Adds the possibility of setting a Code object as the callback of a FunctionTemplate.

src/ic/x64/handler-compiler-x64.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.
 
 #if V8_TARGET_ARCH_X64
 
 #include "src/ic/call-optimization.h"
 #include "src/ic/handler-compiler.h"
 #include "src/ic/ic.h"
 #include "src/isolate-inl.h"
@@ skipping 170 matching lines @@
   if (api_call_info->data()->IsUndefined()) {
     call_data_undefined = true;
     __ LoadRoot(data, Heap::kUndefinedValueRootIndex);
   } else {
     __ movp(data, FieldOperand(callee, JSFunction::kSharedFunctionInfoOffset));
     __ movp(data, FieldOperand(data, SharedFunctionInfo::kFunctionDataOffset));
     __ movp(data, FieldOperand(data, FunctionTemplateInfo::kCallCodeOffset));
     __ movp(data, FieldOperand(data, CallHandlerInfo::kDataOffset));
   }
 
+  if (api_call_info->fast_handler()->IsCode()) {
+    // Just tail call into the fast handler if present.
+    __ Jump(handle(Code::cast(api_call_info->fast_handler())),
+            RelocInfo::CODE_TARGET);
+    return;
+  }
+
   // Put api_function_address in place.
   Address function_address = v8::ToCData<Address>(api_call_info->callback());
   __ Move(api_function_address, function_address,
           RelocInfo::EXTERNAL_REFERENCE);
 
   // Jump to stub.
   CallApiAccessorStub stub(isolate, is_store, call_data_undefined);
   __ TailCallStub(&stub);
 }
 
@@ skipping 599 matching lines @@
   // Return the generated code.
   return GetCode(kind(), Code::NORMAL, name);
 }
 
 
 #undef __
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64