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Auto merge of #46537 - pnkfelix:two-phase-borrows, r=arielb1

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[MIR-borrowck] Two phase borrows

This adds limited support for two-phase borrows as described in
  http://smallcultfollowing.com/babysteps/blog/2017/03/01/nested-method-calls-via-two-phase-borrowing/

The support is off by default; you opt into it via the flag `-Z two-phase-borrows`

I have written "*limited* support" above because there are simple variants of the simple `v.push(v.len())` example that one would think should work but currently do not, such as the one documented in the test compile-fail/borrowck/two-phase-reservation-sharing-interference-2.rs

(To be clear, that test is not describing something that is unsound. It is just providing an explicit example of a limitation in the implementation given in this PR. I have ideas on how to fix, but I want to land the work that is in this PR first, so that I can stop repeatedly rebasing this branch.)
This commit is contained in:
bors 2017-12-15 05:40:12 +00:00
commit 84feab34e4
25 changed files with 1183 additions and 256 deletions
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4
src/librustc/mir/mod.rs
View File

@ -1137,7 +1137,7 @@ impl<'tcx> Debug for Statement<'tcx> {
/// A path to a value; something that can be evaluated without
/// changing or disturbing program state.
#[derive(Clone, PartialEq, RustcEncodable, RustcDecodable)]
#[derive(Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
pub enum Place<'tcx> {
/// local variable
Local(Local),
@ -1151,7 +1151,7 @@ pub enum Place<'tcx> {
/// The def-id of a static, along with its normalized type (which is
/// stored to avoid requiring normalization when reading MIR).
#[derive(Clone, PartialEq, RustcEncodable, RustcDecodable)]
#[derive(Clone, PartialEq, Eq, Hash, RustcEncodable, RustcDecodable)]
pub struct Static<'tcx> {
pub def_id: DefId,
pub ty: Ty<'tcx>,

2
src/librustc/session/config.rs
View File

@ -1028,6 +1028,8 @@ options! {DebuggingOptions, DebuggingSetter, basic_debugging_options,
"emit EndRegion as part of MIR; enable transforms that solely process EndRegion"),
borrowck: Option<String> = (None, parse_opt_string, [UNTRACKED],
"select which borrowck is used (`ast`, `mir`, or `compare`)"),
two_phase_borrows: bool = (false, parse_bool, [UNTRACKED],
"use two-phase reserved/active distinction for `&mut` borrows in MIR borrowck"),
time_passes: bool = (false, parse_bool, [UNTRACKED],
"measure time of each rustc pass"),
count_llvm_insns: bool = (false, parse_bool,

20
src/librustc_data_structures/indexed_set.rs
View File

@ -8,6 +8,7 @@
// option. This file may not be copied, modified, or distributed
// except according to those terms.
use std::borrow::{Borrow, BorrowMut, ToOwned};
use std::fmt;
use std::iter;
use std::marker::PhantomData;
@ -73,6 +74,25 @@ pub struct IdxSet<T: Idx> {
bits: [Word],
}
impl<T: Idx> Borrow<IdxSet<T>> for IdxSetBuf<T> {
fn borrow(&self) -> &IdxSet<T> {
&*self
}
}
impl<T: Idx> BorrowMut<IdxSet<T>> for IdxSetBuf<T> {
fn borrow_mut(&mut self) -> &mut IdxSet<T> {
&mut *self
}
}
impl<T: Idx> ToOwned for IdxSet<T> {
type Owned = IdxSetBuf<T>;
fn to_owned(&self) -> Self::Owned {
IdxSet::to_owned(self)
}
}
impl<T: Idx> fmt::Debug for IdxSetBuf<T> {
fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
w.debug_list()

12
src/librustc_driver/pretty.rs
View File

@ -423,7 +423,8 @@ impl<'hir> pprust_hir::PpAnn for IdentifiedAnnotation<'hir> {
pprust_hir::NodeName(_) => Ok(()),
pprust_hir::NodeItem(item) => {
s.s.space()?;
s.synth_comment(item.id.to_string())
s.synth_comment(format!("node_id: {} hir local_id: {}",
item.id, item.hir_id.local_id.0))
}
pprust_hir::NodeSubItem(id) => {
s.s.space()?;
@ -431,16 +432,19 @@ impl<'hir> pprust_hir::PpAnn for IdentifiedAnnotation<'hir> {
}
pprust_hir::NodeBlock(blk) => {
s.s.space()?;
s.synth_comment(format!("block {}", blk.id))
s.synth_comment(format!("block node_id: {} hir local_id: {}",
blk.id, blk.hir_id.local_id.0))
}
pprust_hir::NodeExpr(expr) => {
s.s.space()?;
s.synth_comment(expr.id.to_string())?;
s.synth_comment(format!("node_id: {} hir local_id: {}",
expr.id, expr.hir_id.local_id.0))?;
s.pclose()
}
pprust_hir::NodePat(pat) => {
s.s.space()?;
s.synth_comment(format!("pat {}", pat.id))
s.synth_comment(format!("pat node_id: {} hir local_id: {}",
pat.id, pat.hir_id.local_id.0))
}
}
}

25
src/librustc_mir/borrow_check/error_reporting.rs
View File

@ -11,7 +11,7 @@
use syntax_pos::Span;
use rustc::middle::region::ScopeTree;
use rustc::mir::{BorrowKind, Field, Local, Location, Operand};
use rustc::mir::{Place, ProjectionElem, Rvalue, StatementKind};
use rustc::mir::{Place, ProjectionElem, Rvalue, Statement, StatementKind};
use rustc::ty::{self, RegionKind};
use rustc_data_structures::indexed_vec::Idx;
@ -19,7 +19,7 @@ use std::rc::Rc;
use super::{MirBorrowckCtxt, Context};
use super::{InitializationRequiringAction, PrefixSet};
use dataflow::{BorrowData, Borrows, FlowAtLocation, MovingOutStatements};
use dataflow::{ActiveBorrows, BorrowData, FlowAtLocation, MovingOutStatements};
use dataflow::move_paths::MovePathIndex;
use util::borrowck_errors::{BorrowckErrors, Origin};
@ -96,7 +96,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
Some(name) => format!("`{}`", name),
None => "value".to_owned(),
};
let borrow_msg = match self.describe_place(&borrow.place) {
let borrow_msg = match self.describe_place(&borrow.borrowed_place) {
Some(name) => format!("`{}`", name),
None => "value".to_owned(),
};
@ -124,7 +124,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
span,
&self.describe_place(place).unwrap_or("_".to_owned()),
self.retrieve_borrow_span(borrow),
&self.describe_place(&borrow.place).unwrap_or("_".to_owned()),
&self.describe_place(&borrow.borrowed_place).unwrap_or("_".to_owned()),
Origin::Mir,
);
@ -143,12 +143,9 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
use rustc::hir::ExprClosure;
use rustc::mir::AggregateKind;
let local = if let StatementKind::Assign(Place::Local(local), _) =
self.mir[location.block].statements[location.statement_index].kind
{
local
} else {
return None;
let local = match self.mir[location.block].statements.get(location.statement_index) {
Some(&Statement { kind: StatementKind::Assign(Place::Local(local), _), .. }) => local,
_ => return None,
};
for stmt in &self.mir[location.block].statements[location.statement_index + 1..] {
@ -324,11 +321,11 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
_: Context,
borrow: &BorrowData<'tcx>,
drop_span: Span,
borrows: &Borrows<'cx, 'gcx, 'tcx>
borrows: &ActiveBorrows<'cx, 'gcx, 'tcx>
) {
let end_span = borrows.opt_region_end_span(&borrow.region);
let scope_tree = borrows.scope_tree();
let root_place = self.prefixes(&borrow.place, PrefixSet::All).last().unwrap();
let scope_tree = borrows.0.scope_tree();
let root_place = self.prefixes(&borrow.borrowed_place, PrefixSet::All).last().unwrap();
match root_place {
&Place::Local(local) => {
@ -357,7 +354,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
_ => drop_span,
};
match (borrow.region, &self.describe_place(&borrow.place)) {
match (borrow.region, &self.describe_place(&borrow.borrowed_place)) {
(RegionKind::ReScope(_), Some(name)) => {
self.report_scoped_local_value_does_not_live_long_enough(
name, &scope_tree, &borrow, drop_span, borrow_span, proper_span, end_span);

12
src/librustc_mir/borrow_check/flows.rs
View File

@ -17,13 +17,13 @@ use rustc::mir::{BasicBlock, Location};
use dataflow::{MaybeInitializedLvals, MaybeUninitializedLvals};
use dataflow::{EverInitializedLvals, MovingOutStatements};
use dataflow::{Borrows, FlowAtLocation, FlowsAtLocation};
use dataflow::{ActiveBorrows, FlowAtLocation, FlowsAtLocation};
use dataflow::move_paths::HasMoveData;
use std::fmt;
// (forced to be `pub` due to its use as an associated type below.)
pub struct Flows<'b, 'gcx: 'tcx, 'tcx: 'b> {
pub borrows: FlowAtLocation<Borrows<'b, 'gcx, 'tcx>>,
pub(crate) struct Flows<'b, 'gcx: 'tcx, 'tcx: 'b> {
pub borrows: FlowAtLocation<ActiveBorrows<'b, 'gcx, 'tcx>>,
pub inits: FlowAtLocation<MaybeInitializedLvals<'b, 'gcx, 'tcx>>,
pub uninits: FlowAtLocation<MaybeUninitializedLvals<'b, 'gcx, 'tcx>>,
pub move_outs: FlowAtLocation<MovingOutStatements<'b, 'gcx, 'tcx>>,
@ -32,7 +32,7 @@ pub struct Flows<'b, 'gcx: 'tcx, 'tcx: 'b> {
impl<'b, 'gcx, 'tcx> Flows<'b, 'gcx, 'tcx> {
pub fn new(
borrows: FlowAtLocation<Borrows<'b, 'gcx, 'tcx>>,
borrows: FlowAtLocation<ActiveBorrows<'b, 'gcx, 'tcx>>,
inits: FlowAtLocation<MaybeInitializedLvals<'b, 'gcx, 'tcx>>,
uninits: FlowAtLocation<MaybeUninitializedLvals<'b, 'gcx, 'tcx>>,
move_outs: FlowAtLocation<MovingOutStatements<'b, 'gcx, 'tcx>>,
@ -87,7 +87,7 @@ impl<'b, 'gcx, 'tcx> fmt::Display for Flows<'b, 'gcx, 'tcx> {
s.push_str(", ");
};
saw_one = true;
let borrow_data = &self.borrows.operator().borrows()[borrow];
let borrow_data = &self.borrows.operator().borrows()[borrow.borrow_index()];
s.push_str(&format!("{}", borrow_data));
});
s.push_str("] ");
@ -99,7 +99,7 @@ impl<'b, 'gcx, 'tcx> fmt::Display for Flows<'b, 'gcx, 'tcx> {
s.push_str(", ");
};
saw_one = true;
let borrow_data = &self.borrows.operator().borrows()[borrow];
let borrow_data = &self.borrows.operator().borrows()[borrow.borrow_index()];
s.push_str(&format!("{}", borrow_data));
});
s.push_str("] ");

