From c68d710d525ce4ef56f1de4ba339e7c7b39ddd77 Mon Sep 17 00:00:00 2001 From: Dylan MacKenzie Date: Sun, 22 Mar 2020 12:09:40 -0700 Subject: [PATCH] Support backward dataflow analyses --- src/librustc_mir/borrow_check/mod.rs | 6 +- .../borrow_check/type_check/liveness/trace.rs | 4 +- src/librustc_mir/dataflow/framework/cursor.rs | 304 ++++------ .../dataflow/framework/direction.rs | 570 ++++++++++++++++++ src/librustc_mir/dataflow/framework/engine.rs | 338 ++++------- .../dataflow/framework/graphviz.rs | 135 +++-- src/librustc_mir/dataflow/framework/mod.rs | 122 ++-- src/librustc_mir/dataflow/framework/tests.rs | 163 +++-- .../dataflow/framework/visitor.rs | 73 +-- .../dataflow/impls/storage_liveness.rs | 4 +- src/librustc_mir/dataflow/mod.rs | 5 +- src/librustc_mir/lib.rs | 4 +- .../transform/check_consts/validation.rs | 6 +- src/librustc_mir/transform/elaborate_drops.rs | 6 +- src/librustc_mir/transform/generator.rs | 13 +- src/librustc_mir/transform/rustc_peek.rs | 2 +- 16 files changed, 1094 insertions(+), 661 deletions(-) create mode 100644 src/librustc_mir/dataflow/framework/direction.rs diff --git a/src/librustc_mir/borrow_check/mod.rs b/src/librustc_mir/borrow_check/mod.rs index b95a1043d92..7d8a2b540a9 100644 --- a/src/librustc_mir/borrow_check/mod.rs +++ b/src/librustc_mir/borrow_check/mod.rs @@ -518,7 +518,7 @@ fn do_mir_borrowck<'a, 'tcx>( impl<'cx, 'tcx> dataflow::ResultsVisitor<'cx, 'tcx> for MirBorrowckCtxt<'cx, 'tcx> { type FlowState = Flows<'cx, 'tcx>; - fn visit_statement( + fn visit_statement_before_primary_effect( &mut self, flow_state: &Flows<'cx, 'tcx>, stmt: &'cx Statement<'tcx>, @@ -607,7 +607,7 @@ fn visit_statement( } } - fn visit_terminator( + fn visit_terminator_before_primary_effect( &mut self, flow_state: &Flows<'cx, 'tcx>, term: &'cx Terminator<'tcx>, @@ -701,7 +701,7 @@ fn visit_terminator( } } - fn visit_terminator_exit( + fn visit_terminator_after_primary_effect( &mut self, flow_state: &Flows<'cx, 'tcx>, term: &'cx Terminator<'tcx>, diff --git a/src/librustc_mir/borrow_check/type_check/liveness/trace.rs b/src/librustc_mir/borrow_check/type_check/liveness/trace.rs index ec52a08c7b2..41c77cf21a7 100644 --- a/src/librustc_mir/borrow_check/type_check/liveness/trace.rs +++ b/src/librustc_mir/borrow_check/type_check/liveness/trace.rs @@ -408,7 +408,7 @@ fn initialized_at_curr_loc(&self, mpi: MovePathIndex) -> bool { /// DROP of some local variable will have an effect -- note that /// drops, as they may unwind, are always terminators. fn initialized_at_terminator(&mut self, block: BasicBlock, mpi: MovePathIndex) -> bool { - self.flow_inits.seek_before(self.body.terminator_loc(block)); + self.flow_inits.seek_before_primary_effect(self.body.terminator_loc(block)); self.initialized_at_curr_loc(mpi) } @@ -418,7 +418,7 @@ fn initialized_at_terminator(&mut self, block: BasicBlock, mpi: MovePathIndex) - /// **Warning:** Does not account for the result of `Call` /// instructions. fn initialized_at_exit(&mut self, block: BasicBlock, mpi: MovePathIndex) -> bool { - self.flow_inits.seek_after(self.body.terminator_loc(block)); + self.flow_inits.seek_after_primary_effect(self.body.terminator_loc(block)); self.initialized_at_curr_loc(mpi) } diff --git a/src/librustc_mir/dataflow/framework/cursor.rs b/src/librustc_mir/dataflow/framework/cursor.rs index 39676d03740..82c8f8575c0 100644 --- a/src/librustc_mir/dataflow/framework/cursor.rs +++ b/src/librustc_mir/dataflow/framework/cursor.rs @@ -1,11 +1,12 @@ //! Random access inspection of the results of a dataflow analysis. use std::borrow::Borrow; +use std::cmp::Ordering; use rustc_index::bit_set::BitSet; -use rustc_middle::mir::{self, BasicBlock, Location, TerminatorKind}; +use rustc_middle::mir::{self, BasicBlock, Location}; -use super::{Analysis, Results}; +use super::{Analysis, Direction, Effect, EffectIndex, Results}; /// A `ResultsCursor` that borrows the underlying `Results`. pub type ResultsRefCursor<'a, 'mir, 'tcx, A> = ResultsCursor<'mir, 'tcx, A, &'a Results<'tcx, A>>; @@ -13,9 +14,9 @@ /// 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 -/// order. 