Avoid re-tagging of the index register in optimized byte array access.

runtime/vm/flow_graph_compiler_x64.cc

Index: runtime/vm/flow_graph_compiler_x64.cc
===================================================================
--- runtime/vm/flow_graph_compiler_x64.cc	(revision 18444)
+++ runtime/vm/flow_graph_compiler_x64.cc	(working copy)
@@ -1322,25 +1322,6 @@
 }
 
 
-void FlowGraphCompiler::LoadDoubleOrSmiToFpu(FpuRegister result,
-                                             Register reg,
-                                             Register temp,
-                                             Label* not_double_or_smi) {
-  Label is_smi, done;
-  __ testq(reg, Immediate(kSmiTagMask));
-  __ j(ZERO, &is_smi);
-  __ CompareClassId(reg, kDoubleCid);
-  __ j(NOT_EQUAL, not_double_or_smi);
-  __ movsd(result, FieldAddress(reg, Double::value_offset()));
-  __ jmp(&done);
-  __ Bind(&is_smi);
-  __ movq(temp, reg);
-  __ SmiUntag(temp);
-  __ cvtsi2sd(result, temp);
-  __ Bind(&done);
-}
-
-
 void FlowGraphCompiler::SaveLiveRegisters(LocationSummary* locs) {
   // TODO(vegorov): consider saving only caller save (volatile) registers.
   const intptr_t xmm_regs_count = locs->live_registers()->fpu_regs_count();