Merge from rust-lang/rust

5 files changed, 54 insertions, 389 deletions

diff --git a/compiler/rustc_mir_dataflow/src/framework/cursor.rs b/compiler/rustc_mir_dataflow/src/framework/cursor.rs
index 7cfaef22689..5ebb343f4e1 100644
--- a/compiler/rustc_mir_dataflow/src/framework/cursor.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/cursor.rs
@@ -7,7 +7,6 @@ use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::{self, BasicBlock, Location};
 
 use super::{Analysis, Direction, Effect, EffectIndex, Results};
-use crate::framework::BitSetExt;
 
 /// Allows random access inspection of the results of a dataflow analysis.
 ///
@@ -221,16 +220,6 @@ where
     }
 }
 
-impl<'mir, 'tcx, A> ResultsCursor<'mir, 'tcx, A>
-where
-    A: crate::GenKillAnalysis<'tcx>,
-    A::Domain: BitSetExt<A::Idx>,
-{
-    pub fn contains(&self, elem: A::Idx) -> bool {
-        self.get().contains(elem)
-    }
-}
-
 #[derive(Clone, Copy, Debug)]
 struct CursorPosition {
     block: BasicBlock,
diff --git a/compiler/rustc_mir_dataflow/src/framework/direction.rs b/compiler/rustc_mir_dataflow/src/framework/direction.rs
index 88a9a78f8ad..3e01f0512c4 100644
--- a/compiler/rustc_mir_dataflow/src/framework/direction.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/direction.rs
@@ -5,7 +5,7 @@ use rustc_middle::mir::{
 };
 
 use super::visitor::{ResultsVisitable, ResultsVisitor};
-use super::{Analysis, Effect, EffectIndex, GenKillAnalysis, GenKillSet, SwitchIntTarget};
+use super::{Analysis, Effect, EffectIndex, SwitchIntTarget};
 
 pub trait Direction {
     const IS_FORWARD: bool;
@@ -29,19 +29,10 @@ pub trait Direction {
         state: &mut A::Domain,
         block: BasicBlock,
         block_data: &'mir mir::BasicBlockData<'tcx>,
-        statement_effect: Option<&dyn Fn(BasicBlock, &mut A::Domain)>,
     ) -> TerminatorEdges<'mir, 'tcx>
     where
         A: Analysis<'tcx>;
 
-    fn gen_kill_statement_effects_in_block<'tcx, A>(
-        analysis: &mut A,
-        trans: &mut GenKillSet<A::Idx>,
-        block: BasicBlock,
-        block_data: &mir::BasicBlockData<'tcx>,
-    ) where
-        A: GenKillAnalysis<'tcx>;
-
     fn visit_results_in_block<'mir, 'tcx, D, R>(
         state: &mut D,
         block: BasicBlock,
@@ -73,7 +64,6 @@ impl Direction for Backward {
         state: &mut A::Domain,
         block: BasicBlock,
         block_data: &'mir mir::BasicBlockData<'tcx>,
-        statement_effect: Option<&dyn Fn(BasicBlock, &mut A::Domain)>,
     ) -> TerminatorEdges<'mir, 'tcx>
     where
         A: Analysis<'tcx>,
@@ -82,31 +72,12 @@ impl Direction for Backward {
         let location = Location { block, statement_index: block_data.statements.len() };
         analysis.apply_before_terminator_effect(state, terminator, location);
         let edges = analysis.apply_terminator_effect(state, terminator, location);
-        if let Some(statement_effect) = statement_effect {
-            statement_effect(block, state)
-        } else {
-            for (statement_index, statement) in block_data.statements.iter().enumerate().rev() {
-                let location = Location { block, statement_index };
-                analysis.apply_before_statement_effect(state, statement, location);
-                analysis.apply_statement_effect(state, statement, location);
-            }
-        }
-        edges
-    }
-
-    fn gen_kill_statement_effects_in_block<'tcx, A>(
-        analysis: &mut A,
-        trans: &mut GenKillSet<A::Idx>,
-        block: BasicBlock,
-        block_data: &mir::BasicBlockData<'tcx>,
-    ) where
-        A: GenKillAnalysis<'tcx>,
-    {
         for (statement_index, statement) in block_data.statements.iter().enumerate().rev() {
             let location = Location { block, statement_index };
-            analysis.before_statement_effect(trans, statement, location);
-            analysis.statement_effect(trans, statement, location);
+            analysis.apply_before_statement_effect(state, statement, location);
+            analysis.apply_statement_effect(state, statement, location);
         }
+        edges
     }
 
