[turbofan] Fix bogus representation for {kCheckTaggedHole}.

The operator in question is guaranteed to produce a tagged value that is
not equal to the-hole, it however does not guarantee the value to be a
HeapObject. The correct representation hence is {kTagged}.

R=bmeurer@chromium.org
TEST=mjsunit/regress/regress-crbug-665587
BUG=chromium:665587

Review-Url: https://codereview.chromium.org/2504183002
Cr-Commit-Position: refs/heads/master@{#41032}

src/compiler/simplified-lowering.cc

@@ -2466,8 +2466,7 @@ class RepresentationSelector {
         return;
       }
       case IrOpcode::kCheckTaggedHole: {
-        VisitUnop(node, UseInfo::AnyTagged(),
-                  MachineRepresentation::kTaggedPointer);
+        VisitUnop(node, UseInfo::AnyTagged(), MachineRepresentation::kTagged);
         return;
       }
       case IrOpcode::kConvertTaggedHoleToUndefined: {

test/mjsunit/regress/regress-crbug-665587.js

+// Copyright 2016 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.
+
+// Flags: --allow-natives-syntax --expose-gc
+
+var a = new (function() { this[0] = 1 });
+function f() {
+  for (var i = 0; i < 4; ++i) {
+    var x = a[0];
+    (function() { return x });
+    if (i == 1) %OptimizeOsr();
+    gc();
+  }
+}
+f();