Merge branch 'main' into abilities-syntax

CONTRIBUTING.md

@@ -38,7 +38,7 @@ Execute `cargo fmt --all` to fix the formatting.
 If you make changes to [Roc's Standard Library](https://www.roc-lang.org/builtins/Str), you can add comments to the code following [the CommonMark Spec](https://spec.commonmark.org/current/) to further explain your intentions. You can view these changes locally with:
 
 ```sh
-cargo run docs crates/compiler/builtins/roc
+cargo run docs crates/compiler/builtins/roc/main.roc
 ```
 
 This command will generate the documentation in the [`generated-docs`](generated-docs) directory.

crates/cli/src/main.rs

@@ -120,8 +120,7 @@ fn main() -> io::Result<()> {
             let input_path = matches.get_one::<PathBuf>(ROC_FILE).unwrap();
             let target = matches
                 .get_one::<String>(FLAG_TARGET)
-                .map(|s| Target::from_str(s).ok())
+                .and_then(|s| Target::from_str(s).ok())
-                .flatten()
                 .unwrap_or_default();
             roc_linker::generate_stub_lib(
                 input_path,
@@ -132,8 +131,7 @@ fn main() -> io::Result<()> {
         Some((CMD_BUILD, matches)) => {
             let target = matches
                 .get_one::<String>(FLAG_TARGET)
-                .map(|s| Target::from_str(s).ok())
+                .and_then(|s| Target::from_str(s).ok())
-                .flatten()
                 .unwrap_or_default();
             let link_type = match (matches.get_flag(FLAG_LIB), matches.get_flag(FLAG_NO_LINK)) {
                 (true, false) => LinkType::Dylib,

crates/cli/tests/cli_run.rs

@@ -725,7 +725,7 @@ mod cli_run {
                 Arg::PlainText("81"),
             ],
             &[],
-            "4\n",
+            "4.000000000000001\n",
             UseValgrind::No,
             TestCliCommands::Run,
         )

crates/compiler/DESIGN.md

@@ -0,0 +1,194 @@
+# Compiler Design
+
+The current Roc compiler is designed as a pipelining compiler parallelizable
+across Roc modules.
+
+Roc's compilation pipeline consists of a few major components, which form the
+table of contents for this document.
+
+<!-- START doctoc generated TOC please keep comment here to allow auto update -->
+<!-- DON'T EDIT THIS SECTION, INSTEAD RE-RUN doctoc TO UPDATE -->
+
+- [Parsing](#parsing)
+- [Canonicalization](#canonicalization)
+  - [Symbol Resolution](#symbol-resolution)
+  - [Type-alias normalization](#type-alias-normalization)
+  - [Closure naming](#closure-naming)
+- [Constraint Generation](#constraint-generation)
+  - [(Mutually-)recursive definitions](#mutually-recursive-definitions)
+- [Type Solving](#type-solving)
+  - [Unification](#unification)
+  - [Type Inference](#type-inference)
+  - [Recursive Types](#recursive-types)
+  - [Lambda Sets](#lambda-sets)
+  - [Ability Collection](#ability-collection)
+  - [Ability Specialization](#ability-specialization)
+  - [Ability Derivation](#ability-derivation)
+  - [Exhaustiveness Checking](#exhaustiveness-checking)
+  - [Debugging](#debugging)
+- [IR Generation](#ir-generation)
+  - [Memory Layouts](#memory-layouts)
+  - [Compiling Calls](#compiling-calls)
+  - [Decision Trees](#decision-trees)
+  - [Tail-call Optimization](#tail-call-optimization)
+  - [Reference-count insertion](#reference-count-insertion)
+  - [Reusing Memory Allocations](#reusing-memory-allocations)
+  - [Debugging](#debugging-1)
+- [LLVM Code Generator](#llvm-code-generator)
+  - [Morphic Analysis](#morphic-analysis)
+  - [C ABI](#c-abi)
+  - [Test Harness](#test-harness)
+  - [Debugging](#debugging-2)
+- [WASM Code Generator](#wasm-code-generator)
+  - [WASM Interpreter](#wasm-interpreter)
+  - [Debugging](#debugging-3)
+- [Dev Code Generator](#dev-code-generator)
+  - [Debugging](#debugging-4)
+- [Builtins](#builtins)
+- [Compiler Driver](#compiler-driver)
+  - [Caching types](#caching-types)
+- [Repl](#repl)
+- [`test` and `dbg`](#test-and-dbg)
+- [Formatter](#formatter)
+- [Glue](#glue)
+- [Active areas of research / help wanted](#active-areas-of-research--help-wanted)
+
+<!-- END doctoc generated TOC please keep comment here to allow auto update -->
+
+## Parsing
+
+Roc's parsers are designed as [combinators](https://en.wikipedia.org/wiki/Parser_combinator).
+A list of Roc's parse AST and combinators can be found in [the root parse
+file](./parse/src/parser.rs).
+
+Combinators enable parsing to compose as functions would - for example, the
+`one_of` combinator supports attempting multiple parsing strategies, and
+succeeding on the first one; the `and_then` combinator chains two parsers
+together, failing if either parser in the sequence fails.
+
+Since Roc is an indentation-sensitive language, parsing must be cognizant and
+deligent about handling indentation and de-indentation levels. Most parsing
+functions take a `min_indent` parameter that specifies the minimum indentation
+of the scope an expression should be parsed in. Generally, failing to reach
+`min_indent` indicates that an expression has ended (but perhaps too early).
+
+## Canonicalization
+
+After parsing a Roc program into an AST, the AST is transformed into a [canonical
+form](./can/src/expr.rs) AST. This may seem a bit redundant - why build another
+tree, when we already have the AST? Canonicalization performs a few analyses
+to catch user errors, and sets up the state necessary to solve the types in a
+program. Among other things, canonicalization
+
+- Uniquely identifies names (think variable and function names). Along the way,
+    canonicalization builds a graph of all variables' references, and catches
+    unused definitions, undefined definitions, and shadowed definitions.
+- Resolves type signatures, including aliases, into a form suitable for type
+    solving.
+- Determines the order definitions are used in, if they are defined
+    out-of-order.
+- Eliminates syntax sugar (for example, renaming `+` to the function call `add`
+    and converting backpassing to function calls).
+- Collects declared abilities, and ability implementations defined for opaque
+    types. Derived abilities for opaque types are elaborated during
+    canonicalization.
+
+### Symbol Resolution
+
+Identifiers, like variable names, are resolved to [Symbol](./module/src/symbol.rs)s.
+
+Currently, a symbol is a 64-bit value with
+- the bottom 32 bits defining the [ModuleId](./module/src/ident.rs) the symbol
+    is defined in
+- the top 32 bits defining the [IdentId](./module/src/ident.rs) of the symbol
+    in the module
+
+A symbol is unique per identifier name and the scope
+that the identifier has been declared in. Symbols are how the rest of the
+compiler refers to value definitions - since the unique scope and identifier
+name is disambiguated when symbols are created, referencing symbols requires no
+further name resolution.
+
+As symbols are constructed, canonicalization also keeps track of all references
+to a given symbol. This simplifies catching unused definitions, undefined
+definitions, and shadowing, to an index into an array.
+
+### Type-alias normalization
+
+### Closure naming
+
+## Constraint Generation
+
+### (Mutually-)recursive definitions
+
+## Type Solving
+
+### Unification
+
+### Type Inference
+
+### Recursive Types
+
+### Lambda Sets
+
+### Ability Collection
+
+### Ability Specialization
+
+### Ability Derivation
+
+### Exhaustiveness Checking
+
+### Debugging
+
+## IR Generation
+
+### Memory Layouts
+
+### Compiling Calls
+
+### Decision Trees
+
+### Tail-call Optimization
+
+### Reference-count insertion
+
+### Reusing Memory Allocations
+
+### Debugging
+
+## LLVM Code Generator
+
+### Morphic Analysis
+
+### C ABI
+
+### Test Harness
+
+### Debugging
+
+## WASM Code Generator
+
+### WASM Interpreter
+
+### Debugging
+
+## Dev Code Generator
+
+### Debugging
+
+## Builtins
+
+## Compiler Driver
+
+### Caching types
+
+## Repl
+
+## `test` and `dbg`
+
+## Formatter
+
+## Glue
+
+## Active areas of research / help wanted

crates/compiler/README.md

@@ -1,147 +1,8 @@
 # The Roc Compiler
 
-Here's how the compiler is laid out.
+For an overview of the design and architecture of the compiler, see
-
+[DESIGN.md](./DESIGN.md). If you want to dive into the
-## Parsing
+implementation or get some tips on debugging the compiler, see below
-
-The main goal of parsing is to take a plain old String (such as the contents a .roc source file read from the filesystem) and translate that String into an `Expr` value.
-
-`Expr` is an `enum` defined in the `expr` module. An `Expr` represents a Roc expression.
-
-For example, parsing would translate this string...
-
-    "1 + 2"
-
-...into this `Expr` value:
-
-    BinOp(Int(1), Plus, Int(2))
-
-> Technically it would be `Box::new(Int(1))` and `Box::new(Int(2))`, but that's beside the point for now.
-
-This `Expr` representation of the expression is useful for things like:
-
-- Checking that all variables are declared before they're used
-- Type checking
-
-> As of this writing, the compiler doesn't do any of those things yet. They'll be added later!
-
-Since the parser is only concerned with translating String values into Expr values, it will happily translate syntactically valid strings into expressions that won't work at runtime.
-
-For example, parsing will translate this string:
-
-not "foo", "bar"
-
-...into this `Expr`:
-
-    CallByName("not", vec!["foo", "bar"])
-
-Now we may know that `not` takes a `Bool` and returns another `Bool`, but the parser doesn't know that.
-
-The parser only knows how to translate a `String` into an `Expr`; it's the job of other parts of the compiler to figure out if `Expr` values have problems like type mismatches and non-exhaustive patterns.
-
-That said, the parser can still run into syntax errors. This won't parse:
-
-    if then 5 then else then
-
-This is gibberish to the parser, so it will produce an error rather than an `Expr`.
-
-Roc's parser is implemented using the [`marwes/combine`](http://github.com/marwes/combine-language/) crate.
-
-## Evaluating
-
-One of the useful things we can do with an `Expr` is to evaluate it.
-
-The process of evaluation is basically to transform an `Expr` into the simplest `Expr` we can that's still equivalent to the original.
-
-For example, let's say we had this code:
-
-    "1 + 8 - 3"
-
-The parser will translate this into the following `Expr`:
-
-    BinOp(
-        Int(1),
-        Plus,
-        BinOp(Int(8), Minus, Int(3))
-    )
-
-The `eval` function will take this `Expr` and translate it into this much simpler `Expr`:
-
-    Int(6)
-
-At this point it's become so simple that we can display it to the end user as the number `6`. So running `parse` and then `eval` on the original Roc string of `1 + 8 - 3` will result in displaying `6` as the final output.
-
-> The `expr` module includes an `impl fmt::Display for Expr` that takes care of translating `Int(6)` into `6`, `Char('x')` as `'x'`, and so on.
-
-`eval` accomplishes this by doing a `match` on an `Expr` and resolving every operation it encounters. For example, when it first sees this:
-
-    BinOp(
-        Int(1),
-        Plus,
-        BinOp(Int(8), Minus, Int(3))
-    )
-
-The first thing it does is to call `eval` on the right `Expr` values on either side of the `Plus`. That results in:
-
-1. Calling `eval` on `Int(1)`, which returns `Int(1)` since it can't be reduced any further.
-2. Calling `eval` on `BinOp(Int(8), Minus, Int(3))`, which in fact can be reduced further.
-
-Since the second call to `eval` will match on another `BinOp`, it's once again going to recursively call `eval` on both of its `Expr` values. Since those are both `Int` values, though, their `eval` calls will return them right away without doing anything else.
-
-Now that it's evaluated the expressions on either side of the `Minus`, `eval` will look at the particular operator being applied to those expressions (in this case, a minus operator) and check to see if the expressions it was given work with that operation.
-
-> Remember, this `Expr` value potentially came directly from the parser. `eval` can't be sure any type checking has been done on it!
-
-If `eval` detects a non-numeric `Expr` value (that is, the `Expr` is not `Int` or `Frac`) on either side of the `Minus`, then it will immediately give an error and halt the evaluation. This sort of runtime type error is common to dynamic languages, and you can think of `eval` as being a dynamic evaluation of Roc code that hasn't necessarily been type-checked.
-
-Assuming there's no type problem, `eval` can go ahead and run the Rust code of `8 - 3` and store the result in an `Int` expr.
-
-That concludes our original recursive call to `eval`, after which point we'll be evaluating this expression:
-
-    BinOp(
-        Int(1),
-        Plus,
-        Int(5)
-    )
-
-This will work the same way as `Minus` did, and will reduce down to `Int(6)`.
-
-## Optimization philosophy
-
-Focus on optimizations which are only safe in the absence of side effects, and leave the rest to LLVM.
-
-This focus may lead to some optimizations becoming transitively in scope. For example, some deforestation
-examples in the MSR paper benefit from multiple rounds of interleaved deforestation, beta-reduction, and inlining.
-To get those benefits, we'd have to do some inlining and beta-reduction that we could otherwise leave to LLVM's
-inlining and constant propagation/folding.
-
-Even if we're doing those things, it may still make sense to have LLVM do a pass for them as well, since
-early LLVM optimization passes may unlock later opportunities for inlining and constant propagation/folding.
-
-## Inlining
-
-If a function is called exactly once (it's a helper function), presumably we always want to inline those.
-If a function is "small enough" it's probably worth inlining too.
-
-## Fusion
-
-<https://www.microsoft.com/en-us/research/wp-content/uploads/2016/07/deforestation-short-cut.pdf>
-
-Basic approach:
-
-Do list stuff using `build` passing Cons Nil (like a cons list) and then do foldr/build substitution/reduction.
-Afterwards, we can do a separate pass to flatten nested Cons structures into properly initialized RRBTs.
-This way we get both deforestation and efficient RRBT construction. Should work for the other collection types too.
-
-It looks like we need to do some amount of inlining and beta reductions on the Roc side, rather than
-leaving all of those to LLVM.
-
-Advanced approach:
-
-Express operations like map and filter in terms of toStream and fromStream, to unlock more deforestation.
-More info on here:
-
-<https://wiki.haskell.org/GHC_optimisations#Fusion>
 
 ## Getting started with the code
 

crates/compiler/builtins/bitcode/build.zig

@@ -17,7 +17,7 @@ pub fn build(b: *Builder) void {
     // Tests
     var main_tests = b.addTest(main_path);
     main_tests.setBuildMode(mode);
-    main_tests.linkSystemLibrary("c");
+    main_tests.linkLibC();
     const test_step = b.step("test", "Run tests");
     test_step.dependOn(&main_tests.step);
 

crates/compiler/builtins/bitcode/src/compiler_rt.zig

@@ -0,0 +1,442 @@
+const std = @import("std");
+const builtin = @import("builtin");
+const math = std.math;
+
+// Eventually, we need to statically ingest compiler-rt and get it working with the surgical linker, then these should not be needed anymore.
+// Until then, we are manually ingesting used parts of compiler-rt here.
+//
+// Taken from
+// https://github.com/ziglang/zig/tree/4976b58ab16069f8d3267b69ed030f29685c1abe/lib/compiler_rt/
+// Thank you Zig Contributors!
+
+// Libcalls that involve u128 on Windows x86-64 are expected by LLVM to use the
+// calling convention of @Vector(2, u64), rather than what's standard.
+pub const want_windows_v2u64_abi = builtin.os.tag == .windows and builtin.cpu.arch == .x86_64 and @import("builtin").object_format != .c;
+
+const v2u64 = @Vector(2, u64);
+
+// Export it as weak incase it is already linked in by something else.
+comptime {
+    @export(__muloti4, .{ .name = "__muloti4", .linkage = .Weak });
+    if (want_windows_v2u64_abi) {
+        @export(__divti3_windows_x86_64, .{ .name = "__divti3", .linkage = .Weak });
+        @export(__modti3_windows_x86_64, .{ .name = "__modti3", .linkage = .Weak });
+        @export(__umodti3_windows_x86_64, .{ .name = "__umodti3", .linkage = .Weak });
+        @export(__udivti3_windows_x86_64, .{ .name = "__udivti3", .linkage = .Weak });
+        @export(__fixdfti_windows_x86_64, .{ .name = "__fixdfti", .linkage = .Weak });
+        @export(__fixsfti_windows_x86_64, .{ .name = "__fixsfti", .linkage = .Weak });
+        @export(__fixunsdfti_windows_x86_64, .{ .name = "__fixunsdfti", .linkage = .Weak });
+        @export(__fixunssfti_windows_x86_64, .{ .name = "__fixunssfti", .linkage = .Weak });
+    } else {
+        @export(__divti3, .{ .name = "__divti3", .linkage = .Weak });
+        @export(__modti3, .{ .name = "__modti3", .linkage = .Weak });
+        @export(__umodti3, .{ .name = "__umodti3", .linkage = .Weak });
+        @export(__udivti3, .{ .name = "__udivti3", .linkage = .Weak });
+        @export(__fixdfti, .{ .name = "__fixdfti", .linkage = .Weak });
+        @export(__fixsfti, .{ .name = "__fixsfti", .linkage = .Weak });
+        @export(__fixunsdfti, .{ .name = "__fixunsdfti", .linkage = .Weak });
+        @export(__fixunssfti, .{ .name = "__fixunssfti", .linkage = .Weak });
+    }
+}
+
+pub fn __muloti4(a: i128, b: i128, overflow: *c_int) callconv(.C) i128 {
+    if (2 * @bitSizeOf(i128) <= @bitSizeOf(usize)) {
+        return muloXi4_genericFast(i128, a, b, overflow);
+    } else {
+        return muloXi4_genericSmall(i128, a, b, overflow);
+    }
+}
+
+pub fn __divti3(a: i128, b: i128) callconv(.C) i128 {
+    return div(a, b);
+}
+
+fn __divti3_windows_x86_64(a: v2u64, b: v2u64) callconv(.C) v2u64 {
+    return @bitCast(v2u64, div(@bitCast(i128, a), @bitCast(i128, b)));
+}
+
+inline fn div(a: i128, b: i128) i128 {
+    const s_a = a >> (128 - 1);
+    const s_b = b >> (128 - 1);
+
+    const an = (a ^ s_a) -% s_a;
+    const bn = (b ^ s_b) -% s_b;
+
+    const r = udivmod(u128, @bitCast(u128, an), @bitCast(u128, bn), null);
+    const s = s_a ^ s_b;
+    return (@bitCast(i128, r) ^ s) -% s;
+}
+
+pub fn __udivti3(a: u128, b: u128) callconv(.C) u128 {
+    return udivmod(u128, a, b, null);
+}
+
+fn __udivti3_windows_x86_64(a: v2u64, b: v2u64) callconv(.C) v2u64 {
+    return @bitCast(v2u64, udivmod(u128, @bitCast(u128, a), @bitCast(u128, b), null));
+}
+
+pub fn __umodti3(a: u128, b: u128) callconv(.C) u128 {
+    var r: u128 = undefined;
+    _ = udivmod(u128, a, b, &r);
+    return r;
+}
+
+fn __umodti3_windows_x86_64(a: v2u64, b: v2u64) callconv(.C) v2u64 {
+    var r: u128 = undefined;
+    _ = udivmod(u128, @bitCast(u128, a), @bitCast(u128, b), &r);
+    return @bitCast(v2u64, r);
+}
+
+pub fn __modti3(a: i128, b: i128) callconv(.C) i128 {
+    return mod(a, b);
+}
+
+fn __modti3_windows_x86_64(a: v2u64, b: v2u64) callconv(.C) v2u64 {
+    return @bitCast(v2u64, mod(@bitCast(i128, a), @bitCast(i128, b)));
+}
+
+inline fn mod(a: i128, b: i128) i128 {
+    const s_a = a >> (128 - 1); // s = a < 0 ? -1 : 0
+    const s_b = b >> (128 - 1); // s = b < 0 ? -1 : 0
+
+    const an = (a ^ s_a) -% s_a; // negate if s == -1
+    const bn = (b ^ s_b) -% s_b; // negate if s == -1
+
+    var r: u128 = undefined;
+    _ = udivmod(u128, @bitCast(u128, an), @bitCast(u128, bn), &r);
+    return (@bitCast(i128, r) ^ s_a) -% s_a; // negate if s == -1
+}
+
+pub fn __fixdfti(a: f64) callconv(.C) i128 {
+    return floatToInt(i128, a);
+}
+
+fn __fixdfti_windows_x86_64(a: f64) callconv(.C) v2u64 {
+    return @bitCast(v2u64, floatToInt(i128, a));
+}
+
+pub fn __fixsfti(a: f32) callconv(.C) i128 {
+    return floatToInt(i128, a);
+}
+
+fn __fixsfti_windows_x86_64(a: f32) callconv(.C) v2u64 {
+    return @bitCast(v2u64, floatToInt(i128, a));
+}
+
+pub fn __fixunsdfti(a: f64) callconv(.C) u128 {
+    return floatToInt(u128, a);
+}
+
+fn __fixunsdfti_windows_x86_64(a: f64) callconv(.C) v2u64 {
+    return @bitCast(v2u64, floatToInt(u128, a));
+}
+
+pub fn __fixunssfti(a: f32) callconv(.C) u128 {
+    return floatToInt(u128, a);
+}
+
+fn __fixunssfti_windows_x86_64(a: f32) callconv(.C) v2u64 {
+    return @bitCast(v2u64, floatToInt(u128, a));
+}
+// mulo - multiplication overflow
+// * return a*%b.
+// * return if a*b overflows => 1 else => 0
+// - muloXi4_genericSmall as default
+// - muloXi4_genericFast for 2*bitsize <= usize
+
+inline fn muloXi4_genericSmall(comptime ST: type, a: ST, b: ST, overflow: *c_int) ST {
+    overflow.* = 0;
+    const min = math.minInt(ST);
+    var res: ST = a *% b;
+    // Hacker's Delight section Overflow subsection Multiplication
+    // case a=-2^{31}, b=-1 problem, because
+    // on some machines a*b = -2^{31} with overflow
+    // Then -2^{31}/-1 overflows and any result is possible.
+    // => check with a<0 and b=-2^{31}
+    if ((a < 0 and b == min) or (a != 0 and @divTrunc(res, a) != b))
+        overflow.* = 1;
+    return res;
+}
+
+inline fn muloXi4_genericFast(comptime ST: type, a: ST, b: ST, overflow: *c_int) ST {
+    overflow.* = 0;
+    const EST = switch (ST) {
+        i32 => i64,
+        i64 => i128,
+        i128 => i256,
+        else => unreachable,
+    };
+    const min = math.minInt(ST);
+    const max = math.maxInt(ST);
+    var res: EST = @as(EST, a) * @as(EST, b);
+    //invariant: -2^{bitwidth(EST)} < res < 2^{bitwidth(EST)-1}
+    if (res < min or max < res)
+        overflow.* = 1;
+    return @truncate(ST, res);
+}
+
+const native_endian = builtin.cpu.arch.endian();
+const low = switch (native_endian) {
+    .Big => 1,
+    .Little => 0,
+};
+const high = 1 - low;
+
+pub fn udivmod(comptime DoubleInt: type, a: DoubleInt, b: DoubleInt, maybe_rem: ?*DoubleInt) DoubleInt {
+    // @setRuntimeSafety(builtin.is_test);
+
+    const double_int_bits = @typeInfo(DoubleInt).Int.bits;
+    const single_int_bits = @divExact(double_int_bits, 2);
+    const SingleInt = std.meta.Int(.unsigned, single_int_bits);
+    const SignedDoubleInt = std.meta.Int(.signed, double_int_bits);
+    const Log2SingleInt = std.math.Log2Int(SingleInt);
+
+    const n = @bitCast([2]SingleInt, a);
+    const d = @bitCast([2]SingleInt, b);
+    var q: [2]SingleInt = undefined;
+    var r: [2]SingleInt = undefined;
+    var sr: c_uint = undefined;
+    // special cases, X is unknown, K != 0
+    if (n[high] == 0) {
+        if (d[high] == 0) {
+            // 0 X
+            // ---
+            // 0 X
+            if (maybe_rem) |rem| {
+                rem.* = n[low] % d[low];
+            }
+            return n[low] / d[low];
+        }
+        // 0 X
+        // ---
+        // K X
+        if (maybe_rem) |rem| {
+            rem.* = n[low];
+        }
+        return 0;
+    }
+    // n[high] != 0
+    if (d[low] == 0) {
+        if (d[high] == 0) {
+            // K X
+            // ---
+            // 0 0
+            if (maybe_rem) |rem| {
+                rem.* = n[high] % d[low];
+            }
+            return n[high] / d[low];
+        }
+        // d[high] != 0
+        if (n[low] == 0) {
+            // K 0
+            // ---
+            // K 0
+            if (maybe_rem) |rem| {
+                r[high] = n[high] % d[high];
+                r[low] = 0;
+                rem.* = @bitCast(DoubleInt, r);
+            }
+            return n[high] / d[high];
+        }
+        // K K
+        // ---
+        // K 0
+        if ((d[high] & (d[high] - 1)) == 0) {
+            // d is a power of 2
+            if (maybe_rem) |rem| {
+                r[low] = n[low];
+                r[high] = n[high] & (d[high] - 1);
+                rem.* = @bitCast(DoubleInt, r);
+            }
+            return n[high] >> @intCast(Log2SingleInt, @ctz(SingleInt, d[high]));
+        }
+        // K K
+        // ---
+        // K 0
+        sr = @bitCast(c_uint, @as(c_int, @clz(SingleInt, d[high])) - @as(c_int, @clz(SingleInt, n[high])));
+        // 0 <= sr <= single_int_bits - 2 or sr large
+        if (sr > single_int_bits - 2) {
+            if (maybe_rem) |rem| {
+                rem.* = a;
+            }
+            return 0;
+        }
+        sr += 1;
+        // 1 <= sr <= single_int_bits - 1
+        // q.all = a << (double_int_bits - sr);
+        q[low] = 0;
+        q[high] = n[low] << @intCast(Log2SingleInt, single_int_bits - sr);
+        // r.all = a >> sr;
+        r[high] = n[high] >> @intCast(Log2SingleInt, sr);
+        r[low] = (n[high] << @intCast(Log2SingleInt, single_int_bits - sr)) | (n[low] >> @intCast(Log2SingleInt, sr));
+    } else {
+        // d[low] != 0
+        if (d[high] == 0) {
+            // K X
+            // ---
+            // 0 K
+            if ((d[low] & (d[low] - 1)) == 0) {
+                // d is a power of 2
+                if (maybe_rem) |rem| {
+                    rem.* = n[low] & (d[low] - 1);
+                }
+                if (d[low] == 1) {
+                    return a;
+                }
+                sr = @ctz(SingleInt, d[low]);
+                q[high] = n[high] >> @intCast(Log2SingleInt, sr);
+                q[low] = (n[high] << @intCast(Log2SingleInt, single_int_bits - sr)) | (n[low] >> @intCast(Log2SingleInt, sr));
+                return @bitCast(DoubleInt, q);
+            }
+            // K X
+            // ---
+            // 0 K
+            sr = 1 + single_int_bits + @as(c_uint, @clz(SingleInt, d[low])) - @as(c_uint, @clz(SingleInt, n[high]));
+            // 2 <= sr <= double_int_bits - 1
+            // q.all = a << (double_int_bits - sr);
+            // r.all = a >> sr;
+            if (sr == single_int_bits) {
+                q[low] = 0;
+                q[high] = n[low];
+                r[high] = 0;
+                r[low] = n[high];
+            } else if (sr < single_int_bits) {
+                // 2 <= sr <= single_int_bits - 1
+                q[low] = 0;
+                q[high] = n[low] << @intCast(Log2SingleInt, single_int_bits - sr);
+                r[high] = n[high] >> @intCast(Log2SingleInt, sr);
+                r[low] = (n[high] << @intCast(Log2SingleInt, single_int_bits - sr)) | (n[low] >> @intCast(Log2SingleInt, sr));
+            } else {
+                // single_int_bits + 1 <= sr <= double_int_bits - 1
+                q[low] = n[low] << @intCast(Log2SingleInt, double_int_bits - sr);
+                q[high] = (n[high] << @intCast(Log2SingleInt, double_int_bits - sr)) | (n[low] >> @intCast(Log2SingleInt, sr - single_int_bits));
+                r[high] = 0;
+                r[low] = n[high] >> @intCast(Log2SingleInt, sr - single_int_bits);
+            }
+        } else {
+            // K X
+            // ---
+            // K K
+            sr = @bitCast(c_uint, @as(c_int, @clz(SingleInt, d[high])) - @as(c_int, @clz(SingleInt, n[high])));
+            // 0 <= sr <= single_int_bits - 1 or sr large
+            if (sr > single_int_bits - 1) {
+                if (maybe_rem) |rem| {
+                    rem.* = a;
+                }
+                return 0;
+            }
+            sr += 1;
+            // 1 <= sr <= single_int_bits
+            // q.all = a << (double_int_bits - sr);
+            // r.all = a >> sr;
+            q[low] = 0;
+            if (sr == single_int_bits) {
+                q[high] = n[low];
+                r[high] = 0;
+                r[low] = n[high];
+            } else {
+                r[high] = n[high] >> @intCast(Log2SingleInt, sr);
+                r[low] = (n[high] << @intCast(Log2SingleInt, single_int_bits - sr)) | (n[low] >> @intCast(Log2SingleInt, sr));
+                q[high] = n[low] << @intCast(Log2SingleInt, single_int_bits - sr);
+            }
+        }
+    }
+    // Not a special case
+    // q and r are initialized with:
+    // q.all = a << (double_int_bits - sr);
+    // r.all = a >> sr;
+    // 1 <= sr <= double_int_bits - 1
+    var carry: u32 = 0;
+    var r_all: DoubleInt = undefined;
+    while (sr > 0) : (sr -= 1) {
+        // r:q = ((r:q)  << 1) | carry
+        r[high] = (r[high] << 1) | (r[low] >> (single_int_bits - 1));
+        r[low] = (r[low] << 1) | (q[high] >> (single_int_bits - 1));
+        q[high] = (q[high] << 1) | (q[low] >> (single_int_bits - 1));
+        q[low] = (q[low] << 1) | carry;
+        // carry = 0;
+        // if (r.all >= b)
+        // {
+        //     r.all -= b;
+        //      carry = 1;
+        // }
+        r_all = @bitCast(DoubleInt, r);
+        const s: SignedDoubleInt = @bitCast(SignedDoubleInt, b -% r_all -% 1) >> (double_int_bits - 1);
+        carry = @intCast(u32, s & 1);
+        r_all -= b & @bitCast(DoubleInt, s);
+        r = @bitCast([2]SingleInt, r_all);
+    }
+    const q_all = (@bitCast(DoubleInt, q) << 1) | carry;
+    if (maybe_rem) |rem| {
+        rem.* = r_all;
+    }
+    return q_all;
+}
+
+pub inline fn floatToInt(comptime I: type, a: anytype) I {
+    const Log2Int = math.Log2Int;
+    const Int = @import("std").meta.Int;
+    const F = @TypeOf(a);
+    const float_bits = @typeInfo(F).Float.bits;
+    const int_bits = @typeInfo(I).Int.bits;
+    const rep_t = Int(.unsigned, float_bits);
+    const sig_bits = math.floatMantissaBits(F);
+    const exp_bits = math.floatExponentBits(F);
+    const fractional_bits = floatFractionalBits(F);
+
+    // const implicit_bit = if (F != f80) (@as(rep_t, 1) << sig_bits) else 0;
+    const implicit_bit = @as(rep_t, 1) << sig_bits;
+    const max_exp = (1 << (exp_bits - 1));
+    const exp_bias = max_exp - 1;
+    const sig_mask = (@as(rep_t, 1) << sig_bits) - 1;
+
+    // Break a into sign, exponent, significand
+    const a_rep: rep_t = @bitCast(rep_t, a);
+    const negative = (a_rep >> (float_bits - 1)) != 0;
+    const exponent = @intCast(i32, (a_rep << 1) >> (sig_bits + 1)) - exp_bias;
+    const significand: rep_t = (a_rep & sig_mask) | implicit_bit;
+
+    // If the exponent is negative, the result rounds to zero.
+    if (exponent < 0) return 0;
+
+    // If the value is too large for the integer type, saturate.
+    switch (@typeInfo(I).Int.signedness) {
+        .unsigned => {
+            if (negative) return 0;
+            if (@intCast(c_uint, exponent) >= @minimum(int_bits, max_exp)) return math.maxInt(I);
+        },
+        .signed => if (@intCast(c_uint, exponent) >= @minimum(int_bits - 1, max_exp)) {
+            return if (negative) math.minInt(I) else math.maxInt(I);
+        },
+    }
+
+    // If 0 <= exponent < sig_bits, right shift to get the result.
+    // Otherwise, shift left.
+    var result: I = undefined;
+    if (exponent < fractional_bits) {
+        result = @intCast(I, significand >> @intCast(Log2Int(rep_t), fractional_bits - exponent));
+    } else {
+        result = @intCast(I, significand) << @intCast(Log2Int(I), exponent - fractional_bits);
+    }
+
+    if ((@typeInfo(I).Int.signedness == .signed) and negative)
+        return ~result +% 1;
+    return result;
+}
+
+/// Returns the number of fractional bits in the mantissa of floating point type T.
+pub inline fn floatFractionalBits(comptime T: type) comptime_int {
+    comptime std.debug.assert(@typeInfo(T) == .Float);
+
+    // standard IEEE floats have an implicit 0.m or 1.m integer part
+    // f80 is special and has an explicitly stored bit in the MSB
+    // this function corresponds to `MANT_DIG - 1' from C
+    return switch (@typeInfo(T).Float.bits) {
+        16 => 10,
+        32 => 23,
+        64 => 52,
+        80 => 63,
+        128 => 112,
+        else => @compileError("unknown floating point type " ++ @typeName(T)),
+    };
+}

