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 2737 matching lines @@
   __ PushRoot(Heap::kUndefinedValueRootIndex);
   // return value default
   __ PushRoot(Heap::kUndefinedValueRootIndex);
   // isolate
   Register scratch = call_data;
   __ Move(scratch, ExternalReference::isolate_address(masm->isolate()));
   __ Push(scratch);
   // holder
   __ Push(holder);
 
+  if (this->is_lazy()) {

[jochen (gone - plz use gerrit), 2017/06/14 09:26:01]

maybe we can just enter the correct context before invoking this stub, i.e., in
https://cs.chromium.org/chromium/src/v8/src/ic/x64/handler-compiler-x64.cc?rc...
we still have the accessor_holder so we could just load the context from there
(in the lazy case) or from the callee (in the non-lazy case).

Do you want to give that a try?

[Yuki, 2017/06/14 13:34:52]

I gave it a shot in PS8, but I failed so far.  Could you take a look at PS8 and
help me understand what's wrong?

I understand your suggestion to get the context from |accessor_holder|, but I
first tried to simply move the code to
PropertyHandlerCompiler::GenerateApiAccessorCall(), and it didn't work :( 
Replacing |holder| with |accessor_holder| didn't work, neither.

+    // load context from holder
+    __ movp(scratch, FieldOperand(holder, HeapObject::kMapOffset));
+    __ 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