[turbofan] Use CompareNilIC for abstract equality with null/undefined.

src/full-codegen/x64/full-codegen-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/code-stubs.h"
 #include "src/codegen.h"
 #include "src/debug/debug.h"
@@ skipping 4863 matching lines @@
   PrepareForBailoutBeforeSplit(expr, true, if_true, if_false);
   if (expr->op() == Token::EQ_STRICT) {
     Heap::RootListIndex nil_value = nil == kNullValue ?
         Heap::kNullValueRootIndex :
         Heap::kUndefinedValueRootIndex;
     __ CompareRoot(rax, nil_value);
     Split(equal, if_true, if_false, fall_through);
   } else {
     Handle<Code> ic = CompareNilICStub::GetUninitialized(isolate(), nil);
     CallIC(ic, expr->CompareOperationFeedbackId());
-    __ testp(rax, rax);
-    Split(not_zero, if_true, if_false, fall_through);
+    __ CompareRoot(rax, Heap::kTrueValueRootIndex);
+    Split(equal, if_true, if_false, fall_through);
   }
   context()->Plug(if_true, if_false);
 }
 
 
 void FullCodeGenerator::VisitThisFunction(ThisFunction* expr) {
   __ movp(rax, Operand(rbp, JavaScriptFrameConstants::kFunctionOffset));
   context()->Plug(rax);
 }
 
@@ skipping 180 matching lines @@
             Assembler::target_address_at(call_target_address,
                                          unoptimized_code));
   return OSR_AFTER_STACK_CHECK;
 }
 
 
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_TARGET_ARCH_X64