[turbofan] Relax a too-strict dcheck.

BUG=v8:5573

Review-Url: https://codereview.chromium.org/2458623002
Cr-Commit-Position: refs/heads/master@{#40619}

src/compiler/simplified-lowering.cc

@@ -1394,8 +1394,7 @@ class RepresentationSelector {
             node->AppendInput(jsgraph_->zone(), jsgraph_->Int32Constant(0));
             NodeProperties::ChangeOp(node, lowering->machine()->Word32Equal());
           } else {
-            DCHECK_EQ(input_info->representation(),
-                      MachineRepresentation::kTagged);
+            DCHECK(CanBeTaggedPointer(input_info->representation()));
             // BooleanNot(x: kRepTagged) => WordEqual(x, #false)
             node->AppendInput(jsgraph_->zone(), jsgraph_->FalseConstant());
             NodeProperties::ChangeOp(node, lowering->machine()->WordEqual());

test/mjsunit/compiler/regress-v8-5573.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
+
+var global = true;
+global = false;
+
+function f() {
+  return !global;
+}
+
+%OptimizeFunctionOnNextCall(f);
+assertTrue(f());