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Diffstat (limited to 'compiler/rustc_borrowck/src/invalidation.rs')
| -rw-r--r-- | compiler/rustc_borrowck/src/invalidation.rs | 442 |
1 files changed, 442 insertions, 0 deletions
diff --git a/compiler/rustc_borrowck/src/invalidation.rs b/compiler/rustc_borrowck/src/invalidation.rs new file mode 100644 index 000000000..ec521b1cf --- /dev/null +++ b/compiler/rustc_borrowck/src/invalidation.rs @@ -0,0 +1,442 @@ +use rustc_data_structures::graph::dominators::Dominators; +use rustc_middle::mir::visit::Visitor; +use rustc_middle::mir::{BasicBlock, Body, Location, Place, Rvalue}; +use rustc_middle::mir::{BorrowKind, Mutability, Operand}; +use rustc_middle::mir::{InlineAsmOperand, Terminator, TerminatorKind}; +use rustc_middle::mir::{Statement, StatementKind}; +use rustc_middle::ty::TyCtxt; + +use crate::{ + borrow_set::BorrowSet, facts::AllFacts, location::LocationTable, path_utils::*, AccessDepth, + Activation, ArtificialField, BorrowIndex, Deep, LocalMutationIsAllowed, Read, ReadKind, + ReadOrWrite, Reservation, Shallow, Write, WriteKind, +}; + +pub(super) fn generate_invalidates<'tcx>( + tcx: TyCtxt<'tcx>, + all_facts: &mut Option<AllFacts>, + location_table: &LocationTable, + body: &Body<'tcx>, + borrow_set: &BorrowSet<'tcx>, +) { + if all_facts.is_none() { + // Nothing to do if we don't have any facts + return; + } + + if let Some(all_facts) = all_facts { + let _prof_timer = tcx.prof.generic_activity("polonius_fact_generation"); + let dominators = body.basic_blocks.dominators(); + let mut ig = InvalidationGenerator { + all_facts, + borrow_set, + tcx, + location_table, + body: &body, + dominators, + }; + ig.visit_body(body); + } +} + +struct InvalidationGenerator<'cx, 'tcx> { + tcx: TyCtxt<'tcx>, + all_facts: &'cx mut AllFacts, + location_table: &'cx LocationTable, + body: &'cx Body<'tcx>, + dominators: Dominators<BasicBlock>, + borrow_set: &'cx BorrowSet<'tcx>, +} + +/// Visits the whole MIR and generates `invalidates()` facts. +/// Most of the code implementing this was stolen from `borrow_check/mod.rs`. +impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> { + fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) { + self.check_activations(location); + + match &statement.kind { + StatementKind::Assign(box (lhs, rhs)) => { + self.consume_rvalue(location, rhs); + + self.mutate_place(location, *lhs, Shallow(None)); + } + StatementKind::FakeRead(box (_, _)) => { + // Only relevant for initialized/liveness/safety checks. + } + StatementKind::CopyNonOverlapping(box rustc_middle::mir::CopyNonOverlapping { + ref src, + ref dst, + ref count, + }) => { + self.consume_operand(location, src); + self.consume_operand(location, dst); + self.consume_operand(location, count); + } + StatementKind::Nop + | StatementKind::Coverage(..) + | StatementKind::AscribeUserType(..) + | StatementKind::Retag { .. } + | StatementKind::StorageLive(..) => { + // `Nop`, `AscribeUserType`, `Retag`, and `StorageLive` are irrelevant + // to borrow check. + } + StatementKind::StorageDead(local) => { + self.access_place( + location, + Place::from(*local), + (Shallow(None), Write(WriteKind::StorageDeadOrDrop)), + LocalMutationIsAllowed::Yes, + ); + } + StatementKind::Deinit(..) | StatementKind::SetDiscriminant { .. } => { + bug!("Statement not allowed in this MIR phase") + } + } + + self.super_statement(statement, location); + } + + fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) { + self.check_activations(location); + + match &terminator.kind { + TerminatorKind::SwitchInt { ref discr, switch_ty: _, targets: _ } => { + self.consume_operand(location, discr); + } + TerminatorKind::Drop { place: drop_place, target: _, unwind: _ } => { + self.access_place( + location, + *drop_place, + (AccessDepth::Drop, Write(WriteKind::StorageDeadOrDrop)), + LocalMutationIsAllowed::Yes, + ); + } + TerminatorKind::DropAndReplace { + place: drop_place, + value: ref new_value, + target: _, + unwind: _, + } => { + self.mutate_place(location, *drop_place, Deep); + self.consume_operand(location, new_value); + } + TerminatorKind::Call { + ref func, + ref args, + destination, + target: _, + cleanup: _, + from_hir_call: _, + fn_span: _, + } => { + self.consume_operand(location, func); + for arg in args { + self.consume_operand(location, arg); + } + self.mutate_place(location, *destination, Deep); + } + TerminatorKind::Assert { ref cond, expected: _, ref msg, target: _, cleanup: _ } => { + self.consume_operand(location, cond); + use rustc_middle::mir::AssertKind; + if let AssertKind::BoundsCheck { ref len, ref index } = *msg { + self.consume_operand(location, len); + self.consume_operand(location, index); + } + } + TerminatorKind::Yield { ref value, resume, resume_arg, drop: _ } => { + self.consume_operand(location, value); + + // Invalidate all borrows of local places + let borrow_set = self.borrow_set; + let resume = self.location_table.start_index(resume.start_location()); + for (i, data) in borrow_set.iter_enumerated() { + if borrow_of_local_data(data.borrowed_place) { + self.all_facts.loan_invalidated_at.push((resume, i)); + } + } + + self.mutate_place(location, *resume_arg, Deep); + } + TerminatorKind::Resume | TerminatorKind::Return | TerminatorKind::GeneratorDrop => { + // Invalidate all borrows of local places + let borrow_set = self.borrow_set; + let start = self.location_table.start_index(location); + for (i, data) in borrow_set.iter_enumerated() { + if borrow_of_local_data(data.borrowed_place) { + self.all_facts.loan_invalidated_at.push((start, i)); + } + } + } + TerminatorKind::InlineAsm { + template: _, + ref operands, + options: _, + line_spans: _, + destination: _, + cleanup: _, + } => { + for op in operands { + match *op { + InlineAsmOperand::In { reg: _, ref value } => { + self.consume_operand(location, value); + } + InlineAsmOperand::Out { reg: _, late: _, place, .. } => { + if let Some(place) = place { + self.mutate_place(location, place, Shallow(None)); + } + } + InlineAsmOperand::InOut { reg: _, late: _, ref in_value, out_place } => { + self.consume_operand(location, in_value); + if let Some(out_place) = out_place { + self.mutate_place(location, out_place, Shallow(None)); + } + } + InlineAsmOperand::Const { value: _ } + | InlineAsmOperand::SymFn { value: _ } + | InlineAsmOperand::SymStatic { def_id: _ } => {} + } + } + } + TerminatorKind::Goto { target: _ } + | TerminatorKind::Abort + | TerminatorKind::Unreachable + | TerminatorKind::FalseEdge { real_target: _, imaginary_target: _ } + | TerminatorKind::FalseUnwind { real_target: _, unwind: _ } => { + // no data used, thus irrelevant to borrowck + } + } + + self.super_terminator(terminator, location); + } +} + +impl<'cx, 'tcx> InvalidationGenerator<'cx, 'tcx> { + /// Simulates mutation of a place. + fn mutate_place(&mut self, location: Location, place: Place<'tcx>, kind: AccessDepth) { + self.access_place( + location, + place, + (kind, Write(WriteKind::Mutate)), + LocalMutationIsAllowed::ExceptUpvars, + ); + } + + /// Simulates consumption of an operand. + fn consume_operand(&mut self, location: Location, operand: &Operand<'tcx>) { + match *operand { + Operand::Copy(place) => { + self.access_place( + location, + place, + (Deep, Read(ReadKind::Copy)), + LocalMutationIsAllowed::No, + ); + } + Operand::Move(place) => { + self.access_place( + location, + place, + (Deep, Write(WriteKind::Move)), + LocalMutationIsAllowed::Yes, + ); + } + Operand::Constant(_) => {} + } + } + + // Simulates consumption of an rvalue + fn consume_rvalue(&mut self, location: Location, rvalue: &Rvalue<'tcx>) { + match *rvalue { + Rvalue::Ref(_ /*rgn*/, bk, place) => { + let access_kind = match bk { + BorrowKind::Shallow => { + (Shallow(Some(ArtificialField::ShallowBorrow)), Read(ReadKind::Borrow(bk))) + } + BorrowKind::Shared => (Deep, Read(ReadKind::Borrow(bk))), + BorrowKind::Unique | BorrowKind::Mut { .. } => { + let wk = WriteKind::MutableBorrow(bk); + if allow_two_phase_borrow(bk) { + (Deep, Reservation(wk)) + } else { + (Deep, Write(wk)) + } + } + }; + + self.access_place(location, place, access_kind, LocalMutationIsAllowed::No); + } + + Rvalue::AddressOf(mutability, place) => { + let access_kind = match mutability { + Mutability::Mut => ( + Deep, + Write(WriteKind::MutableBorrow(BorrowKind::Mut { + allow_two_phase_borrow: false, + })), + ), + Mutability::Not => (Deep, Read(ReadKind::Borrow(BorrowKind::Shared))), + }; + + self.access_place(location, place, access_kind, LocalMutationIsAllowed::No); + } + + Rvalue::ThreadLocalRef(_) => {} + + Rvalue::Use(ref operand) + | Rvalue::Repeat(ref operand, _) + | Rvalue::UnaryOp(_ /*un_op*/, ref operand) + | Rvalue::Cast(_ /*cast_kind*/, ref operand, _ /*ty*/) + | Rvalue::ShallowInitBox(ref operand, _ /*ty*/) => { + self.consume_operand(location, operand) + } + Rvalue::CopyForDeref(ref place) => { + let op = &Operand::Copy(*place); + self.consume_operand(location, op); + } + + Rvalue::Len(place) | Rvalue::Discriminant(place) => { + let af = match *rvalue { + Rvalue::Len(..) => Some(ArtificialField::ArrayLength), + Rvalue::Discriminant(..) => None, + _ => unreachable!