Add monomorphic CompareNilICs and Crankshaft support

src/code-stubs-hydrogen.cc

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 142 matching lines @@
   // arguments above
   HInstruction* stack_pop_count = stack_parameter_count;
   if (descriptor_->function_mode_ == JS_FUNCTION_STUB_MODE) {
     HInstruction* amount = graph()->GetConstant1();
     stack_pop_count = AddInstruction(
         HAdd::New(zone, context_, stack_parameter_count, amount));
     stack_pop_count->ChangeRepresentation(Representation::Integer32());
     stack_pop_count->ClearFlag(HValue::kCanOverflow);
   }
 
-  HReturn* hreturn_instruction = new(zone) HReturn(return_value,
-                                                   context_,
-                                                   stack_pop_count);
-  current_block()->Finish(hreturn_instruction);
+  if (!current_block()->IsFinished()) {
+    HReturn* hreturn_instruction = new(zone) HReturn(return_value,
+                                                     context_,
+                                                     stack_pop_count);
+    current_block()->Finish(hreturn_instruction);
+  }
   return true;
 }
 
 
 template <class Stub>
 class CodeStubGraphBuilder: public CodeStubGraphBuilderBase {
  public:
   explicit CodeStubGraphBuilder(Stub* stub)
       : CodeStubGraphBuilderBase(Isolate::Current(), stub) {}
 
@@ skipping 325 matching lines @@
   AddInstruction(deopt);
   current_block()->MarkAsDeoptimizing();
   return GetParameter(0);
 }
 
 
 Handle<Code> ArrayNArgumentsConstructorStub::GenerateCode() {
   return DoGenerateCode(this);
 }
 
+
+template <>
+HValue* CodeStubGraphBuilder<CompareNilICStub>::BuildCodeUninitializedStub() {
+  CompareNilICStub* stub = casted_stub();
+  HIfContinuation continuation;
+  Handle<Map> sentinel_map(graph()->isolate()->heap()->meta_map());
+  BuildCompareNil(GetParameter(0), stub->GetKind(),
+                  stub->GetTypes(), sentinel_map,
+                  RelocInfo::kNoPosition, &continuation);
+  IfBuilder if_nil(this, &continuation);
+  if_nil.Then();
+  if (continuation.IsFalseReachable()) {
+    if_nil.Else();
+    if_nil.Return(graph()->GetConstantSmi0());
+  }
+  if_nil.End();
+  return continuation.IsTrueReachable()
+      ? graph()->GetConstantSmi1()
+      : graph()->GetConstantUndefined();
+}
+
+
+Handle<Code> CompareNilICStub::GenerateCode() {
+  return DoGenerateCode(this);
+}
+
 } }  // namespace v8::internal