1 // Copyright 2012-2017 The Rust Project Developers. See the COPYRIGHT
2 // file at the top-level directory of this distribution and at
3 // http://rust-lang.org/COPYRIGHT.
5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
8 // option. This file may not be copied, modified, or distributed
9 // except according to those terms.
12 use rustc::hir::def_id::DefId;
13 use rustc::middle::region;
14 use rustc::mir::{self, Location, Place, Mir};
15 use rustc::mir::visit::{PlaceContext, Visitor};
16 use rustc::ty::{self, Region, TyCtxt};
17 use rustc::ty::RegionKind;
18 use rustc::ty::RegionKind::ReScope;
19 use rustc::util::nodemap::{FxHashMap, FxHashSet};
21 use rustc_data_structures::bitslice::{BitwiseOperator};
22 use rustc_data_structures::indexed_set::{IdxSet};
23 use rustc_data_structures::indexed_vec::{Idx, IndexVec};
25 use dataflow::{BitDenotation, BlockSets, InitialFlow};
26 pub use dataflow::indexes::{BorrowIndex, ReserveOrActivateIndex};
27 use borrow_check::nll::region_infer::RegionInferenceContext;
28 use borrow_check::nll::ToRegionVid;
36 /// `Borrows` stores the data used in the analyses that track the flow
39 /// It uniquely identifies every borrow (`Rvalue::Ref`) by a
40 /// `BorrowIndex`, and maps each such index to a `BorrowData`
41 /// describing the borrow. These indexes are used for representing the
42 /// borrows in compact bitvectors.
43 pub struct Borrows<'a, 'gcx: 'tcx, 'tcx: 'a> {
44 tcx: TyCtxt<'a, 'gcx, 'tcx>,
46 scope_tree: Rc<region::ScopeTree>,
47 root_scope: Option<region::Scope>,
49 /// The fundamental map relating bitvector indexes to the borrows
51 borrows: IndexVec<BorrowIndex, BorrowData<'tcx>>,
53 /// Each borrow is also uniquely identified in the MIR by the
54 /// `Location` of the assignment statement in which it appears on
55 /// the right hand side; we map each such location to the
56 /// corresponding `BorrowIndex`.
57 location_map: FxHashMap<Location, BorrowIndex>,
59 /// Every borrow in MIR is immediately stored into a place via an
60 /// assignment statement. This maps each such assigned place back
61 /// to its borrow-indexes.
62 assigned_map: FxHashMap<Place<'tcx>, FxHashSet<BorrowIndex>>,
64 /// Every borrow has a region; this maps each such regions back to
65 /// its borrow-indexes.
66 region_map: FxHashMap<Region<'tcx>, FxHashSet<BorrowIndex>>,
67 local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
68 region_span_map: FxHashMap<RegionKind, Span>,
69 nonlexical_regioncx: Option<Rc<RegionInferenceContext<'tcx>>>,
72 // Two-phase borrows actually requires two flow analyses; they need
73 // to be separate because the final results of the first are used to
74 // construct the gen+kill sets for the second. (The dataflow system
75 // is not designed to allow the gen/kill sets to change during the
76 // fixed-point iteration.)
78 /// The `Reservations` analysis is the first of the two flow analyses
79 /// tracking (phased) borrows. It computes where a borrow is reserved;
80 /// i.e. where it can reach in the control flow starting from its
81 /// initial `assigned = &'rgn borrowed` statement, and ending
82 /// whereever `'rgn` itself ends.
83 pub(crate) struct Reservations<'a, 'gcx: 'tcx, 'tcx: 'a>(pub(crate) Borrows<'a, 'gcx, 'tcx>);
85 /// The `ActiveBorrows` analysis is the second of the two flow
86 /// analyses tracking (phased) borrows. It computes where any given
87 /// borrow `&assigned = &'rgn borrowed` is *active*, which starts at
88 /// the first use of `assigned` after the reservation has started, and
89 /// ends whereever `'rgn` itself ends.
