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Diffstat (limited to 'compiler/rustc_mir_dataflow/src/impls/mod.rs')
| -rw-r--r-- | compiler/rustc_mir_dataflow/src/impls/mod.rs | 766 |
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diff --git a/compiler/rustc_mir_dataflow/src/impls/mod.rs b/compiler/rustc_mir_dataflow/src/impls/mod.rs new file mode 100644 index 000000000..fd1e49277 --- /dev/null +++ b/compiler/rustc_mir_dataflow/src/impls/mod.rs @@ -0,0 +1,766 @@ +//! Dataflow analyses are built upon some interpretation of the +//! bitvectors attached to each basic block, represented via a +//! zero-sized structure. + +use rustc_index::bit_set::{BitSet, ChunkedBitSet}; +use rustc_index::vec::Idx; +use rustc_middle::mir::visit::{MirVisitable, Visitor}; +use rustc_middle::mir::{self, Body, Location}; +use rustc_middle::ty::{self, TyCtxt}; + +use crate::drop_flag_effects_for_function_entry; +use crate::drop_flag_effects_for_location; +use crate::elaborate_drops::DropFlagState; +use crate::framework::{CallReturnPlaces, SwitchIntEdgeEffects}; +use crate::move_paths::{HasMoveData, InitIndex, InitKind, LookupResult, MoveData, MovePathIndex}; +use crate::on_lookup_result_bits; +use crate::MoveDataParamEnv; +use crate::{drop_flag_effects, on_all_children_bits}; +use crate::{lattice, AnalysisDomain, GenKill, GenKillAnalysis}; + +mod borrowed_locals; +mod init_locals; +mod liveness; +mod storage_liveness; + +pub use self::borrowed_locals::borrowed_locals; +pub use self::borrowed_locals::MaybeBorrowedLocals; +pub use self::init_locals::MaybeInitializedLocals; +pub use self::liveness::MaybeLiveLocals; +pub use self::liveness::MaybeTransitiveLiveLocals; +pub use self::storage_liveness::{MaybeRequiresStorage, MaybeStorageLive}; + +/// `MaybeInitializedPlaces` tracks all places that might be +/// initialized upon reaching a particular point in the control flow +/// for a function. +/// +/// For example, in code like the following, we have corresponding +/// dataflow information shown in the right-hand comments. +/// +/// ```rust +/// struct S; +/// fn foo(pred: bool) { // maybe-init: +/// // {} +/// let a = S; let mut b = S; let c; let d; // {a, b} +/// +/// if pred { +/// drop(a); // { b} +/// b = S; // { b} +/// +/// } else { +/// drop(b); // {a} +/// d = S; // {a, d} +/// +/// } // {a, b, d} +/// +/// c = S; // {a, b, c, d} +/// } +/// ``` +/// +/// To determine whether a place *must* be initialized at a +/// particular control-flow point, one can take the set-difference +/// between this data and the data from `MaybeUninitializedPlaces` at the +/// corresponding control-flow point. +/// +/// Similarly, at a given `drop` statement, the set-intersection +/// between this data and `MaybeUninitializedPlaces` yields the set of +/// places that would require a dynamic drop-flag at that statement. +pub struct MaybeInitializedPlaces<'a, 'tcx> { + tcx: TyCtxt<'tcx>, + body: &'a Body<'tcx>, + mdpe: &'a MoveDataParamEnv<'tcx>, +} + +impl<'a, 'tcx> MaybeInitializedPlaces<'a, 'tcx> { + pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self { + MaybeInitializedPlaces { tcx, body, mdpe } + } +} + +impl<'a, 'tcx> HasMoveData<'tcx> for MaybeInitializedPlaces<'a, 'tcx> { + fn move_data(&self) -> &MoveData<'tcx> { + &self.mdpe.move_data + } +} + +/// `MaybeUninitializedPlaces` tracks all places that might be +/// uninitialized upon reaching a particular point in the control flow +/// for a function. +/// +/// For example, in code like the following, we have corresponding +/// dataflow information shown in the right-hand comments. +/// +/// ```rust +/// struct S; +/// fn foo(pred: bool) { // maybe-uninit: +/// // {a, b, c, d} +/// let a = S; let mut b = S; let c; let d; // { c, d} +/// +/// if pred { +/// drop(a); // {a, c, d} +/// b = S; // {a, c, d} +/// +/// } else { +/// drop(b); // { b, c, d} +/// d = S; // { b, c } +/// +/// } // {a, b, c, d} +/// +/// c = S; // {a, b, d} +/// } +/// ``` +/// +/// To determine whether a place *must* be uninitialized at a +/// particular control-flow point, one can take the set-difference +/// between this data and the data from `MaybeInitializedPlaces` at the +/// corresponding control-flow point. +/// +/// Similarly, at a given `drop` statement, the set-intersection +/// between this data and `MaybeInitializedPlaces` yields the set of +/// places that would require a dynamic drop-flag at that statement. +pub struct MaybeUninitializedPlaces<'a, 'tcx> { + tcx: TyCtxt<'tcx>, + body: &'a Body<'tcx>, + mdpe: &'a MoveDataParamEnv<'tcx>, + + mark_inactive_variants_as_uninit: bool, +} + +impl<'a, 'tcx> MaybeUninitializedPlaces<'a, 'tcx> { + pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self { + MaybeUninitializedPlaces { tcx, body, mdpe, mark_inactive_variants_as_uninit: false } + } + + /// Causes inactive enum variants to be marked as "maybe uninitialized" after a switch on an + /// enum discriminant. + /// + /// This is correct in a vacuum but is not the default because it causes problems in the borrow + /// checker, where this information gets propagated along `FakeEdge`s. + pub fn mark_inactive_variants_as_uninit(mut self) -> Self { + self.mark_inactive_variants_as_uninit = true; + self + } +} + +impl<'a, 'tcx> HasMoveData<'tcx> for MaybeUninitializedPlaces<'a, 'tcx> { + fn move_data(&self) -> &MoveData<'tcx> { + &self.mdpe.move_data + } +} + +/// `DefinitelyInitializedPlaces` tracks all places that are definitely +/// initialized upon reaching a particular point in the control flow +/// for a function. +/// +/// For example, in code like the following, we have corresponding +/// dataflow information shown in the right-hand comments. +/// +/// ```rust +/// struct S; +/// fn foo(pred: bool) { // definite-init: +/// // { } +/// let a = S; let mut b = S; let c; let d; // {a, b } +/// +/// if pred { +/// drop(a); // { b, } +/// b = S; // { b, } +/// +/// } else { +/// drop(b); // {a, } +/// d = S; // {a, d} +/// +/// } // { } +/// +/// c = S; // { c } +/// } +/// ``` +/// +/// To determine whether a place *may* be uninitialized at a +/// particular control-flow point, one can take the set-complement +/// of this data. +/// +/// Similarly, at a given `drop` statement, the set-difference between +/// this data and `MaybeInitializedPlaces` yields the set of places +/// that would require a dynamic drop-flag at that statement. +pub struct DefinitelyInitializedPlaces<'a, 'tcx> { + tcx: TyCtxt<'tcx>, + body: &'a Body<'tcx>, + mdpe: &'a MoveDataParamEnv<'tcx>, +} + +impl<'a, 'tcx> DefinitelyInitializedPlaces<'a, 'tcx> { + pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self { + DefinitelyInitializedPlaces { tcx, body, mdpe } + } +} + +impl<'a, 'tcx> HasMoveData<'tcx> for DefinitelyInitializedPlaces<'a, 'tcx> { + fn move_data(&self) -> &MoveData<'tcx> { + &self.mdpe.move_data + } +} + +/// `EverInitializedPlaces` tracks all places that might have ever been +/// initialized upon reaching a particular point in the control flow +/// for a function, without an intervening `StorageDead`. +/// +/// This dataflow is used to determine if an immutable local variable may +/// be assigned to. +/// +/// For example, in code like the following, we have corresponding +/// dataflow information shown in the right-hand comments. +/// +/// ```rust +/// struct S; +/// fn foo(pred: bool) { // ever-init: +/// // { } +/// let a = S; let mut b = S; let c; let d; // {a, b } +/// +/// if pred { +/// drop(a); // {a, b, } +/// b = S; // {a, b, } +/// +/// } else { +/// drop(b); // {a, b, } +/// d = S; // {a, b, d } +/// +/// } // {a, b, d } +/// +/// c = S; // {a, b, c, d } +/// } +/// ``` +pub struct EverInitializedPlaces<'a, 'tcx> { + #[allow(dead_code)] + tcx: TyCtxt<'tcx>, + body: &'a Body<'tcx>, + mdpe: &'a MoveDataParamEnv<'tcx>, +} + +impl<'a, 'tcx> EverInitializedPlaces<'a, 'tcx> { + pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self { + EverInitializedPlaces { tcx, body, mdpe } + } +} + +impl<'a, 'tcx> HasMoveData<'tcx> for EverInitializedPlaces<'a, 'tcx> { + fn move_data(&self) -> &MoveData<'tcx> { + &self.mdpe.move_data + } +} + +impl<'a, 'tcx> MaybeInitializedPlaces<'a, 'tcx> { + fn update_bits( + trans: &mut impl GenKill<MovePathIndex>, + path: MovePathIndex, + state: DropFlagState, + ) { + match state { + DropFlagState::Absent => trans.kill(path), + DropFlagState::Present => trans.gen(path), + } + } +} + +impl<'a, 'tcx> MaybeUninitializedPlaces<'a, 'tcx> { + fn update_bits( + trans: &mut impl GenKill<MovePathIndex>, + path: MovePathIndex, + state: DropFlagState, + ) { + match state { + DropFlagState::Absent => trans.gen(path), + DropFlagState::Present => trans.kill(path), + } + } +} + +impl<'a, 'tcx> DefinitelyInitializedPlaces<'a, 'tcx> { + fn update_bits( + trans: &mut impl GenKill<MovePathIndex>, + path: MovePathIndex, + state: DropFlagState, + ) { + match state { + DropFlagState::Absent => trans.kill(path), + DropFlagState::Present => trans.gen(path), + } + } +} + +impl<'tcx> AnalysisDomain<'tcx> for MaybeInitializedPlaces<'_, 'tcx> { + type Domain = ChunkedBitSet<MovePathIndex>; + const NAME: &'static str = "maybe_init"; + + fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain { + // bottom = uninitialized + ChunkedBitSet::new_empty(self.move_data().move_paths.len()) + } + + fn initialize_start_block(&self, _: &mir::Body<'tcx>, state: &mut Self::Domain) { + drop_flag_effects_for_function_entry(self.tcx, self.body, self.mdpe, |path, s| { + assert!(s == DropFlagState::Present); + state.insert(path); + }); + } +} + +impl<'tcx> GenKillAnalysis<'tcx> for MaybeInitializedPlaces<'_, 'tcx> { + type Idx = MovePathIndex; + + fn statement_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + statement: &mir::Statement<'tcx>, + location: Location, + ) { + drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| { + Self::update_bits(trans, path, s) + }); + + if !self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration { + return; + } + + // Mark all places as "maybe init" if they are mutably borrowed. See #90752. + for_each_mut_borrow(statement, location, |place| { + let LookupResult::Exact(mpi) = self.move_data().rev_lookup.find(place.as_ref()) else { return }; + on_all_children_bits(self.tcx, self.body, self.move_data(), mpi, |child| { + trans.gen(child); + }) + }) + } + + fn terminator_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + terminator: &mir::Terminator<'tcx>, + location: Location, + ) { + drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| { + Self::update_bits(trans, path, s) + }); + + if !self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration { + return; + } + + for_each_mut_borrow(terminator, location, |place| { + let LookupResult::Exact(mpi) = self.move_data().rev_lookup.find(place.as_ref()) else { return }; + on_all_children_bits(self.tcx, self.body, self.move_data(), mpi, |child| { + trans.gen(child); + }) + }) + } + + fn call_return_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + _block: mir::BasicBlock, + return_places: CallReturnPlaces<'_, 'tcx>, + ) { + return_places.for_each(|place| { + // when a call returns successfully, that means we need to set + // the bits for that dest_place to 1 (initialized). + on_lookup_result_bits( + self.tcx, + self.body, + self.move_data(), + self.move_data().rev_lookup.find(place.as_ref()), + |mpi| { + trans.gen(mpi); + }, + ); + }); + } + + fn