re PR tree-optimization/49218 (Incorrect optimization of a 'for' loop creates an infinite loop)

2011-05-30  Richard Guenther  <rguenther@suse.de>

	PR tree-optimization/49218
	* tree-vrp.c (adjust_range_with_scev): Properly check whether
	overflow occured.

	* gcc.c-torture/execute/pr49218.c: New testcase.

From-SVN: r174429

gcc/ChangeLog

 2011-05-30  Richard Guenther  <rguenther@suse.de>
 
+	PR tree-optimization/49218
+	* tree-vrp.c (adjust_range_with_scev): Properly check whether
+	overflow occured.
+
+2011-05-30  Richard Guenther  <rguenther@suse.de>
+
 	* tree-ssa-forwprop.c (forward_propagate_into_comparison):
 	New function split out from ...
 	(forward_propagate_into_gimple_cond): ... here.  Adjust.

gcc/testsuite/ChangeLog

+2011-05-30  Richard Guenther  <rguenther@suse.de>
+
+	PR tree-optimization/49218
+	* gcc.c-torture/execute/pr49218.c: New testcase.
+
 2011-05-30  Ira Rosen  <ira.rosen@linaro.org>
 
 	PR tree-optimization/49199

gcc/testsuite/gcc.c-torture/execute/pr49218.c

+#ifdef __SIZEOF_INT128__
+typedef __int128 L;
+#else
+typedef long long L;
+#endif
+float f;
+
+int
+main ()
+{
+  L i = f;
+  if (i <= 10)
+    do
+      {
+	++i;
+	asm ("");
+      }
+    while (i != 11);
+  return 0;
+}

gcc/tree-vrp.c

@@ -3423,11 +3423,17 @@ adjust_range_with_scev (value_range_t *vr, struct loop *loop,
                                            loop->nb_iterations_upper_bound,
                                            double_int_one),
                                        unsigned_p, &overflow);
-      tem = double_int_to_tree (TREE_TYPE (init), dtmp);
       /* If the multiplication overflowed we can't do a meaningful
-	 adjustment.  */
-      if (!overflow && double_int_equal_p (dtmp, tree_to_double_int (tem)))
-	{
+	 adjustment.  Likewise if the result doesn't fit in the type
+	 of the induction variable.  For a signed type we have to
+	 check whether the result has the expected signedness which
+	 is that of the step as nb_iterations_upper_bound is unsigned.  */
+      if (!overflow
+	  && double_int_fits_to_tree_p (TREE_TYPE (init), dtmp)
+	  && (unsigned_p
+	      || ((dtmp.high ^ TREE_INT_CST_HIGH (step)) >= 0)))
+	{
+	  tem = double_int_to_tree (TREE_TYPE (init), dtmp);
 	  extract_range_from_binary_expr (&maxvr, PLUS_EXPR,
 					  TREE_TYPE (init), init, tem);
 	  /* Likewise if the addition did.  */