[gcc r15-734] ada: Fix oversight in previous change

[gcc r15-734] ada: Fix oversight in previous change

[Marc Poulhi?s]

https://gcc.gnu.org/g:0715ed49b40311e9b2715f63308a970195dd2417

commit r15-734-g0715ed49b40311e9b2715f63308a970195dd2417
Author: Eric Botcazou <ebotcazou@adacore.com>
Date:   Thu Dec 14 13:05:52 2023 +0100

    ada: Fix oversight in previous change
    
    In rare cases, types using structural equality may reach relate_alias_sets.
    
    gcc/ada/
    
            * gcc-interface/utils.cc (relate_alias_sets): Restore previous code
            when the type uses structural equality.

Diff:
---
 gcc/ada/gcc-interface/utils.cc | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/gcc/ada/gcc-interface/utils.cc b/gcc/ada/gcc-interface/utils.cc
index b628481335d..ae520542ace 100644
--- a/gcc/ada/gcc-interface/utils.cc
+++ b/gcc/ada/gcc-interface/utils.cc
@@ -1867,8 +1867,11 @@ relate_alias_sets (tree new_type, tree old_type, enum alias_set_op op)
 		      && TYPE_NONALIASED_COMPONENT (new_type)
 			 != TYPE_NONALIASED_COMPONENT (old_type)));
 
-      /* The alias set always lives on the TYPE_CANONICAL.  */
-      TYPE_ALIAS_SET (TYPE_CANONICAL (new_type)) = get_alias_set (old_type);
+      /* The alias set is a property of the TYPE_CANONICAL if it exists.  */
+      if (TYPE_STRUCTURAL_EQUALITY_P (new_type))
+	TYPE_ALIAS_SET (new_type) = get_alias_set (old_type);
+      else
+	TYPE_ALIAS_SET (TYPE_CANONICAL (new_type)) = get_alias_set (old_type);
       break;
 
     case ALIAS_SET_SUBSET: