Move initialization dataflow impls into their own module.

compiler/rustc_mir_dataflow/src/impls/borrowed_locals.rs

@@ -1,9 +1,10 @@
-use super::*;
+use rustc_index::bit_set::BitSet;
-
-use crate::{AnalysisDomain, CallReturnPlaces, GenKill, GenKillAnalysis};
 use rustc_middle::mir::visit::Visitor;
 use rustc_middle::mir::*;
 
+use crate::framework::CallReturnPlaces;
+use crate::{AnalysisDomain, GenKill, GenKillAnalysis};
+
 /// A dataflow analysis that tracks whether a pointer or reference could possibly exist that points
 /// to a given local.
 ///
@@ -23,12 +24,12 @@ impl<'tcx> AnalysisDomain<'tcx> for MaybeBorrowedLocals {
     type Domain = BitSet<Local>;
     const NAME: &'static str = "maybe_borrowed_locals";
 
-    fn bottom_value(&self, body: &mir::Body<'tcx>) -> Self::Domain {
+    fn bottom_value(&self, body: &Body<'tcx>) -> Self::Domain {
         // bottom = unborrowed
         BitSet::new_empty(body.local_decls().len())
     }
 
-    fn initialize_start_block(&self, _: &mir::Body<'tcx>, _: &mut Self::Domain) {
+    fn initialize_start_block(&self, _: &Body<'tcx>, _: &mut Self::Domain) {
         // No locals are aliased on function entry
     }
 }
@@ -39,7 +40,7 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeBorrowedLocals {
     fn statement_effect(
         &mut self,
         trans: &mut impl GenKill<Self::Idx>,
-        statement: &mir::Statement<'tcx>,
+        statement: &Statement<'tcx>,
         location: Location,
     ) {
         self.transfer_function(trans).visit_statement(statement, location);
@@ -48,7 +49,7 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeBorrowedLocals {
     fn terminator_effect(
         &mut self,
         trans: &mut impl GenKill<Self::Idx>,
-        terminator: &mir::Terminator<'tcx>,
+        terminator: &Terminator<'tcx>,
         location: Location,
     ) {
         self.transfer_function(trans).visit_terminator(terminator, location);
@@ -57,7 +58,7 @@ impl<'tcx> GenKillAnalysis<'tcx> for MaybeBorrowedLocals {
     fn call_return_effect(
         &mut self,
         _trans: &mut impl GenKill<Self::Idx>,
-        _block: mir::BasicBlock,
+        _block: BasicBlock,
         _return_places: CallReturnPlaces<'_, 'tcx>,
     ) {
     }
@@ -82,37 +83,37 @@ where
         }
     }
 
-    fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: Location) {
+    fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) {
         self.super_rvalue(rvalue, location);
 
         match rvalue {
-            mir::Rvalue::AddressOf(_, borrowed_place) | mir::Rvalue::Ref(_, _, borrowed_place) => {
+            Rvalue::AddressOf(_, borrowed_place) | Rvalue::Ref(_, _, borrowed_place) => {
                 if !borrowed_place.is_indirect() {
                     self.trans.gen(borrowed_place.local);
                 }
             }
 
-            mir::Rvalue::Cast(..)
+            Rvalue::Cast(..)
-            | mir::Rvalue::ShallowInitBox(..)
+            | Rvalue::ShallowInitBox(..)
-            | mir::Rvalue::Use(..)
+            | Rvalue::Use(..)
-            | mir::Rvalue::ThreadLocalRef(..)
+            | Rvalue::ThreadLocalRef(..)
-            | mir::Rvalue::Repeat(..)
+            | Rvalue::Repeat(..)
-            | mir::Rvalue::Len(..)
+            | Rvalue::Len(..)
-            | mir::Rvalue::BinaryOp(..)
+            | Rvalue::BinaryOp(..)
-            | mir::Rvalue::CheckedBinaryOp(..)
+            | Rvalue::CheckedBinaryOp(..)
-            | mir::Rvalue::NullaryOp(..)
+            | Rvalue::NullaryOp(..)
-            | mir::Rvalue::UnaryOp(..)
+            | Rvalue::UnaryOp(..)
-            | mir::Rvalue::Discriminant(..)
+            | Rvalue::Discriminant(..)
-            | mir::Rvalue::Aggregate(..)
+            | Rvalue::Aggregate(..)
-            | mir::Rvalue::CopyForDeref(..) => {}
+            | Rvalue::CopyForDeref(..) => {}
         }
     }
 
-    fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Location) {
+    fn visit_terminator(&mut self, terminator: &Terminator<'tcx>, location: Location) {
         self.super_terminator(terminator, location);
 
         match terminator.kind {
-            mir::TerminatorKind::Drop { place: dropped_place, .. } => {
+            TerminatorKind::Drop { place: dropped_place, .. } => {
                 // Drop terminators may call custom drop glue (`Drop::drop`), which takes `&mut
                 // self` as a parameter. In the general case, a drop impl could launder that
                 // reference into the surrounding environment through a raw pointer, thus creating

