[backport gcc-4.9/trunk r199357 <mikpe@it.uu.se>]

gcc/

2013-05-27  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/57343
	* tree-ssa-loop-niter.c (number_of_iterations_ne_max): Do not
	use multiple_of_p if not TYPE_OVERFLOW_UNDEFINED.
	(number_of_iterations_cond): Do not build the folded tree.

gcc/testsuite/

2013-05-27  Richard Biener  <rguenther@suse.de>

	PR tree-optimization/57343
	* gcc.dg/torture/pr57343.c: New testcase.

--- gcc-4.8.1/gcc/testsuite/gcc.dg/torture/pr57343.c.~1~	1970-01-01 01:00:00.000000000 +0100
+++ gcc-4.8.1/gcc/testsuite/gcc.dg/torture/pr57343.c	2013-06-01 11:09:34.828071342 +0200
@@ -0,0 +1,22 @@
+/* { dg-do run } */
+
+int c = 0;
+
+int
+main ()
+{
+  int i, f = 1;
+  for (i = 0; i < 5; i++)
+    {
+      --c;
+      unsigned char h = c * 100;
+      if (h == 0)
+	{
+	  f = 0;
+	  break;
+	}
+    }
+  if (f != 1)
+    __builtin_abort ();
+  return 0;
+}
--- gcc-4.8.1/gcc/tree-ssa-loop-niter.c.~1~	2013-05-08 11:10:04.000000000 +0200
+++ gcc-4.8.1/gcc/tree-ssa-loop-niter.c	2013-06-01 11:09:34.828071342 +0200
@@ -552,10 +552,18 @@ number_of_iterations_ne_max (mpz_t bnd,
 {
   double_int max;
   mpz_t d;
+  tree type = TREE_TYPE (c);
   bool bnds_u_valid = ((no_overflow && exit_must_be_taken)
 		       || mpz_sgn (bnds->below) >= 0);
 
-  if (multiple_of_p (TREE_TYPE (c), c, s))
+  if (integer_onep (s)
+      || (TREE_CODE (c) == INTEGER_CST
+	  && TREE_CODE (s) == INTEGER_CST
+	  && tree_to_double_int (c).mod (tree_to_double_int (s),
+					 TYPE_UNSIGNED (type),
+					 EXACT_DIV_EXPR).is_zero ())
+      || (TYPE_OVERFLOW_UNDEFINED (TREE_TYPE (c))
+	  && multiple_of_p (type, c, s)))
     {
       /* If C is an exact multiple of S, then its value will be reached before
 	 the induction variable overflows (unless the loop is exited in some
@@ -572,16 +580,15 @@ number_of_iterations_ne_max (mpz_t bnd,
      the whole # of iterations analysis will fail).  */
   if (!no_overflow)
     {
-      max = double_int::mask (TYPE_PRECISION (TREE_TYPE (c))
-			     - tree_low_cst (num_ending_zeros (s), 1));
+      max = double_int::mask (TYPE_PRECISION (type)
+			      - tree_low_cst (num_ending_zeros (s), 1));
       mpz_set_double_int (bnd, max, true);
       return;
     }
 
   /* Now we know that the induction variable does not overflow, so the loop
      iterates at most (range of type / S) times.  */
-  mpz_set_double_int (bnd, double_int::mask (TYPE_PRECISION (TREE_TYPE (c))),
-		      true);
+  mpz_set_double_int (bnd, double_int::mask (TYPE_PRECISION (type)), true);
 
   /* If the induction variable is guaranteed to reach the value of C before
      overflow, ... */
@@ -1311,7 +1318,8 @@ number_of_iterations_cond (struct loop *
     }
 
   /* If the loop exits immediately, there is nothing to do.  */
-  if (integer_zerop (fold_build2 (code, boolean_type_node, iv0->base, iv1->base)))
+  tree tem = fold_binary (code, boolean_type_node, iv0->base, iv1->base);
+  if (tem && integer_zerop (tem))
     {
       niter->niter = build_int_cst (unsigned_type_for (type), 0);
       niter->max = double_int_zero;