Add LoadTaggedClassIdMayBeSmi to assembly and improve performance of inline cache stubs.

runtime/vm/assembler_arm64.cc

 // Copyright (c) 2014, 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"
 #if defined(TARGET_ARCH_ARM64)
 
 #include "vm/assembler.h"
 #include "vm/cpu.h"
 #include "vm/longjump.h"
@@ skipping 1055 matching lines @@
 }
 
 
 void Assembler::CompareClassId(
     Register object, intptr_t class_id, Register pp) {
   LoadClassId(TMP, object, pp);
   CompareImmediate(TMP, class_id, pp);
 }
 
 
+void Assembler::LoadTaggedClassIdMayBeSmi(Register result, Register object) {

[zra, 2014/06/04 18:55:00]

tsti(object, kSmiTagMask);
LoadImmediate(result, Smi::RawValue(kSmiCid), PP);
LoadClassId(temp, object, PP);  // Use TMP or pass in a scratch register for
'temp'.
csel(result, result, temp, EQ);

[srdjan, 2014/06/04 20:08:04]

Discussed offline, leave it as it be since LoadClassId with object Smi is not
possible.

+  Label load, done;
+  tsti(object, kSmiTagMask);
+  b(&load, NE);
+  LoadImmediate(result, Smi::RawValue(kSmiCid), PP);
+  b(&done);
+  Bind(&load);
+  LoadClassId(result, object, PP);
+  SmiTag(result);
+  Bind(&done);
+}
+
+
 // Frame entry and exit.
 void Assembler::ReserveAlignedFrameSpace(intptr_t frame_space) {
   // Reserve space for arguments and align frame before entering
   // the C++ world.
   if (frame_space != 0) {
     AddImmediate(SP, SP, -frame_space, kNoPP);
   }
   if (OS::ActivationFrameAlignment() > 1) {
     andi(SP, SP, ~(OS::ActivationFrameAlignment() - 1));
   }
@@ skipping 282 matching lines @@
     LoadImmediate(TMP, tags, pp);
     StoreFieldToOffset(TMP, instance_reg, Object::tags_offset(), pp);
   } else {
     b(failure);
   }
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_ARM64