Remove unused last_pc_ in AssemblerX64.

src/x64/lithium-x64.cc

Index: src/x64/lithium-x64.cc
diff --git a/src/x64/lithium-x64.cc b/src/x64/lithium-x64.cc
index 0e851bc17508054106d673fb6eab89b4151df99f..35ff8a7ab24818ee56acc90547be56dcc01e4d50 100644
--- a/src/x64/lithium-x64.cc
+++ b/src/x64/lithium-x64.cc
@@ -1613,10 +1613,8 @@ LInstruction* LChunkBuilder::DoChange(HChange* instr) {
       LOperand* value = UseRegister(instr->value());
       bool needs_check = !instr->value()->type().IsSmi();
       if (needs_check) {
-        LOperand* xmm_temp =
-            (instr->CanTruncateToInt32() && CpuFeatures::IsSupported(SSE3))
-            ? NULL
-            : FixedTemp(xmm1);
+        LOperand* xmm_temp = instr->CanTruncateToInt32() ? NULL
+                                                         : FixedTemp(xmm1);
         LTaggedToI* res = new LTaggedToI(value, xmm_temp);
         return AssignEnvironment(DefineSameAsFirst(res));
       } else {