re PR tree-optimization/70715 (SCEV failed to prove no-overflow-ness information unsigned loop IV)

	PR tree-optimization/70715
	* tree-ssa-loop-niter.c (loop_exits_before_overflow): Check equality
	after expanding BASE using expand_simple_operations.

	gcc/testsuite/ChangeLog
	PR tree-optimization/70715
	* gcc.dg/tree-ssa/scev-13.c: New test.

From-SVN: r235333

gcc/ChangeLog

+2016-04-21  Bin Cheng  <bin.cheng@arm.com>
+
+	PR tree-optimization/70715
+	* tree-ssa-loop-niter.c (loop_exits_before_overflow): Check equality
+	after expanding BASE using expand_simple_operations.
+
 2016-04-21  Marc Glisse  <marc.glisse@inria.fr>
 
 	* match.pd (min(-x, -y), max(-x, -y), min(~x, ~y), max(~x, ~y)):

gcc/testsuite/ChangeLog

+2016-04-21  Bin Cheng  <bin.cheng@arm.com>
+
+	PR tree-optimization/70715
+	* gcc.dg/tree-ssa/scev-13.c: New test.
+
 2016-04-21  Marc Glisse  <marc.glisse@inria.fr>
 
 	* gcc.dg/tree-ssa/minmax-2.c: New testcase.

gcc/testsuite/gcc.dg/tree-ssa/scev-13.c

+/* { dg-do compile } */
+/* { dg-options "-O3 -fdump-tree-ldist" } */
+
+int
+foo (char *p, unsigned n)
+{
+  while(n--)
+    {
+      p[n]='A';
+    }
+  return 0;
+}
+
+/* Loop can be transformed into builtin memset since &p[n] is SCEV.  */
+/* { dg-final { scan-tree-dump "builtin_memset" "ldist" } } */

gcc/tree-ssa-loop-niter.c

@@ -4141,7 +4141,11 @@ loop_exits_before_overflow (tree base, tree step,
 	    continue;
 
 	  /* Done proving if this is a no-overflow control IV.  */
-	  if (operand_equal_p (base, civ->base, 0))
+	  if (operand_equal_p (base, civ->base, 0)
+	      /* Control IV is recorded after expanding simple operations,
+		 Here we compare it against expanded base too.  */
+	      || operand_equal_p (expand_simple_operations (base),
+				  civ->base, 0))
 	    return true;
 
 	  /* If this is a before stepping control IV, in other words, we have