Assert fail in case of WCHAR

[HuanjunWang]

Target: x86_64-pc-windows-msvc

Assert failed at below line in case of WCHAR
BinaryOperator* int8_dec = BinaryOperator::Create(Instruction::Xor, int8_20, const_key, "xor", label_for_body);

int8_20 has a type with 16 bits and const_key has 8.
Changing const_key to 16 bits in case of wchar will fix this in my try, but you may have better solution.

[shagfu]

llvm是强制类型校验，s16和s8类型不匹配，所以会报错，可以将key扩展s16