[turbofan] Improve codegen for 8- and 16-bit memory comparisons on Intel platforms

test/cctest/test-assembler-x64.cc

Index: test/cctest/test-assembler-x64.cc
diff --git a/test/cctest/test-assembler-x64.cc b/test/cctest/test-assembler-x64.cc
index b11b0d39374bdb51a4650bb69c061da055084792..55186571621f66d92b66418d27afcb54f8739377 100644
--- a/test/cctest/test-assembler-x64.cc
+++ b/test/cctest/test-assembler-x64.cc
@@ -201,7 +201,7 @@ TEST(AssemblerX64ImulOperation) {
   CHECK_EQ(-1, result);
 }
 
-TEST(AssemblerX64testbwOperation) {
+TEST(AssemblerX64testbwqOperation) {
   CcTest::InitializeVM();
   v8::HandleScope scope(CcTest::isolate());
   // Allocate an executable page of memory.
@@ -338,6 +338,12 @@ TEST(AssemblerX64testbwOperation) {
   __ testw(r11, r12);
   __ j(zero, &bad);
 
+  // Test sign-extended imediate tests
+  __ movq(r11, Immediate(2));
+  __ shlq(r11, Immediate(32));
+  __ testq(r11, Immediate(-1));
+  __ j(zero, &bad);
+
   // All tests passed
   __ movq(rax, Immediate(1));
   __ jmp(&done);