Set the current context to the function's context when entering to LAP.

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/api-arguments.h"
 #include "src/bootstrapper.h"
 #include "src/code-stubs.h"
 #include "src/codegen.h"
@@ skipping 2818 matching lines @@
   // return value
   __ Push(scratch);
   // return value default
   __ Push(scratch);
   // isolate
   __ Move(scratch, ExternalReference::isolate_address(masm->isolate()));
   __ Push(scratch);
   // holder
   __ Push(holder);
 
+  if (this->is_lazy()) {
+    // load context from holder
+    __ movp(scratch, FieldOperand(holder, HeapObject::kMapOffset));

[Yuki, 2017/03/28 14:16:58]

|holder| seems pointing to the receiver object instead of the prototype object. 
Is this expected?

I'd like to get the prototype object's creation context.  But, I'm not sure how
to get it...

NamedLoadHandlerCompiler::CompileLoadCallback() seems having |holder|, which is
passed to GenerateApiAccessorCall as |accessor_holder|.
https://cs.chromium.org/chromium/src/v8/src/ic/handler-compiler.cc?rcl=9e60c6...

PropertyHandlerCompiler::GenerateApiAccessorCall() seems looking up a holder,
but the result is CallOptimization::kHolderIsReceiver.
https://cs.chromium.org/chromium/src/v8/src/ic/x64/handler-compiler-x64.cc?rc...

Do you have any clues?

[jochen (gone - plz use gerrit), 2017/03/28 14:43:39]

is that only the case for your test? In that case, I think you need to install a
signature on the accessor

[Yuki, 2017/03/29 14:19:41]

I only tested with the new unittest.  I installed the signature on the accessor
(in PS5), but no luck.  It still fails.

By the way, in Blink, info.Holder() points to the receiver object instead of the
prototype object.  Is |holder| here equivalent to
FunctionCallbackInfo::Holder(), or a different thing?

+    __ GetMapConstructor(scratch, scratch, context);
+    __ movp(context, FieldOperand(scratch, JSFunction::kContextOffset));
+  } else {
+    // load context from callee
+    __ movp(context, FieldOperand(callee, JSFunction::kContextOffset));
+  }
+
   __ movp(scratch, rsp);
   // Push return address back on stack.
   __ PushReturnAddressFrom(return_address);
 
-  if (!this->is_lazy()) {
-    // load context from callee
-    __ movp(context, FieldOperand(callee, JSFunction::kContextOffset));
-  }
-
   // Allocate the v8::Arguments structure in the arguments' space since
   // it's not controlled by GC.
   const int kApiStackSpace = 3;
 
   PrepareCallApiFunction(masm, kApiStackSpace);
 
   // FunctionCallbackInfo::implicit_args_.
   int argc = this->argc();
   __ movp(StackSpaceOperand(0), scratch);
   __ addp(scratch, Immediate((argc + FCA::kArgsLength - 1) * kPointerSize));
@@ skipping 117 matching lines @@
                            kStackUnwindSpace, nullptr, return_value_operand,
                            NULL);
 }
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64