[PATCH] C-amily: Properly strip NOP_EXPR

[H.J. Lu]

gcc/c-family/

	PR c/51628
	* c-warn.c (warn_for_address_or_pointer_of_packed_member): Move
	NOP_EXPR check to ...
	(check_and_warn_address_of_packed_member): Here.

gcc/testsuite/

	PR c/51628
	* c-c++-common/pr51628-33.c: New test.
---
 gcc/c-family/c-warn.c                   |  6 +++---
 gcc/testsuite/c-c++-common/pr51628-33.c | 19 +++++++++++++++++++
 2 files changed, 22 insertions(+), 3 deletions(-)
 create mode 100644 gcc/testsuite/c-c++-common/pr51628-33.c

diff --git a/gcc/c-family/c-warn.c b/gcc/c-family/c-warn.c
index 79b2d8ad449..070934ab2b6 100644
--- a/gcc/c-family/c-warn.c
+++ b/gcc/c-family/c-warn.c
@@ -2755,6 +2755,9 @@ check_and_warn_address_of_packed_member (tree type, tree rhs)
       while (TREE_CODE (rhs) == COMPOUND_EXPR)
 	rhs = TREE_OPERAND (rhs, 1);
 
+      if (TREE_CODE (rhs) == NOP_EXPR)
+	rhs = TREE_OPERAND (rhs, 0);
+
       tree context = check_address_of_packed_member (type, rhs);
       if (context)
 	{
@@ -2844,9 +2847,6 @@ warn_for_address_or_pointer_of_packed_member (bool convert_p, tree type,
       /* Get the type of the pointer pointing to.  */
       type = TREE_TYPE (type);
 
-      if (TREE_CODE (rhs) == NOP_EXPR)
-	rhs = TREE_OPERAND (rhs, 0);
-
       check_and_warn_address_of_packed_member (type, rhs);
     }
 }
diff --git a/gcc/testsuite/c-c++-common/pr51628-33.c b/gcc/testsuite/c-c++-common/pr51628-33.c
new file mode 100644
index 00000000000..0092f32202f
--- /dev/null
+++ b/gcc/testsuite/c-c++-common/pr51628-33.c
@@ -0,0 +1,19 @@
+/* PR c/51628.  */
+/* { dg-do compile } */
+/* { dg-options "-O" } */
+
+struct pair_t
+{
+  char x;
+  int i[4];
+} __attribute__ ((packed, aligned (4)));
+
+extern struct pair_t p;
+extern void bar (int *);
+
+void
+foo (struct pair_t *p)
+{
+  bar (p ? p->i : (int *) 0);
+/* { dg-warning "may result in an unaligned pointer value" "" { target *-*-* } .-1 } */
+}
-- 
2.20.1