244
src/librustc_mir/borrow_check/mod.rs
View File

@ -28,13 +28,15 @@ use rustc_data_structures::indexed_vec::Idx;
use syntax::ast;
use syntax_pos::Span;
use dataflow::do_dataflow;
use dataflow::{do_dataflow, DebugFormatted};
use dataflow::MoveDataParamEnv;
use dataflow::DataflowResultsConsumer;
use dataflow::{DataflowAnalysis, DataflowResultsConsumer};
use dataflow::{FlowAtLocation, FlowsAtLocation};
use dataflow::{MaybeInitializedLvals, MaybeUninitializedLvals};
use dataflow::{EverInitializedLvals, MovingOutStatements};
use dataflow::{BorrowData, BorrowIndex, Borrows};
use dataflow::{Borrows, BorrowData, ReserveOrActivateIndex};
use dataflow::{ActiveBorrows, Reservations};
use dataflow::indexes::{BorrowIndex};
use dataflow::move_paths::{IllegalMoveOriginKind, MoveError};
use dataflow::move_paths::{HasMoveData, LookupResult, MoveData, MovePathIndex};
use util::borrowck_errors::{BorrowckErrors, Origin};
@ -48,6 +50,9 @@ use self::MutateMode::{JustWrite, WriteAndRead};
mod error_reporting;
mod flows;
mod prefixes;
use std::borrow::Cow;
pub(crate) mod nll;
pub fn provide(providers: &mut Providers) {
@ -157,7 +162,7 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
&attributes,
&dead_unwinds,
MaybeInitializedLvals::new(tcx, mir, &mdpe),
|bd, i| &bd.move_data().move_paths[i],
|bd, i| DebugFormatted::new(&bd.move_data().move_paths[i]),
));
let flow_uninits = FlowAtLocation::new(do_dataflow(
tcx,
@ -166,7 +171,7 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
&attributes,
&dead_unwinds,
MaybeUninitializedLvals::new(tcx, mir, &mdpe),
|bd, i| &bd.move_data().move_paths[i],
|bd, i| DebugFormatted::new(&bd.move_data().move_paths[i]),
));
let flow_move_outs = FlowAtLocation::new(do_dataflow(
tcx,
@ -175,7 +180,7 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
&attributes,
&dead_unwinds,
MovingOutStatements::new(tcx, mir, &mdpe),
|bd, i| &bd.move_data().moves[i],
|bd, i| DebugFormatted::new(&bd.move_data().moves[i]),
));
let flow_ever_inits = FlowAtLocation::new(do_dataflow(
tcx,
@ -184,7 +189,7 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
&attributes,
&dead_unwinds,
EverInitializedLvals::new(tcx, mir, &mdpe),
|bd, i| &bd.move_data().inits[i],
|bd, i| DebugFormatted::new(&bd.move_data().inits[i]),
));
// If we are in non-lexical mode, compute the non-lexical lifetimes.
@ -205,23 +210,6 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
};
let flow_inits = flow_inits; // remove mut
let flow_borrows = FlowAtLocation::new(do_dataflow(
tcx,
mir,
id,
&attributes,
&dead_unwinds,
Borrows::new(tcx, mir, opt_regioncx, def_id, body_id),
|bd, i| bd.location(i),
));
let mut state = Flows::new(
flow_borrows,
flow_inits,
flow_uninits,
flow_move_outs,
flow_ever_inits,
);
let mut mbcx = MirBorrowckCtxt {
tcx: tcx,
mir: mir,
@ -235,8 +223,47 @@ fn do_mir_borrowck<'a, 'gcx, 'tcx>(
},
storage_dead_or_drop_error_reported_l: FxHashSet(),
storage_dead_or_drop_error_reported_s: FxHashSet(),
reservation_error_reported: FxHashSet(),
};
let borrows = Borrows::new(tcx, mir, opt_regioncx, def_id, body_id);
let flow_reservations = do_dataflow(
tcx,
mir,
id,
&attributes,
&dead_unwinds,
Reservations::new(borrows),
|rs, i| {
// In principle we could make the dataflow ensure that
// only reservation bits show up, and assert so here.
//
// In practice it is easier to be looser; in particular,
// it is okay for the kill-sets to hold activation bits.
DebugFormatted::new(&(i.kind(), rs.location(i)))
});
let flow_active_borrows = {
let reservations_on_entry = flow_reservations.0.sets.entry_set_state();
let reservations = flow_reservations.0.operator;
let a = DataflowAnalysis::new_with_entry_sets(mir,
&dead_unwinds,
Cow::Borrowed(reservations_on_entry),
ActiveBorrows::new(reservations));
let results = a.run(tcx,
id,
&attributes,
|ab, i| DebugFormatted::new(&(i.kind(), ab.location(i))));
FlowAtLocation::new(results)
};
let mut state = Flows::new(
flow_active_borrows,
flow_inits,
flow_uninits,
flow_move_outs,
flow_ever_inits,
);
mbcx.analyze_results(&mut state); // entry point for DataflowResultsConsumer
opt_closure_req
@ -262,6 +289,14 @@ pub struct MirBorrowckCtxt<'cx, 'gcx: 'tcx, 'tcx: 'cx> {
storage_dead_or_drop_error_reported_l: FxHashSet<Local>,
/// Same as the above, but for statics (thread-locals)
storage_dead_or_drop_error_reported_s: FxHashSet<DefId>,
/// This field keeps track of when borrow conflict errors are reported
/// for reservations, so that we don't report seemingly duplicate
/// errors for corresponding activations
///
/// FIXME: Ideally this would be a set of BorrowIndex, not Places,
/// but it is currently inconvenient to track down the BorrowIndex
/// at the time we detect and report a reservation error.
reservation_error_reported: FxHashSet<Place<'tcx>>,
}
// Check that:
@ -293,6 +328,9 @@ impl<'cx, 'gcx, 'tcx> DataflowResultsConsumer<'cx, 'tcx> for MirBorrowckCtxt<'cx
flow_state
);
let span = stmt.source_info.span;
self.check_activations(location, span, flow_state);
match stmt.kind {
StatementKind::Assign(ref lhs, ref rhs) => {
// NOTE: NLL RFC calls for *shallow* write; using Deep
@ -399,6 +437,9 @@ impl<'cx, 'gcx, 'tcx> DataflowResultsConsumer<'cx, 'tcx> for MirBorrowckCtxt<'cx
flow_state
);
let span = term.source_info.span;
self.check_activations(location, span, flow_state);
match term.kind {
TerminatorKind::SwitchInt {
ref discr,
@ -504,9 +545,8 @@ impl<'cx, 'gcx, 'tcx> DataflowResultsConsumer<'cx, 'tcx> for MirBorrowckCtxt<'cx
let data = domain.borrows();
flow_state.borrows.with_elems_outgoing(|borrows| {
for i in borrows {
let borrow = &data[i];
let borrow = &data[i.borrow_index()];
let context = ContextKind::StorageDead.new(loc);
self.check_for_invalidation_at_exit(context, borrow, span, flow_state);
}
});
@ -533,7 +573,7 @@ enum Control {
}
use self::ShallowOrDeep::{Deep, Shallow};
use self::ReadOrWrite::{Read, Write};
use self::ReadOrWrite::{Activation, Read, Reservation, Write};
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
enum ArtificialField {
@ -568,6 +608,12 @@ enum ReadOrWrite {
/// new values or otherwise invalidated (for example, it could be
/// de-initialized, as in a move operation).
Write(WriteKind),
/// For two-phase borrows, we distinguish a reservation (which is treated
/// like a Read) from an activation (which is treated like a write), and
/// each of those is furthermore distinguished from Reads/Writes above.
Reservation(WriteKind),
Activation(WriteKind, BorrowIndex),
}
/// Kind of read access to a value
@ -656,6 +702,14 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
) -> AccessErrorsReported {
let (sd, rw) = kind;
if let Activation(_, borrow_index) = rw {
if self.reservation_error_reported.contains(&place_span.0) {
debug!("skipping access_place for activation of invalid reservation \
place: {:?} borrow_index: {:?}", place_span.0, borrow_index);
return AccessErrorsReported { mutability_error: false, conflict_error: true };
}
}
let mutability_error =
self.check_access_permissions(place_span, rw, is_local_mutation_allowed);
let conflict_error =
@ -677,9 +731,33 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
context,
(sd, place_span.0),
flow_state,
|this, _index, borrow| match (rw, borrow.kind) {
(Read(_), BorrowKind::Shared) => Control::Continue,
(Read(kind), BorrowKind::Unique) | (Read(kind), BorrowKind::Mut) => {
|this, 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 unsoundenss w/ this check.)
(Activation(_, activating), _) if activating == index.borrow_index() =>
{
debug!("check_access_for_conflict place_span: {:?} sd: {:?} rw: {:?} \
skipping {:?} b/c activation of same borrow_index: {:?}",
place_span, sd, rw, (index, borrow), index.borrow_index());
Control::Continue
}
(Read(_), BorrowKind::Shared) |
(Reservation(..), BorrowKind::Shared) => Control::Continue,
(Read(kind), BorrowKind::Unique) |
(Read(kind), BorrowKind::Mut) => {
// Reading from mere reservations of mutable-borrows is OK.
if this.tcx.sess.opts.debugging_opts.two_phase_borrows &&
index.is_reservation()
{
return Control::Continue;
}
match kind {
ReadKind::Copy => {
error_reported = true;
@ -702,13 +780,32 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
}
Control::Break
}
(Reservation(kind), BorrowKind::Unique) |
(Reservation(kind), BorrowKind::Mut) |
(Activation(kind, _), _) |
(Write(kind), _) => {
match rw {
Reservation(_) => {
debug!("recording invalid reservation of \
place: {:?}", place_span.0);
this.reservation_error_reported.insert(place_span.0.clone());
}
Activation(_, activating) => {
debug!("observing check_place for activation of \
borrow_index: {:?}", activating);
}
Read(..) | Write(..) => {}
}
match kind {
WriteKind::MutableBorrow(bk) => {
let end_issued_loan_span = flow_state
.borrows
.operator()
.opt_region_end_span(&borrow.region);
error_reported = true;
this.report_conflicting_borrow(
context,
@ -721,7 +818,8 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
WriteKind::StorageDeadOrDrop => {
error_reported = true;
this.report_borrowed_value_does_not_live_long_enough(
context, borrow, place_span.1, flow_state.borrows.operator());
context, borrow, place_span.1,
flow_state.borrows.operator());
}
WriteKind::Mutate => {
error_reported = true;
@ -794,9 +892,15 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
let access_kind = match bk {
BorrowKind::Shared => (Deep, Read(ReadKind::Borrow(bk))),
BorrowKind::Unique | BorrowKind::Mut => {
(Deep, Write(WriteKind::MutableBorrow(bk)))
let wk = WriteKind::MutableBorrow(bk);
if self.tcx.sess.opts.debugging_opts.two_phase_borrows {
(Deep, Reservation(wk))
} else {
(Deep, Write(wk))
}
}
};
self.access_place(
context,
(place, span),
@ -804,6 +908,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
LocalMutationIsAllowed::No,
flow_state,
);
self.check_if_path_is_moved(
context,
InitializationRequiringAction::Borrow,
@ -917,7 +1022,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
flow_state: &Flows<'cx, 'gcx, 'tcx>)
{
debug!("check_for_invalidation_at_exit({:?})", borrow);
let place = &borrow.place;
let place = &borrow.borrowed_place;
let root_place = self.prefixes(place, PrefixSet::All).last().unwrap();
// FIXME(nll-rfc#40): do more precise destructor tracking here. For now
@ -974,6 +1079,48 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
)
}
}
fn check_activations(&mut self,
location: Location,
span: Span,
flow_state: &Flows<'cx, 'gcx, 'tcx>)
{
if !self.tcx.sess.opts.debugging_opts.two_phase_borrows {
return;
}
// Two-phase borrow support: For each activation that is newly
// generated at this statement, check if it interferes with
// another borrow.
let domain = flow_state.borrows.operator();
let data = domain.borrows();
flow_state.borrows.each_gen_bit(|gen| {
if gen.is_activation()
{
let borrow_index = gen.borrow_index();
let borrow = &data[borrow_index];
// currently the flow analysis registers
// activations for both mutable and immutable
// borrows. So make sure we are talking about a
// mutable borrow before we check it.
match borrow.kind {
BorrowKind::Shared => return,
BorrowKind::Unique |
BorrowKind::Mut => {}
}
self.access_place(ContextKind::Activation.new(location),
(&borrow.borrowed_place, span),
(Deep, Activation(WriteKind::MutableBorrow(borrow.kind),
borrow_index)),
LocalMutationIsAllowed::No,
flow_state);
// We do not need to call `check_if_path_is_moved`
// again, as we already called it when we made the
// initial reservation.
}
});
}
}
impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
@ -1217,11 +1364,13 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
);
let mut error_reported = false;
match kind {
Reservation(WriteKind::MutableBorrow(BorrowKind::Unique)) |
Write(WriteKind::MutableBorrow(BorrowKind::Unique)) => {
if let Err(_place_err) = self.is_mutable(place, LocalMutationIsAllowed::Yes) {
span_bug!(span, "&unique borrow for {:?} should not fail", place);
}
}
Reservation(WriteKind::MutableBorrow(BorrowKind::Mut)) |
Write(WriteKind::MutableBorrow(BorrowKind::Mut)) => if let Err(place_err) =
self.is_mutable(place, is_local_mutation_allowed)
{
@ -1244,6 +1393,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
err.emit();
},
Reservation(WriteKind::Mutate) |
Write(WriteKind::Mutate) => {
if let Err(place_err) = self.is_mutable(place, is_local_mutation_allowed) {
error_reported = true;
@ -1265,6 +1415,9 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
err.emit();
}
}
Reservation(WriteKind::Move) |
Reservation(WriteKind::StorageDeadOrDrop) |
Reservation(WriteKind::MutableBorrow(BorrowKind::Shared)) |
Write(WriteKind::Move) |
Write(WriteKind::StorageDeadOrDrop) |
Write(WriteKind::MutableBorrow(BorrowKind::Shared)) => {
@ -1279,6 +1432,9 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
);
}
}
Activation(..) => {} // permission checks are done at Reservation point.
Read(ReadKind::Borrow(BorrowKind::Unique)) |
Read(ReadKind::Borrow(BorrowKind::Mut)) |
Read(ReadKind::Borrow(BorrowKind::Shared)) |
@ -1771,6 +1927,18 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
unreachable!("iter::repeat returned None")
}
/// This function iterates over all of the current borrows
/// (represented by 1-bits in `flow_state.borrows`) that conflict
/// with an access to a place, invoking the `op` callback for each
/// one.
///
/// "Current borrow" here means a borrow that reaches the point in
/// the control-flow where the access occurs.
///
/// The borrow's phase is represented by the ReserveOrActivateIndex
/// passed to the callback: one can call `is_reservation()` and
/// `is_activation()` to determine what phase the borrow is
/// currently in, when such distinction matters.
fn each_borrow_involving_path<F>(
&mut self,
_context: Context,
@ -1778,7 +1946,7 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
flow_state: &Flows<'cx, 'gcx, 'tcx>,
mut op: F,
) where
F: FnMut(&mut Self, BorrowIndex, &BorrowData<'tcx>) -> Control,
F: FnMut(&mut Self, ReserveOrActivateIndex, &BorrowData<'tcx>) -> Control,
{
let (access, place) = access_place;
@ -1789,10 +1957,11 @@ impl<'cx, 'gcx, 'tcx> MirBorrowckCtxt<'cx, 'gcx, 'tcx> {
// check for loan restricting path P being used. Accounts for
// borrows of P, P.a.b, etc.
for i in flow_state.borrows.elems_incoming() {
let borrowed = &data[i];
let mut elems_incoming = flow_state.borrows.elems_incoming();
while let Some(i) = elems_incoming.next() {
let borrowed = &data[i.borrow_index()];
if self.places_conflict(&borrowed.place, place, access) {
if self.places_conflict(&borrowed.borrowed_place, place, access) {
let ctrl = op(self, i, borrowed);
if ctrl == Control::Break { return; }
}
@ -1836,6 +2005,7 @@ struct Context {
#[derive(Copy, Clone, PartialEq, Eq, Debug)]
enum ContextKind {
Activation,
AssignLhs,
AssignRhs,
SetDiscrim,

