Implement IsNullCheck for CheckClassInstr. If input is nullable expected type, then check for null …

runtime/vm/intermediate_language_x64.cc

 // Copyright (c) 2013, the Dart project authors.  Please see the AUTHORS file
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
 #include "vm/globals.h"  // Needed here to get TARGET_ARCH_X64.
 #if defined(TARGET_ARCH_X64)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
@@ skipping 4101 matching lines @@
   comparison()->EmitBranchCode(compiler, this);
 }
 
 
 LocationSummary* CheckClassInstr::MakeLocationSummary() const {
   const intptr_t kNumInputs = 1;
   const intptr_t kNumTemps = 0;
   LocationSummary* summary =
       new LocationSummary(kNumInputs, kNumTemps, LocationSummary::kNoCall);
   summary->set_in(0, Location::RequiresRegister());
-  if (!null_check()) {
+  if (!IsNullCheck()) {
     summary->AddTemp(Location::RequiresRegister());
   }
   return summary;
 }
 
 
 void CheckClassInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
-  if (null_check()) {
+  if (IsNullCheck()) {
     Label* deopt = compiler->AddDeoptStub(deopt_id(),
                                           kDeoptCheckClass);
     const Immediate& raw_null =
         Immediate(reinterpret_cast<intptr_t>(Object::null()));
     __ cmpq(locs()->in(0).reg(), raw_null);
     __ j(EQUAL, deopt);
     return;
   }
 
   ASSERT((unary_checks().GetReceiverClassIdAt(0) != kSmiCid) ||
@@ skipping 443 matching lines @@
                          PcDescriptors::kOther,
                          locs());
   __ Drop(2);  // Discard type arguments and receiver.
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_X64