Create new lowlevels for refcounting

compiler/builtins/bitcode/src/main.zig

@@ -138,6 +138,7 @@ comptime {
 
 comptime {
     exportUtilsFn(utils.test_panic, "test_panic");
+    exportUtilsFn(utils.increfC, "incref");
     exportUtilsFn(utils.decrefC, "decref");
     exportUtilsFn(utils.decrefCheckNullC, "decref_check_null");
 

compiler/builtins/bitcode/src/utils.zig

@@ -104,6 +104,12 @@ pub const IntWidth = enum(u8) {
     I128 = 9,
 };
 
+pub fn increfC(ptr_to_refcount: *isize, amount: isize) callconv(.C) void {
+    var refcount = ptr_to_refcount.*;
+    var masked_amount = if (refcount == REFCOUNT_MAX_ISIZE) 0 else amount;
+    ptr_to_refcount.* = refcount + masked_amount;
+}
+
 pub fn decrefC(
     bytes_or_null: ?[*]isize,
     alignment: u32,
@@ -261,3 +267,17 @@ pub const UpdateMode = enum(u8) {
     Immutable = 0,
     InPlace = 1,
 };
+
+test "increfC, refcounted data" {
+    var mock_rc: isize = REFCOUNT_ONE_ISIZE + 17;
+    var ptr_to_refcount: *isize = &mock_rc;
+    increfC(ptr_to_refcount, 2);
+    try std.testing.expectEqual(mock_rc, REFCOUNT_ONE_ISIZE + 19);
+}
+
+test "increfC, static data" {
+    var mock_rc: isize = REFCOUNT_MAX_ISIZE;
+    var ptr_to_refcount: *isize = &mock_rc;
+    increfC(ptr_to_refcount, 2);
+    try std.testing.expectEqual(mock_rc, REFCOUNT_MAX_ISIZE);
+}

compiler/builtins/src/bitcode.rs

@@ -309,5 +309,6 @@ pub const DEC_MUL_WITH_OVERFLOW: &str = "roc_builtins.dec.mul_with_overflow";
 pub const DEC_DIV: &str = "roc_builtins.dec.div";
 
 pub const UTILS_TEST_PANIC: &str = "roc_builtins.utils.test_panic";
+pub const UTILS_INCREF: &str = "roc_builtins.utils.incref";
 pub const UTILS_DECREF: &str = "roc_builtins.utils.decref";
 pub const UTILS_DECREF_CHECK_NULL: &str = "roc_builtins.utils.decref_check_null";

compiler/gen_llvm/src/llvm/build.rs

@@ -6020,6 +6020,10 @@ fn run_low_level<'a, 'ctx, 'env>(
         | ListAny | ListAll | ListFindUnsafe | DictWalk => {
             unreachable!("these are higher order, and are handled elsewhere")
         }
+
+        RefCountGetPtr | RefCountInc | RefCountDec => {
+            unreachable!("LLVM backend does not use lowlevels for refcounting");
+        }
     }
 }
 

compiler/gen_wasm/src/low_level.rs

@@ -370,6 +370,7 @@ pub fn decode_low_level<'a>(
         Not => code_builder.i32_eqz(),
         Hash => return NotImplemented,
         ExpectTrue => return NotImplemented,
+        RefCountGetPtr | RefCountInc | RefCountDec => return NotImplemented,
     }
     Done
 }

compiler/module/src/low_level.rs

@@ -115,6 +115,9 @@ pub enum LowLevel {
     Not,
     Hash,
     ExpectTrue,
+    RefCountGetPtr,
+    RefCountInc,
+    RefCountDec,
 }
 
 macro_rules! higher_order {

compiler/mono/src/borrow.rs

@@ -1008,6 +1008,10 @@ pub fn lowlevel_borrow_signature(arena: &Bump, op: LowLevel) -> &[bool] {
         SetFromList => arena.alloc_slice_copy(&[owned]),
 
         ExpectTrue => arena.alloc_slice_copy(&[irrelevant]),
+
+        RefCountGetPtr | RefCountInc | RefCountDec => {
+            unreachable!("Refcounting lowlevel calls are inserted *after* borrow checking");
+        }
     }
 }