Cleanup of class id loading sequences.

runtime/vm/assembler_mips.cc

Index: runtime/vm/assembler_mips.cc
===================================================================
--- runtime/vm/assembler_mips.cc	(revision 38283)
+++ runtime/vm/assembler_mips.cc	(working copy)
@@ -692,25 +692,22 @@
 
 
 void Assembler::LoadTaggedClassIdMayBeSmi(Register result, Register object) {
-  ASSERT(object != TMP);
-  ASSERT(result != TMP);
+  ASSERT(result != object);
 
-  // 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);
+  andi(CMPRES1, object, Immediate(kSmiTagMask));
+  // If the object *is* a Smi, use the null object instead. o/w leave alone.
+  movz(object, 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);
+  LoadClassId(result, object);
 
-  LoadImmediate(TMP, kSmiCid);
+  LoadImmediate(object, kSmiCid);
   // If object is a Smi, move the Smi cid into result. o/w leave alone.
-  movz(result, TMP, CMPRES1);
+  movz(result, object, CMPRES1);
   // Finally, tag the result.
   SmiTag(result);
 }