compiler/rustc_mir_dataflow/src/impls/initialized.rs

@@ -0,0 +1,705 @@
+use rustc_index::bit_set::{BitSet, ChunkedBitSet};
+use rustc_index::Idx;
+use rustc_middle::mir::{self, Body, Location};
+use rustc_middle::ty::{self, TyCtxt};
+
+use crate::drop_flag_effects_for_function_entry;
+use crate::drop_flag_effects_for_location;
+use crate::elaborate_drops::DropFlagState;
+use crate::framework::{CallReturnPlaces, SwitchIntEdgeEffects};
+use crate::move_paths::{HasMoveData, InitIndex, InitKind, LookupResult, MoveData, MovePathIndex};
+use crate::on_lookup_result_bits;
+use crate::MoveDataParamEnv;
+use crate::{drop_flag_effects, on_all_children_bits};
+use crate::{lattice, AnalysisDomain, GenKill, GenKillAnalysis};
+
+/// `MaybeInitializedPlaces` tracks all places that might be
+/// initialized upon reaching a particular point in the control flow
+/// for a function.
+///
+/// For example, in code like the following, we have corresponding
+/// dataflow information shown in the right-hand comments.
+///
+/// ```rust
+/// struct S;
+/// fn foo(pred: bool) {                        // maybe-init:
+///                                             // {}
+///     let a = S; let mut b = S; let c; let d; // {a, b}
+///
+///     if pred {
+///         drop(a);                            // {   b}
+///         b = S;                              // {   b}
+///
+///     } else {
+///         drop(b);                            // {a}
+///         d = S;                              // {a,       d}
+///
+///     }                                       // {a, b,    d}
+///
+///     c = S;                                  // {a, b, c, d}
+/// }
+/// ```
+///
+/// To determine whether a place *must* be initialized at a
+/// particular control-flow point, one can take the set-difference
+/// between this data and the data from `MaybeUninitializedPlaces` at the
+/// corresponding control-flow point.
+///
+/// Similarly, at a given `drop` statement, the set-intersection
+/// between this data and `MaybeUninitializedPlaces` yields the set of
+/// places that would require a dynamic drop-flag at that statement.
+pub struct MaybeInitializedPlaces<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    body: &'a Body<'tcx>,
+    mdpe: &'a MoveDataParamEnv<'tcx>,
+}
+
+impl<'a, 'tcx> MaybeInitializedPlaces<'a, 'tcx> {
+    pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self {
+        MaybeInitializedPlaces { tcx, body, mdpe }
+    }
+}
+
+impl<'a, 'tcx> HasMoveData<'tcx> for MaybeInitializedPlaces<'a, 'tcx> {
+    fn move_data(&self) -> &MoveData<'tcx> {
+        &self.mdpe.move_data
+    }
+}
+
+/// `MaybeUninitializedPlaces` tracks all places that might be
+/// uninitialized upon reaching a particular point in the control flow
+/// for a function.
+///
+/// For example, in code like the following, we have corresponding
+/// dataflow information shown in the right-hand comments.
+///
+/// ```rust
+/// struct S;
+/// fn foo(pred: bool) {                        // maybe-uninit:
+///                                             // {a, b, c, d}
+///     let a = S; let mut b = S; let c; let d; // {      c, d}
+///
+///     if pred {
+///         drop(a);                            // {a,    c, d}
+///         b = S;                              // {a,    c, d}
+///
+///     } else {
+///         drop(b);                            // {   b, c, d}
+///         d = S;                              // {   b, c   }
+///
+///     }                                       // {a, b, c, d}
+///
+///     c = S;                                  // {a, b,    d}
+/// }
+/// ```
+///
+/// To determine whether a place *must* be uninitialized at a
+/// particular control-flow point, one can take the set-difference
+/// between this data and the data from `MaybeInitializedPlaces` at the
+/// corresponding control-flow point.
+///
+/// Similarly, at a given `drop` statement, the set-intersection
+/// between this data and `MaybeInitializedPlaces` yields the set of
+/// places that would require a dynamic drop-flag at that statement.
+pub struct MaybeUninitializedPlaces<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    body: &'a Body<'tcx>,
+    mdpe: &'a MoveDataParamEnv<'tcx>,
+
+    mark_inactive_variants_as_uninit: bool,
+}
+
+impl<'a, 'tcx> MaybeUninitializedPlaces<'a, 'tcx> {
+    pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self {
+        MaybeUninitializedPlaces { tcx, body, mdpe, mark_inactive_variants_as_uninit: false }
+    }
+
+    /// Causes inactive enum variants to be marked as "maybe uninitialized" after a switch on an
+    /// enum discriminant.
+    ///
+    /// This is correct in a vacuum but is not the default because it causes problems in the borrow
+    /// checker, where this information gets propagated along `FakeEdge`s.
+    pub fn mark_inactive_variants_as_uninit(mut self) -> Self {
+        self.mark_inactive_variants_as_uninit = true;
+        self
+    }
+}
+
+impl<'a, 'tcx> HasMoveData<'tcx> for MaybeUninitializedPlaces<'a, 'tcx> {
+    fn move_data(&self) -> &MoveData<'tcx> {
+        &self.mdpe.move_data
+    }
+}
+
+/// `DefinitelyInitializedPlaces` tracks all places that are definitely
+/// initialized upon reaching a particular point in the control flow
+/// for a function.
+///
+/// For example, in code like the following, we have corresponding
+/// dataflow information shown in the right-hand comments.
+///
+/// ```rust
+/// struct S;
+/// fn foo(pred: bool) {                        // definite-init:
+///                                             // {          }
+///     let a = S; let mut b = S; let c; let d; // {a, b      }
+///
+///     if pred {
+///         drop(a);                            // {   b,     }
+///         b = S;                              // {   b,     }
+///
+///     } else {
+///         drop(b);                            // {a,        }
+///         d = S;                              // {a,       d}
+///
+///     }                                       // {          }
+///
+///     c = S;                                  // {       c  }
+/// }
+/// ```
+///
+/// To determine whether a place *may* be uninitialized at a
+/// particular control-flow point, one can take the set-complement
+/// of this data.
+///
+/// Similarly, at a given `drop` statement, the set-difference between
+/// this data and `MaybeInitializedPlaces` yields the set of places
+/// that would require a dynamic drop-flag at that statement.
+pub struct DefinitelyInitializedPlaces<'a, 'tcx> {
+    tcx: TyCtxt<'tcx>,
+    body: &'a Body<'tcx>,
+    mdpe: &'a MoveDataParamEnv<'tcx>,
+}
+
+impl<'a, 'tcx> DefinitelyInitializedPlaces<'a, 'tcx> {
+    pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self {
+        DefinitelyInitializedPlaces { tcx, body, mdpe }
+    }
+}
+
+impl<'a, 'tcx> HasMoveData<'tcx> for DefinitelyInitializedPlaces<'a, 'tcx> {
+    fn move_data(&self) -> &MoveData<'tcx> {
+        &self.mdpe.move_data
+    }
+}
+
+/// `EverInitializedPlaces` tracks all places that might have ever been
+/// initialized upon reaching a particular point in the control flow
+/// for a function, without an intervening `StorageDead`.
+///
+/// This dataflow is used to determine if an immutable local variable may
+/// be assigned to.
+///
+/// For example, in code like the following, we have corresponding
+/// dataflow information shown in the right-hand comments.
+///
+/// ```rust
+/// struct S;
+/// fn foo(pred: bool) {                        // ever-init:
+///                                             // {          }
+///     let a = S; let mut b = S; let c; let d; // {a, b      }
+///
+///     if pred {
+///         drop(a);                            // {a, b,     }
+///         b = S;                              // {a, b,     }
+///
+///     } else {
+///         drop(b);                            // {a, b,      }
+///         d = S;                              // {a, b,    d }
+///
+///     }                                       // {a, b,    d }
+///
+///     c = S;                                  // {a, b, c, d }
+/// }
+/// ```
+pub struct EverInitializedPlaces<'a, 'tcx> {
+    #[allow(dead_code)]
+    tcx: TyCtxt<'tcx>,
+    body: &'a Body<'tcx>,
+    mdpe: &'a MoveDataParamEnv<'tcx>,
+}
+
