Auto merge of #118230 - nnethercote:streamline-dataflow-cursors, r=<try>

Streamline MIR dataflow cursors

r? `@ghost`

Author: bors

compiler/rustc_borrowck/src/dataflow.rs

@@ -121,24 +121,24 @@ rustc_index::newtype_index! {
 /// `BorrowIndex`, and maps each such index to a `BorrowData`
 /// describing the borrow. These indexes are used for representing the
 /// borrows in compact bitvectors.
-pub struct Borrows<'a, 'tcx> {
+pub struct Borrows<'mir, 'tcx> {
     tcx: TyCtxt<'tcx>,
-    body: &'a Body<'tcx>,
+    body: &'mir Body<'tcx>,
 
-    borrow_set: &'a BorrowSet<'tcx>,
+    borrow_set: &'mir BorrowSet<'tcx>,
     borrows_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
 }
 
-struct OutOfScopePrecomputer<'a, 'tcx> {
+struct OutOfScopePrecomputer<'mir, 'tcx> {
     visited: BitSet<mir::BasicBlock>,
     visit_stack: Vec<mir::BasicBlock>,
-    body: &'a Body<'tcx>,
-    regioncx: &'a RegionInferenceContext<'tcx>,
+    body: &'mir Body<'tcx>,
+    regioncx: &'mir RegionInferenceContext<'tcx>,
     borrows_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
 }
 
-impl<'a, 'tcx> OutOfScopePrecomputer<'a, 'tcx> {
-    fn new(body: &'a Body<'tcx>, regioncx: &'a RegionInferenceContext<'tcx>) -> Self {
+impl<'mir, 'tcx> OutOfScopePrecomputer<'mir, 'tcx> {
+    fn new(body: &'mir Body<'tcx>, regioncx: &'mir RegionInferenceContext<'tcx>) -> Self {
         OutOfScopePrecomputer {
             visited: BitSet::new_empty(body.basic_blocks.len()),
             visit_stack: vec![],
@@ -241,17 +241,17 @@ pub fn calculate_borrows_out_of_scope_at_location<'tcx>(
     prec.borrows_out_of_scope_at_location
 }
 
-struct PoloniusOutOfScopePrecomputer<'a, 'tcx> {
+struct PoloniusOutOfScopePrecomputer<'mir, 'tcx> {
     visited: BitSet<mir::BasicBlock>,
     visit_stack: Vec<mir::BasicBlock>,
-    body: &'a Body<'tcx>,
-    regioncx: &'a RegionInferenceContext<'tcx>,
+    body: &'mir Body<'tcx>,
+    regioncx: &'mir RegionInferenceContext<'tcx>,
 
     loans_out_of_scope_at_location: FxIndexMap<Location, Vec<BorrowIndex>>,
 }
 
-impl<'a, 'tcx> PoloniusOutOfScopePrecomputer<'a, 'tcx> {
-    fn new(body: &'a Body<'tcx>, regioncx: &'a RegionInferenceContext<'tcx>) -> Self {
+impl<'mir, 'tcx> PoloniusOutOfScopePrecomputer<'mir, 'tcx> {
+    fn new(body: &'mir Body<'tcx>, regioncx: &'mir RegionInferenceContext<'tcx>) -> Self {
         Self {
             visited: BitSet::new_empty(body.basic_blocks.len()),
             visit_stack: vec![],
@@ -404,12 +404,12 @@ impl<'tcx> PoloniusOutOfScopePrecomputer<'_, 'tcx> {
     }
 }
 
-impl<'a, 'tcx> Borrows<'a, 'tcx> {
+impl<'mir, 'tcx> Borrows<'mir, 'tcx> {
     pub fn new(
         tcx: TyCtxt<'tcx>,
-        body: &'a Body<'tcx>,
-        regioncx: &'a RegionInferenceContext<'tcx>,
-        borrow_set: &'a BorrowSet<'tcx>,
+        body: &'mir Body<'tcx>,
+        regioncx: &'mir RegionInferenceContext<'tcx>,
+        borrow_set: &'mir BorrowSet<'tcx>,
     ) -> Self {
         let mut borrows_out_of_scope_at_location =
             calculate_borrows_out_of_scope_at_location(body, regioncx, borrow_set);

compiler/rustc_mir_dataflow/src/drop_flag_effects.rs

@@ -3,8 +3,7 @@ use rustc_middle::mir::{self, Body, Location, Terminator, TerminatorKind};
 use rustc_middle::ty::TyCtxt;
 use rustc_target::abi::VariantIdx;
 
-use super::indexes::MovePathIndex;
-use super::move_paths::{InitKind, LookupResult, MoveData};
+use super::move_paths::{InitKind, LookupResult, MoveData, MovePathIndex};
 use super::MoveDataParamEnv;
 
 pub fn move_path_children_matching<'tcx, F>(
@@ -129,7 +128,7 @@ pub fn drop_flag_effects_for_location<'tcx, F>(
     for_location_inits(tcx, body, move_data, loc, |mpi| callback(mpi, DropFlagState::Present));
 }
 
-pub fn for_location_inits<'tcx, F>(
+fn for_location_inits<'tcx, F>(
     tcx: TyCtxt<'tcx>,
     body: &Body<'tcx>,
     move_data: &MoveData<'tcx>,

compiler/rustc_mir_dataflow/src/framework/cursor.rs

@@ -1,76 +1,27 @@
 //! Random access inspection of the results of a dataflow analysis.
 
