Enables optimization on MIPS

runtime/vm/assembler_mips.cc

Index: runtime/vm/assembler_mips.cc
===================================================================
--- runtime/vm/assembler_mips.cc	(revision 23163)
+++ runtime/vm/assembler_mips.cc	(working copy)
@@ -204,10 +204,14 @@
 }
 
 
-void Assembler::CompareObject(Register rd, Register rn, const Object& object) {
+void Assembler::CompareObject(Register rd1, Register rd2,
+                              Register rn, const Object& object) {
   ASSERT(rn != TMP1);
+  ASSERT(rd1 != TMP1);
+  ASSERT(rd1 != rd2);
   LoadObject(TMP1, object);
-  subu(rd, rn, TMP1);
+  slt(rd1, rn, TMP1);
+  slt(rd2, TMP1, rn);

[regis, 2013/05/24 22:32:59]

Do you always need both results? Would it make sense to split this function?

[zra, 2013/05/24 23:25:47]

Not always, no. Both are needed only when the object is a Smi and the comparison
is something other than == or !=. The problem is that in
ControlInstruction::EmitBranchOnCondition you won't know which of the split
CompareObjects came before, if I understand your suggestion correctly.

 }