+impl<'a, 'tcx> EverInitializedPlaces<'a, 'tcx> {
+    pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self {
+        EverInitializedPlaces { tcx, body, mdpe }
+    }
+}
+
+impl<'a, 'tcx> HasMoveData<'tcx> for EverInitializedPlaces<'a, 'tcx> {
+    fn move_data(&self) -> &MoveData<'tcx> {
+        &self.mdpe.move_data
+    }
+}
+
+impl<'a, 'tcx> MaybeInitializedPlaces<'a, 'tcx> {
+    fn update_bits(
+        trans: &mut impl GenKill<MovePathIndex>,
+        path: MovePathIndex,
+        state: DropFlagState,
+    ) {
+        match state {
+            DropFlagState::Absent => trans.kill(path),
+            DropFlagState::Present => trans.gen(path),
+        }
+    }
+}
+
+impl<'a, 'tcx> MaybeUninitializedPlaces<'a, 'tcx> {
+    fn update_bits(
+        trans: &mut impl GenKill<MovePathIndex>,
+        path: MovePathIndex,
+        state: DropFlagState,
+    ) {
+        match state {
+            DropFlagState::Absent => trans.gen(path),
+            DropFlagState::Present => trans.kill(path),
+        }
+    }
+}
+
+impl<'a, 'tcx> DefinitelyInitializedPlaces<'a, 'tcx> {
+    fn update_bits(
+        trans: &mut impl GenKill<MovePathIndex>,
+        path: MovePathIndex,
+        state: DropFlagState,
+    ) {
+        match state {
+            DropFlagState::Absent => trans.kill(path),
+            DropFlagState::Present => trans.gen(path),
+        }
+    }
+}
+
+impl<'tcx> AnalysisDomain<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
+    type Domain = ChunkedBitSet<MovePathIndex>;
+    const NAME: &'static str = "maybe_init";
+
+    fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
+        // bottom = uninitialized
+        ChunkedBitSet::new_empty(self.move_data().move_paths.len())
+    }
+
+    fn initialize_start_block(&self, _: &mir::Body<'tcx>, state: &mut Self::Domain) {
+        drop_flag_effects_for_function_entry(self.tcx, self.body, self.mdpe, |path, s| {
+            assert!(s == DropFlagState::Present);
+            state.insert(path);
+        });
+    }
+}
+
+impl<'tcx> GenKillAnalysis<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
+    type Idx = MovePathIndex;
+
+    fn statement_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        statement: &mir::Statement<'tcx>,
+        location: Location,
+    ) {
+        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
+            Self::update_bits(trans, path, s)
+        });
+
+        // Mark all places as "maybe init" if they are mutably borrowed. See #90752.
+        if self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration
+            && let Some((_, rvalue)) = statement.kind.as_assign()
+            && let mir::Rvalue::Ref(_, mir::BorrowKind::Mut { .. }, place)
+                // FIXME: Does `&raw const foo` allow mutation? See #90413.
+                | mir::Rvalue::AddressOf(_, place) = rvalue
+            && let LookupResult::Exact(mpi) = self.move_data().rev_lookup.find(place.as_ref())
+        {
+            on_all_children_bits(self.tcx, self.body, self.move_data(), mpi, |child| {
+                trans.gen(child);
+            })
+        }
+    }
+
+    fn terminator_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _: &mir::Terminator<'tcx>,
+        location: Location,
+    ) {
+        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
+            Self::update_bits(trans, path, s)
+        });
+    }
+
+    fn call_return_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _block: mir::BasicBlock,
+        return_places: CallReturnPlaces<'_, 'tcx>,
+    ) {
+        return_places.for_each(|place| {
+            // when a call returns successfully, that means we need to set
+            // the bits for that dest_place to 1 (initialized).
+            on_lookup_result_bits(
+                self.tcx,
+                self.body,
+                self.move_data(),
+                self.move_data().rev_lookup.find(place.as_ref()),
+                |mpi| {
+                    trans.gen(mpi);
+                },
+            );
+        });
+    }
+
+    fn switch_int_edge_effects<G: GenKill<Self::Idx>>(
+        &mut self,
+        block: mir::BasicBlock,
+        discr: &mir::Operand<'tcx>,
+        edge_effects: &mut impl SwitchIntEdgeEffects<G>,
+    ) {
+        if !self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration {
+            return;
+        }
+
+        let enum_ = discr.place().and_then(|discr| {
+            switch_on_enum_discriminant(self.tcx, &self.body, &self.body[block], discr)
+        });
+
+        let Some((enum_place, enum_def)) = enum_ else {
+            return;
+        };
+
+        let mut discriminants = enum_def.discriminants(self.tcx);
+        edge_effects.apply(|trans, edge| {
+            let Some(value) = edge.value else {
+                return;
+            };
+
+            // MIR building adds discriminants to the `values` array in the same order as they
+            // are yielded by `AdtDef::discriminants`. We rely on this to match each
+            // discriminant in `values` to its corresponding variant in linear time.
+            let (variant, _) = discriminants
+                .find(|&(_, discr)| discr.val == value)
+                .expect("Order of `AdtDef::discriminants` differed from `SwitchInt::values`");
+
+            // Kill all move paths that correspond to variants we know to be inactive along this
+            // particular outgoing edge of a `SwitchInt`.
+            drop_flag_effects::on_all_inactive_variants(
+                self.tcx,
+                self.body,
+                self.move_data(),
+                enum_place,
+                variant,
+                |mpi| trans.kill(mpi),
+            );
+        });
+    }
+}
+
+impl<'tcx> AnalysisDomain<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> {
+    type Domain = ChunkedBitSet<MovePathIndex>;
+
+    const NAME: &'static str = "maybe_uninit";
+
+    fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
+        // bottom = initialized (start_block_effect counters this at outset)
+        ChunkedBitSet::new_empty(self.move_data().move_paths.len())
+    }
+
+    // sets on_entry bits for Arg places
+    fn initialize_start_block(&self, _: &mir::Body<'tcx>, state: &mut Self::Domain) {
+        // set all bits to 1 (uninit) before gathering counter-evidence
+        state.insert_all();
+
+        drop_flag_effects_for_function_entry(self.tcx, self.body, self.mdpe, |path, s| {
+            assert!(s == DropFlagState::Present);
+            state.remove(path);
+        });
+    }
+}
+
+impl<'tcx> GenKillAnalysis<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> {
+    type Idx = MovePathIndex;
+
+    fn statement_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _statement: &mir::Statement<'tcx>,
+        location: Location,
+    ) {
+        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
+            Self::update_bits(trans, path, s)
+        });
+
+        // Unlike in `MaybeInitializedPlaces` above, we don't need to change the state when a
+        // mutable borrow occurs. Places cannot become uninitialized through a mutable reference.
+    }
+
+    fn terminator_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _terminator: &mir::Terminator<'tcx>,
+        location: Location,
+    ) {
+        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
+            Self::update_bits(trans, path, s)
+        });
+    }
+
+    fn call_return_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _block: mir::BasicBlock,
+        return_places: CallReturnPlaces<'_, 'tcx>,
+    ) {
+        return_places.for_each(|place| {
+            // when a call returns successfully, that means we need to set
+            // the bits for that dest_place to 0 (initialized).
+            on_lookup_result_bits(
+                self.tcx,
+                self.body,
+                self.move_data(),
+                self.move_data().rev_lookup.find(place.as_ref()),
+                |mpi| {
+                    trans.kill(mpi);
+                },
+            );
+        });
+    }
+
+    fn switch_int_edge_effects<G: GenKill<Self::Idx>>(
+        &mut self,
+        block: mir::BasicBlock,
+        discr: &mir::Operand<'tcx>,
+        edge_effects: &mut impl SwitchIntEdgeEffects<G>,
