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|
//! A less precise version of `MaybeInitializedPlaces` whose domain is entire locals.
//!
//! A local will be maybe initialized if *any* projections of that local might be initialized.
use crate::{CallReturnPlaces, GenKill};
use rustc_index::bit_set::BitSet;
use rustc_middle::mir::visit::{PlaceContext, Visitor};
use rustc_middle::mir::{self, BasicBlock, Local, Location};
pub struct MaybeInitializedLocals;
impl<'tcx> crate::AnalysisDomain<'tcx> for MaybeInitializedLocals {
type Domain = BitSet<Local>;
const NAME: &'static str = "maybe_init_locals";
fn bottom_value(&self, body: &mir::Body<'tcx>) -> Self::Domain {
// bottom = uninit
BitSet::new_empty(body.local_decls.len())
}
fn initialize_start_block(&self, body: &mir::Body<'tcx>, entry_set: &mut Self::Domain) {
// Function arguments are initialized to begin with.
for arg in body.args_iter() {
entry_set.insert(arg);
}
}
}
impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeInitializedLocals {
type Idx = Local;
fn statement_effect(
&self,
trans: &mut impl GenKill<Self::Idx>,
statement: &mir::Statement<'tcx>,
loc: Location,
) {
TransferFunction { trans }.visit_statement(statement, loc)
}
fn terminator_effect(
&self,
trans: &mut impl GenKill<Self::Idx>,
terminator: &mir::Terminator<'tcx>,
loc: Location,
) {
TransferFunction { trans }.visit_terminator(terminator, loc)
}
fn call_return_effect(
&self,
trans: &mut impl GenKill<Self::Idx>,
_block: BasicBlock,
return_places: CallReturnPlaces<'_, 'tcx>,
) {
return_places.for_each(|place| trans.gen(place.local));
}
/// See `Analysis::apply_yield_resume_effect`.
fn yield_resume_effect(
&self,
trans: &mut impl GenKill<Self::Idx>,
_resume_block: BasicBlock,
resume_place: mir::Place<'tcx>,
) {
trans.gen(resume_place.local)
}
}
struct TransferFunction<'a, T> {
trans: &'a mut T,
}
impl<T> Visitor<'_> for TransferFunction<'_, T>
where
T: GenKill<Local>,
{
// FIXME: Using `visit_local` here is a bug. For example, on `move _5.field` we mark `_5` as
// deinitialized, although clearly it is only partially deinitialized. This analysis is not
// actually used anywhere at the moment, so this is not critical, but this does need to be fixed
// before it starts being used again.
fn visit_local(&mut self, local: Local, context: PlaceContext, _: Location) {
use rustc_middle::mir::visit::{MutatingUseContext, NonMutatingUseContext, NonUseContext};
match context {
// These are handled specially in `call_return_effect` and `yield_resume_effect`.
PlaceContext::MutatingUse(
MutatingUseContext::Call
| MutatingUseContext::AsmOutput
| MutatingUseContext::Yield,
) => {}
// If it's deinitialized, it's no longer init
PlaceContext::MutatingUse(MutatingUseContext::Deinit) => self.trans.kill(local),
// Otherwise, when a place is mutated, we must consider it possibly initialized.
PlaceContext::MutatingUse(_) => self.trans.gen(local),
// If the local is moved out of, or if it gets marked `StorageDead`, consider it no
// longer initialized.
PlaceContext::NonUse(NonUseContext::StorageDead)
| PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) => self.trans.kill(local),
// All other uses do not affect this analysis.
PlaceContext::NonUse(
NonUseContext::StorageLive
| NonUseContext::AscribeUserTy
| NonUseContext::VarDebugInfo,
)
| PlaceContext::NonMutatingUse(
NonMutatingUseContext::Inspect
| NonMutatingUseContext::Copy
| NonMutatingUseContext::SharedBorrow
| NonMutatingUseContext::ShallowBorrow
| NonMutatingUseContext::UniqueBorrow
| NonMutatingUseContext::AddressOf
| NonMutatingUseContext::Projection,
) => {}
}
}
}
|
