Add merge definitions pass

src/lib.rs

@@ -41,10 +41,7 @@ pub fn compile_book(book: &mut Book, opts: Opts) -> Result<CompileResult, String
   Ok(CompileResult { core_book, hvmc_names, labels, warnings })
 }
 
-pub fn desugar_book(
-  book: &mut Book,
-  Opts { eta, ref_to_ref, prune, supercombinators, simplify_main, .. }: Opts,
-) -> Result<(DefId, Vec<Warning>), String> {
+pub fn desugar_book(book: &mut Book, opts: Opts) -> Result<(DefId, Vec<Warning>), String> {
   let mut warnings = Vec::new();
   let main = book.check_has_main()?;
   book.check_shared_names()?;
@@ -57,19 +54,22 @@ pub fn desugar_book(
   book.check_unbound_vars()?;
   book.make_var_names_unique();
   book.linearize_vars();
-  book.eta_reduction(eta);
+  book.eta_reduction(opts.eta);
   // sanity check
   book.check_unbound_vars()?;
-  if supercombinators {
+  if opts.supercombinators {
     book.detach_supercombinators(main);
   }
-  if ref_to_ref {
+  if opts.ref_to_ref {
     book.simplify_ref_to_ref()?;
   }
-  if simplify_main {
+  if opts.simplify_main {
     book.simplify_main_ref(main);
   }
-  book.prune(Some(main), prune, &mut warnings);
+  if opts.merge_definitions {
+    book.merge_definition(main);
+  }
+  book.prune(Some(main), opts.prune, &mut warnings);
   Ok((main, warnings))
 }
 
@@ -190,8 +190,11 @@ pub struct Opts {
   /// Enables [term::transform::simplify_main_ref].
   pub simplify_main: bool,
 
-  /// Enables dereferences in `pre_reduce` pass.
+  /// Enables dereferences in [hvmc_net::pre_reduce] pass.
   pub pre_reduce_refs: bool,
+
+  /// Enables [term::transform::definition_merge]
+  pub merge_definitions: bool,
 }
 
 impl Opts {
@@ -205,6 +208,7 @@ impl Opts {
       supercombinators: true,
       simplify_main: true,
       pre_reduce_refs: true,
+      merge_definitions: true,
     }
   }
 
@@ -234,6 +238,8 @@ impl Opts {
         "no-simplify-main" => self.simplify_main = false,
         "pre-reduce-refs" => self.pre_reduce_refs = true,
         "no-pre-reduce-refs" => self.pre_reduce_refs = false,
+        "merge-defnitions" => self.merge_definitions = true,
+        "no-merge-defnitions" => self.merge_definitions = false,
         other => return Err(format!("Unknown option '{other}'.")),
       }
     }

src/main.rs

@@ -41,6 +41,7 @@ struct Args {
     all, eta, no-eta, prune, no-prune, ref-to-ref, no-ref-to-ref,
     supercombinators (enabled by default), no-supercombinators,
     simplify-main, no-simplify-main, pre-reduce-refs, no-pre-reduce-refs
+    merge-definitions, no-merge-definitions
     "#,
   )]
   pub opts: Vec<String>,

src/term/mod.rs

@@ -34,8 +34,8 @@ pub struct Book {
 
 #[derive(Debug, Clone, Default)]
 pub struct DefNames {
-  id_to_name: IndexMap<DefId, Name>,
-  name_to_id: IndexMap<Name, DefId>,
+  pub id_to_name: IndexMap<DefId, Name>,
+  pub name_to_id: IndexMap<Name, DefId>,
   id_count: DefId,
 }
 
@@ -63,13 +63,13 @@ pub enum Origin {
   Generated,
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum MatchNum {
   Zero,
   Succ(Option<Option<Name>>),
 }
 
-#[derive(Debug, Clone, PartialEq, Eq)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum Tag {
   Named(Name),
   Numeric(u32),
@@ -77,7 +77,7 @@ pub enum Tag {
   Static,
 }
 
-#[derive(Debug, Clone, Default)]
+#[derive(Debug, Clone, Default, PartialEq, Eq, Hash)]
 pub enum Term {
   Lam {
     tag: Tag,
@@ -149,7 +149,7 @@ pub enum Term {
   Era,
 }
 
-#[derive(Debug, Clone)]
+#[derive(Debug, Clone, PartialEq, Eq, Hash)]
 pub enum Pattern {
   Var(Option<Name>),
   Ctr(Name, Vec<Pattern>),
@@ -158,7 +158,7 @@ pub enum Pattern {
   List(Vec<Pattern>),
 }
 
