re PR tree-optimization/72772 (Missed SCEV after pass reordering@236440)

	PR tree-optimization/72772
	* tree-ssa-loop-niter.c (loop_exits_before_overflow): Check equality
	for expanded base.

	gcc/testsuite
	PR tree-optimization/pr72772
	* gcc.dg/tree-ssa/pr72772.c: New test.

From-SVN: r239291

gcc/ChangeLog

 2016-08-09  Bin Cheng  <bin.cheng@arm.com>
 
 	PR tree-optimization/72772
+	* tree-ssa-loop-niter.c (loop_exits_before_overflow): Check equality
+	for expanded base.
+
+2016-08-09  Bin Cheng  <bin.cheng@arm.com>
+
+	PR tree-optimization/72772
 	* tree-ssa-loop-niter.h (simplify_using_initial_conditions): Delete
 	parameter STOP.
 	* tree-ssa-loop-niter.c (tree_simplify_using_condition_1): Delete

gcc/testsuite/ChangeLog

+2016-08-09  Bin Cheng  <bin.cheng@arm.com>
+
+	PR tree-optimization/pr72772
+	* gcc.dg/tree-ssa/pr72772.c: New test.
+
 2016-08-09  Matthew Fortune  <matthew.fortune@imgtec.com>
 
 	PR rtl-optimization/66669

gcc/testsuite/gcc.dg/tree-ssa/pr72772.c

+/* { dg-do compile } */
+/* { dg-options "-O2 -ftree-loop-distribution -fdump-tree-ldist-details" } */
+
+int foo (int flag, char *a)
+{
+  short i, j;
+  short l = 0;
+  if (flag == 1)
+    l = 3;
+
+  for (i = 0; i < 4; i++)
+    {
+      for (j = l - 1; j > 0; j--)
+        a[j] = a[j - 1];
+      a[0] = i;
+    }
+}
+
+/* Addresses of array reference a[j] and a[j - 1] are SCEVs.  */
+/* { dg-final { scan-tree-dump-not "failed: evolution of base is not affine." "ldist" } } */
+

gcc/tree-ssa-loop-niter.c

@@ -4214,7 +4214,7 @@ loop_exits_before_overflow (tree base, tree step,
       for (civ = loop->control_ivs; civ; civ = civ->next)
 	{
 	  enum tree_code code;
-	  tree stepped, extreme, civ_type = TREE_TYPE (civ->step);
+	  tree civ_type = TREE_TYPE (civ->step);
 
 	  /* Have to consider type difference because operand_equal_p ignores
 	     that for constants.  */
@@ -4227,11 +4227,13 @@ 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)
-	      /* 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))
+	  if (operand_equal_p (base, civ->base, 0))
+	    return true;
+
+	  /* Control IV is recorded after expanding simple operations,
+	     Here we expand base and compare it too.  */
+	  tree expanded_base = expand_simple_operations (base);
+	  if (operand_equal_p (expanded_base, civ->base, 0))
 	    return true;
 
 	  /* If this is a before stepping control IV, in other words, we have
@@ -4253,9 +4255,14 @@ loop_exits_before_overflow (tree base, tree step,
 	  else
 	    code = PLUS_EXPR;
 
-	  stepped = fold_build2 (code, TREE_TYPE (base), base, step);
-	  if (operand_equal_p (stepped, civ->base, 0))
+	  tree stepped = fold_build2 (code, TREE_TYPE (base), base, step);
+	  tree expanded_stepped = fold_build2 (code, TREE_TYPE (base),
+					       expanded_base, step);
+	  if (operand_equal_p (stepped, civ->base, 0)
+	      || operand_equal_p (expanded_stepped, civ->base, 0))
 	    {
+	      tree extreme;
+
 	      if (tree_int_cst_sign_bit (step))
 		{
 		  code = LT_EXPR;