crates/compiler/builtins/bitcode/src/dec.zig

@@ -44,6 +44,8 @@ pub const RocDec = extern struct {
         return ret;
     }
 
+    // TODO: If Str.toDec eventually supports more error types, return errors here.
+    // For now, just return null which will give the default error.
     pub fn fromStr(roc_str: RocStr) ?RocDec {
         if (roc_str.isEmpty()) {
             return null;
@@ -79,7 +81,8 @@ pub const RocDec = extern struct {
 
             var after_str_len = (length - 1) - pi;
             if (after_str_len > decimal_places) {
-                @panic("TODO runtime exception for too many decimal places!");
+                // TODO: runtime exception for too many decimal places!
+                return null;
             }
             var diff_decimal_places = decimal_places - after_str_len;
 
@@ -96,7 +99,8 @@ pub const RocDec = extern struct {
             var result: i128 = undefined;
             var overflowed = @mulWithOverflow(i128, before, one_point_zero_i128, &result);
             if (overflowed) {
-                @panic("TODO runtime exception for overflow!");
+                // TODO: runtime exception for overflow!
+                return null;
             }
             before_val_i128 = result;
         }
@@ -107,7 +111,8 @@ pub const RocDec = extern struct {
                     var result: i128 = undefined;
                     var overflowed = @addWithOverflow(i128, before, after, &result);
                     if (overflowed) {
-                        @panic("TODO runtime exception for overflow!");
+                        // TODO: runtime exception for overflow!
+                        return null;
                     }
                     break :blk .{ .num = result };
                 } else {
@@ -184,7 +189,7 @@ pub const RocDec = extern struct {
         position += 1;
 
         const trailing_zeros: u6 = count_trailing_zeros_base10(num);
-        if (trailing_zeros == decimal_places) {
+        if (trailing_zeros >= decimal_places) {
             // add just a single zero if all decimal digits are zero
             str_bytes[position] = '0';
             position += 1;
@@ -851,6 +856,14 @@ test "fromStr: .123.1" {
     try expectEqual(dec, null);
 }
 
+test "toStr: 100.00" {
+    var dec: RocDec = .{ .num = 100000000000000000000 };
+    var res_roc_str = dec.toStr();
+
+    const res_slice: []const u8 = "100.0"[0..];
+    try expectEqualSlices(u8, res_slice, res_roc_str.asSlice());
+}
+
 test "toStr: 123.45" {
     var dec: RocDec = .{ .num = 123450000000000000000 };
     var res_roc_str = dec.toStr();

crates/compiler/builtins/bitcode/src/main.zig

@@ -5,6 +5,10 @@ const utils = @import("utils.zig");
 const expect = @import("expect.zig");
 const panic_utils = @import("panic.zig");
 
+comptime {
+    _ = @import("compiler_rt.zig");
+}
+
 const ROC_BUILTINS = "roc_builtins";
 const NUM = "num";
 const STR = "str";
@@ -81,8 +85,12 @@ comptime {
         num.exportPow(T, ROC_BUILTINS ++ "." ++ NUM ++ ".pow_int.");
         num.exportDivCeil(T, ROC_BUILTINS ++ "." ++ NUM ++ ".div_ceil.");
 
-        num.exportRoundF32(T, ROC_BUILTINS ++ "." ++ NUM ++ ".round_f32.");
+        num.exportRound(f32, T, ROC_BUILTINS ++ "." ++ NUM ++ ".round_f32.");
-        num.exportRoundF64(T, ROC_BUILTINS ++ "." ++ NUM ++ ".round_f64.");
+        num.exportRound(f64, T, ROC_BUILTINS ++ "." ++ NUM ++ ".round_f64.");
+        num.exportFloor(f32, T, ROC_BUILTINS ++ "." ++ NUM ++ ".floor_f32.");
+        num.exportFloor(f64, T, ROC_BUILTINS ++ "." ++ NUM ++ ".floor_f64.");
+        num.exportCeiling(f32, T, ROC_BUILTINS ++ "." ++ NUM ++ ".ceiling_f32.");
+        num.exportCeiling(f64, T, ROC_BUILTINS ++ "." ++ NUM ++ ".ceiling_f64.");
 
         num.exportAddWithOverflow(T, ROC_BUILTINS ++ "." ++ NUM ++ ".add_with_overflow.");
         num.exportAddOrPanic(T, ROC_BUILTINS ++ "." ++ NUM ++ ".add_or_panic.");
@@ -122,6 +130,8 @@ comptime {
 
         num.exportPow(T, ROC_BUILTINS ++ "." ++ NUM ++ ".pow.");
         num.exportLog(T, ROC_BUILTINS ++ "." ++ NUM ++ ".log.");
+        num.exportFAbs(T, ROC_BUILTINS ++ "." ++ NUM ++ ".fabs.");
+        num.exportSqrt(T, ROC_BUILTINS ++ "." ++ NUM ++ ".sqrt.");
 
         num.exportAddWithOverflow(T, ROC_BUILTINS ++ "." ++ NUM ++ ".add_with_overflow.");
         num.exportSubWithOverflow(T, ROC_BUILTINS ++ "." ++ NUM ++ ".sub_with_overflow.");
@@ -274,60 +284,3 @@ test "" {
 
     testing.refAllDecls(@This());
 }
-
-// For unclear reasons, sometimes this function is not linked in on some machines.
-// Therefore we provide it as LLVM bitcode and mark it as externally linked during our LLVM codegen
-//
-// Taken from
-// https://github.com/ziglang/zig/blob/85755c51d529e7d9b406c6bdf69ce0a0f33f3353/lib/std/special/compiler_rt/muloti4.zig
-//
-// Thank you Zig Contributors!
-
-// Export it as weak incase it is already linked in by something else.
-comptime {
-    if (builtin.target.os.tag != .windows) {
-        @export(__muloti4, .{ .name = "__muloti4", .linkage = .Weak });
-    }
-}
-fn __muloti4(a: i128, b: i128, overflow: *c_int) callconv(.C) i128 {
-    // @setRuntimeSafety(std.builtin.is_test);
-
-    const min = @bitCast(i128, @as(u128, 1 << (128 - 1)));
-    const max = ~min;
-    overflow.* = 0;
-
-    const r = a *% b;
-    if (a == min) {
-        if (b != 0 and b != 1) {
-            overflow.* = 1;
-        }
-        return r;
-    }
-    if (b == min) {
-        if (a != 0 and a != 1) {
-            overflow.* = 1;
-        }
-        return r;
-    }
-
-    const sa = a >> (128 - 1);
-    const abs_a = (a ^ sa) -% sa;
-    const sb = b >> (128 - 1);
-    const abs_b = (b ^ sb) -% sb;
-
-    if (abs_a < 2 or abs_b < 2) {
-        return r;
-    }
-
-    if (sa == sb) {
-        if (abs_a > @divTrunc(max, abs_b)) {
-            overflow.* = 1;
-        }
-    } else {
-        if (abs_a > @divTrunc(min, -abs_b)) {
-            overflow.* = 1;
-        }
-    }
-
-    return r;
-}

crates/compiler/builtins/bitcode/src/num.zig

@@ -152,7 +152,7 @@ pub fn exportAtan(comptime T: type, comptime name: []const u8) void {
 pub fn exportSin(comptime T: type, comptime name: []const u8) void {
     comptime var f = struct {
         fn func(input: T) callconv(.C) T {
-            return @sin(input);
+            return math.sin(input);
         }
     }.func;
     @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });
@@ -161,7 +161,7 @@ pub fn exportSin(comptime T: type, comptime name: []const u8) void {
 pub fn exportCos(comptime T: type, comptime name: []const u8) void {
     comptime var f = struct {
         fn func(input: T) callconv(.C) T {
-            return @cos(input);
+            return math.cos(input);
         }
     }.func;
     @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });
@@ -170,25 +170,52 @@ pub fn exportCos(comptime T: type, comptime name: []const u8) void {
 pub fn exportLog(comptime T: type, comptime name: []const u8) void {
     comptime var f = struct {
         fn func(input: T) callconv(.C) T {
-            return @log(input);
+            return math.ln(input);
         }
     }.func;
     @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });
 }
 
-pub fn exportRoundF32(comptime T: type, comptime name: []const u8) void {
+pub fn exportFAbs(comptime T: type, comptime name: []const u8) void {
     comptime var f = struct {
-        fn func(input: f32) callconv(.C) T {
+        fn func(input: T) callconv(.C) T {
-            return @floatToInt(T, (@round(input)));
+            return math.absFloat(input);
         }
     }.func;
     @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });
 }
 
-pub fn exportRoundF64(comptime T: type, comptime name: []const u8) void {
+pub fn exportSqrt(comptime T: type, comptime name: []const u8) void {
     comptime var f = struct {
-        fn func(input: f64) callconv(.C) T {
+        fn func(input: T) callconv(.C) T {
-            return @floatToInt(T, (@round(input)));
+            return math.sqrt(input);
+        }
+    }.func;
+    @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });
+}
+
+pub fn exportRound(comptime F: type, comptime T: type, comptime name: []const u8) void {
+    comptime var f = struct {
+        fn func(input: F) callconv(.C) T {
+            return @floatToInt(T, (math.round(input)));
+        }
+    }.func;
+    @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });
+}
+
+pub fn exportFloor(comptime F: type, comptime T: type, comptime name: []const u8) void {
+    comptime var f = struct {
+        fn func(input: F) callconv(.C) T {
+            return @floatToInt(T, (math.floor(input)));
+        }
+    }.func;
+    @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });
+}
+
+pub fn exportCeiling(comptime F: type, comptime T: type, comptime name: []const u8) void {
+    comptime var f = struct {
+        fn func(input: F) callconv(.C) T {
+            return @floatToInt(T, (math.ceil(input)));
         }
     }.func;
     @export(f, .{ .name = name ++ @typeName(T), .linkage = .Strong });

crates/compiler/builtins/bitcode/src/utils.zig

@@ -305,6 +305,10 @@ pub fn isUnique(
 
     const isizes: [*]isize = @intToPtr([*]isize, masked_ptr);
 
+    if (DEBUG_INCDEC and builtin.target.cpu.arch != .wasm32) {
+        std.debug.print("| is unique {*}\n", .{&bytes[0]});
+    }
+
     const refcount = (isizes - 1)[0];
 
     return refcount == REFCOUNT_ONE_ISIZE;

crates/compiler/builtins/roc/Dict.roc

@@ -95,7 +95,7 @@ Dict k v := {
     # TODO: define Eq and Hash that are unordered. Only if value implements hash/eq?
     metadata : List I8,
     dataIndices : List Nat,
-    data : List (T k v),
+    data : List (k, v),
     size : Nat,
 } | k implements Hash & Eq
      implements [
@@ -175,12 +175,12 @@ single = \k, v ->
 ##     |> Dict.insert 2 "Two"
 ##     |> Dict.insert 3 "Three"
 ##     |> Dict.insert 4 "Four"
-##     |> Bool.isEq (Dict.fromList [T 1 "One", T 2 "Two", T 3 "Three", T 4 "Four"])
+##     |> Bool.isEq (Dict.fromList [(1, "One"), (2, "Two"), (3, "Three"), (4, "Four")])
 ## ```
-fromList : List (T k v) -> Dict k v | k implements Hash & Eq
+fromList : List (k, v) -> Dict k v | k Hash & Eq
 fromList = \data ->
     # TODO: make this efficient. Should just set data and then set all indicies in the hashmap.
-    List.walk data (empty {}) (\dict, T k v -> insert dict k v)
+    List.walk data (empty {}) (\dict, (k, v) -> insert dict k v)
 
 ## Returns the number of values in the dictionary.
 ## ```
@@ -238,7 +238,7 @@ clear = \@Dict { metadata, dataIndices, data } ->
 ## ```
 walk : Dict k v, state, (state, k, v -> state) -> state | k implements Hash & Eq
 walk = \@Dict { data }, initialState, transform ->
-    List.walk data initialState (\state, T k v -> transform state k v)
+    List.walk data initialState (\state, (k, v) -> transform state k v)
 
 ## Same as [Dict.walk], except you can stop walking early.
 ##
@@ -270,7 +270,7 @@ walk = \@Dict { data }, initialState, transform ->
 ## ```
 walkUntil : Dict k v, state, (state, k, v -> [Continue state, Break state]) -> state | k implements Hash & Eq
 walkUntil = \@Dict { data }, initialState, transform ->
-    List.walkUntil data initialState (\state, T k v -> transform state k v)
+    List.walkUntil data initialState (\state, (k, v) -> transform state k v)
 
 ## Get the value for a given key. If there is a value for the specified key it
 ## will return [Ok value], otherwise return [Err KeyNotFound].
@@ -296,7 +296,7 @@ get = \@Dict { metadata, dataIndices, data }, key ->
     when findIndexHelper metadata dataIndices data h2Key key probe 0 is
         Ok index ->
             dataIndex = listGetUnsafe dataIndices index
-            (T _ v) = listGetUnsafe data dataIndex
+            (_, v) = listGetUnsafe data dataIndex
 
             Ok v
 
@@ -353,7 +353,7 @@ insert = \@Dict { metadata, dataIndices, data, size }, key, value ->
             @Dict {
                 metadata,
                 dataIndices,
-                data: List.set data dataIndex (T key value),
+                data: List.set data dataIndex (key, value),
                 size,
             }
 
@@ -447,9 +447,9 @@ update = \dict, key, alter ->
 ##     |> Dict.insert 3 "Three"
 ##     |> Dict.insert 4 "Four"
 ##     |> Dict.toList
-##     |> Bool.isEq [T 1 "One", T 2 "Two", T 3 "Three", T 4 "Four"]
+##     |> Bool.isEq [(1, "One"), (2, "Two"), (3, "Three"), (4, "Four")]
 ## ```
-toList : Dict k v -> List (T k v) | k implements Hash & Eq
+toList : Dict k v -> List (k, v) | k implements Hash & Eq
 toList = \@Dict { data } ->
     data
 
@@ -466,7 +466,7 @@ toList = \@Dict { data } ->
 ## ```
 keys : Dict k v -> List k | k implements Hash & Eq
 keys = \@Dict { data } ->
-    List.map data (\T k _ -> k)
+    List.map data (\(k, _) -> k)
 
 ## Returns the values of a dictionary as a [List].
 ## This requires allocating a temporary [List], prefer using [Dict.toList] or [Dict.walk] instead.
@@ -481,7 +481,7 @@ keys = \@Dict { data } ->
 ## ```
 values : Dict k v -> List v | k implements Hash & Eq
 values = \@Dict { data } ->
-    List.map data (\T _ v -> v)
+    List.map data (\(_, v) -> v)
 
 ## Combine two dictionaries by keeping the [union](https://en.wikipedia.org/wiki/Union_(set_theory))
 ## of all the key-value pairs. This means that all the key-value pairs in
@@ -567,7 +567,7 @@ removeAll = \xs, ys ->
 
 swapAndUpdateDataIndex : Dict k v, Nat, Nat -> Dict k v | k implements Hash & Eq
 swapAndUpdateDataIndex = \@Dict { metadata, dataIndices, data, size }, removedIndex, lastIndex ->
-    (T key _) = listGetUnsafe data lastIndex
+    (key, _) = listGetUnsafe data lastIndex
     hashKey =
         createLowLevelHasher PseudoRandSeed
         |> Hash.hash key
@@ -603,7 +603,7 @@ insertNotFoundHelper = \@Dict { metadata, dataIndices, data, size }, key, value,
     probe = newProbe h1Key (div8 (List.len metadata))
     index = nextEmptyOrDeletedHelper metadata probe 0
     dataIndex = List.len data
-    nextData = List.append data (T key value)
+    nextData = List.append data (key, value)
 
     @Dict {
         metadata: List.set metadata index h2Key,
@@ -629,7 +629,7 @@ nextEmptyOrDeletedHelper = \metadata, probe, offset ->
 
 # TODO: investigate if this needs to be split into more specific helper functions.
 # There is a chance that returning specific sub-info like the value would be faster.
-findIndexHelper : List I8, List Nat, List (T k v), I8, k, Probe, Nat -> Result Nat [NotFound] | k implements Hash & Eq
+findIndexHelper : List I8, List Nat, List (k, v), I8, k, Probe, Nat -> Result Nat [NotFound] | k implements Hash & Eq
 findIndexHelper = \metadata, dataIndices, data, h2Key, key, probe, offset ->
     # For finding a value, we must search past all deleted element tombstones.
     index = Num.addWrap (mul8 probe.slotIndex) offset
@@ -642,7 +642,7 @@ findIndexHelper = \metadata, dataIndices, data, h2Key, key, probe, offset ->
     else if md == h2Key then
         # Potentially matching slot, check if the key is a match.
         dataIndex = listGetUnsafe dataIndices index
-        (T k _) = listGetUnsafe data dataIndex
+        (k, _) = listGetUnsafe data dataIndex
 
         if k == key then
             # We have a match, return its index.
@@ -687,7 +687,7 @@ rehash = \@Dict { metadata, dataIndices, data, size } ->
 
     rehashHelper newDict metadata dataIndices data 0
 
-rehashHelper : Dict k v, List I8, List Nat, List (T k v), Nat -> Dict k v | k implements Hash & Eq
+rehashHelper : Dict k v, List I8, List Nat, List (k, v), Nat -> Dict k v | k implements Hash & implements 
 rehashHelper = \dict, oldMetadata, oldDataIndices, oldData, index ->
     when List.get oldMetadata index is
         Ok md ->
@@ -695,7 +695,7 @@ rehashHelper = \dict, oldMetadata, oldDataIndices, oldData, index ->
                 if md >= 0 then
                     # We have an actual element here
                     dataIndex = listGetUnsafe oldDataIndices index
-                    (T k _) = listGetUnsafe oldData dataIndex
+                    (k, _) = listGetUnsafe oldData dataIndex
 
                     insertForRehash dict k dataIndex
                 else
@@ -731,8 +731,6 @@ emptySlot = -128
 deletedSlot : I8
 deletedSlot = -2
 
-T k v : [T k v]
-
 # Capacity must be a power of 2.
 # We still will use slots of 8 even though this version has no true slots.
 # We just move an element at a time.
@@ -869,7 +867,7 @@ expect
 
 expect
     dict =
-        fromList [T 1u8 1u8, T 2 2, T 3 3]
+        fromList [(1u8, 1u8), (2, 2), (3, 3)]
         |> remove 1
         |> remove 3
 
