[turbofan] Some strength reduction on Smi/HeapObject checks.

src/compiler/common-operator-reducer.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/compiler/common-operator-reducer.h"
 
 #include <algorithm>
 
 #include "src/compiler/common-operator.h"
 #include "src/compiler/graph.h"
 #include "src/compiler/machine-operator.h"
 #include "src/compiler/node.h"
 #include "src/compiler/node-matchers.h"
 #include "src/compiler/node-properties.h"
 
 namespace v8 {
 namespace internal {
 namespace compiler {
 
 namespace {
 
-enum class Decision { kUnknown, kTrue, kFalse };
-
 Decision DecideCondition(Node* const cond) {
   switch (cond->opcode()) {
     case IrOpcode::kInt32Constant: {
       Int32Matcher mcond(cond);
       return mcond.Value() ? Decision::kTrue : Decision::kFalse;
     }
     case IrOpcode::kHeapConstant: {
       HeapObjectMatcher mcond(cond);
       return mcond.Value()->BooleanValue() ? Decision::kTrue : Decision::kFalse;
     }
@@ skipping 371 matching lines @@
   node->ReplaceInput(0, a);
   node->ReplaceInput(1, b);
   node->TrimInputCount(2);
   NodeProperties::ChangeOp(node, op);
   return Changed(node);
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8