(), + }; + self.access_place( + location, + place, + (Shallow(af), Read(ReadKind::Copy)), + LocalMutationIsAllowed::No, + ); + } + + Rvalue::BinaryOp(_bin_op, box (ref operand1, ref operand2)) + | Rvalue::CheckedBinaryOp(_bin_op, box (ref operand1, ref operand2)) => { + self.consume_operand(location, operand1); + self.consume_operand(location, operand2); + } + + Rvalue::NullaryOp(_op, _ty) => {} + + Rvalue::Aggregate(_, ref operands) => { + for operand in operands { + self.consume_operand(location, operand); + } + } + } + } + + /// Simulates an access to a place. + fn access_place( + &mut self, + location: Location, + place: Place<'tcx>, + kind: (AccessDepth, ReadOrWrite), + _is_local_mutation_allowed: LocalMutationIsAllowed, + ) { + let (sd, rw) = kind; + // note: not doing check_access_permissions checks because they don't generate invalidates + self.check_access_for_conflict(location, place, sd, rw); + } + + fn check_access_for_conflict( + &mut self, + location: Location, + place: Place<'tcx>, + sd: AccessDepth, + rw: ReadOrWrite, + ) { + debug!( + "invalidation::check_access_for_conflict(location={:?}, place={:?}, sd={:?}, \ + rw={:?})", + location, place, sd, rw, + ); + let tcx = self.tcx; + let body = self.body; + let borrow_set = self.borrow_set; + let indices = self.borrow_set.indices(); + each_borrow_involving_path( + self, + tcx, + body, + location, + (sd, place), + borrow_set, + indices, + |this, borrow_index, borrow| { + match (rw, borrow.kind) { + // Obviously an activation is compatible with its own + // reservation (or even prior activating uses of same + // borrow); so don't check if they interfere. + // + // NOTE: *reservations* do conflict with themselves; + // thus aren't injecting unsoundness w/ this check.) + (Activation(_, activating), _) if activating == borrow_index => { + // Activating a borrow doesn't generate any invalidations, since we + // have already taken the reservation + } + + (Read(_), BorrowKind::Shallow | BorrowKind::Shared) + | ( + Read(ReadKind::Borrow(BorrowKind::Shallow)), + BorrowKind::Unique | BorrowKind::Mut { .. }, + ) => { + // Reads don't invalidate shared or shallow borrows + } + + (Read(_), BorrowKind::Unique | BorrowKind::Mut { .. }) => { + // Reading from mere reservations of mutable-borrows is OK. + if !is_active(&this.dominators, borrow, location) { + // If the borrow isn't active yet, reads don't invalidate it + assert!(allow_two_phase_borrow(borrow.kind)); + return Control::Continue; + } + + // Unique and mutable borrows are invalidated by reads from any + // involved path + this.emit_loan_invalidated_at(borrow_index, location); + } + + (Reservation(_) | Activation(_, _) | Write(_), _) => { + // unique or mutable borrows are invalidated by writes. + // Reservations count as writes since we need to check + // that activating the borrow will be OK + // FIXME(bob_twinkles) is this actually the right thing to do? + this.emit_loan_invalidated_at(borrow_index, location); + } + } + Control::Continue + }, + ); + } + + /// Generates a new `loan_invalidated_at(L, B)` fact. + fn emit_loan_invalidated_at(&mut self, b: BorrowIndex, l: Location) { + let lidx = self.location_table.start_index(l); + self.all_facts.loan_invalidated_at.push((lidx, b)); + } + + fn check_activations(&mut self, location: Location) { + // Two-phase borrow support: For each activation that is newly + // generated at this statement, check if it interferes with + // another borrow. + for &borrow_index in self.borrow_set.activations_at_location(location) { + let borrow = &self.borrow_set[borrow_index]; + + // only mutable borrows should be 2-phase + assert!(match borrow.kind { + BorrowKind::Shared | BorrowKind::Shallow => false, + BorrowKind::Unique | BorrowKind::Mut { .. } => true, + }); + + self.access_place( + location, + borrow.borrowed_place, + (Deep, Activation(WriteKind::MutableBorrow(borrow.kind), borrow_index)), + LocalMutationIsAllowed::No, + ); + + // We do not need to call `check_if_path_or_subpath_is_moved` + // again, as we already called it when we made the + // initial reservation. + } + } +} |