@@ -877,7 +875,7 @@ expect
 
 expect
     list =
-        fromList [T 1u8 1u8, T 2u8 2u8, T 3 3]
+        fromList [(1u8, 1u8), (2u8, 2u8), (3, 3)]
         |> remove 1
         |> insert 0 0
         |> remove 3

crates/compiler/builtins/roc/Num.roc

@@ -989,19 +989,11 @@ pow : Frac a, Frac a -> Frac a
 ## This process is known as [exponentiation by squaring](https://en.wikipedia.org/wiki/Exponentiation_by_squaring).
 ##
 ## For a [Frac] alternative to this function, which supports negative exponents,
-## see #Num.exp.
+## see #Num.pow.
-## ```
-## Num.exp 5 0
 ##
-## Num.exp 5 1
+## ## Warning
 ##
-## Num.exp 5 2
+## It is very easy for this function to produce an answer
-##
-## Num.exp 5 6
-## ```
-## ## Performance Details
-##
-## Be careful! It is very easy for this function to produce an answer
 ## so large it causes an overflow.
 powInt : Int a, Int a -> Int a
 

crates/compiler/builtins/src/bitcode.rs

@@ -267,9 +267,15 @@ pub const NUM_IS_INFINITE: IntrinsicName = float_intrinsic!("roc_builtins.num.is
 pub const NUM_IS_FINITE: IntrinsicName = float_intrinsic!("roc_builtins.num.is_finite");
 pub const NUM_LOG: IntrinsicName = float_intrinsic!("roc_builtins.num.log");
 pub const NUM_POW: IntrinsicName = float_intrinsic!("roc_builtins.num.pow");
+pub const NUM_FABS: IntrinsicName = float_intrinsic!("roc_builtins.num.fabs");
+pub const NUM_SQRT: IntrinsicName = float_intrinsic!("roc_builtins.num.sqrt");
 
 pub const NUM_POW_INT: IntrinsicName = int_intrinsic!("roc_builtins.num.pow_int");
 pub const NUM_DIV_CEIL: IntrinsicName = int_intrinsic!("roc_builtins.num.div_ceil");
+pub const NUM_CEILING_F32: IntrinsicName = int_intrinsic!("roc_builtins.num.ceiling_f32");
+pub const NUM_CEILING_F64: IntrinsicName = int_intrinsic!("roc_builtins.num.ceiling_f64");
+pub const NUM_FLOOR_F32: IntrinsicName = int_intrinsic!("roc_builtins.num.floor_f32");
+pub const NUM_FLOOR_F64: IntrinsicName = int_intrinsic!("roc_builtins.num.floor_f64");
 pub const NUM_ROUND_F32: IntrinsicName = int_intrinsic!("roc_builtins.num.round_f32");
 pub const NUM_ROUND_F64: IntrinsicName = int_intrinsic!("roc_builtins.num.round_f64");
 

crates/compiler/gen_dev/src/generic64/aarch64.rs

@@ -458,6 +458,11 @@ impl CallConv<AArch64GeneralReg, AArch64FloatReg, AArch64Assembler> for AArch64C
 }
 
 impl Assembler<AArch64GeneralReg, AArch64FloatReg> for AArch64Assembler {
+    #[inline(always)]
+    fn base_pointer() -> AArch64GeneralReg {
+        AArch64GeneralReg::FP
+    }
+
     #[inline(always)]
     fn abs_reg64_reg64(buf: &mut Vec<'_, u8>, dst: AArch64GeneralReg, src: AArch64GeneralReg) {
         cmp_reg64_imm12(buf, src, 0);
@@ -1065,7 +1070,7 @@ impl Assembler<AArch64GeneralReg, AArch64FloatReg> for AArch64Assembler {
     }
 
     #[inline(always)]
-    fn neq_reg64_reg64_reg64(
+    fn neq_reg_reg_reg(
         buf: &mut Vec<'_, u8>,
         _register_width: RegisterWidth,
         dst: AArch64GeneralReg,

crates/compiler/gen_dev/src/generic64/mod.rs

@@ -1,6 +1,6 @@
 use crate::{
-    single_register_floats, single_register_int_builtins, single_register_integers, Backend, Env,
+    pointer_layouts, single_register_floats, single_register_int_builtins,
-    Relocation,
+    single_register_integers, Backend, Env, Relocation,
 };
 use bumpalo::collections::{CollectIn, Vec};
 use roc_builtins::bitcode::{self, FloatWidth, IntWidth};
@@ -150,6 +150,8 @@ pub enum CompareOperation {
 /// Generally, I prefer explicit sources, as opposed to dst being one of the sources. Ex: `x = x + y` would be `add x, x, y` instead of `add x, y`.
 /// dst should always come before sources.
 pub trait Assembler<GeneralReg: RegTrait, FloatReg: RegTrait>: Sized + Copy {
+    fn base_pointer() -> GeneralReg;
+
     fn abs_reg64_reg64(buf: &mut Vec<'_, u8>, dst: GeneralReg, src: GeneralReg);
     fn abs_freg64_freg64(
         buf: &mut Vec<'_, u8>,
@@ -517,7 +519,7 @@ pub trait Assembler<GeneralReg: RegTrait, FloatReg: RegTrait>: Sized + Copy {
         Self::eq_reg_reg_reg(buf, RegisterWidth::W64, dst, src1, src2)
     }
 
-    fn neq_reg64_reg64_reg64(
+    fn neq_reg_reg_reg(
         buf: &mut Vec<'_, u8>,
         register_width: RegisterWidth,
         dst: GeneralReg,
@@ -904,27 +906,30 @@ impl<
                 ASM::mov_base32_reg64(&mut self.buf, offset, CC::GENERAL_RETURN_REGS[0]);
                 ASM::mov_base32_reg64(&mut self.buf, offset + 8, CC::GENERAL_RETURN_REGS[1]);
             }
-
+            pointer_layouts!() => {
-            other => {
+                let dst_reg = self.storage_manager.claim_general_reg(&mut self.buf, dst);
-                //
+                ASM::mov_reg64_reg64(&mut self.buf, dst_reg, CC::GENERAL_RETURN_REGS[0]);
-                match other {
+            }
-                    LayoutRepr::Boxed(_) => {
+            LayoutRepr::LambdaSet(lambda_set) => {
-                        let dst_reg = self.storage_manager.claim_general_reg(&mut self.buf, dst);
+                self.move_return_value(dst, &lambda_set.runtime_representation())
-                        ASM::mov_reg64_reg64(&mut self.buf, dst_reg, CC::GENERAL_RETURN_REGS[0]);
+            }
-                    }
+            LayoutRepr::Union(UnionLayout::NonRecursive(_)) => {
-                    LayoutRepr::LambdaSet(lambda_set) => {
+                CC::load_returned_complex_symbol(
-                        self.move_return_value(dst, &lambda_set.runtime_representation())
+                    &mut self.buf,
-                    }
+                    &mut self.storage_manager,
-                    _ => {
+                    self.layout_interner,
-                        CC::load_returned_complex_symbol(
+                    dst,
-                            &mut self.buf,
+                    ret_layout,
-                            &mut self.storage_manager,
+                );
-                            self.layout_interner,
+            }
-                            dst,
+            _ => {
-                            ret_layout,
+                CC::load_returned_complex_symbol(
-                        );
+                    &mut self.buf,
-                    }
+                    &mut self.storage_manager,
-                }
+                    self.layout_interner,
+                    dst,
+                    ret_layout,
+                );
             }
         }
     }
@@ -1558,7 +1563,7 @@ impl<
                 let src2_reg = self
                     .storage_manager
                     .load_to_general_reg(&mut self.buf, src2);
-                ASM::neq_reg64_reg64_reg64(&mut self.buf, width, dst_reg, src1_reg, src2_reg);
+                ASM::neq_reg_reg_reg(&mut self.buf, width, dst_reg, src1_reg, src2_reg);
             }
             LayoutRepr::STR => {
                 self.build_fn_call(
@@ -1576,7 +1581,7 @@ impl<
 
                 let width = RegisterWidth::W8; // we're comparing booleans
                 let dst_reg = self.storage_manager.load_to_general_reg(&mut self.buf, dst);
-                ASM::neq_reg64_reg64_reg64(&mut self.buf, width, dst_reg, dst_reg, tmp_reg);
+                ASM::neq_reg_reg_reg(&mut self.buf, width, dst_reg, dst_reg, tmp_reg);
             }
             x => todo!("NumNeq: layout, {:?}", x),
         }
@@ -1714,25 +1719,13 @@ impl<
                         ASM::xor_reg64_reg64_reg64(buf, dst_reg, dst_reg, dst_reg); // zero out dst reg
                         ASM::mov_reg32_freg32(buf, dst_reg, src_reg);
                         ASM::and_reg64_reg64_reg64(buf, dst_reg, dst_reg, mask_reg);
-                        ASM::neq_reg64_reg64_reg64(
+                        ASM::neq_reg_reg_reg(buf, RegisterWidth::W32, dst_reg, dst_reg, mask_reg);
-                            buf,
-                            RegisterWidth::W32,
-                            dst_reg,
-                            dst_reg,
-                            mask_reg,
-                        );
                     }
                     Layout::F64 => {
                         ASM::mov_reg64_imm64(buf, mask_reg, 0x7ff0_0000_0000_0000);
                         ASM::mov_reg64_freg64(buf, dst_reg, src_reg);
                         ASM::and_reg64_reg64_reg64(buf, dst_reg, dst_reg, mask_reg);
-                        ASM::neq_reg64_reg64_reg64(
+                        ASM::neq_reg_reg_reg(buf, RegisterWidth::W64, dst_reg, dst_reg, mask_reg);
-                            buf,
-                            RegisterWidth::W64,
-                            dst_reg,
-                            dst_reg,
-                            mask_reg,
-                        );
                     }
                     _ => unreachable!(),
                 }
@@ -2213,6 +2206,7 @@ impl<
                         storage_manager,
                         self.layout_interner,
                         element_ptr,
+                        0,
                         *ret_layout,
                         *dst,
                     );
@@ -2600,7 +2594,7 @@ impl<
         union_layout: &UnionLayout<'a>,
     ) {
         match union_layout {
-            UnionLayout::NonRecursive(tag_layouts) | UnionLayout::Recursive(tag_layouts) => {
+            UnionLayout::NonRecursive(tag_layouts) => {
                 self.storage_manager.load_field_at_index(
                     self.layout_interner,
                     sym,
@@ -2609,6 +2603,77 @@ impl<
                     tag_layouts[tag_id as usize],
                 );
             }
+            UnionLayout::NullableUnwrapped {
+                nullable_id,
+                other_fields,
+            } => {
+                debug_assert_ne!(tag_id, *nullable_id as TagIdIntType);
+
+                let element_layout = other_fields[index as usize];
+
+                let ptr_reg = self
+                    .storage_manager
+                    .load_to_general_reg(&mut self.buf, structure);
+
+                let mut offset = 0;
+                for field in &other_fields[..index as usize] {
+                    offset += self.layout_interner.stack_size(*field);
+                }
+
+                Self::ptr_read(
+                    &mut self.buf,
+                    &mut self.storage_manager,
+                    self.layout_interner,
+                    ptr_reg,
+                    offset as i32,
+                    element_layout,
+                    *sym,
+                );
+            }
+
+            UnionLayout::NullableWrapped {
+                nullable_id,
+                other_tags,
+            } => {
+                debug_assert_ne!(tag_id, *nullable_id as TagIdIntType);
+
+                let other_fields = if tag_id < *nullable_id {
+                    other_tags[tag_id as usize]
+                } else {
+                    other_tags[tag_id as usize - 1]
+                };
+
+                let element_layout = other_fields[index as usize];
+
+                let ptr_reg = self
+                    .storage_manager
+                    .load_to_general_reg(&mut self.buf, structure);
+
+                let mask_symbol = self.debug_symbol("tag_id_mask");
+                let mask_reg = self
+                    .storage_manager
+                    .claim_general_reg(&mut self.buf, &mask_symbol);
+                ASM::mov_reg64_imm64(&mut self.buf, mask_reg, (!0b111) as _);
+
+                // mask out the tag id bits
+                ASM::and_reg64_reg64_reg64(&mut self.buf, ptr_reg, ptr_reg, mask_reg);
+
+                let mut offset = 0;
+                for field in &other_fields[..index as usize] {
+                    offset += self.layout_interner.stack_size(*field);
+                }
+
+                Self::ptr_read(
+                    &mut self.buf,
+                    &mut self.storage_manager,
+                    self.layout_interner,
+                    ptr_reg,
+                    offset as i32,
+                    element_layout,
+                    *sym,
+                );
+            }
+
             _ => {
                 let union_in_layout = self
                     .layout_interner
@@ -2653,11 +2718,17 @@ impl<
         }
 
         // box is just a pointer on the stack
-        let base_offset = self.storage_manager.claim_stack_area(&sym, 8);
+        let base_offset = self.storage_manager.claim_pointer_stack_area(sym);
         ASM::mov_base32_reg64(&mut self.buf, base_offset, ptr_reg);
     }
 
-    fn expr_box(&mut self, sym: Symbol, value: Symbol, element_layout: InLayout<'a>) {
+    fn expr_box(
+        &mut self,
+        sym: Symbol,
+        value: Symbol,
+        element_layout: InLayout<'a>,
+        reuse: Option<Symbol>,
+    ) {
         let element_width_symbol = Symbol::DEV_TMP;
         self.load_layout_stack_size(element_layout, element_width_symbol);
 
@@ -2665,18 +2736,27 @@ impl<
         let element_alignment_symbol = Symbol::DEV_TMP2;
         self.load_layout_alignment(Layout::U32, element_alignment_symbol);
 
-        self.allocate_with_refcount(
+        let allocation = self.debug_symbol("allocation");
-            Symbol::DEV_TMP3,
+
-            element_width_symbol,
+        match reuse {
-            element_alignment_symbol,
+            None => {
-        );
+                self.allocate_with_refcount(
+                    allocation,
+                    element_width_symbol,
+                    element_alignment_symbol,
+                );
+            }
+            Some(reuse) => {
+                self.allocate_with_refcount_if_null(allocation, reuse, element_layout);
+            }
+        };
 
         self.free_symbol(&element_width_symbol);
         self.free_symbol(&element_alignment_symbol);
 
-        self.build_ptr_write(sym, Symbol::DEV_TMP3, value, element_layout);
+        self.build_ptr_write(sym, allocation, value, element_layout);
 
-        self.free_symbol(&Symbol::DEV_TMP3);
+        self.free_symbol(&allocation);
     }
 
     fn expr_unbox(&mut self, dst: Symbol, ptr: Symbol, element_layout: InLayout<'a>) {
@@ -2684,24 +2764,135 @@ impl<
             .storage_manager
             .load_to_general_reg(&mut self.buf, &ptr);
 
+        let offset = 0;
+
         Self::ptr_read(
             &mut self.buf,
             &mut self.storage_manager,
             self.layout_interner,
             ptr_reg,
+            offset,
             element_layout,
             dst,
         );
     }
 
     fn get_tag_id(&mut self, sym: &Symbol, structure: &Symbol, union_layout: &UnionLayout<'a>) {
-        self.storage_manager.load_union_tag_id(
+        let layout_interner: &mut STLayoutInterner<'a> = self.layout_interner;
-            self.layout_interner,
+        let _buf: &mut Vec<'a, u8> = &mut self.buf;
-            &mut self.buf,
+        match union_layout {
-            sym,
+            UnionLayout::NonRecursive(tags) => {
-            structure,
+                self.storage_manager.load_union_tag_id_nonrecursive(
-            union_layout,
+                    layout_interner,
-        );
+                    &mut self.buf,
+                    sym,
+                    structure,
+                    tags,
+                );
+            }
+            UnionLayout::NullableUnwrapped { nullable_id, .. } => {
+                // simple is_null check on the pointer
+                let tmp = Symbol::DEV_TMP5;
+                let reg = self.storage_manager.claim_general_reg(&mut self.buf, &tmp);
+                ASM::mov_reg64_imm64(&mut self.buf, reg, 0);
+
+                let dst_reg = self.storage_manager.claim_general_reg(&mut self.buf, sym);
+                let src1_reg = reg;
+                let src2_reg = self
+                    .storage_manager
+                    .load_to_general_reg(&mut self.buf, structure);
+
+                match *nullable_id {
+                    true => {
+                        ASM::eq_reg_reg_reg(
+                            &mut self.buf,
+                            RegisterWidth::W64,
+                            dst_reg,
+                            src1_reg,
+                            src2_reg,
+                        );
+                    }
+                    false => {
+                        ASM::neq_reg_reg_reg(
+                            &mut self.buf,
+                            RegisterWidth::W64,
+                            dst_reg,
+                            src1_reg,
+                            src2_reg,
+                        );
+                    }
+                }
+
+                self.free_symbol(&tmp);
+            }
+            UnionLayout::NullableWrapped {
+                nullable_id,
+                other_tags,
+            } => {
+                let number_of_tags = other_tags.len() + 1;
+
+                let dst_reg = self.storage_manager.claim_general_reg(&mut self.buf, sym);
+
+                // build a table to index into with the value that we find
+                let nullable_id = *nullable_id as usize;
+                let it = std::iter::once(nullable_id)
+                    .chain(0..nullable_id)
+                    .chain(nullable_id + 1..number_of_tags);
+
+                let table = self.debug_symbol("tag_id_table");
+                let table_offset = self
+                    .storage_manager
+                    .claim_stack_area(&table, (number_of_tags * 2) as _);
+
+                let mut offset = table_offset;
+                for i in it {
+                    ASM::mov_reg64_imm64(&mut self.buf, dst_reg, i as i64);
+                    ASM::mov_base32_reg16(&mut self.buf, offset, dst_reg);
+
+                    offset += 2;
+                }
+
+                self.free_symbol(&table);
+
+                // mask the 3 lowest bits
+                let tmp = Symbol::DEV_TMP5;
+                let reg = self.storage_manager.claim_general_reg(&mut self.buf, &tmp);
+                ASM::mov_reg64_imm64(&mut self.buf, reg, 0b111);
+
+                let src1_reg = reg;
+                let src2_reg = self
+                    .storage_manager
+                    .load_to_general_reg(&mut self.buf, structure);
+
+                ASM::and_reg64_reg64_reg64(&mut self.buf, dst_reg, src1_reg, src2_reg);
+
+                // we're indexing into an array of u16, so double this index
+                // also the stack grows down, so negate the index
+                ASM::mov_reg64_imm64(&mut self.buf, reg, 2);
+                ASM::umul_reg64_reg64_reg64(
+                    &mut self.buf,
+                    &mut self.storage_manager,
+                    dst_reg,
+                    dst_reg,
+                    reg,
+                );
+
+                // index into the table
+                let base_pointer = ASM::base_pointer();
+                ASM::add_reg64_reg64_reg64(&mut self.buf, dst_reg, dst_reg, base_pointer);
+
+                // load the 16-bit value at the pointer
+                ASM::mov_reg16_mem16_offset32(&mut self.buf, dst_reg, dst_reg, table_offset);
+
+                // keep only the lowest 16 bits
+                ASM::mov_reg64_imm64(&mut self.buf, reg, 0xFFFF);
+                ASM::and_reg64_reg64_reg64(&mut self.buf, dst_reg, dst_reg, reg);
+
+                self.free_symbol(&tmp);
+            }
+
+            x => todo!("getting tag id of union with layout ({:?})", x),
+        };
     }
 
     fn tag(
@@ -2710,15 +2901,144 @@ impl<
         fields: &'a [Symbol],
         union_layout: &UnionLayout<'a>,
         tag_id: TagIdIntType,
+        reuse: Option<Symbol>,
     ) {
-        self.storage_manager.create_union(
+        let target_info = self.storage_manager.target_info;
-            self.layout_interner,
+
-            &mut self.buf,
+        let layout_interner: &mut STLayoutInterner<'a> = self.layout_interner;
-            sym,
+        let buf: &mut Vec<'a, u8> = &mut self.buf;
-            union_layout,
+
-            fields,
+        let (data_size, data_alignment) =
-            tag_id,
+            union_layout.data_size_and_alignment(layout_interner, target_info);
-        )
+
+        match union_layout {
+            UnionLayout::NonRecursive(field_layouts) => {
+                let id_offset = data_size - data_alignment;
+                let base_offset = self.storage_manager.claim_stack_area(sym, data_size);
+                let mut current_offset = base_offset;
+
+                let it = fields.iter().zip(field_layouts[tag_id as usize].iter());
+                for (field, field_layout) in it {
+                    self.storage_manager.copy_symbol_to_stack_offset(
+                        layout_interner,
+                        buf,
+                        current_offset,
+                        field,
+                        field_layout,
+                    );
+                    let field_size = layout_interner.stack_size(*field_layout);
+                    current_offset += field_size as i32;
+                }
+
+                // put the tag id in the right place
+                self.storage_manager
+                    .with_tmp_general_reg(buf, |_symbol_storage, buf, reg| {
+                        ASM::mov_reg64_imm64(buf, reg, tag_id as i64);
+
+                        let total_id_offset = base_offset as u32 + id_offset;
+                        debug_assert!(total_id_offset % data_alignment == 0);
+
+                        // pick the right instruction based on the alignment of the tag id
+                        if field_layouts.len() <= u8::MAX as _ {
+                            ASM::mov_base32_reg8(buf, total_id_offset as i32, reg);
+                        } else {
+                            ASM::mov_base32_reg16(buf, total_id_offset as i32, reg);
+                        }
+                    });
+            }
+            UnionLayout::NullableUnwrapped {
+                nullable_id,
+                other_fields,
+            } => {
+                if tag_id == *nullable_id as TagIdIntType {
+                    // it's just a null pointer
+                    self.load_literal_i64(sym, 0);
+                } else {
+                    // construct the payload as a struct on the stack
+                    let temp_sym = Symbol::DEV_TMP5;
+                    let layout = self
+                        .layout_interner
+                        .insert_no_semantic(LayoutRepr::Struct(other_fields));
+
+                    self.load_literal_symbols(fields);
+                    self.storage_manager.create_struct(
+                        self.layout_interner,
+                        &mut self.buf,
+                        &temp_sym,
+                        &layout,
+                        fields,
+                    );
+
+                    // now effectively box this struct
+                    self.expr_box(*sym, temp_sym, layout, reuse);
+
+                    self.free_symbol(&temp_sym);
+                }
+            }
+            UnionLayout::NullableWrapped {
+                nullable_id,
+                other_tags,
+            } => {
+                let nullable_id = *nullable_id;
+
+                if tag_id == nullable_id as TagIdIntType {
+                    // it's just a null pointer
+                    self.load_literal_i64(sym, 0);
+                } else {
+                    let other_fields = if tag_id < nullable_id {
+                        other_tags[tag_id as usize]
+                    } else {
+                        other_tags[tag_id as usize - 1]
+                    };
+
+                    // construct the payload as a struct on the stack
+                    let temp_sym = Symbol::DEV_TMP5;
+                    let layout = self
+                        .layout_interner
+                        .insert_no_semantic(LayoutRepr::Struct(other_fields));
+
+                    self.load_literal_symbols(fields);
+                    self.storage_manager.create_struct(
+                        self.layout_interner,
+                        &mut self.buf,
+                        &temp_sym,
+                        &layout,
+                        fields,
+                    );
+
+                    // now effectively box this struct
+                    let untagged_pointer_symbol = self.debug_symbol("untagged_pointer");
+                    self.expr_box(untagged_pointer_symbol, temp_sym, layout, reuse);
+
+                    self.free_symbol(&temp_sym);
+
+                    let tag_id_symbol = self.debug_symbol("tag_id");
+
+                    // index zero is taken up by the nullable tag, so any tags before it in the
+                    // ordering need to be incremented by one
+                    let pointer_tag = if tag_id < nullable_id {
+                        tag_id + 1
+                    } else {
+                        tag_id
+                    };
+
+                    // finally, we need to tag the pointer
+                    debug_assert!(tag_id < 8);
+                    self.load_literal_i64(&tag_id_symbol, pointer_tag as _);
+
+                    self.build_int_bitwise_or(
+                        sym,
+                        &untagged_pointer_symbol,
+                        &tag_id_symbol,
+                        IntWidth::U64,
+                    );
+
+                    self.free_symbol(&untagged_pointer_symbol);
+                    self.free_symbol(&tag_id_symbol);
+                }
+            }
+            x => todo!("creating unions with layout: {:?}", x),
+        }
     }
 
     fn load_literal(&mut self, sym: &Symbol, layout: &InLayout<'a>, lit: &Literal<'a>) {
@@ -2860,7 +3180,7 @@ impl<
         if self.storage_manager.is_stored_primitive(sym) {
             // Just load it to the correct type of reg as a stand alone value.
             match repr {
-                single_register_integers!() => {
+                single_register_integers!() | pointer_layouts!() => {
                     self.storage_manager.load_to_specified_general_reg(
                         &mut self.buf,
                         sym,
@@ -2874,22 +3194,14 @@ impl<
                         CC::FLOAT_RETURN_REGS[0],
                     );
                 }
-                other => match other {
+                LayoutRepr::LambdaSet(lambda_set) => {
-                    LayoutRepr::Boxed(_) => {
+                    self.return_symbol(sym, &lambda_set.runtime_representation())
-                        // treat like a 64-bit integer
+                }
-                        self.storage_manager.load_to_specified_general_reg(
+                LayoutRepr::Union(UnionLayout::NonRecursive(_))
-                            &mut self.buf,
+                | LayoutRepr::Builtin(_)
-                            sym,
+                | LayoutRepr::Struct(_) => {
-                            CC::GENERAL_RETURN_REGS[0],
+                    internal_error!("All primitive values should fit in a single register");
-                        );
+                }
-                    }
-                    LayoutRepr::LambdaSet(lambda_set) => {
-                        self.return_symbol(sym, &lambda_set.runtime_representation())
-                    }
-                    _ => {
-                        internal_error!("All primitive values should fit in a single register");
-                    }
-                },
             }
         } else {
             CC::return_complex_symbol(
@@ -3297,22 +3609,78 @@ impl<
         );
     }
 
