[Proxies] Support constructable proxy as new.target (reland)

src/x64/builtins-x64.cc

 // Copyright 2012 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/code-factory.h"
 #include "src/codegen.h"
 #include "src/deoptimizer.h"
 #include "src/full-codegen/full-codegen.h"
@@ skipping 1786 matching lines @@
     __ Push(rdi);
     __ CallRuntime(Runtime::kThrowCalledNonCallable, 1);
   }
 }
 
 
 // static
 void Builtins::Generate_ConstructFunction(MacroAssembler* masm) {
   // ----------- S t a t e -------------
   //  -- rax : the number of arguments (not including the receiver)
-  //  -- rdx : the new target (checked to be a JSFunction)
+  //  -- rdx : the new target (checked to be a constructor)
   //  -- rdi : the constructor to call (checked to be a JSFunction)
   // -----------------------------------
-  __ AssertFunction(rdx);
   __ AssertFunction(rdi);
 
   // Calling convention for function specific ConstructStubs require
   // rbx to contain either an AllocationSite or undefined.
   __ LoadRoot(rbx, Heap::kUndefinedValueRootIndex);
 
   // Tail call to the function-specific construct stub (still in the caller
   // context at this point).
   __ movp(rcx, FieldOperand(rdi, JSFunction::kSharedFunctionInfoOffset));
   __ movp(rcx, FieldOperand(rcx, SharedFunctionInfo::kConstructStubOffset));
@@ skipping 242 matching lines @@
   __ ret(0);
 }
 
 
 #undef __
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64