Cleaner version of IA32 stub optimization

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"  // NOLINT
 #if defined(TARGET_ARCH_IA32)
 
 #include "vm/assembler.h"
 #include "vm/code_generator.h"
 #include "vm/cpu.h"
@@ skipping 2885 matching lines @@
   SmiUntag(object);
   j(NOT_CARRY, is_smi, kNearJump);
   // Load cid: can't use LoadClassId, object is untagged. Use TIMES_2 scale
   // factor in the addressing mode to compensate for this.
   movzxw(scratch, Address(object, TIMES_2, class_id_offset));
   cmpl(scratch, Immediate(class_id));
 }
 
 
 void Assembler::LoadClassIdMayBeSmi(Register result, Register object) {
-  ASSERT(result != object);
-  static const intptr_t kSmiCidSource = kSmiCid << RawObject::kClassIdTagPos;
+  if (result == object) {
+    Label smi, join;
 
-  // Make a dummy "Object" whose cid is kSmiCid.
-  movl(result, Immediate(reinterpret_cast<int32_t>(&kSmiCidSource) + 1));
+    testl(object, Immediate(kSmiTagMask));
+    j(EQUAL, &smi, Assembler::kNearJump);
+    LoadClassId(result, object);
+    jmp(&join, Assembler::kNearJump);
 
-  // Check if object (in tmp) is a Smi.
-  testl(object, Immediate(kSmiTagMask));
+    Bind(&smi);
+    movl(result, Immediate(kSmiCid));
 
-  // If the object is not a Smi, use the original object to load the cid.
-  // Otherwise, the dummy object is used, and the result is kSmiCid.
-  cmovne(result, object);
-  LoadClassId(result, result);
+    Bind(&join);
+  } else {
+    ASSERT(result != object);
+    static const intptr_t kSmiCidSource = kSmiCid << RawObject::kClassIdTagPos;
+
+    // Make a dummy "Object" whose cid is kSmiCid.
+    movl(result, Immediate(reinterpret_cast<int32_t>(&kSmiCidSource) + 1));
+
+    // Check if object (in tmp) is a Smi.
+    testl(object, Immediate(kSmiTagMask));
+
+    // If the object is not a Smi, use the original object to load the cid.
+    // Otherwise, the dummy object is used, and the result is kSmiCid.
+    cmovne(result, object);
+    LoadClassId(result, result);
+  }
 }
 
 
 void Assembler::LoadTaggedClassIdMayBeSmi(Register result, Register object) {
-  LoadClassIdMayBeSmi(result, object);
-  // Tag the result.
-  SmiTag(result);
+  if (result == object) {
+    Label smi, join;
+
+    testl(object, Immediate(kSmiTagMask));
+    j(EQUAL, &smi, Assembler::kNearJump);
+    LoadClassId(result, object);
+    SmiTag(result);
+    jmp(&join, Assembler::kNearJump);
+
+    Bind(&smi);
+    movl(result, Immediate(Smi::RawValue(kSmiCid)));
+
+    Bind(&join);
+  } else {
+    LoadClassIdMayBeSmi(result, object);
+    SmiTag(result);
+  }
 }
 
 
 Address Assembler::ElementAddressForIntIndex(bool is_external,
                                              intptr_t cid,
                                              intptr_t index_scale,
                                              Register array,
                                              intptr_t index) {
   if (is_external) {
     return Address(array, index * index_scale);
@@ skipping 59 matching lines @@
 
 const char* Assembler::FpuRegisterName(FpuRegister reg) {
   ASSERT((0 <= reg) && (reg < kNumberOfXmmRegisters));
   return xmm_reg_names[reg];
 }
 
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_IA32