compiler/rustc_borrowck/src/invalidation.rs

   1 use rustc_data_structures::graph::dominators::Dominators;
   2 use rustc_middle::mir::visit::Visitor;
   3 use rustc_middle::mir::{BasicBlock, Body, Location, Place, Rvalue};
   4 use rustc_middle::mir::{BorrowKind, Mutability, Operand};
   5 use rustc_middle::mir::{InlineAsmOperand, Terminator, TerminatorKind};
   6 use rustc_middle::mir::{Statement, StatementKind};
   7 use rustc_middle::ty::TyCtxt;
   8
   9 use crate::{
  10     borrow_set::BorrowSet, facts::AllFacts, location::LocationTable, path_utils::*, AccessDepth,
  11     Activation, ArtificialField, BorrowIndex, Deep, LocalMutationIsAllowed, Read, ReadKind,
  12     ReadOrWrite, Reservation, Shallow, Write, WriteKind,
  13 };
  14
  15 pub(super) fn generate_invalidates<'tcx>(
  16     tcx: TyCtxt<'tcx>,
  17     all_facts: &mut Option<AllFacts>,
  18     location_table: &LocationTable,
  19     body: &Body<'tcx>,
  20     borrow_set: &BorrowSet<'tcx>,
  21 ) {
  22     if all_facts.is_none() {
  23         // Nothing to do if we don't have any facts
  24         return;
  25     }
  26
  27     if let Some(all_facts) = all_facts {
  28         let _prof_timer = tcx.prof.generic_activity("polonius_fact_generation");
  29         let dominators = body.basic_blocks.dominators();
  30         let mut ig = InvalidationGenerator {
  31             all_facts,
  32             borrow_set,
  33             tcx,
  34             location_table,
  35             body: &body,
  36             dominators,
  37         };
  38         ig.visit_body(body);
  39     }
  40 }
  41
  42 struct InvalidationGenerator<'cx, 'tcx> {
  43     tcx: TyCtxt<'tcx>,
  44     all_facts: &'cx mut AllFacts,
  45     location_table: &'cx LocationTable,
  46     body: &'cx Body<'tcx>,
  47     dominators: Dominators<BasicBlock>,
  48     borrow_set: &'cx BorrowSet<'tcx>,
  49 }
  50
  51 /// Visits the whole MIR and generates `invalidates()` facts.
  52 /// Most of the code implementing this was stolen from `borrow_check/mod.rs`.
  53 impl<'cx, 'tcx> Visitor<'tcx> for InvalidationGenerator<'cx, 'tcx> {
  54     fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) {
  55         self.check_activations(location);
  56
  57         match &statement.kind {
  58             StatementKind::Assign(box (lhs, rhs)) => {
  59                 self.consume_rvalue(location, rhs);
  60
  61                 self.mutate_place(location, *lhs, Shallow(None));
  62             }
  63             StatementKind::FakeRead(box (_, _)) => {
  64                 // Only relevant for initialized/liveness/safety checks.
  65             }
  66             StatementKind::CopyNonOverlapping(box rustc_middle::mir::CopyNonOverlapping {
  67                 ref src,
  68                 ref dst,
  69                 ref count,
  70             }) => {
  71                 self.consume_operand(location, src);
  72                 self.consume_operand(location, dst);
  73                 self.consume_operand(location, count);
  74             }
  75             // Only relevant for mir typeck
  76             StatementKind::AscribeUserType(..)
  77             // Doesn't have any language semantics
  78             | StatementKind::Coverage(..)
  79             // Takes a `bool` argument, and has no return value, thus being irrelevant for borrowck
  80             | StatementKind::Assume(..)
  81             // Does not actually affect borrowck
  82             | StatementKind::StorageLive(..) => {}
  83             StatementKind::StorageDead(local) => {
  84                 self.access_place(
  85                     location,
  86                     Place::from(*local),
  87                     (Shallow(None), Write(WriteKind::StorageDeadOrDrop)),
  88                     LocalMutationIsAllowed::Yes,
  89                 );
  90             }
  91             StatementKind::Nop
  92             | StatementKind::Retag { .. }
  93             | StatementKind::Deinit(..)