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. +/// 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). @@ -29,14 +30,10 @@ pub struct ResultsCursor<'mir, 'tcx, A, R = Results<'tcx, A>> pos: CursorPosition, - /// When this flag is set, the cursor is pointing at a `Call` or `Yield` terminator whose call - /// return or resume effect has been applied to `state`. + /// Indicates that `state` has been modified with a custom effect. /// - /// This flag helps to ensure that multiple calls to `seek_after_assume_success` with the - /// same target will result in exactly one invocation of `apply_call_return_effect`. It is - /// sufficient to clear this only in `seek_to_block_start`, since seeking away from a - /// terminator will always require a cursor reset. - success_effect_applied: bool, + /// When this flag is set, we need to reset to an entry set before doing a seek. + state_needs_reset: bool, } impl<'mir, 'tcx, A, R> ResultsCursor<'mir, 'tcx, A, R> @@ -44,17 +41,21 @@ impl<'mir, 'tcx, A, R> ResultsCursor<'mir, 'tcx, A, R> A: Analysis<'tcx>, R: Borrow>, { - /// Returns a new cursor for `results` that points to the start of the `START_BLOCK`. + /// Returns a new cursor for `results` that points to the entry of the `START_BLOCK`. pub fn new(body: &'mir mir::Body<'tcx>, results: R) -> Self { ResultsCursor { body, - pos: CursorPosition::BlockStart(mir::START_BLOCK), - state: results.borrow().entry_sets[mir::START_BLOCK].clone(), - success_effect_applied: false, + pos: CursorPosition::block_entry(mir::START_BLOCK), + state: results.borrow().entry_set_for_block(mir::START_BLOCK).clone(), + state_needs_reset: false, results, } } + pub fn body(&self) -> &'mir mir::Body<'tcx> { + self.body + } + /// Returns the `Analysis` used to generate the underlying results. pub fn analysis(&self) -> &A { &self.results.borrow().analysis @@ -72,209 +73,134 @@ pub fn contains(&self, elem: A::Idx) -> bool { self.state.contains(elem) } - /// Resets the cursor to the start of the given basic block. - pub fn seek_to_block_start(&mut self, block: BasicBlock) { - self.state.overwrite(&self.results.borrow().entry_sets[block]); - self.pos = CursorPosition::BlockStart(block); - self.success_effect_applied = false; - } - - /// Advances the cursor to hold all effects up to and including to the "before" effect of the - /// statement (or terminator) at the given location. + /// Resets the cursor to hold the dataflow state for the given basic block at fixpoint. /// - /// If you wish to observe the full effect of a statement or terminator, not just the "before" - /// effect, use `seek_after` or `seek_after_assume_success`. - pub fn seek_before(&mut self, target: Location) { - assert!(target <= self.body.terminator_loc(target.block)); - self.seek_(target, false); + /// For forward dataflow analyses, this is the dataflow state prior to the first statement. + /// + /// For backward dataflow analyses, this is the dataflow state after the terminator. + pub(super) fn seek_to_block_entry(&mut self, block: BasicBlock) { + self.state.overwrite(&self.results.borrow().entry_set_for_block(block)); + self.pos = CursorPosition::block_entry(block); + self.state_needs_reset = false; } - /// Advances the cursor to hold the full effect of all statements (and possibly closing - /// terminators) up to and including the `target`. + /// Resets the cursor to hold the state at the entry to the given block. /// - /// If the `target` is a `Call` terminator, any call return effect for that terminator will - /// **not** be observed. Use `seek_after_assume_success` if you wish to observe the call - /// return effect. - pub fn seek_after(&mut self, target: Location) { - assert!