re PR tree-optimization/64277 (Incorrect warning "array subscript is above array bounds")

gcc/

	PR tree-optimization/64277
	* tree-ssa-loop-niter.c (record_nonwrapping_iv): Use base
	range info when possible to refine estimation.

gcc/testsuite/

	PR tree-optimization/64277
	* gcc.dg/pr64277.c: New.

From-SVN: r220204

gcc/ChangeLog

+2015-01-28  Ilya Enkovich  <ilya.enkovich@intel.com>
+
+	PR tree-optimization/64277
+	* tree-ssa-loop-niter.c (record_nonwrapping_iv): Use base
+	range info when possible to refine estimation.
+
 2015-01-28  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	PR tree-optimization/64718

gcc/testsuite/ChangeLog

+2015-01-28  Ilya Enkovich  <ilya.enkovich@intel.com>
+
+	PR tree-optimization/64277
+	* gcc.dg/pr64277.c: New.
+
 2015-01-28  Thomas Preud'homme  <thomas.preudhomme@arm.com>
 
 	PR tree-optimization/64718

gcc/testsuite/gcc.dg/pr64277.c

+/* PR tree-optimization/64277 */
+/* { dg-do compile } */
+/* { dg-options "-O3 -Wall -Werror -fdump-tree-cunroll-details" } */
+/* { dg-final { scan-tree-dump "loop with 5 iterations completely unrolled" "cunroll" } } */
+/* { dg-final { scan-tree-dump "loop with 6 iterations completely unrolled" "cunroll" } } */
+/* { dg-final { cleanup-tree-dump "cunroll" } } */
+
+int f1[10];
+void test1 (short a[], short m, unsigned short l)
+{
+  int i = l;
+  for (i = i + 5; i < m; i++)
+    f1[i] = a[i]++;
+}
+
+void test2 (short a[], short m, short l)
+{
+  int i;
+  if (m > 5)
+    m = 5;
+  for (i = m; i > l; i--)
+    f1[i] = a[i]++;
+}

gcc/tree-ssa-loop-niter.c

@@ -2754,6 +2754,7 @@ record_nonwrapping_iv (struct loop *loop, tree base, tree step, gimple stmt,
 {
   tree niter_bound, extreme, delta;
   tree type = TREE_TYPE (base), unsigned_type;
+  tree orig_base = base;
 
   if (TREE_CODE (step) != INTEGER_CST || integer_zerop (step))
     return;
@@ -2777,16 +2778,30 @@ record_nonwrapping_iv (struct loop *loop, tree base, tree step, gimple stmt,
 
   if (tree_int_cst_sign_bit (step))
     {
+      wide_int min, max;
       extreme = fold_convert (unsigned_type, low);
-      if (TREE_CODE (base) != INTEGER_CST)
+      if (TREE_CODE (orig_base) == SSA_NAME
+	  && TREE_CODE (high) == INTEGER_CST
+	  && INTEGRAL_TYPE_P (TREE_TYPE (orig_base))
+	  && get_range_info (orig_base, &min, &max) == VR_RANGE
+	  && wi::gts_p (high, max))
+	base = wide_int_to_tree (unsigned_type, max);
+      else if (TREE_CODE (base) != INTEGER_CST)
 	base = fold_convert (unsigned_type, high);
       delta = fold_build2 (MINUS_EXPR, unsigned_type, base, extreme);
       step = fold_build1 (NEGATE_EXPR, unsigned_type, step);
     }
   else
     {
+      wide_int min, max;
       extreme = fold_convert (unsigned_type, high);
-      if (TREE_CODE (base) != INTEGER_CST)
+      if (TREE_CODE (orig_base) == SSA_NAME
+	  && TREE_CODE (low) == INTEGER_CST
+	  && INTEGRAL_TYPE_P (TREE_TYPE (orig_base))
+	  && get_range_info (orig_base, &min, &max) == VR_RANGE
+	  && wi::gts_p (min, low))
+	base = wide_int_to_tree (unsigned_type, min);
+      else if (TREE_CODE (base) != INTEGER_CST)
 	base = fold_convert (unsigned_type, low);
       delta = fold_build2 (MINUS_EXPR, unsigned_type, extreme, base);
     }