Auto merge of #69295 - ecstatic-morse:unified-dataflow-generators, r=tmandry

Use new dataflow framework for generators

#65672 introduced a new dataflow framework that can handle arbitrarily complex transfer functions as well as ones expressed as a series of gen/kill operations. This PR ports the analyses used to implement generators to the new framework so that we can remove the old one. See #68241 for a prior example of this. The new framework has some superficial API changes, but this shouldn't alter the generator passes in any way.

r? @tmandry

5 files changed, 159 insertions, 158 deletions

diff --git a/src/librustc_mir/dataflow/generic/mod.rs b/src/librustc_mir/dataflow/generic/mod.rs
index c61b7bed353..9a102c9a3d0 100644
--- a/src/librustc_mir/dataflow/generic/mod.rs
+++ b/src/librustc_mir/dataflow/generic/mod.rs
@@ -75,6 +75,24 @@ where
     pub fn entry_set_for_block(&self, block: BasicBlock) -> &BitSet<A::Idx> {
         &self.entry_sets[block]
     }
+
+    pub fn visit_with(
+        &self,
+        body: &'mir mir::Body<'tcx>,
+        blocks: impl IntoIterator<Item = BasicBlock>,
+        vis: &mut impl ResultsVisitor<'mir, 'tcx, FlowState = BitSet<A::Idx>>,
+    ) {
+        visit_results(body, blocks, self, vis)
+    }
+
+    pub fn visit_in_rpo_with(
+        &self,
+        body: &'mir mir::Body<'tcx>,
+        vis: &mut impl ResultsVisitor<'mir, 'tcx, FlowState = BitSet<A::Idx>>,
+    ) {
+        let blocks = mir::traversal::reverse_postorder(body);
+        visit_results(body, blocks.map(|(bb, _)| bb), self, vis)
+    }
 }
 
 /// Define the domain of a dataflow problem.
@@ -433,16 +451,5 @@ impl<T: Idx> GenKill<T> for BitSet<T> {
     }
 }
 
-// For compatibility with old framework
-impl<T: Idx> GenKill<T> for crate::dataflow::GenKillSet<T> {
-    fn gen(&mut self, elem: T) {
-        self.gen(elem);
-    }
-
-    fn kill(&mut self, elem: T) {
-        self.kill(elem);
-    }
-}
-
 #[cfg(test)]
 mod tests;
diff --git a/src/librustc_mir/dataflow/impls/mod.rs b/src/librustc_mir/dataflow/impls/mod.rs
index 59aa91ab824..87d8e9e411c 100644
--- a/src/librustc_mir/dataflow/impls/mod.rs
+++ b/src/librustc_mir/dataflow/impls/mod.rs
@@ -14,7 +14,7 @@ use crate::util::elaborate_drops::DropFlagState;
 
 use super::generic::{AnalysisDomain, GenKill, GenKillAnalysis};
 use super::move_paths::{HasMoveData, InitIndex, InitKind, LookupResult, MoveData, MovePathIndex};
-use super::{BottomValue, GenKillSet};
+use super::BottomValue;
 
 use super::drop_flag_effects_for_function_entry;
 use super::drop_flag_effects_for_location;
diff --git a/src/librustc_mir/dataflow/impls/storage_liveness.rs b/src/librustc_mir/dataflow/impls/storage_liveness.rs
index 659b66823c2..fabe562e68a 100644
--- a/src/librustc_mir/dataflow/impls/storage_liveness.rs
+++ b/src/librustc_mir/dataflow/impls/storage_liveness.rs
@@ -1,47 +1,39 @@
 pub use super::*;
 
-use crate::dataflow::generic::{Results, ResultsRefCursor};
-use crate::dataflow::BitDenotation;
-use crate::dataflow::MaybeBorrowedLocals;
+use crate::dataflow::generic::{self as dataflow, GenKill, Results, ResultsRefCursor};
+use crate::dataflow::BottomValue;
 use rustc::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor};
 use rustc::mir::*;
 use std::cell::RefCell;
 
 #[derive(Copy, Clone)]
-pub struct MaybeStorageLive<'a, 'tcx> {
-    body: &'a Body<'tcx>,
-}
+pub struct MaybeStorageLive;
 
-impl<'a, 'tcx> MaybeStorageLive<'a, 'tcx> {
-    pub fn new(body: &'a Body<'tcx>) -> Self {
-        MaybeStorageLive { body }
-    }
+impl dataflow::AnalysisDomain<'tcx> for MaybeStorageLive {
+    type Idx = Local;
 
