| use rustc::mir::visit::Visitor; |
| use rustc::mir::{self, Local, Location}; |
| use rustc::ty::{self, TyCtxt}; |
| use rustc_index::bit_set::BitSet; |
| use syntax_pos::DUMMY_SP; |
| |
| use crate::dataflow::{self, GenKillSet}; |
| |
| /// Whether a borrow to a `Local` has been created that could allow that `Local` to be mutated |
| /// indirectly. This could either be a mutable reference (`&mut`) or a shared borrow if the type of |
| /// that `Local` allows interior mutability. Operations that can mutate local's indirectly include: |
| /// assignments through a pointer (`*p = 42`), function calls, drop terminators and inline assembly. |
| /// |
| /// If this returns false for a `Local` at a given statement (or terminator), that `Local` could |
| /// not possibly have been mutated indirectly prior to that statement. |
| #[derive(Copy, Clone)] |
| pub struct IndirectlyMutableLocals<'mir, 'tcx> { |
| body: &'mir mir::Body<'tcx>, |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| } |
| |
| impl<'mir, 'tcx> IndirectlyMutableLocals<'mir, 'tcx> { |
| pub fn new( |
| tcx: TyCtxt<'tcx>, |
| body: &'mir mir::Body<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| ) -> Self { |
| IndirectlyMutableLocals { body, tcx, param_env } |
| } |
| |
| fn transfer_function<'a>( |
| &self, |
| trans: &'a mut GenKillSet<Local>, |
| ) -> TransferFunction<'a, 'mir, 'tcx> { |
| TransferFunction { |
| body: self.body, |
| tcx: self.tcx, |
| param_env: self.param_env, |
| trans |
| } |
| } |
| } |
| |
| impl<'mir, 'tcx> dataflow::BitDenotation<'tcx> for IndirectlyMutableLocals<'mir, 'tcx> { |
| type Idx = Local; |
| |
| fn name() -> &'static str { "mut_borrowed_locals" } |
| |
| fn bits_per_block(&self) -> usize { |
| self.body.local_decls.len() |
| } |
| |
| fn start_block_effect(&self, _entry_set: &mut BitSet<Local>) { |
| // Nothing is borrowed on function entry |
| } |
| |
| fn statement_effect( |
| &self, |
| trans: &mut GenKillSet<Local>, |
| loc: Location, |
| ) { |
| let stmt = &self.body[loc.block].statements[loc.statement_index]; |
| self.transfer_function(trans).visit_statement(stmt, loc); |
| } |
| |
| fn terminator_effect( |
| &self, |
| trans: &mut GenKillSet<Local>, |
| loc: Location, |
| ) { |
| let terminator = self.body[loc.block].terminator(); |
| self.transfer_function(trans).visit_terminator(terminator, loc); |
| } |
| |
| fn propagate_call_return( |
| &self, |
| _in_out: &mut BitSet<Local>, |
| _call_bb: mir::BasicBlock, |
| _dest_bb: mir::BasicBlock, |
| _dest_place: &mir::Place<'tcx>, |
| ) { |
| // Nothing to do when a call returns successfully |
| } |
| } |
| |
| impl<'mir, 'tcx> dataflow::BottomValue for IndirectlyMutableLocals<'mir, 'tcx> { |
| // bottom = unborrowed |
| const BOTTOM_VALUE: bool = false; |
| } |
| |
| /// A `Visitor` that defines the transfer function for `IndirectlyMutableLocals`. |
| struct TransferFunction<'a, 'mir, 'tcx> { |
| trans: &'a mut GenKillSet<Local>, |
| body: &'mir mir::Body<'tcx>, |
| tcx: TyCtxt<'tcx>, |
| param_env: ty::ParamEnv<'tcx>, |
| } |
| |
| impl<'tcx> TransferFunction<'_, '_, 'tcx> { |
| /// Returns `true` if this borrow would allow mutation of the `borrowed_place`. |
| fn borrow_allows_mutation( |
| &self, |
| kind: mir::BorrowKind, |
| borrowed_place: &mir::Place<'tcx>, |
| ) -> bool { |
| match kind { |
| mir::BorrowKind::Mut { .. } => true, |
| |
| | mir::BorrowKind::Shared |
| | mir::BorrowKind::Shallow |
| | mir::BorrowKind::Unique |
| => !borrowed_place |
| .ty(self.body, self.tcx) |
| .ty |
| .is_freeze(self.tcx, self.param_env, DUMMY_SP), |
| } |
| } |
| } |
| |
| impl<'tcx> Visitor<'tcx> for TransferFunction<'_, '_, 'tcx> { |
| fn visit_rvalue( |
| &mut self, |
| rvalue: &mir::Rvalue<'tcx>, |
| location: Location, |
| ) { |
| if let mir::Rvalue::Ref(_, kind, ref borrowed_place) = *rvalue { |
| if self.borrow_allows_mutation(kind, borrowed_place) { |
| match borrowed_place.base { |
| mir::PlaceBase::Local(borrowed_local) if !borrowed_place.is_indirect() |
| => self.trans.gen(borrowed_local), |
| |
| _ => (), |
| } |
| } |
| } |
| |
| self.super_rvalue(rvalue, location); |
| } |
| |
| |
| fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Location) { |
| // This method purposely does nothing except call `super_terminator`. It exists solely to |
| // document the subtleties around drop terminators. |
| |
| self.super_terminator(terminator, location); |
| |
| if let mir::TerminatorKind::Drop { location: _, .. } |
| | mir::TerminatorKind::DropAndReplace { location: _, .. } = &terminator.kind |
| { |
| // Although drop terminators mutably borrow the location being dropped, that borrow |
| // cannot live beyond the drop terminator because the dropped location is invalidated. |
| } |
| } |
| } |