Workaround to avoid generic lowering breaking branches.

src/compiler/js-generic-lowering.cc

 // 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.
 
 #include "src/code-stubs.h"
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph-inl.h"
 #include "src/compiler/js-generic-lowering.h"
 #include "src/compiler/machine-operator.h"
 #include "src/compiler/node-aux-data-inl.h"
@@ skipping 367 matching lines @@
     centrystub_constant_.set(CodeConstant(CEntryStub(isolate(), 1).GetCode()));
   }
   PatchInsertInput(node, 0, centrystub_constant_.get());
   PatchInsertInput(node, nargs + 1, ref);
   PatchInsertInput(node, nargs + 2, arity);
   PatchOperator(node, common()->Call(desc));
 }
 
 
 Node* JSGenericLowering::LowerBranch(Node* node) {
-  Node* test = graph()->NewNode(machine()->WordEqual(), node->InputAt(0),
-                                jsgraph()->TrueConstant());
-  node->ReplaceInput(0, test);
+  if (!info()->is_typing_enabled()) {
+    // TODO(mstarzinger): If typing is enabled then simplified lowering will
+    // have inserted the correct ChangeBoolToBit, otherwise we need to perform
+    // poor-man's representation inference here and insert manual change.
+    Node* test = graph()->NewNode(machine()->WordEqual(), node->InputAt(0),
+                                  jsgraph()->TrueConstant());
+    node->ReplaceInput(0, test);
+  }
   return node;
 }
 
 
 Node* JSGenericLowering::LowerJSUnaryNot(Node* node) {
   ToBooleanStub stub(isolate(), ToBooleanStub::RESULT_AS_INVERSE_ODDBALL);
   ReplaceWithStubCall(node, &stub, CallDescriptor::kPatchableCallSite);
   return node;
 }
 
@@ skipping 142 matching lines @@
 Node* JSGenericLowering::LowerJSCallRuntime(Node* node) {
   Runtime::FunctionId function = OpParameter<Runtime::FunctionId>(node);
   int arity = OperatorProperties::GetValueInputCount(node->op());
   ReplaceWithRuntimeCall(node, function, arity);
   return node;
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8