tree-ssa-propagate.c (cfg_blocks_add): Insert blocks with fewer predecessors at head...

	* tree-ssa-propagate.c (cfg_blocks_add): Insert blocks with fewer
	predecessors at head rather than tail.

From-SVN: r123906

diff --git a/gcc/ChangeLog b/gcc/ChangeLog
index 8575622bd87824255cc421178b57c051fe9c050e..a9f1ca548d28556e0b07aa1b0e54386902729837 100644 (file)
--- a/gcc/ChangeLog
+++ b/gcc/ChangeLog
@@ -1,3 +1,8 @@
+2007-04-16  Ian Lance Taylor  <iant@google.com>
+
+       * tree-ssa-propagate.c (cfg_blocks_add): Insert blocks with fewer
+       predecessors at head rather than tail.
+
 2007-04-16  Matthias Klose  <doko@debian.org>
 
        * gcc/config/alpha/linux.h (CPP_SPEC): Define.

diff --git a/gcc/tree-ssa-propagate.c b/gcc/tree-ssa-propagate.c
index 1981fa1783be6c9c352eaba1d6762a2f33b28e4d..df31e25f8ff1c65e6343423e49e395d2fbdeaf2c 100644 (file)
--- a/gcc/tree-ssa-propagate.c
+++ b/gcc/tree-ssa-propagate.c
@@ -1,5 +1,5 @@
 /* Generic SSA value propagation engine.
-   Copyright (C) 2004, 2005, 2006 Free Software Foundation, Inc.
+   Copyright (C) 2004, 2005, 2006, 2007 Free Software Foundation, Inc.
    Contributed by Diego Novillo <dnovillo@redhat.com>
 
    This file is part of GCC.
@@ -176,6 +176,8 @@ cfg_blocks_empty_p (void)
 static void 
 cfg_blocks_add (basic_block bb)
 {
+  bool head = false;
+
   gcc_assert (bb != ENTRY_BLOCK_PTR && bb != EXIT_BLOCK_PTR);
   gcc_assert (!TEST_BIT (bb_in_list, bb->index));
 
@@ -198,12 +200,26 @@ cfg_blocks_add (basic_block bb)
          cfg_blocks_head = 0;
          VEC_safe_grow (basic_block, heap, cfg_blocks, 2 * cfg_blocks_tail);
        }
-      else
+      /* Minor optimization: we prefer to see blocks with more
+        predecessors later, because there is more of a chance that
+        the incoming edges will be executable.  */
+      else if (EDGE_COUNT (bb->preds)
+              >= EDGE_COUNT (VEC_index (basic_block, cfg_blocks,
+                                        cfg_blocks_head)->preds))
        cfg_blocks_tail = ((cfg_blocks_tail + 1)
                           % VEC_length (basic_block, cfg_blocks));
+      else
+       {
+         if (cfg_blocks_head == 0)
+           cfg_blocks_head = VEC_length (basic_block, cfg_blocks);
+         --cfg_blocks_head;
+         head = true;
+       }
     }
 
-  VEC_replace (basic_block, cfg_blocks, cfg_blocks_tail, bb);
+  VEC_replace (basic_block, cfg_blocks,
+              head ? cfg_blocks_head : cfg_blocks_tail,
+              bb);
   SET_BIT (bb_in_list, bb->index);
 }