Rollup merge of #131225 - nnethercote:rustc_borrowck-mm, r=lqd

`rustc_borrowck` memory management tweaks

Minor cleanups in `rustc_borrowck` relating to memory management.

r? `@lqd`

Author: workingjubilee

compiler/rustc_borrowck/src/consumers.rs

@@ -1,7 +1,5 @@
 //! This file provides API for compiler consumers.
 
-use std::rc::Rc;
-
 use rustc_hir::def_id::LocalDefId;
 use rustc_index::{IndexSlice, IndexVec};
 use rustc_middle::mir::{Body, Promoted};
@@ -65,10 +63,10 @@ pub struct BodyWithBorrowckFacts<'tcx> {
     /// The mir bodies of promoteds.
     pub promoted: IndexVec<Promoted, Body<'tcx>>,
     /// The set of borrows occurring in `body` with data about them.
-    pub borrow_set: Rc<BorrowSet<'tcx>>,
+    pub borrow_set: BorrowSet<'tcx>,
     /// Context generated during borrowck, intended to be passed to
     /// [`calculate_borrows_out_of_scope_at_location`].
-    pub region_inference_context: Rc<RegionInferenceContext<'tcx>>,
+    pub region_inference_context: RegionInferenceContext<'tcx>,
     /// The table that maps Polonius points to locations in the table.
     /// Populated when using [`ConsumerOptions::PoloniusInputFacts`]
     /// or [`ConsumerOptions::PoloniusOutputFacts`].
@@ -79,7 +77,7 @@ pub struct BodyWithBorrowckFacts<'tcx> {
     pub input_facts: Option<Box<PoloniusInput>>,
     /// Polonius output facts. Populated when using
     /// [`ConsumerOptions::PoloniusOutputFacts`].
-    pub output_facts: Option<Rc<PoloniusOutput>>,
+    pub output_facts: Option<Box<PoloniusOutput>>,
 }
 
 /// This function computes borrowck facts for the given body. The [`ConsumerOptions`]

compiler/rustc_borrowck/src/diagnostics/conflict_errors.rs

@@ -708,9 +708,9 @@ impl<'infcx, 'tcx> MirBorrowckCtxt<'_, 'infcx, 'tcx> {
         // for the branching codepaths that aren't covered, to point at them.
         let map = self.infcx.tcx.hir();
         let body = map.body_owned_by(self.mir_def_id());
-        let mut visitor =
-            ConditionVisitor { tcx: self.infcx.tcx, spans: &spans, name: &name, errors: vec![] };
+        let mut visitor = ConditionVisitor { tcx: self.infcx.tcx, spans, name, errors: vec![] };
         visitor.visit_body(&body);
+        let spans = visitor.spans;
 
         let mut show_assign_sugg = false;
         let isnt_initialized = if let InitializationRequiringAction::PartialAssignment
@@ -4465,20 +4465,20 @@ impl<'hir> Visitor<'hir> for BreakFinder {
 
 /// Given a set of spans representing statements initializing the relevant binding, visit all the
 /// function expressions looking for branching code paths that *do not* initialize the binding.
-struct ConditionVisitor<'b, 'tcx> {
+struct ConditionVisitor<'tcx> {
     tcx: TyCtxt<'tcx>,
-    spans: &'b [Span],
-    name: &'b str,
+    spans: Vec<Span>,
+    name: String,
     errors: Vec<(Span, String)>,
 }
 
