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Fix PR 31521


I've applied and tested Andrew Pinski's patch for PR 31521.  We were
missing an opportunity to convert a division into a shift because the
predicate test was too strict.

Bootstrapped and tested on x86_64, x86 and ppc64.
2007-08-02  Andrew Pinski  <andrew_pinski@playstation.sony.com>
            Diego Novillo  <dnovillo@google.com>

	PR 31521
	* tree-vrp.c (simplify_div_or_mod_using_ranges): Also simplify
	if the range includes 0.

testsuite/ChangeLog

	PR 31521
	* gcc.dg/tree-ssa/pr31521.c: New test.

Index: tree-vrp.c
===================================================================
--- tree-vrp.c	(revision 127174)
+++ tree-vrp.c	(working copy)
@@ -5541,7 +5541,7 @@ simplify_div_or_mod_using_ranges (tree s
     {
       bool sop = false;
 
-      val = compare_range_with_value (GT_EXPR, vr, integer_zero_node, &sop);
+      val = compare_range_with_value (GE_EXPR, vr, integer_zero_node, &sop);
 
       if (val
 	  && sop
Index: testsuite/gcc.dg/tree-ssa/pr31521.c
===================================================================
--- testsuite/gcc.dg/tree-ssa/pr31521.c	(revision 0)
+++ testsuite/gcc.dg/tree-ssa/pr31521.c	(revision 0)
@@ -0,0 +1,20 @@
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-vrp1" } */
+
+void fail(void) __attribute__((noreturn));
+int bar(int);
+
+int foo(int x) {
+  int i;
+  int s = 0;
+
+  if (x <= 0) fail();
+  for (i = 0; i < x; ++i) {
+    /* This division by 4 should be replaced with >> 2.  */
+    s += bar(i/4);
+  }
+  return s;
+}
+
+/* { dg-final { scan-tree-dump-times " = i_.* >> 2" 1 "vrp1" } } */
+/* { dg-final { cleanup-tree-dump "vrp1" } } */

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