12
src/librustc_mir/dataflow/at_location.rs
View File

@ -18,6 +18,8 @@ use rustc_data_structures::indexed_vec::Idx;
use dataflow::{BitDenotation, BlockSets, DataflowResults};
use dataflow::move_paths::{HasMoveData, MovePathIndex};
use std::iter;
/// A trait for "cartesian products" of multiple FlowAtLocation.
///
/// There's probably a way to auto-impl this, but I think
@ -94,9 +96,9 @@ where
self.curr_state.contains(x)
}
pub fn elems_incoming(&self) -> indexed_set::Elems<BD::Idx> {
pub fn elems_incoming(&self) -> iter::Peekable<indexed_set::Elems<BD::Idx>> {
let univ = self.base_results.sets().bits_per_block();
self.curr_state.elems(univ)
self.curr_state.elems(univ).peekable()
}
pub fn with_elems_outgoing<F>(&self, f: F)
@ -121,9 +123,8 @@ impl<BD> FlowsAtLocation for FlowAtLocation<BD>
fn reconstruct_statement_effect(&mut self, loc: Location) {
self.stmt_gen.reset_to_empty();
self.stmt_kill.reset_to_empty();
let mut ignored = IdxSetBuf::new_empty(0);
let mut sets = BlockSets {
on_entry: &mut ignored,
on_entry: &mut self.curr_state,
gen_set: &mut self.stmt_gen,
kill_set: &mut self.stmt_kill,
};
@ -135,9 +136,8 @@ impl<BD> FlowsAtLocation for FlowAtLocation<BD>
fn reconstruct_terminator_effect(&mut self, loc: Location) {
self.stmt_gen.reset_to_empty();
self.stmt_kill.reset_to_empty();
let mut ignored = IdxSetBuf::new_empty(0);
let mut sets = BlockSets {
on_entry: &mut ignored,
on_entry: &mut self.curr_state,
gen_set: &mut self.stmt_gen,
kill_set: &mut self.stmt_kill,
};

10
src/librustc_mir/dataflow/graphviz.rs
View File

@ -18,7 +18,6 @@ use rustc_data_structures::indexed_vec::Idx;
use dot;
use dot::IntoCow;
use std::fmt::Debug;
use std::fs::File;
use std::io;
use std::io::prelude::*;
@ -29,6 +28,7 @@ use util;
use super::{BitDenotation, DataflowState};
use super::DataflowBuilder;
use super::DebugFormatted;
pub trait MirWithFlowState<'tcx> {
type BD: BitDenotation;
@ -60,9 +60,9 @@ pub(crate) fn print_borrowck_graph_to<'a, 'tcx, BD, P>(
render_idx: P)
-> io::Result<()>
where BD: BitDenotation,
P: Fn(&BD, BD::Idx) -> &Debug
P: Fn(&BD, BD::Idx) -> DebugFormatted
{
let g = Graph { mbcx: mbcx, phantom: PhantomData, render_idx: render_idx };
let g = Graph { mbcx, phantom: PhantomData, render_idx };
let mut v = Vec::new();
dot::render(&g, &mut v)?;
debug!("print_borrowck_graph_to path: {} node_id: {}",
@ -82,7 +82,7 @@ fn outgoing(mir: &Mir, bb: BasicBlock) -> Vec<Edge> {
impl<'a, 'tcx, MWF, P> dot::Labeller<'a> for Graph<'a, 'tcx, MWF, P>
where MWF: MirWithFlowState<'tcx>,
P: for <'b> Fn(&'b MWF::BD, <MWF::BD as BitDenotation>::Idx) -> &'b Debug,
P: Fn(&MWF::BD, <MWF::BD as BitDenotation>::Idx) -> DebugFormatted,
{
type Node = Node;
type Edge = Edge;
@ -142,7 +142,7 @@ impl<'a, 'tcx, MWF, P> dot::Labeller<'a> for Graph<'a, 'tcx, MWF, P>
const ALIGN_RIGHT: &'static str = r#"align="right""#;
const FACE_MONOSPACE: &'static str = r#"FACE="Courier""#;
fn chunked_present_left<W:io::Write>(w: &mut W,
interpreted: &[&Debug],
interpreted: &[DebugFormatted],
chunk_size: usize)
-> io::Result<()>
{

