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Blocked MutatingUseContext::Projection for all locals of kind LocalKind::Temp. Added a cache of LocalKinds to CanConstProp

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This commit is contained in:
Félix Fischer 2020-04-22 21:53:51 -04:00
parent 6316601ec4
commit 3fd2d4aaa6
1 changed files with 13 additions and 4 deletions
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17
src/librustc_mir/transform/const_prop.rs
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@ -766,6 +766,8 @@ struct CanConstProp {
can_const_prop: IndexVec<Local, ConstPropMode>,
// false at the beginning, once set, there are not allowed to be any more assignments
found_assignment: BitSet<Local>,
// Cache of locals' information
local_kinds: IndexVec<Local, LocalKind>,
}
impl CanConstProp {
@ -774,6 +776,10 @@ impl CanConstProp {
let mut cpv = CanConstProp {
can_const_prop: IndexVec::from_elem(ConstPropMode::FullConstProp, &body.local_decls),
found_assignment: BitSet::new_empty(body.local_decls.len()),
local_kinds: IndexVec::from_fn_n(
|local| body.local_kind(local),
body.local_decls.len(),
),
};
for (local, val) in cpv.can_const_prop.iter_enumerated_mut() {
// cannot use args at all
@ -781,9 +787,8 @@ impl CanConstProp {
// lint for x != y
// FIXME(oli-obk): lint variables until they are used in a condition
// FIXME(oli-obk): lint if return value is constant
let local_kind = body.local_kind(local);
if local_kind == LocalKind::Arg || local_kind == LocalKind::Var {
if cpv.local_kinds[local] == LocalKind::Arg || cpv.local_kinds[local] == LocalKind::Var
{
*val = ConstPropMode::OnlyPropagateInto;
trace!("local {:?} can't be const propagated because it's not a temporary", local);
}
@ -811,8 +816,12 @@ impl<'tcx> Visitor<'tcx> for CanConstProp {
| NonMutatingUse(NonMutatingUseContext::Move)
| NonMutatingUse(NonMutatingUseContext::Inspect)
| NonMutatingUse(NonMutatingUseContext::Projection)
| MutatingUse(MutatingUseContext::Projection)
| NonUse(_) => {}
MutatingUse(MutatingUseContext::Projection) => {
if self.local_kinds[local] != LocalKind::Temp {
self.can_const_prop[local] = ConstPropMode::NoPropagation;
}
}
_ => {
trace!("local {:?} can't be propagaged because it's used: {:?}", local, context);
self.can_const_prop[local] = ConstPropMode::NoPropagation;