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Auto merge of #69156 - ecstatic-morse:unified-dataflow-impls2, r=eddyb
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Use `ResultsCursor` for `elaborate_drops`

Some cleanup after #68241. The old code was using a custom cursor-like struct called `InitializationData`.
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@bors
bors committed Feb 16, 2020
2 parents 2a0d1cb + 26451d0 commit 8040bc9
Showing 1 changed file with 41 additions and 83 deletions.
124 changes: 41 additions & 83 deletions src/librustc_mir/transform/elaborate_drops.rs
View file
Original file line number Diff line number Diff line change
@@ -1,8 +1,8 @@
use crate::dataflow;
use crate::dataflow::generic::{Analysis, Results};
use crate::dataflow::generic::{Analysis, ResultsCursor};
use crate::dataflow::move_paths::{LookupResult, MoveData, MovePathIndex};
use crate::dataflow::on_lookup_result_bits;
use crate::dataflow::MoveDataParamEnv;
use crate::dataflow::{drop_flag_effects_for_location, on_lookup_result_bits};
use crate::dataflow::{on_all_children_bits, on_all_drop_children_bits};
use crate::dataflow::{MaybeInitializedPlaces, MaybeUninitializedPlaces};
use crate::transform::{MirPass, MirSource};
Expand Down Expand Up @@ -41,22 +41,23 @@ impl<'tcx> MirPass<'tcx> for ElaborateDrops {
let env = MoveDataParamEnv { move_data, param_env };
let dead_unwinds = find_dead_unwinds(tcx, body, def_id, &env);

let flow_inits = MaybeInitializedPlaces::new(tcx, body, &env)
let inits = MaybeInitializedPlaces::new(tcx, body, &env)
.into_engine(tcx, body, def_id)
.dead_unwinds(&dead_unwinds)
.iterate_to_fixpoint();
.iterate_to_fixpoint()
.into_results_cursor(body);

let flow_uninits = MaybeUninitializedPlaces::new(tcx, body, &env)
let uninits = MaybeUninitializedPlaces::new(tcx, body, &env)
.into_engine(tcx, body, def_id)
.dead_unwinds(&dead_unwinds)
.iterate_to_fixpoint();
.iterate_to_fixpoint()
.into_results_cursor(body);

ElaborateDropsCtxt {
tcx,
body,
env: &env,
flow_inits,
flow_uninits,
init_data: InitializationData { inits, uninits },
drop_flags: Default::default(),
patch: MirPatch::new(body),
}
Expand All @@ -79,25 +80,18 @@ fn find_dead_unwinds<'tcx>(
// We only need to do this pass once, because unwind edges can only
// reach cleanup blocks, which can't have unwind edges themselves.
let mut dead_unwinds = BitSet::new_empty(body.basic_blocks().len());
let flow_inits = MaybeInitializedPlaces::new(tcx, body, &env)
let mut flow_inits = MaybeInitializedPlaces::new(tcx, body, &env)
.into_engine(tcx, body, def_id)
.iterate_to_fixpoint();
.iterate_to_fixpoint()
.into_results_cursor(body);
for (bb, bb_data) in body.basic_blocks().iter_enumerated() {
let location = match bb_data.terminator().kind {
TerminatorKind::Drop { ref location, unwind: Some(_), .. }
| TerminatorKind::DropAndReplace { ref location, unwind: Some(_), .. } => location,
_ => continue,
};

let mut init_data = InitializationData {
live: flow_inits.entry_set_for_block(bb).clone(),
dead: BitSet::new_empty(env.move_data.move_paths.len()),
};
debug!("find_dead_unwinds @ {:?}: {:?}; init_data={:?}", bb, bb_data, init_data.live);
for stmt in 0..bb_data.statements.len() {
let loc = Location { block: bb, statement_index: stmt };
init_data.apply_location(tcx, body, env, loc);
}
debug!("find_dead_unwinds @ {:?}: {:?}", bb, bb_data);

let path = match env.move_data.rev_lookup.find(location.as_ref()) {
LookupResult::Exact(e) => e,
Expand All @@ -107,12 +101,18 @@ fn find_dead_unwinds<'tcx>(
}
};

debug!("find_dead_unwinds @ {:?}: path({:?})={:?}", bb, location, path);
flow_inits.seek_before(body.terminator_loc(bb));
debug!(
"find_dead_unwinds @ {:?}: path({:?})={:?}; init_data={:?}",
bb,
location,
path,
flow_inits.get()
);

let mut maybe_live = false;
on_all_drop_children_bits(tcx, body, &env, path, |child| {
let (child_maybe_live, _) = init_data.state(child);
maybe_live |= child_maybe_live;
maybe_live |= flow_inits.contains(child);
});

debug!("find_dead_unwinds @ {:?}: maybe_live={}", bb, maybe_live);
Expand All @@ -124,41 +124,23 @@ fn find_dead_unwinds<'tcx>(
dead_unwinds
}

struct InitializationData {
live: BitSet<MovePathIndex>,
dead: BitSet<MovePathIndex>,
struct InitializationData<'mir, 'tcx> {
inits: ResultsCursor<'mir, 'tcx, MaybeInitializedPlaces<'mir, 'tcx>>,
uninits: ResultsCursor<'mir, 'tcx, MaybeUninitializedPlaces<'mir, 'tcx>>,
}

