re PR tree-optimization/40579 (gcc -O2 optimization causes infinite loop and wrong output)

2009-06-29  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/40579
	* tree-vrp.c (vrp_evaluate_conditional): Bail out early if
	the IL to simplify has constants that overflowed.

	* gcc.c-torture/execute/pr40579.c: New testcase.

From-SVN: r149046

gcc/ChangeLog

+2009-06-29  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/40579
+	* tree-vrp.c (vrp_evaluate_conditional): Bail out early if
+	the IL to simplify has constants that overflowed.
+
 2009-06-28  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR tree-optimization/40550

gcc/testsuite/ChangeLog

+2009-06-29  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/40579
+	* gcc.c-torture/execute/pr40579.c: New testcase.
+
 2009-06-28  Uros Bizjak  <ubizjak@gmail.com>
 
 	PR tree-optimization/40550

gcc/testsuite/gcc.c-torture/execute/pr40579.c

+extern void abort (void);
+static char * __attribute__((noinline))
+itos(int num)
+{
+  return (char *)0;
+}
+static void __attribute__((noinline))
+foo(int i, const char *x)
+{
+  if (i >= 4)
+    abort ();
+}
+int main()
+{
+  int x = -__INT_MAX__ + 3;
+  int i;
+
+  for (i = 0; i < 4; ++i)
+    {
+      char *p;
+      --x;
+      p = itos(x);
+      foo(i, p);
+    }
+
+  return 0;
+}
+

gcc/tree-vrp.c

@@ -5679,6 +5679,14 @@ vrp_evaluate_conditional (enum tree_code code, tree op0, tree op1, gimple stmt)
   tree ret;
   bool only_ranges;
 
+  /* Some passes and foldings leak constants with overflow flag set
+     into the IL.  Avoid doing wrong things with these and bail out.  */
+  if ((TREE_CODE (op0) == INTEGER_CST
+       && TREE_OVERFLOW (op0))
+      || (TREE_CODE (op1) == INTEGER_CST
+	  && TREE_OVERFLOW (op1)))
+    return NULL_TREE;
+
   sop = false;
   ret = vrp_evaluate_conditional_warnv_with_ops (code, op0, op1, true, &sop,
   						 &only_ranges);