-impl<'b, 'v, 'tcx> Visitor<'v> for ConditionVisitor<'b, 'tcx> {
+impl<'v, 'tcx> Visitor<'v> for ConditionVisitor<'tcx> {
     fn visit_expr(&mut self, ex: &'v hir::Expr<'v>) {
         match ex.kind {
             hir::ExprKind::If(cond, body, None) => {
                 // `if` expressions with no `else` that initialize the binding might be missing an
                 // `else` arm.
-                if ReferencedStatementsVisitor(self.spans).visit_expr(body).is_break() {
+                if ReferencedStatementsVisitor(&self.spans).visit_expr(body).is_break() {
                     self.errors.push((
                         cond.span,
                         format!(
@@ -4495,8 +4495,8 @@ impl<'b, 'v, 'tcx> Visitor<'v> for ConditionVisitor<'b, 'tcx> {
             hir::ExprKind::If(cond, body, Some(other)) => {
                 // `if` expressions where the binding is only initialized in one of the two arms
                 // might be missing a binding initialization.
-                let a = ReferencedStatementsVisitor(self.spans).visit_expr(body).is_break();
-                let b = ReferencedStatementsVisitor(self.spans).visit_expr(other).is_break();
+                let a = ReferencedStatementsVisitor(&self.spans).visit_expr(body).is_break();
+                let b = ReferencedStatementsVisitor(&self.spans).visit_expr(other).is_break();
                 match (a, b) {
                     (true, true) | (false, false) => {}
                     (true, false) => {
@@ -4536,7 +4536,7 @@ impl<'b, 'v, 'tcx> Visitor<'v> for ConditionVisitor<'b, 'tcx> {
                 // arms might be missing an initialization.
                 let results: Vec<bool> = arms
                     .iter()
-                    .map(|arm| ReferencedStatementsVisitor(self.spans).visit_arm(arm).is_break())
+                    .map(|arm| ReferencedStatementsVisitor(&self.spans).visit_arm(arm).is_break())
                     .collect();
                 if results.iter().any(|x| *x) && !results.iter().all(|x| *x) {
                     for (arm, seen) in arms.iter().zip(results) {

compiler/rustc_borrowck/src/diagnostics/find_use.rs

@@ -1,5 +1,4 @@
 use std::collections::VecDeque;
-use std::rc::Rc;
 
 use rustc_data_structures::fx::FxIndexSet;
 use rustc_middle::mir::visit::{MirVisitable, PlaceContext, Visitor};
@@ -11,7 +10,7 @@ use crate::region_infer::{Cause, RegionInferenceContext};
 
 pub(crate) fn find<'tcx>(
     body: &Body<'tcx>,
-    regioncx: &Rc<RegionInferenceContext<'tcx>>,
+    regioncx: &RegionInferenceContext<'tcx>,
     tcx: TyCtxt<'tcx>,
     region_vid: RegionVid,
     start_point: Location,
@@ -23,7 +22,7 @@ pub(crate) fn find<'tcx>(
 
 struct UseFinder<'a, 'tcx> {
     body: &'a Body<'tcx>,
-    regioncx: &'a Rc<RegionInferenceContext<'tcx>>,
+    regioncx: &'a RegionInferenceContext<'tcx>,
     tcx: TyCtxt<'tcx>,
     region_vid: RegionVid,
     start_point: Location,

compiler/rustc_borrowck/src/lib.rs

@@ -19,7 +19,6 @@ use std::cell::RefCell;
 use std::collections::BTreeMap;
 use std::marker::PhantomData;
 use std::ops::Deref;
-use std::rc::Rc;
 
 use consumers::{BodyWithBorrowckFacts, ConsumerOptions};
 use rustc_data_structures::fx::{FxIndexMap, FxIndexSet};
@@ -200,8 +199,7 @@ fn do_mir_borrowck<'tcx>(
         .into_results_cursor(body);
 
     let locals_are_invalidated_at_exit = tcx.hir().body_owner_kind(def).is_fn_or_closure();
-    let borrow_set =
-        Rc::new(BorrowSet::build(tcx, body, locals_are_invalidated_at_exit, &move_data));
+    let borrow_set = BorrowSet::build(tcx, body, locals_are_invalidated_at_exit, &move_data);
 
     // Compute non-lexical lifetimes.
     let nll::NllOutput {
@@ -245,8 +243,6 @@ fn do_mir_borrowck<'tcx>(
     // usage significantly on some benchmarks.
     drop(flow_inits);
 
