--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/store_merging_25.c	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,75 @@
+/* PR tree-optimization/87859 */
+/* { dg-do run } */
+/* { dg-options "-O2 -fdump-tree-store-merging-details" } */
+/* { dg-final { scan-tree-dump "New sequence of \[23] stores to replace old one of 14 stores" "store-merging" { target i?86-*-* x86_64-*-* } } } */
+/* { dg-final { scan-tree-dump "New sequence of 1 stores to replace old one of 6 stores" "store-merging" { target i?86-*-* x86_64-*-* } } } */
+
+struct S {
+  union F {
+    struct T {
+#define A(n) unsigned n:1;
+#define B(n) A(n##0) A(n##1) A(n##2) A(n##3) A(n##4) \
+	     A(n##5) A(n##6) A(n##7) A(n##8) A(n##9)
+      B(f) B(f1) B(f2) B(f3) B(f4) B(f5)
+      A(f60) A(f61) A(f62) A(f63) A(f64) A(f65) A(f66)
+    } q;
+    unsigned int i[3];
+  } f;
+};
+
+struct S s = {
+  .f.q.f0 = 1, .f.q.f1 = 1, .f.q.f2 = 1, .f.q.f5 = 1, .f.q.f6 = 1,
+  .f.q.f7 = 1, .f.q.f8 = 1, .f.q.f9 = 1, .f.q.f13 = 1, .f.q.f14 = 1,
+  .f.q.f15 = 1, .f.q.f16 = 1, .f.q.f17 = 1, .f.q.f19 = 1, .f.q.f21 = 1,
+  .f.q.f66 = 1
+};
+
+__attribute__((noipa)) void
+bar (unsigned *x)
+{
+  if (x[0] != s.f.i[0] || x[1] != s.f.i[1] || x[2] != s.f.i[2])
+    __builtin_abort ();
+}
+
+__attribute__((noipa)) void
+foo (unsigned char *state, unsigned char c)
+{
+  struct S i;
+  i.f.i[0] = 0;
+  i.f.i[1] = 0;
+  i.f.i[2] = 0;
+  i.f.q.f7 = 1;
+  i.f.q.f2 = 1;
+  i.f.q.f21 = 1;
+  i.f.q.f19 = 1;
+  i.f.q.f14 = 1;
+  i.f.q.f5 = 1;
+  i.f.q.f0 = 1;
+  i.f.q.f15 = 1;
+  i.f.q.f16 = 1;
+  i.f.q.f6 = 1;
+  i.f.q.f9 = 1;
+  i.f.q.f17 = c;
+  i.f.q.f1 = 1;
+  i.f.q.f8 = 1;
+  i.f.q.f13 = 1;
+  i.f.q.f66 = 1;
+  if (*state)
+    {
+      i.f.q.f37 = 1;
+      i.f.q.f38 = 1;
+      i.f.q.f39 = 1;
+      i.f.q.f40 = 1;
+      i.f.q.f41 = 1;
+      i.f.q.f36 = 1;
+    }
+  bar (i.f.i);
+}
+
+int
+main ()
+{
+  unsigned char z = 0;
+  foo (&z, 1);
+  return 0;
+}