+    fn allocate_with_refcount_if_null(&mut self, dst: Symbol, src: Symbol, layout: InLayout) {
+        let src_reg = self
+            .storage_manager
+            .load_to_general_reg(&mut self.buf, &src);
+
+        // dummy mov that is supposed to move src into dst, and is filled in later because don't know yet which
+        // register the other branch will pick for dst. We must pass two different registers here
+        // otherwise the whole instruction is skipped!
+        let dst_reg = self.storage_manager.claim_general_reg(&mut self.buf, &dst);
+        let mov_start_index = self.buf.len();
+        ASM::mov_reg64_reg64(&mut self.buf, dst_reg, src_reg);
+
+        // jump to where the pointer is valid, because it is already valid if non-zero
+        let jmp_start_index = self.buf.len();
+        let jmp_end_index = ASM::jne_reg64_imm64_imm32(&mut self.buf, src_reg, 0x0, 0);
+
+        self.free_symbol(&dst);
+
+        // so, the pointer is NULL, allocate
+
+        let data_bytes = self.debug_symbol("data_bytes");
+        self.load_layout_stack_size(layout, data_bytes);
+
+        let element_alignment = self.debug_symbol("element_alignment");
+        self.load_layout_alignment(layout, element_alignment);
+
+        self.allocate_with_refcount(dst, data_bytes, element_alignment);
+
+        self.free_symbol(&data_bytes);
+        self.free_symbol(&element_alignment);
+
+        let mut tmp = bumpalo::vec![in self.env.arena];
+
+        // update the jump
+        let destination_index = self.buf.len();
+        ASM::jne_reg64_imm64_imm32(
+            &mut tmp,
+            src_reg,
+            0x0,
+            (destination_index - jmp_end_index) as i32,
+        );
+
+        self.buf[jmp_start_index..][..tmp.len()].copy_from_slice(tmp.as_slice());
+
+        // figure out what register was actually used
+        let dst_reg = self
+            .storage_manager
+            .load_to_general_reg(&mut self.buf, &dst);
+
+        tmp.clear();
+        ASM::mov_reg64_reg64(&mut tmp, dst_reg, src_reg);
+
+        self.buf[mov_start_index..][..tmp.len()].copy_from_slice(tmp.as_slice());
+    }
+
     fn unbox_str_or_list(
         buf: &mut Vec<'a, u8>,
         storage_manager: &mut StorageManager<'a, 'r, GeneralReg, FloatReg, ASM, CC>,
         dst: Symbol,
         ptr_reg: GeneralReg,
         tmp_reg: GeneralReg,
+        offset: i32,
     ) {
         let base_offset = storage_manager.claim_stack_area(&dst, 24);
 
-        ASM::mov_reg64_mem64_offset32(buf, tmp_reg, ptr_reg, 0);
+        ASM::mov_reg64_mem64_offset32(buf, tmp_reg, ptr_reg, offset);
         ASM::mov_base32_reg64(buf, base_offset, tmp_reg);
 
-        ASM::mov_reg64_mem64_offset32(buf, tmp_reg, ptr_reg, 8);
+        ASM::mov_reg64_mem64_offset32(buf, tmp_reg, ptr_reg, offset + 8);
         ASM::mov_base32_reg64(buf, base_offset + 8, tmp_reg);
 
-        ASM::mov_reg64_mem64_offset32(buf, tmp_reg, ptr_reg, 16);
+        ASM::mov_reg64_mem64_offset32(buf, tmp_reg, ptr_reg, offset + 16);
         ASM::mov_base32_reg64(buf, base_offset + 16, tmp_reg);
     }
 
@@ -3323,6 +3691,7 @@ impl<
         stack_size: u32,
         ptr_reg: GeneralReg,
         tmp_reg: GeneralReg,
+        read_offset: i32,
     ) {
         let mut copied = 0;
         let size = stack_size as i32;
@@ -3336,7 +3705,7 @@ impl<
 
         if size - copied >= 8 {
             for _ in (0..(size - copied)).step_by(8) {
-                ASM::mov_reg64_mem64_offset32(buf, tmp_reg, ptr_reg, copied);
+                ASM::mov_reg64_mem64_offset32(buf, tmp_reg, ptr_reg, read_offset + copied);
                 ASM::mov_base32_reg64(buf, base_offset + copied, tmp_reg);
 
                 copied += 8;
@@ -3345,7 +3714,7 @@ impl<
 
         if size - copied >= 4 {
             for _ in (0..(size - copied)).step_by(4) {
-                ASM::mov_reg32_mem32_offset32(buf, tmp_reg, ptr_reg, copied);
+                ASM::mov_reg32_mem32_offset32(buf, tmp_reg, ptr_reg, read_offset + copied);
                 ASM::mov_base32_reg32(buf, base_offset + copied, tmp_reg);
 
                 copied += 4;
@@ -3354,7 +3723,7 @@ impl<
 
         if size - copied >= 2 {
             for _ in (0..(size - copied)).step_by(2) {
-                ASM::mov_reg16_mem16_offset32(buf, tmp_reg, ptr_reg, copied);
+                ASM::mov_reg16_mem16_offset32(buf, tmp_reg, ptr_reg, read_offset + copied);
                 ASM::mov_base32_reg16(buf, base_offset + copied, tmp_reg);
 
                 copied += 2;
@@ -3363,7 +3732,7 @@ impl<
 
         if size - copied >= 1 {
             for _ in (0..(size - copied)).step_by(1) {
-                ASM::mov_reg8_mem8_offset32(buf, tmp_reg, ptr_reg, copied);
+                ASM::mov_reg8_mem8_offset32(buf, tmp_reg, ptr_reg, read_offset + copied);
                 ASM::mov_base32_reg8(buf, base_offset + copied, tmp_reg);
 
                 copied += 1;
@@ -3376,6 +3745,7 @@ impl<
         storage_manager: &mut StorageManager<'a, 'r, GeneralReg, FloatReg, ASM, CC>,
         layout_interner: &STLayoutInterner<'a>,
         ptr_reg: GeneralReg,
+        offset: i32,
         element_in_layout: InLayout<'a>,
         dst: Symbol,
     ) {
@@ -3388,48 +3758,55 @@ impl<
                     }
                     IntWidth::I64 | IntWidth::U64 => {
                         let dst_reg = storage_manager.claim_general_reg(buf, &dst);
-                        ASM::mov_reg64_mem64_offset32(buf, dst_reg, ptr_reg, 0);
+                        ASM::mov_reg64_mem64_offset32(buf, dst_reg, ptr_reg, offset);
                     }
                     IntWidth::I32 | IntWidth::U32 => {
                         let dst_reg = storage_manager.claim_general_reg(buf, &dst);
-                        ASM::mov_reg32_mem32_offset32(buf, dst_reg, ptr_reg, 0);
+                        ASM::mov_reg32_mem32_offset32(buf, dst_reg, ptr_reg, offset);
                     }
                     IntWidth::I16 | IntWidth::U16 => {
                         let dst_reg = storage_manager.claim_general_reg(buf, &dst);
-                        ASM::mov_reg16_mem16_offset32(buf, dst_reg, ptr_reg, 0);
+                        ASM::mov_reg16_mem16_offset32(buf, dst_reg, ptr_reg, offset);
                     }
                     IntWidth::I8 | IntWidth::U8 => {
                         let dst_reg = storage_manager.claim_general_reg(buf, &dst);
-                        ASM::mov_reg8_mem8_offset32(buf, dst_reg, ptr_reg, 0);
+                        ASM::mov_reg8_mem8_offset32(buf, dst_reg, ptr_reg, offset);
                     }
                 },
                 Builtin::Float(FloatWidth::F64) => {
                     let dst_reg = storage_manager.claim_float_reg(buf, &dst);
-                    ASM::mov_freg64_mem64_offset32(buf, dst_reg, ptr_reg, 0);
+                    ASM::mov_freg64_mem64_offset32(buf, dst_reg, ptr_reg, offset);
                 }
                 Builtin::Float(FloatWidth::F32) => {
                     let dst_reg = storage_manager.claim_float_reg(buf, &dst);
-                    ASM::mov_freg32_mem32_offset32(buf, dst_reg, ptr_reg, 0);
+                    ASM::mov_freg32_mem32_offset32(buf, dst_reg, ptr_reg, offset);
                 }
                 Builtin::Bool => {
                     // the same as an 8-bit integer
                     let dst_reg = storage_manager.claim_general_reg(buf, &dst);
-                    ASM::mov_reg8_mem8_offset32(buf, dst_reg, ptr_reg, 0);
+                    ASM::mov_reg8_mem8_offset32(buf, dst_reg, ptr_reg, offset);
                 }
                 Builtin::Decimal => {
                     // same as 128-bit integer
                 }
                 Builtin::Str | Builtin::List(_) => {
                     storage_manager.with_tmp_general_reg(buf, |storage_manager, buf, tmp_reg| {
-                        Self::unbox_str_or_list(buf, storage_manager, dst, ptr_reg, tmp_reg);
+                        Self::unbox_str_or_list(
+                            buf,
+                            storage_manager,
+                            dst,
+                            ptr_reg,
+                            tmp_reg,
+                            offset,
+                        );
                     });
                 }
             },
 
-            LayoutRepr::Boxed(_) => {
+            pointer_layouts!() => {
                 // the same as 64-bit integer (for 64-bit targets)
                 let dst_reg = storage_manager.claim_general_reg(buf, &dst);
-                ASM::mov_reg64_mem64_offset32(buf, dst_reg, ptr_reg, 0);
+                ASM::mov_reg64_mem64_offset32(buf, dst_reg, ptr_reg, offset);
             }
 
             LayoutRepr::Struct { .. } => {
@@ -3437,7 +3814,15 @@ impl<
                 let stack_size = layout_interner.stack_size(element_in_layout);
 
                 storage_manager.with_tmp_general_reg(buf, |storage_manager, buf, tmp_reg| {
-                    Self::unbox_to_stack(buf, storage_manager, dst, stack_size, ptr_reg, tmp_reg);
+                    Self::unbox_to_stack(
+                        buf,
+                        storage_manager,
+                        dst,
+                        stack_size,
+                        ptr_reg,
+                        tmp_reg,
+                        offset,
+                    );
                 });
             }
 
@@ -3446,7 +3831,15 @@ impl<
                 let stack_size = layout_interner.stack_size(element_in_layout);
 
                 storage_manager.with_tmp_general_reg(buf, |storage_manager, buf, tmp_reg| {
-                    Self::unbox_to_stack(buf, storage_manager, dst, stack_size, ptr_reg, tmp_reg);
+                    Self::unbox_to_stack(
+                        buf,
+                        storage_manager,
+                        dst,
+                        stack_size,
+                        ptr_reg,
+                        tmp_reg,
+                        offset,
+                    );
                 });
             }
 
@@ -3456,12 +3849,11 @@ impl<
                     storage_manager,
                     layout_interner,
                     ptr_reg,
+                    offset,
                     lambda_set.runtime_representation(),
                     dst,
                 );
             }
-
-            _ => todo!("unboxing of {:?}", layout_interner.dbg(element_in_layout)),
         }
     }
 
@@ -3497,7 +3889,7 @@ impl<
                 let sym_reg = storage_manager.load_to_float_reg(buf, &value);
                 ASM::movesd_mem64_offset32_freg64(buf, ptr_reg, element_offset, sym_reg);
             }
-            LayoutRepr::Boxed(_) => {
+            pointer_layouts!() => {
                 let sym_reg = storage_manager.load_to_general_reg(buf, &value);
                 ASM::mov_mem64_offset32_reg64(buf, ptr_reg, element_offset, sym_reg);
             }
@@ -3605,7 +3997,7 @@ impl<
     }
 
     /// Loads the alignment bytes of `layout` into the given `symbol`
-    fn load_layout_alignment(&mut self, layout: InLayout<'a>, symbol: Symbol) {
+    fn load_layout_alignment(&mut self, layout: InLayout<'_>, symbol: Symbol) {
         let u32_layout = Layout::U32;
         let alignment = self.layout_interner.alignment_bytes(layout);
         let alignment_literal = Literal::Int((alignment as i128).to_ne_bytes());
@@ -3614,7 +4006,7 @@ impl<
     }
 
     /// Loads the stack size of `layout` into the given `symbol`
-    fn load_layout_stack_size(&mut self, layout: InLayout<'a>, symbol: Symbol) {
+    fn load_layout_stack_size(&mut self, layout: InLayout<'_>, symbol: Symbol) {
         let u64_layout = Layout::U64;
         let width = self.layout_interner.stack_size(layout);
         let width_literal = Literal::Int((width as i128).to_ne_bytes());
@@ -3671,3 +4063,17 @@ macro_rules! single_register_layouts {
         single_register_integers!() | single_register_floats!()
     };
 }
+
+#[macro_export]
+macro_rules! pointer_layouts {
+    () => {
+        LayoutRepr::Boxed(_)
+            | LayoutRepr::RecursivePointer(_)
+            | LayoutRepr::Union(
+                UnionLayout::Recursive(_)
+                    | UnionLayout::NonNullableUnwrapped(_)
+                    | UnionLayout::NullableWrapped { .. }
+                    | UnionLayout::NullableUnwrapped { .. },
+            )
+    };
+}

crates/compiler/gen_dev/src/generic64/storage.rs

@@ -1,7 +1,7 @@
 use crate::{
     generic64::{Assembler, CallConv, RegTrait},
-    sign_extended_int_builtins, single_register_floats, single_register_int_builtins,
+    pointer_layouts, sign_extended_int_builtins, single_register_floats,
-    single_register_integers, single_register_layouts, Env,
+    single_register_int_builtins, single_register_integers, single_register_layouts, Env,
 };
 use bumpalo::collections::Vec;
 use roc_builtins::bitcode::{FloatWidth, IntWidth};
@@ -11,8 +11,7 @@ use roc_module::symbol::Symbol;
 use roc_mono::{
     ir::{JoinPointId, Param},
     layout::{
-        Builtin, InLayout, Layout, LayoutInterner, LayoutRepr, STLayoutInterner, TagIdIntType,
+        Builtin, InLayout, Layout, LayoutInterner, LayoutRepr, STLayoutInterner, UnionLayout,
-        UnionLayout,
     },
 };
 use roc_target::TargetInfo;
@@ -91,7 +90,7 @@ pub struct StorageManager<
     phantom_cc: PhantomData<CC>,
     phantom_asm: PhantomData<ASM>,
     pub(crate) env: &'r Env<'a>,
-    target_info: TargetInfo,
+    pub(crate) target_info: TargetInfo,
     // Data about where each symbol is stored.
     symbol_storage_map: MutMap<Symbol, Storage<GeneralReg, FloatReg>>,
 
@@ -598,40 +597,38 @@ impl<
         }
     }
 
-    pub fn load_union_tag_id(
+    pub fn load_union_tag_id_nonrecursive(
         &mut self,
         layout_interner: &mut STLayoutInterner<'a>,
         _buf: &mut Vec<'a, u8>,
         sym: &Symbol,
         structure: &Symbol,
-        union_layout: &UnionLayout<'a>,
+        tags: &[&[InLayout]],
     ) {
+        let union_layout = UnionLayout::NonRecursive(tags);
+
         // This must be removed and reinserted for ownership and mutability reasons.
         let owned_data = self.remove_allocation_for_sym(structure);
         self.allocation_map
             .insert(*structure, Rc::clone(&owned_data));
-        match union_layout {
-            UnionLayout::NonRecursive(_) => {
-                let (union_offset, _) = self.stack_offset_and_size(structure);
 
-                let (data_size, data_alignment) =
+        let (union_offset, _) = self.stack_offset_and_size(structure);
-                    union_layout.data_size_and_alignment(layout_interner, self.target_info);
-                let id_offset = data_size - data_alignment;
-                let discriminant = union_layout.discriminant();
 
-                let size = discriminant.stack_size();
+        let (data_size, data_alignment) =
-                self.allocation_map.insert(*sym, owned_data);
+            union_layout.data_size_and_alignment(layout_interner, self.target_info);
-                self.symbol_storage_map.insert(
+        let id_offset = data_size - data_alignment;
-                    *sym,
+        let discriminant = union_layout.discriminant();
-                    Stack(ReferencedPrimitive {
+
-                        base_offset: union_offset + id_offset as i32,
+        let size = discriminant.stack_size();
-                        size,
+        self.allocation_map.insert(*sym, owned_data);
-                        sign_extend: false, // tag ids are always unsigned
+        self.symbol_storage_map.insert(
-                    }),
+            *sym,
-                );
+            Stack(ReferencedPrimitive {
-            }
+                base_offset: union_offset + id_offset as i32,
-            x => todo!("getting tag id of union with layout ({:?})", x),
+                size,
-        }
+                sign_extend: false, // tag ids are always unsigned
+            }),
+        );
     }
 
     // Loads the dst to be the later 64 bits of a list (its length).
@@ -700,56 +697,6 @@ impl<
         }
     }
 
-    /// Creates a union on the stack, moving the data in fields into the union and tagging it.
-    pub fn create_union(
-        &mut self,
-        layout_interner: &mut STLayoutInterner<'a>,
-        buf: &mut Vec<'a, u8>,
-        sym: &Symbol,
-        union_layout: &UnionLayout<'a>,
-        fields: &'a [Symbol],
-        tag_id: TagIdIntType,
-    ) {
-        match union_layout {
-            UnionLayout::NonRecursive(field_layouts) => {
-                let (data_size, data_alignment) =
-                    union_layout.data_size_and_alignment(layout_interner, self.target_info);
-                let id_offset = data_size - data_alignment;
-                let base_offset = self.claim_stack_area(sym, data_size);
-                let mut current_offset = base_offset;
-
-                let it = fields.iter().zip(field_layouts[tag_id as usize].iter());
-                for (field, field_layout) in it {
-                    self.copy_symbol_to_stack_offset(
-                        layout_interner,
-                        buf,
-                        current_offset,
-                        field,
-                        field_layout,
-                    );
-                    let field_size = layout_interner.stack_size(*field_layout);
-                    current_offset += field_size as i32;
-                }
-
-                // put the tag id in the right place
-                self.with_tmp_general_reg(buf, |_symbol_storage, buf, reg| {
-                    ASM::mov_reg64_imm64(buf, reg, tag_id as i64);
-
-                    let total_id_offset = base_offset as u32 + id_offset;
-                    debug_assert!(total_id_offset % data_alignment == 0);
-
-                    // pick the right instruction based on the alignment of the tag id
-                    if field_layouts.len() <= u8::MAX as _ {
-                        ASM::mov_base32_reg8(buf, total_id_offset as i32, reg);
-                    } else {
-                        ASM::mov_base32_reg16(buf, total_id_offset as i32, reg);
-                    }
-                });
-            }
-            x => todo!("creating unions with layout: {:?}", x),
-        }
-    }
-
     /// Copies a complex symbol on the stack to the arg pointer.
     pub fn copy_symbol_to_arg_pointer(
         &mut self,
@@ -845,12 +792,6 @@ impl<
                     self.copy_to_stack_offset(buf, size, from_offset, to_offset)
                 }
             },
-            LayoutRepr::Boxed(_) => {
-                // like a 64-bit integer
-                debug_assert_eq!(to_offset % 8, 0);
-                let reg = self.load_to_general_reg(buf, sym);
-                ASM::mov_base32_reg64(buf, to_offset, reg);
-            }
             LayoutRepr::LambdaSet(lambda_set) => {
                 // like its runtime representation
                 self.copy_symbol_to_stack_offset(
@@ -861,14 +802,18 @@ impl<
                     &lambda_set.runtime_representation(),
                 )
             }
-            _ if layout_interner.stack_size(*layout) == 0 => {}
             LayoutRepr::Struct { .. } | LayoutRepr::Union(UnionLayout::NonRecursive(_)) => {
                 let (from_offset, size) = self.stack_offset_and_size(sym);
                 debug_assert_eq!(size, layout_interner.stack_size(*layout));
 
                 self.copy_to_stack_offset(buf, size, from_offset, to_offset)
             }
-            x => todo!("copying data to the stack with layout, {:?}", x),
+            LayoutRepr::RecursivePointer(_) | LayoutRepr::Boxed(_) | LayoutRepr::Union(_) => {
+                // like a 64-bit integer
+                debug_assert_eq!(to_offset % 8, 0);
+                let reg = self.load_to_general_reg(buf, sym);
+                ASM::mov_base32_reg64(buf, to_offset, reg);
+            }
         }
     }
 
@@ -1160,7 +1105,7 @@ impl<
         layout: InLayout<'a>,
     ) {
         match layout_interner.get(layout).repr {
-            single_register_layouts!() => {
+            single_register_layouts!() | pointer_layouts!() => {
                 let base_offset = self.claim_stack_size(8);
                 self.symbol_storage_map.insert(
                     symbol,
@@ -1172,20 +1117,17 @@ impl<
                 self.allocation_map
                     .insert(symbol, Rc::new((base_offset, 8)));
             }
+            LayoutRepr::LambdaSet(lambda_set) => self.joinpoint_argument_stack_storage(
+                layout_interner,
+                symbol,
+                lambda_set.runtime_representation(),
+            ),
             _ => {
-                if let LayoutRepr::LambdaSet(lambda_set) = layout_interner.get(layout).repr {
+                let stack_size = layout_interner.stack_size(layout);
-                    self.joinpoint_argument_stack_storage(
+                if stack_size == 0 {
-                        layout_interner,
+                    self.no_data(&symbol);
-                        symbol,
-                        lambda_set.runtime_representation(),
-                    )
                 } else {
-                    let stack_size = layout_interner.stack_size(layout);
+                    self.claim_stack_area(&symbol, stack_size);
-                    if stack_size == 0 {
-                        self.no_data(&symbol);
-                    } else {
-                        self.claim_stack_area(&symbol, stack_size);
-                    }
                 }
             }
         }
@@ -1228,7 +1170,7 @@ impl<
         base_offset: i32,
     ) {
         match layout_interner.get(layout).repr {
-            single_register_integers!() => {
+            single_register_integers!() | pointer_layouts!() => {
                 let reg = self.load_to_general_reg(buf, &symbol);
                 ASM::mov_base32_reg64(buf, base_offset, reg);
             }
@@ -1236,27 +1178,21 @@ impl<
                 let reg = self.load_to_float_reg(buf, &symbol);
                 ASM::mov_base32_freg64(buf, base_offset, reg);
             }
-            _ => match layout_interner.get(layout).repr {
+            LayoutRepr::LambdaSet(lambda_set) => {
-                LayoutRepr::LambdaSet(lambda_set) => {
+                self.jump_argument_stack_storage(
-                    self.jump_argument_stack_storage(
+                    layout_interner,
-                        layout_interner,
+                    buf,
-                        buf,
+                    symbol,
-                        symbol,
+                    lambda_set.runtime_representation(),
-                        lambda_set.runtime_representation(),
+                    base_offset,
-                        base_offset,
+                );
-                    );
+            }
-                }
+            _ => {
-                LayoutRepr::Boxed(_) => {
+                internal_error!(
-                    let reg = self.load_to_general_reg(buf, &symbol);
+                    r"cannot load non-primitive layout ({:?}) to primitive stack location",
-                    ASM::mov_base32_reg64(buf, base_offset, reg);
+                    layout_interner.dbg(layout)
-                }
+                )
-                _ => {
+            }
-                    internal_error!(
-                        r"cannot load non-primitive layout ({:?}) to primitive stack location",
-                        layout_interner.dbg(layout)
-                    )
-                }
-            },
         }
     }
 
@@ -1341,6 +1277,22 @@ impl<
         base_offset
     }
 
+    pub fn claim_pointer_stack_area(&mut self, sym: Symbol) -> i32 {
+        let size = 8;
+
+        let base_offset = self.claim_stack_size(size);
+
+        self.symbol_storage_map.insert(
+            sym,
+            Stack(Primitive {
+                base_offset,
+                reg: None,
+            }),
+        );
+
+        base_offset
+    }
+
     /// claim_stack_size claims `amount` bytes from the stack alignind to 8.
     /// This may be free space in the stack or result in increasing the stack size.
     /// It returns base pointer relative offset of the new data.
@@ -1541,12 +1493,10 @@ impl<
 fn is_primitive(layout_interner: &mut STLayoutInterner<'_>, layout: InLayout<'_>) -> bool {
     match layout_interner.get(layout).repr {
         single_register_layouts!() => true,
-        _ => match layout_interner.get(layout).repr {
+        pointer_layouts!() => true,
-            LayoutRepr::Boxed(_) => true,
+        LayoutRepr::LambdaSet(lambda_set) => {
-            LayoutRepr::LambdaSet(lambda_set) => {
+            is_primitive(layout_interner, lambda_set.runtime_representation())
-                is_primitive(layout_interner, lambda_set.runtime_representation())
+        }
-            }
+        _ => false,
-            _ => false,
-        },
     }
 }

crates/compiler/gen_dev/src/generic64/x86_64.rs

@@ -1,7 +1,7 @@
 use crate::generic64::{storage::StorageManager, Assembler, CallConv, RegTrait};
 use crate::{
-    single_register_floats, single_register_int_builtins, single_register_integers,
+    pointer_layouts, single_register_floats, single_register_int_builtins,
-    single_register_layouts, Relocation,
+    single_register_integers, single_register_layouts, Relocation,
 };
 use bumpalo::collections::Vec;
 use roc_builtins::bitcode::{FloatWidth, IntWidth};
@@ -461,6 +461,7 @@ impl X64_64SystemVStoreArgs {
     ) {
         match layout_interner.get(in_layout).repr {
             single_register_integers!() => self.store_arg_general(buf, storage_manager, sym),
+            pointer_layouts!() => self.store_arg_general(buf, storage_manager, sym),
             single_register_floats!() => self.store_arg_float(buf, storage_manager, sym),
             LayoutRepr::I128 | LayoutRepr::U128 => {
                 let (offset, _) = storage_manager.stack_offset_and_size(&sym);
@@ -507,92 +508,83 @@ impl X64_64SystemVStoreArgs {
                 }
                 self.tmp_stack_offset += size as i32;
             }
-            other => {
+            LayoutRepr::LambdaSet(lambda_set) => self.store_arg(
-                // look at the layout in more detail
+                buf,
-                match other {
+                storage_manager,
-                    LayoutRepr::Boxed(_) => {
+                layout_interner,
-                        // treat boxed like a 64-bit integer
+                sym,
-                        self.store_arg_general(buf, storage_manager, sym)
+                lambda_set.runtime_representation(),
-                    }
+            ),
-                    LayoutRepr::LambdaSet(lambda_set) => self.store_arg(
+            LayoutRepr::Struct { .. } => {
+                // for now, just also store this on the stack
+                let (base_offset, size) = storage_manager.stack_offset_and_size(&sym);
+                debug_assert_eq!(base_offset % 8, 0);
+                for i in (0..size as i32).step_by(8) {
+                    X86_64Assembler::mov_reg64_base32(
                         buf,
-                        storage_manager,
+                        Self::GENERAL_RETURN_REGS[0],
-                        layout_interner,
+                        base_offset + i,
-                        sym,
+                    );
-                        lambda_set.runtime_representation(),
+                    X86_64Assembler::mov_stack32_reg64(
-                    ),
+                        buf,
-                    LayoutRepr::Struct { .. } => {
+                        self.tmp_stack_offset + i,
-                        // for now, just also store this on the stack
+                        Self::GENERAL_RETURN_REGS[0],
-                        let (base_offset, size) = storage_manager.stack_offset_and_size(&sym);
+                    );
-                        debug_assert_eq!(base_offset % 8, 0);
+                }
-                        for i in (0..size as i32).step_by(8) {
+                self.tmp_stack_offset += size as i32;
-                            X86_64Assembler::mov_reg64_base32(
+            }
-                                buf,
+            LayoutRepr::Union(UnionLayout::NonRecursive(_)) => {
-                                Self::GENERAL_RETURN_REGS[0],
+                type ASM = X86_64Assembler;
-                                base_offset + i,
-                            );
-                            X86_64Assembler::mov_stack32_reg64(
-                                buf,
-                                self.tmp_stack_offset + i,
-                                Self::GENERAL_RETURN_REGS[0],
-                            );
-                        }
-                        self.tmp_stack_offset += size as i32;
-                    }
-                    LayoutRepr::Union(UnionLayout::NonRecursive(_)) => {
-                        type ASM = X86_64Assembler;
 
