remove dead code in fast double elements

* src/x64/lithium-codegen-x64.cc (DoLoadKeyedFastDoubleElement)
  (DoStoreKeyedFastDoubleElement): Remove set but unused variables.

BUG=
TEST=Fixes a build with gcc-4.6.

Review URL: http://codereview.chromium.org/7491041
Patch from Andy Wingo <wingo@igalia.com>.

git-svn-id: http://v8.googlecode.com/svn/branches/bleeding_edge@8738 ce2b1a6d-e550-0410-aec6-3dcde31c8c00

src/ia32/lithium-codegen-ia32.cc

@@ -2232,7 +2232,6 @@ void LCodeGen::DoLoadKeyedFastElement(LLoadKeyedFastElement* instr) {
 
 void LCodeGen::DoLoadKeyedFastDoubleElement(
     LLoadKeyedFastDoubleElement* instr) {
-  Register elements = ToRegister(instr->elements());
   XMMRegister result = ToDoubleRegister(instr->result());
 
   if (instr->hydrogen()->RequiresHoleCheck()) {
@@ -3097,7 +3096,6 @@ void LCodeGen::DoStoreKeyedFastElement(LStoreKeyedFastElement* instr) {
 void LCodeGen::DoStoreKeyedFastDoubleElement(
     LStoreKeyedFastDoubleElement* instr) {
   XMMRegister value = ToDoubleRegister(instr->value());
-  Register elements = ToRegister(instr->elements());
   Register key = instr->key()->IsRegister() ? ToRegister(instr->key()) : no_reg;
   Label have_value;
 

src/x64/lithium-codegen-x64.cc

@@ -2246,7 +2246,6 @@ void LCodeGen::DoLoadKeyedFastElement(LLoadKeyedFastElement* instr) {
 
 void LCodeGen::DoLoadKeyedFastDoubleElement(
     LLoadKeyedFastDoubleElement* instr) {
-  Register elements = ToRegister(instr->elements());
   XMMRegister result(ToDoubleRegister(instr->result()));
 
   if (instr->hydrogen()->RequiresHoleCheck()) {
@@ -3101,14 +3100,11 @@ void LCodeGen::DoStoreKeyedFastElement(LStoreKeyedFastElement* instr) {
 void LCodeGen::DoStoreKeyedFastDoubleElement(
     LStoreKeyedFastDoubleElement* instr) {
   XMMRegister value = ToDoubleRegister(instr->value());
-  Register elements = ToRegister(instr->elements());
   Label have_value;
 
   __ ucomisd(value, value);
   __ j(parity_odd, &have_value);  // NaN.
 
-  ExternalReference canonical_nan_reference =
-      ExternalReference::address_of_canonical_non_hole_nan();
   __ Set(kScratchRegister, BitCast<uint64_t>(
       FixedDoubleArray::canonical_not_the_hole_nan_as_double()));
   __ movq(value, kScratchRegister);