+    ) {
+        if !self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration {
+            return;
+        }
+
+        if !self.mark_inactive_variants_as_uninit {
+            return;
+        }
+
+        let enum_ = discr.place().and_then(|discr| {
+            switch_on_enum_discriminant(self.tcx, &self.body, &self.body[block], discr)
+        });
+
+        let Some((enum_place, enum_def)) = enum_ else {
+            return;
+        };
+
+        let mut discriminants = enum_def.discriminants(self.tcx);
+        edge_effects.apply(|trans, edge| {
+            let Some(value) = edge.value else {
+                return;
+            };
+
+            // MIR building adds discriminants to the `values` array in the same order as they
+            // are yielded by `AdtDef::discriminants`. We rely on this to match each
+            // discriminant in `values` to its corresponding variant in linear time.
+            let (variant, _) = discriminants
+                .find(|&(_, discr)| discr.val == value)
+                .expect("Order of `AdtDef::discriminants` differed from `SwitchInt::values`");
+
+            // Mark all move paths that correspond to variants other than this one as maybe
+            // uninitialized (in reality, they are *definitely* uninitialized).
+            drop_flag_effects::on_all_inactive_variants(
+                self.tcx,
+                self.body,
+                self.move_data(),
+                enum_place,
+                variant,
+                |mpi| trans.gen(mpi),
+            );
+        });
+    }
+}
+
+impl<'a, 'tcx> AnalysisDomain<'tcx> for DefinitelyInitializedPlaces<'a, 'tcx> {
+    /// Use set intersection as the join operator.
+    type Domain = lattice::Dual<BitSet<MovePathIndex>>;
+
+    const NAME: &'static str = "definite_init";
+
+    fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
+        // bottom = initialized (start_block_effect counters this at outset)
+        lattice::Dual(BitSet::new_filled(self.move_data().move_paths.len()))
+    }
+
+    // sets on_entry bits for Arg places
+    fn initialize_start_block(&self, _: &mir::Body<'tcx>, state: &mut Self::Domain) {
+        state.0.clear();
+
+        drop_flag_effects_for_function_entry(self.tcx, self.body, self.mdpe, |path, s| {
+            assert!(s == DropFlagState::Present);
+            state.0.insert(path);
+        });
+    }
+}
+
+impl<'tcx> GenKillAnalysis<'tcx> for DefinitelyInitializedPlaces<'_, 'tcx> {
+    type Idx = MovePathIndex;
+
+    fn statement_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _statement: &mir::Statement<'tcx>,
+        location: Location,
+    ) {
+        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
+            Self::update_bits(trans, path, s)
+        })
+    }
+
+    fn terminator_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _terminator: &mir::Terminator<'tcx>,
+        location: Location,
+    ) {
+        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
+            Self::update_bits(trans, path, s)
+        })
+    }
+
+    fn call_return_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _block: mir::BasicBlock,
+        return_places: CallReturnPlaces<'_, 'tcx>,
+    ) {
+        return_places.for_each(|place| {
+            // when a call returns successfully, that means we need to set
+            // the bits for that dest_place to 1 (initialized).
+            on_lookup_result_bits(
+                self.tcx,
+                self.body,
+                self.move_data(),
+                self.move_data().rev_lookup.find(place.as_ref()),
+                |mpi| {
+                    trans.gen(mpi);
+                },
+            );
+        });
+    }
+}
+
+impl<'tcx> AnalysisDomain<'tcx> for EverInitializedPlaces<'_, 'tcx> {
+    type Domain = ChunkedBitSet<InitIndex>;
+
+    const NAME: &'static str = "ever_init";
+
+    fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
+        // bottom = no initialized variables by default
+        ChunkedBitSet::new_empty(self.move_data().inits.len())
+    }
+
+    fn initialize_start_block(&self, body: &mir::Body<'tcx>, state: &mut Self::Domain) {
+        for arg_init in 0..body.arg_count {
+            state.insert(InitIndex::new(arg_init));
+        }
+    }
+}
+
+impl<'tcx> GenKillAnalysis<'tcx> for EverInitializedPlaces<'_, 'tcx> {
+    type Idx = InitIndex;
+
+    #[instrument(skip(self, trans), level = "debug")]
+    fn statement_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        stmt: &mir::Statement<'tcx>,
+        location: Location,
+    ) {
+        let move_data = self.move_data();
+        let init_path_map = &move_data.init_path_map;
+        let init_loc_map = &move_data.init_loc_map;
+        let rev_lookup = &move_data.rev_lookup;
+
+        debug!("initializes move_indexes {:?}", &init_loc_map[location]);
+        trans.gen_all(init_loc_map[location].iter().copied());
+
+        if let mir::StatementKind::StorageDead(local) = stmt.kind {
+            // End inits for StorageDead, so that an immutable variable can
+            // be reinitialized on the next iteration of the loop.
+            let move_path_index = rev_lookup.find_local(local);
+            debug!("clears the ever initialized status of {:?}", init_path_map[move_path_index]);
+            trans.kill_all(init_path_map[move_path_index].iter().copied());
+        }
+    }
+
+    #[instrument(skip(self, trans, _terminator), level = "debug")]
+    fn terminator_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        _terminator: &mir::Terminator<'tcx>,
+        location: Location,
+    ) {
+        let (body, move_data) = (self.body, self.move_data());
+        let term = body[location.block].terminator();
+        let init_loc_map = &move_data.init_loc_map;
+        debug!(?term);
+        debug!("initializes move_indexes {:?}", init_loc_map[location]);
+        trans.gen_all(
+            init_loc_map[location]
+                .iter()
+                .filter(|init_index| {
+                    move_data.inits[**init_index].kind != InitKind::NonPanicPathOnly
+                })
+                .copied(),
+        );
+    }
+
+    fn call_return_effect(
+        &mut self,
+        trans: &mut impl GenKill<Self::Idx>,
+        block: mir::BasicBlock,
+        _return_places: CallReturnPlaces<'_, 'tcx>,
+    ) {
+        let move_data = self.move_data();
+        let init_loc_map = &move_data.init_loc_map;
+
+        let call_loc = self.body.terminator_loc(block);
+        for init_index in &init_loc_map[call_loc] {
+            trans.gen(*init_index);
+        }
+    }
+}
+
+/// Inspect a `SwitchInt`-terminated basic block to see if the condition of that `SwitchInt` is
+/// an enum discriminant.
+///
+/// We expect such blocks to have a call to `discriminant` as their last statement like so:
+///
+/// ```text
+/// ...
+/// _42 = discriminant(_1)
+/// SwitchInt(_42, ..)
+/// ```
+///
+/// If the basic block matches this pattern, this function returns the place corresponding to the
+/// enum (`_1` in the example above) as well as the `AdtDef` of that enum.
+fn switch_on_enum_discriminant<'mir, 'tcx>(
+    tcx: TyCtxt<'tcx>,
+    body: &'mir mir::Body<'tcx>,
+    block: &'mir mir::BasicBlockData<'tcx>,
+    switch_on: mir::Place<'tcx>,
+) -> Option<(mir::Place<'tcx>, ty::AdtDef<'tcx>)> {
+    for statement in block.statements.iter().rev() {
+        match &statement.kind {
+            mir::StatementKind::Assign(box (lhs, mir::Rvalue::Discriminant(discriminated)))
+                if *lhs == switch_on =>
+            {
+                match discriminated.ty(body, tcx).ty.kind() {
+                    ty::Adt(def, _) => return Some((*discriminated, *def)),
+
+                    // `Rvalue::Discriminant` is also used to get the active yield point for a
+                    // generator, but we do not need edge-specific effects in that case. This may
+                    // change in the future.
+                    ty::Generator(..) => return None,
+
+                    t => bug!("`discriminant` called on unexpected type {:?}", t),
+                }
+            }
+            mir::StatementKind::Coverage(_) => continue,
+            _ => return None,
+        }
+    }
+    None
+}

