Better sequences for class id loading on ia32.

runtime/vm/intermediate_language_ia32.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_IA32.
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/intermediate_language.h"
 
 #include "vm/dart_entry.h"
@@ skipping 927 matching lines @@
   return LocationSummary::Make(isolate,
                                kNumInputs,
                                Location::RequiresRegister(),
                                LocationSummary::kNoCall);
 }
 
 
 void LoadClassIdInstr::EmitNativeCode(FlowGraphCompiler* compiler) {
   const Register object = locs()->in(0).reg();
   const Register result = locs()->out(0).reg();
-  Label not_smi, done;
+  Label done;
 
   // We don't use Assembler::LoadTaggedClassIdMayBeSmi() here---which uses
   // a conditional move instead, and requires an additional register---because
   // it is slower, probably due to branch prediction usually working just fine
   // in this case.
+  __ movl(result, Immediate(kSmiCid << 1));

[srdjan, 2014/07/11 18:23:30]

ASSERT result != object

[zra, 2014/07/11 18:28:41]

Done.

   __ testl(object, Immediate(kSmiTagMask));
-  __ j(NOT_ZERO, &not_smi, Assembler::kNearJump);
-  __ movl(result, Immediate(Smi::RawValue(kSmiCid)));
-  __ jmp(&done, Assembler::kNearJump);
-  __ Bind(&not_smi);
+  __ j(EQUAL, &done, Assembler::kNearJump);
   __ LoadClassId(result, object);
   __ SmiTag(result);
   __ Bind(&done);
 }
 
 
 CompileType LoadIndexedInstr::ComputeType() const {
   switch (class_id_) {
     case kArrayCid:
     case kImmutableArrayCid:
@@ skipping 5551 matching lines @@
   __ movl(EDX, Immediate(kInvalidObjectPointer));
   __ movl(EDX, Immediate(kInvalidObjectPointer));
 #endif
 }
 
 }  // namespace dart
 
 #undef __
 
 #endif  // defined TARGET_ARCH_IA32