(target <= self.body.terminator_loc(target.block)); - - // If we have already applied the call return effect, we are currently pointing at a `Call` - // terminator. Unconditionally reset the dataflow cursor, since there is no way to "undo" - // the call return effect. - if self.success_effect_applied { - self.seek_to_block_start(target.block); + /// For forward analyses, this is the block's state at fixpoint. + /// + /// For backward analyses, this is the state that will be propagated to its + /// predecessors (ignoring edge-specific effects). + pub fn seek_to_block_start(&mut self, block: BasicBlock) { + if A::Direction::is_forward() { + self.seek_to_block_entry(block) + } else { + self.seek_after(Location { block, statement_index: 0 }, Effect::Primary) } - - self.seek_(target, true); } - /// Advances the cursor to hold all effects up to and including of the statement (or - /// terminator) at the given location. + /// Resets the cursor to hold the state at the exit of the given block. /// - /// If the `target` is a `Call` or `Yield` terminator, any call return or resume effect for that - /// terminator will be observed. Use `seek_after` if you do **not** wish to observe the - /// "success" effect. - pub fn seek_after_assume_success(&mut self, target: Location) { - let terminator_loc = self.body.terminator_loc(target.block); - assert!(target.statement_index <= terminator_loc.statement_index); - - self.seek_(target, true); - - if target != terminator_loc || self.success_effect_applied { - return; - } - - // Apply the effect of the "success" path of the terminator. - - self.success_effect_applied = true; - let terminator = self.body.basic_blocks()[target.block].terminator(); - match &terminator.kind { - TerminatorKind::Call { destination: Some((return_place, _)), func, args, .. } => { - self.results.borrow().analysis.apply_call_return_effect( - &mut self.state, - target.block, - func, - args, - *return_place, - ); - } - TerminatorKind::Yield { resume, resume_arg, .. } => { - self.results.borrow().analysis.apply_yield_resume_effect( - &mut self.state, - *resume, - *resume_arg, - ); - } - _ => {} + /// For backward analyses, this is the block's state at fixpoint. + /// + /// For forward analyses, this is the state that will be propagated to its + /// successors (ignoring edge-specific effects). + pub fn seek_to_block_end(&mut self, block: BasicBlock) { + if A::Direction::is_backward() { + self.seek_to_block_entry(block) + } else { + self.seek_after(self.body.terminator_loc(block), Effect::Primary) } } - fn seek_(&mut self, target: Location, apply_after_effect_at_target: bool) { - use CursorPosition::*; - - match self.pos { - // Return early if we are already at the target location. - Before(curr) if curr == target && !apply_after_effect_at_target => return, - After(curr) if curr == target && apply_after_effect_at_target => return, + /// Advances the cursor to hold the dataflow state at `target` before its "primary" effect is + /// applied. + /// + /// The "before" effect at the target location *will be* applied. + pub fn seek_before_primary_effect(&mut self, target: Location) { + self.seek_after(target, Effect::Before) + } - // Otherwise, we must reset to the start of the target block if... + /// Advances the cursor to hold the dataflow state at `target` after its "primary" effect is + /// applied. + /// + /// The "before" effect at the target location will be applied as well. + pub fn seek_after_primary_effect(&mut self, target: Location) { + self.seek_after(target, Effect::Primary) + } - // we are in a different block entirely. - BlockStart(block) | Before(Location { block, .. }) | After(Location { block, .. }) - if block != target.block => - { - self.seek_to_block_start(target.block) - } + fn seek_after(&mut self, target: Location, effect: Effect) { + assert!