bjoernager/rust
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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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30
compiler/rustc_mir_transform/src/copy_prop.rs
View file

@ -162,20 +162,22 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> {
}
fn visit_statement(&mut self, stmt: &mut Statement<'tcx>, loc: Location) {
match stmt.kind {
// When removing storage statements, we need to remove both (#107511).
StatementKind::StorageLive(l) | StatementKind::StorageDead(l)
if self.storage_to_remove.contains(l) =>
{
stmt.make_nop()
}
StatementKind::Assign(box (ref place, ref mut rvalue))
if place.as_local().is_some() =>
{
// Do not replace assignments.
self.visit_rvalue(rvalue, loc)
}
_ => self.super_statement(stmt, loc),
// When removing storage statements, we need to remove both (#107511).
if let StatementKind::StorageLive(l) | StatementKind::StorageDead(l) = stmt.kind
&& self.storage_to_remove.contains(l)
{
stmt.make_nop();
return
}
self.super_statement(stmt, loc);
// Do not leave tautological assignments around.
if let StatementKind::Assign(box (lhs, ref rhs)) = stmt.kind
&& let Rvalue::Use(Operand::Copy(rhs) | Operand::Move(rhs)) | Rvalue::CopyForDeref(rhs) = *rhs
&& lhs == rhs
{
stmt.make_nop();
}
}
}

24
compiler/rustc_mir_transform/src/ssa.rs
View file

@ -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
}