Rollup merge of #132134 - nnethercote:rm-ResultsVisitable, r=cjgillot

Remove `ResultsVisitable`

`ResultsVisitable` has annoyed me for a while. This PR removes it. Details in the individual commits.

r? `@cjgillot.`

2 files changed, 173 insertions, 80 deletions

diff --git a/compiler/rustc_borrowck/src/dataflow.rs b/compiler/rustc_borrowck/src/dataflow.rs
index d832decc170..7adc7a8863e 100644
--- a/compiler/rustc_borrowck/src/dataflow.rs
+++ b/compiler/rustc_borrowck/src/dataflow.rs
@@ -1,93 +1,171 @@
+use std::fmt;
+
 use rustc_data_structures::fx::FxIndexMap;
 use rustc_data_structures::graph;
 use rustc_index::bit_set::BitSet;
-use rustc_middle::mir::{self, BasicBlock, Body, Location, Place, TerminatorEdges};
+use rustc_middle::mir::{
+    self, BasicBlock, Body, CallReturnPlaces, Location, Place, TerminatorEdges,
+};
 use rustc_middle::ty::{RegionVid, TyCtxt};
 use rustc_mir_dataflow::fmt::DebugWithContext;
 use rustc_mir_dataflow::impls::{EverInitializedPlaces, MaybeUninitializedPlaces};
-use rustc_mir_dataflow::{Analysis, Forward, GenKill, Results, ResultsVisitable};
+use rustc_mir_dataflow::{Analysis, GenKill, JoinSemiLattice, SwitchIntEdgeEffects};
 use tracing::debug;
 
 use crate::{BorrowSet, PlaceConflictBias, PlaceExt, RegionInferenceContext, places_conflict};
 
-/// The results of the dataflow analyses used by the borrow checker.
-pub(crate) struct BorrowckResults<'a, 'tcx> {
-    pub(crate) borrows: Results<'tcx, Borrows<'a, 'tcx>>,
-    pub(crate) uninits: Results<'tcx, MaybeUninitializedPlaces<'a, 'tcx>>,
-    pub(crate) ever_inits: Results<'tcx, EverInitializedPlaces<'a, 'tcx>>,
-}
-
-/// The transient state of the dataflow analyses used by the borrow checker.
-#[derive(Debug)]
-pub(crate) struct BorrowckDomain<'a, 'tcx> {
-    pub(crate) borrows: <Borrows<'a, 'tcx> as Analysis<'tcx>>::Domain,
-    pub(crate) uninits: <MaybeUninitializedPlaces<'a, 'tcx> as Analysis<'tcx>>::Domain,
-    pub(crate) ever_inits: <EverInitializedPlaces<'a, 'tcx> as Analysis<'tcx>>::Domain,
+// This analysis is different to most others. Its results aren't computed with
+// `iterate_to_fixpoint`, but are instead composed from the results of three sub-analyses that are
+// computed individually with `iterate_to_fixpoint`.
+pub(crate) struct Borrowck<'a, 'tcx> {
+    pub(crate) borrows: Borrows<'a, 'tcx>,
+    pub(crate) uninits: MaybeUninitializedPlaces<'a, 'tcx>,
+    pub(crate) ever_inits: EverInitializedPlaces<'a, 'tcx>,
 }
 
-impl<'a, 'tcx> ResultsVisitable<'tcx> for BorrowckResults<'a, 'tcx> {
-    type Direction = Forward;
+impl<'a, 'tcx> Analysis<'tcx> for Borrowck<'a, 'tcx> {
     type Domain = BorrowckDomain<'a, 'tcx>;
 
+    const NAME: &'static str = "borrowck";
+
     fn bottom_value(&self, body: &mir::Body<'tcx>) -> Self::Domain {
         BorrowckDomain {
-            borrows: self.borrows.analysis.bottom_value(body),
-            uninits: self.uninits.analysis.bottom_value(body),
-            ever_inits: self.ever_inits.analysis.bottom_value(body),
+            borrows: self.borrows.bottom_value(body),
+            uninits: self.uninits.bottom_value(body),
+            ever_inits: self.ever_inits.bottom_value(body),
         }
     }
 
-    fn reset_to_block_entry(&self, state: &mut Self::Domain, block: BasicBlock) {
-        state.borrows.clone_from(self.borrows.entry_set_for_block(block));
-        state.uninits.clone_from(self.uninits.entry_set_for_block(block));
-        state.ever_inits.clone_from(self.ever_inits.entry_set_for_block(block));
+    fn initialize_start_block(&self, _body: &mir::Body<'tcx>, _state: &mut Self::Domain) {
+        // This is only reachable from `iterate_to_fixpoint`, which this analysis doesn't use.
+        unreachable!();
     }
 
-    fn reconstruct_before_statement_effect(
+    fn apply_before_statement_effect(
         &mut self,
         state: &mut Self::Domain,
         stmt: &mir::Statement<'tcx>,
         loc: Location,
     ) {
-        self.borrows.analysis.apply_before_statement_effect(&mut state.borrows, stmt, loc);
-        self.uninits.analysis.apply_before_statement_effect(&mut state.uninits, stmt, loc);
-        self.ever_inits.analysis.apply_before_statement_effect(&mut state.ever_inits, stmt, loc);
+        self.borrows.apply_before_statement_effect(&mut state.borrows, stmt, loc);
+        self.uninits.apply_before_statement_effect(&mut state.uninits, stmt, loc);
+        self.ever_inits.apply_before_statement_effect(&mut state.ever_inits, stmt, loc);
     }
 
-    fn reconstruct_statement_effect(
+    fn apply_statement_effect(
         &mut self,
         state: &mut Self::Domain,
         stmt: &mir::Statement<'tcx>,
         loc: Location,
     ) {
-        self.borrows.analysis.apply_statement_effect(&mut state.borrows, stmt, loc);
-        self.uninits.analysis.apply_statement_effect(&mut state.uninits, stmt, loc);
-        self.ever_inits.analysis.apply_statement_effect(&mut state.ever_inits, stmt, loc);
+        self.borrows.apply_statement_effect(&mut state.borrows, stmt, loc);
+        self.uninits.apply_statement_effect(&mut state.uninits, stmt, loc);
+        self.ever_inits.apply_statement_effect(&mut state.ever_inits, stmt, loc);
     }
 
-    fn reconstruct_before_terminator_effect(
+    fn apply_before_terminator_effect(
         &mut self,
         state: &mut Self::Domain,
         term: &mir::Terminator<'tcx>,
         loc: Location,
     ) {
-        self.borrows.analysis.apply_before_terminator_effect(&mut state.borrows, term, loc);
-        self.uninits.analysis.apply_before_terminator_effect(&mut state.uninits, term, loc);
-        self.ever_inits.analysis.apply_before_terminator_effect(&mut state.ever_inits, term, loc);
+        self.borrows.apply_before_terminator_effect(&mut state.borrows, term, loc);
+        self.uninits.apply_before_terminator_effect(&mut state.uninits, term, loc);
+        self.ever_inits.apply_before_terminator_effect(&mut state.ever_inits, term, loc);
     }
 
