[PATCH] PR86844: Fix for store merging

[Andreas Krebbel <krebbel@linux.ibm.com>]

From: Andreas Krebbel <krebbel@linux.vnet.ibm.com>

Bootstrapped and regtested on s390x and x86_64.

gcc/ChangeLog:

2018-08-07  Andreas Krebbel  <krebbel@linux.ibm.com>

	PR tree-optimization/86844
	* gimple-ssa-store-merging.c (check_no_overlap): Add a check to
	reject overlaps if it has seen a non-constant store in between.

gcc/testsuite/ChangeLog:

2018-08-07  Andreas Krebbel  <krebbel@linux.ibm.com>

	PR tree-optimization/86844
	* gcc.dg/pr86844.c: New test.
---
 gcc/gimple-ssa-store-merging.c |  8 +++++++-
 gcc/testsuite/gcc.dg/pr86844.c | 42 ++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 49 insertions(+), 1 deletion(-)
 create mode 100644 gcc/testsuite/gcc.dg/pr86844.c

diff --git a/gcc/gimple-ssa-store-merging.c b/gcc/gimple-ssa-store-merging.c
index 0ae4581..2abef2e 100644
--- a/gcc/gimple-ssa-store-merging.c
+++ b/gcc/gimple-ssa-store-merging.c
@@ -2401,13 +2401,19 @@ check_no_overlap (vec<store_immediate_info *> m_store_info, unsigned int i,
 		  unsigned HOST_WIDE_INT end)
 {
   unsigned int len = m_store_info.length ();
+  bool seen_group_end_store_p = false;
+
   for (++i; i < len; ++i)
     {
       store_immediate_info *info = m_store_info[i];
       if (info->bitpos >= end)
 	break;
+      if (info->rhs_code != INTEGER_CST)
+	seen_group_end_store_p = true;
       if (info->order < last_order
-	  && (rhs_code != INTEGER_CST || info->rhs_code != INTEGER_CST))
+	  && (rhs_code != INTEGER_CST
+	      || info->rhs_code != INTEGER_CST
+	      || seen_group_end_store_p))
 	return false;
     }
   return true;
diff --git a/gcc/testsuite/gcc.dg/pr86844.c b/gcc/testsuite/gcc.dg/pr86844.c
new file mode 100644
index 0000000..9ef08e9
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/pr86844.c
@@ -0,0 +1,42 @@
+/* { dg-do run } */
+/* { dg-require-effective-target stdint_types } */
+/* { dg-options "-O1 -fstore-merging" } */
+
+#include <stdint.h>
+
+struct foo
+{
+  union
+  {
+    uint32_t u4i;
+
+    struct
+    {
+      uint8_t x;
+      uint8_t y;
+      uint8_t z;
+      uint8_t w;
+    } s;
+  } u;
+  uint8_t v;
+};
+
+void __attribute__((noinline,noclone))
+f (struct foo *a)
+{
+  a->u.u4i = 0;
+  a->u.s.w = 222;
+  a->u.s.y = 129;
+  a->u.s.z = a->v;
+}
+
+int
+main ()
+{
+  struct foo s;
+
+  f (&s);
+
+  if (s.u.s.w != 222)
+    __builtin_abort ();
+}
-- 
2.9.1