[gcc r15-7829] middle-end/97323 - TYPE_CANONICAL vs. ARRAY_TYPE modes

[Richard Biener]

https://gcc.gnu.org/g:556e25f0e9abc720c940994bd9a1491062933d49

commit r15-7829-g556e25f0e9abc720c940994bd9a1491062933d49
Author: Richard Biener <rguenther@suse.de>
Date:   Tue Mar 4 16:13:09 2025 +0100

    middle-end/97323 - TYPE_CANONICAL vs. ARRAY_TYPE modes
    
    For strict-alignment targets we can end up with BLKmode single-element
    array types when the element type is unaligned.  This confuses
    type checking since the canonical type would have an aligned
    element type and a non-BLKmode mode.  The following simply ignores
    the mode we assign to array types for this purpose, like we already
    do for record and union types.
    
            PR middle-end/97323
            * tree.cc (gimple_canonical_types_compatible_p): Ignore
            TYPE_MODE also for ARRAY_TYPE.
            (verify_type): Likewise.
    
            * gcc.dg/pr97323.c: New testcase.

Diff:
---
 gcc/testsuite/gcc.dg/pr97323.c | 5 +++++
 gcc/tree.cc                    | 2 ++
 2 files changed, 7 insertions(+)

diff --git a/gcc/testsuite/gcc.dg/pr97323.c b/gcc/testsuite/gcc.dg/pr97323.c
new file mode 100644
index 000000000000..8845a34fa158
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr97323.c
@@ -0,0 +1,5 @@
+/* { dg-do compile } */
+/* { dg-options "-g" } */
+
+typedef int a __attribute__((aligned(2)));
+a b[1];
diff --git a/gcc/tree.cc b/gcc/tree.cc
index 0743ed71c789..4e855b4b2d33 100644
--- a/gcc/tree.cc
+++ b/gcc/tree.cc
@@ -13982,6 +13982,7 @@ gimple_canonical_types_compatible_p (const_tree t1, const_tree t2,
      flexible array members, we allow mismatching modes for structures or
      unions.  */
   if (!RECORD_OR_UNION_TYPE_P (t1)
+      && TREE_CODE (t1) != ARRAY_TYPE
       && TYPE_MODE (t1) != TYPE_MODE (t2))
     return false;
 
@@ -14313,6 +14314,7 @@ verify_type (const_tree t)
 	 flexible array members.  */
       && !RECORD_OR_UNION_TYPE_P (t)
       && !RECORD_OR_UNION_TYPE_P (TYPE_CANONICAL (t))
+      && TREE_CODE (t) != ARRAY_TYPE
       && TYPE_MODE (t) != TYPE_MODE (TYPE_CANONICAL (t)))
     {
       error ("%<TYPE_MODE%> of %<TYPE_CANONICAL%> is not compatible");