-    fn reconstruct_terminator_effect(
+    fn apply_terminator_effect<'mir>(
         &mut self,
         state: &mut Self::Domain,
-        term: &mir::Terminator<'tcx>,
+        term: &'mir mir::Terminator<'tcx>,
         loc: Location,
+    ) -> TerminatorEdges<'mir, 'tcx> {
+        self.borrows.apply_terminator_effect(&mut state.borrows, term, loc);
+        self.uninits.apply_terminator_effect(&mut state.uninits, term, loc);
+        self.ever_inits.apply_terminator_effect(&mut state.ever_inits, term, loc);
+
+        // This return value doesn't matter. It's only used by `iterate_to_fixpoint`, which this
+        // analysis doesn't use.
+        TerminatorEdges::None
+    }
+
+    fn apply_call_return_effect(
+        &mut self,
+        _state: &mut Self::Domain,
+        _block: BasicBlock,
+        _return_places: CallReturnPlaces<'_, 'tcx>,
+    ) {
+        // This is only reachable from `iterate_to_fixpoint`, which this analysis doesn't use.
+        unreachable!();
+    }
+
+    fn apply_switch_int_edge_effects(
+        &mut self,
+        _block: BasicBlock,
+        _discr: &mir::Operand<'tcx>,
+        _apply_edge_effects: &mut impl SwitchIntEdgeEffects<Self::Domain>,
     ) {
-        self.borrows.analysis.apply_terminator_effect(&mut state.borrows, term, loc);
-        self.uninits.analysis.apply_terminator_effect(&mut state.uninits, term, loc);
-        self.ever_inits.analysis.apply_terminator_effect(&mut state.ever_inits, term, loc);
+        // This is only reachable from `iterate_to_fixpoint`, which this analysis doesn't use.
+        unreachable!();
     }
 }
 
+impl JoinSemiLattice for BorrowckDomain<'_, '_> {
+    fn join(&mut self, _other: &Self) -> bool {
+        // This is only reachable from `iterate_to_fixpoint`, which this analysis doesn't use.
+        unreachable!();
+    }
+}
+
+impl<'tcx, C> DebugWithContext<C> for BorrowckDomain<'_, 'tcx>
+where
+    C: rustc_mir_dataflow::move_paths::HasMoveData<'tcx>,
+{
+    fn fmt_with(&self, ctxt: &C, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        f.write_str("borrows: ")?;
+        self.borrows.fmt_with(ctxt, f)?;
+        f.write_str(" uninits: ")?;
+        self.uninits.fmt_with(ctxt, f)?;
+        f.write_str(" ever_inits: ")?;
+        self.ever_inits.fmt_with(ctxt, f)?;
+        Ok(())
+    }
+
+    fn fmt_diff_with(&self, old: &Self, ctxt: &C, f: &mut fmt::Formatter<'_>) -> fmt::Result {
+        if self == old {
+            return Ok(());
+        }
+
+        if self.borrows != old.borrows {
+            f.write_str("borrows: ")?;
+            self.borrows.fmt_diff_with(&old.borrows, ctxt, f)?;
+            f.write_str("\n")?;
+        }
+
+        if self.uninits != old.uninits {
+            f.write_str("uninits: ")?;
+            self.uninits.fmt_diff_with(&old.uninits, ctxt, f)?;
+            f.write_str("\n")?;
+        }
+
+        if self.ever_inits != old.ever_inits {
+            f.write_str("ever_inits: ")?;
+            self.ever_inits.fmt_diff_with(&old.ever_inits, ctxt, f)?;
+            f.write_str("\n")?;
+        }
+
+        Ok(())
+    }
+}
+
+/// The transient state of the dataflow analyses used by the borrow checker.
+#[derive(Clone, Debug, PartialEq, Eq)]
+pub(crate) struct BorrowckDomain<'a, 'tcx> {
+    pub(crate) borrows: <Borrows<'a, 'tcx> as Analysis<'tcx>>::Domain,
+    pub(crate) uninits: <MaybeUninitializedPlaces<'a, 'tcx> as Analysis<'tcx>>::Domain,
+    pub(crate) ever_inits: <EverInitializedPlaces<'a, 'tcx> as Analysis<'tcx>>::Domain,
+}
+
 rustc_index::newtype_index! {
     #[orderable]
     #[debug_format = "bw{}"]
diff --git a/compiler/rustc_borrowck/src/lib.rs b/compiler/rustc_borrowck/src/lib.rs
index 657e6e0907c..7eaf265d410 100644
--- a/compiler/rustc_borrowck/src/lib.rs
+++ b/compiler/rustc_borrowck/src/lib.rs
@@ -36,13 +36,13 @@ use rustc_middle::mir::*;
 use rustc_middle::query::Providers;
 use rustc_middle::ty::{self, ParamEnv, RegionVid, TyCtxt, TypingMode};
 use rustc_middle::{bug, span_bug};
-use rustc_mir_dataflow::Analysis;
 use rustc_mir_dataflow::impls::{
     EverInitializedPlaces, MaybeInitializedPlaces, MaybeUninitializedPlaces,
 };
 use rustc_mir_dataflow::move_paths::{
     InitIndex, InitLocation, LookupResult, MoveData, MoveOutIndex, MovePathIndex,
 };
+use rustc_mir_dataflow::{Analysis, EntrySets, Results, ResultsVisitor, visit_results};
 use rustc_session::lint::builtin::UNUSED_MUT;
 use rustc_span::{Span, Symbol};
 use smallvec::SmallVec;
@@ -50,7 +50,7 @@ use tracing::{debug, instrument};
 
