Optimize the typeof operator.

src/arm64/lithium-codegen-arm64.cc

Index: src/arm64/lithium-codegen-arm64.cc
diff --git a/src/arm64/lithium-codegen-arm64.cc b/src/arm64/lithium-codegen-arm64.cc
index 78348337270c4adc7be419f3320de71ac13d7e5b..c2a2ff364cc5bc80b1e29c0645a1383bbd68b067 100644
--- a/src/arm64/lithium-codegen-arm64.cc
+++ b/src/arm64/lithium-codegen-arm64.cc
@@ -5795,9 +5795,17 @@ void LCodeGen::DoTruncateDoubleToIntOrSmi(LTruncateDoubleToIntOrSmi* instr) {
 
 
 void LCodeGen::DoTypeof(LTypeof* instr) {
-  Register input = ToRegister(instr->value());
-  __ Push(input);
-  CallRuntime(Runtime::kTypeof, 1, instr);
+  DCHECK(ToRegister(instr->value()).is(x3));
+  DCHECK(ToRegister(instr->result()).is(x0));
+  Label end, do_call;
+  Register value_register = ToRegister(instr->value());
+  __ JumpIfNotSmi(value_register, &do_call);
+  __ Mov(x0, Immediate(isolate()->factory()->number_string()));
+  __ B(&end);
+  __ Bind(&do_call);
+  TypeofStub stub(isolate());
+  CallCode(stub.GetCode(), RelocInfo::CODE_TARGET, instr);
+  __ Bind(&end);
 }