-    pub fn body(&self) -> &Body<'tcx> {
-        self.body
-    }
-}
+    const NAME: &'static str = "maybe_storage_live";
 
-impl<'a, 'tcx> BitDenotation<'tcx> for MaybeStorageLive<'a, 'tcx> {
-    type Idx = Local;
-    fn name() -> &'static str {
-        "maybe_storage_live"
-    }
-    fn bits_per_block(&self) -> usize {
-        self.body.local_decls.len()
+    fn bits_per_block(&self, body: &mir::Body<'tcx>) -> usize {
+        body.local_decls.len()
     }
 
-    fn start_block_effect(&self, on_entry: &mut BitSet<Local>) {
+    fn initialize_start_block(&self, body: &mir::Body<'tcx>, on_entry: &mut BitSet<Self::Idx>) {
         // The resume argument is live on function entry (we don't care about
         // the `self` argument)
-        for arg in self.body.args_iter().skip(1) {
+        for arg in body.args_iter().skip(1) {
             on_entry.insert(arg);
         }
     }
+}
 
-    fn statement_effect(&self, trans: &mut GenKillSet<Local>, loc: Location) {
-        let stmt = &self.body[loc.block].statements[loc.statement_index];
-
+impl dataflow::GenKillAnalysis<'tcx> for MaybeStorageLive {
+    fn statement_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        stmt: &mir::Statement<'tcx>,
+        _: Location,
+    ) {
         match stmt.kind {
             StatementKind::StorageLive(l) => trans.gen(l),
             StatementKind::StorageDead(l) => trans.kill(l),
@@ -49,22 +41,28 @@ impl<'a, 'tcx> BitDenotation<'tcx> for MaybeStorageLive<'a, 'tcx> {
         }
     }
 
-    fn terminator_effect(&self, _trans: &mut GenKillSet<Local>, _loc: Location) {
+    fn terminator_effect(
+        &self,
+        _trans: &mut impl GenKill<Self::Idx>,
+        _: &mir::Terminator<'tcx>,
+        _: Location,
+    ) {
         // Terminators have no effect
     }
 
-    fn propagate_call_return(
+    fn call_return_effect(
         &self,
-        _in_out: &mut BitSet<Local>,
-        _call_bb: mir::BasicBlock,
-        _dest_bb: mir::BasicBlock,
-        _dest_place: &mir::Place<'tcx>,
+        _trans: &mut impl GenKill<Self::Idx>,
+        _block: BasicBlock,
+        _func: &mir::Operand<'tcx>,
+        _args: &[mir::Operand<'tcx>],
+        _return_place: &mir::Place<'tcx>,
     ) {
         // Nothing to do when a call returns successfully
     }
 }
 
-impl<'a, 'tcx> BottomValue for MaybeStorageLive<'a, 'tcx> {
+impl BottomValue for MaybeStorageLive {
     /// bottom = dead
     const BOTTOM_VALUE: bool = false;
 }
@@ -73,60 +71,62 @@ type BorrowedLocalsResults<'a, 'tcx> = ResultsRefCursor<'a, 'a, 'tcx, MaybeBorro
 
 /// Dataflow analysis that determines whether each local requires storage at a
 /// given location; i.e. whether its storage can go away without being observed.
-pub struct RequiresStorage<'mir, 'tcx> {
+pub struct MaybeRequiresStorage<'mir, 'tcx> {
     body: ReadOnlyBodyAndCache<'mir, 'tcx>,
     borrowed_locals: RefCell<BorrowedLocalsResults<'mir, 'tcx>>,
 }
 
-impl<'mir, 'tcx: 'mir> RequiresStorage<'mir, 'tcx> {
+impl<'mir, 'tcx> MaybeRequiresStorage<'mir, 'tcx> {
     pub fn new(
         body: ReadOnlyBodyAndCache<'mir, 'tcx>,
         borrowed_locals: &'mir Results<'tcx, MaybeBorrowedLocals>,
     ) -> Self {
-        RequiresStorage {
+        MaybeRequiresStorage {
             body,
             borrowed_locals: RefCell::new(ResultsRefCursor::new(*body, borrowed_locals)),
         }
     }
-
-    pub fn body(&self) -> &Body<'tcx> {
-        &self.body
-    }
 }
 