-use crate::{framework::BitSetExt, CloneAnalysis};
+use crate::framework::BitSetExt;
 
-use std::borrow::{Borrow, BorrowMut};
 use std::cmp::Ordering;
 
 #[cfg(debug_assertions)]
 use rustc_index::bit_set::BitSet;
 use rustc_middle::mir::{self, BasicBlock, Location};
 
-use super::{Analysis, Direction, Effect, EffectIndex, EntrySets, Results, ResultsCloned};
-
-// `AnalysisResults` is needed as an impl such as the following has an unconstrained type
-// parameter:
-// ```
-// impl<'tcx, A, E, R> ResultsCursor<'_, 'tcx, A, R>
-// where
-//     A: Analysis<'tcx>,
-//     E: Borrow<EntrySets<'tcx, A>>,
-//     R: Results<'tcx, A, E>,
-// {}
-// ```
-
-/// A type representing the analysis results consumed by a `ResultsCursor`.
-pub trait AnalysisResults<'tcx, A>: BorrowMut<Results<'tcx, A, Self::EntrySets>>
-where
-    A: Analysis<'tcx>,
-{
-    /// The type containing the entry sets for this `Results` type.
-    ///
-    /// Should be either `EntrySets<'tcx, A>` or `&EntrySets<'tcx, A>`.
-    type EntrySets: Borrow<EntrySets<'tcx, A>>;
-}
-impl<'tcx, A, E> AnalysisResults<'tcx, A> for Results<'tcx, A, E>
-where
-    A: Analysis<'tcx>,
-    E: Borrow<EntrySets<'tcx, A>>,
-{
-    type EntrySets = E;
-}
-impl<'a, 'tcx, A, E> AnalysisResults<'tcx, A> for &'a mut Results<'tcx, A, E>
-where
-    A: Analysis<'tcx>,
-    E: Borrow<EntrySets<'tcx, A>>,
-{
-    type EntrySets = E;
-}
-
-/// A `ResultsCursor` that borrows the underlying `Results`.
-pub type ResultsRefCursor<'res, 'mir, 'tcx, A> =
-    ResultsCursor<'mir, 'tcx, A, &'res mut Results<'tcx, A>>;
-
-/// A `ResultsCursor` which uses a cloned `Analysis` while borrowing the underlying `Results`. This
-/// allows multiple cursors over the same `Results`.
-pub type ResultsClonedCursor<'res, 'mir, 'tcx, A> =
-    ResultsCursor<'mir, 'tcx, A, ResultsCloned<'res, 'tcx, A>>;
+use super::{Analysis, Direction, Effect, EffectIndex, Results};
 
 /// Allows random access inspection of the results of a dataflow analysis.
 ///
 /// This cursor only has linear performance within a basic block when its statements are visited in
 /// the same order as the `DIRECTION` of the analysis. In the worst case—when statements are
 /// visited in *reverse* order—performance will be quadratic in the number of statements in the
 /// block. The order in which basic blocks are inspected has no impact on performance.
-///
-/// A `ResultsCursor` can either own (the default) or borrow the dataflow results it inspects. The
-/// type of ownership is determined by `R` (see `ResultsRefCursor` above).
-pub struct ResultsCursor<'mir, 'tcx, A, R = Results<'tcx, A>>
+pub struct ResultsCursor<'mir, 'tcx, A>
 where
     A: Analysis<'tcx>,
 {
     body: &'mir mir::Body<'tcx>,
-    results: R,
+    results: Results<'tcx, A>,
     state: A::Domain,
 
     pos: CursorPosition,
@@ -84,7 +35,7 @@ where
     reachable_blocks: BitSet<BasicBlock>,
 }
 
-impl<'mir, 'tcx, A, R> ResultsCursor<'mir, 'tcx, A, R>
+impl<'mir, 'tcx, A> ResultsCursor<'mir, 'tcx, A>
 where
     A: Analysis<'tcx>,
 {
@@ -99,30 +50,13 @@ where
     }
 
     /// Unwraps this cursor, returning the underlying `Results`.
-    pub fn into_results(self) -> R {
+    pub fn into_results(self) -> Results<'tcx, A> {
         self.results
     }
-}
 