90 pub(crate) struct ActiveBorrows<'a, 'gcx: 'tcx, 'tcx: 'a>(pub(crate) Borrows<'a, 'gcx, 'tcx>);
92 impl<'a, 'gcx, 'tcx> Reservations<'a, 'gcx, 'tcx> {
93 pub(crate) fn new(b: Borrows<'a, 'gcx, 'tcx>) -> Self { Reservations(b) }
94 pub(crate) fn location(&self, idx: ReserveOrActivateIndex) -> &Location {
95 self.0.location(idx.borrow_index())
99 impl<'a, 'gcx, 'tcx> ActiveBorrows<'a, 'gcx, 'tcx> {
100 pub(crate) fn new(r: Reservations<'a, 'gcx, 'tcx>) -> Self { ActiveBorrows(r.0) }
101 pub(crate) fn location(&self, idx: ReserveOrActivateIndex) -> &Location {
102 self.0.location(idx.borrow_index())
106 // temporarily allow some dead fields: `kind` and `region` will be
107 // needed by borrowck; `borrowed_place` will probably be a MovePathIndex when
108 // that is extended to include borrowed data paths.
111 pub struct BorrowData<'tcx> {
112 pub(crate) location: Location,
113 pub(crate) kind: mir::BorrowKind,
114 pub(crate) region: Region<'tcx>,
115 pub(crate) borrowed_place: mir::Place<'tcx>,
116 pub(crate) assigned_place: mir::Place<'tcx>,
119 impl<'tcx> fmt::Display for BorrowData<'tcx> {
120 fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
121 let kind = match self.kind {
122 mir::BorrowKind::Shared => "",
123 mir::BorrowKind::Unique => "uniq ",
124 mir::BorrowKind::Mut => "mut ",
126 let region = format!("{}", self.region);
127 let region = if region.len() > 0 { format!("{} ", region) } else { region };
128 write!(w, "&{}{}{:?}", region, kind, self.borrowed_place)
132 impl ReserveOrActivateIndex {
133 fn reserved(i: BorrowIndex) -> Self { ReserveOrActivateIndex::new((i.index() * 2)) }
134 fn active(i: BorrowIndex) -> Self { ReserveOrActivateIndex::new((i.index() * 2) + 1) }
136 pub(crate) fn is_reservation(self) -> bool { self.index() % 2 == 0 }
137 pub(crate) fn is_activation(self) -> bool { self.index() % 2 == 1}
139 pub(crate) fn kind(self) -> &'static str {
140 if self.is_reservation() { "reserved" } else { "active" }
142 pub(crate) fn borrow_index(self) -> BorrowIndex {
143 BorrowIndex::new(self.index() / 2)
147 impl<'a, 'gcx, 'tcx> Borrows<'a, 'gcx, 'tcx> {
148 pub fn new(tcx: TyCtxt<'a, 'gcx, 'tcx>,
150 nonlexical_regioncx: Option<Rc<RegionInferenceContext<'tcx>>>,
152 body_id: Option<hir::BodyId>)
154 let scope_tree = tcx.region_scope_tree(def_id);
155 let root_scope = body_id.map(|body_id| {
156 region::Scope::CallSite(tcx.hir.body(body_id).value.hir_id.local_id)
158 let mut visitor = GatherBorrows {
161 idx_vec: IndexVec::new(),
162 location_map: FxHashMap(),
163 assigned_map: FxHashMap(),
164 region_map: FxHashMap(),
165 local_map: FxHashMap(),
166 region_span_map: FxHashMap()
168 visitor.visit_mir(mir);
169 return Borrows { tcx: tcx,
171 borrows: visitor.idx_vec,
174 location_map: visitor.location_map,
175 assigned_map: visitor.assigned_map,
176 region_map: visitor.region_map,
177 local_map: visitor.local_map,
178 region_span_map: visitor.region_span_map,
179 nonlexical_regioncx };
181 struct GatherBorrows<'a, 'gcx: 'tcx, 'tcx: 'a> {
182 tcx: TyCtxt<'a, 'gcx, 'tcx>,
184 idx_vec: IndexVec<BorrowIndex, BorrowData<'tcx>>,
185 location_map: FxHashMap<Location, BorrowIndex>,
186 assigned_map: FxHashMap<Place<'tcx>, FxHashSet<BorrowIndex>>,
187 region_map: FxHashMap<Region<'tcx>, FxHashSet<BorrowIndex>>,
188 local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
189 region_span_map: FxHashMap<RegionKind, Span>,