switch_int_edge_effects<G: GenKill<Self::Idx>>( + &self, + block: mir::BasicBlock, + discr: &mir::Operand<'tcx>, + edge_effects: &mut impl SwitchIntEdgeEffects<G>, + ) { + if !self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration { + return; + } + + let enum_ = discr.place().and_then(|discr| { + switch_on_enum_discriminant(self.tcx, &self.body, &self.body[block], discr) + }); + + let Some((enum_place, enum_def)) = enum_ else { + return; + }; + + let mut discriminants = enum_def.discriminants(self.tcx); + edge_effects.apply(|trans, edge| { + let Some(value) = edge.value else { + return; + }; + + // MIR building adds discriminants to the `values` array in the same order as they + // are yielded by `AdtDef::discriminants`. We rely on this to match each + // discriminant in `values` to its corresponding variant in linear time. + let (variant, _) = discriminants + .find(|&(_, discr)| discr.val == value) + .expect("Order of `AdtDef::discriminants` differed from `SwitchInt::values`"); + + // Kill all move paths that correspond to variants we know to be inactive along this + // particular outgoing edge of a `SwitchInt`. + drop_flag_effects::on_all_inactive_variants( + self.tcx, + self.body, + self.move_data(), + enum_place, + variant, + |mpi| trans.kill(mpi), + ); + }); + } +} + +impl<'tcx> AnalysisDomain<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> { + type Domain = ChunkedBitSet<MovePathIndex>; + + const NAME: &'static str = "maybe_uninit"; + + fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain { + // bottom = initialized (start_block_effect counters this at outset) + ChunkedBitSet::new_empty(self.move_data().move_paths.len()) + } + + // sets on_entry bits for Arg places + fn initialize_start_block(&self, _: &mir::Body<'tcx>, state: &mut Self::Domain) { + // set all bits to 1 (uninit) before gathering counter-evidence + state.insert_all(); + + drop_flag_effects_for_function_entry(self.tcx, self.body, self.mdpe, |path, s| { + assert!(s == DropFlagState::Present); + state.remove(path); + }); + } +} + +impl<'tcx> GenKillAnalysis<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> { + type Idx = MovePathIndex; + + fn statement_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + _statement: &mir::Statement<'tcx>, + location: Location, + ) { + drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| { + Self::update_bits(trans, path, s) + }); + + // Unlike in `MaybeInitializedPlaces` above, we don't need to change the state when a + // mutable borrow occurs. Places cannot become uninitialized through a mutable reference. + } + + fn terminator_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + _terminator: &mir::Terminator<'tcx>, + location: Location, + ) { + drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| { + Self::update_bits(trans, path, s) + }); + } + + fn call_return_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + _block: mir::BasicBlock, + return_places: CallReturnPlaces<'_, 'tcx>, + ) { + return_places.for_each(|place| { + // when a call returns successfully, that means we need to set + // the bits for that dest_place to 0 (initialized). + on_lookup_result_bits( + self.tcx, + self.body, + self.move_data(), + self.move_data().rev_lookup.find(place.as_ref()), + |mpi| { + trans.kill(mpi); + }, + ); + }); + } + + fn switch_int_edge_effects<G: GenKill<Self::Idx>>( + &self, + block: mir::BasicBlock, + discr: &mir::Operand<'tcx>, + edge_effects: &mut impl SwitchIntEdgeEffects<G>, + ) { + if !self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration { + return; + } + + if !self.mark_inactive_variants_as_uninit { + return; + } + + let enum_ = discr.place().and_then(|discr| { + switch_on_enum_discriminant(self.tcx, &self.body, &self.body[block], discr) + }); + + let