Cleanup of class id loading sequences.

runtime/vm/assembler_mips.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_MIPS)
 
 #include "vm/assembler.h"
 #include "vm/longjump.h"
 #include "vm/runtime_entry.h"
@@ skipping 674 matching lines @@
   const intptr_t table_offset_in_isolate =
       Isolate::class_table_offset() + ClassTable::table_offset();
   lw(result, Address(result, table_offset_in_isolate));
   sll(TMP, TMP, 2);
   addu(result, result, TMP);
   lw(result, Address(result));
 }
 
 
 void Assembler::LoadTaggedClassIdMayBeSmi(Register result, Register object) {
-  ASSERT(object != TMP);
-  ASSERT(result != TMP);
+  static const intptr_t kSmiCidSource = kSmiCid << RawObject::kClassIdTagPos;
 
-  // Make a copy of object since result and object can be the same register.
-  mov(TMP, object);
-  // Load up a null object. We only need it so we can use LoadClassId on it in
-  // the case that object is a Smi.
-  LoadImmediate(result, reinterpret_cast<intptr_t>(Object::null()));
-  // Check if the object is a Smi.
-  andi(CMPRES1, TMP, Immediate(kSmiTagMask));
-  // If the object *is* a Smi, load the null object into tmp. o/w leave alone.
-  movz(TMP, result, CMPRES1);
-  // Loads either the cid of the object if it isn't a Smi, or the cid of null
-  // if it is a Smi, which will be ignored.
-  LoadClassId(result, TMP);
-
-  LoadImmediate(TMP, kSmiCid);
-  // If object is a Smi, move the Smi cid into result. o/w leave alone.
+  LoadImmediate(TMP, reinterpret_cast<int32_t>(&kSmiCidSource) + 1);
+  andi(CMPRES1, object, Immediate(kSmiTagMask));
+  if (result != object) {
+    mov(result, object);
+  }
   movz(result, TMP, CMPRES1);
-  // Finally, tag the result.
+  LoadClassId(result, result);
   SmiTag(result);
 }
 
 
 void Assembler::EnterFrame() {
   ASSERT(!in_delay_slot_);
   addiu(SP, SP, Immediate(-2 * kWordSize));
   sw(RA, Address(SP, 1 * kWordSize));
   sw(FP, Address(SP, 0 * kWordSize));
   mov(FP, SP);
@@ skipping 429 matching lines @@
     Emit(reinterpret_cast<int32_t>(message));
     Bind(&msg);
     break_(Instr::kMsgMessageCode);
   }
 #endif
 }
 
 }  // namespace dart
 
 #endif  // defined TARGET_ARCH_MIPS