Work In Progress: support new.target

src/x64/full-codegen-x64.cc

Index: src/x64/full-codegen-x64.cc
diff --git a/src/x64/full-codegen-x64.cc b/src/x64/full-codegen-x64.cc
index 7560117c7307465442b101a125598b10255221dc..b2cd7215ecdb4950f0a5498e0952461ef6bf76f9 100644
--- a/src/x64/full-codegen-x64.cc
+++ b/src/x64/full-codegen-x64.cc
@@ -240,16 +240,39 @@ void FullCodeGenerator::Generate() {
 
   Variable* new_target_var = scope()->new_target_var();
   if (new_target_var != nullptr) {
+    // If this is a [[Construct]] then the new.target is passed as the -2
+    // argument. If it is a [[Call]] this is always undefined.
     Comment cmnt(masm_, "[ new.target");
+    Label assign, construct, check_frame_marker;
+    __ movp(rax, Operand(rbp, StandardFrameConstants::kCallerFPOffset));
+    __ Cmp(Operand(rax, StandardFrameConstants::kContextOffset),
+           Smi::FromInt(StackFrame::ARGUMENTS_ADAPTOR));
+    __ j(not_equal, &check_frame_marker);
+    __ movp(rax, Operand(rax, StandardFrameConstants::kCallerFPOffset));
+    __ bind(&check_frame_marker);
+    __ Cmp(Operand(rax, StandardFrameConstants::kMarkerOffset),
+           Smi::FromInt(StackFrame::CONSTRUCT));
+    __ j(equal, &construct);
+
+    // [[Call]]
+    __ LoadRoot(rax, Heap::kUndefinedValueRootIndex);
+    __ jmp(&assign);
+
+    // [[Construct]]
+    __ bind(&construct);
+
     // new.target is parameter -2.
     int offset = 2 * kPointerSize + kFPOnStackSize + kPCOnStackSize +
                  (info_->scope()->num_parameters() - 1) * kPointerSize;
     __ movp(rax, Operand(rbp, offset));
+
+    __ bind(&assign);
     SetVar(new_target_var, rax, rbx, rdx);
   }
 
   ArgumentsAccessStub::HasNewTarget has_new_target =
-      IsSubclassConstructor(info->function()->kind())
+      (info->scope()->new_target_var() != nullptr ||
+       IsSubclassConstructor(info->function()->kind()))
           ? ArgumentsAccessStub::HAS_NEW_TARGET
           : ArgumentsAccessStub::NO_NEW_TARGET;
 
@@ -465,7 +488,8 @@ void FullCodeGenerator::EmitReturnSequence() {
     int no_frame_start = masm_->pc_offset();
 
     int arg_count = info_->scope()->num_parameters() + 1;
-    if (IsSubclassConstructor(info_->function()->kind())) {
+    if (info_->scope()->new_target_var() != nullptr ||
+        IsSubclassConstructor(info_->function()->kind())) {
       arg_count++;
     }
     int arguments_bytes = arg_count * kPointerSize;