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Merge return place with other locals in CopyProp.

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This commit is contained in:
Camille GILLOT 2023-05-14 11:25:47 +00:00
parent bc888958c9
commit f40f235879
19 changed files with 601 additions and 218 deletions
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24
compiler/rustc_mir_transform/src/ssa.rs
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@ -267,11 +267,6 @@ fn compute_copy_classes(ssa: &mut SsaVisitor, body: &Body<'_>) -> IndexVec<Local
for &local in &ssa.assignment_order {
debug!(?local);
if local == RETURN_PLACE {
// `_0` is special, we cannot rename it.
continue;
}
// This is not SSA: mark that we don't know the value.
debug!(assignments = ?ssa.assignments[local]);
let Set1::One(LocationExtended::Plain(loc)) = ssa.assignments[local] else { continue };
@ -290,7 +285,23 @@ fn compute_copy_classes(ssa: &mut SsaVisitor, body: &Body<'_>) -> IndexVec<Local
// We visit in `assignment_order`, ie. reverse post-order, so `rhs` has been
// visited before `local`, and we just have to copy the representing local.
copies[local] = copies[rhs];
let head = copies[rhs];
if local == RETURN_PLACE {
// `_0` is special, we cannot rename it. Instead, rename the class of `rhs` to
// `RETURN_PLACE`. This is only possible if the class head is a temporary, not an
// argument.
if body.local_kind(head) != LocalKind::Temp {
continue;
}
for h in copies.iter_mut() {
if *h == head {
*h = RETURN_PLACE;
}
}
} else {
copies[local] = head;
}
ssa.direct_uses[rhs] -= 1;
}
@ -302,6 +313,7 @@ fn compute_copy_classes(ssa: &mut SsaVisitor, body: &Body<'_>) -> IndexVec<Local
for &head in copies.iter() {
assert_eq!(copies[head], head);
}
debug_assert_eq!(copies[RETURN_PLACE], RETURN_PLACE);
copies
}