Fix duplicated function generation for generics

When emitting the backend IR we need to check if we have already compiled
one already. This is all due to the fact when we do generic substitutions
in type resolution its only upon usage of a function the function is
substituted it gains a new unique ty_ref HIR ID to make sure new
substituted versions of a type have unique ids.

This means we can end up with multiple substitued versions of the same
function which end up being compiled multiple times. This was also the case
for generic data types but is already fixed.

Fixes #403

1 files changed, 25 insertions, 21 deletions

diff --git a/gcc/rust/backend/rust-compile-item.h b/gcc/rust/backend/rust-compile-item.h
index 5a7d846..c3dc279 100644
--- a/gcc/rust/backend/rust-compile-item.h
+++ b/gcc/rust/backend/rust-compile-item.h
@@ -92,17 +92,6 @@ public:
     if (!compile_fns)
       return;
 
-    // items can be forward compiled which means we may not need to invoke this
-    // code
-    Bfunction *lookup = nullptr;
-    if (ctx->lookup_function_decl (function.get_mappings ().get_hirid (),
-				   &lookup))
-      {
-	// has this been added to the list then it must be finished
-	if (ctx->function_completed (lookup))
-	  return;
-      }
-
     TyTy::BaseType *fntype_tyty;
     if (!ctx->get_tyctx ()->lookup_type (function.get_mappings ().get_hirid (),
 					 &fntype_tyty))
@@ -112,28 +101,43 @@ public:
 	return;
       }
 
-    if (fntype_tyty->get_kind () != TyTy::TypeKind::FNDEF)
-      {
-	rust_error_at (function.get_locus (), "invalid TyTy for function item");
-	return;
-      }
-
+    rust_assert (fntype_tyty->get_kind () == TyTy::TypeKind::FNDEF);
     TyTy::FnType *fntype = static_cast<TyTy::FnType *> (fntype_tyty);
     if (fntype->has_subsititions_defined ())
       {
-	// we cant do anything for this only when it is used
+	// we cant do anything for this only when it is used and a concrete type
+	// is given
 	if (concrete == nullptr)
 	  return;
 	else
 	  {
 	    rust_assert (concrete->get_kind () == TyTy::TypeKind::FNDEF);
 	    fntype = static_cast<TyTy::FnType *> (concrete);
+	  }
+      }
 
-	    // override the Hir Lookups for the substituions in this context
-	    fntype->override_context ();
+    // items can be forward compiled which means we may not need to invoke this
+    // code. We might also have already compiled this generic function as well.
+    Bfunction *lookup = nullptr;
+    if (ctx->lookup_function_decl (fntype->get_ty_ref (), &lookup, fntype))
+      {
+	// has this been added to the list then it must be finished
+	if (ctx->function_completed (lookup))
+	  {
+	    Bfunction *dummy = nullptr;
+	    if (!ctx->lookup_function_decl (fntype->get_ty_ref (), &dummy))
+	      ctx->insert_function_decl (fntype->get_ty_ref (), lookup, fntype);
+
+	    return;
 	  }
       }
 
+    if (fntype->has_subsititions_defined ())
+      {
+	// override the Hir Lookups for the substituions in this context
+	fntype->override_context ();
+      }
+
     ::Btype *compiled_fn_type = TyTyResolveCompile::compile (ctx, fntype);
 
     unsigned int flags = 0;
@@ -155,7 +159,7 @@ public:
     Bfunction *fndecl
       = ctx->get_backend ()->function (compiled_fn_type, ir_symbol_name,
 				       asm_name, flags, function.get_locus ());
-    ctx->insert_function_decl (fntype->get_ty_ref (), fndecl);
+    ctx->insert_function_decl (fntype->get_ty_ref (), fndecl, fntype);
 
     // setup the params
     TyTy::BaseType *tyret = fntype->get_return_type ();