Struct rustc_mir_dataflow::impls::liveness::MaybeLiveLocals

pub struct MaybeLiveLocals;

A live-variable dataflow analysis.

This analysis considers references as being used only at the point of the borrow. In other words, this analysis does not track uses because of references that already exist. See this mir-dataflow test for an example. You almost never want to use this analysis without also looking at the results of MaybeBorrowedLocals.

Field-(in)sensitivity

As the name suggests, this analysis is field insensitive. If a projection of a variable x is assigned to (e.g. x.0 = 42), it does not “define” x as far as liveness is concerned. In fact, such an assignment is currently marked as a “use” of x in an attempt to be maximally conservative.

Trait Implementations

impl<'tcx> AnalysisDomain<'tcx> for MaybeLiveLocals

type Domain = ChunkedBitSet<Local>

The type that holds the dataflow state at any given point in the program.

type Direction = Backward

The direction of this analysis. Either Forward or Backward.

const NAME: &'static str = "liveness"

A descriptive name for this analysis. Used only for debugging.

fn bottom_value(&self, body: &Body<'tcx>) -> Self::Domain

Returns the initial value of the dataflow state upon entry to each basic block.

fn initialize_start_block(&self, _: &Body<'tcx>, _: &mut Self::Domain)

Mutates the initial value of the dataflow state upon entry to the START_BLOCK.

impl<'tcx> GenKillAnalysis<'tcx> for MaybeLiveLocals

type Idx = Local

fn statement_effect(
    &self,
    trans: &mut impl GenKill<Self::Idx>,
    statement: &Statement<'tcx>,
    location: Location
)

See Analysis::apply_statement_effect.

fn terminator_effect(
    &self,
    trans: &mut impl GenKill<Self::Idx>,
    terminator: &Terminator<'tcx>,
    location: Location
)

See Analysis::apply_terminator_effect.

fn call_return_effect(
    &self,
    trans: &mut impl GenKill<Self::Idx>,
    _block: BasicBlock,
    return_places: CallReturnPlaces<'_, 'tcx>
)

See Analysis::apply_call_return_effect.

fn yield_resume_effect(
    &self,
    trans: &mut impl GenKill<Self::Idx>,
    _resume_block: BasicBlock,
    resume_place: Place<'tcx>
)

See Analysis::apply_yield_resume_effect.

fn before_statement_effect(
    &self,
    _trans: &mut impl GenKill<Self::Idx>,
    _statement: &Statement<'tcx>,
    _location: Location
)

See Analysis::apply_before_statement_effect.

fn before_terminator_effect(
    &self,
    _trans: &mut impl GenKill<Self::Idx>,
    _terminator: &Terminator<'tcx>,
    _location: Location
)

See Analysis::apply_before_terminator_effect.

fn switch_int_edge_effects<G: GenKill<Self::Idx>>(
    &self,
    _block: BasicBlock,
    _discr: &Operand<'tcx>,
    _edge_effects: &mut impl SwitchIntEdgeEffects<G>
)

See Analysis::apply_switch_int_edge_effects.

impl<'tcx> RustcPeekAt<'tcx> for MaybeLiveLocals

fn peek_at(
    &self,
    tcx: TyCtxt<'tcx>,
    place: Place<'tcx>,
    flow_state: &ChunkedBitSet<Local>,
    call: PeekCall
)

Layout

Note: Most layout information is completely unstable and may even differ between compilations. The only exception is types with certain repr(...) attributes. Please see the Rust Reference’s “Type Layout” chapter for details on type layout guarantees.

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