[turbofan] Add support for change/truncate to MachineOperatorReducer.

test/compiler-unittests/graph-unittest.cc

Index: test/compiler-unittests/graph-unittest.cc
diff --git a/test/compiler-unittests/graph-unittest.cc b/test/compiler-unittests/graph-unittest.cc
index 251c5a055f45327e1ff5d9d45500070c2586138d..8dc047df2ddba872c60d9a93970cb2d33cd519da 100644
--- a/test/compiler-unittests/graph-unittest.cc
+++ b/test/compiler-unittests/graph-unittest.cc
@@ -55,6 +55,11 @@ Node* GraphTest::Int32Constant(int32_t value) {
 }
 
 
+Node* GraphTest::Int64Constant(int64_t value) {
+  return graph()->NewNode(common()->Int64Constant(value));
+}
+
+
 Node* GraphTest::NumberConstant(double value) {
   return graph()->NewNode(common()->NumberConstant(value));
 }
@@ -647,6 +652,12 @@ Matcher<Node*> IsInt32Constant(const Matcher<int32_t>& value_matcher) {
 }
 
 
+Matcher<Node*> IsInt64Constant(const Matcher<int64_t>& value_matcher) {
+  return MakeMatcher(
+      new IsConstantMatcher<int64_t>(IrOpcode::kInt64Constant, value_matcher));
+}
+
+
 Matcher<Node*> IsFloat64Constant(const Matcher<double>& value_matcher) {
   return MakeMatcher(
       new IsConstantMatcher<double>(IrOpcode::kFloat64Constant, value_matcher));