-                        let tmp_reg = Self::GENERAL_RETURN_REGS[0];
+                let tmp_reg = Self::GENERAL_RETURN_REGS[0];
-                        let stack_offset = self.tmp_stack_offset;
+                let stack_offset = self.tmp_stack_offset;
 
-                        let mut copied = 0;
+                let mut copied = 0;
-                        let (base_offset, size) = storage_manager.stack_offset_and_size(&sym);
+                let (base_offset, size) = storage_manager.stack_offset_and_size(&sym);
 
-                        if size - copied >= 8 {
+                if size - copied >= 8 {
-                            for _ in (0..(size - copied)).step_by(8) {
+                    for _ in (0..(size - copied)).step_by(8) {
-                                ASM::mov_reg64_base32(buf, tmp_reg, base_offset + copied as i32);
+                        ASM::mov_reg64_base32(buf, tmp_reg, base_offset + copied as i32);
-                                ASM::mov_stack32_reg64(buf, stack_offset + copied as i32, tmp_reg);
+                        ASM::mov_stack32_reg64(buf, stack_offset + copied as i32, tmp_reg);
 
-                                copied += 8;
+                        copied += 8;
-                            }
-                        }
-
-                        if size - copied >= 4 {
-                            for _ in (0..(size - copied)).step_by(4) {
-                                ASM::mov_reg32_base32(buf, tmp_reg, base_offset + copied as i32);
-                                ASM::mov_stack32_reg32(buf, stack_offset + copied as i32, tmp_reg);
-
-                                copied += 4;
-                            }
-                        }
-
-                        if size - copied >= 2 {
-                            for _ in (0..(size - copied)).step_by(2) {
-                                ASM::mov_reg16_base32(buf, tmp_reg, base_offset + copied as i32);
-                                ASM::mov_stack32_reg16(buf, stack_offset + copied as i32, tmp_reg);
-
-                                copied += 2;
-                            }
-                        }
-
-                        if size - copied >= 1 {
-                            for _ in (0..(size - copied)).step_by(1) {
-                                ASM::mov_reg8_base32(buf, tmp_reg, base_offset + copied as i32);
-                                ASM::mov_stack32_reg8(buf, stack_offset + copied as i32, tmp_reg);
-
-                                copied += 1;
-                            }
-                        }
-
-                        self.tmp_stack_offset += size as i32;
-                    }
-                    _ => {
-                        todo!(
-                            "calling with arg type, {:?}",
-                            layout_interner.dbg(in_layout)
-                        );
                     }
                 }
+
+                if size - copied >= 4 {
+                    for _ in (0..(size - copied)).step_by(4) {
+                        ASM::mov_reg32_base32(buf, tmp_reg, base_offset + copied as i32);
+                        ASM::mov_stack32_reg32(buf, stack_offset + copied as i32, tmp_reg);
+
+                        copied += 4;
+                    }
+                }
+
+                if size - copied >= 2 {
+                    for _ in (0..(size - copied)).step_by(2) {
+                        ASM::mov_reg16_base32(buf, tmp_reg, base_offset + copied as i32);
+                        ASM::mov_stack32_reg16(buf, stack_offset + copied as i32, tmp_reg);
+
+                        copied += 2;
+                    }
+                }
+
+                if size - copied >= 1 {
+                    for _ in (0..(size - copied)).step_by(1) {
+                        ASM::mov_reg8_base32(buf, tmp_reg, base_offset + copied as i32);
+                        ASM::mov_stack32_reg8(buf, stack_offset + copied as i32, tmp_reg);
+
+                        copied += 1;
+                    }
+                }
+
+                self.tmp_stack_offset += size as i32;
+            }
+            _ => {
+                todo!(
+                    "calling with arg type, {:?}",
+                    layout_interner.dbg(in_layout)
+                );
             }
         }
     }
@@ -664,6 +656,7 @@ impl X64_64SystemVLoadArgs {
         let stack_size = layout_interner.stack_size(in_layout);
         match layout_interner.get(in_layout).repr {
             single_register_integers!() => self.load_arg_general(storage_manager, sym),
+            pointer_layouts!() => self.load_arg_general(storage_manager, sym),
             single_register_floats!() => self.load_arg_float(storage_manager, sym),
             _ if stack_size == 0 => {
                 storage_manager.no_data(&sym);
@@ -673,38 +666,32 @@ impl X64_64SystemVLoadArgs {
                 storage_manager.complex_stack_arg(&sym, self.argument_offset, stack_size);
                 self.argument_offset += stack_size as i32;
             }
-            other => match other {
+            LayoutRepr::LambdaSet(lambda_set) => self.load_arg(
-                LayoutRepr::Boxed(_) => {
+                storage_manager,
-                    // boxed layouts are pointers, which we treat as 64-bit integers
+                layout_interner,
-                    self.load_arg_general(storage_manager, sym)
+                sym,
-                }
+                lambda_set.runtime_representation(),
-                LayoutRepr::LambdaSet(lambda_set) => self.load_arg(
+            ),
-                    storage_manager,
+            LayoutRepr::Struct { .. } => {
-                    layout_interner,
+                // for now, just also store this on the stack
-                    sym,
+                storage_manager.complex_stack_arg(&sym, self.argument_offset, stack_size);
-                    lambda_set.runtime_representation(),
+                self.argument_offset += stack_size as i32;
-                ),
+            }
-                LayoutRepr::Struct { .. } => {
+            LayoutRepr::Builtin(Builtin::Int(IntWidth::U128 | IntWidth::I128)) => {
-                    // for now, just also store this on the stack
+                storage_manager.complex_stack_arg(&sym, self.argument_offset, stack_size);
-                    storage_manager.complex_stack_arg(&sym, self.argument_offset, stack_size);
+                self.argument_offset += stack_size as i32;
-                    self.argument_offset += stack_size as i32;
+            }
-                }
+            LayoutRepr::Union(UnionLayout::NonRecursive(_)) => {
-                LayoutRepr::Builtin(Builtin::Int(IntWidth::U128 | IntWidth::I128)) => {
+                // for now, just also store this on the stack
-                    storage_manager.complex_stack_arg(&sym, self.argument_offset, stack_size);
+                storage_manager.complex_stack_arg(&sym, self.argument_offset, stack_size);
-                    self.argument_offset += stack_size as i32;
+                self.argument_offset += stack_size as i32;
-                }
+            }
-                LayoutRepr::Union(UnionLayout::NonRecursive(_)) => {
+            _ => {
-                    // for now, just also store this on the stack
+                todo!(
-                    storage_manager.complex_stack_arg(&sym, self.argument_offset, stack_size);
+                    "Loading args with layout {:?}",
-                    self.argument_offset += stack_size as i32;
+                    layout_interner.dbg(in_layout)
-                }
+                );
-                _ => {
+            }
-                    todo!(
-                        "Loading args with layout {:?}",
-                        layout_interner.dbg(in_layout)
-                    );
-                }
-            },
         }
     }
 
@@ -1152,6 +1139,11 @@ where
 }
 
 impl Assembler<X86_64GeneralReg, X86_64FloatReg> for X86_64Assembler {
+    #[inline(always)]
+    fn base_pointer() -> X86_64GeneralReg {
+        X86_64GeneralReg::RBP
+    }
+
     // These functions should map to the raw assembly functions below.
     // In some cases, that means you can just directly call one of the direct assembly functions.
     #[inline(always)]
@@ -1756,7 +1748,7 @@ impl Assembler<X86_64GeneralReg, X86_64FloatReg> for X86_64Assembler {
     }
 
     #[inline(always)]
-    fn neq_reg64_reg64_reg64(
+    fn neq_reg_reg_reg(
         buf: &mut Vec<'_, u8>,
         register_width: RegisterWidth,
         dst: X86_64GeneralReg,

crates/compiler/gen_dev/src/lib.rs

@@ -798,7 +798,7 @@ trait Backend<'a> {
                 ..
             } => {
                 self.load_literal_symbols(arguments);
-                self.tag(sym, arguments, tag_layout, *tag_id);
+                self.tag(sym, arguments, tag_layout, *tag_id, None);
             }
             Expr::ExprBox { symbol: value } => {
                 let element_layout = match self.interner().get(*layout).repr {
@@ -807,7 +807,7 @@ trait Backend<'a> {
                 };
 
                 self.load_literal_symbols([*value].as_slice());
-                self.expr_box(*sym, *value, element_layout)
+                self.expr_box(*sym, *value, element_layout, None)
             }
             Expr::ExprUnbox { symbol: ptr } => {
                 let element_layout = *layout;
@@ -815,7 +815,60 @@ trait Backend<'a> {
                 self.load_literal_symbols([*ptr].as_slice());
                 self.expr_unbox(*sym, *ptr, element_layout)
             }
-            x => todo!("the expression, {:?}", x),
+            Expr::NullPointer => {
+                self.load_literal_i64(sym, 0);
+            }
+            Expr::Reuse {
+                tag_layout,
+                tag_id,
+                symbol: reused,
+                arguments,
+                ..
+            } => {
+                self.load_literal_symbols(arguments);
+                self.tag(sym, arguments, tag_layout, *tag_id, Some(*reused));
+            }
+            Expr::Reset { symbol, .. } => {
+                let layout = *self.layout_map().get(symbol).unwrap();
+
+                // Expand the Refcounting statement into more detailed IR with a function call
+                // If this layout requires a new RC proc, we get enough info to create a linker symbol
+                // for it. Here we don't create linker symbols at this time, but in Wasm backend, we do.
+                let (new_expr, new_specializations) = {
+                    let (module_id, layout_interner, interns, rc_proc_gen, _) =
+                        self.module_interns_helpers_mut();
+                    let ident_ids = interns.all_ident_ids.get_mut(&module_id).unwrap();
+
+                    rc_proc_gen.call_reset_refcount(ident_ids, layout_interner, layout, *symbol)
+                };
+
+                for spec in new_specializations.into_iter() {
+                    self.helper_proc_symbols_mut().push(spec);
+                }
+
+                self.build_expr(sym, &new_expr, &Layout::BOOL)
+            }
+            Expr::ResetRef { symbol, .. } => {
+                let layout = *self.layout_map().get(symbol).unwrap();
+
+                // Expand the Refcounting statement into more detailed IR with a function call
+                // If this layout requires a new RC proc, we get enough info to create a linker symbol
+                // for it. Here we don't create linker symbols at this time, but in Wasm backend, we do.
+                let (new_expr, new_specializations) = {
+                    let (module_id, layout_interner, interns, rc_proc_gen, _) =
+                        self.module_interns_helpers_mut();
+                    let ident_ids = interns.all_ident_ids.get_mut(&module_id).unwrap();
+
+                    rc_proc_gen.call_resetref_refcount(ident_ids, layout_interner, layout, *symbol)
+                };
+
+                for spec in new_specializations.into_iter() {
+                    self.helper_proc_symbols_mut().push(spec);
+                }
+
+                self.build_expr(sym, &new_expr, &Layout::BOOL)
+            }
+            Expr::RuntimeErrorFunction(_) => todo!(),
         }
     }
 
@@ -1068,13 +1121,12 @@ trait Backend<'a> {
             }
             LowLevel::Eq => {
                 debug_assert_eq!(2, args.len(), "Eq: expected to have exactly two argument");
-                debug_assert_eq!(
+                debug_assert!(
-                    arg_layouts[0], arg_layouts[1],
+                    self.interner().eq_repr(arg_layouts[0], arg_layouts[1],),
                     "Eq: expected all arguments of to have the same layout"
                 );
-                debug_assert_eq!(
+                debug_assert!(
-                    Layout::BOOL,
+                    self.interner().eq_repr(Layout::BOOL, *ret_layout,),
-                    *ret_layout,
                     "Eq: expected to have return layout of type Bool"
                 );
                 self.build_eq(sym, &args[0], &args[1], &arg_layouts[0])
@@ -1085,22 +1137,20 @@ trait Backend<'a> {
                     args.len(),
                     "NotEq: expected to have exactly two argument"
                 );
-                debug_assert_eq!(
+                debug_assert!(
-                    arg_layouts[0], arg_layouts[1],
+                    self.interner().eq_repr(arg_layouts[0], arg_layouts[1],),
                     "NotEq: expected all arguments of to have the same layout"
                 );
-                debug_assert_eq!(
+                debug_assert!(
-                    Layout::BOOL,
+                    self.interner().eq_repr(Layout::BOOL, *ret_layout,),
-                    *ret_layout,
                     "NotEq: expected to have return layout of type Bool"
                 );
                 self.build_neq(sym, &args[0], &args[1], &arg_layouts[0])
             }
             LowLevel::Not => {
                 debug_assert_eq!(1, args.len(), "Not: expected to have exactly one argument");
-                debug_assert_eq!(
+                debug_assert!(
-                    Layout::BOOL,
+                    self.interner().eq_repr(Layout::BOOL, *ret_layout,),
-                    *ret_layout,
                     "Not: expected to have return layout of type Bool"
                 );
                 self.build_not(sym, &args[0], &arg_layouts[0])
@@ -1111,13 +1161,12 @@ trait Backend<'a> {
                     args.len(),
                     "NumLt: expected to have exactly two argument"
                 );
-                debug_assert_eq!(
+                debug_assert!(
-                    arg_layouts[0], arg_layouts[1],
+                    self.interner().eq_repr(arg_layouts[0], arg_layouts[1],),
                     "NumLt: expected all arguments of to have the same layout"
                 );
-                debug_assert_eq!(
+                debug_assert!(
-                    Layout::BOOL,
+                    self.interner().eq_repr(Layout::BOOL, *ret_layout,),
-                    *ret_layout,
                     "NumLt: expected to have return layout of type Bool"
                 );
                 self.build_num_lt(sym, &args[0], &args[1], &arg_layouts[0])
@@ -1128,13 +1177,12 @@ trait Backend<'a> {
                     args.len(),
                     "NumGt: expected to have exactly two argument"
                 );
-                debug_assert_eq!(
+                debug_assert!(
-                    arg_layouts[0], arg_layouts[1],
+                    self.interner().eq_repr(arg_layouts[0], arg_layouts[1],),
                     "NumGt: expected all arguments of to have the same layout"
                 );
-                debug_assert_eq!(
+                debug_assert!(
-                    Layout::BOOL,
+                    self.interner().eq_repr(Layout::BOOL, *ret_layout,),
-                    *ret_layout,
                     "NumGt: expected to have return layout of type Bool"
                 );
                 self.build_num_gt(sym, &args[0], &args[1], &arg_layouts[0])
@@ -1159,9 +1207,8 @@ trait Backend<'a> {
                     "NumIsNan: expected to have exactly one argument"
                 );
 
-                debug_assert_eq!(
+                debug_assert!(
-                    Layout::BOOL,
+                    self.interner().eq_repr(Layout::BOOL, *ret_layout,),
-                    *ret_layout,
                     "NumIsNan: expected to have return layout of type Bool"
                 );
                 self.build_num_is_nan(sym, &args[0], &arg_layouts[0])
@@ -1173,9 +1220,8 @@ trait Backend<'a> {
                     "NumIsInfinite: expected to have exactly one argument"
                 );
 
-                debug_assert_eq!(
+                debug_assert!(
-                    Layout::BOOL,
+                    self.interner().eq_repr(Layout::BOOL, *ret_layout,),
-                    *ret_layout,
                     "NumIsInfinite: expected to have return layout of type Bool"
                 );
                 self.build_num_is_infinite(sym, &args[0], &arg_layouts[0])
@@ -1187,9 +1233,8 @@ trait Backend<'a> {
                     "NumIsFinite: expected to have exactly one argument"
                 );
 
-                debug_assert_eq!(
+                debug_assert!(
-                    Layout::BOOL,
+                    self.interner().eq_repr(Layout::BOOL, *ret_layout,),
-                    *ret_layout,
                     "NumIsFinite: expected to have return layout of type Bool"
                 );
                 self.build_num_is_finite(sym, &args[0], &arg_layouts[0])
@@ -1204,9 +1249,8 @@ trait Backend<'a> {
                     arg_layouts[0], arg_layouts[1],
                     "NumLte: expected all arguments of to have the same layout"
                 );
-                debug_assert_eq!(
+                debug_assert!(
-                    Layout::BOOL,
+                    self.interner().eq_repr(Layout::BOOL, *ret_layout,),
-                    *ret_layout,
                     "NumLte: expected to have return layout of type Bool"
                 );
                 self.build_num_lte(sym, &args[0], &args[1], &arg_layouts[0])
@@ -1221,9 +1265,8 @@ trait Backend<'a> {
                     arg_layouts[0], arg_layouts[1],
                     "NumGte: expected all arguments of to have the same layout"
                 );
-                debug_assert_eq!(
+                debug_assert!(
-                    Layout::BOOL,
+                    self.interner().eq_repr(Layout::BOOL, *ret_layout,),
-                    *ret_layout,
                     "NumGte: expected to have return layout of type Bool"
                 );
                 self.build_num_gte(sym, &args[0], &args[1], &arg_layouts[0])
@@ -1761,9 +1804,8 @@ trait Backend<'a> {
                     args.len(),
                     "NumIsZero: expected to have exactly one argument"
                 );
-                debug_assert_eq!(
+                debug_assert!(
-                    Layout::BOOL,
+                    self.interner().eq_repr(Layout::BOOL, *ret_layout,),
-                    *ret_layout,
                     "NumIsZero: expected to have return layout of type Bool"
                 );
 
@@ -2216,13 +2258,20 @@ trait Backend<'a> {
         args: &'a [Symbol],
         tag_layout: &UnionLayout<'a>,
         tag_id: TagIdIntType,
+        reuse: Option<Symbol>,
     );
 
     /// load a value from a pointer
     fn expr_unbox(&mut self, sym: Symbol, ptr: Symbol, element_layout: InLayout<'a>);
 
     /// store a refcounted value on the heap
-    fn expr_box(&mut self, sym: Symbol, value: Symbol, element_layout: InLayout<'a>);
+    fn expr_box(
+        &mut self,
+        sym: Symbol,
+        value: Symbol,
+        element_layout: InLayout<'a>,
+        reuse: Option<Symbol>,
+    );
 
     /// return_symbol moves a symbol to the correct return location for the backend and adds a jump to the end of the function.
     fn return_symbol(&mut self, sym: &Symbol, layout: &InLayout<'a>);

crates/compiler/gen_llvm/src/llvm/intrinsics.rs

@@ -7,11 +7,12 @@ use inkwell::{
 };
 use roc_builtins::{
     bitcode::{FloatWidth, IntWidth, IntrinsicName},
-    float_intrinsic, llvm_int_intrinsic,
+    llvm_int_intrinsic,
 };
 
 use super::build::{add_func, FunctionSpec};
 
+#[allow(dead_code)]
 fn add_float_intrinsic<'ctx, F>(
     ctx: &'ctx Context,
     module: &Module<'ctx>,
@@ -111,18 +112,6 @@ pub(crate) fn add_intrinsics<'ctx>(ctx: &'ctx Context, module: &Module<'ctx>) {
         i8_ptr_type.fn_type(&[], false),
     );
 
-    add_float_intrinsic(ctx, module, &LLVM_LOG, |t| t.fn_type(&[t.into()], false));
-    add_float_intrinsic(ctx, module, &LLVM_POW, |t| {
-        t.fn_type(&[t.into(), t.into()], false)
-    });
-    add_float_intrinsic(ctx, module, &LLVM_FABS, |t| t.fn_type(&[t.into()], false));
-    add_float_intrinsic(ctx, module, &LLVM_SIN, |t| t.fn_type(&[t.into()], false));
-    add_float_intrinsic(ctx, module, &LLVM_COS, |t| t.fn_type(&[t.into()], false));
-    add_float_intrinsic(ctx, module, &LLVM_CEILING, |t| {
-        t.fn_type(&[t.into()], false)
-    });
-    add_float_intrinsic(ctx, module, &LLVM_FLOOR, |t| t.fn_type(&[t.into()], false));
-
     add_int_intrinsic(ctx, module, &LLVM_ADD_WITH_OVERFLOW, |t| {
         let fields = [t.into(), i1_type.into()];
         ctx.struct_type(&fields, false)
@@ -150,17 +139,6 @@ pub(crate) fn add_intrinsics<'ctx>(ctx: &'ctx Context, module: &Module<'ctx>) {
     });
 }
 
-pub const LLVM_POW: IntrinsicName = float_intrinsic!("llvm.pow");
-pub const LLVM_FABS: IntrinsicName = float_intrinsic!("llvm.fabs");
-pub static LLVM_SQRT: IntrinsicName = float_intrinsic!("llvm.sqrt");
-pub static LLVM_LOG: IntrinsicName = float_intrinsic!("llvm.log");
-
-pub static LLVM_SIN: IntrinsicName = float_intrinsic!("llvm.sin");
-pub static LLVM_COS: IntrinsicName = float_intrinsic!("llvm.cos");
-pub static LLVM_CEILING: IntrinsicName = float_intrinsic!("llvm.ceil");
-pub static LLVM_FLOOR: IntrinsicName = float_intrinsic!("llvm.floor");
-pub static LLVM_ROUND: IntrinsicName = float_intrinsic!("llvm.round");
-
 pub static LLVM_MEMSET_I64: &str = "llvm.memset.p0i8.i64";
 pub static LLVM_MEMSET_I32: &str = "llvm.memset.p0i8.i32";
 

crates/compiler/gen_llvm/src/llvm/lowlevel.rs

@@ -41,9 +41,13 @@ use crate::llvm::{
         self, basic_type_from_layout, zig_num_parse_result_type, zig_to_int_checked_result_type,
     },
     intrinsics::{
-        LLVM_ADD_SATURATED, LLVM_ADD_WITH_OVERFLOW, LLVM_CEILING, LLVM_COS, LLVM_FABS, LLVM_FLOOR,
+        // These instrinsics do not generate calls to libc and are safe to keep.
-        LLVM_LOG, LLVM_MUL_WITH_OVERFLOW, LLVM_POW, LLVM_ROUND, LLVM_SIN, LLVM_SQRT,
+        // If we find that any of them generate calls to libc on some platforms, we need to define them as zig bitcode.
-        LLVM_SUB_SATURATED, LLVM_SUB_WITH_OVERFLOW,
+        LLVM_ADD_SATURATED,
+        LLVM_ADD_WITH_OVERFLOW,
+        LLVM_MUL_WITH_OVERFLOW,
+        LLVM_SUB_SATURATED,
+        LLVM_SUB_WITH_OVERFLOW,
     },
     refcounting::PointerToRefcount,
 };
@@ -1704,7 +1708,11 @@ fn build_float_binop<'ctx>(
         NumLt => bd.build_float_compare(OLT, lhs, rhs, "float_lt").into(),
         NumLte => bd.build_float_compare(OLE, lhs, rhs, "float_lte").into(),
         NumDivFrac => bd.build_float_div(lhs, rhs, "div_float").into(),
-        NumPow => env.call_intrinsic(&LLVM_POW[float_width], &[lhs.into(), rhs.into()]),
+        NumPow => call_bitcode_fn(
+            env,
+            &[lhs.into(), rhs.into()],
+            &bitcode::NUM_POW[float_width],
+        ),
         _ => {
             unreachable!("Unrecognized int binary operation: {:?}", op);
         }
@@ -2316,9 +2324,9 @@ fn build_float_unary_op<'a, 'ctx>(
     // TODO: Handle different sized floats
     match op {
         NumNeg => bd.build_float_neg(arg, "negate_float").into(),
-        NumAbs => env.call_intrinsic(&LLVM_FABS[float_width], &[arg.into()]),
+        NumAbs => call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_FABS[float_width]),
-        NumSqrtUnchecked => env.call_intrinsic(&LLVM_SQRT[float_width], &[arg.into()]),
+        NumSqrtUnchecked => call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_SQRT[float_width]),
-        NumLogUnchecked => env.call_intrinsic(&LLVM_LOG[float_width], &[arg.into()]),
+        NumLogUnchecked => call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_LOG[float_width]),
         NumToFrac => {
             let return_width = match layout_interner.get(layout).repr {
                 LayoutRepr::Builtin(Builtin::Float(return_width)) => return_width,
@@ -2342,64 +2350,46 @@ fn build_float_unary_op<'a, 'ctx>(
             }
         }
         NumCeiling => {
-            let (return_signed, return_type) = match layout_interner.get(layout).repr {
+            let int_width = match layout_interner.get(layout).repr {
-                LayoutRepr::Builtin(Builtin::Int(int_width)) => (
+                LayoutRepr::Builtin(Builtin::Int(int_width)) => int_width,
-                    int_width.is_signed(),
-                    convert::int_type_from_int_width(env, int_width),
-                ),
                 _ => internal_error!("Ceiling return layout is not int: {:?}", layout),
             };
-            let opcode = if return_signed {
+            match float_width {
-                InstructionOpcode::FPToSI
+                FloatWidth::F32 => {
-            } else {
+                    call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_CEILING_F32[int_width])
-                InstructionOpcode::FPToUI
+                }
-            };
+                FloatWidth::F64 => {
-            env.builder.build_cast(
+                    call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_CEILING_F64[int_width])
-                opcode,
+                }
-                env.call_intrinsic(&LLVM_CEILING[float_width], &[arg.into()]),
+            }
-                return_type,
-                "num_ceiling",
-            )
         }
         NumFloor => {
-            let (return_signed, return_type) = match layout_interner.get(layout).repr {
+            let int_width = match layout_interner.get(layout).repr {
-                LayoutRepr::Builtin(Builtin::Int(int_width)) => (
+                LayoutRepr::Builtin(Builtin::Int(int_width)) => int_width,
-                    int_width.is_signed(),
+                _ => internal_error!("Floor return layout is not int: {:?}", layout),
-                    convert::int_type_from_int_width(env, int_width),
-                ),
-                _ => internal_error!("Ceiling return layout is not int: {:?}", layout),
             };
-            let opcode = if return_signed {
+            match float_width {
-                InstructionOpcode::FPToSI
+                FloatWidth::F32 => {
-            } else {
+                    call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_FLOOR_F32[int_width])
-                InstructionOpcode::FPToUI
+                }
-            };
+                FloatWidth::F64 => {
-            env.builder.build_cast(
+                    call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_FLOOR_F64[int_width])
-                opcode,
+                }
-                env.call_intrinsic(&LLVM_FLOOR[float_width], &[arg.into()]),
+            }
-                return_type,
-                "num_floor",
-            )
         }
         NumRound => {
-            let (return_signed, return_type) = match layout_interner.get(layout).repr {
+            let int_width = match layout_interner.get(layout).repr {
-                LayoutRepr::Builtin(Builtin::Int(int_width)) => (
+                LayoutRepr::Builtin(Builtin::Int(int_width)) => int_width,
-                    int_width.is_signed(),
+                _ => internal_error!("Round return layout is not int: {:?}", layout),
-                    convert::int_type_from_int_width(env, int_width),
-                ),
-                _ => internal_error!("Ceiling return layout is not int: {:?}", layout),
             };
-            let opcode = if return_signed {
+            match float_width {
-                InstructionOpcode::FPToSI
+                FloatWidth::F32 => {
-            } else {
+                    call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_ROUND_F32[int_width])
-                InstructionOpcode::FPToUI
+                }
-            };
+                FloatWidth::F64 => {
-            env.builder.build_cast(
+                    call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_ROUND_F64[int_width])
-                opcode,
+                }
-                env.call_intrinsic(&LLVM_ROUND[float_width], &[arg.into()]),
+            }
-                return_type,
-                "num_round",
-            )
         }
         NumIsNan => call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_IS_NAN[float_width]),
         NumIsInfinite => {
@@ -2408,8 +2398,8 @@ fn build_float_unary_op<'a, 'ctx>(
         NumIsFinite => call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_IS_FINITE[float_width]),
 
