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Rollup merge of rust-lang#125652 - amandasystems:you-dropped-somethin…
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…g, r=oli-obk

Revert propagation of drop-live information from Polonius

rust-lang#64749 introduced a flow of drop-use data from Polonius to `LivenessResults::add_extra_drop_facts()`, which makes `LivenessResults` agree with Polonius on liveness in the presence of free regions that may be dropped. Later changes accidentally removed this flow. This PR restores it.
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jieyouxu authored May 31, 2024
2 parents 2a2c29a + 8066ebc commit e895233
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Showing 4 changed files with 30 additions and 35 deletions.
11 changes: 3 additions & 8 deletions compiler/rustc_borrowck/src/type_check/liveness/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -14,7 +14,6 @@ use std::rc::Rc;
use crate::{
constraints::OutlivesConstraintSet,
facts::{AllFacts, AllFactsExt},
location::LocationTable,
region_infer::values::LivenessValues,
universal_regions::UniversalRegions,
};
Expand All @@ -39,7 +38,6 @@ pub(super) fn generate<'mir, 'tcx>(
elements: &Rc<DenseLocationMap>,
flow_inits: &mut ResultsCursor<'mir, 'tcx, MaybeInitializedPlaces<'mir, 'tcx>>,
move_data: &MoveData<'tcx>,
location_table: &LocationTable,
use_polonius: bool,
) {
debug!("liveness::generate");
Expand All @@ -53,11 +51,9 @@ pub(super) fn generate<'mir, 'tcx>(
compute_relevant_live_locals(typeck.tcx(), &free_regions, body);
let facts_enabled = use_polonius || AllFacts::enabled(typeck.tcx());

let polonius_drop_used = facts_enabled.then(|| {
let mut drop_used = Vec::new();
polonius::populate_access_facts(typeck, body, location_table, move_data, &mut drop_used);
drop_used
});
if facts_enabled {
polonius::populate_access_facts(typeck, body, move_data);
};

trace::trace(
typeck,
Expand All @@ -67,7 +63,6 @@ pub(super) fn generate<'mir, 'tcx>(
move_data,
relevant_live_locals,
boring_locals,
polonius_drop_used,
);

// Mark regions that should be live where they appear within rvalues or within a call: like
Expand Down
9 changes: 1 addition & 8 deletions compiler/rustc_borrowck/src/type_check/liveness/polonius.rs
Original file line number Diff line number Diff line change
Expand Up @@ -85,13 +85,10 @@ impl<'a, 'tcx> Visitor<'tcx> for UseFactsExtractor<'a, 'tcx> {
pub(super) fn populate_access_facts<'a, 'tcx>(
typeck: &mut TypeChecker<'a, 'tcx>,
body: &Body<'tcx>,
location_table: &LocationTable,
move_data: &MoveData<'tcx>,
//FIXME: this is not mutated, but expected to be modified as
// out param, bug?
dropped_at: &mut Vec<(Local, Location)>,
) {
debug!("populate_access_facts()");
let location_table = typeck.borrowck_context.location_table;

if let Some(facts) = typeck.borrowck_context.all_facts.as_mut() {
let mut extractor = UseFactsExtractor {
Expand All @@ -104,10 +101,6 @@ pub(super) fn populate_access_facts<'a, 'tcx>(
};
extractor.visit_body(body);

facts.var_dropped_at.extend(
dropped_at.iter().map(|&(local, location)| (local, location_table.mid_index(location))),
);

for (local, local_decl) in body.local_decls.iter_enumerated() {
debug!(
"add use_of_var_derefs_origin facts - local={:?}, type={:?}",
Expand Down
35 changes: 25 additions & 10 deletions compiler/rustc_borrowck/src/type_check/liveness/trace.rs
Original file line number Diff line number Diff line change
Expand Up @@ -16,6 +16,7 @@ use rustc_mir_dataflow::impls::MaybeInitializedPlaces;
use rustc_mir_dataflow::move_paths::{HasMoveData, MoveData, MovePathIndex};
use rustc_mir_dataflow::ResultsCursor;

use crate::location::RichLocation;
use crate::{
region_infer::values::{self, LiveLoans},
type_check::liveness::local_use_map::LocalUseMap,
Expand Down Expand Up @@ -46,7 +47,6 @@ pub(super) fn trace<'mir, 'tcx>(
move_data: &MoveData<'tcx>,
relevant_live_locals: Vec<Local>,
boring_locals: Vec<Local>,
polonius_drop_used: Option<Vec<(Local, Location)>>,
) {
let local_use_map = &LocalUseMap::build(&relevant_live_locals, elements, body);

Expand Down Expand Up @@ -93,9 +93,7 @@ pub(super) fn trace<'mir, 'tcx>(

let mut results = LivenessResults::new(cx);

if let Some(drop_used) = polonius_drop_used {
results.add_extra_drop_facts(drop_used, relevant_live_locals.iter().copied().collect())
}
results.add_extra_drop_facts(&relevant_live_locals);

results.compute_for_all_locals(relevant_live_locals);

Expand Down Expand Up @@ -218,21 +216,38 @@ impl<'me, 'typeck, 'flow, 'tcx> LivenessResults<'me, 'typeck, 'flow, 'tcx> {
///
/// Add facts for all locals with free regions, since regions may outlive
/// the function body only at certain nodes in the CFG.
fn add_extra_drop_facts(
&mut self,
drop_used: Vec<(Local, Location)>,
relevant_live_locals: FxIndexSet<Local>,
) {
fn add_extra_drop_facts(&mut self, relevant_live_locals: &[Local]) -> Option<()> {
let drop_used = self
.cx
.typeck
.borrowck_context
.all_facts
.as_ref()
.map(|facts| facts.var_dropped_at.clone())?;

let relevant_live_locals: FxIndexSet<_> = relevant_live_locals.iter().copied().collect();

let locations = IntervalSet::new(self.cx.elements.num_points());

for (local, location) in drop_used {
for (local, location_index) in drop_used {
if !relevant_live_locals.contains(&local) {
let local_ty = self.cx.body.local_decls[local].ty;
if local_ty.has_free_regions() {
let location = match self
.cx
.typeck
.borrowck_context
.location_table
.to_location(location_index)
{
RichLocation::Start(l) => l,
RichLocation::Mid(l) => l,
};
self.cx.add_drop_live_facts_for(local, local_ty, &[location], &locations);
}
}
}
Some(())
}

/// Clear the value of fields that are "per local variable".
Expand Down
10 changes: 1 addition & 9 deletions compiler/rustc_borrowck/src/type_check/mod.rs
Original file line number Diff line number Diff line change
Expand Up @@ -188,15 +188,7 @@ pub(crate) fn type_check<'mir, 'tcx>(
checker.equate_inputs_and_outputs(body, universal_regions, &normalized_inputs_and_output);
checker.check_signature_annotation(body);

liveness::generate(
&mut checker,
body,
elements,
flow_inits,
move_data,
location_table,
use_polonius,
);
liveness::generate(&mut checker, body, elements, flow_inits, move_data, use_polonius);

translate_outlives_facts(&mut checker);
let opaque_type_values = infcx.take_opaque_types();
Expand Down

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