  94             | StatementKind::SetDiscriminant { .. } => {
  95                 bug!("Statement not allowed in this MIR phase")
  96             }
  97         }
  98
  99         self.super_statement(statement, location);
 100     }
 101
 102     fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
 103         self.check_activations(location);
 104
 105         match &terminator.kind {
 106             TerminatorKind::SwitchInt { ref discr, switch_ty: _, targets: _ } => {
 107                 self.consume_operand(location, discr);
 108             }
 109             TerminatorKind::Drop { place: drop_place, target: _, unwind: _ } => {
 110                 self.access_place(
 111                     location,
 112                     *drop_place,
 113                     (AccessDepth::Drop, Write(WriteKind::StorageDeadOrDrop)),
 114                     LocalMutationIsAllowed::Yes,
 115                 );
 116             }
 117             TerminatorKind::DropAndReplace {
 118                 place: drop_place,
 119                 value: ref new_value,
 120                 target: _,
 121                 unwind: _,
 122             } => {
 123                 self.mutate_place(location, *drop_place, Deep);
 124                 self.consume_operand(location, new_value);
 125             }
 126             TerminatorKind::Call {
 127                 ref func,
 128                 ref args,
 129                 destination,
 130                 target: _,
 131                 cleanup: _,
 132                 from_hir_call: _,
 133                 fn_span: _,
 134             } => {
 135                 self.consume_operand(location, func);
 136                 for arg in args {
 137                     self.consume_operand(location, arg);
 138                 }
 139                 self.mutate_place(location, *destination, Deep);
 140             }
 141             TerminatorKind::Assert { ref cond, expected: _, ref msg, target: _, cleanup: _ } => {
 142                 self.consume_operand(location, cond);
 143                 use rustc_middle::mir::AssertKind;
 144                 if let AssertKind::BoundsCheck { ref len, ref index } = *msg {
 145                     self.consume_operand(location, len);
 146                     self.consume_operand(location, index);
 147                 }
 148             }
 149             TerminatorKind::Yield { ref value, resume, resume_arg, drop: _ } => {
 150                 self.consume_operand(location, value);
 151
 152                 // Invalidate all borrows of local places
 153                 let borrow_set = self.borrow_set;
 154                 let resume = self.location_table.start_index(resume.start_location());
 155                 for (i, data) in borrow_set.iter_enumerated() {
 156                     if borrow_of_local_data(data.borrowed_place) {
 157                         self.all_facts.loan_invalidated_at.push((resume, i));
 158                     }
 159                 }
 160
 161                 self.mutate_place(location, *resume_arg, Deep);
 162             }
 163             TerminatorKind::Resume | TerminatorKind::Return | TerminatorKind::GeneratorDrop => {
 164                 // Invalidate all borrows of local places
 165                 let borrow_set = self.borrow_set;
 166                 let start = self.location_table.start_index(location);
 167                 for (i, data) in borrow_set.iter_enumerated() {
 168                     if borrow_of_local_data(data.borrowed_place) {
 169                         self.all_facts.loan_invalidated_at.push((start, i));
 170                     }
 171                 }
 172             }
 173             TerminatorKind::InlineAsm {
 174                 template: _,
 175                 ref operands,
 176                 options: _,
 177                 line_spans: _,
 178                 destination: _,
 179                 cleanup: _,
 180             } => {
 181                 for op in operands {
 182                     match *op {
 183                         InlineAsmOperand::In { reg: _, ref value } => {
 184                             self.consume_operand(location, value);
 185                         }
 186                         InlineAsmOperand::Out { reg: _, late: _, place, .. } => {
 187                             if let Some(place) = place {
 188                                 self.mutate_place(location, place, Shallow(None));
 189                             }
 190                         }
 191                         InlineAsmOperand::InOut { reg: _, late: _, ref in_value, out_place } => {
 192                             self.consume_operand(location, in_value);
 193                             if let Some(out_place) = out_place {
 194                                 self.mutate_place(location, out_place, Shallow(None));
 195                             }
 196                         }
 197                         InlineAsmOperand::Const { value: _ }
 198                         | InlineAsmOperand::SymFn { value: _ }
 199                         | InlineAsmOperand::SymStatic { def_id: _ } => {}
 200                     }
 201                 }
 202             }
 203             TerminatorKind::Goto { target: _ }
 204             | TerminatorKind::Abort
 205             | TerminatorKind::Unreachable
 206             | TerminatorKind::FalseEdge { real_target: _, imaginary_target: _ }
 207             | TerminatorKind::FalseUnwind { real_target: _, unwind: _ } => {
 208                 // no data used, thus irrelevant to borrowck
 209             }
 210         }
 211
 212         self.super_terminator(terminator, location);
 213     }
 214 }
 215
 216 impl<'cx, 'tcx> InvalidationGenerator<'cx, 'tcx> {
 217     /// Simulates mutation of a place.
