re PR rtl-optimization/84003 (FAIL: g++.dg/torture/pr77745.C with noinline foo)

2018-01-26  Richard Biener  <rguenther@suse.de>

	PR rtl-optimization/84003
	* dse.c (record_store): Only record redundant stores when
	the earlier store aliases at least all accesses the later one does.

	* g++.dg/torture/pr77745.C: Mark foo noinline to trigger
	latent bug in DSE if NOINLINE is appropriately defined.
	* g++.dg/torture/pr77745-2.C: New testcase including pr77745.C
	and defining NOINLINE.

From-SVN: r257091

gcc/ChangeLog

+2018-01-26  Richard Biener  <rguenther@suse.de>
+
+	PR rtl-optimization/84003
+	* dse.c (record_store): Only record redundant stores when
+	the earlier store aliases at least all accesses the later one does.
+
 2018-01-26  Jakub Jelinek  <jakub@redhat.com>
 
 	PR rtl-optimization/83985

gcc/dse.c

@@ -1532,7 +1532,12 @@ record_store (rtx body, bb_info_t bb_info)
 	      && known_subrange_p (offset, width,
 				   s_info->offset, s_info->width)
 	      && all_positions_needed_p (s_info, offset - s_info->offset,
-					 width))
+					 width)
+	      /* We can only remove the later store if the earlier aliases
+		 at least all accesses the later one.  */
+	      && (MEM_ALIAS_SET (mem) == MEM_ALIAS_SET (s_info->mem)
+		  || alias_set_subset_of (MEM_ALIAS_SET (mem),
+					  MEM_ALIAS_SET (s_info->mem))))
 	    {
 	      if (GET_MODE (mem) == BLKmode)
 		{

gcc/testsuite/ChangeLog

+2018-01-26  Richard Biener  <rguenther@suse.de>
+
+	PR rtl-optimization/84003
+	* g++.dg/torture/pr77745.C: Mark foo noinline to trigger
+	latent bug in DSE if NOINLINE is appropriately defined.
+	* g++.dg/torture/pr77745-2.C: New testcase including pr77745.C
+	and defining NOINLINE.
+
 2018-01-26  Kyrylo Tkachov  <kyrylo.tkachov@arm.com>
 
 	* gcc.target/aarch64/advsimd-intrinsics/vld1x2.c: Make float64

gcc/testsuite/g++.dg/torture/pr77745-2.C

+// { dg-do run }
+
+#define NOINLINE __attribute__((noinline))
+#include "pr77745.C"

gcc/testsuite/g++.dg/torture/pr77745.C

 // { dg-do run }
 
+#ifndef NOINLINE
+#define NOINLINE /* */
+#endif
+
 inline void* operator new(__SIZE_TYPE__, void* __p) noexcept { return __p; }
 
-long foo(char *c1, char *c2)
+long NOINLINE foo(char *c1, char *c2)
 {
   long *p1 = new (c1) long;
   *p1 = 100;