         // trigonometry
-        NumSin => env.call_intrinsic(&LLVM_SIN[float_width], &[arg.into()]),
+        NumSin => call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_SIN[float_width]),
-        NumCos => env.call_intrinsic(&LLVM_COS[float_width], &[arg.into()]),
+        NumCos => call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_COS[float_width]),
 
         NumAtan => call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_ATAN[float_width]),
         NumAcos => call_bitcode_fn(env, &[arg.into()], &bitcode::NUM_ACOS[float_width]),

crates/compiler/load_internal/src/file.rs

@@ -32,7 +32,7 @@ use roc_module::symbol::{
 };
 use roc_mono::ir::{
     CapturedSymbols, ExternalSpecializations, GlueLayouts, LambdaSetId, PartialProc, Proc,
-    ProcLayout, Procs, ProcsBase, UpdateModeIds,
+    ProcLayout, Procs, ProcsBase, UpdateModeIds, UsageTrackingMap,
 };
 use roc_mono::layout::LayoutInterner;
 use roc_mono::layout::{
@@ -3115,7 +3115,6 @@ fn update<'a>(
                         &mut layout_interner,
                         module_id,
                         ident_ids,
-                        state.target_info,
                         &mut state.procedures,
                     );
 
@@ -5783,6 +5782,7 @@ fn make_specializations<'a>(
         abilities: AbilitiesView::World(&world_abilities),
         exposed_by_module,
         derived_module: &derived_module,
+        struct_indexing: UsageTrackingMap::default(),
     };
 
     let mut procs = Procs::new_in(arena);
@@ -5883,6 +5883,7 @@ fn build_pending_specializations<'a>(
         abilities: AbilitiesView::Module(&abilities_store),
         exposed_by_module,
         derived_module: &derived_module,
+        struct_indexing: UsageTrackingMap::default(),
     };
 
     let layout_cache_snapshot = layout_cache.snapshot();
@@ -6364,6 +6365,7 @@ fn load_derived_partial_procs<'a>(
             abilities: AbilitiesView::World(world_abilities),
             exposed_by_module,
             derived_module,
+            struct_indexing: UsageTrackingMap::default(),
         };
 
         let partial_proc = match derived_expr {

crates/compiler/mono/src/drop_specialization.rs

@@ -15,11 +15,10 @@ use bumpalo::collections::CollectIn;
 
 use roc_module::low_level::LowLevel;
 use roc_module::symbol::{IdentIds, ModuleId, Symbol};
-use roc_target::TargetInfo;
 
 use crate::ir::{
-    BranchInfo, Call, CallType, Expr, JoinPointId, Literal, ModifyRc, Proc, ProcLayout, Stmt,
+    BranchInfo, Call, CallType, Expr, JoinPointId, ListLiteralElement, Literal, ModifyRc, Proc,
-    UpdateModeId,
+    ProcLayout, Stmt, UpdateModeId,
 };
 use crate::layout::{
     Builtin, InLayout, Layout, LayoutInterner, LayoutRepr, STLayoutInterner, UnionLayout,
@@ -27,7 +26,7 @@ use crate::layout::{
 
 use bumpalo::Bump;
 
-use roc_collections::{MutMap, MutSet};
+use roc_collections::MutMap;
 
 /**
 Try to find increments of symbols followed by decrements of the symbol they were indexed out of (their parent).
@@ -38,12 +37,10 @@ pub fn specialize_drops<'a, 'i>(
     layout_interner: &'i mut STLayoutInterner<'a>,
     home: ModuleId,
     ident_ids: &'i mut IdentIds,
-    target_info: TargetInfo,
     procs: &mut MutMap<(Symbol, ProcLayout<'a>), Proc<'a>>,
 ) {
     for ((_symbol, proc_layout), proc) in procs.iter_mut() {
-        let mut environment =
+        let mut environment = DropSpecializationEnvironment::new(arena, home, proc_layout.result);
-            DropSpecializationEnvironment::new(arena, home, proc_layout.result, target_info);
         specialize_drops_proc(arena, layout_interner, ident_ids, &mut environment, proc);
     }
 }
@@ -104,7 +101,7 @@ fn specialize_drops_stmt<'a, 'i>(
                                 _ => unreachable!("List get should have two arguments"),
                             };
 
-                            environment.add_list_child(*structure, *binding, index);
+                            environment.add_list_child_symbol(*structure, *binding, index);
 
                             alloc_let_with_continuation!(environment)
                         }
@@ -114,9 +111,18 @@ fn specialize_drops_stmt<'a, 'i>(
                             RC::NoRc => alloc_let_with_continuation!(environment),
                             // We probably should not pass the increments to the continuation.
                             RC::Rc | RC::Uknown => {
-                                let mut new_environment = environment.clone_without_incremented();
+                                let incremented_symbols = environment.incremented_symbols.drain();
 
-                                alloc_let_with_continuation!(&mut new_environment)
+                                let new_stmt = alloc_let_with_continuation!(environment);
+
+                                // The new_environment might have inserted increments that were set to 0 before. We need to add th
+                                for (symbol, increment) in incremented_symbols.map.into_iter() {
+                                    environment
+                                        .incremented_symbols
+                                        .insert_count(symbol, increment);
+                                }
+
+                                new_stmt
                             }
                         },
                         _ => {
@@ -127,16 +133,62 @@ fn specialize_drops_stmt<'a, 'i>(
                             // the parent might be deallocated before the function can use it.
                             // Thus forget everything about any increments.
 
-                            let mut new_environment = environment.clone_without_incremented();
+                            let incremented_symbols = environment.incremented_symbols.drain();
 
-                            alloc_let_with_continuation!(&mut new_environment)
+                            let new_stmt = alloc_let_with_continuation!(environment);
+
+                            // The new_environment might have inserted increments that were set to 0 before. We need to add th
+                            for (symbol, increment) in incremented_symbols.map.into_iter() {
+                                environment
+                                    .incremented_symbols
+                                    .insert_count(symbol, increment);
+                            }
+
+                            new_stmt
                         }
                     }
                 }
 
-                Expr::Tag { tag_id, .. } => {
+                Expr::Tag {
+                    tag_id,
+                    arguments: children,
+                    ..
+                } => {
                     environment.symbol_tag.insert(*binding, *tag_id);
 
+                    for (index, child) in children.iter().enumerate() {
+                        environment.add_union_child(*binding, *child, *tag_id, index as u64);
+                    }
+
+                    alloc_let_with_continuation!(environment)
+                }
+                Expr::Struct(children) => {
+                    for (index, child) in children.iter().enumerate() {
+                        environment.add_struct_child(*binding, *child, index as u64);
+                    }
+
+                    alloc_let_with_continuation!(environment)
+                }
+                Expr::ExprBox { symbol: child } => {
+                    environment.add_box_child(*binding, *child);
+
+                    alloc_let_with_continuation!(environment)
+                }
+                Expr::Array {
+                    elems: children, ..
+                } => {
+                    for (index, child) in
+                        children
+                            .iter()
+                            .enumerate()
+                            .filter_map(|(index, child)| match child {
+                                ListLiteralElement::Literal(_) => None,
+                                ListLiteralElement::Symbol(s) => Some((index, s)),
+                            })
+                    {
+                        environment.add_list_child(*binding, *child, index as u64);
+                    }
+
                     alloc_let_with_continuation!(environment)
                 }
                 Expr::StructAtIndex {
@@ -188,13 +240,10 @@ fn specialize_drops_stmt<'a, 'i>(
                     }
                     alloc_let_with_continuation!(environment)
                 }
-                Expr::Struct(_)
+                Expr::RuntimeErrorFunction(_)
-                | Expr::RuntimeErrorFunction(_)
-                | Expr::ExprBox { .. }
                 | Expr::NullPointer
                 | Expr::GetTagId { .. }
-                | Expr::EmptyArray
+                | Expr::EmptyArray => {
-                | Expr::Array { .. } => {
                     // Does nothing relevant to drop specialization. So we can just continue.
                     alloc_let_with_continuation!(environment)
                 }
@@ -283,10 +332,12 @@ fn specialize_drops_stmt<'a, 'i>(
                 };
 
                 // Find the lowest symbol count for each symbol in each branch, and update the environment to match.
-                for (symbol, count) in environment.incremented_symbols.iter_mut() {
+                for (symbol, count) in environment.incremented_symbols.map.iter_mut() {
                     let consumed = branch_envs
                         .iter()
-                        .map(|branch_env| branch_env.incremented_symbols.get(symbol).unwrap_or(&0))
+                        .map(|branch_env| {
+                            branch_env.incremented_symbols.map.get(symbol).unwrap_or(&0)
+                        })
                         .min()
                         .unwrap();
 
@@ -300,10 +351,14 @@ fn specialize_drops_stmt<'a, 'i>(
                     let symbol_differences =
                         environment
                             .incremented_symbols
+                            .map
                             .iter()
                             .filter_map(|(symbol, count)| {
-                                let branch_count =
+                                let branch_count = $branch_env
-                                    $branch_env.incremented_symbols.get(symbol).unwrap_or(&0);
+                                    .incremented_symbols
+                                    .map
+                                    .get(symbol)
+                                    .unwrap_or(&0);
 
                                 match branch_count - count {
                                     0 => None,
@@ -338,11 +393,6 @@ fn specialize_drops_stmt<'a, 'i>(
                 (info.clone(), new_branch)
             };
 
-            // Remove all 0 counts as cleanup.
-            environment
-                .incremented_symbols
-                .retain(|_, count| *count > 0);
-
             arena.alloc(Stmt::Switch {
                 cond_symbol: *cond_symbol,
                 cond_layout: *cond_layout,
@@ -354,10 +404,12 @@ fn specialize_drops_stmt<'a, 'i>(
         Stmt::Ret(symbol) => arena.alloc(Stmt::Ret(*symbol)),
         Stmt::Refcounting(rc, continuation) => match rc {
             ModifyRc::Inc(symbol, count) => {
-                let any = environment.any_incremented(symbol);
+                let inc_before = environment.incremented_symbols.contains(symbol);
 
                 // Add a symbol for every increment performed.
-                environment.add_incremented(*symbol, *count);
+                environment
+                    .incremented_symbols
+                    .insert_count(*symbol, *count);
 
                 let new_continuation = specialize_drops_stmt(
                     arena,
@@ -367,12 +419,17 @@ fn specialize_drops_stmt<'a, 'i>(
                     continuation,
                 );
 
-                if any {
+                if inc_before {
                     // There were increments before this one, best to let the first one do the increments.
                     // Or there are no increments left, so we can just continue.
                     new_continuation
                 } else {
-                    match environment.get_incremented(symbol) {
+                    match environment
+                        .incremented_symbols
+                        .map
+                        .remove(symbol)
+                        .unwrap_or(0)
+                    {
                         // This is the first increment, but all increments are consumed. So don't insert any.
                         0 => new_continuation,
                         // We still need to do some increments.
@@ -393,7 +450,7 @@ fn specialize_drops_stmt<'a, 'i>(
                 // dec a
                 // dec b
 
-                if environment.pop_incremented(symbol) {
+                if environment.incremented_symbols.pop(symbol) {
                     // This decremented symbol was incremented before, so we can remove it.
                     specialize_drops_stmt(
                         arena,
@@ -411,10 +468,10 @@ fn specialize_drops_stmt<'a, 'i>(
                     // As a might get dropped as a result of the decrement of b.
                     let mut incremented_children = {
                         let mut todo_children = bumpalo::vec![in arena; *symbol];
-                        let mut incremented_children = MutSet::default();
+                        let mut incremented_children = CountingMap::new();
 
                         while let Some(child) = todo_children.pop() {
-                            if environment.pop_incremented(&child) {
+                            if environment.incremented_symbols.pop(&child) {
                                 incremented_children.insert(child);
                             } else {
                                 todo_children.extend(environment.get_children(&child));
@@ -485,8 +542,10 @@ fn specialize_drops_stmt<'a, 'i>(
                     };
 
                     // Add back the increments for the children to the environment.
-                    for child_symbol in incremented_children.iter() {
+                    for (child_symbol, symbol_count) in incremented_children.map.into_iter() {
-                        environment.add_incremented(*child_symbol, 1)
+                        environment
+                            .incremented_symbols
+                            .insert_count(child_symbol, symbol_count)
                     }
 
                     updated_stmt
@@ -565,7 +624,8 @@ fn specialize_drops_stmt<'a, 'i>(
             body,
             remainder,
         } => {
-            let mut new_environment = environment.clone_without_incremented();
+            let mut new_environment = environment.clone();
+            new_environment.incremented_symbols.clear();
 
             for param in parameters.iter() {
                 new_environment.add_symbol_layout(param.symbol, param.layout);
@@ -604,7 +664,7 @@ fn specialize_struct<'a, 'i>(
     environment: &mut DropSpecializationEnvironment<'a>,
     symbol: &Symbol,
     struct_layout: &'a [InLayout],
-    incremented_children: &mut MutSet<Child>,
+    incremented_children: &mut CountingMap<Child>,
     continuation: &'a Stmt<'a>,
 ) -> &'a Stmt<'a> {
     match environment.struct_children.get(symbol) {
@@ -620,7 +680,7 @@ fn specialize_struct<'a, 'i>(
 
             for (index, _layout) in struct_layout.iter().enumerate() {
                 for (child, _i) in children_clone.iter().filter(|(_, i)| *i == index as u64) {
-                    let removed = incremented_children.remove(child);
+                    let removed = incremented_children.pop(child);
                     index_symbols.insert(index, (*child, removed));
 
                     if removed {
@@ -693,7 +753,7 @@ fn specialize_union<'a, 'i>(
     environment: &mut DropSpecializationEnvironment<'a>,
     symbol: &Symbol,
     union_layout: UnionLayout<'a>,
-    incremented_children: &mut MutSet<Child>,
+    incremented_children: &mut CountingMap<Child>,
     continuation: &'a Stmt<'a>,
 ) -> &'a Stmt<'a> {
     let current_tag = environment.symbol_tag.get(symbol).copied();
@@ -736,7 +796,7 @@ fn specialize_union<'a, 'i>(
                         {
                             debug_assert_eq!(tag, *t);
 
-                            let removed = incremented_children.remove(child);
+                            let removed = incremented_children.pop(child);
                             index_symbols.insert(index, (*child, removed));
 
                             if removed {
@@ -898,14 +958,14 @@ fn specialize_boxed<'a, 'i>(
     layout_interner: &'i mut STLayoutInterner<'a>,
     ident_ids: &'i mut IdentIds,
     environment: &mut DropSpecializationEnvironment<'a>,
-    incremented_children: &mut MutSet<Child>,
+    incremented_children: &mut CountingMap<Child>,
     symbol: &Symbol,
     continuation: &'a Stmt<'a>,
 ) -> &'a Stmt<'a> {
-    let removed = match incremented_children.iter().next() {
+    let removed = match incremented_children.map.iter().next() {
-        Some(s) => {
+        Some((s, _)) => {
             let s = *s;
-            incremented_children.remove(&s);
+            incremented_children.pop(&s);
             Some(s)
         }
         None => None,
@@ -924,23 +984,20 @@ fn specialize_boxed<'a, 'i>(
                 *symbol,
                 // If the symbol is unique:
                 // - free the box
-                |_, _, _| {
+                |_, _, continuation| {
                     arena.alloc(Stmt::Refcounting(
                         // TODO can be replaced by free if ever added to the IR.
                         ModifyRc::DecRef(*symbol),
-                        new_continuation,
+                        continuation,
                     ))
                 },
                 // If the symbol is not unique:
                 // - increment the child
                 // - decref the box
-                |_, _, _| {
+                |_, _, continuation| {
                     arena.alloc(Stmt::Refcounting(
                         ModifyRc::Inc(s, 1),
-                        arena.alloc(Stmt::Refcounting(
+                        arena.alloc(Stmt::Refcounting(ModifyRc::DecRef(*symbol), continuation)),
-                            ModifyRc::DecRef(*symbol),
-                            new_continuation,
-                        )),
                     ))
                 },
                 new_continuation,
@@ -958,7 +1015,7 @@ fn specialize_list<'a, 'i>(
     layout_interner: &'i mut STLayoutInterner<'a>,
     ident_ids: &'i mut IdentIds,
     environment: &mut DropSpecializationEnvironment<'a>,
-    incremented_children: &mut MutSet<Child>,
+    incremented_children: &mut CountingMap<Child>,
     symbol: &Symbol,
     item_layout: InLayout,
     continuation: &'a Stmt<'a>,
@@ -993,7 +1050,7 @@ fn specialize_list<'a, 'i>(
                         for (child, i) in children_clone.iter().filter(|(_child, i)| *i == index) {
                             debug_assert!(length > *i);
 
-                            let removed = incremented_children.remove(child);
+                            let removed = incremented_children.pop(child);
                             index_symbols.insert(index, (*child, removed));
 
                             if removed {
@@ -1214,7 +1271,6 @@ struct DropSpecializationEnvironment<'a> {
     arena: &'a Bump,
     home: ModuleId,
     layout: InLayout<'a>,
-    target_info: TargetInfo,
 
     symbol_layouts: MutMap<Symbol, InLayout<'a>>,
 
@@ -1231,7 +1287,7 @@ struct DropSpecializationEnvironment<'a> {
     list_children: MutMap<Parent, Vec<'a, (Child, Index)>>,
 
     // Keeps track of all incremented symbols.
-    incremented_symbols: MutMap<Symbol, u64>,
+    incremented_symbols: CountingMap<Symbol>,
 
     // Map containing the current known tag of a layout.
     symbol_tag: MutMap<Symbol, Tag>,
@@ -1244,42 +1300,23 @@ struct DropSpecializationEnvironment<'a> {
 }
 
 impl<'a> DropSpecializationEnvironment<'a> {
-    fn new(arena: &'a Bump, home: ModuleId, layout: InLayout<'a>, target_info: TargetInfo) -> Self {
+    fn new(arena: &'a Bump, home: ModuleId, layout: InLayout<'a>) -> Self {
         Self {
             arena,
             home,
             layout,
-            target_info,
             symbol_layouts: MutMap::default(),
             struct_children: MutMap::default(),
             union_children: MutMap::default(),
             box_children: MutMap::default(),
             list_children: MutMap::default(),
-            incremented_symbols: MutMap::default(),
+            incremented_symbols: CountingMap::new(),
             symbol_tag: MutMap::default(),
             symbol_index: MutMap::default(),
             list_length: MutMap::default(),
         }
     }
 
-    fn clone_without_incremented(&self) -> Self {
-        Self {
-            arena: self.arena,
-            home: self.home,
-            layout: self.layout,
-            target_info: self.target_info,
-            symbol_layouts: self.symbol_layouts.clone(),
-            struct_children: self.struct_children.clone(),
-            union_children: self.union_children.clone(),
-            box_children: self.box_children.clone(),
-            list_children: self.list_children.clone(),
-            incremented_symbols: MutMap::default(),
-            symbol_tag: self.symbol_tag.clone(),
-            symbol_index: self.symbol_index.clone(),
-            list_length: self.list_length.clone(),
-        }
-    }
-
     fn create_symbol<'i>(&self, ident_ids: &'i mut IdentIds, debug_name: &str) -> Symbol {
         let ident_id = ident_ids.add_str(debug_name);
         Symbol::new(self.home, ident_id)
@@ -1316,12 +1353,16 @@ impl<'a> DropSpecializationEnvironment<'a> {
             .push(child);
     }
 
-    fn add_list_child(&mut self, parent: Parent, child: Child, index: &Symbol) {
+    fn add_list_child(&mut self, parent: Parent, child: Child, index: u64) {
+        self.list_children
+            .entry(parent)
+            .or_insert_with(|| Vec::new_in(self.arena))
+            .push((child, index));
+    }
+
+    fn add_list_child_symbol(&mut self, parent: Parent, child: Child, index: &Symbol) {
         if let Some(index) = self.symbol_index.get(index) {
-            self.list_children
+            self.add_list_child(parent, child, *index)
-                .entry(parent)
-                .or_insert_with(|| Vec::new_in(self.arena))
-                .push((child, *index));
         }
     }
 
@@ -1346,39 +1387,6 @@ impl<'a> DropSpecializationEnvironment<'a> {
 
         res
     }
-
-    /**
-    Add a symbol for every increment performed.
-     */
-    fn add_incremented(&mut self, symbol: Symbol, count: u64) {
-        self.incremented_symbols
-            .entry(symbol)
-            .and_modify(|c| *c += count)
-            .or_insert(count);
-    }
-
-    fn any_incremented(&self, symbol: &Symbol) -> bool {
-        self.incremented_symbols.contains_key(symbol)
-    }
-
-    /**
-    Return the amount of times a symbol still has to be incremented.
-    Accounting for later consumtion and removal of the increment.
-    */
-    fn get_incremented(&mut self, symbol: &Symbol) -> u64 {
-        self.incremented_symbols.remove(symbol).unwrap_or(0)
-    }
-
-    fn pop_incremented(&mut self, symbol: &Symbol) -> bool {
-        match self.incremented_symbols.get_mut(symbol) {
-            Some(0) => false,
-            Some(c) => {
-                *c -= 1;
-                true
-            }
-            None => false,
-        }
-    }
 }
 
 /**
@@ -1490,3 +1498,59 @@ fn low_level_no_rc(lowlevel: &LowLevel) -> RC {
         }
     }
 }
+
+/// Map that contains a count for each key.
+/// Keys with a count of 0 are kept around, so that it can be seen that they were once present.
+#[derive(Clone)]
+struct CountingMap<K> {
+    map: MutMap<K, u64>,
+}
+
+impl<K> CountingMap<K>
+where
+    K: Eq + std::hash::Hash + Clone,
+{
+    fn new() -> Self {
+        Self {
+            map: MutMap::default(),
+        }
+    }
+
+    fn insert(&mut self, key: K) {
+        self.insert_count(key, 1);
+    }
+
+    fn insert_count(&mut self, key: K, count: u64) {
+        self.map
+            .entry(key)
+            .and_modify(|c| *c += count)
+            .or_insert(count);
+    }
+
+    fn pop(&mut self, key: &K) -> bool {
+        match self.map.get_mut(key) {
+            Some(0) => false,
+            Some(c) => {
+                *c -= 1;
+                true
+            }
+            None => false,
+        }
+    }
+
+    fn contains(&self, symbol: &K) -> bool {
+        self.map.contains_key(symbol)
+    }
+
+    fn drain(&mut self) -> Self {
+        let res = self.clone();
+        for (_, v) in self.map.iter_mut() {
+            *v = 0;
+        }
+        res
+    }
+
+    fn clear(&mut self) {
+        self.map.clear();
+    }
+}

crates/compiler/mono/src/ir.rs

@@ -1386,6 +1386,7 @@ pub struct Env<'a, 'i> {
     pub abilities: AbilitiesView<'i>,
     pub exposed_by_module: &'i ExposedByModule,
     pub derived_module: &'i SharedDerivedModule,
+    pub struct_indexing: UsageTrackingMap<(Symbol, u64), Symbol>,
 }
 
 impl<'a, 'i> Env<'a, 'i> {
@@ -4225,6 +4226,7 @@ pub fn with_hole<'a>(
             // If this symbol is a raw value, find the real name we gave to its specialized usage.
             if let ReuseSymbol::Value(_symbol) = can_reuse_symbol(
                 env,
+                layout_cache,
                 procs,
                 &roc_can::expr::Expr::Var(symbol, variable),
                 variable,
@@ -4324,7 +4326,7 @@ pub fn with_hole<'a>(
         OpaqueRef { argument, .. } => {
             let (arg_var, loc_arg_expr) = *argument;
 