     fn apply_effects_in_range<'tcx, A>(
@@ -330,42 +301,21 @@ impl Direction for Forward {
         state: &mut A::Domain,
         block: BasicBlock,
         block_data: &'mir mir::BasicBlockData<'tcx>,
-        statement_effect: Option<&dyn Fn(BasicBlock, &mut A::Domain)>,
     ) -> TerminatorEdges<'mir, 'tcx>
     where
         A: Analysis<'tcx>,
     {
-        if let Some(statement_effect) = statement_effect {
-            statement_effect(block, state)
-        } else {
-            for (statement_index, statement) in block_data.statements.iter().enumerate() {
-                let location = Location { block, statement_index };
-                analysis.apply_before_statement_effect(state, statement, location);
-                analysis.apply_statement_effect(state, statement, location);
-            }
+        for (statement_index, statement) in block_data.statements.iter().enumerate() {
+            let location = Location { block, statement_index };
+            analysis.apply_before_statement_effect(state, statement, location);
+            analysis.apply_statement_effect(state, statement, location);
         }
-
         let terminator = block_data.terminator();
         let location = Location { block, statement_index: block_data.statements.len() };
         analysis.apply_before_terminator_effect(state, terminator, location);
         analysis.apply_terminator_effect(state, terminator, location)
     }
 
-    fn gen_kill_statement_effects_in_block<'tcx, A>(
-        analysis: &mut A,
-        trans: &mut GenKillSet<A::Idx>,
-        block: BasicBlock,
-        block_data: &mir::BasicBlockData<'tcx>,
-    ) where
-        A: GenKillAnalysis<'tcx>,
-    {
-        for (statement_index, statement) in block_data.statements.iter().enumerate() {
-            let location = Location { block, statement_index };
-            analysis.before_statement_effect(trans, statement, location);
-            analysis.statement_effect(trans, statement, location);
-        }
-    }
-
     fn apply_effects_in_range<'tcx, A>(
         analysis: &mut A,
         state: &mut A::Domain,
diff --git a/compiler/rustc_mir_dataflow/src/framework/engine.rs b/compiler/rustc_mir_dataflow/src/framework/engine.rs
index 9d50e57d668..cbd1083d037 100644
--- a/compiler/rustc_mir_dataflow/src/framework/engine.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/engine.rs
@@ -5,7 +5,7 @@ use std::path::PathBuf;
 
 use rustc_data_structures::work_queue::WorkQueue;
 use rustc_hir::def_id::DefId;
-use rustc_index::{Idx, IndexVec};
+use rustc_index::IndexVec;
 use rustc_middle::bug;
 use rustc_middle::mir::{self, BasicBlock, create_dump_file, dump_enabled, traversal};
 use rustc_middle::ty::TyCtxt;
@@ -16,15 +16,13 @@ use {rustc_ast as ast, rustc_graphviz as dot};
 
 use super::fmt::DebugWithContext;
 use super::{
-    Analysis, AnalysisDomain, Direction, GenKill, GenKillAnalysis, GenKillSet, JoinSemiLattice,
-    ResultsCursor, ResultsVisitor, graphviz, visit_results,
+    Analysis, Direction, JoinSemiLattice, ResultsCursor, ResultsVisitor, graphviz, visit_results,
 };
 use crate::errors::{
     DuplicateValuesFor, PathMustEndInFilename, RequiresAnArgument, UnknownFormatter,
 };
-use crate::framework::BitSetExt;
 
-type EntrySets<'tcx, A> = IndexVec<BasicBlock, <A as AnalysisDomain<'tcx>>::Domain>;
+type EntrySets<'tcx, A> = IndexVec<BasicBlock, <A as Analysis<'tcx>>::Domain>;
 
