346 lines
12 KiB
Rust
346 lines
12 KiB
Rust
use crate::nll::ToRegionVid;
|
|
use crate::path_utils::allow_two_phase_borrow;
|
|
use crate::place_ext::PlaceExt;
|
|
use crate::BorrowIndex;
|
|
use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexMap};
|
|
use rustc_index::bit_set::BitSet;
|
|
use rustc_middle::mir::traversal;
|
|
use rustc_middle::mir::visit::{MutatingUseContext, NonUseContext, PlaceContext, Visitor};
|
|
use rustc_middle::mir::{self, Body, Local, Location};
|
|
use rustc_middle::ty::{RegionVid, TyCtxt};
|
|
use rustc_mir_dataflow::move_paths::MoveData;
|
|
use std::fmt;
|
|
use std::ops::Index;
|
|
|
|
pub struct BorrowSet<'tcx> {
|
|
/// The fundamental map relating bitvector indexes to the borrows
|
|
/// in the MIR. Each borrow is also uniquely identified in the MIR
|
|
/// by the `Location` of the assignment statement in which it
|
|
/// appears on the right hand side. Thus the location is the map
|
|
/// key, and its position in the map corresponds to `BorrowIndex`.
|
|
pub location_map: FxIndexMap<Location, BorrowData<'tcx>>,
|
|
|
|
/// Locations which activate borrows.
|
|
/// NOTE: a given location may activate more than one borrow in the future
|
|
/// when more general two-phase borrow support is introduced, but for now we
|
|
/// only need to store one borrow index.
|
|
pub activation_map: FxHashMap<Location, Vec<BorrowIndex>>,
|
|
|
|
/// Map from local to all the borrows on that local.
|
|
pub local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
|
|
|
|
pub(crate) locals_state_at_exit: LocalsStateAtExit,
|
|
}
|
|
|
|
impl<'tcx> Index<BorrowIndex> for BorrowSet<'tcx> {
|
|
type Output = BorrowData<'tcx>;
|
|
|
|
fn index(&self, index: BorrowIndex) -> &BorrowData<'tcx> {
|
|
&self.location_map[index.as_usize()]
|
|
}
|
|
}
|
|
|
|
/// Location where a two-phase borrow is activated, if a borrow
|
|
/// is in fact a two-phase borrow.
|
|
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
|
|
pub enum TwoPhaseActivation {
|
|
NotTwoPhase,
|
|
NotActivated,
|
|
ActivatedAt(Location),
|
|
}
|
|
|
|
#[derive(Debug, Clone)]
|
|
pub struct BorrowData<'tcx> {
|
|
/// Location where the borrow reservation starts.
|
|
/// In many cases, this will be equal to the activation location but not always.
|
|
pub reserve_location: Location,
|
|
/// Location where the borrow is activated.
|
|
pub activation_location: TwoPhaseActivation,
|
|
/// What kind of borrow this is
|
|
pub kind: mir::BorrowKind,
|
|
/// The region for which this borrow is live
|
|
pub region: RegionVid,
|
|
/// Place from which we are borrowing
|
|
pub borrowed_place: mir::Place<'tcx>,
|
|
/// Place to which the borrow was stored
|
|
pub assigned_place: mir::Place<'tcx>,
|
|
}
|
|
|
|
impl<'tcx> fmt::Display for BorrowData<'tcx> {
|
|
fn fmt(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result {
|
|
let kind = match self.kind {
|
|
mir::BorrowKind::Shared => "",
|
|
mir::BorrowKind::Shallow => "shallow ",
|
|
mir::BorrowKind::Unique => "uniq ",
|
|
mir::BorrowKind::Mut { .. } => "mut ",
|
|
};
|
|
write!(w, "&{:?} {}{:?}", self.region, kind, self.borrowed_place)
|
|
}
|
|
}
|
|
|
|
pub enum LocalsStateAtExit {
|
|
AllAreInvalidated,
|
|
SomeAreInvalidated { has_storage_dead_or_moved: BitSet<Local> },
|
|
}
|
|
|
|
impl LocalsStateAtExit {
|
|
fn build<'tcx>(
|
|
locals_are_invalidated_at_exit: bool,
|
|
body: &Body<'tcx>,
|
|
move_data: &MoveData<'tcx>,
|
|
) -> Self {
|
|
struct HasStorageDead(BitSet<Local>);
|
|
|
|
impl<'tcx> Visitor<'tcx> for HasStorageDead {
|
|
fn visit_local(&mut self, local: &Local, ctx: PlaceContext, _: Location) {
|
|
if ctx == PlaceContext::NonUse(NonUseContext::StorageDead) {
|
|
self.0.insert(*local);
|
|
}
|
|
}
|
|
}
|
|
|
|
if locals_are_invalidated_at_exit {
|
|
LocalsStateAtExit::AllAreInvalidated
|
|
} else {
|
|
let mut has_storage_dead = HasStorageDead(BitSet::new_empty(body.local_decls.len()));
|
|
has_storage_dead.visit_body(&body);
|
|
let mut has_storage_dead_or_moved = has_storage_dead.0;
|
|
for move_out in &move_data.moves {
|
|
if let Some(index) = move_data.base_local(move_out.path) {
|
|
has_storage_dead_or_moved.insert(index);
|
|
}
|
|
}
|
|
LocalsStateAtExit::SomeAreInvalidated { has_storage_dead_or_moved }
|
|
}
|
|
}
|
|
}
|
|
|
|
impl<'tcx> BorrowSet<'tcx> {
|
|
pub fn build(
|
|
tcx: TyCtxt<'tcx>,
|
|