-impl<'res, 'mir, 'tcx, A> ResultsCursor<'mir, 'tcx, A, ResultsCloned<'res, 'tcx, A>>
-where
-    A: Analysis<'tcx> + CloneAnalysis,
-{
-    /// Creates a new cursor over the same `Results`. Note that the cursor's position is *not*
-    /// copied.
-    pub fn new_cursor(&self) -> Self {
-        Self::new(self.body, self.results.reclone_analysis())
-    }
-}
-
-impl<'mir, 'tcx, A, R> ResultsCursor<'mir, 'tcx, A, R>
-where
-    A: Analysis<'tcx>,
-    R: AnalysisResults<'tcx, A>,
-{
     /// Returns a new cursor that can inspect `results`.
-    pub fn new(body: &'mir mir::Body<'tcx>, results: R) -> Self {
-        let bottom_value = results.borrow().analysis.bottom_value(body);
+    pub fn new(body: &'mir mir::Body<'tcx>, results: Results<'tcx, A>) -> Self {
+        let bottom_value = results.analysis.bottom_value(body);
         ResultsCursor {
             body,
             results,
@@ -147,28 +81,23 @@ where
     }
 
     /// Returns the underlying `Results`.
-    pub fn results(&mut self) -> &Results<'tcx, A, R::EntrySets> {
-        self.results.borrow()
+    pub fn results(&self) -> &Results<'tcx, A> {
+        &self.results
     }
 
     /// Returns the underlying `Results`.
-    pub fn mut_results(&mut self) -> &mut Results<'tcx, A, R::EntrySets> {
-        self.results.borrow_mut()
+    pub fn mut_results(&mut self) -> &mut Results<'tcx, A> {
+        &mut self.results
     }
 
     /// Returns the `Analysis` used to generate the underlying `Results`.
     pub fn analysis(&self) -> &A {
-        &self.results.borrow().analysis
+        &self.results.analysis
     }
 
     /// Returns the `Analysis` used to generate the underlying `Results`.
     pub fn mut_analysis(&mut self) -> &mut A {
-        &mut self.results.borrow_mut().analysis
-    }
-
-    /// Returns both the dataflow state at the current location and the `Analysis`.
-    pub fn get_with_analysis(&mut self) -> (&A::Domain, &mut A) {
-        (&self.state, &mut self.results.borrow_mut().analysis)
+        &mut self.results.analysis
     }
 
     /// Resets the cursor to hold the entry set for the given basic block.
@@ -180,7 +109,7 @@ where
         #[cfg(debug_assertions)]
         assert!(self.reachable_blocks.contains(block));
 
-        self.state.clone_from(self.results.borrow().entry_set_for_block(block));
+        self.state.clone_from(self.results.entry_set_for_block(block));
         self.pos = CursorPosition::block_entry(block);
         self.state_needs_reset = false;
     }
@@ -269,11 +198,10 @@ where
             )
         };
 
-        let analysis = &mut self.results.borrow_mut().analysis;
         let target_effect_index = effect.at_index(target.statement_index);
 
         A::Direction::apply_effects_in_range(
-            analysis,
+            &mut self.results.analysis,
             &mut self.state,
             target.block,
             block_data,
@@ -289,12 +217,12 @@ where
     /// This can be used, e.g., to apply the call return effect directly to the cursor without
     /// creating an extra copy of the dataflow state.
     pub fn apply_custom_effect(&mut self, f: impl FnOnce(&mut A, &mut A::Domain)) {
-        f(&mut self.results.borrow_mut().analysis, &mut self.state);
+        f(&mut self.results.analysis, &mut self.state);
         self.state_needs_reset = true;
     }
 }
 
-impl<'mir, 'tcx, A, R> ResultsCursor<'mir, 'tcx, A, R>
+impl<'mir, 'tcx, A> ResultsCursor<'mir, 'tcx, A>
 where
     A: crate::GenKillAnalysis<'tcx>,
     A::Domain: BitSetExt<A::Idx>,

compiler/rustc_mir_dataflow/src/framework/direction.rs

@@ -287,12 +287,12 @@ impl Direction for Backward {
     }
 }
 
-struct BackwardSwitchIntEdgeEffectsApplier<'a, 'tcx, D, F> {
-    body: &'a mir::Body<'tcx>,
+struct BackwardSwitchIntEdgeEffectsApplier<'mir, 'tcx, D, F> {
+    body: &'mir mir::Body<'tcx>,
     pred: BasicBlock,
-    exit_state: &'a mut D,
+    exit_state: &'mir mut D,
     bb: BasicBlock,
-    propagate: &'a mut F,
+    propagate: &'mir mut F,
     effects_applied: bool,
 }
 
@@ -523,9 +523,9 @@ impl Direction for Forward {
     }
 }
 
-struct ForwardSwitchIntEdgeEffectsApplier<'a, D, F> {
-    exit_state: &'a mut D,
-    targets: &'a SwitchTargets,
+struct ForwardSwitchIntEdgeEffectsApplier<'mir, D, F> {
+    exit_state: &'mir mut D,
+    targets: &'mir SwitchTargets,
     propagate: F,
 
     effects_applied: bool,