From: Eric Botcazou <ebotcazou@adacore.com>
Date: Fri, 7 May 2021 18:44:36 +0000 (+0200)
Subject: Do not apply scalar storage order to pointer fields
X-Git-Tag: basepoints/gcc-13~7691
X-Git-Url: http://git.ipfire.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=e2bc5b6c04df820017c497a2578bd3c4c7b6c89b;p=thirdparty%2Fgcc.git

Do not apply scalar storage order to pointer fields

Pointer fields (and vector fields originally) were not really considered
when the scalar_storage_order attribute, so they are swapped as well.
As pointed out, this is problematic to describe in DWARF and probably
not very useful in any case, so this pulls them out.

gcc/
	* doc/extend.texi (scalar_storage_order): Mention effect on pointer
	and vector fields.
	* tree.h (reverse_storage_order_for_component_p): Return false if
	the type is a pointer.
gcc/c/
	* c-typeck.c (build_unary_op) <ADDR_EXPR>: Do not issue an error
	on the address of a pointer field in a record with reverse SSO.
gcc/testsuite/
	* gcc.dg/sso-12.c: New test.
---

diff --git a/gcc/c/c-typeck.c b/gcc/c/c-typeck.c
index fdc7bb6125c2..5bdc673d03a8 100644
--- a/gcc/c/c-typeck.c
+++ b/gcc/c/c-typeck.c
@@ -4866,6 +4866,7 @@ build_unary_op (location_t location, enum tree_code code, tree xarg,
 	  if (TYPE_REVERSE_STORAGE_ORDER (TREE_TYPE (TREE_OPERAND (arg, 0))))
 	    {
 	      if (!AGGREGATE_TYPE_P (TREE_TYPE (arg))
+		  && !POINTER_TYPE_P (TREE_TYPE (arg))
 		  && !VECTOR_TYPE_P (TREE_TYPE (arg)))
 		{
 		  error_at (location, "cannot take address of scalar with "
diff --git a/gcc/doc/extend.texi b/gcc/doc/extend.texi
index c8caf36f2930..fd9175d1b3bb 100644
--- a/gcc/doc/extend.texi
+++ b/gcc/doc/extend.texi
@@ -8551,6 +8551,9 @@ or an array whose component is a @code{union} or a @code{struct}, and it is
 possible for these fields to have a different scalar storage order than the
 enclosing type.
 
+Note that neither pointer nor vector fields are considered scalar fields in
+this context, so the attribute has no effects on these fields.
+
 This attribute is supported only for targets that use a uniform default
 scalar storage order (fortunately, most of them), i.e.@: targets that store
 the scalars either all in big-endian or all in little-endian.
diff --git a/gcc/testsuite/gcc.dg/sso-12.c b/gcc/testsuite/gcc.dg/sso-12.c
new file mode 100644
index 000000000000..3bed280e1734
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/sso-12.c
@@ -0,0 +1,27 @@
+/* Test scalar_storage_order attribute and pointer fields */
+
+/* { dg-do run } */
+/* { dg-options "-Wno-pedantic" } */
+
+#if __BYTE_ORDER__ == __ORDER_LITTLE_ENDIAN__
+struct __attribute__((scalar_storage_order("big-endian"))) Rec
+{
+  int *p;
+};
+#else
+struct __attribute__((scalar_storage_order("little-endian"))) Rec
+{
+  int *p;
+};
+#endif
+
+int main (int argc)
+{
+  struct Rec r = { &argc };
+  int *p = &argc;
+
+  if (__builtin_memcmp (&r.p, &p, sizeof (int *)) != 0)
+    __builtin_abort ();
+
+  return 0;
+}
diff --git a/gcc/tree.h b/gcc/tree.h
index 6d3cfc4c588e..784452ca490e 100644
--- a/gcc/tree.h
+++ b/gcc/tree.h
@@ -4989,7 +4989,9 @@ static inline bool
 reverse_storage_order_for_component_p (tree t)
 {
   /* The storage order only applies to scalar components.  */
-  if (AGGREGATE_TYPE_P (TREE_TYPE (t)) || VECTOR_TYPE_P (TREE_TYPE (t)))
+  if (AGGREGATE_TYPE_P (TREE_TYPE (t))
+      || POINTER_TYPE_P (TREE_TYPE (t))
+      || VECTOR_TYPE_P (TREE_TYPE (t)))
     return false;
 
   if (TREE_CODE (t) == REALPART_EXPR || TREE_CODE (t) == IMAGPART_EXPR)