192 impl<'a, 'gcx, 'tcx> Visitor<'tcx> for GatherBorrows<'a, 'gcx, 'tcx> {
193 fn visit_assign(&mut self,
194 block: mir::BasicBlock,
195 assigned_place: &mir::Place<'tcx>,
196 rvalue: &mir::Rvalue<'tcx>,
197 location: mir::Location) {
198 fn root_local(mut p: &mir::Place<'_>) -> Option<mir::Local> {
200 mir::Place::Projection(pi) => p = &pi.base,
201 mir::Place::Static(_) => return None,
202 mir::Place::Local(l) => return Some(*l)
206 if let mir::Rvalue::Ref(region, kind, ref borrowed_place) = *rvalue {
207 if is_unsafe_place(self.tcx, self.mir, borrowed_place) { return; }
209 let borrow = BorrowData {
210 location, kind, region,
211 borrowed_place: borrowed_place.clone(),
212 assigned_place: assigned_place.clone(),
214 let idx = self.idx_vec.push(borrow);
215 self.location_map.insert(location, idx);
217 insert(&mut self.assigned_map, assigned_place, idx);
218 insert(&mut self.region_map, ®ion, idx);
219 if let Some(local) = root_local(borrowed_place) {
220 insert(&mut self.local_map, &local, idx);
224 return self.super_assign(block, assigned_place, rvalue, location);
226 fn insert<'a, K, V>(map: &'a mut FxHashMap<K, FxHashSet<V>>,
229 where K: Clone+Eq+Hash, V: Eq+Hash
232 .or_insert(FxHashSet())
237 fn visit_rvalue(&mut self,
238 rvalue: &mir::Rvalue<'tcx>,
239 location: mir::Location) {
240 if let mir::Rvalue::Ref(region, kind, ref place) = *rvalue {
241 // double-check that we already registered a BorrowData for this
243 let mut found_it = false;
244 for idx in &self.region_map[region] {
245 let bd = &self.idx_vec[*idx];
246 if bd.location == location &&
248 bd.region == region &&
249 bd.borrowed_place == *place
255 assert!(found_it, "Ref {:?} at {:?} missing BorrowData", rvalue, location);
258 return self.super_rvalue(rvalue, location);
261 fn visit_statement(&mut self,
262 block: mir::BasicBlock,
263 statement: &mir::Statement<'tcx>,
264 location: Location) {
265 if let mir::StatementKind::EndRegion(region_scope) = statement.kind {
266 self.region_span_map.insert(ReScope(region_scope), statement.source_info.span);
268 return self.super_statement(block, statement, location);
273 pub fn borrows(&self) -> &IndexVec<BorrowIndex, BorrowData<'tcx>> { &self.borrows }
275 pub fn scope_tree(&self) -> &Rc<region::ScopeTree> { &self.scope_tree }
277 pub fn location(&self, idx: BorrowIndex) -> &Location {
278 &self.borrows[idx].location
281 /// Add all borrows to the kill set, if those borrows are out of scope at `location`.
283 /// `is_activations` tracks whether we are in the Reservations or
284 /// the ActiveBorrows flow analysis, and does not set the
285 /// activation kill bits in the former case. (Technically, we
286 /// could set those kill bits without such a guard, since they are
287 /// never gen'ed by Reservations in the first place. But it makes
288 /// the instrumentation and graph renderings nicer to leave
289 /// activations out when of the Reservations kill sets.)
290 fn kill_loans_out_of_scope_at_location(&self,
291 sets: &mut BlockSets<ReserveOrActivateIndex>,
293 is_activations: bool) {
294 if let Some(ref regioncx) = self.nonlexical_regioncx {
295 // NOTE: The state associated with a given `location`
296 // reflects the dataflow on entry to the statement. If it
297 // does not contain `borrow_region`, then then that means
298 // that the statement at `location` kills the borrow.