-impl<'mir, 'tcx> BitDenotation<'tcx> for RequiresStorage<'mir, 'tcx> {
+impl<'mir, 'tcx> dataflow::AnalysisDomain<'tcx> for MaybeRequiresStorage<'mir, 'tcx> {
     type Idx = Local;
-    fn name() -> &'static str {
-        "requires_storage"
-    }
-    fn bits_per_block(&self) -> usize {
-        self.body.local_decls.len()
+
+    const NAME: &'static str = "requires_storage";
+
+    fn bits_per_block(&self, body: &mir::Body<'tcx>) -> usize {
+        body.local_decls.len()
     }
 
-    fn start_block_effect(&self, on_entry: &mut BitSet<Local>) {
+    fn initialize_start_block(&self, body: &mir::Body<'tcx>, on_entry: &mut BitSet<Self::Idx>) {
         // The resume argument is live on function entry (we don't care about
         // the `self` argument)
-        for arg in self.body.args_iter().skip(1) {
+        for arg in body.args_iter().skip(1) {
             on_entry.insert(arg);
         }
     }
+}
 
-    fn before_statement_effect(&self, sets: &mut GenKillSet<Self::Idx>, loc: Location) {
-        let stmt = &self.body[loc.block].statements[loc.statement_index];
-
+impl<'mir, 'tcx> dataflow::GenKillAnalysis<'tcx> for MaybeRequiresStorage<'mir, 'tcx> {
+    fn before_statement_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        stmt: &mir::Statement<'tcx>,
+        loc: Location,
+    ) {
         // If a place is borrowed in a statement, it needs storage for that statement.
-        self.borrowed_locals.borrow().analysis().statement_effect(sets, stmt, loc);
+        self.borrowed_locals.borrow().analysis().statement_effect(trans, stmt, loc);
 
-        // If a place is assigned to in a statement, it needs storage for that statement.
         match &stmt.kind {
-            StatementKind::StorageDead(l) => sets.kill(*l),
+            StatementKind::StorageDead(l) => trans.kill(*l),
+
+            // If a place is assigned to in a statement, it needs storage for that statement.
             StatementKind::Assign(box (place, _))
             | StatementKind::SetDiscriminant { box place, .. } => {
-                sets.gen(place.local);
+                trans.gen(place.local);
             }
-            StatementKind::InlineAsm(box InlineAsm { outputs, .. }) => {
-                for place in &**outputs {
-                    sets.gen(place.local);
+            StatementKind::InlineAsm(asm) => {
+                for place in &*asm.outputs {
+                    trans.gen(place.local);
                 }
             }
 
@@ -140,22 +140,30 @@ impl<'mir, 'tcx> BitDenotation<'tcx> for RequiresStorage<'mir, 'tcx> {
         }
     }
 
-    fn statement_effect(&self, sets: &mut GenKillSet<Local>, loc: Location) {
+    fn statement_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _: &mir::Statement<'tcx>,
+        loc: Location,
+    ) {
         // If we move from a place then only stops needing storage *after*
         // that statement.
-        self.check_for_move(sets, loc);
+        self.check_for_move(trans, loc);
     }
 
-    fn before_terminator_effect(&self, sets: &mut GenKillSet<Local>, loc: Location) {
-        let terminator = self.body[loc.block].terminator();
-
+    fn before_terminator_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        terminator: &mir::Terminator<'tcx>,
+        loc: Location,
+    ) {
         // If a place is borrowed in a terminator, it needs storage for that terminator.
-        self.borrowed_locals.borrow().analysis().terminator_effect(sets, terminator, loc);
+        self.borrowed_locals.borrow().analysis().terminator_effect(trans, terminator, loc);
 
         match &terminator.kind {
-            TerminatorKind::Call { destination: Some((Place { local, .. }, _)), .. }
-            | TerminatorKind::Yield { resume_arg: Place { local, .. }, .. } => {
-                sets.gen(*local);
+            TerminatorKind::Call { destination: Some((place, _)), .. }
+            | TerminatorKind::Yield { resume_arg: place, .. } => {
+                trans.gen(place.local);
             }
 
             // Nothing to do for these. Match exhaustively so this fails to compile when new
@@ -176,14 +184,19 @@ impl<'mir, 'tcx> BitDenotation<'tcx> for RequiresStorage<'mir, 'tcx> {
         }
     }
 