compiler/rustc_mir_dataflow/src/impls/mod.rs

@@ -2,719 +2,18 @@
 //! bitvectors attached to each basic block, represented via a
 //! zero-sized structure.
 
-use rustc_index::bit_set::{BitSet, ChunkedBitSet};
-use rustc_index::Idx;
-use rustc_middle::mir::{self, Body, Location};
-use rustc_middle::ty::{self, TyCtxt};
-
-use crate::drop_flag_effects_for_function_entry;
-use crate::drop_flag_effects_for_location;
-use crate::elaborate_drops::DropFlagState;
-use crate::framework::{CallReturnPlaces, SwitchIntEdgeEffects};
-use crate::move_paths::{HasMoveData, InitIndex, InitKind, LookupResult, MoveData, MovePathIndex};
-use crate::on_lookup_result_bits;
-use crate::MoveDataParamEnv;
-use crate::{drop_flag_effects, on_all_children_bits};
-use crate::{lattice, AnalysisDomain, GenKill, GenKillAnalysis};
-
 mod borrowed_locals;
+mod initialized;
 mod liveness;
 mod storage_liveness;
 
 pub use self::borrowed_locals::borrowed_locals;
 pub use self::borrowed_locals::MaybeBorrowedLocals;
+pub use self::initialized::{
+    DefinitelyInitializedPlaces, EverInitializedPlaces, MaybeInitializedPlaces,
+    MaybeUninitializedPlaces,
+};
 pub use self::liveness::MaybeLiveLocals;
 pub use self::liveness::MaybeTransitiveLiveLocals;
 pub use self::liveness::TransferFunction as LivenessTransferFunction;
 pub use self::storage_liveness::{MaybeRequiresStorage, MaybeStorageDead, MaybeStorageLive};
-
-/// `MaybeInitializedPlaces` tracks all places that might be
-/// initialized upon reaching a particular point in the control flow
-/// for a function.
-///
-/// For example, in code like the following, we have corresponding
-/// dataflow information shown in the right-hand comments.
-///
-/// ```rust
-/// struct S;
-/// fn foo(pred: bool) {                        // maybe-init:
-///                                             // {}
-///     let a = S; let mut b = S; let c; let d; // {a, b}
-///
-///     if pred {
-///         drop(a);                            // {   b}
-///         b = S;                              // {   b}
-///
-///     } else {
-///         drop(b);                            // {a}
-///         d = S;                              // {a,       d}
-///
-///     }                                       // {a, b,    d}
-///
-///     c = S;                                  // {a, b, c, d}
-/// }
-/// ```
-///
-/// To determine whether a place *must* be initialized at a
-/// particular control-flow point, one can take the set-difference
-/// between this data and the data from `MaybeUninitializedPlaces` at the
-/// corresponding control-flow point.
-///
-/// Similarly, at a given `drop` statement, the set-intersection
-/// between this data and `MaybeUninitializedPlaces` yields the set of
-/// places that would require a dynamic drop-flag at that statement.
-pub struct MaybeInitializedPlaces<'a, 'tcx> {
-    tcx: TyCtxt<'tcx>,
-    body: &'a Body<'tcx>,
-    mdpe: &'a MoveDataParamEnv<'tcx>,
-}
-
-impl<'a, 'tcx> MaybeInitializedPlaces<'a, 'tcx> {
-    pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self {
-        MaybeInitializedPlaces { tcx, body, mdpe }
-    }
-}
-
-impl<'a, 'tcx> HasMoveData<'tcx> for MaybeInitializedPlaces<'a, 'tcx> {
-    fn move_data(&self) -> &MoveData<'tcx> {
-        &self.mdpe.move_data
-    }
-}
-
-/// `MaybeUninitializedPlaces` tracks all places that might be
-/// uninitialized upon reaching a particular point in the control flow
-/// for a function.
-///
-/// For example, in code like the following, we have corresponding
-/// dataflow information shown in the right-hand comments.
-///
-/// ```rust
-/// struct S;
-/// fn foo(pred: bool) {                        // maybe-uninit:
-///                                             // {a, b, c, d}
-///     let a = S; let mut b = S; let c; let d; // {      c, d}
-///
-///     if pred {
-///         drop(a);                            // {a,    c, d}
-///         b = S;                              // {a,    c, d}
-///
-///     } else {
-///         drop(b);                            // {   b, c, d}
-///         d = S;                              // {   b, c   }
-///
-///     }                                       // {a, b, c, d}
-///
-///     c = S;                                  // {a, b,    d}
-/// }
-/// ```
-///
-/// To determine whether a place *must* be uninitialized at a
-/// particular control-flow point, one can take the set-difference
-/// between this data and the data from `MaybeInitializedPlaces` at the
-/// corresponding control-flow point.
-///
-/// Similarly, at a given `drop` statement, the set-intersection
-/// between this data and `MaybeInitializedPlaces` yields the set of
-/// places that would require a dynamic drop-flag at that statement.
-pub struct MaybeUninitializedPlaces<'a, 'tcx> {
-    tcx: TyCtxt<'tcx>,
-    body: &'a Body<'tcx>,
-    mdpe: &'a MoveDataParamEnv<'tcx>,
-
-    mark_inactive_variants_as_uninit: bool,
-}
-
-impl<'a, 'tcx> MaybeUninitializedPlaces<'a, 'tcx> {
-    pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self {
-        MaybeUninitializedPlaces { tcx, body, mdpe, mark_inactive_variants_as_uninit: false }
-    }
-
-    /// Causes inactive enum variants to be marked as "maybe uninitialized" after a switch on an
-    /// enum discriminant.
-    ///
-    /// This is correct in a vacuum but is not the default because it causes problems in the borrow
-    /// checker, where this information gets propagated along `FakeEdge`s.
-    pub fn mark_inactive_variants_as_uninit(mut self) -> Self {
-        self.mark_inactive_variants_as_uninit = true;
-        self
-    }
-}
-
-impl<'a, 'tcx> HasMoveData<'tcx> for MaybeUninitializedPlaces<'a, 'tcx> {
-    fn move_data(&self) -> &MoveData<'tcx> {
-        &self.mdpe.move_data
-    }
-}
-
-/// `DefinitelyInitializedPlaces` tracks all places that are definitely
-/// initialized upon reaching a particular point in the control flow
-/// for a function.
-///
-/// For example, in code like the following, we have corresponding
-/// dataflow information shown in the right-hand comments.
-///
-/// ```rust
-/// struct S;
-/// fn foo(pred: bool) {                        // definite-init:
-///                                             // {          }
-///     let a = S; let mut b = S; let c; let d; // {a, b      }
-///
-///     if pred {
-///         drop(a);                            // {   b,     }
-///         b = S;                              // {   b,     }
-///
-///     } else {
-///         drop(b);                            // {a,        }
-///         d = S;                              // {a,       d}
-///
-///     }                                       // {          }
-///
-///     c = S;                                  // {       c  }
-/// }
-/// ```
-///
-/// To determine whether a place *may* be uninitialized at a
-/// particular control-flow point, one can take the set-complement
-/// of this data.
-///
-/// Similarly, at a given `drop` statement, the set-difference between
-/// this data and `MaybeInitializedPlaces` yields the set of places
-/// that would require a dynamic drop-flag at that statement.
-pub struct DefinitelyInitializedPlaces<'a, 'tcx> {
-    tcx: TyCtxt<'tcx>,
-    body: &'a Body<'tcx>,
-    mdpe: &'a MoveDataParamEnv<'tcx>,
-}
-
-impl<'a, 'tcx> DefinitelyInitializedPlaces<'a, 'tcx> {
-    pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self {
-        DefinitelyInitializedPlaces { tcx, body, mdpe }
-    }
-}
-
-impl<'a, 'tcx> HasMoveData<'tcx> for DefinitelyInitializedPlaces<'a, 'tcx> {
-    fn move_data(&self) -> &MoveData<'tcx> {
-        &self.mdpe.move_data
-    }
-}
-
-/// `EverInitializedPlaces` tracks all places that might have ever been
-/// initialized upon reaching a particular point in the control flow
-/// for a function, without an intervening `StorageDead`.
-///
-/// This dataflow is used to determine if an immutable local variable may
-/// be assigned to.
-///
-/// For example, in code like the following, we have corresponding
-/// dataflow information shown in the right-hand comments.
-///
-/// ```rust
-/// struct S;
-/// fn foo(pred: bool) {                        // ever-init:
-///                                             // {          }
-///     let a = S; let mut b = S; let c; let d; // {a, b      }
-///
-///     if pred {
-///         drop(a);                            // {a, b,     }
-///         b = S;                              // {a, b,     }
-///
-///     } else {
-///         drop(b);                            // {a, b,      }
