Fix use of boolean_true/false_node (PR 83979)

[Richard Sandiford]

r255913 changed some constant_boolean_node calls to boolean_true_node
and boolean_false_node, which meant that the returned tree didn't
always have the right type.

Tested on aarch64-linux-gnu.  Probably bordering on obvious, but just
in case: OK to install?

Richard


2018-01-23  Richard Sandiford  <richard.sandif...@linaro.org>

gcc/
        PR tree-optimization/83979
        * fold-const.c (fold_comparison): Use constant_boolean_node
        instead of boolean_{true,false}_node.

gcc/testsuite/
        PR tree-optimization/83979
        * g++.dg/pr83979.c: New test.

Index: gcc/fold-const.c
===================================================================
--- gcc/fold-const.c    2018-01-16 15:13:19.643832679 +0000
+++ gcc/fold-const.c    2018-01-23 11:23:59.982555852 +0000
@@ -8572,39 +8572,39 @@ fold_comparison (location_t loc, enum tr
                {
                case EQ_EXPR:
                  if (known_eq (bitpos0, bitpos1))
-                   return boolean_true_node;
+                   return constant_boolean_node (true, type);
                  if (known_ne (bitpos0, bitpos1))
-                   return boolean_false_node;
+                   return constant_boolean_node (false, type);
                  break;
                case NE_EXPR:
                  if (known_ne (bitpos0, bitpos1))
-                   return boolean_true_node;
+                   return constant_boolean_node (true, type);
                  if (known_eq (bitpos0, bitpos1))
-                   return boolean_false_node;
+                   return constant_boolean_node (false, type);
                  break;
                case LT_EXPR:
                  if (known_lt (bitpos0, bitpos1))
-                   return boolean_true_node;
+                   return constant_boolean_node (true, type);
                  if (known_ge (bitpos0, bitpos1))
-                   return boolean_false_node;
+                   return constant_boolean_node (false, type);
                  break;
                case LE_EXPR:
                  if (known_le (bitpos0, bitpos1))
-                   return boolean_true_node;
+                   return constant_boolean_node (true, type);
                  if (known_gt (bitpos0, bitpos1))
-                   return boolean_false_node;
+                   return constant_boolean_node (false, type);
                  break;
                case GE_EXPR:
                  if (known_ge (bitpos0, bitpos1))
-                   return boolean_true_node;
+                   return constant_boolean_node (true, type);
                  if (known_lt (bitpos0, bitpos1))
-                   return boolean_false_node;
+                   return constant_boolean_node (false, type);
                  break;
                case GT_EXPR:
                  if (known_gt (bitpos0, bitpos1))
-                   return boolean_true_node;
+                   return constant_boolean_node (true, type);
                  if (known_le (bitpos0, bitpos1))
-                   return boolean_false_node;
+                   return constant_boolean_node (false, type);
                  break;
                default:;
                }
Index: gcc/testsuite/g++.dg/pr83979.c
===================================================================
--- /dev/null   2018-01-22 18:46:35.983712806 +0000
+++ gcc/testsuite/g++.dg/pr83979.c      2018-01-23 11:23:59.982555852 +0000
@@ -0,0 +1,7 @@
+/* { dg-compile } */
+
+int
+foo (char* p)
+{
+  return p + 1000 < p;
+}