re PR tree-optimization/20657 ([tcb] VRP does not get rid of a redundant "if" statement.)

gcc/
	PR tree-optimization/20657
	* tree-vrp.c (extract_range_from_expr): Notice INTEGER_CST to
	create an appropriate range from it.

testsuite/
	PR tree-optimization/20657
	* gcc.dg/tree-ssa/pr20657.c: New.

From-SVN: r98134

gcc/ChangeLog

+2005-04-14  Kazu Hirata  <kazu@cs.umass.edu>
+
+	PR tree-optimization/20657
+	* tree-vrp.c (extract_range_from_expr): Notice INTEGER_CST to
+	create an appropriate range from it.
+
 2005-04-14  Uros Bizjak  <uros@kss-loka.si>
 
 	* reg-stack.c (subst_stack_regs_pat): Handle <UNSPEC_FIST_FLOOR> and

gcc/testsuite/ChangeLog

+2005-04-14  Kazu Hirata  <kazu@cs.umass.edu>
+
+	PR tree-optimization/20657
+	* gcc.dg/tree-ssa/pr20657.c: New.
+
 2005-04-14  Uros Bizjak  <uros@kss-loka.si>
 
 	* gcc.dg/builtins-53.c: Also check (int)trunc* and

gcc/testsuite/gcc.dg/tree-ssa/pr20657.c

+/* PR tree-optimization/20657
+   VRP did not pick up a conditional equivalence from the first "if"
+   statement, which was needed to eliminate the second "if" statement.  */
+
+/* { dg-do compile } */
+/* { dg-options "-O2 -fno-tree-dominator-opts -fdump-tree-vrp-details" } */
+
+int
+foo (int a)
+{
+  if (a == 0)
+    if (a == 0)
+      return 1;
+  return 0;
+}
+
+/* { dg-final { scan-tree-dump-times "Folding predicate" 1 "vrp"} } */

gcc/tree-vrp.c

@@ -830,6 +830,8 @@ extract_range_from_expr (value_range *vr, tree expr)
     extract_range_from_unary_expr (vr, expr);
   else if (expr_computes_nonzero (expr))
     set_value_range_to_nonnull (vr, TREE_TYPE (expr));
+  else if (TREE_CODE (expr) == INTEGER_CST)
+    set_value_range (vr, VR_RANGE, expr, expr);
   else
     set_value_range (vr, VR_VARYING, NULL_TREE, NULL_TREE);
 }