-///         d = S;                              // {a, b,    d }
-///
-///     }                                       // {a, b,    d }
-///
-///     c = S;                                  // {a, b, c, d }
-/// }
-/// ```
-pub struct EverInitializedPlaces<'a, 'tcx> {
-    #[allow(dead_code)]
-    tcx: TyCtxt<'tcx>,
-    body: &'a Body<'tcx>,
-    mdpe: &'a MoveDataParamEnv<'tcx>,
-}
-
-impl<'a, 'tcx> EverInitializedPlaces<'a, 'tcx> {
-    pub fn new(tcx: TyCtxt<'tcx>, body: &'a Body<'tcx>, mdpe: &'a MoveDataParamEnv<'tcx>) -> Self {
-        EverInitializedPlaces { tcx, body, mdpe }
-    }
-}
-
-impl<'a, 'tcx> HasMoveData<'tcx> for EverInitializedPlaces<'a, 'tcx> {
-    fn move_data(&self) -> &MoveData<'tcx> {
-        &self.mdpe.move_data
-    }
-}
-
-impl<'a, 'tcx> MaybeInitializedPlaces<'a, 'tcx> {
-    fn update_bits(
-        trans: &mut impl GenKill<MovePathIndex>,
-        path: MovePathIndex,
-        state: DropFlagState,
-    ) {
-        match state {
-            DropFlagState::Absent => trans.kill(path),
-            DropFlagState::Present => trans.gen(path),
-        }
-    }
-}
-
-impl<'a, 'tcx> MaybeUninitializedPlaces<'a, 'tcx> {
-    fn update_bits(
-        trans: &mut impl GenKill<MovePathIndex>,
-        path: MovePathIndex,
-        state: DropFlagState,
-    ) {
-        match state {
-            DropFlagState::Absent => trans.gen(path),
-            DropFlagState::Present => trans.kill(path),
-        }
-    }
-}
-
-impl<'a, 'tcx> DefinitelyInitializedPlaces<'a, 'tcx> {
-    fn update_bits(
-        trans: &mut impl GenKill<MovePathIndex>,
-        path: MovePathIndex,
-        state: DropFlagState,
-    ) {
-        match state {
-            DropFlagState::Absent => trans.kill(path),
-            DropFlagState::Present => trans.gen(path),
-        }
-    }
-}
-
-impl<'tcx> AnalysisDomain<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
-    type Domain = ChunkedBitSet<MovePathIndex>;
-    const NAME: &'static str = "maybe_init";
-
-    fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
-        // bottom = uninitialized
-        ChunkedBitSet::new_empty(self.move_data().move_paths.len())
-    }
-
-    fn initialize_start_block(&self, _: &mir::Body<'tcx>, state: &mut Self::Domain) {
-        drop_flag_effects_for_function_entry(self.tcx, self.body, self.mdpe, |path, s| {
-            assert!(s == DropFlagState::Present);
-            state.insert(path);
-        });
-    }
-}
-
-impl<'tcx> GenKillAnalysis<'tcx> for MaybeInitializedPlaces<'_, 'tcx> {
-    type Idx = MovePathIndex;
-
-    fn statement_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        statement: &mir::Statement<'tcx>,
-        location: Location,
-    ) {
-        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
-            Self::update_bits(trans, path, s)
-        });
-
-        // Mark all places as "maybe init" if they are mutably borrowed. See #90752.
-        if self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration
-            && let Some((_, rvalue)) = statement.kind.as_assign()
-            && let mir::Rvalue::Ref(_, mir::BorrowKind::Mut { .. }, place)
-                // FIXME: Does `&raw const foo` allow mutation? See #90413.
-                | mir::Rvalue::AddressOf(_, place) = rvalue
-            && let LookupResult::Exact(mpi) = self.move_data().rev_lookup.find(place.as_ref())
-        {
-            on_all_children_bits(self.tcx, self.body, self.move_data(), mpi, |child| {
-                trans.gen(child);
-            })
-        }
-    }
-
-    fn terminator_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        _: &mir::Terminator<'tcx>,
-        location: Location,
-    ) {
-        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
-            Self::update_bits(trans, path, s)
-        });
-    }
-
-    fn call_return_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        _block: mir::BasicBlock,
-        return_places: CallReturnPlaces<'_, 'tcx>,
-    ) {
-        return_places.for_each(|place| {
-            // when a call returns successfully, that means we need to set
-            // the bits for that dest_place to 1 (initialized).
-            on_lookup_result_bits(
-                self.tcx,
-                self.body,
-                self.move_data(),
-                self.move_data().rev_lookup.find(place.as_ref()),
-                |mpi| {
-                    trans.gen(mpi);
-                },
-            );
-        });
-    }
-
-    fn switch_int_edge_effects<G: GenKill<Self::Idx>>(
-        &mut self,
-        block: mir::BasicBlock,
-        discr: &mir::Operand<'tcx>,
-        edge_effects: &mut impl SwitchIntEdgeEffects<G>,
-    ) {
-        if !self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration {
-            return;
-        }
-
-        let enum_ = discr.place().and_then(|discr| {
-            switch_on_enum_discriminant(self.tcx, &self.body, &self.body[block], discr)
-        });
-
-        let Some((enum_place, enum_def)) = enum_ else {
-            return;
-        };
-
-        let mut discriminants = enum_def.discriminants(self.tcx);
-        edge_effects.apply(|trans, edge| {
-            let Some(value) = edge.value else {
-                return;
-            };
-
-            // MIR building adds discriminants to the `values` array in the same order as they
-            // are yielded by `AdtDef::discriminants`. We rely on this to match each
-            // discriminant in `values` to its corresponding variant in linear time.
-            let (variant, _) = discriminants
-                .find(|&(_, discr)| discr.val == value)
-                .expect("Order of `AdtDef::discriminants` differed from `SwitchInt::values`");
-
-            // Kill all move paths that correspond to variants we know to be inactive along this
-            // particular outgoing edge of a `SwitchInt`.
-            drop_flag_effects::on_all_inactive_variants(
-                self.tcx,
-                self.body,
-                self.move_data(),
-                enum_place,
-                variant,
-                |mpi| trans.kill(mpi),
-            );
-        });
-    }
-}
-
-impl<'tcx> AnalysisDomain<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> {
-    type Domain = ChunkedBitSet<MovePathIndex>;
-
-    const NAME: &'static str = "maybe_uninit";
-
-    fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
-        // bottom = initialized (start_block_effect counters this at outset)
-        ChunkedBitSet::new_empty(self.move_data().move_paths.len())
-    }
-
-    // sets on_entry bits for Arg places
-    fn initialize_start_block(&self, _: &mir::Body<'tcx>, state: &mut Self::Domain) {
-        // set all bits to 1 (uninit) before gathering counter-evidence
-        state.insert_all();
-
-        drop_flag_effects_for_function_entry(self.tcx, self.body, self.mdpe, |path, s| {
-            assert!(s == DropFlagState::Present);
-            state.remove(path);
-        });
-    }
-}
-
-impl<'tcx> GenKillAnalysis<'tcx> for MaybeUninitializedPlaces<'_, 'tcx> {
-    type Idx = MovePathIndex;
-
-    fn statement_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        _statement: &mir::Statement<'tcx>,
-        location: Location,
-    ) {
-        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
-            Self::update_bits(trans, path, s)
-        });
-
-        // Unlike in `MaybeInitializedPlaces` above, we don't need to change the state when a
-        // mutable borrow occurs. Places cannot become uninitialized through a mutable reference.
-    }
-
-    fn terminator_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        _terminator: &mir::Terminator<'tcx>,
-        location: Location,
-    ) {
-        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
-            Self::update_bits(trans, path, s)
-        });
-    }
-
-    fn call_return_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        _block: mir::BasicBlock,
-        return_places: CallReturnPlaces<'_, 'tcx>,
-    ) {
-        return_places.for_each(|place| {
-            // when a call returns successfully, that means we need to set
-            // the bits for that dest_place to 0 (initialized).
-            on_lookup_result_bits(
-                self.tcx,
-                self.body,
-                self.move_data(),
-                self.move_data().rev_lookup.find(place.as_ref()),
-                |mpi| {
-                    trans.kill(mpi);
-                },
-            );
-        });
-    }
-