517
src/librustc_mir/dataflow/impls/borrows.rs
View File

@ -11,8 +11,8 @@
use rustc::hir;
use rustc::hir::def_id::DefId;
use rustc::middle::region;
use rustc::mir::{self, Location, Mir};
use rustc::mir::visit::Visitor;
use rustc::mir::{self, Location, Place, Mir};
use rustc::mir::visit::{PlaceContext, Visitor};
use rustc::ty::{self, Region, TyCtxt};
use rustc::ty::RegionKind;
use rustc::ty::RegionKind::ReScope;
@ -20,36 +20,91 @@ use rustc::util::nodemap::{FxHashMap, FxHashSet};
use rustc_data_structures::bitslice::{BitwiseOperator};
use rustc_data_structures::indexed_set::{IdxSet};
use rustc_data_structures::indexed_vec::{IndexVec};
use rustc_data_structures::indexed_vec::{Idx, IndexVec};
use dataflow::{BitDenotation, BlockSets, DataflowOperator};
pub use dataflow::indexes::BorrowIndex;
use dataflow::{BitDenotation, BlockSets, InitialFlow};
pub use dataflow::indexes::{BorrowIndex, ReserveOrActivateIndex};
use borrow_check::nll::region_infer::RegionInferenceContext;
use borrow_check::nll::ToRegionVid;
use syntax_pos::Span;
use std::fmt;
use std::hash::Hash;
use std::rc::Rc;
// `Borrows` maps each dataflow bit to an `Rvalue::Ref`, which can be
// uniquely identified in the MIR by the `Location` of the assigment
// statement in which it appears on the right hand side.
/// `Borrows` stores the data used in the analyses that track the flow
/// of borrows.
///
/// It uniquely identifies every borrow (`Rvalue::Ref`) by a
/// `BorrowIndex`, and maps each such index to a `BorrowData`
/// describing the borrow. These indexes are used for representing the
/// borrows in compact bitvectors.
pub struct Borrows<'a, 'gcx: 'tcx, 'tcx: 'a> {
tcx: TyCtxt<'a, 'gcx, 'tcx>,
mir: &'a Mir<'tcx>,
scope_tree: Rc<region::ScopeTree>,
root_scope: Option<region::Scope>,
/// The fundamental map relating bitvector indexes to the borrows
/// in the MIR.
borrows: IndexVec<BorrowIndex, BorrowData<'tcx>>,
/// 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; we map each such location to the
/// corresponding `BorrowIndex`.
location_map: FxHashMap<Location, BorrowIndex>,
/// Every borrow in MIR is immediately stored into a place via an
/// assignment statement. This maps each such assigned place back
/// to its borrow-indexes.
assigned_map: FxHashMap<Place<'tcx>, FxHashSet<BorrowIndex>>,
/// Every borrow has a region; this maps each such regions back to
/// its borrow-indexes.
region_map: FxHashMap<Region<'tcx>, FxHashSet<BorrowIndex>>,
local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
region_span_map: FxHashMap<RegionKind, Span>,
nonlexical_regioncx: Option<RegionInferenceContext<'tcx>>,
}
// Two-phase borrows actually requires two flow analyses; they need
// to be separate because the final results of the first are used to
// construct the gen+kill sets for the second. (The dataflow system
// is not designed to allow the gen/kill sets to change during the
// fixed-point iteration.)
/// The `Reservations` analysis is the first of the two flow analyses
/// tracking (phased) borrows. It computes where a borrow is reserved;
/// i.e. where it can reach in the control flow starting from its
/// initial `assigned = &'rgn borrowed` statement, and ending
/// whereever `'rgn` itself ends.
pub(crate) struct Reservations<'a, 'gcx: 'tcx, 'tcx: 'a>(pub(crate) Borrows<'a, 'gcx, 'tcx>);
/// The `ActiveBorrows` analysis is the second of the two flow
/// analyses tracking (phased) borrows. It computes where any given
/// borrow `&assigned = &'rgn borrowed` is *active*, which starts at
/// the first use of `assigned` after the reservation has started, and
/// ends whereever `'rgn` itself ends.
pub(crate) struct ActiveBorrows<'a, 'gcx: 'tcx, 'tcx: 'a>(pub(crate) Borrows<'a, 'gcx, 'tcx>);
impl<'a, 'gcx, 'tcx> Reservations<'a, 'gcx, 'tcx> {
pub(crate) fn new(b: Borrows<'a, 'gcx, 'tcx>) -> Self { Reservations(b) }
pub(crate) fn location(&self, idx: ReserveOrActivateIndex) -> &Location {
self.0.location(idx.borrow_index())
}
}
impl<'a, 'gcx, 'tcx> ActiveBorrows<'a, 'gcx, 'tcx> {
pub(crate) fn new(r: Reservations<'a, 'gcx, 'tcx>) -> Self { ActiveBorrows(r.0) }
pub(crate) fn location(&self, idx: ReserveOrActivateIndex) -> &Location {
self.0.location(idx.borrow_index())
}
}
// temporarily allow some dead fields: `kind` and `region` will be
// needed by borrowck; `place` will probably be a MovePathIndex when
// needed by borrowck; `borrowed_place` will probably be a MovePathIndex when
// that is extended to include borrowed data paths.
#[allow(dead_code)]
#[derive(Debug)]
@ -57,7 +112,8 @@ pub struct BorrowData<'tcx> {
pub(crate) location: Location,
pub(crate) kind: mir::BorrowKind,
pub(crate) region: Region<'tcx>,
pub(crate) place: mir::Place<'tcx>,
pub(crate) borrowed_place: mir::Place<'tcx>,
pub(crate) assigned_place: mir::Place<'tcx>,
}
impl<'tcx> fmt::Display for BorrowData<'tcx> {
@ -69,7 +125,22 @@ impl<'tcx> fmt::Display for BorrowData<'tcx> {
};
let region = format!("{}", self.region);
let region = if region.len() > 0 { format!("{} ", region) } else { region };
write!(w, "&{}{}{:?}", region, kind, self.place)
write!(w, "&{}{}{:?}", region, kind, self.borrowed_place)
}
}
impl ReserveOrActivateIndex {
fn reserved(i: BorrowIndex) -> Self { ReserveOrActivateIndex::new((i.index() * 2)) }
fn active(i: BorrowIndex) -> Self { ReserveOrActivateIndex::new((i.index() * 2) + 1) }
pub(crate) fn is_reservation(self) -> bool { self.index() % 2 == 0 }
pub(crate) fn is_activation(self) -> bool { self.index() % 2 == 1}
pub(crate) fn kind(self) -> &'static str {
if self.is_reservation() { "reserved" } else { "active" }
}
pub(crate) fn borrow_index(self) -> BorrowIndex {
BorrowIndex::new(self.index() / 2)
}
}
@ -89,6 +160,7 @@ impl<'a, 'gcx, 'tcx> Borrows<'a, 'gcx, 'tcx> {
mir,
idx_vec: IndexVec::new(),
location_map: FxHashMap(),
assigned_map: FxHashMap(),
region_map: FxHashMap(),
local_map: FxHashMap(),
region_span_map: FxHashMap()
@ -100,6 +172,7 @@ impl<'a, 'gcx, 'tcx> Borrows<'a, 'gcx, 'tcx> {
scope_tree,
root_scope,
location_map: visitor.location_map,
assigned_map: visitor.assigned_map,
region_map: visitor.region_map,
local_map: visitor.local_map,
region_span_map: visitor.region_span_map,
@ -110,13 +183,16 @@ impl<'a, 'gcx, 'tcx> Borrows<'a, 'gcx, 'tcx> {
mir: &'a Mir<'tcx>,
idx_vec: IndexVec<BorrowIndex, BorrowData<'tcx>>,
location_map: FxHashMap<Location, BorrowIndex>,
assigned_map: FxHashMap<Place<'tcx>, FxHashSet<BorrowIndex>>,
region_map: FxHashMap<Region<'tcx>, FxHashSet<BorrowIndex>>,
local_map: FxHashMap<mir::Local, FxHashSet<BorrowIndex>>,
region_span_map: FxHashMap<RegionKind, Span>,
}
impl<'a, 'gcx, 'tcx> Visitor<'tcx> for GatherBorrows<'a, 'gcx, 'tcx> {
fn visit_rvalue(&mut self,
fn visit_assign(&mut self,
block: mir::BasicBlock,
assigned_place: &mir::Place<'tcx>,
rvalue: &mir::Rvalue<'tcx>,
location: mir::Location) {
fn root_local(mut p: &mir::Place<'_>) -> Option<mir::Local> {
@ -127,23 +203,59 @@ impl<'a, 'gcx, 'tcx> Borrows<'a, 'gcx, 'tcx> {
}}
}
if let mir::Rvalue::Ref(region, kind, ref place) = *rvalue {
if is_unsafe_place(self.tcx, self.mir, place) { return; }
if let mir::Rvalue::Ref(region, kind, ref borrowed_place) = *rvalue {
if is_unsafe_place(self.tcx, self.mir, borrowed_place) { return; }
let borrow = BorrowData {
location: location, kind: kind, region: region, place: place.clone(),
location, kind, region,
borrowed_place: borrowed_place.clone(),
assigned_place: assigned_place.clone(),
};
let idx = self.idx_vec.push(borrow);
self.location_map.insert(location, idx);
let borrows = self.region_map.entry(region).or_insert(FxHashSet());
borrows.insert(idx);
if let Some(local) = root_local(place) {
let borrows = self.local_map.entry(local).or_insert(FxHashSet());
borrows.insert(idx);
insert(&mut self.assigned_map, assigned_place, idx);
insert(&mut self.region_map, &region, idx);
if let Some(local) = root_local(borrowed_place) {
insert(&mut self.local_map, &local, idx);
}
}
return self.super_assign(block, assigned_place, rvalue, location);
fn insert<'a, K, V>(map: &'a mut FxHashMap<K, FxHashSet<V>>,
k: &K,
v: V)
where K: Clone+Eq+Hash, V: Eq+Hash
{
map.entry(k.clone())
.or_insert(FxHashSet())
.insert(v);
}
}
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 mut found_it = false;
for idx in &self.region_map[region] {
let bd = &self.idx_vec[*idx];
if bd.location == location &&
bd.kind == kind &&
bd.region == region &&
bd.borrowed_place == *place
{
found_it = true;
break;
}
}
assert!(found_it, "Ref {:?} at {:?} missing BorrowData", rvalue, location);
}
return self.super_rvalue(rvalue, location);
}
fn visit_statement(&mut self,
@ -153,7 +265,7 @@ impl<'a, 'gcx, 'tcx> Borrows<'a, 'gcx, 'tcx> {
if let mir::StatementKind::EndRegion(region_scope) = statement.kind {
self.region_span_map.insert(ReScope(region_scope), statement.source_info.span);
}
self.super_statement(block, statement, location);
return self.super_statement(block, statement, location);
}
}
}
@ -166,80 +278,95 @@ impl<'a, 'gcx, 'tcx> Borrows<'a, 'gcx, 'tcx> {
&self.borrows[idx].location
}
/// Returns the span for the "end point" given region. This will
/// return `None` if NLL is enabled, since that concept has no
/// meaning there. Otherwise, return region span if it exists and
/// span for end of the function if it doesn't exist.
pub fn opt_region_end_span(&self, region: &Region) -> Option<Span> {
match self.nonlexical_regioncx {
Some(_) => None,
None => {
match self.region_span_map.get(region) {
Some(span) => Some(span.end_point()),
None => Some(self.mir.span.end_point())
}
}
}
}
/// Add all borrows to the kill set, if those borrows are out of scope at `location`.
///
/// `is_activations` tracks whether we are in the Reservations or
/// the ActiveBorrows flow analysis, and does not set the
/// activation kill bits in the former case. (Technically, we
/// could set those kill bits without such a guard, since they are
/// never gen'ed by Reservations in the first place. But it makes
/// the instrumentation and graph renderings nicer to leave
/// activations out when of the Reservations kill sets.)
fn kill_loans_out_of_scope_at_location(&self,
sets: &mut BlockSets<BorrowIndex>,
location: Location) {
sets: &mut BlockSets<ReserveOrActivateIndex>,
location: Location,
is_activations: bool) {
if let Some(ref regioncx) = self.nonlexical_regioncx {
// NOTE: The state associated with a given `location`
// reflects the dataflow on entry to the statement. If it
// does not contain `borrow_region`, then then that means
// that the statement at `location` kills the borrow.
//
// We are careful always to call this function *before* we
// set up the gen-bits for the statement or
// termanator. That way, if the effect of the statement or
// terminator *does* introduce a new loan of the same
// region, then setting that gen-bit will override any
// potential kill introduced here.
for (borrow_index, borrow_data) in self.borrows.iter_enumerated() {
let borrow_region = borrow_data.region.to_region_vid();
if !regioncx.region_contains_point(borrow_region, location) {
// The region checker really considers the borrow
// to start at the point **after** the location of
// the borrow, but the borrow checker puts the gen
// directly **on** the location of the
// borrow. This results in a gen/kill both being
// generated for same point if we are not
// careful. Probably we should change the point of
// the gen, but for now we hackily account for the
// mismatch here by not generating a kill for the
// location on the borrow itself.
if location != borrow_data.location {
sets.kill(&borrow_index);
sets.kill(&ReserveOrActivateIndex::reserved(borrow_index));
if is_activations {
sets.kill(&ReserveOrActivateIndex::active(borrow_index));
}
}
}
}
}
}
impl<'a, 'gcx, 'tcx> BitDenotation for Borrows<'a, 'gcx, 'tcx> {
type Idx = BorrowIndex;
fn name() -> &'static str { "borrows" }
fn bits_per_block(&self) -> usize {
self.borrows.len()
}
fn start_block_effect(&self, _sets: &mut IdxSet<BorrowIndex>) {
// no borrows of code region_scopes have been taken prior to
// function execution, so this method has no effect on
// `_sets`.
}
fn statement_effect(&self,
sets: &mut BlockSets<BorrowIndex>,
location: Location) {
/// Models statement effect in Reservations and ActiveBorrows flow