 218     fn mutate_place(&mut self, location: Location, place: Place<'tcx>, kind: AccessDepth) {
 219         self.access_place(
 220             location,
 221             place,
 222             (kind, Write(WriteKind::Mutate)),
 223             LocalMutationIsAllowed::ExceptUpvars,
 224         );
 225     }
 226
 227     /// Simulates consumption of an operand.
 228     fn consume_operand(&mut self, location: Location, operand: &Operand<'tcx>) {
 229         match *operand {
 230             Operand::Copy(place) => {
 231                 self.access_place(
 232                     location,
 233                     place,
 234                     (Deep, Read(ReadKind::Copy)),
 235                     LocalMutationIsAllowed::No,
 236                 );
 237             }
 238             Operand::Move(place) => {
 239                 self.access_place(
 240                     location,
 241                     place,
 242                     (Deep, Write(WriteKind::Move)),
 243                     LocalMutationIsAllowed::Yes,
 244                 );
 245             }
 246             Operand::Constant(_) => {}
 247         }
 248     }
 249
 250     // Simulates consumption of an rvalue
 251     fn consume_rvalue(&mut self, location: Location, rvalue: &Rvalue<'tcx>) {
 252         match *rvalue {
 253             Rvalue::Ref(_ /*rgn*/, bk, place) => {
 254                 let access_kind = match bk {
 255                     BorrowKind::Shallow => {
 256                         (Shallow(Some(ArtificialField::ShallowBorrow)), Read(ReadKind::Borrow(bk)))
 257                     }
 258                     BorrowKind::Shared => (Deep, Read(ReadKind::Borrow(bk))),
 259                     BorrowKind::Unique | BorrowKind::Mut { .. } => {
 260                         let wk = WriteKind::MutableBorrow(bk);
 261                         if allow_two_phase_borrow(bk) {
 262                             (Deep, Reservation(wk))
 263                         } else {
 264                             (Deep, Write(wk))
 265                         }
 266                     }
 267                 };
 268
 269                 self.access_place(location, place, access_kind, LocalMutationIsAllowed::No);
 270             }
 271
 272             Rvalue::AddressOf(mutability, place) => {
 273                 let access_kind = match mutability {
 274                     Mutability::Mut => (
 275                         Deep,
 276                         Write(WriteKind::MutableBorrow(BorrowKind::Mut {
 277                             allow_two_phase_borrow: false,
 278                         })),
 279                     ),
 280                     Mutability::Not => (Deep, Read(ReadKind::Borrow(BorrowKind::Shared))),
 281                 };
 282
 283                 self.access_place(location, place, access_kind, LocalMutationIsAllowed::No);
 284             }
 285
 286             Rvalue::ThreadLocalRef(_) => {}
 287
 288             Rvalue::Use(ref operand)
 289             | Rvalue::Repeat(ref operand, _)
 290             | Rvalue::UnaryOp(_ /*un_op*/, ref operand)
 291             | Rvalue::Cast(_ /*cast_kind*/, ref operand, _ /*ty*/)
 292             | Rvalue::ShallowInitBox(ref operand, _ /*ty*/) => {
 293                 self.consume_operand(location, operand)
 294             }
 295             Rvalue::CopyForDeref(ref place) => {
 296                 let op = &Operand::Copy(*place);
 297                 self.consume_operand(location, op);
 298             }
 299
 300             Rvalue::Len(place) | Rvalue::Discriminant(place) => {
 301                 let af = match *rvalue {
 302                     Rvalue::Len(..) => Some(ArtificialField::ArrayLength),
 303                     Rvalue::Discriminant(..) => None,
 304                     _ => unreachable!(),
 305                 };
 306                 self.access_place(
 307                     location,
 308                     place,
 309                     (Shallow(af), Read(ReadKind::Copy)),
 310                     LocalMutationIsAllowed::No,
 311                 );
 312             }
 313
 314             Rvalue::BinaryOp(_bin_op, box (ref operand1, ref operand2))
 315             | Rvalue::CheckedBinaryOp(_bin_op, box (ref operand1, ref operand2)) => {
 316                 self.consume_operand(location, operand1);
 317                 self.consume_operand(location, operand2);
 318             }
 319
 320             Rvalue::NullaryOp(_op, _ty) => {}
 321
 322             Rvalue::Aggregate(_, ref operands) => {
 323                 for operand in operands {
 324                     self.consume_operand(location, operand);
 325                 }
 326             }
 327         }
 328     }
 329
 330     /// Simulates an access to a place.
