re PR tree-optimization/64454 (optimize (x%5)%5)

PR tree-optimization/64454
	* tree-vrp.c (simplify_div_or_mod_using_ranges): Optimize
	op0 % op1 into op0 if op0 is in range [-op1 + 1, op1 - 1]
	for signed or [0, op1 - 1] for unsigned modulo.
	(simplify_stmt_using_ranges): Call simplify_div_or_mod_using_ranges
	even if op1 does not satisfy integer_pow2p.

	* gcc.dg/pr64454.c: New test.

From-SVN: r219491

gcc/ChangeLog

@@ -1,5 +1,12 @@
 2015-01-12  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/64454
+	* tree-vrp.c (simplify_div_or_mod_using_ranges): Optimize
+	op0 % op1 into op0 if op0 is in range [-op1 + 1, op1 - 1]
+	for signed or [0, op1 - 1] for unsigned modulo.
+	(simplify_stmt_using_ranges): Call simplify_div_or_mod_using_ranges
+	even if op1 does not satisfy integer_pow2p.
+
 	PR other/64370
 	* sreal.c (sreal::to_double): Use ldexp instead of scalbnl.
 

gcc/testsuite/ChangeLog

@@ -1,5 +1,8 @@
 2015-01-12  Jakub Jelinek  <jakub@redhat.com>
 
+	PR tree-optimization/64454
+	* gcc.dg/pr64454.c: New test.
+
 	PR testsuite/64028
 	* gcc.dg/vect/no-section-anchors-vect-31.c: Add dg-add-options
 	bind_pic_locally.

gcc/testsuite/gcc.dg/pr64454.c

@@ -0,0 +1,43 @@
+/* PR tree-optimization/64454 */
+/* { dg-do compile } */
+/* { dg-options "-O2 -fdump-tree-vrp1" } */
+
+unsigned
+f1 (unsigned x)
+{
+  return (x % 5) % 5;
+}
+
+int
+f2 (int x)
+{
+  return (x % 5) % 5;
+}
+
+int
+f3 (int x)
+{
+  return (x % -5) % -5;
+}
+
+unsigned
+f4 (unsigned x)
+{
+  return (x % 5) % 6;
+}
+
+int
+f5 (int x)
+{
+  return (x % 5) % 6;
+}
+
+int
+f6 (int x)
+{
+  return (x % -5) % -6;
+}
+
+/* { dg-final { scan-tree-dump-times "% 5" 6 "vrp1" } } */
+/* { dg-final { scan-tree-dump-times "% 6" 0 "vrp1" } } */
+/* { dg-final { cleanup-tree-dump "vrp1" } } */

gcc/tree-vrp.c

@@ -8998,7 +8998,11 @@ simplify_truth_ops_using_ranges (gimple_stmt_iterator *gsi, gimple stmt)
 
 /* Simplify a division or modulo operator to a right shift or
    bitwise and if the first operand is unsigned or is greater
-   than zero and the second operand is an exact power of two.  */
+   than zero and the second operand is an exact power of two.
+   For TRUNC_MOD_EXPR op0 % op1 with constant op1, optimize it
+   into just op0 if op0's range is known to be a subset of
+   [-op1 + 1, op1 - 1] for signed and [0, op1 - 1] for unsigned
+   modulo.  */
 
 static bool
 simplify_div_or_mod_using_ranges (gimple stmt)
@@ -9007,7 +9011,30 @@ simplify_div_or_mod_using_ranges (gimple stmt)
   tree val = NULL;
   tree op0 = gimple_assign_rhs1 (stmt);
   tree op1 = gimple_assign_rhs2 (stmt);
-  value_range_t *vr = get_value_range (gimple_assign_rhs1 (stmt));
+  value_range_t *vr = get_value_range (op0);
+
+  if (rhs_code == TRUNC_MOD_EXPR
+      && TREE_CODE (op1) == INTEGER_CST
+      && tree_int_cst_sgn (op1) == 1
+      && range_int_cst_p (vr)
+      && tree_int_cst_lt (vr->max, op1))
+    {
+      if (TYPE_UNSIGNED (TREE_TYPE (op0))
+	  || tree_int_cst_sgn (vr->min) >= 0
+	  || tree_int_cst_lt (fold_unary (NEGATE_EXPR, TREE_TYPE (op1), op1),
+			      vr->min))
+	{
+	  /* If op0 already has the range op0 % op1 has,
+	     then TRUNC_MOD_EXPR won't change anything.  */
+	  gimple_stmt_iterator gsi = gsi_for_stmt (stmt);
+	  gimple_assign_set_rhs_from_tree (&gsi, op0);
+	  update_stmt (stmt);
+	  return true;
+	}
+    }
+
+  if (!integer_pow2p (op1))
+    return false;
 
   if (TYPE_UNSIGNED (TREE_TYPE (op0)))
     {
@@ -9880,11 +9907,14 @@ simplify_stmt_using_ranges (gimple_stmt_iterator *gsi)
 
       /* Transform TRUNC_DIV_EXPR and TRUNC_MOD_EXPR into RSHIFT_EXPR
 	 and BIT_AND_EXPR respectively if the first operand is greater
-	 than zero and the second operand is an exact power of two.  */
+	 than zero and the second operand is an exact power of two.
+	 Also optimize TRUNC_MOD_EXPR away if the second operand is
+	 constant and the first operand already has the right value
+	 range.  */
 	case TRUNC_DIV_EXPR:
 	case TRUNC_MOD_EXPR:
-	  if (INTEGRAL_TYPE_P (TREE_TYPE (rhs1))
-	      && integer_pow2p (gimple_assign_rhs2 (stmt)))
+	  if (TREE_CODE (rhs1) == SSA_NAME
+	      && INTEGRAL_TYPE_P (TREE_TYPE (rhs1)))
 	    return simplify_div_or_mod_using_ranges (stmt);
 	  break;