bjoernager/rust
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Rollup merge of #95857 - ouz-a:mir-opt, r=oli-obk

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Allow multiple derefs to be splitted in deref_separator

Previously in #95649 only a single deref within projection was supported and multiple derefs caused a bunch of issues, this PR fixes those issues.

```@oli-obk``` helped a ton again ❤️
This commit is contained in:
Dylan DPC 2022-04-10 21:03:38 +02:00 • committed by GitHub
commit 78fc931355
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3 changed files with 117 additions and 8 deletions
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16
compiler/rustc_mir_transform/src/deref_separator.rs
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@ -11,6 +11,8 @@ pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
for (i, stmt) in data.statements.iter_mut().enumerate() {
match stmt.kind {
StatementKind::Assign(box (og_place, Rvalue::Ref(region, borrow_knd, place))) => {
let mut place_local = place.local;
let mut last_len = 0;
for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() {
if p_elem == ProjectionElem::Deref && !p_ref.projection.is_empty() {
// The type that we are derefing.
@ -23,15 +25,18 @@ pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
patch.add_statement(loc, StatementKind::StorageLive(temp));
// We are adding current p_ref's projections to our
// temp value.
let deref_place =
Place::from(p_ref.local).project_deeper(p_ref.projection, tcx);
// temp value, excluding projections we already covered.
let deref_place = Place::from(place_local)
.project_deeper(&p_ref.projection[last_len..], tcx);
patch.add_assign(
loc,
Place::from(temp),
Rvalue::Use(Operand::Move(deref_place)),
);
place_local = temp;
last_len = p_ref.projection.len();
// We are creating a place by using our temp value's location
// and copying derefed values which we need to create new statement.
let temp_place =
@ -50,11 +55,6 @@ pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
// Since our job with the temp is done it should be gone
let loc = Location { block: block, statement_index: i + 1 };
patch.add_statement(loc, StatementKind::StorageDead(temp));
// As all projections are off the base projection, if there are
// multiple derefs in the middle of projection, it might cause
// unsoundness, to not let that happen we break the loop.
break;
}
}
}