 /// A dataflow analysis that has converged to fixpoint.
 #[derive(Clone)]
@@ -82,53 +80,6 @@ where
     entry_sets: IndexVec<BasicBlock, A::Domain>,
     pass_name: Option<&'static str>,
     analysis: A,
-
-    /// Cached, cumulative transfer functions for each block.
-    //
-    // FIXME(ecstaticmorse): This boxed `Fn` trait object is invoked inside a tight loop for
-    // gen/kill problems on cyclic CFGs. This is not ideal, but it doesn't seem to degrade
-    // performance in practice. I've tried a few ways to avoid this, but they have downsides. See
-    // the message for the commit that added this FIXME for more information.
-    apply_statement_trans_for_block: Option<Box<dyn Fn(BasicBlock, &mut A::Domain)>>,
-}
-
-impl<'mir, 'tcx, A, D, T> Engine<'mir, 'tcx, A>
-where
-    A: GenKillAnalysis<'tcx, Idx = T, Domain = D>,
-    D: Clone + JoinSemiLattice + GenKill<T> + BitSetExt<T>,
-    T: Idx,
-{
-    /// Creates a new `Engine` to solve a gen-kill dataflow problem.
-    pub fn new_gen_kill(tcx: TyCtxt<'tcx>, body: &'mir mir::Body<'tcx>, mut analysis: A) -> Self {
-        // If there are no back-edges in the control-flow graph, we only ever need to apply the
-        // transfer function for each block exactly once (assuming that we process blocks in RPO).
-        //
-        // In this case, there's no need to compute the block transfer functions ahead of time.
-        if !body.basic_blocks.is_cfg_cyclic() {
-            return Self::new(tcx, body, analysis, None);
-        }
-
-        // Otherwise, compute and store the cumulative transfer function for each block.
-
-        let identity = GenKillSet::identity(analysis.domain_size(body));
-        let mut trans_for_block = IndexVec::from_elem(identity, &body.basic_blocks);
-
-        for (block, block_data) in body.basic_blocks.iter_enumerated() {
-            let trans = &mut trans_for_block[block];
-            A::Direction::gen_kill_statement_effects_in_block(
-                &mut analysis,
-                trans,
-                block,
-                block_data,
-            );
-        }
-
-        let apply_trans = Box::new(move |bb: BasicBlock, state: &mut A::Domain| {
-            trans_for_block[bb].apply(state);
-        });
-
-        Self::new(tcx, body, analysis, Some(apply_trans as Box<_>))
-    }
 }
 
 impl<'mir, 'tcx, A, D> Engine<'mir, 'tcx, A>
@@ -138,19 +89,7 @@ where
 {
     /// Creates a new `Engine` to solve a dataflow problem with an arbitrary transfer
     /// function.
-    ///
-    /// Gen-kill problems should use `new_gen_kill`, which will coalesce transfer functions for
-    /// better performance.
-    pub fn new_generic(tcx: TyCtxt<'tcx>, body: &'mir mir::Body<'tcx>, analysis: A) -> Self {
-        Self::new(tcx, body, analysis, None)
-    }
-
-    fn new(
-        tcx: TyCtxt<'tcx>,
-        body: &'mir mir::Body<'tcx>,
-        analysis: A,
-        apply_statement_trans_for_block: Option<Box<dyn Fn(BasicBlock, &mut A::Domain)>>,
-    ) -> Self {
+    pub(crate) fn new(tcx: TyCtxt<'tcx>, body: &'mir mir::Body<'tcx>, analysis: A) -> Self {
         let mut entry_sets =
             IndexVec::from_fn_n(|_| analysis.bottom_value(body), body.basic_blocks.len());
         analysis.initialize_start_block(body, &mut entry_sets[mir::START_BLOCK]);
@@ -160,7 +99,7 @@ where
             bug!("`initialize_start_block` is not yet supported for backward dataflow analyses");
         }
 
-        Engine { analysis, tcx, body, pass_name: None, entry_sets, apply_statement_trans_for_block }
+        Engine { analysis, tcx, body, pass_name: None, entry_sets }
     }
 
