| use crate::borrow_check::borrow_set::{BorrowSet, BorrowData}; |
| use crate::borrow_check::place_ext::PlaceExt; |
| |
| use rustc::mir::{self, Location, Place, PlaceBase, Body}; |
| use rustc::ty::{self, TyCtxt}; |
| use rustc::ty::RegionVid; |
| |
| use rustc_data_structures::bit_set::BitSet; |
| use rustc_data_structures::fx::FxHashMap; |
| use rustc_data_structures::indexed_vec::{Idx, IndexVec}; |
| |
| use crate::dataflow::{BitDenotation, BottomValue, GenKillSet}; |
| use crate::borrow_check::nll::region_infer::RegionInferenceContext; |
| use crate::borrow_check::nll::ToRegionVid; |
| use crate::borrow_check::places_conflict; |
| |
| use std::rc::Rc; |
| |
| newtype_index! { |
| pub struct BorrowIndex { |
| DEBUG_FORMAT = "bw{}" |
| } |
| } |
| |
| /// `Borrows` stores the data used in the analyses that track the flow |
| /// of borrows. |
| /// |
| /// It uniquely identifies every borrow (`Rvalue::Ref`) by a |
| /// `BorrowIndex`, and maps each such index to a `BorrowData` |
| /// describing the borrow. These indexes are used for representing the |
| /// borrows in compact bitvectors. |
| pub struct Borrows<'a, 'tcx> { |
| tcx: TyCtxt<'tcx>, |
| body: &'a Body<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| |
| borrow_set: Rc<BorrowSet<'tcx>>, |
| borrows_out_of_scope_at_location: FxHashMap<Location, Vec<BorrowIndex>>, |
| |
| /// NLL region inference context with which NLL queries should be resolved |
| _nonlexical_regioncx: Rc<RegionInferenceContext<'tcx>>, |
| } |
| |
| struct StackEntry { |
| bb: mir::BasicBlock, |
| lo: usize, |
| hi: usize, |
| first_part_only: bool |
| } |
| |
| fn precompute_borrows_out_of_scope<'tcx>( |
| body: &Body<'tcx>, |
| regioncx: &Rc<RegionInferenceContext<'tcx>>, |
| borrows_out_of_scope_at_location: &mut FxHashMap<Location, Vec<BorrowIndex>>, |
| borrow_index: BorrowIndex, |
| borrow_region: RegionVid, |
| location: Location, |
| ) { |
| // We visit one BB at a time. The complication is that we may start in the |
| // middle of the first BB visited (the one containing `location`), in which |
| // case we may have to later on process the first part of that BB if there |
| // is a path back to its start. |
| |
| // For visited BBs, we record the index of the first statement processed. |
| // (In fully processed BBs this index is 0.) Note also that we add BBs to |
| // `visited` once they are added to `stack`, before they are actually |
| // processed, because this avoids the need to look them up again on |
| // completion. |
| let mut visited = FxHashMap::default(); |
| visited.insert(location.block, location.statement_index); |
| |
| let mut stack = vec![]; |
| stack.push(StackEntry { |
| bb: location.block, |
| lo: location.statement_index, |
| hi: body[location.block].statements.len(), |
| first_part_only: false, |
| }); |
| |
| while let Some(StackEntry { bb, lo, hi, first_part_only }) = stack.pop() { |
| let mut finished_early = first_part_only; |
| for i in lo ..= hi { |
| let location = Location { block: bb, statement_index: i }; |
| // If region does not contain a point at the location, then add to list and skip |
| // successor locations. |
| if !regioncx.region_contains(borrow_region, location) { |
| debug!("borrow {:?} gets killed at {:?}", borrow_index, location); |
| borrows_out_of_scope_at_location |
| .entry(location) |
| .or_default() |
| .push(borrow_index); |
| finished_early = true; |
| break; |
| } |
| } |
| |
| if !finished_early { |
| // Add successor BBs to the work list, if necessary. |
| let bb_data = &body[bb]; |
| assert!(hi == bb_data.statements.len()); |
| for &succ_bb in bb_data.terminator.as_ref().unwrap().successors() { |
| visited.entry(succ_bb) |
| .and_modify(|lo| { |