-    fn switch_int_edge_effects<G: GenKill<Self::Idx>>(
-        &mut self,
-        block: mir::BasicBlock,
-        discr: &mir::Operand<'tcx>,
-        edge_effects: &mut impl SwitchIntEdgeEffects<G>,
-    ) {
-        if !self.tcx.sess.opts.unstable_opts.precise_enum_drop_elaboration {
-            return;
-        }
-
-        if !self.mark_inactive_variants_as_uninit {
-            return;
-        }
-
-        let enum_ = discr.place().and_then(|discr| {
-            switch_on_enum_discriminant(self.tcx, &self.body, &self.body[block], discr)
-        });
-
-        let Some((enum_place, enum_def)) = enum_ else {
-            return;
-        };
-
-        let mut discriminants = enum_def.discriminants(self.tcx);
-        edge_effects.apply(|trans, edge| {
-            let Some(value) = edge.value else {
-                return;
-            };
-
-            // MIR building adds discriminants to the `values` array in the same order as they
-            // are yielded by `AdtDef::discriminants`. We rely on this to match each
-            // discriminant in `values` to its corresponding variant in linear time.
-            let (variant, _) = discriminants
-                .find(|&(_, discr)| discr.val == value)
-                .expect("Order of `AdtDef::discriminants` differed from `SwitchInt::values`");
-
-            // Mark all move paths that correspond to variants other than this one as maybe
-            // uninitialized (in reality, they are *definitely* uninitialized).
-            drop_flag_effects::on_all_inactive_variants(
-                self.tcx,
-                self.body,
-                self.move_data(),
-                enum_place,
-                variant,
-                |mpi| trans.gen(mpi),
-            );
-        });
-    }
-}
-
-impl<'a, 'tcx> AnalysisDomain<'tcx> for DefinitelyInitializedPlaces<'a, 'tcx> {
-    /// Use set intersection as the join operator.
-    type Domain = lattice::Dual<BitSet<MovePathIndex>>;
-
-    const NAME: &'static str = "definite_init";
-
-    fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
-        // bottom = initialized (start_block_effect counters this at outset)
-        lattice::Dual(BitSet::new_filled(self.move_data().move_paths.len()))
-    }
-
-    // sets on_entry bits for Arg places
-    fn initialize_start_block(&self, _: &mir::Body<'tcx>, state: &mut Self::Domain) {
-        state.0.clear();
-
-        drop_flag_effects_for_function_entry(self.tcx, self.body, self.mdpe, |path, s| {
-            assert!(s == DropFlagState::Present);
-            state.0.insert(path);
-        });
-    }
-}
-
-impl<'tcx> GenKillAnalysis<'tcx> for DefinitelyInitializedPlaces<'_, 'tcx> {
-    type Idx = MovePathIndex;
-
-    fn statement_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        _statement: &mir::Statement<'tcx>,
-        location: Location,
-    ) {
-        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
-            Self::update_bits(trans, path, s)
-        })
-    }
-
-    fn terminator_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        _terminator: &mir::Terminator<'tcx>,
-        location: Location,
-    ) {
-        drop_flag_effects_for_location(self.tcx, self.body, self.mdpe, location, |path, s| {
-            Self::update_bits(trans, path, s)
-        })
-    }
-
-    fn call_return_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        _block: mir::BasicBlock,
-        return_places: CallReturnPlaces<'_, 'tcx>,
-    ) {
-        return_places.for_each(|place| {
-            // when a call returns successfully, that means we need to set
-            // the bits for that dest_place to 1 (initialized).
-            on_lookup_result_bits(
-                self.tcx,
-                self.body,
-                self.move_data(),
-                self.move_data().rev_lookup.find(place.as_ref()),
-                |mpi| {
-                    trans.gen(mpi);
-                },
-            );
-        });
-    }
-}
-
-impl<'tcx> AnalysisDomain<'tcx> for EverInitializedPlaces<'_, 'tcx> {
-    type Domain = ChunkedBitSet<InitIndex>;
-
-    const NAME: &'static str = "ever_init";
-
-    fn bottom_value(&self, _: &mir::Body<'tcx>) -> Self::Domain {
-        // bottom = no initialized variables by default
-        ChunkedBitSet::new_empty(self.move_data().inits.len())
-    }
-
-    fn initialize_start_block(&self, body: &mir::Body<'tcx>, state: &mut Self::Domain) {
-        for arg_init in 0..body.arg_count {
-            state.insert(InitIndex::new(arg_init));
-        }
-    }
-}
-
-impl<'tcx> GenKillAnalysis<'tcx> for EverInitializedPlaces<'_, 'tcx> {
-    type Idx = InitIndex;
-
-    #[instrument(skip(self, trans), level = "debug")]
-    fn statement_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        stmt: &mir::Statement<'tcx>,
-        location: Location,
-    ) {
-        let move_data = self.move_data();
-        let init_path_map = &move_data.init_path_map;
-        let init_loc_map = &move_data.init_loc_map;
-        let rev_lookup = &move_data.rev_lookup;
-
-        debug!("initializes move_indexes {:?}", &init_loc_map[location]);
-        trans.gen_all(init_loc_map[location].iter().copied());
-
-        if let mir::StatementKind::StorageDead(local) = stmt.kind {
-            // End inits for StorageDead, so that an immutable variable can
-            // be reinitialized on the next iteration of the loop.
-            let move_path_index = rev_lookup.find_local(local);
-            debug!("clears the ever initialized status of {:?}", init_path_map[move_path_index]);
-            trans.kill_all(init_path_map[move_path_index].iter().copied());
-        }
-    }
-
-    #[instrument(skip(self, trans, _terminator), level = "debug")]
-    fn terminator_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        _terminator: &mir::Terminator<'tcx>,
-        location: Location,
-    ) {
-        let (body, move_data) = (self.body, self.move_data());
-        let term = body[location.block].terminator();
-        let init_loc_map = &move_data.init_loc_map;
-        debug!(?term);
-        debug!("initializes move_indexes {:?}", init_loc_map[location]);
-        trans.gen_all(
-            init_loc_map[location]
-                .iter()
-                .filter(|init_index| {
-                    move_data.inits[**init_index].kind != InitKind::NonPanicPathOnly
-                })
-                .copied(),
-        );
-    }
-
-    fn call_return_effect(
-        &mut self,
-        trans: &mut impl GenKill<Self::Idx>,
-        block: mir::BasicBlock,
-        _return_places: CallReturnPlaces<'_, 'tcx>,
-    ) {
-        let move_data = self.move_data();
-        let init_loc_map = &move_data.init_loc_map;
-
-        let call_loc = self.body.terminator_loc(block);
-        for init_index in &init_loc_map[call_loc] {
-            trans.gen(*init_index);
-        }
-    }
-}
-
-/// Inspect a `SwitchInt`-terminated basic block to see if the condition of that `SwitchInt` is
-/// an enum discriminant.
-///
-/// We expect such blocks to have a call to `discriminant` as their last statement like so:
-///
-/// ```text
-/// ...
-/// _42 = discriminant(_1)
-/// SwitchInt(_42, ..)
-/// ```
-///
-/// If the basic block matches this pattern, this function returns the place corresponding to the
-/// enum (`_1` in the example above) as well as the `AdtDef` of that enum.
-fn switch_on_enum_discriminant<'mir, 'tcx>(
-    tcx: TyCtxt<'tcx>,
-    body: &'mir mir::Body<'tcx>,
-    block: &'mir mir::BasicBlockData<'tcx>,
-    switch_on: mir::Place<'tcx>,
-) -> Option<(mir::Place<'tcx>, ty::AdtDef<'tcx>)> {
-    for statement in block.statements.iter().rev() {
-        match &statement.kind {
-            mir::StatementKind::Assign(box (lhs, mir::Rvalue::Discriminant(discriminated)))
-                if *lhs == switch_on =>
-            {
-                match discriminated.ty(body, tcx).ty.kind() {
-                    ty::Adt(def, _) => return Some((*discriminated, *def)),
-
-                    // `Rvalue::Discriminant` is also used to get the active yield point for a
-                    // generator, but we do not need edge-specific effects in that case. This may
-                    // change in the future.
-                    ty::Generator(..) => return None,
-
-                    t => bug!("`discriminant` called on unexpected type {:?}", t),
-                }
-            }
-            mir::StatementKind::Coverage(_) => continue,
-            _ => return None,
-        }
-    }
-    None
-}

