[x64] Fix testw with immediates.

test/cctest/test-assembler-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 310 matching lines @@
 
   CodeDesc desc;
   assm.GetCode(&desc);
   // Call the function from C++.
   uint64_t left = V8_2PART_UINT64_C(0x10000000, 20000000);
   uint64_t right = V8_2PART_UINT64_C(0x30000000, 00000000);
   uint64_t result = FUNCTION_CAST<F4>(buffer)(&left, &right);
   CHECK_EQ(1u, result);
 }
 
+TEST(AssemblerX64TestwOperations) {
+  typedef uint16_t (*F)(uint16_t * x);
+  CcTest::InitializeVM();
+  // Allocate an executable page of memory.
+  size_t actual_size;
+  byte* buffer = static_cast<byte*>(v8::base::OS::Allocate(
+      Assembler::kMinimalBufferSize, &actual_size, true));
+  CHECK(buffer);
+  Assembler assm(CcTest::i_isolate(), buffer, static_cast<int>(actual_size));
+
+  // Set rax with the ZF flag of the testl instruction.
+  Label done;
+  __ movq(rax, Immediate(1));
+  __ testw(Operand(arg1, 0), Immediate(0xf0f0));
+  __ j(not_zero, &done, Label::kNear);
+  __ movq(rax, Immediate(0));
+  __ bind(&done);
+  __ ret(0);
+
+  CodeDesc desc;
+  assm.GetCode(&desc);
+  // Call the function from C++.
+  uint16_t operand = 0x8000;
+  uint16_t result = FUNCTION_CAST<F>(buffer)(&operand);
+  CHECK_EQ(1u, result);
+}
 
 TEST(AssemblerX64XorlOperations) {
   CcTest::InitializeVM();
   // Allocate an executable page of memory.
   size_t actual_size;
   byte* buffer = static_cast<byte*>(v8::base::OS::Allocate(
       Assembler::kMinimalBufferSize, &actual_size, true));
   CHECK(buffer);
   Assembler assm(CcTest::i_isolate(), buffer, static_cast<int>(actual_size));
 
@@ skipping 1923 matching lines @@
 
   F1 f = FUNCTION_CAST<F1>(code->entry());
   for (int i = 0; i < kNumCases; ++i) {
     int res = f(i);
     PrintF("f(%d) = %d\n", i, res);
     CHECK_EQ(values[i], res);
   }
 }
 
 #undef __