[PATCH] Fix PR61672

[Richard Biener <rguenther at suse dot de>]

When removing the MEM_ATTR unification hash I didn't grep for
MEM_ATTR equality comares which now causes PR61672, missed
optimizations at least in PRE.  The following fixes that by
exporting and using mem_attrs_eq_p.

Bootstrapped and tested on x86_64-unknown-linux-gnu - as this is
a regression on the 4.9 branch I'd like to eventually backport this.

Richard.

2014-08-05  Richard Biener  <rguenther@suse.de>

	PR rtl-optimization/61672
	* emit-rtl.h (mem_attrs_eq_p): Declare.
	* emit-rtl.c (mem_attrs_eq_p): Export.  Handle NULL mem-attrs.
	* cse.c (exp_equiv_p): Use mem_attrs_eq_p.
	* cfgcleanup.c (merge_memattrs): Likewise.
	Include emit-rtl.h.

Index: gcc/emit-rtl.h
===================================================================
--- gcc/emit-rtl.h	(revision 208113)
+++ gcc/emit-rtl.h	(working copy)
@@ -20,6 +20,9 @@ along with GCC; see the file COPYING3.
 #ifndef GCC_EMIT_RTL_H
 #define GCC_EMIT_RTL_H
 
+/* Return whether two MEM_ATTRs are equal.  */
+bool mem_attrs_eq_p (const struct mem_attrs *, const struct mem_attrs *);
+
 /* Set the alias set of MEM to SET.  */
 extern void set_mem_alias_set (rtx, alias_set_type);
 
Index: gcc/emit-rtl.c
===================================================================
--- gcc/emit-rtl.c	(revision 208113)
+++ gcc/emit-rtl.c	(working copy)
@@ -245,9 +245,13 @@ const_fixed_htab_eq (const void *x, cons
 
 /* Return true if the given memory attributes are equal.  */
 
-static bool
+bool
 mem_attrs_eq_p (const struct mem_attrs *p, const struct mem_attrs *q)
 {
+  if (p == q)
+    return true;
+  if (!p || !q)
+    return false;
   return (p->alias == q->alias
 	  && p->offset_known_p == q->offset_known_p
 	  && (!p->offset_known_p || p->offset == q->offset)
Index: gcc/cse.c
===================================================================
--- gcc/cse.c	(revision 208113)
+++ gcc/cse.c	(working copy)
@@ -2680,7 +2680,7 @@ exp_equiv_p (const_rtx x, const_rtx y, i
 	     But because really all MEM attributes should be the same for
 	     equivalent MEMs, we just use the invariant that MEMs that have
 	     the same attributes share the same mem_attrs data structure.  */
-	  if (MEM_ATTRS (x) != MEM_ATTRS (y))
+	  if (!mem_attrs_eq_p (MEM_ATTRS (x), MEM_ATTRS (y)))
 	    return 0;
 	}
       break;
Index: gcc/cfgcleanup.c
===================================================================
--- gcc/cfgcleanup.c	(revision 208113)
+++ gcc/cfgcleanup.c	(working copy)
@@ -53,6 +53,7 @@ along with GCC; see the file COPYING3.
 #include "df.h"
 #include "dce.h"
 #include "dbgcnt.h"
+#include "emit-rtl.h"
 
 #define FORWARDER_BLOCK_P(BB) ((BB)->flags & BB_FORWARDER_BLOCK)
 
@@ -882,7 +883,7 @@ merge_memattrs (rtx x, rtx y)
   if (GET_MODE (x) != GET_MODE (y))
     return;
 
-  if (code == MEM && MEM_ATTRS (x) != MEM_ATTRS (y))
+  if (code == MEM && !mem_attrs_eq_p (MEM_ATTRS (x), MEM_ATTRS (y)))
     {
       if (! MEM_ATTRS (x))
 	MEM_ATTRS (y) = 0;