-#[derive(Debug, Clone, Copy, PartialEq, Eq)]
+#[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
 pub enum Op {
   ADD,
   SUB,

src/term/transform/definition_merge.rs

@@ -0,0 +1,48 @@
+use super::simplify_ref_to_ref::subst_ref_to_ref;
+use crate::term::{Book, DefId, Name, Term};
+use std::collections::HashMap;
+
+impl Book {
+  /// Merges definitions that have the same structure into one definintion.
+  /// Expects variables to be linear.
+  pub fn merge_definition(&mut self, main: DefId) {
+    let mut term_to_defid: HashMap<Term, DefId> = HashMap::new();
+    let mut defid_map: HashMap<DefId, DefId> = HashMap::new();
+
+    for (id, def) in &mut self.defs {
+      if id == &main {
+        continue;
+      }
+
+      def.assert_no_pattern_matching_rules();
+      let term = std::mem::take(&mut def.rules[0].body);
+
+      if let Some(new) = term_to_defid.get(&term) {
+        defid_map.insert(*id, *new);
+      } else {
+        term_to_defid.insert(term, *id);
+      }
+    }
+
+    for (term, id) in term_to_defid {
+      self.defs.get_mut(&id).unwrap().rules[0].body = term;
+    }
+
+    for (old, new) in &defid_map {
+      let old_name = self.def_names.id_to_name.remove(old).unwrap();
+      let new_name = self.def_names.name(new).unwrap();
+
+      let merged_name = Name(format!("{}${}", new_name, old_name));
+
+      self.def_names.id_to_name.insert(*new, merged_name.clone());
+      self.def_names.name_to_id.insert(merged_name, *new);
+
+      self.def_names.name_to_id.remove(&old_name);
+      self.defs.remove(old);
+    }
+
+    for def in self.defs.values_mut() {
+      subst_ref_to_ref(&mut def.rules[0].body, &defid_map);
+    }
+  }
+}

src/term/transform/mod.rs

@@ -1,3 +1,4 @@
+pub mod definition_merge;
 pub mod definition_pruning;
 pub mod desugar_implicit_match_binds;
 pub mod desugar_let_destructors;

src/term/transform/simplify_ref_to_ref.rs

@@ -43,7 +43,7 @@ impl Book {
   }
 }
 
-fn subst_ref_to_ref(term: &mut Term, ref_map: &HashMap<DefId, DefId>) {
+pub fn subst_ref_to_ref(term: &mut Term, ref_map: &HashMap<DefId, DefId>) {
   match term {
     Term::Ref { def_id } => {
       if let Some(target_id) = ref_map.get(def_id) {

tests/golden_tests/compile_file_o_all/merge_definitions.hvm

@@ -0,0 +1,6 @@
+true  = @t @f t
+false = @t @f f
+fst = @a @b a
+snd = @a @b b
+
+main = @* (fst true (snd false *))

tests/snapshots/compile_file_o_all__adt_option_and.hvm.snap

@@ -2,10 +2,9 @@
 source: tests/golden_tests.rs
 input_file: tests/golden_tests/compile_file_o_all/adt_option_and.hvm
 ---
-@A = ({2 @H {2 @G a}} a)
+@A = ({2 @H {2 @C a}} a)
 @C = (* @None)
 @D = {4 a (b {2 {4 [b a] c} {2 * c}})}
-@G = (* @None)
 @H = {4 a ({2 @D {2 @C (a b)}} b)}
 @None = {2 * {2 a a}}
 @Some = (a {2 {4 a b} {2 * b}})

tests/snapshots/compile_file_o_all__ex0.hvm.snap

@@ -2,9 +2,9 @@
 source: tests/golden_tests.rs
 input_file: tests/golden_tests/compile_file_o_all/ex0.hvm
 ---
+@1 = (* (a a))
 @C_2 = ({3 (a b) (c a)} (c b))
 @S = (a ((a b) (* b)))
-@Z = (* (a a))
 @main = a
-& @C_2 ~ (@S (@Z a))
+& @C_2 ~ (@S (@1 a))
 

tests/snapshots/compile_file_o_all__merge_definitions.hvm.snap

@@ -0,0 +1,10 @@
+---
+source: tests/golden_tests.rs
+input_file: tests/golden_tests/compile_file_o_all/merge_definitions.hvm
+---
+@1 = (a (* a))
+@2 = (* (a a))
+@main = (* a)
+& @1 ~ (@1 (b a))
+& @2 ~ (@2 (* b))
+

tests/snapshots/compile_file_o_all__nested_adt_match.hvm.snap

@@ -4,8 +4,7 @@ input_file: tests/golden_tests/compile_file_o_all/nested_adt_match.hvm
 ---
 @8 = ({2 @C {2 @A a}} a)
 @A = #0
-@C = {4 {2 @G {2 @E a}} a}
-@E = #0
+@C = {4 {2 @G {2 @A a}} a}
 @G = {4 a a}
 @Some = (a {2 {4 a b} {2 * b}})
 @main = a

tests/snapshots/compile_file_o_all__tagged_sup.hvm.snap

@@ -2,9 +2,8 @@
 source: tests/golden_tests.rs
 input_file: tests/golden_tests/compile_file_o_all/tagged_sup.hvm
 ---
-@a = {3 (a a) (b b)}
-@b = {3 (a a) (b b)}
+@1 = {3 (a a) (b b)}
 @c = {5 (a a) (b b)}
 @main = a
-& @a ~ (@b (@c a))
+& @1 ~ (@1 (@c a))