Use sarq on x64

BUG=
R=bmeurer@chromium.org

Review URL: https://codereview.chromium.org/219043003

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@20350 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/x64/lithium-codegen-x64.cc

@@ -5608,10 +5608,10 @@ void LCodeGen::DoLoadFieldByIndex(LLoadFieldByIndex* instr) {
 
   Label out_of_object, done;
   __ Move(kScratchRegister, Smi::FromInt(1));
-  __ testq(index, kScratchRegister);
+  __ testp(index, kScratchRegister);
   __ j(not_zero, deferred->entry());
 
-  __ sar(index, Immediate(1));
+  __ sarp(index, Immediate(1));
 
   __ SmiToInteger32(index, index);
   __ cmpl(index, Immediate(0));