X64 Crankshaft: Implement DoubleToI in optimizing compiler.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
===================================================================
--- src/x64/lithium-x64.cc	(revision 6879)
+++ src/x64/lithium-x64.cc	(working copy)
@@ -1577,12 +1577,8 @@
       return AssignPointerMap(Define(result, result_temp));
     } else {
       ASSERT(to.IsInteger32());
-      bool needs_temp = instr->CanTruncateToInt32() &&
-          !CpuFeatures::IsSupported(SSE3);
-      LOperand* value = needs_temp ?
-          UseTempRegister(instr->value()) : UseRegister(instr->value());
-      LOperand* temp = needs_temp ? TempRegister() : NULL;
-      return AssignEnvironment(DefineAsRegister(new LDoubleToI(value, temp)));
+      LOperand* value = UseRegister(instr->value());
+      return AssignEnvironment(DefineAsRegister(new LDoubleToI(value)));
     }
   } else if (from.IsInteger32()) {
     if (to.IsTagged()) {