[turbofan] Truncation of Bit/Word8/16 to Word32 is a no-op.

TEST=mjsunit/compiler/regress-445859
BUG=chromium:445859
LOG=y
R=jarin@chromium.org

Review URL: https://codereview.chromium.org/828313002

Cr-Commit-Position: refs/heads/master@{#25951}

src/compiler/simplified-lowering.cc

@@ -181,7 +181,7 @@ class RepresentationSelector {
     } else {
       // In the change phase, insert a change before the use if necessary.
       MachineTypeUnion output = GetInfo(input)->output;
-      if ((output & kRepWord32) == 0) {
+      if ((output & (kRepBit | kRepWord8 | kRepWord16 | kRepWord32)) == 0) {
         // Output representation doesn't match usage.
         TRACE(("  truncate-to-int32: #%d:%s(@%d #%d:%s) ", node->id(),
                node->op()->mnemonic(), index, input->id(),

test/mjsunit/compiler/regress-445859.js

+// Copyright 2014 the V8 project authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+var foo = (function Module(global, env, buffer) {
+  "use asm";
+  var i8 = new global.Int8Array(buffer);
+  function foo() { i8[0] += 4294967295; }
+  return { foo: foo };
+})(this, {}, new ArrayBuffer(64 * 1024)).foo;
+foo();