Some((enum_place, enum_def)) = enum_ else { + return; + }; + + let mut discriminants = enum_def.discriminants(self.tcx); + edge_effects.apply(|trans, edge| { + let Some(value) = edge.value else { + return; + }; + + // MIR building adds discriminants to the `values` array in the same order as they + // are yielded by `AdtDef::discriminants`. We rely on this to match each + // discriminant in `values` to its corresponding variant in linear time. + let (variant, _) = discriminants + .find(|&(_, discr)| discr.val == value) + .expect("Order of `AdtDef::discriminants` differed from `SwitchInt::values`"); + + // Mark all move paths that correspond to variants other than this one as maybe + // uninitialized (in reality, they are *definitely* uninitialized). + drop_flag_effects::on_all_inactive_variants( + self.tcx, + self.body, + self.move_data(), + enum_place, + variant, + |mpi| trans.gen(mpi), + ); + }); + } +} + +impl<'a, 'tcx> AnalysisDomain<'tcx> for DefinitelyInitializedPlaces<'a, 'tcx> { + /// Use set intersection as the join operator. + type Domain = lattice::Dual<BitSet<MovePathIndex>>; + + const NAME: &'static str = "definite_init"; + + fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain { + // bottom = initialized (start_block_effect counters this at outset) + lattice::Dual(BitSet::new_filled(self.move_data().move_paths.len())) + } + + // sets on_entry bits for Arg places + fn initialize_start_block(&self, _: &mir::Body<'tcx>, state: &mut Self::Domain) { + state.0.clear(); + + drop_flag_effects_for_function_entry(self.tcx, self.body, self.mdpe, |path, s| { + assert!(s == DropFlagState::Present); + state.0.insert(path); + }); + } +} + +impl<'tcx> GenKillAnalysis<'tcx> for DefinitelyInitializedPlaces<'_, 'tcx> { + type Idx = MovePathIndex; + + fn statement_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + _statement: &mir::Statement<'tcx>, + location: Location, + ) { + drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| { + Self::update_bits(trans, path, s) + }) + } + + fn terminator_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + _terminator: &mir::Terminator<'tcx>, + location: Location, + ) { + drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| { + Self::update_bits(trans, path, s) + }) + } + + fn call_return_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + _block: mir::BasicBlock, + return_places: CallReturnPlaces<'_, 'tcx>, + ) { + return_places.for_each(|place| { + // when a call returns successfully, that means we need to set + // the bits for that dest_place to 1 (initialized). + on_lookup_result_bits( + self.tcx, + self.body, + self.move_data(), + self.move_data().rev_lookup.find(place.as_ref()), + |mpi| { + trans.gen(mpi); + }, + ); + }); + } +} + +impl<'tcx> AnalysisDomain<'tcx> for EverInitializedPlaces<'_, 'tcx> { + type Domain = ChunkedBitSet<InitIndex>; + + const NAME: &'static str = "ever_init"; + + fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain { + // bottom = no initialized variables by default + ChunkedBitSet::new_empty(self.move_data().inits.len()) + } + + fn initialize_start_block(&self, body: &mir::Body<'tcx>, state: &mut Self::Domain) { + for arg_init in 0..body.arg_count { + state.insert(InitIndex::new(arg_init)); + } + } +} + +impl<'tcx> GenKillAnalysis<'tcx> for EverInitializedPlaces<'_, 'tcx> { + type Idx = InitIndex; + + #[instrument(skip(self, trans), level = "debug")] + fn statement_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + stmt: &mir::Statement<'tcx>, + location: Location, + ) { + let move_data = self.move_data(); + let init_path_map = &move_data.init_path_map; + let init_loc_map = &move_data.init_loc_map; + let rev_lookup = &move_data.rev_lookup; + + debug!("initializes move_indexes {:?