| // `succ_bb` has been seen before. If it wasn't |
| // fully processed, add its first part to `stack` |
| // for processing. |
| if *lo > 0 { |
| stack.push(StackEntry { |
| bb: succ_bb, |
| lo: 0, |
| hi: *lo - 1, |
| first_part_only: true, |
| }); |
| } |
| // And update this entry with 0, to represent the |
| // whole BB being processed. |
| *lo = 0; |
| }) |
| .or_insert_with(|| { |
| // succ_bb hasn't been seen before. Add it to |
| // `stack` for processing. |
| stack.push(StackEntry { |
| bb: succ_bb, |
| lo: 0, |
| hi: body[succ_bb].statements.len(), |
| first_part_only: false, |
| }); |
| // Insert 0 for this BB, to represent the whole BB |
| // being processed. |
| 0 |
| }); |
| } |
| } |
| } |
| } |
| |
| impl<'a, 'tcx> Borrows<'a, 'tcx> { |
| crate fn new( |
| tcx: TyCtxt<'tcx>, |
| body: &'a Body<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| nonlexical_regioncx: Rc<RegionInferenceContext<'tcx>>, |
| borrow_set: &Rc<BorrowSet<'tcx>>, |
| ) -> Self { |
| let mut borrows_out_of_scope_at_location = FxHashMap::default(); |
| for (borrow_index, borrow_data) in borrow_set.borrows.iter_enumerated() { |
| let borrow_region = borrow_data.region.to_region_vid(); |
| let location = borrow_set.borrows[borrow_index].reserve_location; |
| |
| precompute_borrows_out_of_scope(body, &nonlexical_regioncx, |
| &mut borrows_out_of_scope_at_location, |
| borrow_index, borrow_region, location); |
| } |
| |
| Borrows { |
| tcx: tcx, |
| body: body, |
| param_env, |
| borrow_set: borrow_set.clone(), |
| borrows_out_of_scope_at_location, |
| _nonlexical_regioncx: nonlexical_regioncx, |
| } |
| } |
| |
| crate fn borrows(&self) -> &IndexVec<BorrowIndex, BorrowData<'tcx>> { &self.borrow_set.borrows } |
| |
| pub fn location(&self, idx: BorrowIndex) -> &Location { |
| &self.borrow_set.borrows[idx].reserve_location |
| } |
| |
| /// Add all borrows to the kill set, if those borrows are out of scope at `location`. |
| /// That means they went out of a nonlexical scope |
| fn kill_loans_out_of_scope_at_location(&self, |
| trans: &mut GenKillSet<BorrowIndex>, |
| location: Location) { |
| // NOTE: The state associated with a given `location` |
| // reflects the dataflow on entry to the statement. |
| // Iterate over each of the borrows that we've precomputed |
| // to have went out of scope at this location and kill them. |
| // |
| // We are careful always to call this function *before* we |
| // set up the gen-bits for the statement or |
| // termanator. That way, if the effect of the statement or |
| // terminator *does* introduce a new loan of the same |
| // region, then setting that gen-bit will override any |
| // potential kill introduced here. |
| if let Some(indices) = self.borrows_out_of_scope_at_location.get(&location) { |
| trans.kill_all(indices); |
| } |
| } |
| |
| /// Kill any borrows that conflict with `place`. |
| fn kill_borrows_on_place( |
| &self, |
| trans: &mut GenKillSet<BorrowIndex>, |
| place: &Place<'tcx> |
| ) { |
| debug!("kill_borrows_on_place: place={:?}", place); |
| |
| if let PlaceBase::Local(local) = place.base { |
| let other_borrows_of_local = self |
| .borrow_set |
| .local_map |
| .get(&local) |
| .into_iter() |
| .flat_map(|bs| bs.into_iter()); |
| |
| // If the borrowed place is a local with no projections, all other borrows of this |
| // local must conflict. This is purely an optimization so we don't have to call |
| // `places_conflict` for every borrow. |
| if place.projection.is_empty() { |
| trans.kill_all(other_borrows_of_local); |
| return; |
| } |
| |
| // By passing `PlaceConflictBias::NoOverlap`, we conservatively assume that any given |
| // pair of array indices are unequal, so that when `places_conflict` returns true, we |