/// analyses; `is activations` tells us if we are in the latter
/// case.
fn statement_effect_on_borrows(&self,
sets: &mut BlockSets<ReserveOrActivateIndex>,
location: Location,
is_activations: bool) {
let block = &self.mir.basic_blocks().get(location.block).unwrap_or_else(|| {
panic!("could not find block at location {:?}", location);
});
let stmt = block.statements.get(location.statement_index).unwrap_or_else(|| {
panic!("could not find statement at location {:?}");
});
// Do kills introduced by NLL before setting up any potential
// gens. (See NOTE in kill_loans_out_of_scope_at_location.)
self.kill_loans_out_of_scope_at_location(sets, location, is_activations);
if is_activations {
// INVARIANT: `sets.on_entry` accurately captures
// reservations on entry to statement (b/c
// accumulates_intrablock_state is overridden for
// ActiveBorrows).
//
// Now compute the activations generated by uses within
// the statement based on that reservation state.
let mut find = FindPlaceUses { sets, assigned_map: &self.assigned_map };
find.visit_statement(location.block, stmt, location);
}
match stmt.kind {
// EndRegion kills any borrows (reservations and active borrows both)
mir::StatementKind::EndRegion(region_scope) => {
if let Some(borrow_indexes) = self.region_map.get(&ReScope(region_scope)) {
assert!(self.nonlexical_regioncx.is_none());
sets.kill_all(borrow_indexes);
for idx in borrow_indexes {
sets.kill(&ReserveOrActivateIndex::reserved(*idx));
if is_activations {
sets.kill(&ReserveOrActivateIndex::active(*idx));
}
}
} else {
// (if there is no entry, then there are no borrows to be tracked)
}
}
mir::StatementKind::Assign(_, ref rhs) => {
// NOTE: if/when the Assign case is revised to inspect
// the assigned_place here, make sure to also
// re-consider the current implementations of the
// propagate_call_return method.
if let mir::Rvalue::Ref(region, _, ref place) = *rhs {
if is_unsafe_place(self.tcx, self.mir, place) { return; }
if let RegionKind::ReEmpty = region {
@ -254,7 +381,7 @@ impl<'a, 'gcx, 'tcx> BitDenotation for Borrows<'a, 'gcx, 'tcx> {
assert!(self.region_map.get(region).unwrap_or_else(|| {
panic!("could not find BorrowIndexs for region {:?}", region);
}).contains(&index));
sets.gen(&index);
sets.gen(&ReserveOrActivateIndex::reserved(*index));
}
}
@ -264,7 +391,12 @@ impl<'a, 'gcx, 'tcx> BitDenotation for Borrows<'a, 'gcx, 'tcx> {
//
// FIXME: expand this to variables that are assigned over.
if let Some(borrow_indexes) = self.local_map.get(&local) {
sets.kill_all(borrow_indexes);
sets.kill_all(borrow_indexes.iter()
.map(|b| ReserveOrActivateIndex::reserved(*b)));
if is_activations {
sets.kill_all(borrow_indexes.iter()
.map(|b| ReserveOrActivateIndex::active(*b)));
}
}
}
@ -275,17 +407,37 @@ impl<'a, 'gcx, 'tcx> BitDenotation for Borrows<'a, 'gcx, 'tcx> {
mir::StatementKind::Nop => {}
}
self.kill_loans_out_of_scope_at_location(sets, location);
}
fn terminator_effect(&self,
sets: &mut BlockSets<BorrowIndex>,
location: Location) {
/// Models terminator effect in Reservations and ActiveBorrows
/// flow analyses; `is activations` tells us if we are in the
/// latter case.
fn terminator_effect_on_borrows(&self,
sets: &mut BlockSets<ReserveOrActivateIndex>,
location: Location,
is_activations: bool) {
let block = &self.mir.basic_blocks().get(location.block).unwrap_or_else(|| {
panic!("could not find block at location {:?}", location);
});
match block.terminator().kind {
// Do kills introduced by NLL before setting up any potential
// gens. (See NOTE in kill_loans_out_of_scope_at_location.)
self.kill_loans_out_of_scope_at_location(sets, location, is_activations);
let term = block.terminator();
if is_activations {
// INVARIANT: `sets.on_entry` accurately captures
// reservations on entry to terminator (b/c
// accumulates_intrablock_state is overridden for
// ActiveBorrows).
//
// Now compute effect of the terminator on the activations
// themselves in the ActiveBorrows state.
let mut find = FindPlaceUses { sets, assigned_map: &self.assigned_map };
find.visit_terminator(location.block, term, location);
}
match term.kind {
mir::TerminatorKind::Resume |
mir::TerminatorKind::Return |
mir::TerminatorKind::GeneratorDrop => {
@ -304,7 +456,10 @@ impl<'a, 'gcx, 'tcx> BitDenotation for Borrows<'a, 'gcx, 'tcx> {
if *scope != root_scope &&
self.scope_tree.is_subscope_of(*scope, root_scope)
{
sets.kill(&borrow_index);
sets.kill(&ReserveOrActivateIndex::reserved(borrow_index));
if is_activations {
sets.kill(&ReserveOrActivateIndex::active(borrow_index));
}
}
}
}
@ -320,29 +475,223 @@ impl<'a, 'gcx, 'tcx> BitDenotation for Borrows<'a, 'gcx, 'tcx> {
mir::TerminatorKind::FalseEdges {..} |
mir::TerminatorKind::Unreachable => {}
}
self.kill_loans_out_of_scope_at_location(sets, location);
}
}
impl<'a, 'gcx, 'tcx> ActiveBorrows<'a, 'gcx, 'tcx> {
pub(crate) fn borrows(&self) -> &IndexVec<BorrowIndex, BorrowData<'tcx>> {
self.0.borrows()
}
/// Returns the span for the "end point" given region. This will
/// return `None` if NLL is enabled, since that concept has no
/// meaning there. Otherwise, return region span if it exists and
/// span for end of the function if it doesn't exist.
pub(crate) fn opt_region_end_span(&self, region: &Region) -> Option<Span> {
match self.0.nonlexical_regioncx {
Some(_) => None,
None => {
match self.0.region_span_map.get(region) {
Some(span) => Some(span.end_point()),
None => Some(self.0.mir.span.end_point())
}
}
}
}
}
/// `FindPlaceUses` is a MIR visitor that updates `self.sets` for all
/// of the borrows activated by a given statement or terminator.
///
/// ----
///
/// The `ActiveBorrows` flow analysis, when inspecting any given
/// statement or terminator, needs to "generate" (i.e. set to 1) all
/// of the bits for the borrows that are activated by that
/// statement/terminator.
///
/// This struct will seek out all places that are assignment-targets
/// for borrows (gathered in `self.assigned_map`; see also the
/// `assigned_map` in `struct Borrows`), and set the corresponding
/// gen-bits for activations of those borrows in `self.sets`
struct FindPlaceUses<'a, 'b: 'a, 'tcx: 'a> {
assigned_map: &'a FxHashMap<Place<'tcx>, FxHashSet<BorrowIndex>>,
sets: &'a mut BlockSets<'b, ReserveOrActivateIndex>,
}
impl<'a, 'b, 'tcx> FindPlaceUses<'a, 'b, 'tcx> {
fn has_been_reserved(&self, b: &BorrowIndex) -> bool {
self.sets.on_entry.contains(&ReserveOrActivateIndex::reserved(*b))
}
/// return whether `context` should be considered a "use" of a
/// place found in that context. "Uses" activate associated
/// borrows (at least when such uses occur while the borrow also
/// has a reservation at the time).
fn is_potential_use(context: PlaceContext) -> bool {
match context {
// storage effects on an place do not activate it
PlaceContext::StorageLive | PlaceContext::StorageDead => false,
// validation effects do not activate an place
//
// FIXME: Should they? Is it just another read? Or can we
// guarantee it won't dereference the stored address? How
// "deep" does validation go?
PlaceContext::Validate => false,
// pure overwrites of an place do not activate it. (note
// PlaceContext::Call is solely about dest place)
PlaceContext::Store | PlaceContext::Call => false,
// reads of an place *do* activate it
PlaceContext::Move |
PlaceContext::Copy |
PlaceContext::Drop |
PlaceContext::Inspect |
PlaceContext::Borrow { .. } |
PlaceContext::Projection(..) => true,
}
}
}
impl<'a, 'b, 'tcx> Visitor<'tcx> for FindPlaceUses<'a, 'b, 'tcx> {
fn visit_place(&mut self,
place: &mir::Place<'tcx>,
context: PlaceContext<'tcx>,
location: Location) {
debug!("FindPlaceUses place: {:?} assigned from borrows: {:?} \
used in context: {:?} at location: {:?}",
place, self.assigned_map.get(place), context, location);
if Self::is_potential_use(context) {
if let Some(borrows) = self.assigned_map.get(place) {
for borrow_idx in borrows {
debug!("checking if index {:?} for {:?} is reserved ({}) \
and thus needs active gen-bit set in sets {:?}",
borrow_idx, place, self.has_been_reserved(&borrow_idx), self.sets);
if self.has_been_reserved(&borrow_idx) {
self.sets.gen(&ReserveOrActivateIndex::active(*borrow_idx));
} else {
// (This can certainly happen in valid code. I
// just want to know about it in the short
// term.)
debug!("encountered use of Place {:?} of borrow_idx {:?} \
at location {:?} outside of reservation",
place, borrow_idx, location);
}
}
}
}
self.super_place(place, context, location);
}
}
impl<'a, 'gcx, 'tcx> BitDenotation for Reservations<'a, 'gcx, 'tcx> {
type Idx = ReserveOrActivateIndex;
fn name() -> &'static str { "reservations" }
fn bits_per_block(&self) -> usize {
self.0.borrows.len() * 2
}
fn start_block_effect(&self, _entry_set: &mut IdxSet<ReserveOrActivateIndex>) {
// no borrows of code region_scopes have been taken prior to
// function execution, so this method has no effect on
// `_sets`.
}
fn statement_effect(&self,
sets: &mut BlockSets<ReserveOrActivateIndex>,
location: Location) {
debug!("Reservations::statement_effect sets: {:?} location: {:?}", sets, location);
self.0.statement_effect_on_borrows(sets, location, false);
}
fn terminator_effect(&self,
sets: &mut BlockSets<ReserveOrActivateIndex>,
location: Location) {
debug!("Reservations::terminator_effect sets: {:?} location: {:?}", sets, location);
self.0.terminator_effect_on_borrows(sets, location, false);
}
fn propagate_call_return(&self,
_in_out: &mut IdxSet<BorrowIndex>,
_in_out: &mut IdxSet<ReserveOrActivateIndex>,
_call_bb: mir::BasicBlock,
_dest_bb: mir::BasicBlock,
_dest_place: &mir::Place) {
// there are no effects on the region scopes from method calls.
// there are no effects on borrows from method call return...
//
// ... but if overwriting a place can affect flow state, then
// latter is not true; see NOTE on Assign case in
// statement_effect_on_borrows.
}
}
impl<'a, 'gcx, 'tcx> BitwiseOperator for Borrows<'a, 'gcx, 'tcx> {
impl<'a, 'gcx, 'tcx> BitDenotation for ActiveBorrows<'a, 'gcx, 'tcx> {
type Idx = ReserveOrActivateIndex;
fn name() -> &'static str { "active_borrows" }
/// Overriding this method; `ActiveBorrows` uses the intrablock
/// state in `on_entry` to track the current reservations (which
/// then affect the construction of the gen/kill sets for
/// activations).
fn accumulates_intrablock_state() -> bool { true }
fn bits_per_block(&self) -> usize {
self.0.borrows.len() * 2
}
fn start_block_effect(&self, _entry_sets: &mut IdxSet<ReserveOrActivateIndex>) {
// no borrows of code region_scopes have been taken prior to
// function execution, so this method has no effect on
// `_sets`.
}
fn statement_effect(&self,
sets: &mut BlockSets<ReserveOrActivateIndex>,
location: Location) {
debug!("ActiveBorrows::statement_effect sets: {:?} location: {:?}", sets, location);
self.0.statement_effect_on_borrows(sets, location, true);
}
fn terminator_effect(&self,
sets: &mut BlockSets<ReserveOrActivateIndex>,
location: Location) {
debug!("ActiveBorrows::terminator_effect sets: {:?} location: {:?}", sets, location);
self.0.terminator_effect_on_borrows(sets, location, true);
}
fn propagate_call_return(&self,
_in_out: &mut IdxSet<ReserveOrActivateIndex>,
_call_bb: mir::BasicBlock,
_dest_bb: mir::BasicBlock,
_dest_place: &mir::Place) {
// there are no effects on borrows from method call return...
//
// ... but If overwriting a place can affect flow state, then
// latter is not true; see NOTE on Assign case in
// statement_effect_on_borrows.
}
}
impl<'a, 'gcx, 'tcx> BitwiseOperator for Reservations<'a, 'gcx, 'tcx> {
#[inline]
fn join(&self, pred1: usize, pred2: usize) -> usize {
pred1 | pred2 // union effects of preds when computing borrows
pred1 | pred2 // union effects of preds when computing reservations
}
}
impl<'a, 'gcx, 'tcx> DataflowOperator for Borrows<'a, 'gcx, 'tcx> {
impl<'a, 'gcx, 'tcx> BitwiseOperator for ActiveBorrows<'a, 'gcx, 'tcx> {
#[inline]
fn join(&self, pred1: usize, pred2: usize) -> usize {
pred1 | pred2 // union effects of preds when computing activations
}
}
impl<'a, 'gcx, 'tcx> InitialFlow for Reservations<'a, 'gcx, 'tcx> {
#[inline]
fn bottom_value() -> bool {
false // bottom = no Rvalue::Refs are active by default
false // bottom = no Rvalue::Refs are reserved by default
}
}