compiler/rustc_mir_dataflow/src/impls/storage_liveness.rs

@@ -1,10 +1,12 @@
-pub use super::*;
+use rustc_index::bit_set::BitSet;
-
-use crate::{CallReturnPlaces, GenKill, ResultsClonedCursor};
 use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
+
 use std::borrow::Cow;
 
+use super::MaybeBorrowedLocals;
+use crate::{CallReturnPlaces, GenKill, ResultsClonedCursor};
+
 #[derive(Clone)]
 pub struct MaybeStorageLive<'a> {
     always_live_locals: Cow<'a, BitSet<Local>>,
@@ -27,12 +29,12 @@ impl<'tcx, 'a> crate::AnalysisDomain<'tcx> for MaybeStorageLive<'a> {
 
     const NAME: &'static str = "maybe_storage_live";
 
-    fn bottom_value(&self, body: &mir::Body<'tcx>) -> Self::Domain {
+    fn bottom_value(&self, body: &Body<'tcx>) -> Self::Domain {
         // bottom = dead
         BitSet::new_empty(body.local_decls.len())
     }
 
-    fn initialize_start_block(&self, body: &mir::Body<'tcx>, on_entry: &mut Self::Domain) {
+    fn initialize_start_block(&self, body: &Body<'tcx>, on_entry: &mut Self::Domain) {
         assert_eq!(body.local_decls.len(), self.always_live_locals.domain_size());
         for local in self.always_live_locals.iter() {
             on_entry.insert(local);
@@ -50,7 +52,7 @@ impl<'tcx, 'a> crate::GenKillAnalysis<'tcx> for MaybeStorageLive<'a> {
     fn statement_effect(
         &mut self,
         trans: &mut impl GenKill<Self::Idx>,
-        stmt: &mir::Statement<'tcx>,
+        stmt: &Statement<'tcx>,
         _: Location,
     ) {
         match stmt.kind {
@@ -63,7 +65,7 @@ impl<'tcx, 'a> crate::GenKillAnalysis<'tcx> for MaybeStorageLive<'a> {
     fn terminator_effect(
         &mut self,
         _trans: &mut impl GenKill<Self::Idx>,
-        _: &mir::Terminator<'tcx>,
+        _: &Terminator<'tcx>,
         _: Location,
     ) {
         // Terminators have no effect
@@ -95,12 +97,12 @@ impl<'tcx> crate::AnalysisDomain<'tcx> for MaybeStorageDead {
 
     const NAME: &'static str = "maybe_storage_dead";
 
-    fn bottom_value(&self, body: &mir::Body<'tcx>) -> Self::Domain {
+    fn bottom_value(&self, body: &Body<'tcx>) -> Self::Domain {
         // bottom = live
         BitSet::new_empty(body.local_decls.len())
     }
 
-    fn initialize_start_block(&self, body: &mir::Body<'tcx>, on_entry: &mut Self::Domain) {
+    fn initialize_start_block(&self, body: &Body<'tcx>, on_entry: &mut Self::Domain) {
         assert_eq!(body.local_decls.len(), self.always_live_locals.domain_size());
         // Do not iterate on return place and args, as they are trivially always live.
         for local in body.vars_and_temps_iter() {
@@ -117,7 +119,7 @@ impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeStorageDead {
     fn statement_effect(
         &mut self,
         trans: &mut impl GenKill<Self::Idx>,
-        stmt: &mir::Statement<'tcx>,
+        stmt: &Statement<'tcx>,
         _: Location,
     ) {
         match stmt.kind {
@@ -130,7 +132,7 @@ impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeStorageDead {
     fn terminator_effect(
         &mut self,
         _trans: &mut impl GenKill<Self::Idx>,
-        _: &mir::Terminator<'tcx>,
+        _: &Terminator<'tcx>,
         _: Location,
     ) {
         // Terminators have no effect
@@ -172,12 +174,12 @@ impl<'tcx> crate::AnalysisDomain<'tcx> for MaybeRequiresStorage<'_, '_, 'tcx> {
 
     const NAME: &'static str = "requires_storage";
 
-    fn bottom_value(&self, body: &mir::Body<'tcx>) -> Self::Domain {
+    fn bottom_value(&self, body: &Body<'tcx>) -> Self::Domain {
         // bottom = dead
         BitSet::new_empty(body.local_decls.len())
     }
 
-    fn initialize_start_block(&self, body: &mir::Body<'tcx>, on_entry: &mut Self::Domain) {
+    fn initialize_start_block(&self, body: &Body<'tcx>, on_entry: &mut Self::Domain) {
         // The resume argument is live on function entry (we don't care about
         // the `self` argument)
         for arg in body.args_iter().skip(1) {
@@ -192,7 +194,7 @@ impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeRequiresStorage<'_, '_, 'tcx> {
     fn before_statement_effect(
         &mut self,
         trans: &mut impl GenKill<Self::Idx>,
-        stmt: &mir::Statement<'tcx>,
+        stmt: &Statement<'tcx>,
         loc: Location,
     ) {
         // If a place is borrowed in a statement, it needs storage for that statement.
@@ -225,7 +227,7 @@ impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeRequiresStorage<'_, '_, 'tcx> {
     fn statement_effect(
         &mut self,
         trans: &mut impl GenKill<Self::Idx>,
-        _: &mir::Statement<'tcx>,
+        _: &Statement<'tcx>,
         loc: Location,
     ) {
         // If we move from a place then it only stops needing storage *after*
@@ -236,7 +238,7 @@ impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeRequiresStorage<'_, '_, 'tcx> {
     fn before_terminator_effect(
         &mut self,
         trans: &mut impl GenKill<Self::Idx>,
-        terminator: &mir::Terminator<'tcx>,
+        terminator: &Terminator<'tcx>,
         loc: Location,
     ) {
         // If a place is borrowed in a terminator, it needs storage for that terminator.
@@ -289,7 +291,7 @@ impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeRequiresStorage<'_, '_, 'tcx> {
     fn terminator_effect(
         &mut self,
         trans: &mut impl GenKill<Self::Idx>,
-        terminator: &mir::Terminator<'tcx>,
+        terminator: &Terminator<'tcx>,
         loc: Location,
     ) {
         match terminator.kind {
@@ -338,7 +340,7 @@ impl<'tcx> crate::GenKillAnalysis<'tcx> for MaybeRequiresStorage<'_, '_, 'tcx> {
         &mut self,
         trans: &mut impl GenKill<Self::Idx>,
         _resume_block: BasicBlock,
-        resume_place: mir::Place<'tcx>,
+        resume_place: Place<'tcx>,
     ) {
         trans.gen(resume_place.local);
     }