body: &Body<'tcx>,
|
|
locals_are_invalidated_at_exit: bool,
|
|
move_data: &MoveData<'tcx>,
|
|
) -> Self {
|
|
let mut visitor = GatherBorrows {
|
|
tcx,
|
|
body: &body,
|
|
location_map: Default::default(),
|
|
activation_map: Default::default(),
|
|
local_map: Default::default(),
|
|
pending_activations: Default::default(),
|
|
locals_state_at_exit: LocalsStateAtExit::build(
|
|
locals_are_invalidated_at_exit,
|
|
body,
|
|
move_data,
|
|
),
|
|
};
|
|
|
|
for (block, block_data) in traversal::preorder(&body) {
|
|
visitor.visit_basic_block_data(block, block_data);
|
|
}
|
|
|
|
BorrowSet {
|
|
location_map: visitor.location_map,
|
|
activation_map: visitor.activation_map,
|
|
local_map: visitor.local_map,
|
|
locals_state_at_exit: visitor.locals_state_at_exit,
|
|
}
|
|
}
|
|
|
|
pub(crate) fn activations_at_location(&self, location: Location) -> &[BorrowIndex] {
|
|
self.activation_map.get(&location).map_or(&[], |activations| &activations[..])
|
|
}
|
|
|
|
pub(crate) fn len(&self) -> usize {
|
|
self.location_map.len()
|
|
}
|
|
|
|
pub(crate) fn indices(&self) -> impl Iterator<Item = BorrowIndex> {
|
|
BorrowIndex::from_usize(0)..BorrowIndex::from_usize(self.len())
|
|
}
|
|
|
|
pub(crate) fn iter_enumerated(&self) -> impl Iterator<Item = (BorrowIndex, &BorrowData<'tcx>)> {
|
|
self.indices().zip(self.location_map.values())
|
|
}
|
|
|
|
pub(crate) fn get_index_of(&self, location: &Location) -> Option<BorrowIndex> {
|
|
self.location_map.get_index_of(location).map(BorrowIndex::from)
|
|
}
|
|
}
|
|
|
|
struct GatherBorrows<'a, 'tcx> {
|
|
tcx: TyCtxt<'tcx>,
|
|
body: &'a Body<'tcx>,
|
|
location_map: FxIndexMap<Location, BorrowData<'tcx>>,
|
|
activation_map: FxHashMap<Location, Vec<BorrowIndex>>,
|
|
local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
|
|
|
|
/// When we encounter a 2-phase borrow statement, it will always
|
|
/// be assigning into a temporary TEMP:
|
|
///
|
|
/// TEMP = &foo
|
|
///
|
|
/// We add TEMP into this map with `b`, where `b` is the index of
|
|
/// the borrow. When we find a later use of this activation, we
|
|
/// remove from the map (and add to the "tombstone" set below).
|
|
pending_activations: FxHashMap<mir::Local, BorrowIndex>,
|
|
|
|
locals_state_at_exit: LocalsStateAtExit,
|
|
}
|
|
|
|
impl<'a, 'tcx> Visitor<'tcx> for GatherBorrows<'a, 'tcx> {
|
|
fn visit_assign(
|
|
&mut self,
|
|
assigned_place: &mir::Place<'tcx>,
|
|
rvalue: &mir::Rvalue<'tcx>,
|
|
location: mir::Location,
|
|
) {
|
|
if let mir::Rvalue::Ref(region, kind, ref borrowed_place) = *rvalue {
|
|
if borrowed_place.ignore_borrow(self.tcx, self.body, &self.locals_state_at_exit) {
|
|
debug!("ignoring_borrow of {:?}", borrowed_place);
|
|
return;
|
|
}
|
|
|
|
let region = region.to_region_vid();
|
|
|
|
let borrow = BorrowData {
|
|
kind,
|
|
region,
|
|
reserve_location: location,
|
|
activation_location: TwoPhaseActivation::NotTwoPhase,
|
|
borrowed_place: *borrowed_place,
|
|
assigned_place: *assigned_place,
|
|
};
|
|
let (idx, _) = self.location_map.insert_full(location, borrow);
|
|
let idx = BorrowIndex::from(idx);
|
|
|
|
self.insert_as_pending_if_two_phase(location, assigned_place, kind, idx);
|
|
|
|
self.local_map.entry(borrowed_place.local).or_default().insert(idx);
|
|
}
|
|
|
|
self.super_assign(assigned_place, rvalue, location)
|
|
}
|
|
|
|
fn visit_local(&mut self, temp: &Local, context: PlaceContext, location: Location) {
|
|
if !context.is_use() {
|
|
return;
|
|
}
|
|
|
|
// We found a use of some temporary TMP
|
|
// check whether we (earlier) saw a 2-phase borrow like
|
|
//
|
|
// TMP = &mut place
|
|
if let Some(&borrow_index) = self.pending_activations.get(temp) {
|
|
let borrow_data = &mut self.location_map[borrow_index.as_usize()];
|
|
|
|
// Watch out: the use of TMP in the borrow itself
|
|
// doesn't count as an activation. =)
|
|
if borrow_data.reserve_location == location
|
|
&& context == PlaceContext::MutatingUse(MutatingUseContext::Store)
|
|
{
|
|
return;
|
|
}
|
|
|
|
if let TwoPhaseActivation::ActivatedAt(other_location) = borrow_data.activation_location
|
|
{
|
|
span_bug!(
|
|
self.body.source_info(location).span,
|
|
"found two uses for 2-phase borrow temporary {:?}: \
|
|
{:?} and {:?}",
|
|
temp,
|
|
location,
|
|
other_location,
|
|
);
|
|
}
|
|
|
|
// Otherwise, this is the unique later use that we expect.