-    let regioncx = Rc::new(regioncx);
-
     let flow_borrows = Borrows::new(tcx, body, &regioncx, &borrow_set)
         .into_engine(tcx, body)
         .pass_name("borrowck")
@@ -288,10 +284,10 @@ fn do_mir_borrowck<'tcx>(
             access_place_error_reported: Default::default(),
             reservation_error_reported: Default::default(),
             uninitialized_error_reported: Default::default(),
-            regioncx: regioncx.clone(),
+            regioncx: &regioncx,
             used_mut: Default::default(),
             used_mut_upvars: SmallVec::new(),
-            borrow_set: Rc::clone(&borrow_set),
+            borrow_set: &borrow_set,
             upvars: &[],
             local_names: IndexVec::from_elem(None, &promoted_body.local_decls),
             region_names: RefCell::default(),
@@ -329,10 +325,10 @@ fn do_mir_borrowck<'tcx>(
         access_place_error_reported: Default::default(),
         reservation_error_reported: Default::default(),
         uninitialized_error_reported: Default::default(),
-        regioncx: Rc::clone(&regioncx),
+        regioncx: &regioncx,
         used_mut: Default::default(),
         used_mut_upvars: SmallVec::new(),
-        borrow_set: Rc::clone(&borrow_set),
+        borrow_set: &borrow_set,
         upvars: tcx.closure_captures(def),
         local_names,
         region_names: RefCell::default(),
@@ -569,10 +565,10 @@ struct MirBorrowckCtxt<'a, 'infcx, 'tcx> {
     used_mut_upvars: SmallVec<[FieldIdx; 8]>,
     /// Region inference context. This contains the results from region inference and lets us e.g.
     /// find out which CFG points are contained in each borrow region.
-    regioncx: Rc<RegionInferenceContext<'tcx>>,
+    regioncx: &'a RegionInferenceContext<'tcx>,
 
     /// The set of borrows extracted from the MIR
-    borrow_set: Rc<BorrowSet<'tcx>>,
+    borrow_set: &'a BorrowSet<'tcx>,
 
     /// Information about upvars not necessarily preserved in types or MIR
     upvars: &'tcx [&'tcx ty::CapturedPlace<'tcx>],
@@ -588,7 +584,7 @@ struct MirBorrowckCtxt<'a, 'infcx, 'tcx> {
     next_region_name: RefCell<usize>,
 
     /// Results of Polonius analysis.
-    polonius_output: Option<Rc<PoloniusOutput>>,
+    polonius_output: Option<Box<PoloniusOutput>>,
 
     diags: diags::BorrowckDiags<'infcx, 'tcx>,
     move_errors: Vec<MoveError<'tcx>>,
@@ -800,9 +796,8 @@ impl<'a, 'tcx, R> rustc_mir_dataflow::ResultsVisitor<'a, 'tcx, R>
             TerminatorKind::Yield { value: _, resume: _, resume_arg: _, drop: _ } => {
                 if self.movable_coroutine {
                     // Look for any active borrows to locals
-                    let borrow_set = self.borrow_set.clone();
                     for i in state.borrows.iter() {
-                        let borrow = &borrow_set[i];
+                        let borrow = &self.borrow_set[i];
                         self.check_for_local_borrow(borrow, span);
                     }
                 }
@@ -816,9 +811,8 @@ impl<'a, 'tcx, R> rustc_mir_dataflow::ResultsVisitor<'a, 'tcx, R>
                 // Often, the storage will already have been killed by an explicit
                 // StorageDead, but we don't always emit those (notably on unwind paths),
                 // so this "extra check" serves as a kind of backup.
-                let borrow_set = self.borrow_set.clone();
                 for i in state.borrows.iter() {
-                    let borrow = &borrow_set[i];
+                    let borrow = &self.borrow_set[i];
                     self.check_for_invalidation_at_exit(loc, borrow, span);
                 }
             }
@@ -1037,13 +1031,12 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
         state: &BorrowckDomain<'a, 'tcx>,
     ) -> bool {
         let mut error_reported = false;
-        let borrow_set = Rc::clone(&self.borrow_set);
 