-            match can_reuse_symbol(env, procs, &loc_arg_expr.value, arg_var) {
+            match can_reuse_symbol(env, layout_cache, procs, &loc_arg_expr.value, arg_var) {
                 // Opaques decay to their argument.
                 ReuseSymbol::Value(symbol) => {
                     let real_name = procs.get_or_insert_symbol_specialization(
@@ -4909,20 +4911,19 @@ pub fn with_hole<'a>(
         RecordUpdate {
             record_var,
             symbol: structure,
-            updates,
+            ref updates,
             ..
         } => {
             use FieldType::*;
 
             enum FieldType<'a> {
-                CopyExisting(u64),
+                CopyExisting,
                 UpdateExisting(&'a roc_can::expr::Field),
             }
 
             // Strategy: turn a record update into the creation of a new record.
             // This has the benefit that we don't need to do anything special for reference
             // counting
-
             let sorted_fields_result = {
                 let mut layout_env = layout::Env::from_components(
                     layout_cache,
@@ -4938,43 +4939,56 @@ pub fn with_hole<'a>(
                 Err(_) => return runtime_error(env, "Can't update record with improper layout"),
             };
 
-            let mut field_layouts = Vec::with_capacity_in(sorted_fields.len(), env.arena);
+            let single_field_struct = sorted_fields.len() == 1;
 
-            let mut symbols = Vec::with_capacity_in(sorted_fields.len(), env.arena);
+            // The struct indexing generated by the current context
+            let mut current_struct_indexing = Vec::with_capacity_in(sorted_fields.len(), env.arena);
+            // The symbols that are used to create the new struct
+            let mut new_struct_symbols = Vec::with_capacity_in(sorted_fields.len(), env.arena);
+            // Information about the fields that are being updated
             let mut fields = Vec::with_capacity_in(sorted_fields.len(), env.arena);
+            let mut index = 0;
+            for (label, _, opt_field_layout) in sorted_fields.iter() {
+                let record_index = (structure, index);
 
-            let mut current = 0;
-            for (label, _, opt_field_layout) in sorted_fields.into_iter() {
                 match opt_field_layout {
                     Err(_) => {
-                        debug_assert!(!updates.contains_key(&label));
+                        debug_assert!(!updates.contains_key(label));
                         // this was an optional field, and now does not exist!
-                        // do not increment `current`!
+                        // do not increment `index`!
                     }
-                    Ok(field_layout) => {
+                    Ok(_field_layout) => {
-                        field_layouts.push(field_layout);
+                        current_struct_indexing.push(record_index);
 
-                        if let Some(field) = updates.get(&label) {
+                        // The struct with a single field is optimized in such a way that replacing later indexing will cause an incorrect IR.
-                            let field_symbol = possible_reuse_symbol_or_specialize(
+                        // Thus, only insert these struct_indices if there is more than one field in the struct.
+                        if !single_field_struct {
+                            let original_struct_symbol = env.unique_symbol();
+                            env.struct_indexing
+                                .insert(record_index, original_struct_symbol);
+                        }
+                        if let Some(field) = updates.get(label) {
+                            let new_struct_symbol = possible_reuse_symbol_or_specialize(
                                 env,
                                 procs,
                                 layout_cache,
                                 &field.loc_expr.value,
                                 field.var,
                             );
-
+                            new_struct_symbols.push(new_struct_symbol);
                             fields.push(UpdateExisting(field));
-                            symbols.push(field_symbol);
                         } else {
-                            fields.push(CopyExisting(current));
+                            new_struct_symbols
-                            symbols.push(env.unique_symbol());
+                                .push(*env.struct_indexing.get(record_index).unwrap());
+                            fields.push(CopyExisting);
                         }
 
-                        current += 1;
+                        index += 1;
                     }
                 }
             }
-            let symbols = symbols.into_bump_slice();
+
+            let new_struct_symbols = new_struct_symbols.into_bump_slice();
 
             let record_layout = layout_cache
                 .from_var(env.arena, record_var, env.subs)
@@ -4985,8 +4999,8 @@ pub fn with_hole<'a>(
                 _ => arena.alloc([record_layout]),
             };
 
-            if symbols.len() == 1 {
+            if single_field_struct {
-                // TODO we can probably special-case this more, skippiing the generation of
+                // TODO we can probably special-case this more, skipping the generation of
                 // UpdateExisting
                 let mut stmt = hole.clone();
 
@@ -4994,7 +5008,7 @@ pub fn with_hole<'a>(
 
                 match what_to_do {
                     UpdateExisting(field) => {
-                        substitute_in_exprs(env.arena, &mut stmt, assigned, symbols[0]);
+                        substitute_in_exprs(env.arena, &mut stmt, assigned, new_struct_symbols[0]);
 
                         stmt = assign_to_symbol(
                             env,
@@ -5002,11 +5016,11 @@ pub fn with_hole<'a>(
                             layout_cache,
                             field.var,
                             *field.loc_expr.clone(),
-                            symbols[0],
+                            new_struct_symbols[0],
                             stmt,
                         );
                     }
-                    CopyExisting(_) => {
+                    CopyExisting => {
                         unreachable!(
                             r"when a record has just one field and is updated, it must update that one field"
                         );
@@ -5015,12 +5029,10 @@ pub fn with_hole<'a>(
 
                 stmt
             } else {
-                let expr = Expr::Struct(symbols);
+                let expr = Expr::Struct(new_struct_symbols);
                 let mut stmt = Stmt::Let(assigned, expr, record_layout, hole);
 
-                let it = field_layouts.iter().zip(symbols.iter()).zip(fields);
+                for (new_struct_symbol, what_to_do) in new_struct_symbols.iter().zip(fields) {
-
-                for ((field_layout, symbol), what_to_do) in it {
                     match what_to_do {
                         UpdateExisting(field) => {
                             stmt = assign_to_symbol(
@@ -5029,47 +5041,54 @@ pub fn with_hole<'a>(
                                 layout_cache,
                                 field.var,
                                 *field.loc_expr.clone(),
-                                *symbol,
+                                *new_struct_symbol,
                                 stmt,
                             );
                         }
-                        CopyExisting(index) => {
+                        CopyExisting => {
-                            let structure_needs_specialization =
+                            // When a field is copied, the indexing symbol is already placed in new_struct_symbols
-                                procs.ability_member_aliases.get(structure).is_some()
+                            // Thus, we don't need additional logic here.
-                                    || procs.is_module_thunk(structure)
-                                    || procs.is_imported_module_thunk(structure);
-
-                            let specialized_structure_sym = if structure_needs_specialization {
-                                // We need to specialize the record now; create a new one for it.
-                                // TODO: reuse this symbol for all updates
-                                env.unique_symbol()
-                            } else {
-                                // The record is already good.
-                                structure
-                            };
-
-                            let access_expr = Expr::StructAtIndex {
-                                structure: specialized_structure_sym,
-                                index,
-                                field_layouts,
-                            };
-                            stmt =
-                                Stmt::Let(*symbol, access_expr, *field_layout, arena.alloc(stmt));
-
-                            if structure_needs_specialization {
-                                stmt = specialize_symbol(
-                                    env,
-                                    procs,
-                                    layout_cache,
-                                    Some(record_var),
-                                    specialized_structure_sym,
-                                    env.arena.alloc(stmt),
-                                    structure,
-                                );
-                            }
                         }
                     }
                 }
+
+                let structure_needs_specialization =
+                    procs.ability_member_aliases.get(structure).is_some()
+                        || procs.is_module_thunk(structure)
+                        || procs.is_imported_module_thunk(structure);
+
+                let specialized_structure_sym = if structure_needs_specialization {
+                    // We need to specialize the record now; create a new one for it.
+                    env.unique_symbol()
+                } else {
+                    // The record is already good.
+                    structure
+                };
+
+                for record_index in current_struct_indexing.into_iter().rev() {
+                    if let Some(symbol) = env.struct_indexing.get_used(&record_index) {
+                        let layout = field_layouts[record_index.1 as usize];
+                        let access_expr = Expr::StructAtIndex {
+                            structure: specialized_structure_sym,
+                            index: record_index.1,
+                            field_layouts,
+                        };
+                        stmt = Stmt::Let(symbol, access_expr, layout, arena.alloc(stmt));
+                    };
+                }
+
+                if structure_needs_specialization {
+                    stmt = specialize_symbol(
+                        env,
+                        procs,
+                        layout_cache,
+                        Some(record_var),
+                        specialized_structure_sym,
+                        env.arena.alloc(stmt),
+                        structure,
+                    );
+                }
+
                 stmt
             }
         }
@@ -5227,7 +5246,7 @@ pub fn with_hole<'a>(
                     // re-use that symbol, and don't define its value again
                     let mut result;
                     use ReuseSymbol::*;
-                    match can_reuse_symbol(env, procs, &loc_expr.value, fn_var) {
+                    match can_reuse_symbol(env, layout_cache, procs, &loc_expr.value, fn_var) {
                         LocalFunction(_) => {
                             unreachable!("if this was known to be a function, we would not be here")
                         }
@@ -5685,22 +5704,28 @@ fn compile_struct_like<'a, L, UnusedLayout>(
         // TODO how should function pointers be handled here?
         use ReuseSymbol::*;
         match take_elem_expr(index) {
-            Some((var, loc_expr)) => match can_reuse_symbol(env, procs, &loc_expr.value, var) {
+            Some((var, loc_expr)) => {
-                Imported(symbol) | LocalFunction(symbol) | UnspecializedExpr(symbol) => {
+                match can_reuse_symbol(env, layout_cache, procs, &loc_expr.value, var) {
-                    elem_symbols.push(symbol);
+                    Imported(symbol) | LocalFunction(symbol) | UnspecializedExpr(symbol) => {
-                    can_elems.push(Field::FunctionOrUnspecialized(symbol, variable));
+                        elem_symbols.push(symbol);
+                        can_elems.push(Field::FunctionOrUnspecialized(symbol, variable));
+                    }
+                    Value(symbol) => {
+                        let reusable = procs.get_or_insert_symbol_specialization(
+                            env,
+                            layout_cache,
+                            symbol,
+                            var,
+                        );
+                        elem_symbols.push(reusable);
+                        can_elems.push(Field::ValueSymbol);
+                    }
+                    NotASymbol => {
+                        elem_symbols.push(env.unique_symbol());
+                        can_elems.push(Field::Field(var, *loc_expr));
+                    }
                 }
-                Value(symbol) => {
+            }
-                    let reusable =
-                        procs.get_or_insert_symbol_specialization(env, layout_cache, symbol, var);
-                    elem_symbols.push(reusable);
-                    can_elems.push(Field::ValueSymbol);
-                }
-                NotASymbol => {
-                    elem_symbols.push(env.unique_symbol());
-                    can_elems.push(Field::Field(var, *loc_expr));
-                }
-            },
             None => {
                 // this field was optional, but not given
                 continue;
@@ -6816,7 +6841,7 @@ pub fn from_can<'a>(
             store_specialized_expectation_lookups(env, [variable], &[spec_var]);
 
             let symbol_is_reused = matches!(
-                can_reuse_symbol(env, procs, &loc_condition.value, variable),
+                can_reuse_symbol(env, layout_cache, procs, &loc_condition.value, variable),
                 ReuseSymbol::Value(_)
             );
 
@@ -7615,7 +7640,8 @@ enum ReuseSymbol {
 
 fn can_reuse_symbol<'a>(
     env: &mut Env<'a, '_>,
-    procs: &Procs<'a>,
+    layout_cache: &mut LayoutCache<'a>,
+    procs: &mut Procs<'a>,
     expr: &roc_can::expr::Expr,
     expr_var: Variable,
 ) -> ReuseSymbol {
@@ -7627,6 +7653,52 @@ fn can_reuse_symbol<'a>(
             late_resolve_ability_specialization(env, *member, *specialization_id, expr_var)
         }
         Var(symbol, _) => *symbol,
+        RecordAccess {
+            record_var,
+            field,
+            loc_expr,
+            ..
+        } => {
+            let sorted_fields_result = {
+                let mut layout_env = layout::Env::from_components(
+                    layout_cache,
+                    env.subs,
+                    env.arena,
+                    env.target_info,
+                );
+                layout::sort_record_fields(&mut layout_env, *record_var)
+            };
+
+            let sorted_fields = match sorted_fields_result {
+                Ok(fields) => fields,
+                Err(_) => unreachable!("Can't access record with improper layout"),
+            };
+
+            let index = sorted_fields
+                .into_iter()
+                .enumerate()
+                .find_map(|(current, (label, _, _))| (label == *field).then_some(current));
+
+            let struct_index = index.expect("field not in its own type");
+
+            let struct_symbol = possible_reuse_symbol_or_specialize(
+                env,
+                procs,
+                layout_cache,
+                &loc_expr.value,
+                *record_var,
+            );
+
+            match env
+                .struct_indexing
+                .get((struct_symbol, struct_index as u64))
+            {
+                Some(symbol) => *symbol,
+                None => {
+                    return NotASymbol;
+                }
+            }
+        }
         _ => return NotASymbol,
     };
 
@@ -7660,7 +7732,7 @@ fn possible_reuse_symbol_or_specialize<'a>(
     expr: &roc_can::expr::Expr,
     var: Variable,
 ) -> Symbol {
-    match can_reuse_symbol(env, procs, expr, var) {
+    match can_reuse_symbol(env, layout_cache, procs, expr, var) {
         ReuseSymbol::Value(symbol) => {
             procs.get_or_insert_symbol_specialization(env, layout_cache, symbol, var)
         }
@@ -7999,7 +8071,7 @@ fn assign_to_symbol<'a>(
     result: Stmt<'a>,
 ) -> Stmt<'a> {
     use ReuseSymbol::*;
-    match can_reuse_symbol(env, procs, &loc_arg.value, arg_var) {
+    match can_reuse_symbol(env, layout_cache, procs, &loc_arg.value, arg_var) {
         Imported(original) | LocalFunction(original) | UnspecializedExpr(original) => {
             // for functions we must make sure they are specialized correctly
             specialize_symbol(
@@ -9983,3 +10055,42 @@ where
 
     answer
 }
+
+enum Usage {
+    Used,
+    Unused,
+}
+
+pub struct UsageTrackingMap<K, V> {
+    map: MutMap<K, (V, Usage)>,
+}
+
+impl<K, V> Default for UsageTrackingMap<K, V> {
+    fn default() -> Self {
+        Self {
+            map: MutMap::default(),
+        }
+    }
+}
+
+impl<K, V> UsageTrackingMap<K, V>
+where
+    K: std::cmp::Eq + std::hash::Hash,
+{
+    pub fn insert(&mut self, key: K, value: V) {
+        self.map.insert(key, (value, Usage::Unused));
+    }
+
+    pub fn get(&mut self, key: K) -> Option<&V> {
+        let (value, usage) = self.map.get_mut(&key)?;
+        *usage = Usage::Used;
+        Some(value)
+    }
+
+    fn get_used(&mut self, key: &K) -> Option<V> {
+        self.map.remove(key).and_then(|(value, usage)| match usage {
+            Usage::Used => Some(value),
+            Usage::Unused => None,
+        })
+    }
+}

crates/compiler/test_gen/src/gen_num.rs

@@ -1842,7 +1842,7 @@ fn float_add_checked_fail() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen_dev"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn float_add_overflow() {
     assert_evals_to!(
         "1.7976931348623157e308 + 1.7976931348623157e308",

crates/compiler/test_gen/src/gen_primitives.rs

@@ -597,7 +597,7 @@ fn top_level_destructure() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_len_0() {
     assert_evals_to!(
         indoc!(
@@ -625,7 +625,7 @@ fn linked_list_len_0() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_len_twice_0() {
     assert_evals_to!(
         indoc!(
@@ -653,7 +653,7 @@ fn linked_list_len_twice_0() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_len_1() {
     assert_evals_to!(
         indoc!(
@@ -681,7 +681,7 @@ fn linked_list_len_1() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_len_twice_1() {
     assert_evals_to!(
         indoc!(
@@ -709,7 +709,7 @@ fn linked_list_len_twice_1() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_len_3() {
     assert_evals_to!(
         indoc!(
@@ -738,7 +738,7 @@ fn linked_list_len_3() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_sum_num_a() {
     assert_evals_to!(
         indoc!(
@@ -767,7 +767,7 @@ fn linked_list_sum_num_a() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_sum_int() {
     assert_evals_to!(
         indoc!(
@@ -795,7 +795,7 @@ fn linked_list_sum_int() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_map() {
     assert_evals_to!(
         indoc!(
@@ -1244,7 +1244,7 @@ fn return_wrapped_closure() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_is_singleton() {
     assert_evals_to!(
         indoc!(
@@ -1279,7 +1279,7 @@ fn linked_list_is_singleton() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_is_empty_1() {
     assert_evals_to!(
         indoc!(
@@ -1314,7 +1314,7 @@ fn linked_list_is_empty_1() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_is_empty_2() {
     assert_evals_to!(
         indoc!(
@@ -1346,7 +1346,7 @@ fn linked_list_is_empty_2() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_singleton() {
     // verifies only that valid llvm is produced
     assert_evals_to!(
@@ -1712,7 +1712,7 @@ fn nested_pattern_match_two_ways() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_guarded_double_pattern_match() {
     // the important part here is that the first case (with the nested Cons) does not match
     // TODO this also has undefined behavior
@@ -1744,7 +1744,7 @@ fn linked_list_guarded_double_pattern_match() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn linked_list_double_pattern_match() {
     assert_evals_to!(
         indoc!(

crates/compiler/test_gen/src/gen_tags.rs

@@ -2063,7 +2063,7 @@ fn non_unary_union_with_lambda_set_with_imported_toplevels_issue_4733() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn nullable_wrapped_with_non_nullable_singleton_tags() {
     assert_evals_to!(
         indoc!(
@@ -2094,7 +2094,7 @@ fn nullable_wrapped_with_non_nullable_singleton_tags() {
 }
 
 #[test]
-#[cfg(any(feature = "gen-llvm", feature = "gen-wasm"))]
+#[cfg(any(feature = "gen-llvm", feature = "gen-wasm", feature = "gen-dev"))]
 fn nullable_wrapped_with_nullable_not_last_index() {
     assert_evals_to!(
         indoc!(
@@ -2102,9 +2102,9 @@ fn nullable_wrapped_with_nullable_not_last_index() {
             app "test" provides [main] to "./platform"
 
             Parser : [
-                OneOrMore Parser,
-                Keyword Str,
                 CharLiteral,
+                Keyword Str,
+                OneOrMore Parser,
             ]
 
             toIdParser : Parser -> Str

crates/compiler/test_mono/generated/dict.txt

@@ -1,28 +1,28 @@
-procedure Dict.1 (Dict.547):
+procedure Dict.1 (Dict.537):
-    let Dict.556 : List {[], []} = Array [];
+    let Dict.546 : List {[], []} = Array [];
-    let Dict.563 : U64 = 0i64;
+    let Dict.553 : U64 = 0i64;
-    let Dict.564 : U64 = 8i64;
+    let Dict.554 : U64 = 8i64;
-    let Dict.557 : List U64 = CallByName List.11 Dict.563 Dict.564;
+    let Dict.547 : List U64 = CallByName List.11 Dict.553 Dict.554;
-    let Dict.560 : I8 = CallByName Dict.37;
+    let Dict.550 : I8 = CallByName Dict.36;
-    let Dict.561 : U64 = 8i64;
+    let Dict.551 : U64 = 8i64;
-    let Dict.558 : List I8 = CallByName List.11 Dict.560 Dict.561;
+    let Dict.548 : List I8 = CallByName List.11 Dict.550 Dict.551;
-    let Dict.559 : U64 = 0i64;
+    let Dict.549 : U64 = 0i64;
-    let Dict.555 : {List {[], []}, List U64, List I8, U64} = Struct {Dict.556, Dict.557, Dict.558, Dict.559};
+    let Dict.545 : {List {[], []}, List U64, List I8, U64} = Struct {Dict.546, Dict.547, Dict.548, Dict.549};
-    ret Dict.555;
+    ret Dict.545;
 
-procedure Dict.37 ():
+procedure Dict.36 ():
-    let Dict.562 : I8 = -128i64;
+    let Dict.552 : I8 = -128i64;
-    ret Dict.562;
+    ret Dict.552;
 
-procedure Dict.4 (Dict.553):
+procedure Dict.4 (Dict.543):
-    let Dict.99 : U64 = StructAtIndex 3 Dict.553;
+    let Dict.97 : U64 = StructAtIndex 3 Dict.543;
-    let #Derived_gen.2 : List {[], []} = StructAtIndex 0 Dict.553;
+    let #Derived_gen.2 : List {[], []} = StructAtIndex 0 Dict.543;
     dec #Derived_gen.2;
-    let #Derived_gen.1 : List U64 = StructAtIndex 1 Dict.553;
+    let #Derived_gen.1 : List U64 = StructAtIndex 1 Dict.543;
     dec #Derived_gen.1;
-    let #Derived_gen.0 : List I8 = StructAtIndex 2 Dict.553;
+    let #Derived_gen.0 : List I8 = StructAtIndex 2 Dict.543;
     dec #Derived_gen.0;
-    ret Dict.99;
+    ret Dict.97;
 
 procedure List.11 (List.115, List.116):
     let List.495 : List I8 = CallByName List.68 List.116;

crates/compiler/test_mono/generated/drop_specialize_after_struct.txt

@@ -0,0 +1,6 @@
+procedure Test.0 ():
+    let Test.2 : Str = "value";
+    let Test.3 : {Str, Str} = Struct {Test.2, Test.2};
+    dec Test.2;
+    let Test.4 : Str = "result";
+    ret Test.4;

crates/compiler/test_mono/generated/encode_derived_nested_record_string.txt

@@ -697,8 +697,8 @@ procedure Json.25 (Json.183):
         let Json.1906 : List U8 = CallByName List.8 Json.1907 Json.1908;
         ret Json.1906;
     else
-        let Json.1948 : U64 = StructAtIndex 0 Json.186;
         inc Json.184;
+        let Json.1948 : U64 = StructAtIndex 0 Json.186;
         let Json.1947 : {List U8, List U8} = CallByName List.52 Json.184 Json.1948;
         let Json.210 : List U8 = StructAtIndex 0 Json.1947;
         let Json.212 : List U8 = StructAtIndex 1 Json.1947;

crates/compiler/test_mono/generated/encode_derived_record_one_field_string.txt

@@ -623,8 +623,8 @@ procedure Json.25 (Json.183):
         let Json.1532 : List U8 = CallByName List.8 Json.1533 Json.1534;
         ret Json.1532;
     else
-        let Json.1574 : U64 = StructAtIndex 0 Json.186;
         inc Json.184;
+        let Json.1574 : U64 = StructAtIndex 0 Json.186;
         let Json.1573 : {List U8, List U8} = CallByName List.52 Json.184 Json.1574;
         let Json.210 : List U8 = StructAtIndex 0 Json.1573;
         let Json.212 : List U8 = StructAtIndex 1 Json.1573;

crates/compiler/test_mono/generated/encode_derived_record_two_field_strings.txt

@@ -630,8 +630,8 @@ procedure Json.25 (Json.183):
         let Json.1532 : List U8 = CallByName List.8 Json.1533 Json.1534;
         ret Json.1532;
     else
-        let Json.1574 : U64 = StructAtIndex 0 Json.186;
         inc Json.184;
+        let Json.1574 : U64 = StructAtIndex 0 Json.186;
         let Json.1573 : {List U8, List U8} = CallByName List.52 Json.184 Json.1574;
         let Json.210 : List U8 = StructAtIndex 0 Json.1573;
         let Json.212 : List U8 = StructAtIndex 1 Json.1573;

crates/compiler/test_mono/generated/encode_derived_string.txt

@@ -118,8 +118,8 @@ procedure Json.25 (Json.183):
         let Json.1179 : List U8 = CallByName List.8 Json.1180 Json.1181;
         ret Json.1179;
     else
-        let Json.1221 : U64 = StructAtIndex 0 Json.186;
         inc Json.184;
+        let Json.1221 : U64 = StructAtIndex 0 Json.186;
         let Json.1220 : {List U8, List U8} = CallByName List.52 Json.184 Json.1221;
         let Json.210 : List U8 = StructAtIndex 0 Json.1220;
         let Json.212 : List U8 = StructAtIndex 1 Json.1220;

crates/compiler/test_mono/generated/encode_derived_tag_one_field_string.txt

@@ -147,8 +147,8 @@ procedure Json.25 (Json.183):
         let Json.1220 : List U8 = CallByName List.8 Json.1221 Json.1222;
         ret Json.1220;
     else
-        let Json.1262 : U64 = StructAtIndex 0 Json.186;
         inc Json.184;
+        let Json.1262 : U64 = StructAtIndex 0 Json.186;
         let Json.1261 : {List U8, List U8} = CallByName List.52 Json.184 Json.1262;
         let Json.210 : List U8 = StructAtIndex 0 Json.1261;
         let Json.212 : List U8 = StructAtIndex 1 Json.1261;

crates/compiler/test_mono/generated/encode_derived_tag_two_payloads_string.txt

@@ -150,8 +150,8 @@ procedure Json.25 (Json.183):
         let Json.1220 : List U8 = CallByName List.8 Json.1221 Json.1222;
         ret Json.1220;
     else
-        let Json.1262 : U64 = StructAtIndex 0 Json.186;
         inc Json.184;
+        let Json.1262 : U64 = StructAtIndex 0 Json.186;
         let Json.1261 : {List U8, List U8} = CallByName List.52 Json.184 Json.1262;
         let Json.210 : List U8 = StructAtIndex 0 Json.1261;
         let Json.212 : List U8 = StructAtIndex 1 Json.1261;

crates/compiler/test_mono/generated/issue_2535_let_weakened_fields_referenced_in_list.txt

