[gcc r14-7952] gccrs: Fix overflow intrinsic use before init

[gcc r14-7952] gccrs: Fix overflow intrinsic use before init

[Arthur Cohen]

https://gcc.gnu.org/g:215b6acecb609d2a424e36116f1be8cf30d53438

commit r14-7952-g215b6acecb609d2a424e36116f1be8cf30d53438
Author: Philip Herron <herron.philip@googlemail.com>
Date:   Thu Aug 31 11:32:18 2023 +0100

    gccrs: Fix overflow intrinsic use before init
    
    The overflow intrinsic returns a tuple of (value, boolean) where it value
    is the operator result and boolean if it overflowed or not. The intrinsic
    here did not initilize the resulting tuple and therefore was creating a use
    before init error resulting in garbage results
    
    Addresses #1895
    
    gcc/rust/ChangeLog:
    
            * backend/rust-compile-intrinsic.cc (op_with_overflow_inner): fix use before init
    
    Signed-off-by: Philip Herron <herron.philip@googlemail.com>

Diff:
---
 gcc/rust/backend/rust-compile-intrinsic.cc | 46 +++++++++++++++++++-----------
 1 file changed, 30 insertions(+), 16 deletions(-)

diff --git a/gcc/rust/backend/rust-compile-intrinsic.cc b/gcc/rust/backend/rust-compile-intrinsic.cc
index 5c1cde3b202..cbf6c0bb2b8 100644
--- a/gcc/rust/backend/rust-compile-intrinsic.cc
+++ b/gcc/rust/backend/rust-compile-intrinsic.cc
@@ -598,7 +598,25 @@ op_with_overflow_inner (Context *ctx, TyTy::FnType *fntype, tree_code op)
   if (!ctx->get_backend ()->function_set_parameters (fndecl, param_vars))
     return error_mark_node;
 
-  enter_intrinsic_block (ctx, fndecl);
+  rust_assert (fntype->get_num_substitutions () == 1);
+  auto &param_mapping = fntype->get_substs ().at (0);
+  const TyTy::ParamType *param_tyty = param_mapping.get_param_ty ();
+  TyTy::BaseType *resolved_tyty = param_tyty->resolve ();
+  tree template_parameter_type
+    = TyTyResolveCompile::compile (ctx, resolved_tyty);
+
+  // this should match y as well or we can take it from the TyTy structure
+  tree tmp_stmt = error_mark_node;
+  Bvariable *result_variable = ctx->get_backend ()->temporary_variable (
+    fndecl, NULL_TREE, template_parameter_type, NULL_TREE,
+    true /*address_is_taken*/, UNDEF_LOCATION, &tmp_stmt);
+  Bvariable *bool_variable
+    = ctx->get_backend ()->temporary_variable (fndecl, NULL_TREE,
+					       boolean_type_node, NULL_TREE,
+					       true /*address_is_taken*/,
+					       UNDEF_LOCATION, &tmp_stmt);
+
+  enter_intrinsic_block (ctx, fndecl, {result_variable, bool_variable});
 
   // BUILTIN op_with_overflow FN BODY BEGIN
   auto x = ctx->get_backend ()->var_expression (x_param, UNDEF_LOCATION);
@@ -628,24 +646,20 @@ op_with_overflow_inner (Context *ctx, TyTy::FnType *fntype, tree_code op)
     }
   rust_assert (overflow_builtin != error_mark_node);
 
-  // this should match y as well or we can take it from the TyTy structure
-  tree overflow_op_type = TREE_TYPE (x);
-  tree tmp_stmt = error_mark_node;
-  Bvariable *bvar
-    = ctx->get_backend ()->temporary_variable (fndecl, NULL_TREE,
-					       overflow_op_type, NULL_TREE,
-					       true /*address_is_taken*/,
-					       UNDEF_LOCATION, &tmp_stmt);
-  ctx->add_statement (tmp_stmt);
-
-  tree result_decl = bvar->get_tree (UNDEF_LOCATION);
+  tree bool_decl = bool_variable->get_tree (BUILTINS_LOCATION);
+  tree result_decl = result_variable->get_tree (BUILTINS_LOCATION);
   tree result_ref = build_fold_addr_expr_loc (BUILTINS_LOCATION, result_decl);
 
-  tree did_overflow_node
-    = build_call_expr_loc (BUILTINS_LOCATION, overflow_builtin, 3, x, y,
-			   result_ref);
+  tree builtin_call = build_call_expr_loc (BUILTINS_LOCATION, overflow_builtin,
+					   3, x, y, result_ref);
+
+  tree overflow_assignment
+    = ctx->get_backend ()->assignment_statement (bool_decl, builtin_call,
+						 BUILTINS_LOCATION);
+
+  ctx->add_statement (overflow_assignment);
 
-  std::vector<tree> vals = {result_decl, did_overflow_node};
+  std::vector<tree> vals = {result_decl, bool_decl};
   tree tuple_type = TREE_TYPE (DECL_RESULT (fndecl));
   tree result_expr
     = ctx->get_backend ()->constructor_expression (tuple_type, false, vals, -1,