2011-10-26 Tom de Vries <tom@codesourcery.com>

	PR tree-optimization/50763
	* tree-ssa-tail-merge.c (replace_block_by): Update vops if phi_vuse1 or
	phi_vuse2 is NULL_TREE only if bb1 dominates or is dominated by bb2.

git-svn-id: svn+ssh://gcc.gnu.org/svn/gcc/trunk@180518 138bc75d-0d04-0410-961f-82ee72b054a4

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index a54e949..1a09dcc 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2011-10-26  Tom de Vries  <tom@codesourcery.com>
+
+       PR tree-optimization/50763
+       * tree-ssa-tail-merge.c (replace_block_by): Update vops if phi_vuse1 or
+       phi_vuse2 is NULL_TREE only if bb1 dominates or is dominated by bb2.
+
 2011-10-26  Richard Guenther  <rguenther@suse.de>
 
        PR lto/41844

diff --git a/gcc/tree-ssa-tail-merge.c b/gcc/tree-ssa-tail-merge.c
index f7b2f52..eb4bc92 100644 (file)
--- a/gcc/tree-ssa-tail-merge.c
+++ b/gcc/tree-ssa-tail-merge.c
@@ -1551,7 +1551,12 @@ replace_block_by (basic_block bb1, basic_block bb2, bool update_vops)
       phi_vuse1 = vop_at_entry (bb1);
 
       /* If both are not found, it means there's no need to update.  */
-      update_vops = phi_vuse1 != NULL_TREE || phi_vuse2 != NULL_TREE;
+      if (phi_vuse1 == NULL_TREE && phi_vuse2 == NULL_TREE)
+       update_vops = false;
+      else if (phi_vuse1 == NULL_TREE)
+       update_vops = dominated_by_p (CDI_DOMINATORS, bb1, bb2);
+      else if (phi_vuse2 == NULL_TREE)
+       update_vops = dominated_by_p (CDI_DOMINATORS, bb2, bb1);
     }
 
   if (phi_vuse1 && gimple_bb (SSA_NAME_DEF_STMT (phi_vuse1)) == bb1)