--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/store_merging_20.c	Thu Oct 25 07:37:49 2018 +0900
@@ -0,0 +1,68 @@
+/* { dg-do run } */
+/* { dg-require-effective-target store_merge } */
+/* { dg-options "-O2 -fdump-tree-store-merging" } */
+
+extern void abort (void);
+
+struct S1 {
+  unsigned int flag : 1;
+  unsigned int size : 31;
+};
+
+__attribute__((noipa))
+void foo1 (struct S1 *s, unsigned int size)
+{
+  s->flag = 1;
+  s->size = size & 0x7FFFFFFF;
+}
+
+struct S2 {
+  unsigned int flag : 1;
+  unsigned int size : 15;
+  unsigned short count;
+};
+
+__attribute__((noipa))
+void foo2 (struct S2 *s, unsigned short size)
+{
+  s->flag = 1;
+  s->size = size;
+  s->count = 0xABCD;
+}
+
+struct S3 {
+  unsigned int n1 : 4;
+  unsigned int c  : 8;
+  unsigned int n2 : 4;
+};
+
+__attribute__((noipa))
+void foo3 (struct S3 *s, unsigned char n1, unsigned char c, unsigned char n2)
+{
+  s->n1 = n1 & 0xF;
+  s->n2 = n2 & 0xF;
+  s->c = c;
+}
+
+int main (void)
+{
+  struct S1 s1;
+  struct S2 s2;
+  struct S3 s3;
+
+  foo1 (&s1, 0x12345678);
+  if (s1.flag != 1 || s1.size != 0x12345678)
+    abort ();
+
+  foo2 (&s2, 0x1234);
+  if (s2.flag != 1 || s2.size != 0x1234 || s2.count != 0xABCD)
+    abort ();
+
+  foo3 (&s3, 0x12, 0x34, 0x56);
+  if (s3.n1 != 0x2 || s3.c != 0x34 || s3.n2 != 0x6)
+    abort ();
+
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "Merging successful" 3 "store-merging" } } */