|
|
// Double check: This borrow is indeed a two-phase borrow (that is,
|
|
// we are 'transitioning' from `NotActivated` to `ActivatedAt`) and
|
|
// we've not found any other activations (checked above).
|
|
assert_eq!(
|
|
borrow_data.activation_location,
|
|
TwoPhaseActivation::NotActivated,
|
|
"never found an activation for this borrow!",
|
|
);
|
|
self.activation_map.entry(location).or_default().push(borrow_index);
|
|
|
|
borrow_data.activation_location = TwoPhaseActivation::ActivatedAt(location);
|
|
}
|
|
}
|
|
|
|
fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: mir::Location) {
|
|
if let mir::Rvalue::Ref(region, kind, ref place) = *rvalue {
|
|
// double-check that we already registered a BorrowData for this
|
|
|
|
let borrow_data = &self.location_map[&location];
|
|
assert_eq!(borrow_data.reserve_location, location);
|
|
assert_eq!(borrow_data.kind, kind);
|
|
assert_eq!(borrow_data.region, region.to_region_vid());
|
|
assert_eq!(borrow_data.borrowed_place, *place);
|
|
}
|
|
|
|
self.super_rvalue(rvalue, location)
|
|
}
|
|
}
|
|
|
|
impl<'a, 'tcx> GatherBorrows<'a, 'tcx> {
|
|
/// If this is a two-phase borrow, then we will record it
|
|
/// as "pending" until we find the activating use.
|
|
fn insert_as_pending_if_two_phase(
|
|
&mut self,
|
|
start_location: Location,
|
|
assigned_place: &mir::Place<'tcx>,
|
|
kind: mir::BorrowKind,
|
|
borrow_index: BorrowIndex,
|
|
) {
|
|
debug!(
|
|
"Borrows::insert_as_pending_if_two_phase({:?}, {:?}, {:?})",
|
|
start_location, assigned_place, borrow_index,
|
|
);
|
|
|
|
if !allow_two_phase_borrow(kind) {
|
|
debug!(" -> {:?}", start_location);
|
|
return;
|
|
}
|
|
|
|
// When we encounter a 2-phase borrow statement, it will always
|
|
// be assigning into a temporary TEMP:
|
|
//
|
|
// TEMP = &foo
|
|
//
|
|
// so extract `temp`.
|
|
let Some(temp) = assigned_place.as_local() else {
|
|
span_bug!(
|
|
self.body.source_info(start_location).span,
|
|
"expected 2-phase borrow to assign to a local, not `{:?}`",
|
|
assigned_place,
|
|
);
|
|
};
|
|
|
|
// Consider the borrow not activated to start. When we find an activation, we'll update
|
|
// this field.
|
|
{
|
|
let borrow_data = &mut self.location_map[borrow_index.as_usize()];
|
|
borrow_data.activation_location = TwoPhaseActivation::NotActivated;
|
|
}
|
|
|
|
// Insert `temp` into the list of pending activations. From
|
|
// now on, we'll be on the lookout for a use of it. Note that
|
|
// we are guaranteed that this use will come after the
|
|
// assignment.
|
|
let old_value = self.pending_activations.insert(temp, borrow_index);
|
|
if let Some(old_index) = old_value {
|
|
span_bug!(
|
|
self.body.source_info(start_location).span,
|
|
"found already pending activation for temp: {:?} \
|
|
at borrow_index: {:?} with associated data {:?}",
|
|
temp,
|
|
old_index,
|
|
self.location_map[old_index.as_usize()]
|
|
);
|
|
}
|
|
}
|
|
}
|