@@ -1,13 +1,13 @@
 procedure Test.1 ():
-    let Test.7 : U8 = 1i64;
+    let Test.10 : U8 = 1i64;
-    let Test.8 : U8 = 2i64;
+    let Test.11 : U8 = 2i64;
-    let Test.6 : {U8, U8} = Struct {Test.7, Test.8};
+    let Test.9 : {U8, U8} = Struct {Test.10, Test.11};
-    ret Test.6;
+    ret Test.9;
 
 procedure Test.0 ():
-    let Test.9 : {U8, U8} = CallByName Test.1;
+    let Test.13 : {U8, U8} = CallByName Test.1;
-    let Test.3 : U8 = StructAtIndex 0 Test.9;
+    let Test.4 : U8 = StructAtIndex 0 Test.13;
-    let Test.5 : {U8, U8} = CallByName Test.1;
+    let Test.8 : {U8, U8} = CallByName Test.1;
-    let Test.4 : U8 = StructAtIndex 1 Test.5;
+    let Test.6 : U8 = StructAtIndex 1 Test.8;
-    let Test.2 : List U8 = Array [Test.3, Test.4];
+    let Test.2 : List U8 = Array [Test.4, Test.6];
     ret Test.2;

crates/compiler/test_mono/generated/issue_4749.txt

@@ -179,8 +179,8 @@ procedure Json.60 (Json.540):
     let Json.1336 : U8 = GetTagId Json.1327;
     let Json.1337 : Int1 = lowlevel Eq Json.1335 Json.1336;
     if Json.1337 then
-        let Json.542 : U64 = UnionAtIndex (Id 2) (Index 0) Json.1327;
         inc Json.540;
+        let Json.542 : U64 = UnionAtIndex (Id 2) (Index 0) Json.1327;
         let Json.1329 : List U8 = CallByName List.29 Json.540 Json.542;
         let Json.1332 : U64 = 0i64;
         let Json.1331 : {U64, U64} = Struct {Json.542, Json.1332};
@@ -532,18 +532,15 @@ procedure Json.68 ():
 procedure Json.69 (Json.1467):
     joinpoint Json.1197 Json.1165:
         let Json.599 : List U8 = StructAtIndex 0 Json.1165;
-        inc Json.599;
+        inc 4 Json.599;
         let Json.600 : List U8 = StructAtIndex 1 Json.1165;
         let Json.1315 : U64 = 0i64;
         let Json.601 : [C {}, C U8] = CallByName List.2 Json.599 Json.1315;
         let Json.1314 : U64 = 1i64;
-        inc Json.599;
         let Json.602 : [C {}, C U8] = CallByName List.2 Json.599 Json.1314;
         let Json.1313 : U64 = 2i64;
-        inc Json.599;
         let Json.603 : List U8 = CallByName List.29 Json.599 Json.1313;
         let Json.1312 : U64 = 6i64;
-        inc Json.599;
         let Json.604 : List U8 = CallByName List.29 Json.599 Json.1312;
         let Json.1198 : {[C {}, C U8], [C {}, C U8]} = Struct {Json.601, Json.602};
         joinpoint Json.1277:
@@ -832,7 +829,7 @@ procedure Test.3 ():
     let Test.7 : Str = "Roc";
     let Test.6 : [C [C List U8, C ], C Str] = TagId(1) Test.7;
     let Test.5 : Int1 = CallByName Bool.11 Test.1 Test.6;
-    dec Test.6;
+    dec Test.7;
     expect Test.5;
     dec Test.0;
     dec Test.1;

crates/compiler/test_mono/generated/issue_4772_weakened_monomorphic_destructure.txt

@@ -153,8 +153,8 @@ procedure Json.60 (Json.540):
     let Json.1336 : U8 = GetTagId Json.1327;
     let Json.1337 : Int1 = lowlevel Eq Json.1335 Json.1336;
     if Json.1337 then
-        let Json.542 : U64 = UnionAtIndex (Id 2) (Index 0) Json.1327;
         inc Json.540;
+        let Json.542 : U64 = UnionAtIndex (Id 2) (Index 0) Json.1327;
         let Json.1329 : List U8 = CallByName List.29 Json.540 Json.542;
         let Json.1332 : U64 = 0i64;
         let Json.1331 : {U64, U64} = Struct {Json.542, Json.1332};
@@ -506,18 +506,15 @@ procedure Json.68 ():
 procedure Json.69 (Json.1467):
     joinpoint Json.1197 Json.1165:
         let Json.599 : List U8 = StructAtIndex 0 Json.1165;
-        inc Json.599;
+        inc 4 Json.599;
         let Json.600 : List U8 = StructAtIndex 1 Json.1165;
         let Json.1315 : U64 = 0i64;
         let Json.601 : [C {}, C U8] = CallByName List.2 Json.599 Json.1315;
         let Json.1314 : U64 = 1i64;
-        inc Json.599;
         let Json.602 : [C {}, C U8] = CallByName List.2 Json.599 Json.1314;
         let Json.1313 : U64 = 2i64;
-        inc Json.599;
         let Json.603 : List U8 = CallByName List.29 Json.599 Json.1313;
         let Json.1312 : U64 = 6i64;
-        inc Json.599;
         let Json.604 : List U8 = CallByName List.29 Json.599 Json.1312;
         let Json.1198 : {[C {}, C U8], [C {}, C U8]} = Struct {Json.601, Json.602};
         joinpoint Json.1277:
@@ -865,7 +862,7 @@ procedure Test.12 ():
     let Test.16 : {List U8, I64} = Struct {Test.17, Test.18};
     let Test.15 : [C Str, C {List U8, I64}] = TagId(1) Test.16;
     let Test.14 : Int1 = CallByName Bool.11 Test.10 Test.15;
-    dec Test.15;
+    dec Test.16;
     expect Test.14;
     dec Test.10;
     let Test.13 : {} = Struct {};

crates/compiler/test_mono/generated/list_one_vs_one_spread_issue_4685.txt

@@ -5,7 +5,8 @@ procedure Test.0 ():
     let Test.9 : U64 = 1i64;
     let Test.10 : Int1 = lowlevel Eq Test.8 Test.9;
     if Test.10 then
-        dec Test.1;
+        dec Test.11;
+        decref Test.1;
         let Test.3 : Str = "B";
         ret Test.3;
     else

crates/compiler/test_mono/generated/peano1.txt

@@ -5,11 +5,20 @@ procedure Test.0 ():
     let Test.2 : [<rnu><null>, C *self] = TagId(0) Test.13;
     let Test.10 : U8 = 1i64;
     let Test.11 : U8 = GetTagId Test.2;
-    dec Test.2;
+    joinpoint #Derived_gen.0:
-    let Test.12 : Int1 = lowlevel Eq Test.10 Test.11;
+        let Test.12 : Int1 = lowlevel Eq Test.10 Test.11;
-    if Test.12 then
+        if Test.12 then
-        let Test.8 : I64 = 0i64;
+            let Test.8 : I64 = 0i64;
-        ret Test.8;
+            ret Test.8;
+        else
+            let Test.9 : I64 = 1i64;
+            ret Test.9;
+    in
+    let #Derived_gen.1 : Int1 = lowlevel RefCountIsUnique Test.2;
+    if #Derived_gen.1 then
+        dec Test.13;
+        decref Test.2;
+        jump #Derived_gen.0;
     else
-        let Test.9 : I64 = 1i64;
+        decref Test.2;
-        ret Test.9;
+        jump #Derived_gen.0;

crates/compiler/test_mono/generated/polymorphic_expression_unification.txt

@@ -30,6 +30,15 @@ procedure Test.0 ():
     let Test.16 : Str = "";
     let Test.15 : [<r>C List *self, C Str] = TagId(1) Test.16;
     let Test.13 : Int1 = CallByName Bool.11 Test.14 Test.15;
-    dec Test.15;
+    joinpoint #Derived_gen.0:
-    dec Test.14;
+        dec Test.14;
-    ret Test.13;
+        ret Test.13;
+    in
+    let #Derived_gen.1 : Int1 = lowlevel RefCountIsUnique Test.15;
+    if #Derived_gen.1 then
+        dec Test.16;
+        decref Test.15;
+        jump #Derived_gen.0;
+    else
+        decref Test.15;
+        jump #Derived_gen.0;

crates/compiler/test_mono/generated/quicksort_swap.txt

@@ -45,10 +45,9 @@ procedure Num.22 (#Attr.2, #Attr.3):
 
 procedure Test.1 (Test.2):
     let Test.28 : U64 = 0i64;
-    inc Test.2;
+    inc 2 Test.2;
     let Test.26 : [C {}, C I64] = CallByName List.2 Test.2 Test.28;
     let Test.27 : U64 = 0i64;
-    inc Test.2;
     let Test.25 : [C {}, C I64] = CallByName List.2 Test.2 Test.27;
     let Test.8 : {[C {}, C I64], [C {}, C I64]} = Struct {Test.25, Test.26};
     joinpoint Test.22:

crates/compiler/test_mono/generated/record_update.txt

@@ -0,0 +1,47 @@
+procedure List.3 (List.104, List.105, List.106):
+    let List.503 : {List U64, U64} = CallByName List.64 List.104 List.105 List.106;
+    let List.502 : List U64 = StructAtIndex 0 List.503;
+    ret List.502;
+
+procedure List.6 (#Attr.2):
+    let List.501 : U64 = lowlevel ListLen #Attr.2;
+    ret List.501;
+
+procedure List.64 (List.101, List.102, List.103):
+    let List.500 : U64 = CallByName List.6 List.101;
+    let List.497 : Int1 = CallByName Num.22 List.102 List.500;
+    if List.497 then
+        let List.498 : {List U64, U64} = CallByName List.67 List.101 List.102 List.103;
+        ret List.498;
+    else
+        let List.496 : {List U64, U64} = Struct {List.101, List.103};
+        ret List.496;
+
+procedure List.67 (#Attr.2, #Attr.3, #Attr.4):
+    let List.499 : {List U64, U64} = lowlevel ListReplaceUnsafe #Attr.2 #Attr.3 #Attr.4;
+    ret List.499;
+
+procedure Num.22 (#Attr.2, #Attr.3):
+    let Num.281 : Int1 = lowlevel NumLt #Attr.2 #Attr.3;
+    ret Num.281;
+
+procedure Test.1 (Test.2):
+    let Test.6 : List U64 = StructAtIndex 0 Test.2;
+    let Test.8 : List U64 = StructAtIndex 1 Test.2;
+    let Test.10 : List U64 = StructAtIndex 2 Test.2;
+    let Test.13 : U64 = 8i64;
+    let Test.14 : U64 = 8i64;
+    let Test.9 : List U64 = CallByName List.3 Test.8 Test.13 Test.14;
+    let Test.11 : U64 = 7i64;
+    let Test.12 : U64 = 7i64;
+    let Test.7 : List U64 = CallByName List.3 Test.6 Test.11 Test.12;
+    let Test.5 : {List U64, List U64, List U64} = Struct {Test.7, Test.9, Test.10};
+    ret Test.5;
+
+procedure Test.0 ():
+    let Test.15 : List U64 = Array [];
+    let Test.16 : List U64 = Array [];
+    let Test.17 : List U64 = Array [];
+    let Test.4 : {List U64, List U64, List U64} = Struct {Test.15, Test.16, Test.17};
+    let Test.3 : {List U64, List U64, List U64} = CallByName Test.1 Test.4;
+    ret Test.3;

crates/compiler/test_mono/generated/rigids.txt

@@ -44,9 +44,8 @@ procedure Num.22 (#Attr.2, #Attr.3):
     ret Num.283;
 
 procedure Test.1 (Test.2, Test.3, Test.4):
-    inc Test.4;
+    inc 2 Test.4;
     let Test.29 : [C {}, C I64] = CallByName List.2 Test.4 Test.3;
-    inc Test.4;
     let Test.28 : [C {}, C I64] = CallByName List.2 Test.4 Test.2;
     let Test.13 : {[C {}, C I64], [C {}, C I64]} = Struct {Test.28, Test.29};
     joinpoint Test.25:

crates/compiler/test_mono/generated/unspecialized_lambda_set_unification_does_not_duplicate_identical_concrete_types.txt

@@ -136,8 +136,8 @@ procedure Json.25 (Json.183):
         let Json.1223 : List U8 = CallByName List.8 Json.1224 Json.1225;
         ret Json.1223;
     else
-        let Json.1265 : U64 = StructAtIndex 0 Json.186;
         inc Json.184;
+        let Json.1265 : U64 = StructAtIndex 0 Json.186;
         let Json.1264 : {List U8, List U8} = CallByName List.52 Json.184 Json.1265;
         let Json.210 : List U8 = StructAtIndex 0 Json.1264;
         let Json.212 : List U8 = StructAtIndex 1 Json.1264;

crates/compiler/test_mono/src/tests.rs

@@ -3050,3 +3050,31 @@ fn specialize_after_match() {
         "#
     )
 }
+
+#[mono_test]
+fn drop_specialize_after_struct() {
+    indoc!(
+        r#"
+        app "test" provides [main] to "./platform"
+
+        Tuple a b : { left : a, right : b }
+
+        main =
+            v = "value"
+            t = { left: v, right: v }
+            "result"
+        "#
+    )
+}
+
+#[mono_test]
+fn record_update() {
+    indoc!(
+        r#"
+        app "test" provides [main] to "./platform"
+        main = f {a: [], b: [], c:[]}
+        f : {a: List Nat, b: List Nat, c: List Nat} -> {a: List Nat, b: List Nat, c: List Nat}
+        f = \record -> {record & a: List.set record.a 7 7, b: List.set record.b 8 8}
+        "#
+    )
+}

crates/compiler/uitest/tests/specialize/record_update_between_modules.txt

@@ -23,10 +23,10 @@ procedure Dep.0 ():
     ret Dep.1;
 
 procedure Test.0 ():
-    let Test.3 : Str = "http://www.example.com";
+    let Test.5 : {Str, Str} = CallByName Dep.0;
-    let Test.4 : {Str, Str} = CallByName Dep.0;
+    let Test.2 : Str = StructAtIndex 0 Test.5;
-    let Test.2 : Str = StructAtIndex 0 Test.4;
+    let #Derived_gen.0 : Str = StructAtIndex 1 Test.5;
-    let #Derived_gen.0 : Str = StructAtIndex 1 Test.4;
     dec #Derived_gen.0;
-    let Test.1 : {Str, Str} = Struct {Test.2, Test.3};
+    let Test.4 : Str = "http://www.example.com";
+    let Test.1 : {Str, Str} = Struct {Test.2, Test.4};
     ret Test.1;

crates/error_macros/src/lib.rs

@@ -24,7 +24,7 @@ macro_rules! internal_error {
 macro_rules! user_error {
     ($($arg:tt)*) => ({
         eprintln!("We ran into an issue while compiling your code.");
-        eprintln!("Sadly, we don't havs a pretty error message for this case yet.");
+        eprintln!("Sadly, we don't have a pretty error message for this case yet.");
         eprintln!("If you can't figure out the problem from the context below, please reach out at: https://roc.zulipchat.com/");
         eprintln!($($arg)*);
         std::process::exit(1);

crates/linker/src/elf.rs

@@ -1471,21 +1471,11 @@ fn surgery_elf_help(
                             }
                         }
                     } else {
-                        // Explicitly ignore some symbols that are currently always linked.
+                        internal_error!(
-                        const ALWAYS_LINKED: &[&str] = &["__divti3", "__udivti3"];
+                            "Undefined Symbol in relocation, {:+x?}: {:+x?}",
-
+                            rel,
-                        match app_obj.symbol_by_index(index) {
+                            app_obj.symbol_by_index(index)
-                            Ok(sym) if ALWAYS_LINKED.contains(&sym.name().unwrap_or_default()) => {
+                        );
-                                continue
-                            }
-                            _ => {
-                                internal_error!(
-                                    "Undefined Symbol in relocation, {:+x?}: {:+x?}",
-                                    rel,
-                                    app_obj.symbol_by_index(index)
-                                );
-                            }
-                        }
                     }
                 }
 

crates/linker/src/pe.rs

@@ -434,7 +434,19 @@ pub(crate) fn surgery_pe(executable_path: &Path, metadata_path: &Path, roc_app_b
                         relocation,
                     );
                 } else {
-                    if *address == 0 && !name.starts_with("roc") {
+                    let is_ingested_compiler_rt = [
+                        "__muloti4",
+                        "__divti3",
+                        "__udivti3",
+                        "__modti3",
+                        "__umodti3",
+                        "__fixdfti",
+                        "__fixsfti",
+                        "__fixunsdfti",
+                        "__fixunssfti",
+                    ]
+                    .contains(&name.as_str());
+                    if *address == 0 && !name.starts_with("roc") && !is_ingested_compiler_rt {
                         eprintln!(
                             "I don't know the address of the {} function! this may cause segfaults",
                             name

crates/packaging/src/https.rs

@@ -13,6 +13,7 @@ use crate::tarball::Compression;
 // let's try to avoid doing that.
 const BROTLI_BUFFER_BYTES: usize = 8 * 1_000_000; // MB
 
+#[derive(Debug, PartialEq)]
 pub struct PackageMetadata<'a> {
     /// The BLAKE3 hash of the tarball's contents. Also the .tar filename on disk.
     pub content_hash: &'a str,
@@ -29,13 +30,29 @@ pub struct PackageMetadata<'a> {
 /// - .tar.br
 const VALID_EXTENSION_SUFFIXES: [&str; 2] = [".gz", ".br"];
 
-#[derive(Debug)]
+/// Since the TLD (top level domain) `.zip` is now available, there is a new attack
+/// vector where malicous URLs can be used to confuse the reader.
+/// Example of a URL which would take you to example.zip:
+/// https://github.com∕kubernetes∕kubernetes∕archive∕refs∕tags∕@example.zip
+/// roc employs a checksum mechanism to prevent tampering with packages.
+/// Nevertheless we should avoid such issues earlier.
+/// You can read more here: https://medium.com/@bobbyrsec/the-dangers-of-googles-zip-tld-5e1e675e59a5
+const MISLEADING_CHARACTERS_IN_URL: [char; 5] = [
+    '@',        // @ - For now we avoid usage of the @, to avoid the "tld zip" attack vector
+    '\u{2044}', // U+2044 ==  ⁄ Fraction Slash
+    '\u{2215}', // U+2215 ==  ∕ Division Slash
+    '\u{FF0F}', // U+2215 == ／ Fullwidth Solidus
+    '\u{29F8}', // U+29F8 == ⧸ Big Solidus
+];
+
+#[derive(Debug, PartialEq)]
 pub enum UrlProblem {
     InvalidExtensionSuffix(String),
     MissingTarExt,
     InvalidFragment(String),
     MissingHash,
     MissingHttps,
+    MisleadingCharacter,
 }
 
 impl<'a> TryFrom<&'a str> for PackageMetadata<'a> {
@@ -56,6 +73,14 @@ impl<'a> PackageMetadata<'a> {
             }
         };
 
+        // Next, check if there are misleading characters in the URL
+        if url
+            .chars()
+            .any(|ch| MISLEADING_CHARACTERS_IN_URL.contains(&ch))
+        {
+            return Err(UrlProblem::MisleadingCharacter);
+        }
+
         // Next, get the (optional) URL fragment, which must be a .roc filename
         let (without_fragment, fragment) = match without_protocol.rsplit_once('#') {
             Some((before_fragment, fragment)) => {
@@ -102,6 +127,105 @@ impl<'a> PackageMetadata<'a> {
     }
 }
 
+#[test]
+fn url_problem_missing_https() {
+    let expected = Err(UrlProblem::MissingHttps);
+    assert_eq!(PackageMetadata::try_from("http://example.com"), expected);
+}
+
+#[test]
+fn url_problem_misleading_characters() {
+    let expected = Err(UrlProblem::MisleadingCharacter);
+
+    for misleading_character_example in [
+        "https://user:password@example.com/",
+        //"https://example.com⁄path",
+        "https://example.com\u{2044}path",
+        //"https://example.com∕path",
+        "https://example.com\u{2215}path",
+        //"https://example.com／path",
+        "https://example.com\u{ff0f}path",
+        //"https://example.com⧸path",
+        "https://example.com\u{29f8}path",
+    ] {
+        assert_eq!(
+            PackageMetadata::try_from(misleading_character_example),
+            expected
+        );
+    }
+}
+
+#[test]
+fn url_problem_invalid_fragment_not_a_roc_file() {
+    let expected = Err(UrlProblem::InvalidFragment("filename.sh".to_string()));
+    assert_eq!(
+        PackageMetadata::try_from("https://example.com/#filename.sh"),
+        expected
+    );
+}
+
+#[test]
+fn url_problem_invalid_fragment_empty_roc_filename() {
+    let expected = Err(UrlProblem::InvalidFragment(".roc".to_string()));
+    assert_eq!(
+        PackageMetadata::try_from("https://example.com/#.roc"),
+        expected
+    );
+}
+
+#[test]
+fn url_problem_not_a_tar_url() {
+    let expected = Err(UrlProblem::MissingTarExt);
+    assert_eq!(
+        PackageMetadata::try_from("https://example.com/filename.zip"),
+        expected
+    );
+}
+
+#[test]
+fn url_problem_invalid_tar_suffix() {
+    let expected = Err(UrlProblem::InvalidExtensionSuffix(".zip".to_string()));
+    assert_eq!(
+        PackageMetadata::try_from("https://example.com/filename.tar.zip"),
+        expected
+    );
+}
+
+#[test]
+fn url_problem_missing_hash() {
+    let expected = Err(UrlProblem::MissingHash);
+    assert_eq!(
+        PackageMetadata::try_from("https://example.com/.tar.gz"),
+        expected
+    );
+}
+
+#[test]
+fn url_without_fragment() {
+    let expected = Ok(PackageMetadata {
+        cache_subdir: "example.com/path",
+        content_hash: "hash",
+        root_module_filename: None,
+    });
+    assert_eq!(
+        PackageMetadata::try_from("https://example.com/path/hash.tar.gz"),
+        expected
+    );
+}
+
+#[test]
+fn url_with_fragment() {
+    let expected = Ok(PackageMetadata {
+        cache_subdir: "example.com/path",
+        content_hash: "hash",
+        root_module_filename: Some("filename.roc"),
+    });
+    assert_eq!(
+        PackageMetadata::try_from("https://example.com/path/hash.tar.gz#filename.roc"),
+        expected
+    );
+}
+
 #[derive(Debug)]
 pub enum Problem {
     UnsupportedEncoding(String),

examples/virtual-dom-wip/platform/Html/Internal/Client.roc

@@ -656,49 +656,11 @@ nextNodeId = \rendered ->
 eqRenderedTree : RenderedTree state, RenderedTree state -> Bool
 eqRenderedTree = \a, b ->
     (a.root == b.root)
-    && eqRenderedNodes a.nodes b.nodes
+    && (a.nodes == b.nodes)
     && (List.len a.handlers == List.len b.handlers)
     && (a.deletedNodeCache == b.deletedNodeCache)
     && (a.deletedHandlerCache == b.deletedHandlerCache)
 
-eqRenderedNodes : List (Result RenderedNode [DeletedNode]), List (Result RenderedNode [DeletedNode]) -> Bool
-eqRenderedNodes = \a, b ->
-    List.map2 a b Tuple
-    |> List.all
-        (\t ->
-            when t is
-                Tuple (Ok x) (Ok y) -> eqRenderedNode x y
-                Tuple (Err x) (Err y) -> x == y
-                _ -> Bool.false)
-
-eqRenderedNode : RenderedNode, RenderedNode -> Bool
-eqRenderedNode = \a, b ->
-    when { a, b } is
-        { a: RenderedNone, b: RenderedNone } ->
-            Bool.true
-
-        { a: RenderedText aStr, b: RenderedText bStr } ->
-            aStr == bStr
-
-        { a: RenderedElement aName aAttrs aChildren, b: RenderedElement bName bAttrs bChildren } ->
-            (aName == bName)
-            && (aChildren == bChildren) # good enough for testing!
-            && eqRenderedAttrs aAttrs bAttrs
-
-        _ -> Bool.false
-
-eqRenderedAttrs : RenderedAttributes, RenderedAttributes -> Bool
-eqRenderedAttrs = \a, b ->
-    eqAttrDict a.eventListeners b.eventListeners
-    && eqAttrDict a.htmlAttrs b.htmlAttrs
-    && eqAttrDict a.domProps b.domProps
-    && eqAttrDict a.styles b.styles
-
-eqAttrDict : Dict Str v, Dict Str v -> Bool | v implements Eq
-eqAttrDict = \a, b ->
-    Dict.keys a
-    |> List.all \k -> Dict.get a k == Dict.get b k
-
 # indexNodes
 expect
     html : Html {}
@@ -713,12 +675,12 @@ expect
     expected = {
         nodes: [
             RenderedText "Roc",
-            RenderedElement "a" { emptyRenderedAttrs & htmlAttrs: Dict.fromList [T "href" "https://www.roc-lang.org/"] } [0],
+            RenderedElement "a" { emptyRenderedAttrs & htmlAttrs: Dict.fromList [("href", "https://www.roc-lang.org/")] } [0],
         ],
         siblingIds: [1],
     }
 
-    (List.map2 actual.nodes expected.nodes eqRenderedNode |> List.walk Bool.true Bool.and)
+    (actual.nodes == expected.nodes)
     && (actual.siblingIds == expected.siblingIds)
 
 # diff
@@ -822,7 +784,7 @@ expect
                 Ok (RenderedText "The app"),
                 Ok (RenderedElement "h1" emptyRenderedAttrs [0]),
                 Ok (RenderedText "The answer is 42"),
-                Ok (RenderedElement "div" { emptyRenderedAttrs & eventListeners: Dict.fromList [T "click" { accessors: [], handlerId: 0 }] } [2]),
+                Ok (RenderedElement "div" { emptyRenderedAttrs & eventListeners: Dict.fromList [("click", { accessors: [], handlerId: 0 })] } [2]),
                 Ok (RenderedElement "body" emptyRenderedAttrs [1, 3]),
             ],
             deletedNodeCache: [],