From: rth <rth@138bc75d-0d04-0410-961f-82ee72b054a4>
Date: Tue, 4 Sep 2012 18:17:54 +0000 (+0000)
Subject: * alias.c (read_dependence): Return true for ALIAS_SET_MEMORY_BARRIER.
X-Git-Url: http://git.sourceforge.jp/view?p=pf3gnuchains%2Fgcc-fork.git;a=commitdiff_plain;h=9cd23f0de3394747ac2c2c4a2e8401ef0194032e

* alias.c (read_dependence): Return true for ALIAS_SET_MEMORY_BARRIER.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/branches/gcc-4_7-branch@190942 138bc75d-0d04-0410-961f-82ee72b054a4
---

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 0b7ba90b188..e71ab917a61 100644
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,7 @@
+2012-09-04  Richard Henderson  <rth@redhat.com>
+
+	* alias.c (read_dependence): Return true for ALIAS_SET_MEMORY_BARRIER.
+
 2012-09-04  Georg-Johann Lay  <avr@gjlay.de>
 
 	Backport from 2012-09-04 mainline r190920
diff --git a/gcc/alias.c b/gcc/alias.c
index e9d701f9636..f20716d0dff 100644
--- a/gcc/alias.c
+++ b/gcc/alias.c
@@ -2127,12 +2127,18 @@ memrefs_conflict_p (int xsize, rtx x, int ysize, rtx y, HOST_WIDE_INT c)
    storeqi_unaligned pattern.  */
 
 /* Read dependence: X is read after read in MEM takes place.  There can
-   only be a dependence here if both reads are volatile.  */
+   only be a dependence here if both reads are volatile, or if either is
+   an explicit barrier.  */
 
 int
 read_dependence (const_rtx mem, const_rtx x)
 {
-  return MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem);
+  if (MEM_VOLATILE_P (x) && MEM_VOLATILE_P (mem))
+    return true;
+  if (MEM_ALIAS_SET (x) == ALIAS_SET_MEMORY_BARRIER
+      || MEM_ALIAS_SET (mem) == ALIAS_SET_MEMORY_BARRIER)
+    return true;
+  return false;
 }
 
 /* Returns nonzero if something about the mode or address format MEM1