Add a Stack() class for specifying operand constraints for values on the stack. Add encoding recipes for RISC-V spill and fill instructions. Don't implement the encoding recipe functions yet since we don't have the stack slot layout yet.
Add a Stack() class for specifying operand constraints for values on the stack. Add encoding recipes for RISC-V spill and fill instructions. Don't implement the encoding recipe functions yet since we don't have the stack slot layout yet.