[gcc r12-2755] Fix oversight in handling of reverse SSO in SRA pass

[gcc r12-2755] Fix oversight in handling of reverse SSO in SRA pass

[Eric Botcazou]

https://gcc.gnu.org/g:4e3129b0caceec008a940aa5eada253cd0f0b3ec

commit r12-2755-g4e3129b0caceec008a940aa5eada253cd0f0b3ec
Author: Eric Botcazou <ebotcazou@gcc.gnu.org>
Date:   Thu Aug 5 10:21:30 2021 +0200

    Fix oversight in handling of reverse SSO in SRA pass
    
    The scalar storage order does not apply to pointer and vector components.
    
    gcc/
            PR tree-optimization/101626
            * tree-sra.c (propagate_subaccesses_from_rhs): Do not set the
            reverse scalar storage order on a pointer or vector component.
    
    gcc/testsuite/
            * gcc.dg/sso-15.c: New test.

Diff:
---
 gcc/testsuite/gcc.dg/sso-15.c | 36 ++++++++++++++++++++++++++++++++++++
 gcc/tree-sra.c                |  5 ++++-
 2 files changed, 40 insertions(+), 1 deletion(-)

diff --git a/gcc/testsuite/gcc.dg/sso-15.c b/gcc/testsuite/gcc.dg/sso-15.c
new file mode 100644
index 00000000000..d8a711d6576
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/sso-15.c
@@ -0,0 +1,36 @@
+/* { dg-do compile } */
+/* { dg-options "-O2" } */
+
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+#define REV_ENDIANNESS __attribute__((scalar_storage_order("big-endian")))
+#else
+#define REV_ENDIANNESS __attribute__((scalar_storage_order("little-endian")))
+#endif
+
+struct X { int *p; } REV_ENDIANNESS;
+
+struct X x;
+
+struct X __attribute__((noinline)) foo (int *p)
+{
+  struct X x;
+  x.p = p;
+  return x;
+}
+
+void __attribute((noinline)) bar (void)
+{
+  *x.p = 1;
+}
+
+extern void abort (void);
+
+int main (void)
+{
+  int i = 0;
+  x = foo(&i);
+  bar();
+  if (i != 1)
+    abort ();
+  return 0;
+}
diff --git a/gcc/tree-sra.c b/gcc/tree-sra.c
index c05d22f3e8f..3a9e14f50a0 100644
--- a/gcc/tree-sra.c
+++ b/gcc/tree-sra.c
@@ -2790,7 +2790,10 @@ propagate_subaccesses_from_rhs (struct access *lacc, struct access *racc)
 	{
 	  /* We are about to change the access type from aggregate to scalar,
 	     so we need to put the reverse flag onto the access, if any.  */
-	  const bool reverse = TYPE_REVERSE_STORAGE_ORDER (lacc->type);
+	  const bool reverse
+	    = TYPE_REVERSE_STORAGE_ORDER (lacc->type)
+	      && !POINTER_TYPE_P (racc->type)
+	      && !VECTOR_TYPE_P (racc->type);
 	  tree t = lacc->base;
 
 	  lacc->type = racc->type;