 use crate::borrow_set::{BorrowData, BorrowSet};
 use crate::consumers::{BodyWithBorrowckFacts, ConsumerOptions};
-use crate::dataflow::{BorrowIndex, BorrowckDomain, BorrowckResults, Borrows};
+use crate::dataflow::{BorrowIndex, Borrowck, BorrowckDomain, Borrows};
 use crate::diagnostics::{AccessKind, IllegalMoveOriginKind, MoveError, RegionName};
 use crate::location::LocationTable;
 use crate::nll::PoloniusOutput;
@@ -221,6 +221,10 @@ fn do_mir_borrowck<'tcx>(
         consumer_options,
     );
 
+    // `flow_inits` is large, so we drop it as soon as possible. This reduces
+    // peak memory usage significantly on some benchmarks.
+    drop(flow_inits);
+
     // Dump MIR results into a file, if that is enabled. This let us
     // write unit-tests, as well as helping with debugging.
     nll::dump_nll_mir(&infcx, body, &regioncx, &opt_closure_req, &borrow_set);
@@ -229,27 +233,6 @@ fn do_mir_borrowck<'tcx>(
     // information.
     nll::dump_annotation(&infcx, body, &regioncx, &opt_closure_req, &opaque_type_values, diags);
 
-    // The various `flow_*` structures can be large. We drop `flow_inits` here
-    // so it doesn't overlap with the others below. This reduces peak memory
-    // usage significantly on some benchmarks.
-    drop(flow_inits);
-
-    let flow_borrows = Borrows::new(tcx, body, &regioncx, &borrow_set).iterate_to_fixpoint(
-        tcx,
-        body,
-        Some("borrowck"),
-    );
-    let flow_uninits = MaybeUninitializedPlaces::new(tcx, body, &move_data).iterate_to_fixpoint(
-        tcx,
-        body,
-        Some("borrowck"),
-    );
-    let flow_ever_inits = EverInitializedPlaces::new(body, &move_data).iterate_to_fixpoint(
-        tcx,
-        body,
-        Some("borrowck"),
-    );
-
     let movable_coroutine =
         // The first argument is the coroutine type passed by value
         if let Some(local) = body.local_decls.raw.get(1)
@@ -334,16 +317,11 @@ fn do_mir_borrowck<'tcx>(
     // Compute and report region errors, if any.
     mbcx.report_region_errors(nll_errors);
 
-    let mut results = BorrowckResults {
-        ever_inits: flow_ever_inits,
-        uninits: flow_uninits,
-        borrows: flow_borrows,
-    };
-
-    rustc_mir_dataflow::visit_results(
+    let mut flow_results = get_flow_results(tcx, body, &move_data, &borrow_set, &regioncx);
+    visit_results(
         body,
         traversal::reverse_postorder(body).map(|(bb, _)| bb),
-        &mut results,
+        &mut flow_results,
         &mut mbcx,
     );
 