300 // We are careful always to call this function *before* we
301 // set up the gen-bits for the statement or
302 // termanator. That way, if the effect of the statement or
303 // terminator *does* introduce a new loan of the same
304 // region, then setting that gen-bit will override any
305 // potential kill introduced here.
306 for (borrow_index, borrow_data) in self.borrows.iter_enumerated() {
307 let borrow_region = borrow_data.region.to_region_vid();
308 if !regioncx.region_contains_point(borrow_region, location) {
309 sets.kill(&ReserveOrActivateIndex::reserved(borrow_index));
311 sets.kill(&ReserveOrActivateIndex::active(borrow_index));
318 /// Models statement effect in Reservations and ActiveBorrows flow
319 /// analyses; `is activations` tells us if we are in the latter
321 fn statement_effect_on_borrows(&self,
322 sets: &mut BlockSets<ReserveOrActivateIndex>,
324 is_activations: bool) {
325 let block = &self.mir.basic_blocks().get(location.block).unwrap_or_else(|| {
326 panic!("could not find block at location {:?}", location);
328 let stmt = block.statements.get(location.statement_index).unwrap_or_else(|| {
329 panic!("could not find statement at location {:?}");
332 // Do kills introduced by NLL before setting up any potential
333 // gens. (See NOTE in kill_loans_out_of_scope_at_location.)
334 self.kill_loans_out_of_scope_at_location(sets, location, is_activations);
337 // INVARIANT: `sets.on_entry` accurately captures
338 // reservations on entry to statement (b/c
339 // accumulates_intrablock_state is overridden for
342 // Now compute the activations generated by uses within
343 // the statement based on that reservation state.
344 let mut find = FindPlaceUses { sets, assigned_map: &self.assigned_map };
345 find.visit_statement(location.block, stmt, location);
349 // EndRegion kills any borrows (reservations and active borrows both)
350 mir::StatementKind::EndRegion(region_scope) => {
351 if let Some(borrow_indexes) = self.region_map.get(&ReScope(region_scope)) {
352 assert!(self.nonlexical_regioncx.is_none());
353 for idx in borrow_indexes {
354 sets.kill(&ReserveOrActivateIndex::reserved(*idx));
356 sets.kill(&ReserveOrActivateIndex::active(*idx));
360 // (if there is no entry, then there are no borrows to be tracked)
364 mir::StatementKind::Assign(_, ref rhs) => {
365 // NOTE: if/when the Assign case is revised to inspect
366 // the assigned_place here, make sure to also
367 // re-consider the current implementations of the
368 // propagate_call_return method.
370 if let mir::Rvalue::Ref(region, _, ref place) = *rhs {
371 if is_unsafe_place(self.tcx, self.mir, place) { return; }
372 if let RegionKind::ReEmpty = region {
373 // If the borrowed value is dead, the region for it
374 // can be empty. Don't track the borrow in that case.
378 let index = self.location_map.get(&location).unwrap_or_else(|| {
379 panic!("could not find BorrowIndex for location {:?}", location);
381 assert!(self.region_map.get(region).unwrap_or_else(|| {
382 panic!("could not find BorrowIndexs for region {:?}", region);
383 }).contains(&index));
384 sets.gen(&ReserveOrActivateIndex::reserved(*index));
388 mir::StatementKind::StorageDead(local) => {
389 // Make sure there are no remaining borrows for locals that
390 // are gone out of scope.
392 // FIXME: expand this to variables that are assigned over.
