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use super::{ Instruction, Address };
static Z: Address = Address::Memory(0);
static E: Address = Address::Memory(1);
static N: Address = Address::Memory(2);
static STACK_POINTER: Address = Address::Memory(4);
#[derive(Debug)]
pub(crate) enum ArgumentError {
UnknownInstruction,
TooMany,
TooFew,
NotLocation,
}
impl Instruction {
fn new1(name: &str, a: &Address) -> Instruction {
Instruction { name: name.to_string(), args: vec![a.clone()] }
}
fn new2(name: &str, a: &Address, b: &Address) -> Instruction {
Instruction { name: name.to_string(), args: vec![a.clone(), b.clone()] }
}
fn new3(name: &str, a: &Address, b: &Address, c: &Address) -> Instruction {
Instruction { name: name.to_string(), args: vec![a.clone(), b.clone(), c.clone()] }
}
fn new_subleq(a: &Address, b: &Address, c: &Address) -> Instruction {
if let Address::Constants(_) = c {
panic!("Constants cannot be the third subleq argument!");
}
Self::new3("subleq", a, b, c)
}
fn check_args_len(&self, expected: usize) -> Result<(), ArgumentError> {
if self.args.len() < expected {
return Err(ArgumentError::TooFew);
}
else if self.args.len() > expected {
return Err(ArgumentError::TooMany);
}
Ok(())
}
pub(crate) fn check_args(&self) -> Result<(), ArgumentError> {
match &*self.name {
"subleq" => {
self.check_args_len(3)?;
for arg in &self.args {
if ! arg.is_location() {
return Err(ArgumentError::NotLocation);
}
}
},
"jmp" | "jsr" => {
self.check_args_len(1)?;
if ! self.args[0].is_location() {
return Err(ArgumentError::NotLocation);
}
},
"beq" => {
self.check_args_len(2)?;
if ! self.args[1].is_location() {
return Err(ArgumentError::NotLocation);
}
},
"rts"
=> self.check_args_len(0)?,
"inc" | "dec"
=> self.check_args_len(1)?,
"add" | "sub" | "mov"
=> self.check_args_len(2)?,
_ => return Err(ArgumentError::UnknownInstruction),
}
Ok(())
}
pub(crate) fn collapse(&mut self, next: usize) -> Vec<Instruction> {
self.name = self.name.to_lowercase();
match &*self.name {
/* Primitive instrutions (need only one collapse) */
"subleq" => vec![self.clone()],
"jmp" => vec![
Instruction::new_subleq(&Z, &Z, &self.args[0]),
],
"inc" => vec![
Instruction::new_subleq(&N, &self.args[0], &Address::Instruction(next + 1)),
],
"dec" => vec![
Instruction::new_subleq(&E, &self.args[0], &Address::Instruction(next + 1)),
],
"add" => vec![
Instruction::new_subleq(&self.args[0], &Z, &Address::Instruction(next + 1)),
Instruction::new_subleq(&Z, &self.args[1], &Address::Instruction(next + 2)),
Instruction::new_subleq(&Z, &Z, &Address::Instruction(next + 3)),
],
"sub" => vec![
Instruction::new_subleq(&self.args[0], &self.args[1], &Address::Instruction(next + 1)),
],
"mov" => vec![
Instruction::new_subleq(&self.args[1], &self.args[1], &Address::Instruction(next + 1)),
Instruction::new_subleq(&self.args[0], &Z, &Address::Instruction(next + 2)),
Instruction::new_subleq(&Z, &self.args[1], &Address::Instruction(next + 3)),
Instruction::new_subleq(&Z, &Z, &Address::Instruction(next + 4)),
],
"beq" => vec![
Instruction::new_subleq(&self.args[0], &Z, &Address::Instruction(next + 2)),
Instruction::new_subleq(&Z, &Z, &Address::Instruction(next + 4)),
Instruction::new_subleq(&Z, &Z, &Address::Instruction(next + 3)),
Instruction::new_subleq(&Z, &self.args[0], &self.args[1] ),
],
/* Composite instructions (require two collapses) */
"jsr" => {
vec![
Instruction::new1("inc", &STACK_POINTER),
// We're modifying the generated mov instruction
// Every &self.args[1] value gets replaced with the value which SP points to
Instruction::new2("mov", &STACK_POINTER, &Address::InstructionOffset(next + 4, 0)),
Instruction::new2("mov", &STACK_POINTER, &Address::InstructionOffset(next + 4, 1)),
Instruction::new2("mov", &STACK_POINTER, &Address::InstructionOffset(next + 4, 7)),
Instruction::new2("mov", &Address::InstructionConstant(next + 6), &Z),
Instruction::new1("jmp", &self.args[0]),
]
},
"rts" => vec![
Instruction::new2("mov", &STACK_POINTER, &Address::InstructionOffset(next + 1, 3)),
Instruction::new2("mov", &Z, &Address::InstructionOffset(next + 3, 2)),
Instruction::new1("dec", &STACK_POINTER),
Instruction::new1("jmp", &Z),
],
_ => panic!("Unknown instruction {}!", self.name),
}
}
pub(crate) fn collapse_len(&self) -> usize {
match &*self.name {
"subleq" | "jmp" | "inc" | "dec" | "sub"
=> 1,
"add"
=> 3,
"mov" | "beq" | "rts"
=> 4,
"jsr"
=> 6,
_ => panic!("Unknown instruction {}!", self.name),
}
}
}
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