@@ -426,6 +404,47 @@ fn do_mir_borrowck<'tcx>(
     (result, body_with_facts)
 }
 
+fn get_flow_results<'a, 'tcx>(
+    tcx: TyCtxt<'tcx>,
+    body: &'a Body<'tcx>,
+    move_data: &'a MoveData<'tcx>,
+    borrow_set: &'a BorrowSet<'tcx>,
+    regioncx: &RegionInferenceContext<'tcx>,
+) -> Results<'tcx, Borrowck<'a, 'tcx>> {
+    // We compute these three analyses individually, but them combine them into
+    // a single results so that `mbcx` can visit them all together.
+    let borrows = Borrows::new(tcx, body, regioncx, borrow_set).iterate_to_fixpoint(
+        tcx,
+        body,
+        Some("borrowck"),
+    );
+    let uninits = MaybeUninitializedPlaces::new(tcx, body, move_data).iterate_to_fixpoint(
+        tcx,
+        body,
+        Some("borrowck"),
+    );
+    let ever_inits = EverInitializedPlaces::new(body, move_data).iterate_to_fixpoint(
+        tcx,
+        body,
+        Some("borrowck"),
+    );
+
+    let analysis = Borrowck {
+        borrows: borrows.analysis,
+        uninits: uninits.analysis,
+        ever_inits: ever_inits.analysis,
+    };
+
+    assert_eq!(borrows.entry_sets.len(), uninits.entry_sets.len());
+    assert_eq!(borrows.entry_sets.len(), ever_inits.entry_sets.len());
+    let entry_sets: EntrySets<'_, Borrowck<'_, '_>> =
+        itertools::izip!(borrows.entry_sets, uninits.entry_sets, ever_inits.entry_sets)
+            .map(|(borrows, uninits, ever_inits)| BorrowckDomain { borrows, uninits, ever_inits })
+            .collect();
+
+    Results { analysis, entry_sets }
+}
+
 pub(crate) struct BorrowckInferCtxt<'tcx> {
     pub(crate) infcx: InferCtxt<'tcx>,
     pub(crate) reg_var_to_origin: RefCell<FxIndexMap<ty::RegionVid, RegionCtxt>>,
@@ -588,14 +607,10 @@ struct MirBorrowckCtxt<'a, 'infcx, 'tcx> {
 // 2. loans made in overlapping scopes do not conflict
 // 3. assignments do not affect things loaned out as immutable
 // 4. moves do not affect things loaned out in any way
-impl<'a, 'tcx, R> rustc_mir_dataflow::ResultsVisitor<'a, 'tcx, R>
-    for MirBorrowckCtxt<'a, '_, 'tcx>
-{
-    type Domain = BorrowckDomain<'a, 'tcx>;
-
+impl<'a, 'tcx> ResultsVisitor<'a, 'tcx, Borrowck<'a, 'tcx>> for MirBorrowckCtxt<'a, '_, 'tcx> {
     fn visit_statement_before_primary_effect(
         &mut self,
-        _results: &mut R,
+        _results: &mut Results<'tcx, Borrowck<'a, 'tcx>>,
         state: &BorrowckDomain<'a, 'tcx>,
         stmt: &'a Statement<'tcx>,
         location: Location,
@@ -667,7 +682,7 @@ impl<'a, 'tcx, R> rustc_mir_dataflow::ResultsVisitor<'a, 'tcx, R>
 
     fn visit_terminator_before_primary_effect(
         &mut self,
-        _results: &mut R,
+        _results: &mut Results<'tcx, Borrowck<'a, 'tcx>>,
         state: &BorrowckDomain<'a, 'tcx>,
         term: &'a Terminator<'tcx>,
         loc: Location,
@@ -780,7 +795,7 @@ impl<'a, 'tcx, R> rustc_mir_dataflow::ResultsVisitor<'a, 'tcx, R>
 
     fn visit_terminator_after_primary_effect(
         &mut self,
-        _results: &mut R,
+        _results: &mut Results<'tcx, Borrowck<'a, 'tcx>>,
         state: &BorrowckDomain<'a, 'tcx>,
         term: &'a Terminator<'tcx>,
         loc: Location,