393 if let Some(borrow_indexes) = self.local_map.get(&local) {
394 sets.kill_all(borrow_indexes.iter()
395 .map(|b| ReserveOrActivateIndex::reserved(*b)));
397 sets.kill_all(borrow_indexes.iter()
398 .map(|b| ReserveOrActivateIndex::active(*b)));
403 mir::StatementKind::InlineAsm { .. } |
404 mir::StatementKind::SetDiscriminant { .. } |
405 mir::StatementKind::StorageLive(..) |
406 mir::StatementKind::Validate(..) |
407 mir::StatementKind::Nop => {}
412 /// Models terminator effect in Reservations and ActiveBorrows
413 /// flow analyses; `is activations` tells us if we are in the
415 fn terminator_effect_on_borrows(&self,
416 sets: &mut BlockSets<ReserveOrActivateIndex>,
418 is_activations: bool) {
419 let block = &self.mir.basic_blocks().get(location.block).unwrap_or_else(|| {
420 panic!("could not find block at location {:?}", location);
423 // Do kills introduced by NLL before setting up any potential
424 // gens. (See NOTE in kill_loans_out_of_scope_at_location.)
425 self.kill_loans_out_of_scope_at_location(sets, location, is_activations);
427 let term = block.terminator();
429 // INVARIANT: `sets.on_entry` accurately captures
430 // reservations on entry to terminator (b/c
431 // accumulates_intrablock_state is overridden for
434 // Now compute effect of the terminator on the activations
435 // themselves in the ActiveBorrows state.
436 let mut find = FindPlaceUses { sets, assigned_map: &self.assigned_map };
437 find.visit_terminator(location.block, term, location);
441 mir::TerminatorKind::Resume |
442 mir::TerminatorKind::Return |
443 mir::TerminatorKind::GeneratorDrop => {
444 // When we return from the function, then all `ReScope`-style regions
445 // are guaranteed to have ended.
446 // Normally, there would be `EndRegion` statements that come before,
447 // and hence most of these loans will already be dead -- but, in some cases
448 // like unwind paths, we do not always emit `EndRegion` statements, so we
449 // add some kills here as a "backup" and to avoid spurious error messages.
450 for (borrow_index, borrow_data) in self.borrows.iter_enumerated() {
451 if let ReScope(scope) = borrow_data.region {
452 // Check that the scope is not actually a scope from a function that is
453 // a parent of our closure. Note that the CallSite scope itself is
454 // *outside* of the closure, for some weird reason.
455 if let Some(root_scope) = self.root_scope {
456 if *scope != root_scope &&
457 self.scope_tree.is_subscope_of(*scope, root_scope)
459 sets.kill(&ReserveOrActivateIndex::reserved(borrow_index));
461 sets.kill(&ReserveOrActivateIndex::active(borrow_index));
468 mir::TerminatorKind::SwitchInt {..} |
469 mir::TerminatorKind::Drop {..} |
470 mir::TerminatorKind::DropAndReplace {..} |
471 mir::TerminatorKind::Call {..} |
472 mir::TerminatorKind::Assert {..} |
473 mir::TerminatorKind::Yield {..} |
474 mir::TerminatorKind::Goto {..} |
475 mir::TerminatorKind::FalseEdges {..} |
476 mir::TerminatorKind::Unreachable => {}
481 impl<'a, 'gcx, 'tcx> ActiveBorrows<'a, 'gcx, 'tcx> {
482 pub(crate) fn borrows(&self) -> &IndexVec<BorrowIndex, BorrowData<'tcx>> {
486 /// Returns the span for the "end point" given region. This will
487 /// return `None` if NLL is enabled, since that concept has no
488 /// meaning there. Otherwise, return region span if it exists and
489 /// span for end of the function if it doesn't exist.
490 pub(crate) fn opt_region_end_span(&self, region: &Region) -> Option<Span> {
491 match self.0.nonlexical_regioncx {
494 match self.0.region_span_map.get(region) {
495 Some(span) => Some(span.end_point()),
496 None => Some(self.0.mir.span.end_point())
503 /// `FindPlaceUses` is a MIR visitor that updates `self.sets` for all
504 /// of the borrows activated by a given statement or terminator.
508 /// The `ActiveBorrows` flow analysis, when inspecting any given
509 /// statement or terminator, needs to "generate" (i.e. set to 1) all
510 /// of the bits for the borrows that are activated by that
511 /// statement/terminator.
