X64/Win64: Fix bug in returning ObjectPair.

src/x64/codegen-x64.cc

 // Copyright 2009 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 6844 matching lines @@
   // Result is in rax - do not destroy this register!
 
   if (always_allocate_scope) {
     __ movq(kScratchRegister, scope_depth);
     __ decl(Operand(kScratchRegister, 0));
   }
 
   // Check for failure result.
   Label failure_returned;
   ASSERT(((kFailureTag + 1) & kFailureTagMask) == 0);
+#ifdef _WIN64
+  // If return value is on the stack, pop it to registers.
+  if (result_size_ > 1) {
+    ASSERT_EQ(2, result_size_);
+    // Position above 4 argument mirrors and arguments object.
+    __ movq(rax, Operand(rsp, 6 * kPointerSize));
+    __ movq(rdx, Operand(rsp, 7 * kPointerSize));
+  }
+#endif
   __ lea(rcx, Operand(rax, 1));
   // Lower 2 bits of rcx are 0 iff rax has failure tag.
   __ testl(rcx, Immediate(kFailureTagMask));
   __ j(zero, &failure_returned);
 
   // Exit the JavaScript to C++ exit frame.
   __ LeaveExitFrame(frame_type, result_size_);
   __ ret(0);
 
   // Handling of failure.
@@ skipping 857 matching lines @@
   masm.GetCode(&desc);
   // Call the function from C++.
   return FUNCTION_CAST<ModuloFunction>(buffer);
 }
 
 #endif
 
 #undef __
 
 } }  // namespace v8::internal