Use UnboxedInt32 and UnboxedUint32 representation for LoadIndexedInstr

runtime/vm/assembler_x64.h

Index: runtime/vm/assembler_x64.h
diff --git a/runtime/vm/assembler_x64.h b/runtime/vm/assembler_x64.h
index 117f1e832e2b0377ac6c559caedc71bb682b567a..1e5bd04597ebc875d3c75f58f9b0c01abeb54d82 100644
--- a/runtime/vm/assembler_x64.h
+++ b/runtime/vm/assembler_x64.h
@@ -478,6 +478,8 @@ class Assembler : public ValueObject {
 
   void comisd(XmmRegister a, XmmRegister b);
   void cvtsi2sd(XmmRegister a, Register b);
+  // Only looks at first 32-bits of b.
+  void cvtsi2sd32(XmmRegister a, Register b);

[Vyacheslav Egorov (Google), 2014/10/09 19:08:58]

I'd think that ideally this instructions would use the same suffix schema as
other instructions.

s/cvtsi2sd/cvtsi2sdq/
s/cvtsi2sd32/cvtsi2sdl/

but maybe that would be too much changes around. 

[Cutch, 2014/10/09 20:48:22]

I had the same thought after Zach's suggestion. Done.

   void cvttsd2siq(Register dst, XmmRegister src);
 
   void cvtss2sd(XmmRegister dst, XmmRegister src);