513 /// This struct will seek out all places that are assignment-targets
514 /// for borrows (gathered in `self.assigned_map`; see also the
515 /// `assigned_map` in `struct Borrows`), and set the corresponding
516 /// gen-bits for activations of those borrows in `self.sets`
517 struct FindPlaceUses<'a, 'b: 'a, 'tcx: 'a> {
518 assigned_map: &'a FxHashMap<Place<'tcx>, FxHashSet<BorrowIndex>>,
519 sets: &'a mut BlockSets<'b, ReserveOrActivateIndex>,
522 impl<'a, 'b, 'tcx> FindPlaceUses<'a, 'b, 'tcx> {
523 fn has_been_reserved(&self, b: &BorrowIndex) -> bool {
524 self.sets.on_entry.contains(&ReserveOrActivateIndex::reserved(*b))
527 /// return whether `context` should be considered a "use" of a
528 /// place found in that context. "Uses" activate associated
529 /// borrows (at least when such uses occur while the borrow also
530 /// has a reservation at the time).
531 fn is_potential_use(context: PlaceContext) -> bool {
533 // storage effects on an place do not activate it
534 PlaceContext::StorageLive | PlaceContext::StorageDead => false,
536 // validation effects do not activate an place
538 // FIXME: Should they? Is it just another read? Or can we
539 // guarantee it won't dereference the stored address? How
540 // "deep" does validation go?
541 PlaceContext::Validate => false,
543 // FIXME: This is here to not change behaviour from before
544 // AsmOutput existed, but it's not necessarily a pure overwrite.
545 // so it's possible this should activate the place.
546 PlaceContext::AsmOutput |
547 // pure overwrites of an place do not activate it. (note
548 // PlaceContext::Call is solely about dest place)
549 PlaceContext::Store | PlaceContext::Call => false,
551 // reads of an place *do* activate it
555 PlaceContext::Inspect |
556 PlaceContext::Borrow { .. } |
557 PlaceContext::Projection(..) => true,
562 impl<'a, 'b, 'tcx> Visitor<'tcx> for FindPlaceUses<'a, 'b, 'tcx> {
563 fn visit_place(&mut self,
564 place: &mir::Place<'tcx>,
565 context: PlaceContext<'tcx>,
566 location: Location) {
567 debug!("FindPlaceUses place: {:?} assigned from borrows: {:?} \
568 used in context: {:?} at location: {:?}",
569 place, self.assigned_map.get(place), context, location);
570 if Self::is_potential_use(context) {
571 if let Some(borrows) = self.assigned_map.get(place) {
572 for borrow_idx in borrows {
573 debug!("checking if index {:?} for {:?} is reserved ({}) \
574 and thus needs active gen-bit set in sets {:?}",
575 borrow_idx, place, self.has_been_reserved(&borrow_idx), self.sets);
576 if self.has_been_reserved(&borrow_idx) {
577 self.sets.gen(&ReserveOrActivateIndex::active(*borrow_idx));
579 // (This can certainly happen in valid code. I
580 // just want to know about it in the short
582 debug!("encountered use of Place {:?} of borrow_idx {:?} \
583 at location {:?} outside of reservation",
584 place, borrow_idx, location);
590 self.super_place(place, context, location);
595 impl<'a, 'gcx, 'tcx> BitDenotation for Reservations<'a, 'gcx, 'tcx> {
596 type Idx = ReserveOrActivateIndex;
597 fn name() -> &'static str { "reservations" }
598 fn bits_per_block(&self) -> usize {
599 self.0.borrows.len() * 2
601 fn start_block_effect(&self, _entry_set: &mut IdxSet<ReserveOrActivateIndex>) {
602 // no borrows of code region_scopes have been taken prior to
603 // function execution, so this method has no effect on
607 fn statement_effect(&self,
608 sets: &mut BlockSets<ReserveOrActivateIndex>,
609 location: Location) {
610 debug!("Reservations::statement_effect sets: {:?} location: {:?}", sets, location);
611 self.0.statement_effect_on_borrows(sets, location, false);
614 fn terminator_effect(&self,
615 sets: &mut BlockSets<ReserveOrActivateIndex>,
616 location: Location) {
617 debug!("Reservations::terminator_effect sets: {:?} location: {:?}", sets, location);
618 self.0.terminator_effect_on_borrows(sets, location, false);
621 fn propagate_call_return(&self,
622 _in_out: &mut IdxSet<ReserveOrActivateIndex>,
623 _call_bb: mir::BasicBlock,
624 _dest_bb: mir::BasicBlock,
625 _dest_place: &mir::Place) {
626 // there are no effects on borrows from method call return...
