Cleanup of class id loading sequences.

runtime/vm/assembler_arm64.cc

Index: runtime/vm/assembler_arm64.cc
===================================================================
--- runtime/vm/assembler_arm64.cc	(revision 38283)
+++ runtime/vm/assembler_arm64.cc	(working copy)
@@ -1095,25 +1095,22 @@
 
 
 void Assembler::LoadTaggedClassIdMayBeSmi(Register result, Register object) {
-  ASSERT(result != TMP);
-  ASSERT(object != 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..
   LoadObject(result, Object::null_object(), PP);
   // Check if the object is a Smi.
-  tsti(TMP, kSmiTagMask);
-  // If the object *is* a Smi, load the null object into tmp. o/w leave alone.
-  csel(TMP, result, TMP, EQ);
+  tsti(object, kSmiTagMask);
+  // If the object *is* a Smi, use the null object instead. o/w leave alone.
+  csel(object, result, object, EQ);
   // 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, PP);
+  LoadClassId(result, object, PP);
 
-  LoadImmediate(TMP, kSmiCid, PP);
+  LoadImmediate(object, kSmiCid, PP);
   // If object is a Smi, move the Smi cid into result. o/w leave alone.
-  csel(result, TMP, result, EQ);
+  csel(result, object, result, EQ);
   // Finally, tag the result.
   SmiTag(result);
 }