}", &init_loc_map[location]); + trans.gen_all(init_loc_map[location].iter().copied()); + + if let mir::StatementKind::StorageDead(local) = stmt.kind { + // End inits for StorageDead, so that an immutable variable can + // be reinitialized on the next iteration of the loop. + let move_path_index = rev_lookup.find_local(local); + debug!("clears the ever initialized status of {:?}", init_path_map[move_path_index]); + trans.kill_all(init_path_map[move_path_index].iter().copied()); + } + } + + #[instrument(skip(self, trans, _terminator), level = "debug")] + fn terminator_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + _terminator: &mir::Terminator<'tcx>, + location: Location, + ) { + let (body, move_data) = (self.body, self.move_data()); + let term = body[location.block].terminator(); + let init_loc_map = &move_data.init_loc_map; + debug!(?term); + debug!("initializes move_indexes {:?}", init_loc_map[location]); + trans.gen_all( + init_loc_map[location] + .iter() + .filter(|init_index| { + move_data.inits[**init_index].kind != InitKind::NonPanicPathOnly + }) + .copied(), + ); + } + + fn call_return_effect( + &self, + trans: &mut impl GenKill<Self::Idx>, + block: mir::BasicBlock, + _return_places: CallReturnPlaces<'_, 'tcx>, + ) { + let move_data = self.move_data(); + let init_loc_map = &move_data.init_loc_map; + + let call_loc = self.body.terminator_loc(block); + for init_index in &init_loc_map[call_loc] { + trans.gen(*init_index); + } + } +} + +/// Inspect a `SwitchInt`-terminated basic block to see if the condition of that `SwitchInt` is +/// an enum discriminant. +/// +/// We expect such blocks to have a call to `discriminant` as their last statement like so: +/// +/// ```text +/// ... +/// _42 = discriminant(_1) +/// SwitchInt(_42, ..) +/// ``` +/// +/// If the basic block matches this pattern, this function returns the place corresponding to the +/// enum (`_1` in the example above) as well as the `AdtDef` of that enum. +fn switch_on_enum_discriminant<'mir, 'tcx>( + tcx: TyCtxt<'tcx>, + body: &'mir mir::Body<'tcx>, + block: &'mir mir::BasicBlockData<'tcx>, + switch_on: mir::Place<'tcx>, +) -> Option<(mir::Place<'tcx>, ty::AdtDef<'tcx>)> { + for statement in block.statements.iter().rev() { + match &statement.kind { + mir::StatementKind::Assign(box (lhs, mir::Rvalue::Discriminant(discriminated))) + if *lhs == switch_on => + { + match discriminated.ty(body, tcx).ty.kind() { + ty::Adt(def, _) => return Some((*discriminated, *def)), + + // `Rvalue::Discriminant` is also used to get the active yield point for a + // generator, but we do not need edge-specific effects in that case. This may + // change in the future. + ty::Generator(..) => return None, + + t => bug!("`discriminant` called on unexpected type {:?}", t), + } + } + mir::StatementKind::Coverage(_) => continue, + _ => return None, + } + } + None +} + +struct OnMutBorrow<F>(F); + +impl<F> Visitor<'_> for OnMutBorrow<F> +where + F: FnMut(&mir::Place<'_>), +{ + fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'_>, location: Location) { + // FIXME: Does `&raw const foo` allow mutation? See #90413. + match rvalue { + mir::Rvalue::Ref(_, mir::BorrowKind::Mut { .. }, place) + | mir::Rvalue::AddressOf(_, place) => (self.0)(place), + + _ => {} + } + + self.super_rvalue(rvalue, location) + } +} + +/// Calls `f` for each mutable borrow or raw reference in the program. +/// +/// This DOES NOT call `f` for a shared borrow of a type with interior mutability. That's okay for +/// initializedness, because we cannot move from an `UnsafeCell` (outside of `core::cell`), but +/// other analyses will likely need to check for `!Freeze`. +fn for_each_mut_borrow<'tcx>( + mir: &impl MirVisitable<'tcx>, + location: Location, + f: impl FnMut(&mir::Place<'_>), +) { + let mut vis = OnMutBorrow(f); + + mir.apply(location, &mut vis); +} |