2011-06-28 Kai Tietz <ktietz@redhat.com>

        * tree-ssa-math-opts.c (execute_optimize_bswap): Search
        within BB from last to first.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@175580 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 2e744e8..f655761 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2011-06-28  Kai Tietz  <ktietz@redhat.com>
+
+       * tree-ssa-math-opts.c (execute_optimize_bswap): Search
+       within BB from last to first.
+
 2011-06-28  Joseph Myers  <joseph@codesourcery.com>
 
        * genattr-common.c: New.  Based on genattr.c.

diff --git a/gcc/tree-ssa-math-opts.c b/gcc/tree-ssa-math-opts.c
index 4da4018..49ec360 100644 (file)
--- a/gcc/tree-ssa-math-opts.c
+++ b/gcc/tree-ssa-math-opts.c
@@ -1821,7 +1821,11 @@ execute_optimize_bswap (void)
     {
       gimple_stmt_iterator gsi;
 
-      for (gsi = gsi_after_labels (bb); !gsi_end_p (gsi); gsi_next (&gsi))
+      /* We do a reverse scan for bswap patterns to make sure we get the
+        widest match. As bswap pattern matching doesn't handle
+        previously inserted smaller bswap replacements as sub-
+        patterns, the wider variant wouldn't be detected.  */
+      for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi); gsi_prev (&gsi))
         {
          gimple stmt = gsi_stmt (gsi);
          tree bswap_src, bswap_type;