628 // ... but if overwriting a place can affect flow state, then
629 // latter is not true; see NOTE on Assign case in
630 // statement_effect_on_borrows.
634 impl<'a, 'gcx, 'tcx> BitDenotation for ActiveBorrows<'a, 'gcx, 'tcx> {
635 type Idx = ReserveOrActivateIndex;
636 fn name() -> &'static str { "active_borrows" }
638 /// Overriding this method; `ActiveBorrows` uses the intrablock
639 /// state in `on_entry` to track the current reservations (which
640 /// then affect the construction of the gen/kill sets for
642 fn accumulates_intrablock_state() -> bool { true }
644 fn bits_per_block(&self) -> usize {
645 self.0.borrows.len() * 2
648 fn start_block_effect(&self, _entry_sets: &mut IdxSet<ReserveOrActivateIndex>) {
649 // no borrows of code region_scopes have been taken prior to
650 // function execution, so this method has no effect on
654 fn statement_effect(&self,
655 sets: &mut BlockSets<ReserveOrActivateIndex>,
656 location: Location) {
657 debug!("ActiveBorrows::statement_effect sets: {:?} location: {:?}", sets, location);
658 self.0.statement_effect_on_borrows(sets, location, true);
661 fn terminator_effect(&self,
662 sets: &mut BlockSets<ReserveOrActivateIndex>,
663 location: Location) {
664 debug!("ActiveBorrows::terminator_effect sets: {:?} location: {:?}", sets, location);
665 self.0.terminator_effect_on_borrows(sets, location, true);
668 fn propagate_call_return(&self,
669 _in_out: &mut IdxSet<ReserveOrActivateIndex>,
670 _call_bb: mir::BasicBlock,
671 _dest_bb: mir::BasicBlock,
672 _dest_place: &mir::Place) {
673 // there are no effects on borrows from method call return...
675 // ... but If overwriting a place can affect flow state, then
676 // latter is not true; see NOTE on Assign case in
677 // statement_effect_on_borrows.
681 impl<'a, 'gcx, 'tcx> BitwiseOperator for Reservations<'a, 'gcx, 'tcx> {
683 fn join(&self, pred1: usize, pred2: usize) -> usize {
684 pred1 | pred2 // union effects of preds when computing reservations
688 impl<'a, 'gcx, 'tcx> BitwiseOperator for ActiveBorrows<'a, 'gcx, 'tcx> {
690 fn join(&self, pred1: usize, pred2: usize) -> usize {
691 pred1 | pred2 // union effects of preds when computing activations
695 impl<'a, 'gcx, 'tcx> InitialFlow for Reservations<'a, 'gcx, 'tcx> {
697 fn bottom_value() -> bool {
698 false // bottom = no Rvalue::Refs are reserved by default
702 fn is_unsafe_place<'a, 'gcx: 'tcx, 'tcx: 'a>(
703 tcx: TyCtxt<'a, 'gcx, 'tcx>,
705 place: &mir::Place<'tcx>
707 use self::mir::Place::*;
708 use self::mir::ProjectionElem;
712 Static(ref static_) => tcx.is_static_mut(static_.def_id),
713 Projection(ref proj) => {
715 ProjectionElem::Field(..) |
716 ProjectionElem::Downcast(..) |
717 ProjectionElem::Subslice { .. } |
718 ProjectionElem::ConstantIndex { .. } |
719 ProjectionElem::Index(_) => {
720 is_unsafe_place(tcx, mir, &proj.base)
722 ProjectionElem::Deref => {
723 let ty = proj.base.ty(mir, tcx).to_ty(tcx);
725 ty::TyRawPtr(..) => true,
726 _ => is_unsafe_place(tcx, mir, &proj.base),