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

runtime/vm/assembler_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"
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/cpu.h"
@@ skipping 2638 matching lines @@
 
 
 void Assembler::CompareClassId(Register object,
                                intptr_t class_id,
                                Register scratch) {
   LoadClassId(scratch, object);
   cmpl(scratch, Immediate(class_id));
 }
 
 
+void Assembler::LoadTaggedClassIdMayBeSmi(Register result, Register object) {
+  testl(object, Immediate(kSmiTagMask));
+  Label not_smi, done;
+  j(NOT_ZERO, &not_smi, Assembler::kNearJump);
+  movl(result, Immediate(Smi::RawValue(kSmiCid)));
+  jmp(&done, Assembler::kNearJump);
+  Bind(&not_smi);
+  LoadClassId(result, object);
+  SmiTag(result);
+  Bind(&done);
+}
+
+
 static const char* cpu_reg_names[kNumberOfCpuRegisters] = {
   "eax", "ecx", "edx", "ebx", "esp", "ebp", "esi", "edi"
 };
 
 
 const char* Assembler::RegisterName(Register reg) {
   ASSERT((0 <= reg) && (reg < kNumberOfCpuRegisters));
   return cpu_reg_names[reg];
 }
 
 
 static const char* xmm_reg_names[kNumberOfXmmRegisters] = {
   "xmm0", "xmm1", "xmm2", "xmm3", "xmm4", "xmm5", "xmm6", "xmm7"
 };
 
 
 const char* Assembler::FpuRegisterName(FpuRegister reg) {
   ASSERT((0 <= reg) && (reg < kNumberOfXmmRegisters));
   return xmm_reg_names[reg];
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32