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simplify window passes

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This commit is contained in:
nora 2022-04-16 00:37:50 +02:00
parent 3eb9486a8c
commit 31f2304a30
1 changed files with 55 additions and 53 deletions
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108
rust2/src/opts.rs
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@ -160,42 +160,65 @@ fn pass_find_set_null(ir: &mut Ir<'_>) {
/// pass that replaces `SetN(n) Add(m)` with `SetN(n + m)`
fn pass_set_n(ir: &mut Ir<'_>) {
let stmts = &mut ir.stmts;
for i in 0..stmts.len() {
let a = &mut stmts[i];
if let StmtKind::Loop(body) = &mut a.kind {
pass_set_n(body);
}
if i >= stmts.len() - 1 {
break; // we are the last element
}
let a = &stmts[i];
two_window_pass(ir, pass_set_n, |a, b| {
if let StmtKind::SetN(before) = a.kind() {
let b = &stmts[i + 1];
let new = match b.kind() {
StmtKind::Add(n) => StmtKind::SetN(before.wrapping_add(*n)),
StmtKind::Sub(n) => StmtKind::SetN(before.wrapping_sub(*n)),
_ => {
continue;
return WindowPassAction::None;
}
};
let span = a.span.merge(b.span);
stmts.remove(i + 1);
stmts[i] = Stmt::new(new, span);
return WindowPassAction::Merge(new);
}
}
WindowPassAction::None
});
}
/// pass that replaces `Left(5) Right(3)` with `Left(2)`
fn pass_cancel_left_right_add_sub(ir: &mut Ir<'_>) {
two_window_pass(ir, pass_cancel_left_right_add_sub, |a, b| {
match (a.kind(), b.kind()) {
(StmtKind::Right(r), StmtKind::Left(l)) | (StmtKind::Left(l), StmtKind::Right(r)) => {
let new = match r.cmp(l) {
Ordering::Equal => return WindowPassAction::RemoveBoth,
Ordering::Less => StmtKind::Left(l - r),
Ordering::Greater => StmtKind::Right(r - l),
};
WindowPassAction::Merge(new)
}
(StmtKind::Add(r), StmtKind::Sub(l)) | (StmtKind::Sub(l), StmtKind::Add(r)) => {
let new = match r.cmp(l) {
Ordering::Equal => return WindowPassAction::RemoveBoth,
Ordering::Less => StmtKind::Sub(l - r),
Ordering::Greater => StmtKind::Add(r - l),
};
WindowPassAction::Merge(new)
}
_ => WindowPassAction::None,
}
})
}
enum WindowPassAction<'ir> {
None,
Merge(StmtKind<'ir>),
RemoveBoth,
}
fn two_window_pass<'ir, P, F>(ir: &mut Ir<'ir>, pass_recur: P, action: F)
where
P: Fn(&mut Ir<'ir>),
F: Fn(&Stmt<'ir>, &Stmt<'ir>) -> WindowPassAction<'ir>,
{
let stmts = &mut ir.stmts;
let mut i = 0;
while i < stmts.len() {
let a = &mut stmts[i];
if let StmtKind::Loop(body) = &mut a.kind {
pass_cancel_left_right_add_sub(body);
pass_recur(body);
}
if i >= stmts.len() - 1 {
@ -205,44 +228,23 @@ fn pass_cancel_left_right_add_sub(ir: &mut Ir<'_>) {
let a = &stmts[i];
let b = &stmts[i + 1];
match (a.kind(), b.kind()) {
(StmtKind::Right(r), StmtKind::Left(l)) | (StmtKind::Left(l), StmtKind::Right(r)) => {
let new = match r.cmp(l) {
Ordering::Equal => {
// remove both
stmts.remove(i + 1);
stmts.remove(i);
continue;
}
Ordering::Less => StmtKind::Left(l - r),
Ordering::Greater => StmtKind::Right(r - l),
};
let merged_span = a.span.merge(b.span);
let span = a.span.merge(b.span);
stmts.remove(i + 1);
stmts[i] = Stmt::new(new, span);
// don't increment i, maybe the next one matches as well (<><)
}
(StmtKind::Add(r), StmtKind::Sub(l)) | (StmtKind::Sub(l), StmtKind::Add(r)) => {
let new = match r.cmp(l) {
Ordering::Equal => {
// remove both
stmts.remove(i + 1);
stmts.remove(i);
continue;
}
Ordering::Less => StmtKind::Sub(l - r),
Ordering::Greater => StmtKind::Add(r - l),
};
let result = action(a, b);
let span = a.span.merge(b.span);
stmts.remove(i + 1);
stmts[i] = Stmt::new(new, span);
// don't increment i, maybe the next one matches as well (<><)
}
_ => {
match result {
WindowPassAction::None => {
// only increment i if we haven't removed anything
i += 1;
}
WindowPassAction::RemoveBoth => {
stmts.remove(i);
stmts.remove(i + 1);
}
WindowPassAction::Merge(new) => {
stmts.remove(i + 1);
stmts[i] = Stmt::new(new, merged_span);
}
}
}
}