ARM64: Add and use SmiTagAndPush.

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 ea63bae4b15ef987efd65e833e3f52fecdf6ea9c..47a5d81907a9c042011138920545efa412fa1a05 100644
--- a/src/arm64/lithium-codegen-arm64.cc
+++ b/src/arm64/lithium-codegen-arm64.cc
@@ -5493,8 +5493,7 @@ void LCodeGen::DoDeferredStringCharCodeAt(LStringCharCodeAt* instr) {
   // Push the index as a smi. This is safe because of the checks in
   // DoStringCharCodeAt above.
   Register index = ToRegister(instr->index());
-  __ SmiTag(index);
-  __ Push(index);
+  __ SmiTagAndPush(index);
 
   CallRuntimeFromDeferred(Runtime::kHiddenStringCharCodeAt, 2, instr,
                           instr->context());
@@ -5543,8 +5542,7 @@ void LCodeGen::DoDeferredStringCharFromCode(LStringCharFromCode* instr) {
   __ Mov(result, 0);
 
   PushSafepointRegistersScope scope(this, Safepoint::kWithRegisters);
-  __ SmiTag(char_code);
-  __ Push(char_code);
+  __ SmiTagAndPush(char_code);
   CallRuntimeFromDeferred(Runtime::kCharFromCode, 1, instr, instr->context());
   __ StoreToSafepointRegisterSlot(x0, result);
 }