[compiler] Introduce initial StrictEqualStub.

src/x64/code-stubs-x64.cc

 // Copyright 2013 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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
 #include "src/ic/handler-compiler.h"
@@ skipping 3154 matching lines @@
   if (equality) {
     StringHelper::GenerateFlatOneByteStringEquals(masm, left, right, tmp1,
                                                   tmp2);
   } else {
     StringHelper::GenerateCompareFlatOneByteStrings(
         masm, left, right, tmp1, tmp2, tmp3, kScratchRegister);
   }
 
   // Handle more complex cases in runtime.
   __ bind(&runtime);
-  __ PopReturnAddressTo(tmp1);
-  __ Push(left);
-  __ Push(right);
-  __ PushReturnAddressFrom(tmp1);
   if (equality) {
-    __ TailCallRuntime(Runtime::kStringEquals);
+    {
+      FrameScope scope(masm, StackFrame::INTERNAL);
+      __ Push(left);
+      __ Push(right);
+      __ CallRuntime(Runtime::kStringEqual);
+    }
+    __ LoadRoot(rdx, Heap::kTrueValueRootIndex);
+    __ subp(rax, rdx);
+    __ Ret();
   } else {
+    __ PopReturnAddressTo(tmp1);
+    __ Push(left);
+    __ Push(right);
+    __ PushReturnAddressFrom(tmp1);
     __ TailCallRuntime(Runtime::kStringCompare);
   }
 
   __ bind(&miss);
   GenerateMiss(masm);
 }
 
 
 void CompareICStub::GenerateReceivers(MacroAssembler* masm) {
   DCHECK_EQ(CompareICState::RECEIVER, state());
@@ skipping 2451 matching lines @@
                            NULL);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64