         // Use polonius output if it has been enabled.
         let mut polonius_output;
         let borrows_in_scope = if let Some(polonius) = &self.polonius_output {
             let location = self.location_table.start_index(location);
-            polonius_output = BitSet::new_empty(borrow_set.len());
+            polonius_output = BitSet::new_empty(self.borrow_set.len());
             for &idx in polonius.errors_at(location) {
                 polonius_output.insert(idx);
             }
@@ -1057,7 +1050,7 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
             self.infcx.tcx,
             self.body,
             (sd, place_span.0),
-            &borrow_set,
+            self.borrow_set,
             |borrow_index| borrows_in_scope.contains(borrow_index),
             |this, borrow_index, borrow| match (rw, borrow.kind) {
                 // Obviously an activation is compatible with its own
@@ -1580,9 +1573,8 @@ impl<'a, 'tcx> MirBorrowckCtxt<'a, '_, 'tcx> {
         // Two-phase borrow support: For each activation that is newly
         // generated at this statement, check if it interferes with
         // another borrow.
-        let borrow_set = self.borrow_set.clone();
-        for &borrow_index in borrow_set.activations_at_location(location) {
-            let borrow = &borrow_set[borrow_index];
+        for &borrow_index in self.borrow_set.activations_at_location(location) {
+            let borrow = &self.borrow_set[borrow_index];
 
             // only mutable borrows should be 2-phase
             assert!(match borrow.kind {

compiler/rustc_borrowck/src/nll.rs

@@ -42,7 +42,7 @@ pub(crate) struct NllOutput<'tcx> {
     pub regioncx: RegionInferenceContext<'tcx>,
     pub opaque_type_values: FxIndexMap<LocalDefId, OpaqueHiddenType<'tcx>>,
     pub polonius_input: Option<Box<AllFacts>>,
-    pub polonius_output: Option<Rc<PoloniusOutput>>,
+    pub polonius_output: Option<Box<PoloniusOutput>>,
     pub opt_closure_req: Option<ClosureRegionRequirements<'tcx>>,
     pub nll_errors: RegionErrors<'tcx>,
 }
@@ -98,7 +98,7 @@ pub(crate) fn compute_regions<'a, 'tcx>(
 
     let universal_regions = Rc::new(universal_regions);
 
-    let elements = &Rc::new(DenseLocationMap::new(body));
+    let elements = Rc::new(DenseLocationMap::new(body));
 
     // Run the MIR type-checker.
     let MirTypeckResults { constraints, universal_region_relations, opaque_type_values } =
@@ -107,13 +107,13 @@ pub(crate) fn compute_regions<'a, 'tcx>(
             param_env,
             body,
             promoted,
-            &universal_regions,
+            universal_regions.clone(),
             location_table,
             borrow_set,
             &mut all_facts,
             flow_inits,
             move_data,
-            elements,
+            elements.clone(),
             upvars,
         );
 
@@ -165,7 +165,7 @@ pub(crate) fn compute_regions<'a, 'tcx>(
         universe_causes,
         type_tests,
         liveness_constraints,
-        elements,
+        elements.clone(),
     );
 
     // If requested: dump NLL facts, and run legacy polonius analysis.
@@ -184,7 +184,7 @@ pub(crate) fn compute_regions<'a, 'tcx>(
             let algorithm = Algorithm::from_str(&algorithm).unwrap();
             debug!("compute_regions: using polonius algorithm {:?}", algorithm);
             let _prof_timer = infcx.tcx.prof.generic_activity("polonius_analysis");
-            Some(Rc::new(Output::compute(all_facts, algorithm, false)))
+            Some(Box::new(Output::compute(all_facts, algorithm, false)))
         } else {
             None
         }

compiler/rustc_borrowck/src/region_infer/mod.rs

@@ -407,7 +407,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         universe_causes: FxIndexMap<ty::UniverseIndex, UniverseInfo<'tcx>>,
         type_tests: Vec<TypeTest<'tcx>>,
         liveness_constraints: LivenessValues,
-        elements: &Rc<DenseLocationMap>,
+        elements: Rc<DenseLocationMap>,
     ) -> Self {
         debug!("universal_regions: {:#?}", universal_regions);
         debug!("outlives constraints: {:#?}", outlives_constraints);
@@ -430,7 +430,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         }
 
         let mut scc_values =
-            RegionValues::new(elements, universal_regions.len(), &placeholder_indices);
+            RegionValues::new(elements, universal_regions.len(), placeholder_indices);
 