| // will be assured that two places being compared definitely denotes the same sets of |
| // locations. |
| let definitely_conflicting_borrows = other_borrows_of_local |
| .filter(|&&i| { |
| places_conflict::places_conflict( |
| self.tcx, |
| self.param_env, |
| self.body, |
| &self.borrow_set.borrows[i].borrowed_place, |
| place, |
| places_conflict::PlaceConflictBias::NoOverlap) |
| }); |
| |
| trans.kill_all(definitely_conflicting_borrows); |
| } |
| } |
| } |
| |
| impl<'a, 'tcx> BitDenotation<'tcx> for Borrows<'a, 'tcx> { |
| type Idx = BorrowIndex; |
| fn name() -> &'static str { "borrows" } |
| fn bits_per_block(&self) -> usize { |
| self.borrow_set.borrows.len() * 2 |
| } |
| |
| fn start_block_effect(&self, _entry_set: &mut BitSet<Self::Idx>) { |
| // no borrows of code region_scopes have been taken prior to |
| // function execution, so this method has no effect. |
| } |
| |
| fn before_statement_effect(&self, |
| trans: &mut GenKillSet<Self::Idx>, |
| location: Location) { |
| debug!("Borrows::before_statement_effect trans: {:?} location: {:?}", |
| trans, location); |
| self.kill_loans_out_of_scope_at_location(trans, location); |
| } |
| |
| fn statement_effect(&self, |
| trans: &mut GenKillSet<Self::Idx>, |
| location: Location) { |
| debug!("Borrows::statement_effect: trans={:?} location={:?}", |
| trans, location); |
| |
| let block = &self.body.basic_blocks().get(location.block).unwrap_or_else(|| { |
| panic!("could not find block at location {:?}", location); |
| }); |
| let stmt = block.statements.get(location.statement_index).unwrap_or_else(|| { |
| panic!("could not find statement at location {:?}"); |
| }); |
| |
| debug!("Borrows::statement_effect: stmt={:?}", stmt); |
| match stmt.kind { |
| mir::StatementKind::Assign(box(ref lhs, ref rhs)) => { |
| if let mir::Rvalue::Ref(_, _, ref place) = *rhs { |
| if place.ignore_borrow( |
| self.tcx, |
| self.body, |
| &self.borrow_set.locals_state_at_exit, |
| ) { |
| return; |
| } |
| let index = self.borrow_set.location_map.get(&location).unwrap_or_else(|| { |
| panic!("could not find BorrowIndex for location {:?}", location); |
| }); |
| |
| trans.gen(*index); |
| } |
| |
| // Make sure there are no remaining borrows for variables |
| // that are assigned over. |
| self.kill_borrows_on_place(trans, lhs); |
| } |
| |
| mir::StatementKind::StorageDead(local) => { |
| // Make sure there are no remaining borrows for locals that |
| // are gone out of scope. |
| self.kill_borrows_on_place(trans, &Place::from(local)); |
| } |
| |
| mir::StatementKind::InlineAsm(ref asm) => { |
| for (output, kind) in asm.outputs.iter().zip(&asm.asm.outputs) { |
| if !kind.is_indirect && !kind.is_rw { |
| self.kill_borrows_on_place(trans, output); |
| } |
| } |
| } |
| |
| mir::StatementKind::FakeRead(..) | |
| mir::StatementKind::SetDiscriminant { .. } | |
| mir::StatementKind::StorageLive(..) | |
| mir::StatementKind::Retag { .. } | |
| mir::StatementKind::AscribeUserType(..) | |
| mir::StatementKind::Nop => {} |
| |
| } |
| } |
| |
| fn before_terminator_effect(&self, |
| trans: &mut GenKillSet<Self::Idx>, |
| location: Location) { |
| debug!("Borrows::before_terminator_effect: trans={:?} location={:?}", |
| trans, location); |
| self.kill_loans_out_of_scope_at_location(trans, location); |
| } |
| |
| fn terminator_effect(&self, |
| _: &mut GenKillSet<Self::Idx>, |
| _: Location) {} |
| |
| fn propagate_call_return( |
| &self, |
| _in_out: &mut BitSet<BorrowIndex>, |
| _call_bb: mir::BasicBlock, |
| _dest_bb: mir::BasicBlock, |
| _dest_place: &mir::Place<'tcx>, |
| ) { |
| } |
| } |
| |
| impl<'a, 'tcx> BottomValue for Borrows<'a, 'tcx> { |
| /// bottom = nothing is reserved or activated yet; |
| const BOTTOM_VALUE: bool = false; |
| } |
