Daily bump.

[pf3gnuchains/gcc-fork.git] / gcc / tree-ssa-loop-ivopts.c

diff --git a/gcc/tree-ssa-loop-ivopts.c b/gcc/tree-ssa-loop-ivopts.c
index 436e6ce..e6565db 100644 (file)
--- a/gcc/tree-ssa-loop-ivopts.c
+++ b/gcc/tree-ssa-loop-ivopts.c
@@ -1,5 +1,5 @@
 /* Induction variable optimizations.
-   Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009
+   Copyright (C) 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010
    Free Software Foundation, Inc.
 
 This file is part of GCC.
@@ -4089,6 +4089,7 @@ determine_use_iv_cost_condition (struct ivopts_data *data,
   bitmap depends_on_elim = NULL, depends_on_express = NULL, depends_on;
   comp_cost elim_cost, express_cost, cost;
   bool ok;
+  tree *control_var, *bound_cst;
 
   /* Only consider real candidates.  */
   if (!cand->iv)
@@ -4110,9 +4111,22 @@ determine_use_iv_cost_condition (struct ivopts_data *data,
 
   /* Try expressing the original giv.  If it is compared with an invariant,
      note that we cannot get rid of it.  */
-  ok = extract_cond_operands (data, use->stmt, NULL, NULL, NULL, &cmp_iv);
+  ok = extract_cond_operands (data, use->stmt, &control_var, &bound_cst,
+                             NULL, &cmp_iv);
   gcc_assert (ok);
 
+  /* When the condition is a comparison of the candidate IV against
+     zero, prefer this IV.
+
+     TODO: The constant that we're substracting from the cost should
+     be target-dependent.  This information should be added to the
+     target costs for each backend.  */
+  if (!infinite_cost_p (elim_cost) /* Do not try to decrease infinite! */
+      && integer_zerop (*bound_cst)
+      && (operand_equal_p (*control_var, cand->var_after, 0)
+         || operand_equal_p (*control_var, cand->var_before, 0)))
+    elim_cost.cost -= 1;
+
   express_cost = get_computation_cost (data, use, cand, false,
                                       &depends_on_express, NULL);
   fd_ivopts_data = data;