Turn StringLengthStub (used by string wrappers only) into a hydrogen stub.

src/x64/code-stubs-x64.cc

Index: src/x64/code-stubs-x64.cc
diff --git a/src/x64/code-stubs-x64.cc b/src/x64/code-stubs-x64.cc
index 84706fe4207f12dba9aa357073255add92bd0dc5..d1ea51bf8bc3b435acab16642190cf0a04a73cfc 100644
--- a/src/x64/code-stubs-x64.cc
+++ b/src/x64/code-stubs-x64.cc
@@ -166,6 +166,26 @@ void KeyedLoadFieldStub::InitializeInterfaceDescriptor(
 }
 
 
+void StringLengthStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  static Register registers[] = { rax, rcx };
+  descriptor->register_param_count_ = 2;
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ = NULL;
+}
+
+
+void KeyedStringLengthStub::InitializeInterfaceDescriptor(
+    Isolate* isolate,
+    CodeStubInterfaceDescriptor* descriptor) {
+  static Register registers[] = { rdx, rax };
+  descriptor->register_param_count_ = 2;
+  descriptor->register_params_ = registers;
+  descriptor->deoptimization_handler_ = NULL;
+}
+
+
 void KeyedStoreFastElementStub::InitializeInterfaceDescriptor(
     Isolate* isolate,
     CodeStubInterfaceDescriptor* descriptor) {
@@ -913,35 +933,6 @@ void FunctionPrototypeStub::Generate(MacroAssembler* masm) {
 }
 
 
-void StringLengthStub::Generate(MacroAssembler* masm) {
-  Label miss;
-  Register receiver;
-  if (kind() == Code::KEYED_LOAD_IC) {
-    // ----------- S t a t e -------------
-    //  -- rax    : key
-    //  -- rdx    : receiver
-    //  -- rsp[0] : return address
-    // -----------------------------------
-    __ Cmp(rax, masm->isolate()->factory()->length_string());
-    __ j(not_equal, &miss);
-    receiver = rdx;
-  } else {
-    ASSERT(kind() == Code::LOAD_IC);
-    // ----------- S t a t e -------------
-    //  -- rax    : receiver
-    //  -- rcx    : name
-    //  -- rsp[0] : return address
-    // -----------------------------------
-    receiver = rax;
-  }
-
-  StubCompiler::GenerateLoadStringLength(masm, receiver, r8, r9, &miss);
-  __ bind(&miss);
-  StubCompiler::TailCallBuiltin(
-      masm, BaseLoadStoreStubCompiler::MissBuiltin(kind()));
-}
-
-
 void StoreArrayLengthStub::Generate(MacroAssembler* masm) {
   // ----------- S t a t e -------------
   //  -- rax    : value