     /// Adds an identifier to the graphviz output for this particular run of a dataflow analysis.
@@ -177,14 +116,7 @@ where
     where
         A::Domain: DebugWithContext<A>,
     {
-        let Engine {
-            mut analysis,
-            body,
-            mut entry_sets,
-            tcx,
-            apply_statement_trans_for_block,
-            pass_name,
-        } = self;
+        let Engine { mut analysis, body, mut entry_sets, tcx, pass_name } = self;
 
         let mut dirty_queue: WorkQueue<BasicBlock> = WorkQueue::with_none(body.basic_blocks.len());
 
@@ -213,13 +145,8 @@ where
             state.clone_from(&entry_sets[bb]);
 
             // Apply the block transfer function, using the cached one if it exists.
-            let edges = A::Direction::apply_effects_in_block(
-                &mut analysis,
-                &mut state,
-                bb,
-                bb_data,
-                apply_statement_trans_for_block.as_deref(),
-            );
+            let edges =
+                A::Direction::apply_effects_in_block(&mut analysis, &mut state, bb, bb_data);
 
             A::Direction::join_state_into_successors_of(
                 &mut analysis,
diff --git a/compiler/rustc_mir_dataflow/src/framework/mod.rs b/compiler/rustc_mir_dataflow/src/framework/mod.rs
index d0472e35fe0..959f1ea5340 100644
--- a/compiler/rustc_mir_dataflow/src/framework/mod.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/mod.rs
@@ -1,9 +1,11 @@
 //! A framework that can express both [gen-kill] and generic dataflow problems.
 //!
-//! To use this framework, implement either the [`Analysis`] or the
-//! [`GenKillAnalysis`] trait. If your transfer function can be expressed with only gen/kill
-//! operations, prefer `GenKillAnalysis` since it will run faster while iterating to fixpoint. The
-//! `impls` module contains several examples of gen/kill dataflow analyses.
+//! To use this framework, implement the [`Analysis`] trait. There used to be a `GenKillAnalysis`
+//! alternative trait for gen-kill analyses that would pre-compute the transfer function for each
+//! block. It was intended as an optimization, but it ended up not being any faster than
+//! `Analysis`.
+//!
+//! The `impls` module contains several examples of dataflow analyses.
 //!
 //! Create an `Engine` for your analysis using the `into_engine` method on the `Analysis` trait,
 //! then call `iterate_to_fixpoint`. From there, you can use a `ResultsCursor` to inspect the
@@ -87,11 +89,26 @@ impl<T: Idx> BitSetExt<T> for ChunkedBitSet<T> {
     }
 }
 
-/// Defines the domain of a dataflow problem.
+/// A dataflow problem with an arbitrarily complex transfer function.
+///
+/// This trait specifies the lattice on which this analysis operates (the domain), its
+/// initial value at the entry point of each basic block, and various operations.
+///
+/// # Convergence
+///
+/// When implementing this trait it's possible to choose a transfer function such that the analysis
+/// does not reach fixpoint. To guarantee convergence, your transfer functions must maintain the
+/// following invariant:
+///
+/// > If the dataflow state **before** some point in the program changes to be greater
+/// than the prior state **before** that point, the dataflow state **after** that point must
+/// also change to be greater than the prior state **after** that point.
 ///
-/// This trait specifies the lattice on which this analysis operates (the domain) as well as its
-/// initial value at the entry point of each basic block.
-pub trait AnalysisDomain<'tcx> {
+/// This invariant guarantees that the dataflow state at a given point in the program increases
+/// monotonically until fixpoint is reached. Note that this monotonicity requirement only applies
+/// to the same point in the program at different points in time. The dataflow state at a given
+/// point in the program may or may not be greater than the state at any preceding point.
+pub trait Analysis<'tcx> {
     /// The type that holds the dataflow state at any given point in the program.
     type Domain: Clone + JoinSemiLattice;
 
@@ -116,25 +133,7 @@ pub trait AnalysisDomain<'tcx> {
     // block where control flow could exit the MIR body (e.g., those terminated with `return` or
     // `resume`). It's not obvious how to handle `yield` points in coroutines, however.
     fn initialize_start_block(&self, body: &mir::Body<'tcx>, state: &mut Self::Domain);
-}
 