-    fn terminator_effect(&self, sets: &mut GenKillSet<Local>, loc: Location) {
-        match &self.body[loc.block].terminator().kind {
+    fn terminator_effect(
+        &self,
+        trans: &mut impl GenKill<Self::Idx>,
+        terminator: &mir::Terminator<'tcx>,
+        loc: Location,
+    ) {
+        match &terminator.kind {
             // For call terminators the destination requires storage for the call
             // and after the call returns successfully, but not after a panic.
             // Since `propagate_call_unwind` doesn't exist, we have to kill the
-            // destination here, and then gen it again in `propagate_call_return`.
-            TerminatorKind::Call { destination: Some((Place { local, .. }, _)), .. } => {
-                sets.kill(*local);
+            // destination here, and then gen it again in `call_return_effect`.
+            TerminatorKind::Call { destination: Some((place, _)), .. } => {
+                trans.kill(place.local);
             }
 
             // Nothing to do for these. Match exhaustively so this fails to compile when new
@@ -204,45 +217,49 @@ impl<'mir, 'tcx> BitDenotation<'tcx> for RequiresStorage<'mir, 'tcx> {
             | TerminatorKind::Unreachable => {}
         }
 
-        self.check_for_move(sets, loc);
+        self.check_for_move(trans, loc);
     }
 
-    fn propagate_call_return(
+    fn call_return_effect(
         &self,
-        in_out: &mut BitSet<Local>,
-        _call_bb: mir::BasicBlock,
-        _dest_bb: mir::BasicBlock,
-        dest_place: &mir::Place<'tcx>,
+        trans: &mut impl GenKill<Self::Idx>,
+        _block: BasicBlock,
+        _func: &mir::Operand<'tcx>,
+        _args: &[mir::Operand<'tcx>],
+        return_place: &mir::Place<'tcx>,
     ) {
-        in_out.insert(dest_place.local);
+        trans.gen(return_place.local);
     }
 }
 
-impl<'mir, 'tcx> RequiresStorage<'mir, 'tcx> {
+impl<'mir, 'tcx> MaybeRequiresStorage<'mir, 'tcx> {
     /// Kill locals that are fully moved and have not been borrowed.
-    fn check_for_move(&self, sets: &mut GenKillSet<Local>, loc: Location) {
-        let mut visitor = MoveVisitor { sets, borrowed_locals: &self.borrowed_locals };
+    fn check_for_move(&self, trans: &mut impl GenKill<Local>, loc: Location) {
+        let mut visitor = MoveVisitor { trans, borrowed_locals: &self.borrowed_locals };
         visitor.visit_location(self.body, loc);
     }
 }
 
-impl<'mir, 'tcx> BottomValue for RequiresStorage<'mir, 'tcx> {
+impl<'mir, 'tcx> BottomValue for MaybeRequiresStorage<'mir, 'tcx> {
     /// bottom = dead
     const BOTTOM_VALUE: bool = false;
 }
 
-struct MoveVisitor<'a, 'mir, 'tcx> {
+struct MoveVisitor<'a, 'mir, 'tcx, T> {
     borrowed_locals: &'a RefCell<BorrowedLocalsResults<'mir, 'tcx>>,
-    sets: &'a mut GenKillSet<Local>,
+    trans: &'a mut T,
 }
 
-impl<'a, 'mir: 'a, 'tcx> Visitor<'tcx> for MoveVisitor<'a, 'mir, 'tcx> {
+impl<'a, 'mir, 'tcx, T> Visitor<'tcx> for MoveVisitor<'a, 'mir, 'tcx, T>
+where
+    T: GenKill<Local>,
+{
     fn visit_local(&mut self, local: &Local, context: PlaceContext, loc: Location) {
         if PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) == context {
             let mut borrowed_locals = self.borrowed_locals.borrow_mut();
             borrowed_locals.seek_before(loc);
             if !borrowed_locals.contains(*local) {
-                self.sets.kill(*local);
+                self.trans.kill(*local);
             }
         }
     }
diff --git a/src/librustc_mir/dataflow/mod.rs b/src/librustc_mir/dataflow/mod.rs
index 4d86ed9cab2..25463f31867 100644
--- a/src/librustc_mir/dataflow/mod.rs
+++ b/src/librustc_mir/dataflow/mod.rs
@@ -25,7 +25,7 @@ pub use self::impls::DefinitelyInitializedPlaces;
 pub use self::impls::EverInitializedPlaces;
 pub use self::impls::{MaybeBorrowedLocals, MaybeMutBorrowedLocals};
 pub use self::impls::{MaybeInitializedPlaces, MaybeUninitializedPlaces};
-pub use self::impls::{MaybeStorageLive, RequiresStorage};
+pub use self::impls::{MaybeRequiresStorage, MaybeStorageLive};
 
 use self::move_paths::MoveData;
 
diff --git a/src/librustc_mir/transform/generator.rs b/src/librustc_mir/transform/generator.rs
index 3621ca63209..3107be1b622 100644
--- a/src/librustc_mir/transform/generator.rs
+++ b/src/librustc_mir/transform/generator.rs
@@ -49,10 +49,8 @@
 //! For generators with state 1 (returned) and state 2 (poisoned) it does nothing.
 //! Otherwise it drops all the values in scope at the last suspension point.
 
