[experimental, do not merge!] a faster implementation of Polonius

compiler/rustc_borrowck/src/borrow_set.rs

@@ -1,3 +1,4 @@
+use std::cell::OnceCell;
 use std::fmt;
 use std::ops::Index;
 
@@ -84,6 +85,7 @@ pub struct BorrowData<'tcx> {
  pub(crate) borrowed_place: mir::Place<'tcx>,
  /// Place to which the borrow was stored
  pub(crate) assigned_place: mir::Place<'tcx>,
+ pub(crate) dependent_regions: OnceCell<DenseBitSet<RegionVid>>,
 }
 
 // These methods are public to support borrowck consumers.
@@ -261,6 +263,7 @@ impl<'a, 'tcx> Visitor<'tcx> for GatherBorrows<'a, 'tcx> {
  activation_location: TwoPhaseActivation::NotTwoPhase,
  borrowed_place,
  assigned_place: *assigned_place,
+ dependent_regions: OnceCell::new(),
  };
  let (idx, _) = self.location_map.insert_full(location, borrow);
  let idx = BorrowIndex::from(idx);

compiler/rustc_borrowck/src/dataflow.rs

@@ -301,6 +301,7 @@ struct PoloniusOutOfScopePrecomputer<'a, 'tcx> {
  loans_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
 }
 
+#[expect(dead_code)]
 impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
  fn compute(
  body: &Body<'tcx>,
@@ -476,11 +477,18 @@ impl<'a, 'tcx> Borrows<'a, 'tcx> {
  if !tcx.sess.opts.unstable_opts.polonius.is_next_enabled() {
  calculate_borrows_out_of_scope_at_location(body, regioncx, borrow_set)
  } else {
- PoloniusOutOfScopePrecomputer::compute(body, regioncx, borrow_set)
+ unimplemented!() // This should probably be removed.
  };
  Borrows { tcx, body, borrow_set, borrows_out_of_scope_at_location }
  }
 
+ /// A dummy `Borrows` with no useful information.
+ ///
+ /// Used for Polonius which doesn't need this.
+ pub fn dummy(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, borrow_set: &'a BorrowSet<'tcx>) -> Self {
+ Borrows { tcx, body, borrow_set, borrows_out_of_scope_at_location: Default::default() }
+ }
+
  /// Add all borrows to the kill set, if those borrows are out of scope at `location`.
  /// That means they went out of a nonlexical scope
  fn kill_loans_out_of_scope_at_location(
@@ -563,6 +571,10 @@ impl<'tcx> rustc_mir_dataflow::Analysis<'tcx> for Borrows<'_, 'tcx> {
  const NAME: &'static str = "borrows";
 
  fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
+ if !self.tcx.sess.opts.unstable_opts.polonius.is_legacy_enabled() {
+ return DenseBitSet::new_empty(0);
+ }
+
  // bottom = nothing is reserved or activated yet;
  DenseBitSet::new_empty(self.borrow_set.len())
  }
@@ -578,6 +590,10 @@ impl<'tcx> rustc_mir_dataflow::Analysis<'tcx> for Borrows<'_, 'tcx> {
  _statement: &mir::Statement<'tcx>,
  location: Location,
  ) {
+ if !self.tcx.sess.opts.unstable_opts.polonius.is_legacy_enabled() {
+ return;
+ }
+
  self.kill_loans_out_of_scope_at_location(state, location);
  }
 
@@ -587,6 +603,10 @@ impl<'tcx> rustc_mir_dataflow::Analysis<'tcx> for Borrows<'_, 'tcx> {
  stmt: &mir::Statement<'tcx>,
  location: Location,
  ) {
+ if !self.tcx.sess.opts.unstable_opts.polonius.is_legacy_enabled() {
+ return;
+ }
+
  match &stmt.kind {
  mir::StatementKind::Assign(box (lhs, rhs)) => {
  if let mir::Rvalue::Ref(_, _, place) = rhs {
@@ -636,6 +656,10 @@ impl<'tcx> rustc_mir_dataflow::Analysis<'tcx> for Borrows<'_, 'tcx> {
  _terminator: &mir::Terminator<'tcx>,
  location: Location,
  ) {
+ if !self.tcx.sess.opts.unstable_opts.polonius.is_legacy_enabled() {
+ return;
+ }
+
  self.kill_loans_out_of_scope_at_location(state, location);
  }
 
@@ -645,6 +669,10 @@ impl<'tcx> rustc_mir_dataflow::Analysis<'tcx> for Borrows<'_, 'tcx> {
  terminator: &'mir mir::Terminator<'tcx>,
  _location: Location,
  ) -> TerminatorEdges<'mir, 'tcx> {
+ if !self.tcx.sess.opts.unstable_opts.polonius.is_legacy_enabled() {
+ return terminator.edges();
+ }
+
  if let mir::TerminatorKind::InlineAsm { operands, .. } = &terminator.kind {
  for op in operands {
  if let mir::InlineAsmOperand::Out { place: Some(place), .. }

compiler/rustc_borrowck/src/diagnostics/explain_borrow.rs

@@ -632,8 +632,8 @@ impl<'tcx> MirBorrowckCtxt<'_, '_, 'tcx> {
  // We want to focus on relevant live locals in diagnostics, so when polonius is enabled, we
  // ensure that we don't emit live boring locals as explanations.
  let is_local_boring = |local| {
- if let Some(polonius_diagnostics) = self.polonius_diagnostics {
- polonius_diagnostics.boring_nll_locals.contains(&local)
+ if let Some(polonius) = &self.polonius {
+ polonius.pcx.is_boring_local(local)
  } else {
  assert!(!tcx.sess.opts.unstable_opts.polonius.is_next_enabled());