-/// A dataflow problem with an arbitrarily complex transfer function.
-///
-/// # Convergence
-///
-/// When implementing this trait directly (not via [`GenKillAnalysis`]), it's possible to choose a
-/// transfer function such that the analysis does not reach fixpoint. To guarantee convergence,
-/// your transfer functions must maintain the following invariant:
-///
-/// > If the dataflow state **before** some point in the program changes to be greater
-/// than the prior state **before** that point, the dataflow state **after** that point must
-/// also change to be greater than the prior state **after** that point.
-///
-/// This invariant guarantees that the dataflow state at a given point in the program increases
-/// monotonically until fixpoint is reached. Note that this monotonicity requirement only applies
-/// to the same point in the program at different points in time. The dataflow state at a given
-/// point in the program may or may not be greater than the state at any preceding point.
-pub trait Analysis<'tcx>: AnalysisDomain<'tcx> {
     /// Updates the current dataflow state with the effect of evaluating a statement.
     fn apply_statement_effect(
         &mut self,
@@ -165,10 +164,12 @@ pub trait Analysis<'tcx>: AnalysisDomain<'tcx> {
     /// initialized here.
     fn apply_terminator_effect<'mir>(
         &mut self,
-        state: &mut Self::Domain,
+        _state: &mut Self::Domain,
         terminator: &'mir mir::Terminator<'tcx>,
-        location: Location,
-    ) -> TerminatorEdges<'mir, 'tcx>;
+        _location: Location,
+    ) -> TerminatorEdges<'mir, 'tcx> {
+        terminator.edges()
+    }
 
     /// Updates the current dataflow state with an effect that occurs immediately *before* the
     /// given terminator.
@@ -193,10 +194,11 @@ pub trait Analysis<'tcx>: AnalysisDomain<'tcx> {
     /// edges.
     fn apply_call_return_effect(
         &mut self,
-        state: &mut Self::Domain,
-        block: BasicBlock,
-        return_places: CallReturnPlaces<'_, 'tcx>,
-    );
+        _state: &mut Self::Domain,
+        _block: BasicBlock,
+        _return_places: CallReturnPlaces<'_, 'tcx>,
+    ) {
+    }
 
     /// Updates the current dataflow state with the effect of taking a particular branch in a
     /// `SwitchInt` terminator.
@@ -223,9 +225,7 @@ pub trait Analysis<'tcx>: AnalysisDomain<'tcx> {
 