 331     fn access_place(
 332         &mut self,
 333         location: Location,
 334         place: Place<'tcx>,
 335         kind: (AccessDepth, ReadOrWrite),
 336         _is_local_mutation_allowed: LocalMutationIsAllowed,
 337     ) {
 338         let (sd, rw) = kind;
 339         // note: not doing check_access_permissions checks because they don't generate invalidates
 340         self.check_access_for_conflict(location, place, sd, rw);
 341     }
 342
 343     fn check_access_for_conflict(
 344         &mut self,
 345         location: Location,
 346         place: Place<'tcx>,
 347         sd: AccessDepth,
 348         rw: ReadOrWrite,
 349     ) {
 350         debug!(
 351             "invalidation::check_access_for_conflict(location={:?}, place={:?}, sd={:?}, \
 352              rw={:?})",
 353             location, place, sd, rw,
 354         );
 355         let tcx = self.tcx;
 356         let body = self.body;
 357         let borrow_set = self.borrow_set;
 358         let indices = self.borrow_set.indices();
 359         each_borrow_involving_path(
 360             self,
 361             tcx,
 362             body,
 363             location,
 364             (sd, place),
 365             borrow_set,
 366             indices,
 367             |this, borrow_index, borrow| {
 368                 match (rw, borrow.kind) {
 369                     // Obviously an activation is compatible with its own
 370                     // reservation (or even prior activating uses of same
 371                     // borrow); so don't check if they interfere.
 372                     //
 373                     // NOTE: *reservations* do conflict with themselves;
 374                     // thus aren't injecting unsoundness w/ this check.)
 375                     (Activation(_, activating), _) if activating == borrow_index => {
 376                         // Activating a borrow doesn't generate any invalidations, since we
 377                         // have already taken the reservation
 378                     }
 379
 380                     (Read(_), BorrowKind::Shallow | BorrowKind::Shared)
 381                     | (
 382                         Read(ReadKind::Borrow(BorrowKind::Shallow)),
 383                         BorrowKind::Unique | BorrowKind::Mut { .. },
 384                     ) => {
 385                         // Reads don't invalidate shared or shallow borrows
 386                     }
 387
 388                     (Read(_), BorrowKind::Unique | BorrowKind::Mut { .. }) => {
 389                         // Reading from mere reservations of mutable-borrows is OK.
 390                         if !is_active(&this.dominators, borrow, location) {
 391                             // If the borrow isn't active yet, reads don't invalidate it
 392                             assert!(allow_two_phase_borrow(borrow.kind));
 393                             return Control::Continue;
 394                         }
 395
 396                         // Unique and mutable borrows are invalidated by reads from any
 397                         // involved path
 398                         this.emit_loan_invalidated_at(borrow_index, location);
 399                     }
 400
 401                     (Reservation(_) | Activation(_, _) | Write(_), _) => {
 402                         // unique or mutable borrows are invalidated by writes.
 403                         // Reservations count as writes since we need to check
 404                         // that activating the borrow will be OK
 405                         // FIXME(bob_twinkles) is this actually the right thing to do?
 406                         this.emit_loan_invalidated_at(borrow_index, location);
 407                     }
 408                 }
 409                 Control::Continue
 410             },
 411         );
 412     }
 413
 414     /// Generates a new `loan_invalidated_at(L, B)` fact.
 415     fn emit_loan_invalidated_at(&mut self, b: BorrowIndex, l: Location) {
 416         let lidx = self.location_table.start_index(l);
 417         self.all_facts.loan_invalidated_at.push((lidx, b));
 418     }
 419
 420     fn check_activations(&mut self, location: Location) {
 421         // Two-phase borrow support: For each activation that is newly
 422         // generated at this statement, check if it interferes with
 423         // another borrow.
 424         for &borrow_index in self.borrow_set.activations_at_location(location) {
 425             let borrow = &self.borrow_set[borrow_index];
 426
 427             // only mutable borrows should be 2-phase
 428             assert!(match borrow.kind {
 429                 BorrowKind::Shared | BorrowKind::Shallow => false,
 430                 BorrowKind::Unique | BorrowKind::Mut { .. } => true,
 431             });
 432
 433             self.access_place(
 434                 location,
 435                 borrow.borrowed_place,
 436                 (Deep, Activation(WriteKind::MutableBorrow(borrow.kind), borrow_index)),
 437                 LocalMutationIsAllowed::No,
 438             );
 439
 440             // We do not need to call `check_if_path_or_subpath_is_moved`
 441             // again, as we already called it when we made the
 442             // initial reservation.
 443         }
 444     }
 445 }