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Remove redundant union check in KnownPanicsLint const prop #124550

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Merged
merged 1 commit into from
Apr 30, 2024
Merged

Remove redundant union check in KnownPanicsLint const prop #124550

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47 changes: 18 additions & 29 deletions compiler/rustc_mir_transform/src/known_panics_lint.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -583,33 +583,21 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> {
val.into()
}

Aggregate(ref kind, ref fields) => {
// Do not const prop union fields as they can be
// made to produce values that don't match their
// underlying layout's type (see ICE #121534).
// If the last element of the `Adt` tuple
// is `Some` it indicates the ADT is a union
if let AggregateKind::Adt(_, _, _, _, Some(_)) = **kind {
return None;
};
Value::Aggregate {
fields: fields
.iter()
.map(|field| {
self.eval_operand(field).map_or(Value::Uninit, Value::Immediate)
})
.collect(),
variant: match **kind {
AggregateKind::Adt(_, variant, _, _, _) => variant,
AggregateKind::Array(_)
| AggregateKind::Tuple
| AggregateKind::RawPtr(_, _)
| AggregateKind::Closure(_, _)
| AggregateKind::Coroutine(_, _)
| AggregateKind::CoroutineClosure(_, _) => VariantIdx::ZERO,
},
}
}
Aggregate(ref kind, ref fields) => Value::Aggregate {
fields: fields
.iter()
.map(|field| self.eval_operand(field).map_or(Value::Uninit, Value::Immediate))
.collect(),
variant: match **kind {
AggregateKind::Adt(_, variant, _, _, _) => variant,
AggregateKind::Array(_)
| AggregateKind::Tuple
| AggregateKind::RawPtr(_, _)
| AggregateKind::Closure(_, _)
| AggregateKind::Coroutine(_, _)
| AggregateKind::CoroutineClosure(_, _) => VariantIdx::ZERO,
},
},

Repeat(ref op, n) => {
trace!(?op, ?n);
Expand Down Expand Up @@ -897,8 +885,9 @@ impl CanConstProp {
for (local, val) in cpv.can_const_prop.iter_enumerated_mut() {
let ty = body.local_decls[local].ty;
if ty.is_union() {
// Do not const prop unions as they can
// ICE during layout calc
// Unions are incompatible with the current implementation of
// const prop because Rust has no concept of an active
// variant of a union
*val = ConstPropMode::NoPropagation;
} else {
match tcx.layout_of(param_env.and(ty)) {
Expand Down