         for region in liveness_constraints.regions() {
             let scc = constraint_sccs.scc(region);
@@ -637,7 +637,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         &mut self,
         infcx: &InferCtxt<'tcx>,
         body: &Body<'tcx>,
-        polonius_output: Option<Rc<PoloniusOutput>>,
+        polonius_output: Option<Box<PoloniusOutput>>,
     ) -> (Option<ClosureRegionRequirements<'tcx>>, RegionErrors<'tcx>) {
         let mir_def_id = body.source.def_id();
         self.propagate_constraints();
@@ -663,7 +663,9 @@ impl<'tcx> RegionInferenceContext<'tcx> {
             self.check_polonius_subset_errors(
                 outlives_requirements.as_mut(),
                 &mut errors_buffer,
-                polonius_output.expect("Polonius output is unavailable despite `-Z polonius`"),
+                polonius_output
+                    .as_ref()
+                    .expect("Polonius output is unavailable despite `-Z polonius`"),
             );
         } else {
             self.check_universal_regions(outlives_requirements.as_mut(), &mut errors_buffer);
@@ -1411,7 +1413,7 @@ impl<'tcx> RegionInferenceContext<'tcx> {
         &self,
         mut propagated_outlives_requirements: Option<&mut Vec<ClosureOutlivesRequirement<'tcx>>>,
         errors_buffer: &mut RegionErrors<'tcx>,
-        polonius_output: Rc<PoloniusOutput>,
+        polonius_output: &PoloniusOutput,
     ) {
         debug!(
             "check_polonius_subset_errors: {} subset_errors",

compiler/rustc_borrowck/src/region_infer/values.rs

@@ -275,15 +275,16 @@ impl<N: Idx> RegionValues<N> {
     /// Each of the regions in num_region_variables will be initialized with an
     /// empty set of points and no causal information.
     pub(crate) fn new(
-        elements: &Rc<DenseLocationMap>,
+        elements: Rc<DenseLocationMap>,
         num_universal_regions: usize,
-        placeholder_indices: &Rc<PlaceholderIndices>,
+        placeholder_indices: Rc<PlaceholderIndices>,
     ) -> Self {
+        let num_points = elements.num_points();
         let num_placeholders = placeholder_indices.len();
         Self {
-            elements: elements.clone(),
-            points: SparseIntervalMatrix::new(elements.num_points()),
-            placeholder_indices: placeholder_indices.clone(),
+            elements,
+            points: SparseIntervalMatrix::new(num_points),
+            placeholder_indices,
             free_regions: SparseBitMatrix::new(num_universal_regions),
             placeholders: SparseBitMatrix::new(num_placeholders),
         }

compiler/rustc_borrowck/src/type_check/free_region_relations.rs

@@ -54,15 +54,15 @@ pub(crate) fn create<'tcx>(
     infcx: &InferCtxt<'tcx>,
     param_env: ty::ParamEnv<'tcx>,
     implicit_region_bound: ty::Region<'tcx>,
-    universal_regions: &Rc<UniversalRegions<'tcx>>,
+    universal_regions: Rc<UniversalRegions<'tcx>>,
     constraints: &mut MirTypeckRegionConstraints<'tcx>,
 ) -> CreateResult<'tcx> {
     UniversalRegionRelationsBuilder {
         infcx,
         param_env,
         implicit_region_bound,
         constraints,
-        universal_regions: universal_regions.clone(),
+        universal_regions,
         region_bound_pairs: Default::default(),
         outlives: Default::default(),
         inverse_outlives: Default::default(),

compiler/rustc_borrowck/src/type_check/liveness/mod.rs

@@ -1,5 +1,3 @@
-use std::rc::Rc;
-
 use itertools::{Either, Itertools};
 use rustc_data_structures::fx::FxHashSet;
 use rustc_middle::mir::visit::{TyContext, Visitor};
@@ -33,7 +31,7 @@ mod trace;
 pub(super) fn generate<'a, 'tcx>(
     typeck: &mut TypeChecker<'_, 'tcx>,
     body: &Body<'tcx>,
-    elements: &Rc<DenseLocationMap>,
+    elements: &DenseLocationMap,
     flow_inits: &mut ResultsCursor<'a, 'tcx, MaybeInitializedPlaces<'a, 'tcx>>,
     move_data: &MoveData<'tcx>,
 ) {