12
src/librustc_mir/dataflow/impls/mod.rs
View File

@ -23,7 +23,7 @@ use util::elaborate_drops::DropFlagState;
use super::move_paths::{HasMoveData, MoveData, MoveOutIndex, MovePathIndex, InitIndex};
use super::move_paths::{LookupResult, InitKind};
use super::{BitDenotation, BlockSets, DataflowOperator};
use super::{BitDenotation, BlockSets, InitialFlow};
use super::drop_flag_effects_for_function_entry;
use super::drop_flag_effects_for_location;
@ -702,35 +702,35 @@ impl<'a, 'gcx, 'tcx> BitwiseOperator for EverInitializedLvals<'a, 'gcx, 'tcx> {
// propagating, or you start at all-ones and then use Intersect as
// your merge when propagating.
impl<'a, 'gcx, 'tcx> DataflowOperator for MaybeInitializedLvals<'a, 'gcx, 'tcx> {
impl<'a, 'gcx, 'tcx> InitialFlow for MaybeInitializedLvals<'a, 'gcx, 'tcx> {
#[inline]
fn bottom_value() -> bool {
false // bottom = uninitialized
}
}
impl<'a, 'gcx, 'tcx> DataflowOperator for MaybeUninitializedLvals<'a, 'gcx, 'tcx> {
impl<'a, 'gcx, 'tcx> InitialFlow for MaybeUninitializedLvals<'a, 'gcx, 'tcx> {
#[inline]
fn bottom_value() -> bool {
false // bottom = initialized (start_block_effect counters this at outset)
}
}
impl<'a, 'gcx, 'tcx> DataflowOperator for DefinitelyInitializedLvals<'a, 'gcx, 'tcx> {
impl<'a, 'gcx, 'tcx> InitialFlow for DefinitelyInitializedLvals<'a, 'gcx, 'tcx> {
#[inline]
fn bottom_value() -> bool {
true // bottom = initialized (start_block_effect counters this at outset)
}
}
impl<'a, 'gcx, 'tcx> DataflowOperator for MovingOutStatements<'a, 'gcx, 'tcx> {
impl<'a, 'gcx, 'tcx> InitialFlow for MovingOutStatements<'a, 'gcx, 'tcx> {
#[inline]
fn bottom_value() -> bool {
false // bottom = no loans in scope by default
}
}
impl<'a, 'gcx, 'tcx> DataflowOperator for EverInitializedLvals<'a, 'gcx, 'tcx> {
impl<'a, 'gcx, 'tcx> InitialFlow for EverInitializedLvals<'a, 'gcx, 'tcx> {
#[inline]
fn bottom_value() -> bool {
false // bottom = no initialized variables by default

2
src/librustc_mir/dataflow/impls/storage_liveness.rs
View File

@ -74,7 +74,7 @@ impl<'a, 'tcx> BitwiseOperator for MaybeStorageLive<'a, 'tcx> {
}
}
impl<'a, 'tcx> DataflowOperator for MaybeStorageLive<'a, 'tcx> {
impl<'a, 'tcx> InitialFlow for MaybeStorageLive<'a, 'tcx> {
#[inline]
fn bottom_value() -> bool {
false // bottom = dead