impl InitializationData {
fn apply_location<'tcx>(
&mut self,
tcx: TyCtxt<'tcx>,
body: &Body<'tcx>,
env: &MoveDataParamEnv<'tcx>,
loc: Location,
) {
drop_flag_effects_for_location(tcx, body, env, loc, |path, df| {
debug!("at location {:?}: setting {:?} to {:?}", loc, path, df);
match df {
DropFlagState::Present => {
self.live.insert(path);
self.dead.remove(path);
}
DropFlagState::Absent => {
self.dead.insert(path);
self.live.remove(path);
}
}
});
impl InitializationData<'_, '_> {
fn seek_before(&mut self, loc: Location) {
self.inits.seek_before(loc);
self.uninits.seek_before(loc);
}

fn state(&self, path: MovePathIndex) -> (bool, bool) {
(self.live.contains(path), self.dead.contains(path))
fn maybe_live_dead(&self, path: MovePathIndex) -> (bool, bool) {
(self.inits.contains(path), self.uninits.contains(path))
}
}

struct Elaborator<'a, 'b, 'tcx> {
init_data: &'a InitializationData,
ctxt: &'a mut ElaborateDropsCtxt<'b, 'tcx>,
}

Expand Down Expand Up @@ -189,13 +171,13 @@ impl<'a, 'b, 'tcx> DropElaborator<'a, 'tcx> for Elaborator<'a, 'b, 'tcx> {

fn drop_style(&self, path: Self::Path, mode: DropFlagMode) -> DropStyle {
let ((maybe_live, maybe_dead), multipart) = match mode {
DropFlagMode::Shallow => (self.init_data.state(path), false),
DropFlagMode::Shallow => (self.ctxt.init_data.maybe_live_dead(path), false),
DropFlagMode::Deep => {
let mut some_live = false;
let mut some_dead = false;
let mut children_count = 0;
on_all_drop_children_bits(self.tcx(), self.body(), self.ctxt.env, path, |child| {
let (live, dead) = self.init_data.state(child);
let (live, dead) = self.ctxt.init_data.maybe_live_dead(child);
debug!("elaborate_drop: state({:?}) = {:?}", child, (live, dead));
some_live |= live;
some_dead |= dead;
Expand Down Expand Up @@ -269,8 +251,7 @@ struct ElaborateDropsCtxt<'a, 'tcx> {
tcx: TyCtxt<'tcx>,
body: &'a Body<'tcx>,
env: &'a MoveDataParamEnv<'tcx>,
flow_inits: Results<'tcx, MaybeInitializedPlaces<'a, 'tcx>>,
flow_uninits: Results<'tcx, MaybeUninitializedPlaces<'a, 'tcx>>,
init_data: InitializationData<'a, 'tcx>,
drop_flags: FxHashMap<MovePathIndex, Local>,
patch: MirPatch<'tcx>,
}
Expand All @@ -284,25 +265,6 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
self.env.param_env
}

// FIXME(ecstaticmorse): This duplicates `dataflow::ResultsCursor` but hardcodes the transfer
// function for `Maybe{Un,}InitializedPlaces` directly. It should be replaced by a a pair of
// `ResultsCursor`s.
fn initialization_data_at(&self, loc: Location) -> InitializationData {
let mut data = InitializationData {
live: self.flow_inits.entry_set_for_block(loc.block).to_owned(),
dead: self.flow_uninits.entry_set_for_block(loc.block).to_owned(),
};
for stmt in 0..loc.statement_index {
data.apply_location(
self.tcx,
self.body,
self.env,
Location { block: loc.block, statement_index: stmt },
);
}
data
}

fn create_drop_flag(&mut self, index: MovePathIndex, span: Span) {
let tcx = self.tcx;
let patch = &mut self.patch;
Expand Down Expand Up @@ -338,10 +300,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
_ => continue,
};

let init_data = self.initialization_data_at(Location {
block: bb,
statement_index: data.statements.len(),
});
self.init_data.seek_before(self.body.terminator_loc(bb));

let path = self.move_data().rev_lookup.find(location.as_ref());
debug!("collect_drop_flags: {:?}, place {:?} ({:?})", bb, location, path);
Expand All @@ -350,7 +309,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
LookupResult::Exact(e) => e,
LookupResult::Parent(None) => continue,
LookupResult::Parent(Some(parent)) => {
let (_maybe_live, maybe_dead) = init_data.state(parent);
let (_maybe_live, maybe_dead) = self.init_data.maybe_live_dead(parent);
if maybe_dead {
span_bug!(
terminator.source_info.span,
Expand All @@ -365,7 +324,7 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
};

on_all_drop_children_bits(self.tcx, self.body, self.env, path, |child| {
let (maybe_live, maybe_dead) = init_data.state(child);
let (maybe_live, maybe_dead) = self.init_data.maybe_live_dead(child);
debug!(
"collect_drop_flags: collecting {:?} from {:?}@{:?} - {:?}",
child,
Expand All @@ -388,10 +347,10 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
let resume_block = self.patch.resume_block();
match terminator.kind {
TerminatorKind::Drop { ref location, target, unwind } => {
let init_data = self.initialization_data_at(loc);
self.init_data.seek_before(loc);
match self.move_data().rev_lookup.find(location.as_ref()) {
LookupResult::Exact(path) => elaborate_drop(
&mut Elaborator { init_data: &init_data, ctxt: self },
&mut Elaborator { ctxt: self },
terminator.source_info,
location,
path,
Expand Down Expand Up @@ -471,10 +430,9 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> {
match self.move_data().rev_lookup.find(location.as_ref()) {
LookupResult::Exact(path) => {
debug!("elaborate_drop_and_replace({:?}) - tracked {:?}", terminator, path);
let init_data = self.initialization_data_at(loc);

self.init_data.seek_before(loc);
elaborate_drop(
&mut Elaborator { init_data: &init_data, ctxt: self },
&mut Elaborator { ctxt: self },
terminator.source_info,
location,
path,
Expand Down

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