[PATCH] Avoid changing type in the type_hash_canon hash

[Richard Biener]

When building a type and type_hash_canon returns an existing type
avoid changing it, in particular its TYPE_CANONICAL.

Bootstrapped and tested on x86_64-unknown-linux-gnu for all languages.

OK for trunk?

Thanks,
Richard.

        PR middle-end/114931
        * tree.cc (build_array_type_1): Return early when type_hash_canon
        returned an older existing type.
        (build_function_type): Likewise.
        (build_method_type_directly): Likewise.
        (build_offset_type): Likewise.
---
 gcc/tree.cc | 12 ++++++++++++
 1 file changed, 12 insertions(+)

diff --git a/gcc/tree.cc b/gcc/tree.cc
index 83f3bf306af..780662549fe 100644
--- a/gcc/tree.cc
+++ b/gcc/tree.cc
@@ -7352,7 +7352,10 @@ build_array_type_1 (tree elt_type, tree index_type, bool 
typeless_storage,
   if (shared)
     {
       hashval_t hash = type_hash_canon_hash (t);
+      tree probe_type = t;
       t = type_hash_canon (hash, t);
+      if (t != probe_type)
+       return t;
     }
 
   if (TYPE_CANONICAL (t) == t && set_canonical)
@@ -7509,7 +7512,10 @@ build_function_type (tree value_type, tree arg_types,
 
   /* If we already have such a type, use the old one.  */
   hashval_t hash = type_hash_canon_hash (t);
+  tree probe_type = t;
   t = type_hash_canon (hash, t);
+  if (t != probe_type)
+    return t;
 
   /* Set up the canonical type. */
   any_structural_p   = TYPE_STRUCTURAL_EQUALITY_P (value_type);
@@ -7663,7 +7669,10 @@ build_method_type_directly (tree basetype,
 
   /* If we already have such a type, use the old one.  */
   hashval_t hash = type_hash_canon_hash (t);
+  tree probe_type = t;
   t = type_hash_canon (hash, t);
+  if (t != probe_type)
+    return t;
 
   /* Set up the canonical type. */
   any_structural_p
@@ -7720,7 +7729,10 @@ build_offset_type (tree basetype, tree type)
 
   /* If we already have such a type, use the old one.  */
   hashval_t hash = type_hash_canon_hash (t);
+  tree probe_type = t;
   t = type_hash_canon (hash, t);
+  if (t != probe_type)
+    return t;
 
   if (!COMPLETE_TYPE_P (t))
     layout_type (t);
-- 
2.35.3