-use crate::dataflow::generic::{Analysis, ResultsCursor};
-use crate::dataflow::{do_dataflow, DataflowResultsCursor, DebugFormatted};
-use crate::dataflow::{DataflowResults, DataflowResultsConsumer, FlowAtLocation};
-use crate::dataflow::{MaybeBorrowedLocals, MaybeStorageLive, RequiresStorage};
+use crate::dataflow::generic::{self as dataflow, Analysis};
+use crate::dataflow::{MaybeBorrowedLocals, MaybeRequiresStorage, MaybeStorageLive};
 use crate::transform::no_landing_pads::no_landing_pads;
 use crate::transform::simplify;
 use crate::transform::{MirPass, MirSource};
@@ -467,18 +465,15 @@ fn locals_live_across_suspend_points(
     source: MirSource<'tcx>,
     movable: bool,
 ) -> LivenessInfo {
-    let dead_unwinds = BitSet::new_empty(body.basic_blocks().len());
     let def_id = source.def_id();
     let body_ref: &Body<'_> = &body;
 
     // Calculate when MIR locals have live storage. This gives us an upper bound of their
     // lifetimes.
-    let storage_live_analysis = MaybeStorageLive::new(body_ref);
-    let storage_live_results =
-        do_dataflow(tcx, body_ref, def_id, &[], &dead_unwinds, storage_live_analysis, |bd, p| {
-            DebugFormatted::new(&bd.body().local_decls[p])
-        });
-    let mut storage_live_cursor = DataflowResultsCursor::new(&storage_live_results, body_ref);
+    let mut storage_live = MaybeStorageLive
+        .into_engine(tcx, body_ref, def_id)
+        .iterate_to_fixpoint()
+        .into_results_cursor(body_ref);
 
     // Find the MIR locals which do not use StorageLive/StorageDead statements.
     // The storage of these locals are always live.
@@ -490,22 +485,16 @@ fn locals_live_across_suspend_points(
     let borrowed_locals_results =
         MaybeBorrowedLocals::all_borrows().into_engine(tcx, body_ref, def_id).iterate_to_fixpoint();
 
-    let mut borrowed_locals_cursor = ResultsCursor::new(body_ref, &borrowed_locals_results);
+    let mut borrowed_locals_cursor =
+        dataflow::ResultsCursor::new(body_ref, &borrowed_locals_results);
 
     // Calculate the MIR locals that we actually need to keep storage around
     // for.
-    let requires_storage_analysis = RequiresStorage::new(body, &borrowed_locals_results);
-    let requires_storage_results = do_dataflow(
-        tcx,
-        body_ref,
-        def_id,
-        &[],
-        &dead_unwinds,
-        requires_storage_analysis,
-        |bd, p| DebugFormatted::new(&bd.body().local_decls[p]),
-    );
+    let requires_storage_results = MaybeRequiresStorage::new(body, &borrowed_locals_results)
+        .into_engine(tcx, body_ref, def_id)
+        .iterate_to_fixpoint();
     let mut requires_storage_cursor =
-        DataflowResultsCursor::new(&requires_storage_results, body_ref);
+        dataflow::ResultsCursor::new(body_ref, &requires_storage_results);
 
     // Calculate the liveness of MIR locals ignoring borrows.
     let mut live_locals = liveness::LiveVarSet::new_empty(body.local_decls.len());
@@ -534,14 +523,14 @@ fn locals_live_across_suspend_points(
                 liveness.outs[block].union(borrowed_locals_cursor.get());
             }
 
-            storage_live_cursor.seek(loc);
-            let storage_liveness = storage_live_cursor.get();
+            storage_live.seek_before(loc);
+            let storage_liveness = storage_live.get();
 
             // Store the storage liveness for later use so we can restore the state
             // after a suspension point
             storage_liveness_map.insert(block, storage_liveness.clone());
 
-            requires_storage_cursor.seek(loc);
+            requires_storage_cursor.seek_before(loc);
             let storage_required = requires_storage_cursor.get().clone();
 