236
src/librustc_mir/dataflow/mod.rs
View File

@ -18,8 +18,8 @@ use rustc::ty::{self, TyCtxt};
use rustc::mir::{self, Mir, BasicBlock, BasicBlockData, Location, Statement, Terminator};
use rustc::session::Session;
use std::borrow::Borrow;
use std::fmt::{self, Debug};
use std::borrow::{Borrow, Cow};
use std::fmt;
use std::io;
use std::mem;
use std::path::PathBuf;
@ -29,7 +29,8 @@ pub use self::impls::{MaybeStorageLive};
pub use self::impls::{MaybeInitializedLvals, MaybeUninitializedLvals};
pub use self::impls::{DefinitelyInitializedLvals, MovingOutStatements};
pub use self::impls::EverInitializedLvals;
pub use self::impls::borrows::{Borrows, BorrowData, BorrowIndex};
pub use self::impls::borrows::{Borrows, BorrowData};
pub(crate) use self::impls::borrows::{ActiveBorrows, Reservations, ReserveOrActivateIndex};
pub use self::at_location::{FlowAtLocation, FlowsAtLocation};
pub(crate) use self::drop_flag_effects::*;
@ -51,10 +52,29 @@ pub(crate) struct DataflowBuilder<'a, 'tcx: 'a, BD> where BD: BitDenotation
print_postflow_to: Option<String>,
}
pub trait Dataflow<BD: BitDenotation> {
/// `DebugFormatted` encapsulates the "{:?}" rendering of some
/// arbitrary value. This way: you pay cost of allocating an extra
/// string (as well as that of rendering up-front); in exchange, you
/// don't have to hand over ownership of your value or deal with
/// borrowing it.
pub(crate) struct DebugFormatted(String);
impl DebugFormatted {
pub fn new(input: &fmt::Debug) -> DebugFormatted {
DebugFormatted(format!("{:?}", input))
}
}
impl fmt::Debug for DebugFormatted {
fn fmt(&self, w: &mut fmt::Formatter) -> fmt::Result {
write!(w, "{}", self.0)
}
}
pub(crate) trait Dataflow<BD: BitDenotation> {
/// Sets up and runs the dataflow problem, using `p` to render results if
/// implementation so chooses.
fn dataflow<P>(&mut self, p: P) where P: Fn(&BD, BD::Idx) -> &Debug {
fn dataflow<P>(&mut self, p: P) where P: Fn(&BD, BD::Idx) -> DebugFormatted {
let _ = p; // default implementation does not instrument process.
self.build_sets();
self.propagate();
@ -69,7 +89,7 @@ pub trait Dataflow<BD: BitDenotation> {
impl<'a, 'tcx: 'a, BD> Dataflow<BD> for DataflowBuilder<'a, 'tcx, BD> where BD: BitDenotation
{
fn dataflow<P>(&mut self, p: P) where P: Fn(&BD, BD::Idx) -> &Debug {
fn dataflow<P>(&mut self, p: P) where P: Fn(&BD, BD::Idx) -> DebugFormatted {
self.flow_state.build_sets();
self.pre_dataflow_instrumentation(|c,i| p(c,i)).unwrap();
self.flow_state.propagate();
@ -101,44 +121,56 @@ pub struct MoveDataParamEnv<'gcx, 'tcx> {
}
pub(crate) fn do_dataflow<'a, 'gcx, 'tcx, BD, P>(tcx: TyCtxt<'a, 'gcx, 'tcx>,
mir: &Mir<'tcx>,
mir: &'a Mir<'tcx>,
node_id: ast::NodeId,
attributes: &[ast::Attribute],
dead_unwinds: &IdxSet<BasicBlock>,
bd: BD,
p: P)
-> DataflowResults<BD>
where BD: BitDenotation,
P: Fn(&BD, BD::Idx) -> &fmt::Debug
where BD: BitDenotation + InitialFlow,
P: Fn(&BD, BD::Idx) -> DebugFormatted
{
let name_found = |sess: &Session, attrs: &[ast::Attribute], name| -> Option<String> {
if let Some(item) = has_rustc_mir_with(attrs, name) {
if let Some(s) = item.value_str() {
return Some(s.to_string())
} else {
sess.span_err(
item.span,
&format!("{} attribute requires a path", item.name()));
return None;
let flow_state = DataflowAnalysis::new(mir, dead_unwinds, bd);
flow_state.run(tcx, node_id, attributes, p)
}
impl<'a, 'gcx: 'tcx, 'tcx: 'a, BD> DataflowAnalysis<'a, 'tcx, BD> where BD: BitDenotation
{
pub(crate) fn run<P>(self,
tcx: TyCtxt<'a, 'gcx, 'tcx>,
node_id: ast::NodeId,
attributes: &[ast::Attribute],
p: P) -> DataflowResults<BD>
where P: Fn(&BD, BD::Idx) -> DebugFormatted
{
let name_found = |sess: &Session, attrs: &[ast::Attribute], name| -> Option<String> {
if let Some(item) = has_rustc_mir_with(attrs, name) {
if let Some(s) = item.value_str() {
return Some(s.to_string())
} else {
sess.span_err(
item.span,
&format!("{} attribute requires a path", item.name()));
return None;
}
}
}
return None;
};
return None;
};
let print_preflow_to =
name_found(tcx.sess, attributes, "borrowck_graphviz_preflow");
let print_postflow_to =
name_found(tcx.sess, attributes, "borrowck_graphviz_postflow");
let print_preflow_to =
name_found(tcx.sess, attributes, "borrowck_graphviz_preflow");
let print_postflow_to =
name_found(tcx.sess, attributes, "borrowck_graphviz_postflow");
let mut mbcx = DataflowBuilder {
node_id,
print_preflow_to,
print_postflow_to,
flow_state: DataflowAnalysis::new(tcx, mir, dead_unwinds, bd),
};
let mut mbcx = DataflowBuilder {
node_id,
print_preflow_to, print_postflow_to, flow_state: self,
};
mbcx.dataflow(p);
mbcx.flow_state.results()
mbcx.dataflow(p);
mbcx.flow_state.results()
}
}
struct PropagationContext<'b, 'a: 'b, 'tcx: 'a, O> where O: 'b + BitDenotation
@ -157,17 +189,12 @@ impl<'a, 'tcx: 'a, BD> DataflowAnalysis<'a, 'tcx, BD> where BD: BitDenotation
};
while propcx.changed {
propcx.changed = false;
propcx.reset(&mut temp);
propcx.walk_cfg(&mut temp);
}
}
fn build_sets(&mut self) {
// First we need to build the entry-, gen- and kill-sets. The
// gather_moves information provides a high-level mapping from
// mir-locations to the MoveOuts (and those correspond
// directly to gen-sets here). But we still need to figure out
// the kill-sets.
// First we need to build the entry-, gen- and kill-sets.
{
let sets = &mut self.flow_state.sets.for_block(mir::START_BLOCK.index());
@ -177,15 +204,28 @@ impl<'a, 'tcx: 'a, BD> DataflowAnalysis<'a, 'tcx, BD> where BD: BitDenotation
for (bb, data) in self.mir.basic_blocks().iter_enumerated() {
let &mir::BasicBlockData { ref statements, ref terminator, is_cleanup: _ } = data;
let mut interim_state;
let sets = &mut self.flow_state.sets.for_block(bb.index());
let track_intrablock = BD::accumulates_intrablock_state();
if track_intrablock {
debug!("swapping in mutable on_entry, initially {:?}", sets.on_entry);
interim_state = sets.on_entry.to_owned();
sets.on_entry = &mut interim_state;
}
for j_stmt in 0..statements.len() {
let location = Location { block: bb, statement_index: j_stmt };
self.flow_state.operator.statement_effect(sets, location);
if track_intrablock {
sets.apply_local_effect();
}
}
if terminator.is_some() {
let location = Location { block: bb, statement_index: statements.len() };
self.flow_state.operator.terminator_effect(sets, location);
if track_intrablock {
sets.apply_local_effect();
}
}
}
}
@ -193,13 +233,6 @@ impl<'a, 'tcx: 'a, BD> DataflowAnalysis<'a, 'tcx, BD> where BD: BitDenotation
impl<'b, 'a: 'b, 'tcx: 'a, BD> PropagationContext<'b, 'a, 'tcx, BD> where BD: BitDenotation
{
fn reset(&mut self, bits: &mut IdxSet<BD::Idx>) {
let e = if BD::bottom_value() {!0} else {0};
for b in bits.words_mut() {
*b = e;
}
}
fn walk_cfg(&mut self, in_out: &mut IdxSet<BD::Idx>) {
let mir = self.builder.mir;
for (bb_idx, bb_data) in mir.basic_blocks().iter().enumerate() {
@ -231,7 +264,7 @@ fn dataflow_path(context: &str, prepost: &str, path: &str) -> PathBuf {
impl<'a, 'tcx: 'a, BD> DataflowBuilder<'a, 'tcx, BD> where BD: BitDenotation
{
fn pre_dataflow_instrumentation<P>(&self, p: P) -> io::Result<()>
where P: Fn(&BD, BD::Idx) -> &Debug
where P: Fn(&BD, BD::Idx) -> DebugFormatted
{
if let Some(ref path_str) = self.print_preflow_to {
let path = dataflow_path(BD::name(), "preflow", path_str);
@ -242,7 +275,7 @@ impl<'a, 'tcx: 'a, BD> DataflowBuilder<'a, 'tcx, BD> where BD: BitDenotation
}
fn post_dataflow_instrumentation<P>(&self, p: P) -> io::Result<()>
where P: Fn(&BD, BD::Idx) -> &Debug
where P: Fn(&BD, BD::Idx) -> DebugFormatted
{
if let Some(ref path_str) = self.print_postflow_to {
let path = dataflow_path(BD::name(), "postflow", path_str);
@ -255,7 +288,7 @@ impl<'a, 'tcx: 'a, BD> DataflowBuilder<'a, 'tcx, BD> where BD: BitDenotation
/// Maps each block to a set of bits
#[derive(Debug)]
struct Bits<E:Idx> {
pub(crate) struct Bits<E:Idx> {
bits: IdxSetBuf<E>,
}
@ -276,7 +309,7 @@ impl<E:Idx> Bits<E> {
/// underlying flow analysis results, because it needs to handle cases
/// where we are combining the results of *multiple* flow analyses
/// (e.g. borrows + inits + uninits).
pub trait DataflowResultsConsumer<'a, 'tcx: 'a> {
pub(crate) trait DataflowResultsConsumer<'a, 'tcx: 'a> {
type FlowState: FlowsAtLocation;
// Observation Hooks: override (at least one of) these to get analysis feedback.
@ -403,12 +436,12 @@ impl<O: BitDenotation> DataflowState<O> {
words.each_bit(bits_per_block, f)
}
pub fn interpret_set<'c, P>(&self,
o: &'c O,
words: &IdxSet<O::Idx>,
render_idx: &P)
-> Vec<&'c Debug>
where P: Fn(&O, O::Idx) -> &Debug
pub(crate) fn interpret_set<'c, P>(&self,
o: &'c O,
words: &IdxSet<O::Idx>,
render_idx: &P)
-> Vec<DebugFormatted>
where P: Fn(&O, O::Idx) -> DebugFormatted
{
let mut v = Vec::new();
self.each_bit(words, |i| {
@ -455,6 +488,7 @@ pub struct AllSets<E: Idx> {
/// killed during the iteration. (This is such a good idea that the
/// `fn gen` and `fn kill` methods that set their state enforce this
/// for you.)
#[derive(Debug)]
pub struct BlockSets<'a, E: Idx> {
/// Dataflow state immediately before control flow enters the given block.
pub(crate) on_entry: &'a mut IdxSet<E>,
@ -496,6 +530,7 @@ impl<'a, E:Idx> BlockSets<'a, E> {
self.gen_set.remove(e);
self.kill_set.add(e);
}
fn kill_all<I>(&mut self, i: I)
where I: IntoIterator,
I::Item: Borrow<E>
@ -504,6 +539,11 @@ impl<'a, E:Idx> BlockSets<'a, E> {
self.kill(j.borrow());
}
}
fn apply_local_effect(&mut self) {
self.on_entry.union(&self.gen_set);
self.on_entry.subtract(&self.kill_set);
}
}
impl<E:Idx> AllSets<E> {
@ -532,18 +572,51 @@ impl<E:Idx> AllSets<E> {
pub fn on_entry_set_for(&self, block_idx: usize) -> &IdxSet<E> {
self.lookup_set_for(&self.on_entry_sets, block_idx)
}
pub(crate) fn entry_set_state(&self) -> &Bits<E> {
&self.on_entry_sets
}
}
/// Parameterization for the precise form of data flow that is used.
pub trait DataflowOperator: BitwiseOperator {
/// `InitialFlow` handles initializing the bitvectors before any
/// code is inspected by the analysis. Analyses that need more nuanced
/// initialization (e.g. they need to consult the results of some other
/// dataflow analysis to set up the initial bitvectors) should not
/// implement this.
pub trait InitialFlow {
/// Specifies the initial value for each bit in the `on_entry` set
fn bottom_value() -> bool;
}
pub trait BitDenotation: DataflowOperator {
pub trait BitDenotation: BitwiseOperator {
/// Specifies what index type is used to access the bitvector.
type Idx: Idx;
/// Some analyses want to accumulate knowledge within a block when
/// analyzing its statements for building the gen/kill sets. Override
/// this method to return true in such cases.
///
/// When this returns true, the statement-effect (re)construction
/// will clone the `on_entry` state and pass along a reference via
/// `sets.on_entry` to that local clone into `statement_effect` and
/// `terminator_effect`).
///
/// When its false, no local clone is constucted; instead a
/// reference directly into `on_entry` is passed along via
/// `sets.on_entry` instead, which represents the flow state at
/// the block's start, not necessarily the state immediately prior
/// to the statement/terminator under analysis.
///
/// In either case, the passed reference is mutable; but this is a
/// wart from using the `BlockSets` type in the API; the intention
/// is that the `statement_effect` and `terminator_effect` methods
/// mutate only the gen/kill sets.
///
/// FIXME: We should consider enforcing the intention described in
/// the previous paragraph by passing the three sets in separate
/// parameters to encode their distinct mutabilities.
fn accumulates_intrablock_state() -> bool { false }
/// A name describing the dataflow analysis that this
/// BitDenotation is supporting. The name should be something
/// suitable for plugging in as part of a filename e.g. avoid
@ -618,29 +691,33 @@ pub trait BitDenotation: DataflowOperator {
dest_place: &mir::Place);
}
impl<'a, 'gcx, 'tcx: 'a, D> DataflowAnalysis<'a, 'tcx, D> where D: BitDenotation
impl<'a, 'tcx, D> DataflowAnalysis<'a, 'tcx, D> where D: BitDenotation
{
pub fn new(_tcx: TyCtxt<'a, 'gcx, 'tcx>,
mir: &'a Mir<'tcx>,
pub fn new(mir: &'a Mir<'tcx>,
dead_unwinds: &'a IdxSet<mir::BasicBlock>,
denotation: D) -> Self {
denotation: D) -> Self where D: InitialFlow {
let bits_per_block = denotation.bits_per_block();
let usize_bits = mem::size_of::<usize>() * 8;
let words_per_block = (bits_per_block + usize_bits - 1) / usize_bits;
// (now rounded up to multiple of word size)
let bits_per_block = words_per_block * usize_bits;
let num_blocks = mir.basic_blocks().len();
let num_overall = num_blocks * bits_per_block;
let zeroes = Bits::new(IdxSetBuf::new_empty(num_overall));
let num_overall = Self::num_bits_overall(mir, bits_per_block);
let on_entry = Bits::new(if D::bottom_value() {
IdxSetBuf::new_filled(num_overall)
} else {
IdxSetBuf::new_empty(num_overall)
});
Self::new_with_entry_sets(mir, dead_unwinds, Cow::Owned(on_entry), denotation)
}
pub(crate) fn new_with_entry_sets(mir: &'a Mir<'tcx>,
dead_unwinds: &'a IdxSet<mir::BasicBlock>,
on_entry: Cow<Bits<D::Idx>>,
denotation: D)
-> Self {
let bits_per_block = denotation.bits_per_block();
let usize_bits = mem::size_of::<usize>() * 8;
let words_per_block = (bits_per_block + usize_bits - 1) / usize_bits;
let num_overall = Self::num_bits_overall(mir, bits_per_block);
assert_eq!(num_overall, on_entry.bits.words().len() * usize_bits);
let zeroes = Bits::new(IdxSetBuf::new_empty(num_overall));
DataflowAnalysis {
mir,
dead_unwinds,
@ -650,12 +727,23 @@ impl<'a, 'gcx, 'tcx: 'a, D> DataflowAnalysis<'a, 'tcx, D> where D: BitDenotation
words_per_block,
gen_sets: zeroes.clone(),
kill_sets: zeroes,
on_entry_sets: on_entry,
on_entry_sets: on_entry.into_owned(),
},
operator: denotation,
},
}
}
}
fn num_bits_overall(mir: &Mir, bits_per_block: usize) -> usize {
let usize_bits = mem::size_of::<usize>() * 8;
let words_per_block = (bits_per_block + usize_bits - 1) / usize_bits;
// (now rounded up to multiple of word size)
let bits_per_block = words_per_block * usize_bits;
let num_blocks = mir.basic_blocks().len();
let num_overall = num_blocks * bits_per_block;
num_overall
}
}

3
src/librustc_mir/dataflow/move_paths/mod.rs
View File

@ -65,6 +65,9 @@ pub(crate) mod indexes {
/// Index into Borrows.locations
new_index!(BorrowIndex, "bw");
/// Index into Reservations/Activations bitvector
new_index!(ReserveOrActivateIndex, "ra");
}
pub use self::indexes::MovePathIndex;

20
src/librustc_mir/transform/elaborate_drops.rs
View File

@ -14,7 +14,7 @@ use dataflow::{DataflowResults};
use dataflow::{on_all_children_bits, on_all_drop_children_bits};
use dataflow::{drop_flag_effects_for_location, on_lookup_result_bits};
use dataflow::MoveDataParamEnv;
use dataflow;
use dataflow::{self, do_dataflow, DebugFormatted};
use rustc::hir;
use rustc::ty::{self, TyCtxt};
use rustc::mir::*;
@ -59,13 +59,13 @@ impl MirPass for ElaborateDrops {
};
let dead_unwinds = find_dead_unwinds(tcx, mir, id, &env);
let flow_inits =
dataflow::do_dataflow(tcx, mir, id, &[], &dead_unwinds,
MaybeInitializedLvals::new(tcx, mir, &env),
|bd, p| &bd.move_data().move_paths[p]);
do_dataflow(tcx, mir, id, &[], &dead_unwinds,
MaybeInitializedLvals::new(tcx, mir, &env),
|bd, p| DebugFormatted::new(&bd.move_data().move_paths[p]));
let flow_uninits =
dataflow::do_dataflow(tcx, mir, id, &[], &dead_unwinds,
MaybeUninitializedLvals::new(tcx, mir, &env),
|bd, p| &bd.move_data().move_paths[p]);
do_dataflow(tcx, mir, id, &[], &dead_unwinds,
MaybeUninitializedLvals::new(tcx, mir, &env),
|bd, p| DebugFormatted::new(&bd.move_data().move_paths[p]));
ElaborateDropsCtxt {
tcx,
@ -96,9 +96,9 @@ fn find_dead_unwinds<'a, 'tcx>(
// reach cleanup blocks, which can't have unwind edges themselves.
let mut dead_unwinds = IdxSetBuf::new_empty(mir.basic_blocks().len());
let flow_inits =
dataflow::do_dataflow(tcx, mir, id, &[], &dead_unwinds,
MaybeInitializedLvals::new(tcx, mir, &env),
|bd, p| &bd.move_data().move_paths[p]);
do_dataflow(tcx, mir, id, &[], &dead_unwinds,
MaybeInitializedLvals::new(tcx, mir, &env),
|bd, p| DebugFormatted::new(&bd.move_data().move_paths[p]));
for (bb, bb_data) in mir.basic_blocks().iter_enumerated() {
let location = match bb_data.terminator().kind {
TerminatorKind::Drop { ref location, unwind: Some(_), .. } |