     /// Creates an `Engine` to find the fixpoint for this dataflow problem.
     ///
-    /// You shouldn't need to override this outside this module, since the combination of the
-    /// default impl and the one for all `A: GenKillAnalysis` will do the right thing.
-    /// Its purpose is to enable method chaining like so:
+    /// You shouldn't need to override this. Its purpose is to enable method chaining like so:
     ///
     /// ```ignore (cross-crate-imports)
     /// let results = MyAnalysis::new(tcx, body)
@@ -242,164 +242,11 @@ pub trait Analysis<'tcx>: AnalysisDomain<'tcx> {
     where
         Self: Sized,
     {
-        Engine::new_generic(tcx, body, self)
-    }
-}
-
-/// A gen/kill dataflow problem.
-///
-/// Each method in this trait has a corresponding one in `Analysis`. However, the first two methods
-/// here only allow modification of the dataflow state via "gen" and "kill" operations. By defining
-/// transfer functions for each statement in this way, the transfer function for an entire basic
-/// block can be computed efficiently. The remaining methods match up with `Analysis` exactly.
-///
-/// `Analysis` is automatically implemented for all implementers of `GenKillAnalysis` via a blanket
-/// impl below.
-pub trait GenKillAnalysis<'tcx>: Analysis<'tcx> {
-    type Idx: Idx;
-
-    fn domain_size(&self, body: &mir::Body<'tcx>) -> usize;
-
-    /// See `Analysis::apply_statement_effect`. Note how the second arg differs.
-    fn statement_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        statement: &mir::Statement<'tcx>,
-        location: Location,
-    );
-
-    /// See `Analysis::apply_before_statement_effect`. Note how the second arg
-    /// differs.
-    fn before_statement_effect(
-        &mut self,
-        _trans: &mut impl GenKill<Self::Idx>,
-        _statement: &mir::Statement<'tcx>,
-        _location: Location,
-    ) {
-    }
-
-    /// See `Analysis::apply_terminator_effect`.
-    fn terminator_effect<'mir>(
-        &mut self,
-        trans: &mut Self::Domain,
-        terminator: &'mir mir::Terminator<'tcx>,
-        location: Location,
-    ) -> TerminatorEdges<'mir, 'tcx>;
-
-    /// See `Analysis::apply_before_terminator_effect`.
-    fn before_terminator_effect(
-        &mut self,
-        _trans: &mut Self::Domain,
-        _terminator: &mir::Terminator<'tcx>,
-        _location: Location,
-    ) {
-    }
-
-    /* Edge-specific effects */
-
-    /// See `Analysis::apply_call_return_effect`.
-    fn call_return_effect(
-        &mut self,
-        trans: &mut Self::Domain,
-        block: BasicBlock,
-        return_places: CallReturnPlaces<'_, 'tcx>,
-    );
-
-    /// See `Analysis::apply_switch_int_edge_effects`.
-    fn switch_int_edge_effects<G: GenKill<Self::Idx>>(
-        &mut self,
-        _block: BasicBlock,
-        _discr: &mir::Operand<'tcx>,
-        _edge_effects: &mut impl SwitchIntEdgeEffects<G>,
-    ) {
-    }
-}
-
-// Blanket impl: any impl of `GenKillAnalysis` automatically impls `Analysis`.
-impl<'tcx, A> Analysis<'tcx> for A
-where
-    A: GenKillAnalysis<'tcx>,
-    A::Domain: GenKill<A::Idx> + BitSetExt<A::Idx>,
-{
-    fn apply_statement_effect(
-        &mut self,
-        state: &mut A::Domain,
-        statement: &mir::Statement<'tcx>,
-        location: Location,
-    ) {
-        self.statement_effect(state, statement, location);
-    }
-
-    fn apply_before_statement_effect(
-        &mut self,
-        state: &mut A::Domain,
-        statement: &mir::Statement<'tcx>,
-        location: Location,
-    ) {
-        self.before_statement_effect(state, statement, location);
-    }
-
-    fn apply_terminator_effect<'mir>(
-        &mut self,
-        state: &mut A::Domain,
-        terminator: &'mir mir::Terminator<'tcx>,
-        location: Location,
-    ) -> TerminatorEdges<'mir, 'tcx> {
-        self.terminator_effect(state, terminator, location)
-    }
-
-    fn apply_before_terminator_effect(
-        &mut self,
-        state: &mut A::Domain,
-        terminator: &mir::Terminator<'tcx>,
-        location: Location,
-    ) {
-        self.before_terminator_effect(state, terminator, location);
-    }
-
-    /* Edge-specific effects */
-
-    fn apply_call_return_effect(
-        &mut self,
-        state: &mut A::Domain,
-        block: BasicBlock,
-        return_places: CallReturnPlaces<'_, 'tcx>,
-    ) {
-        self.call_return_effect(state, block, return_places);
-    }
-
-    fn apply_switch_int_edge_effects(
-        &mut self,
-        block: BasicBlock,
-        discr: &mir::Operand<'tcx>,
-        edge_effects: &mut impl SwitchIntEdgeEffects<A::Domain>,
-    ) {
-        self.switch_int_edge_effects(block, discr, edge_effects);
-    }
-
-    /* Extension methods */
-    #[inline]
-    fn into_engine<'mir>(
-        self,
-        tcx: TyCtxt<'tcx>,
-        body: &'mir mir::Body<'tcx>,
-    ) -> Engine<'mir, 'tcx, Self>
-    where
-        Self: Sized,
-    {
-        Engine::new_gen_kill(tcx, body, self)
+        Engine::new(tcx, body, self)
     }
 }
 