             // Locals live are live at this point only if they are used across
@@ -611,7 +600,7 @@ fn compute_storage_conflicts(
     body: &'mir Body<'tcx>,
     stored_locals: &liveness::LiveVarSet,
     ignored: &StorageIgnored,
-    requires_storage: DataflowResults<'tcx, RequiresStorage<'mir, 'tcx>>,
+    requires_storage: dataflow::Results<'tcx, MaybeRequiresStorage<'mir, 'tcx>>,
 ) -> BitMatrix<GeneratorSavedLocal, GeneratorSavedLocal> {
     assert_eq!(body.local_decls.len(), ignored.0.domain_size());
     assert_eq!(body.local_decls.len(), stored_locals.domain_size());
@@ -629,8 +618,11 @@ fn compute_storage_conflicts(
         stored_locals: &stored_locals,
         local_conflicts: BitMatrix::from_row_n(&ineligible_locals, body.local_decls.len()),
     };
-    let mut state = FlowAtLocation::new(requires_storage);
-    visitor.analyze_results(&mut state);
+
+    // Visit only reachable basic blocks. The exact order is not important.
+    let reachable_blocks = traversal::preorder(body).map(|(bb, _)| bb);
+    requires_storage.visit_with(body, reachable_blocks, &mut visitor);
+
     let local_conflicts = visitor.local_conflicts;
 
     // Compress the matrix using only stored locals (Local -> GeneratorSavedLocal).
@@ -659,60 +651,45 @@ fn compute_storage_conflicts(
     storage_conflicts
 }
 
-struct StorageConflictVisitor<'body, 'tcx, 's> {
-    body: &'body Body<'tcx>,
+struct StorageConflictVisitor<'mir, 'tcx, 's> {
+    body: &'mir Body<'tcx>,
     stored_locals: &'s liveness::LiveVarSet,
     // FIXME(tmandry): Consider using sparse bitsets here once we have good
     // benchmarks for generators.
     local_conflicts: BitMatrix<Local, Local>,
 }
 
-impl<'body, 'tcx, 's> DataflowResultsConsumer<'body, 'tcx>
-    for StorageConflictVisitor<'body, 'tcx, 's>
-{
-    type FlowState = FlowAtLocation<'tcx, RequiresStorage<'body, 'tcx>>;
-
-    fn body(&self) -> &'body Body<'tcx> {
-        self.body
-    }
-
-    fn visit_block_entry(&mut self, block: BasicBlock, flow_state: &Self::FlowState) {
-        // statement_index is only used for logging, so this is fine.
-        self.apply_state(flow_state, Location { block, statement_index: 0 });
-    }
+impl dataflow::ResultsVisitor<'mir, 'tcx> for StorageConflictVisitor<'mir, 'tcx, '_> {
+    type FlowState = BitSet<Local>;
 
-    fn visit_statement_entry(
+    fn visit_statement(
         &mut self,
+        state: &Self::FlowState,
+        _statement: &'mir Statement<'tcx>,
         loc: Location,
-        _stmt: &Statement<'tcx>,
-        flow_state: &Self::FlowState,
     ) {
-        self.apply_state(flow_state, loc);
+        self.apply_state(state, loc);
     }
 
-    fn visit_terminator_entry(
+    fn visit_terminator(
         &mut self,
+        state: &Self::FlowState,
+        _terminator: &'mir Terminator<'tcx>,
         loc: Location,
-        _term: &Terminator<'tcx>,
-        flow_state: &Self::FlowState,
     ) {
-        self.apply_state(flow_state, loc);
+        self.apply_state(state, loc);
     }
 }
 
 impl<'body, 'tcx, 's> StorageConflictVisitor<'body, 'tcx, 's> {
-    fn apply_state(
-        &mut self,
-        flow_state: &FlowAtLocation<'tcx, RequiresStorage<'body, 'tcx>>,
-        loc: Location,
-    ) {
+    fn apply_state(&mut self, flow_state: &BitSet<Local>, loc: Location) {
         // Ignore unreachable blocks.
         match self.body.basic_blocks()[loc.block].terminator().kind {
             TerminatorKind::Unreachable => return,
             _ => (),
         };
 
-        let mut eligible_storage_live = flow_state.as_dense().clone();
+        let mut eligible_storage_live = flow_state.clone();
         eligible_storage_live.intersect(&self.stored_locals);
 
         for local in eligible_storage_live.iter() {