re PR tree-optimization/21001 (VRP is weak when the tested variable in a…

re PR tree-optimization/21001 (VRP is weak when the tested variable in a COND_EXPR is used only in the COND_EXPR.)

gcc/
	PR tree-optimization/21001
	* tree-optimize.c (init_tree_optimization_passes): Move the
	first pass_forwprop immediately before pass_vrp.

testsuite/
	PR tree-optimization/21001
	* gcc.dg/tree-ssa/pr21001.c: New.

From-SVN: r98309

gcc/ChangeLog

+2005-04-18  Kazu Hirata  <kazu@cs.umass.edu>
+
+	PR tree-optimization/21001
+	* tree-optimize.c (init_tree_optimization_passes): Move the
+	first pass_forwprop immediately before pass_vrp.
+
 2005-04-17  Ian Lance Taylor  <ian@airs.com>
 
 	* c-common.def (SIZEOF_EXPR, ARROW_EXPR, ALIGNOF_EXPR): Remove.

gcc/testsuite/ChangeLog

+2005-04-18  Kazu Hirata  <kazu@cs.umass.edu>
+
+	PR tree-optimization/21001
+	* gcc.dg/tree-ssa/pr21001.c: New.
+
 2005-04-17  Thomas Koenig  <Thomas.Koenig@online.de>
 
 	PR libfortran/21075

gcc/testsuite/gcc.dg/tree-ssa/pr21001.c

+/* PR tree-optimization/21001
+   VRP did not insert ASSERT_EXPRs when the variable tested in a
+   COND_EXPR is a single-use variable.  By propagating the definition
+   of the single-use variable into the COND_EXPR, we can get useful
+   range infomation out of the conditional.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-tree-dominator-opts -fdump-tree-vrp-details" } */
+
+int
+foo (int a)
+{
+  int b = a != 0;
+  if (b)
+    if (a != 0)
+      return 1;
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "Folding predicate" 1 "vrp"} } */

gcc/tree-optimize.c

@@ -356,9 +356,9 @@ init_tree_optimization_passes (void)
   NEXT_PASS (pass_dominator);
   NEXT_PASS (pass_copy_prop);
   NEXT_PASS (pass_dce);
+  NEXT_PASS (pass_forwprop);
   NEXT_PASS (pass_vrp);
   NEXT_PASS (pass_merge_phi);
-  NEXT_PASS (pass_forwprop);
   NEXT_PASS (pass_phiopt);
   NEXT_PASS (pass_may_alias);
   NEXT_PASS (pass_tail_recursion);