 /// The legal operations for a transfer function in a gen/kill problem.
-///
-/// This abstraction exists because there are two different contexts in which we call the methods in
-/// `GenKillAnalysis`. Sometimes we need to store a single transfer function that can be efficiently
-/// applied multiple times, such as when computing the cumulative transfer function for each block.
-/// These cases require a `GenKillSet`, which in turn requires two `BitSet`s of storage. Oftentimes,
-/// however, we only need to apply an effect once. In *these* cases, it is more efficient to pass the
-/// `BitSet` representing the state vector directly into the `*_effect` methods as opposed to
-/// building up a `GenKillSet` and then throwing it away.
 pub trait GenKill<T> {
     /// Inserts `elem` into the state vector.
     fn gen_(&mut self, elem: T);
@@ -422,44 +269,6 @@ pub trait GenKill<T> {
     }
 }
 
-/// Stores a transfer function for a gen/kill problem.
-///
-/// Calling `gen_`/`kill` on a `GenKillSet` will "build up" a transfer function so that it can be
-/// applied multiple times efficiently. When there are multiple calls to `gen_` and/or `kill` for
-/// the same element, the most recent one takes precedence.
-#[derive(Clone)]
-pub struct GenKillSet<T> {
-    gen_: HybridBitSet<T>,
-    kill: HybridBitSet<T>,
-}
-
-impl<T: Idx> GenKillSet<T> {
-    /// Creates a new transfer function that will leave the dataflow state unchanged.
-    pub fn identity(universe: usize) -> Self {
-        GenKillSet {
-            gen_: HybridBitSet::new_empty(universe),
-            kill: HybridBitSet::new_empty(universe),
-        }
-    }
-
-    pub fn apply(&self, state: &mut impl BitSetExt<T>) {
-        state.union(&self.gen_);
-        state.subtract(&self.kill);
-    }
-}
-
-impl<T: Idx> GenKill<T> for GenKillSet<T> {
-    fn gen_(&mut self, elem: T) {
-        self.gen_.insert(elem);
-        self.kill.remove(elem);
-    }
-
-    fn kill(&mut self, elem: T) {
-        self.kill.insert(elem);
-        self.gen_.remove(elem);
-    }
-}
-
 impl<T: Idx> GenKill<T> for BitSet<T> {
     fn gen_(&mut self, elem: T) {
         self.insert(elem);
diff --git a/compiler/rustc_mir_dataflow/src/framework/tests.rs b/compiler/rustc_mir_dataflow/src/framework/tests.rs
index 1861f4cffc7..14fb6dfb50c 100644
--- a/compiler/rustc_mir_dataflow/src/framework/tests.rs
+++ b/compiler/rustc_mir_dataflow/src/framework/tests.rs
@@ -154,7 +154,7 @@ impl<D: Direction> MockAnalysis<'_, D> {
     }
 }
 
-impl<'tcx, D: Direction> AnalysisDomain<'tcx> for MockAnalysis<'tcx, D> {
+impl<'tcx, D: Direction> Analysis<'tcx> for MockAnalysis<'tcx, D> {
     type Domain = BitSet<usize>;
     type Direction = D;
 
@@ -167,9 +167,7 @@ impl<'tcx, D: Direction> AnalysisDomain<'tcx> for MockAnalysis<'tcx, D> {
     fn initialize_start_block(&self, _: &mir::Body<'tcx>, _: &mut Self::Domain) {
         unimplemented!("This is never called since `MockAnalysis` is never iterated to fixpoint");
     }
-}
 
-impl<'tcx, D: Direction> Analysis<'tcx> for MockAnalysis<'tcx, D> {
     fn apply_statement_effect(
         &mut self,
         state: &mut Self::Domain,
@@ -210,14 +208,6 @@ impl<'tcx, D: Direction> Analysis<'tcx> for MockAnalysis<'tcx, D> {
         let idx = self.effect(Effect::Before.at_index(location.statement_index));
         assert!(state.insert(idx));
     }
-
-    fn apply_call_return_effect(
-        &mut self,
-        _state: &mut Self::Domain,
-        _block: BasicBlock,
-        _return_places: CallReturnPlaces<'_, 'tcx>,
-    ) {
-    }
 }
 
 #[derive(Clone, Copy, Debug, PartialEq, Eq)]