6
src/librustc_mir/transform/generator.rs
View File

@ -78,7 +78,7 @@ use std::mem;
use transform::{MirPass, MirSource};
use transform::simplify;
use transform::no_landing_pads::no_landing_pads;
use dataflow::{self, MaybeStorageLive, state_for_location};
use dataflow::{do_dataflow, DebugFormatted, MaybeStorageLive, state_for_location};
pub struct StateTransform;
@ -341,8 +341,8 @@ fn locals_live_across_suspend_points<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
let node_id = tcx.hir.as_local_node_id(source.def_id).unwrap();
let analysis = MaybeStorageLive::new(mir);
let storage_live =
dataflow::do_dataflow(tcx, mir, node_id, &[], &dead_unwinds, analysis,
|bd, p| &bd.mir().local_decls[p]);
do_dataflow(tcx, mir, node_id, &[], &dead_unwinds, analysis,
|bd, p| DebugFormatted::new(&bd.mir().local_decls[p]));
let mut ignored = StorageIgnored(IdxSetBuf::new_filled(mir.local_decls.len()));
ignored.visit_mir(mir);

8
src/librustc_mir/transform/rustc_peek.rs
View File

@ -18,7 +18,7 @@ use rustc_data_structures::indexed_set::IdxSetBuf;
use rustc_data_structures::indexed_vec::Idx;
use transform::{MirPass, MirSource};
use dataflow::do_dataflow;
use dataflow::{do_dataflow, DebugFormatted};
use dataflow::MoveDataParamEnv;
use dataflow::BitDenotation;
use dataflow::DataflowResults;
@ -51,15 +51,15 @@ impl MirPass for SanityCheck {
let flow_inits =
do_dataflow(tcx, mir, id, &attributes, &dead_unwinds,
MaybeInitializedLvals::new(tcx, mir, &mdpe),
|bd, i| &bd.move_data().move_paths[i]);
|bd, i| DebugFormatted::new(&bd.move_data().move_paths[i]));
let flow_uninits =
do_dataflow(tcx, mir, id, &attributes, &dead_unwinds,
MaybeUninitializedLvals::new(tcx, mir, &mdpe),
|bd, i| &bd.move_data().move_paths[i]);
|bd, i| DebugFormatted::new(&bd.move_data().move_paths[i]));
let flow_def_inits =
do_dataflow(tcx, mir, id, &attributes, &dead_unwinds,
DefinitelyInitializedLvals::new(tcx, mir, &mdpe),
|bd, i| &bd.move_data().move_paths[i]);
|bd, i| DebugFormatted::new(&bd.move_data().move_paths[i]));
if has_rustc_mir_with(&attributes, "rustc_peek_maybe_init").is_some() {
sanity_check_via_rustc_peek(tcx, mir, id, &attributes, &flow_inits);

62
src/test/compile-fail/borrowck/two-phase-activation-sharing-interference.rs Normal file
View File

@ -0,0 +1,62 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// revisions: lxl nll
//[lxl]compile-flags: -Z borrowck=mir -Z two-phase-borrows
//[nll]compile-flags: -Z borrowck=mir -Z two-phase-borrows -Z nll
// This is an important corner case pointed out by Niko: one is
// allowed to initiate a shared borrow during a reservation, but it
// *must end* before the activation occurs.
//
// FIXME: for clarity, diagnostics for these cases might be better off
// if they specifically said "cannot activate mutable borrow of `x`"
#![allow(dead_code)]
fn read(_: &i32) { }
fn ok() {
let mut x = 3;
let y = &mut x;
{ let z = &x; read(z); }
*y += 1;
}
fn not_ok() {
let mut x = 3;
let y = &mut x;
let z = &x;
*y += 1;
//[lxl]~^ ERROR cannot borrow `x` as mutable because it is also borrowed as immutable
//[nll]~^^ ERROR cannot borrow `x` as mutable because it is also borrowed as immutable
read(z);
}
fn should_be_ok_with_nll() {
let mut x = 3;
let y = &mut x;
let z = &x;
read(z);
*y += 1;
//[lxl]~^ ERROR cannot borrow `x` as mutable because it is also borrowed as immutable
// (okay with nll today)
}
fn should_also_eventually_be_ok_with_nll() {
let mut x = 3;
let y = &mut x;
let _z = &x;
*y += 1;
//[lxl]~^ ERROR cannot borrow `x` as mutable because it is also borrowed as immutable
//[nll]~^^ ERROR cannot borrow `x` as mutable because it is also borrowed as immutable
}
fn main() { }

37
src/test/compile-fail/borrowck/two-phase-allow-access-during-reservation.rs Normal file
View File

@ -0,0 +1,37 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// revisions: lxl nll
//[lxl]compile-flags: -Z borrowck=mir -Z two-phase-borrows
//[nll]compile-flags: -Z borrowck=mir -Z two-phase-borrows -Z nll
// This is the second counter-example from Niko's blog post
// smallcultfollowing.com/babysteps/blog/2017/03/01/nested-method-calls-via-two-phase-borrowing/
//
// It is "artificial". It is meant to illustrate directly that we
// should allow an aliasing access during reservation, but *not* while
// the mutable borrow is active.
fn main() {
/*0*/ let mut i = 0;
/*1*/ let p = &mut i; // (reservation of `i` starts here)
/*2*/ let j = i; // OK: `i` is only reserved here
/*3*/ *p += 1; // (mutable borrow of `i` starts here, since `p` is used)
/*4*/ let k = i; //[lxl]~ ERROR cannot use `i` because it was mutably borrowed [E0503]
//[nll]~^ ERROR cannot use `i` because it was mutably borrowed [E0503]
/*5*/ *p += 1;
let _ = (j, k, p);
}

34
src/test/compile-fail/borrowck/two-phase-cannot-nest-mut-self-calls.rs Normal file
View File

@ -0,0 +1,34 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// revisions: lxl nll
//[lxl]compile-flags: -Z borrowck=mir -Z two-phase-borrows
//[nll]compile-flags: -Z borrowck=mir -Z two-phase-borrows -Z nll
// This is the third counter-example from Niko's blog post
// smallcultfollowing.com/babysteps/blog/2017/03/01/nested-method-calls-via-two-phase-borrowing/
//
// It shows that not all nested method calls on `self` are magically
// allowed by this change. In particular, a nested `&mut` borrow is
// still disallowed.
fn main() {
let mut vec = vec![0, 1];
vec.get({
vec.push(2);
//[lxl]~^ ERROR cannot borrow `vec` as mutable because it is also borrowed as immutable
//[nll]~^^ ERROR cannot borrow `vec` as mutable because it is also borrowed as immutable
0
});
}

37
src/test/compile-fail/borrowck/two-phase-reservation-sharing-interference-2.rs Normal file
View File

@ -0,0 +1,37 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// revisions: lxl nll
//[lxl]compile-flags: -Z borrowck=mir -Z two-phase-borrows
//[nll]compile-flags: -Z borrowck=mir -Z two-phase-borrows -Z nll
// This is similar to two-phase-reservation-sharing-interference.rs
// in that it shows a reservation that overlaps with a shared borrow.
//
// Currently, this test fails with lexical lifetimes, but succeeds
// with non-lexical lifetimes. (The reason is because the activation
// of the mutable borrow ends up overlapping with a lexically-scoped
// shared borrow; but a non-lexical shared borrow can end before the
// activation occurs.)
//
// So this test is just making a note of the current behavior.
#![feature(rustc_attrs)]
#[rustc_error]
fn main() { //[nll]~ ERROR compilation successful
let mut v = vec![0, 1, 2];
let shared = &v;
v.push(shared.len());
//[lxl]~^ ERROR cannot borrow `v` as mutable because it is also borrowed as immutable [E0502]
assert_eq!(v, [0, 1, 2, 3]);
}

46
src/test/compile-fail/borrowck/two-phase-reservation-sharing-interference.rs Normal file
View File

@ -0,0 +1,46 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// revisions: lxl nll
//[lxl]compile-flags: -Z borrowck=mir -Z two-phase-borrows
//[nll]compile-flags: -Z borrowck=mir -Z two-phase-borrows -Z nll
// This is a corner case that the current implementation is (probably)
// treating more conservatively than is necessary. But it also does
// not seem like a terribly important use case to cover.
//
// So this test is just making a note of the current behavior, with
// the caveat that in the future, the rules may be loosened, at which
// point this test might be thrown out.
fn main() {
let mut vec = vec![0, 1];
let delay: &mut Vec<_>;
{
let shared = &vec;
// we reserve here, which could (on its own) be compatible
// with the shared borrow. But in the current implementation,
// its an error.
delay = &mut vec;
//[lxl]~^ ERROR cannot borrow `vec` as mutable because it is also borrowed as immutable
//[nll]~^^ ERROR cannot borrow `vec` as mutable because it is also borrowed as immutable
shared[0];
}
// the &mut-borrow only becomes active way down here.
//
// (At least in theory; part of the reason this test fails is that
// the constructed MIR throws in extra &mut reborrows which
// flummoxes our attmpt to delay the activation point here.)
delay.push(2);
}

30
src/test/compile-fail/borrowck/two-phase-sneaky.rs Normal file
View File

@ -0,0 +1,30 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// revisions: lxl nll
//[lxl]compile-flags: -Z borrowck=mir -Z two-phase-borrows
//[nll]compile-flags: -Z borrowck=mir -Z two-phase-borrows -Z nll
// This is the first counter-example from Niko's blog post
// smallcultfollowing.com/babysteps/blog/2017/03/01/nested-method-calls-via-two-phase-borrowing/
// of a danger for code to crash if we just turned off the check for whether
// a mutable-borrow aliases another borrow.
fn main() {
let mut v: Vec<String> = vec![format!("Hello, ")];
v[0].push_str({
v.push(format!("foo"));
//[lxl]~^ ERROR cannot borrow `v` as mutable more than once at a time [E0499]
//[nll]~^^ ERROR cannot borrow `v` as mutable more than once at a time [E0499]
"World!"
});
}

21
src/test/run-pass/borrowck/two-phase-baseline.rs Normal file
View File

@ -0,0 +1,21 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// revisions: lxl nll
//[lxl]compile-flags: -Z borrowck=mir -Z two-phase-borrows
//[nll]compile-flags: -Z borrowck=mir -Z two-phase-borrows -Z nll
// This is the "goto example" for why we want two phase borrows.
fn main() {
let mut v = vec![0, 1, 2];
v.push(v.len());
assert_eq!(v, [0, 1, 2, 3]);
}

27
src/test/run-pass/borrowck/two-phase-control-flow-split-before-activation.rs Normal file
View File

@ -0,0 +1,27 @@
// Copyright 2017 The Rust Project Developers. See the COPYRIGHT
// file at the top-level directory of this distribution and at
// http://rust-lang.org/COPYRIGHT.
//
// Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
// http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
// <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
// option. This file may not be copied, modified, or distributed
// except according to those terms.
// revisions: lxl nll
//[lxl]compile-flags: -Z borrowck=mir -Z two-phase-borrows
//[nll]compile-flags: -Z borrowck=mir -Z two-phase-borrows -Z nll
fn main() {
let mut a = 0;
let mut b = 0;
let p = if maybe() {
&mut a
} else {
&mut b
};
use_(p);
}
fn maybe() -> bool { false }
fn use_<T>(_: T) { }