tree-ssa-forwprop.c (ssa_forward_propagate_and_combine): Scan stmts forward when...

2011-06-10  Richard Guenther  <rguenther@suse.de>

	* tree-ssa-forwprop.c (ssa_forward_propagate_and_combine):
	Scan stmts forward when combining, visit inserted stmts when
	a stmt was changed.

From-SVN: r174900

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index fa56bf092b5a50801a64c387f7aa5bad816dadf5..ec2d7e9f0e265b8f39f4c2a6d2b800b14836cc80 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,9 @@
+2011-06-10  Richard Guenther  <rguenther@suse.de>
+
+       * tree-ssa-forwprop.c (ssa_forward_propagate_and_combine):
+       Scan stmts forward when combining, visit inserted stmts when
+       a stmt was changed.
+
 2011-06-10  Paolo Carlini  <paolo.carlini@oracle.com>
 
        * tree.h (error_operand_p): Add.

diff --git a/gcc/tree-ssa-forwprop.c b/gcc/tree-ssa-forwprop.c
index 56ba5226af400275f7ed25a5b392487145ffe88d..77a6264d560bbdb90982782e041240fbe295a6c9 100644 (file)
--- a/gcc/tree-ssa-forwprop.c
+++ b/gcc/tree-ssa-forwprop.c
@@ -2212,7 +2212,8 @@ ssa_forward_propagate_and_combine (void)
 
   FOR_EACH_BB (bb)
     {
-      gimple_stmt_iterator gsi;
+      gimple_stmt_iterator gsi, prev;
+      bool prev_initialized;
 
       /* Apply forward propagation to all stmts in the basic-block.
         Note we update GSI within the loop as necessary.  */
@@ -2304,7 +2305,8 @@ ssa_forward_propagate_and_combine (void)
 
       /* Combine stmts with the stmts defining their operands.
         Note we update GSI within the loop as necessary.  */
-      for (gsi = gsi_last_bb (bb); !gsi_end_p (gsi);)
+      prev_initialized = false;
+      for (gsi = gsi_start_bb (bb); !gsi_end_p (gsi);)
        {
          gimple stmt = gsi_stmt (gsi);
          bool changed = false;
@@ -2386,9 +2388,24 @@ ssa_forward_propagate_and_combine (void)
            default:;
            }
 
-         /* If the stmt changed try combining it again.  */
-         if (!changed)
-           gsi_prev (&gsi);
+         if (changed)
+           {
+             /* If the stmt changed then re-visit it and the statements
+                inserted before it.  */
+             if (!prev_initialized)
+               gsi = gsi_start_bb (bb);
+             else
+               {
+                 gsi = prev;
+                 gsi_next (&gsi);
+               }
+           }
+         else
+           {
+             prev = gsi;
+             prev_initialized = true;
+             gsi_next (&gsi);
+           }
        }
     }