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refactor access fact generation
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- use consistent names
- inline single use functions
- dedupe and simplify some paths
- fix fact generation timer activity: it was missing the walk and
  extraction process
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@lqd
lqd committed Dec 14, 2024
1 parent b0e04d5 commit 585c71f
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Showing 3 changed files with 67 additions and 80 deletions.
2 changes: 1 addition & 1 deletion compiler/rustc_borrowck/src/type_check/liveness/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -45,7 +45,7 @@ pub(super) fn generate<'a, 'tcx>(
let (relevant_live_locals, boring_locals) =
compute_relevant_live_locals(typeck.tcx(), &free_regions, body);

polonius::populate_access_facts(typeck, body, move_data);
polonius::emit_access_facts(typeck, body, move_data);

trace::trace(
typeck,
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143 changes: 65 additions & 78 deletions compiler/rustc_borrowck/src/type_check/liveness/polonius.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -11,88 +11,19 @@ use crate::location::{LocationIndex, LocationTable};
type VarPointRelation = Vec<(Local, LocationIndex)>;
type PathPointRelation = Vec<(MovePathIndex, LocationIndex)>;

struct UseFactsExtractor<'a, 'tcx> {
var_defined_at: &'a mut VarPointRelation,
var_used_at: &'a mut VarPointRelation,
location_table: &'a LocationTable,
var_dropped_at: &'a mut VarPointRelation,
move_data: &'a MoveData<'tcx>,
path_accessed_at_base: &'a mut PathPointRelation,
}

// A Visitor to walk through the MIR and extract point-wise facts
impl<'tcx> UseFactsExtractor<'_, 'tcx> {
fn location_to_index(&self, location: Location) -> LocationIndex {
self.location_table.mid_index(location)
}

fn insert_def(&mut self, local: Local, location: Location) {
debug!("UseFactsExtractor::insert_def()");
self.var_defined_at.push((local, self.location_to_index(location)));
}

fn insert_use(&mut self, local: Local, location: Location) {
debug!("UseFactsExtractor::insert_use()");
self.var_used_at.push((local, self.location_to_index(location)));
}

fn insert_drop_use(&mut self, local: Local, location: Location) {
debug!("UseFactsExtractor::insert_drop_use()");
self.var_dropped_at.push((local, self.location_to_index(location)));
}

fn insert_path_access(&mut self, path: MovePathIndex, location: Location) {
debug!("UseFactsExtractor::insert_path_access({:?}, {:?})", path, location);
self.path_accessed_at_base.push((path, self.location_to_index(location)));
}

fn place_to_mpi(&self, place: &Place<'tcx>) -> Option<MovePathIndex> {
match self.move_data.rev_lookup.find(place.as_ref()) {
LookupResult::Exact(mpi) => Some(mpi),
LookupResult::Parent(mmpi) => mmpi,
}
}
}

impl<'a, 'tcx> Visitor<'tcx> for UseFactsExtractor<'a, 'tcx> {
fn visit_local(&mut self, local: Local, context: PlaceContext, location: Location) {
match def_use::categorize(context) {
Some(DefUse::Def) => self.insert_def(local, location),
Some(DefUse::Use) => self.insert_use(local, location),
Some(DefUse::Drop) => self.insert_drop_use(local, location),
_ => (),
}
}

fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
self.super_place(place, context, location);
match context {
PlaceContext::NonMutatingUse(_) => {
if let Some(mpi) = self.place_to_mpi(place) {
self.insert_path_access(mpi, location);
}
}

PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
if let Some(mpi) = self.place_to_mpi(place) {
self.insert_path_access(mpi, location);
}
}
_ => (),
}
}
}

pub(super) fn populate_access_facts<'a, 'tcx>(
/// Emit polonius facts for variable defs, uses, drops, and path accesses.
pub(super) fn emit_access_facts<'a, 'tcx>(
typeck: &mut TypeChecker<'a, 'tcx>,
body: &Body<'tcx>,
move_data: &MoveData<'tcx>,
) {
if let Some(facts) = typeck.all_facts.as_mut() {
debug!("populate_access_facts()");
debug!("emit_access_facts()");

let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
let location_table = typeck.location_table;

let mut extractor = UseFactsExtractor {
let mut extractor = AccessFactsExtractor {
var_defined_at: &mut facts.var_defined_at,
var_used_at: &mut facts.var_used_at,
var_dropped_at: &mut facts.var_dropped_at,
Expand All @@ -107,7 +38,6 @@ pub(super) fn populate_access_facts<'a, 'tcx>(
"add use_of_var_derefs_origin facts - local={:?}, type={:?}",
local, local_decl.ty
);
let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
let universal_regions = &typeck.universal_regions;
typeck.infcx.tcx.for_each_free_region(&local_decl.ty, |region| {
let region_vid = universal_regions.to_region_vid(region);
Expand All @@ -119,12 +49,12 @@ pub(super) fn populate_access_facts<'a, 'tcx>(

/// For every potentially drop()-touched region `region` in `local`'s type
/// (`kind`), emit a Polonius `use_of_var_derefs_origin(local, origin)` fact.
pub(super) fn add_drop_of_var_derefs_origin<'tcx>(
pub(super) fn emit_drop_facts<'tcx>(
typeck: &mut TypeChecker<'_, 'tcx>,
local: Local,
kind: &GenericArg<'tcx>,
) {
debug!("add_drop_of_var_derefs_origin(local={:?}, kind={:?}", local, kind);
debug!("emit_drop_facts(local={:?}, kind={:?}", local, kind);
if let Some(facts) = typeck.all_facts.as_mut() {
let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
let universal_regions = &typeck.universal_regions;
Expand All @@ -134,3 +64,60 @@ pub(super) fn add_drop_of_var_derefs_origin<'tcx>(
});
}
}

/// MIR visitor extracting point-wise facts about accesses.
struct AccessFactsExtractor<'a, 'tcx> {
var_defined_at: &'a mut VarPointRelation,
var_used_at: &'a mut VarPointRelation,
location_table: &'a LocationTable,
var_dropped_at: &'a mut VarPointRelation,
move_data: &'a MoveData<'tcx>,
path_accessed_at_base: &'a mut PathPointRelation,
}

impl<'tcx> AccessFactsExtractor<'_, 'tcx> {
fn location_to_index(&self, location: Location) -> LocationIndex {
self.location_table.mid_index(location)
}
}

impl<'a, 'tcx> Visitor<'tcx> for AccessFactsExtractor<'a, 'tcx> {
fn visit_local(&mut self, local: Local, context: PlaceContext, location: Location) {
match def_use::categorize(context) {
Some(DefUse::Def) => {
debug!("AccessFactsExtractor - emit def");
self.var_defined_at.push((local, self.location_to_index(location)));
}
Some(DefUse::Use) => {
debug!("AccessFactsExtractor - emit use");
self.var_used_at.push((local, self.location_to_index(location)));
}
Some(DefUse::Drop) => {
debug!("AccessFactsExtractor - emit drop");
self.var_dropped_at.push((local, self.location_to_index(location)));
}
_ => (),
}
}

fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
self.super_place(place, context, location);

match context {
PlaceContext::NonMutatingUse(_)
| PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
let path = match self.move_data.rev_lookup.find(place.as_ref()) {
LookupResult::Exact(path) | LookupResult::Parent(Some(path)) => path,
_ => {
// There's no path access to emit.
return;
}
};
debug!("AccessFactsExtractor - emit path access ({path:?}, {location:?})");
self.path_accessed_at_base.push((path, self.location_to_index(location)));
}

_ => {}
}
}
}
2 changes: 1 addition & 1 deletion compiler/rustc_borrowck/src/type_check/liveness/trace.rs
View file
Original file line number Diff line number Diff line change
Expand Up @@ -590,7 +590,7 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
// the destructor and must be live at this point.
for &kind in &drop_data.dropck_result.kinds {
Self::make_all_regions_live(self.elements, self.typeck, kind, live_at);
polonius::add_drop_of_var_derefs_origin(self.typeck, dropped_local, &kind);
polonius::emit_drop_facts(self.typeck, dropped_local, &kind);
}
}

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