(target <= self.body.terminator_loc(target.block)); - // we are in the same block but have advanced past the target statement. - Before(curr) | After(curr) if curr.statement_index > target.statement_index => { - self.seek_to_block_start(target.block) + // Reset to the entry of the target block if any of the following are true: + // - A custom effect has been applied to the cursor state. + // - We are in a different block than the target. + // - We are in the same block but have advanced past the target effect. + if self.state_needs_reset || self.pos.block != target.block { + self.seek_to_block_entry(target.block); + } else if let Some(curr_effect) = self.pos.curr_effect_index { + let mut ord = curr_effect.statement_index.cmp(&target.statement_index); + if A::Direction::is_backward() { + ord = ord.reverse() } - // we have already applied the entire effect of a statement but only wish to observe - // its "before" effect. - After(curr) - if curr.statement_index == target.statement_index - && !apply_after_effect_at_target => - { - self.seek_to_block_start(target.block) + match ord.then_with(|| curr_effect.effect.cmp(&effect)) { + Ordering::Equal => return, + Ordering::Greater => self.seek_to_block_entry(target.block), + Ordering::Less => {} } - - // N.B., `success_effect_applied` is checked in `seek_after`, not here. - _ => (), } - let analysis = &self.results.borrow().analysis; - let block_data = &self.body.basic_blocks()[target.block]; - // At this point, the cursor is in the same block as the target location at an earlier // statement. - debug_assert_eq!(target.block, self.pos.block()); - - // Find the first statement whose transfer function has not yet been applied. - let first_unapplied_statement = match self.pos { - BlockStart(_) => 0, - After(Location { statement_index, .. }) => statement_index + 1, - - // If we have only applied the "before" effect for the current statement, apply the - // remainder before continuing. - Before(curr) => { - if curr.statement_index == block_data.statements.len() { - let terminator = block_data.terminator(); - analysis.apply_terminator_effect(&mut self.state, terminator, curr); - } else { - let statement = &block_data.statements[curr.statement_index]; - analysis.apply_statement_effect(&mut self.state, statement, curr); - } - - // If all we needed to do was go from `Before` to `After` in the same statement, - // we are now done. - if curr.statement_index == target.statement_index { - debug_assert!(apply_after_effect_at_target); - self.pos = After(target); - return; - } - - curr.statement_index + 1 - } + debug_assert_eq!(target.block, self.pos.block); + + let block_data = &self.body[target.block]; + let next_effect = if A::Direction::is_forward() { + #[rustfmt::skip] + self.pos.curr_effect_index.map_or_else( + || Effect::Before.at_index(0), + EffectIndex::next_in_forward_order, + ) + } else { + self.pos.curr_effect_index.map_or_else( + || Effect::Before.at_index(block_data.statements.len()), + EffectIndex::next_in_backward_order, + ) }; - // We have now applied all effects prior to `first_unapplied_statement`. - - // Apply the effects of all statements before `target`. - let mut location = Location { block: target.block, statement_index: 0 }; - for statement_index in first_unapplied_statement..target.statement_index { - location.statement_index = statement_index; - let statement = &block_data.statements[statement_index]; - analysis.apply_before_statement_effect(&mut self.state, statement, location); - analysis.apply_statement_effect(&mut self.state, statement, location); - } - - // Apply the effect of the statement (or terminator) at `target`. - location.statement_index = target.statement_index; - if target.statement_index == block_data.statements.len() { - let terminator = &block_data.terminator(); - analysis.apply_before_terminator_effect(&mut self.state, terminator, location); - - if apply_after_effect_at_target { - analysis.apply_terminator_effect(&mut self.state, terminator, location); - self.pos = After(target); - } else { - self.pos = Before(target); - } - } else { - let statement = &block_data.statements[target.statement_index]; - analysis.apply_before_statement_effect(&mut self.state, statement, location); + let analysis = &self.results.borrow().analysis; + let target_effect_index = effect.at_index(target.statement_index); + + A::Direction::apply_effects_in_range( + analysis, + &mut self.state, + target.block, + block_data, + next_effect..=target_effect_index, + ); + + self.pos = + CursorPosition { block: target.block, curr_effect_index: Some(target_effect_index) }; + } - if apply_after_effect_at_target { - analysis.apply_statement_effect(&mut self.state, statement, location); - self.pos = After(target) - } else { - self.pos = Before(target); - } - } + /// Applies `f` to the cursor's internal state. + /// + /// 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(&A, &mut BitSet)) { + f(&self.results.borrow().analysis, &mut self.state); + self.state_needs_reset = true; } } #[derive(Clone, Copy, Debug)] -enum CursorPosition { - /// No effects within this block have been applied. - BlockStart(BasicBlock), - - /// Only the "before" effect of the statement (or terminator) at this location has been - /// applied (along with the effects of all previous statements). - Before(Location), - - /// The effects of all statements up to and including the one at this location have been - /// applied. - After(Location), +struct CursorPosition { + block: BasicBlock, + curr_effect_index: Option, } impl CursorPosition { - fn block(&self) -> BasicBlock { - match *self { - Self::BlockStart(block) => block, - Self::Before(loc) | Self::After(loc) => loc.block, - } + fn block_entry(block: BasicBlock) -> CursorPosition { + CursorPosition { block, curr_effect_index: None } } } diff --git a/src/librustc_mir/dataflow/framework/direction.rs b/src/librustc_mir/dataflow/framework/direction.rs new file mode 100644 index 00000000000..76f703ec913 --- /dev/null +++ b/src/librustc_mir/dataflow/framework/direction.rs @@ -0,0 +1,570 @@ +use rustc_index::bit_set::BitSet; +use rustc_middle::mir::{self, BasicBlock, Location}; +use rustc_middle::ty::{self, TyCtxt}; +use std::ops::RangeInclusive; + +use super::visitor::{ResultsVisitable, ResultsVisitor}; +use super::{Analysis, Effect, EffectIndex, GenKillAnalysis, GenKillSet}; + +pub trait Direction { + fn is_forward() -> bool; + + fn is_backward() -> bool { + !Self::is_forward() + } + + /// Applies all effects between the given `EffectIndex`s. + /// + /// `effects.start()` must precede or equal `effects.end()` in this direction. + fn apply_effects_in_range( + analysis: &A, + state: &mut BitSet, + block: BasicBlock, + block_data: &mir::BasicBlockData<'tcx>, + effects: RangeInclusive, + ) where + A: Analysis<'tcx>; + + fn apply_effects_in_block( + analysis: &A, + state: &mut BitSet, + block: BasicBlock, + block_data: &mir::BasicBlockData<'tcx>, + ) where + A: Analysis<'tcx>; + + fn gen_kill_effects_in_block( + analysis: &A, + trans: &mut GenKillSet, + block: BasicBlock, + block_data: &mir::BasicBlockData<'tcx>, + ) where + A: GenKillAnalysis<'tcx>; + + fn visit_results_in_block( + state: &mut F, + block: BasicBlock, + block_data: &'mir mir::BasicBlockData<'tcx>, + results: &R, + vis: &mut impl ResultsVisitor<'mir, 'tcx, FlowState = F>, + ) where + R: ResultsVisitable<'tcx, FlowState = F>; + + fn join_state_into_successors_of( + analysis: &A, + tcx: TyCtxt<'tcx>, + body: &mir::Body<'tcx>, + dead_unwinds: Option<&BitSet>, + exit_state: &mut BitSet, + block: (BasicBlock, &'_ mir::BasicBlockData<'tcx>), + propagate: impl FnMut(BasicBlock, &BitSet), + ) where + A: Analysis<'tcx>; +} + +/// Dataflow that runs from the exit of a block (the terminator), to its entry (the first statement). +pub struct Backward; + +impl Direction for Backward { + fn is_forward() -> bool { + false + } + + fn apply_effects_in_block( + analysis: &A, + state: &mut BitSet, + block: BasicBlock, + block_data: &mir::BasicBlockData<'tcx>, + ) where + A: Analysis<'tcx>, + { + 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); + + 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); + } + } + + fn gen_kill_effects_in_block( + analysis: &A, + trans: &mut GenKillSet, + block: BasicBlock, + block_data: &mir::BasicBlockData<'tcx>, + ) where + A: GenKillAnalysis<'tcx>, + { + let terminator = block_data.terminator(); + let location = Location { block, statement_index: block_data.statements.len() }; + analysis.before_terminator_effect(trans, terminator, location); + analysis.terminator_effect(trans, terminator, location); + + 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); + } + } + + fn apply_effects_in_range( + analysis: &A, + state: &mut BitSet, + block: BasicBlock, + block_data: &mir::BasicBlockData<'tcx>, + effects: RangeInclusive, + ) where + A: Analysis<'tcx>, + { + let (from, to) = (*effects.start(), *effects.end()); + let terminator_index = block_data.statements.len(); + + assert!(from.statement_index <= terminator_index); + assert!(!to.precedes_in_backward_order(from)); + + // Handle the statement (or terminator) at `from`. + + let next_effect = match from.effect { + // If we need to apply the terminator effect in all or in part, do so now. + _ if from.statement_index == terminator_index => { + let location = Location { block, statement_index: from.statement_index }; + let terminator = block_data.terminator(); + + if from.effect == Effect::Before { + analysis.apply_before_terminator_effect(state, terminator, location); + if to == Effect::Before.at_index(terminator_index) { + return; + } + } + + analysis.apply_terminator_effect(state, terminator, location); + if to == Effect::Primary.at_index(terminator_index) { + return; + } + + // If `from.statement_index` is `0`, we will have hit one of the earlier comparisons + // with `to`. + from.statement_index - 1 + } + + Effect::Primary => { + let location = Location { block, statement_index: from.statement_index }; + let statement = &block_data.statements[from.statement_index]; + + analysis.apply_statement_effect(state, statement, location); + if to == Effect::Primary.at_index(from.statement_index) { + return; + } + + from.statement_index - 1 + } + + Effect::Before => from.statement_index, + }; + + // Handle all statements between `first_unapplied_idx` and `to.statement_index`. + + for statement_index in (to.statement_index..next_effect).rev().map(|i| i + 1) { + let location = Location { block, statement_index }; + let statement = &block_data.statements[statement_index]; + analysis.apply_before_statement_effect(state, statement, location); + analysis.apply_statement_effect(state, statement, location); + } + + // Handle the statement at `to`. + + let location = Location { block, statement_index: to.statement_index }; + let statement = &block_data.statements[to.statement_index]; + analysis.apply_before_statement_effect(state, statement, location); + + if to.effect == Effect::Before { + return; + } + + analysis.apply_statement_effect(state, statement, location); + } + + fn visit_results_in_block( + state: &mut F, + block: BasicBlock, + block_data: &'mir mir::BasicBlockData<'tcx>, + results: &R, + vis: &mut impl ResultsVisitor<'mir, 'tcx, FlowState = F>, + ) where + R: ResultsVisitable<'tcx, FlowState = F>, + { + results.reset_to_block_entry(state, block); + + vis.visit_block_end(&state, block_data, block); + + // Terminator + let loc = Location { block, statement_index: block_data.statements.len() }; + let term = block_data.terminator(); + results.reconstruct_before_terminator_effect(state, term, loc); + vis.visit_terminator_before_primary_effect(state, term, loc); + results.reconstruct_terminator_effect(state, term, loc); + vis.visit_terminator_after_primary_effect(state, term, loc); + + for (statement_index, stmt) in block_data.statements.iter().enumerate().rev() { + let loc = Location { block, statement_index }; + results.reconstruct_before_statement_effect(state, stmt, loc); + vis.visit_statement_before_primary_effect(state, stmt, loc); + results.reconstruct_statement_effect(state, stmt, loc); + vis.visit_statement_after_primary_effect(state, stmt, loc); + } + + vis.visit_block_start(state, block_data, block); + } + + fn join_state_into_successors_of( + analysis: &A, + _tcx: TyCtxt<'tcx>, + body: &mir::Body<'tcx>, + dead_unwinds: Option<&BitSet>, + exit_state: &mut BitSet, + (bb, _bb_data): (BasicBlock, &'_ mir::BasicBlockData<'tcx>), + mut propagate: impl FnMut(BasicBlock, &BitSet), + ) where + A: Analysis<'tcx>, + { + for pred in body.predecessors()[bb].iter().copied() { + match body[pred].terminator().kind { + // Apply terminator-specific edge effects. + // + // FIXME(ecstaticmorse): Avoid cloning the exit state unconditionally. + mir::TerminatorKind::Call { + destination: Some((return_place, dest)), + ref func, + ref args, + .. + } if dest == bb => { + let mut tmp = exit_state.clone(); + analysis.apply_call_return_effect(&mut tmp, pred, func, args, return_place); + propagate(pred, &tmp); + } + + mir::TerminatorKind::Yield { resume, resume_arg, .. } if resume == bb => { + let mut tmp = exit_state.clone(); + analysis.apply_yield_resume_effect(&mut tmp, resume, resume_arg); + propagate(pred, &tmp); + } + + // Ignore dead unwinds. + mir::TerminatorKind::Call { cleanup: Some(unwind), .. } + | mir::TerminatorKind::Assert { cleanup: Some(unwind), .. } + | mir::TerminatorKind::Drop { unwind: Some(unwind), .. } + | mir::TerminatorKind::DropAndReplace { unwind: Some(unwind), .. } + | mir::TerminatorKind::FalseUnwind { unwind: Some(unwind), .. } + if unwind == bb => + { + if dead_unwinds.map_or(true, |dead| !dead.contains(bb)) { + propagate(pred, exit_state); + } + } + + _ => propagate(pred, exit_state), + } + } + } +} + +/// Dataflow that runs from the entry of a block (the first statement), to its exit (terminator). +pub struct Forward; + +impl Direction for Forward { + fn is_forward() -> bool { + true + } + + fn apply_effects_in_block( + analysis: &A, + state: &mut BitSet, + block: BasicBlock, + block_data: &mir::BasicBlockData<'tcx>, + ) where + A: Analysis<'tcx>, + { + 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_effects_in_block( + analysis: &A, + trans: &mut GenKillSet, + 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); + } + + let terminator = block_data.terminator(); + let location = Location { block, statement_index: block_data.statements.len() }; + analysis.before_terminator_effect(trans, terminator, location); + analysis.terminator_effect(trans, terminator, location); + } + + fn apply_effects_in_range( + analysis: &A, + state: &mut BitSet, + block: BasicBlock, + block_data: &mir::BasicBlockData<'tcx>, + effects: RangeInclusive, + ) where + A: Analysis<'tcx>, + { + let (from, to) = (*effects.start(), *effects.end()); + let terminator_index = block_data.statements.len(); + + assert!(to.statement_index <= terminator_index); + assert!(!to.precedes_in_forward_order(from)); + + // If we have applied the before affect of the statement or terminator at `from` but not its + // after effect, do so now and start the loop below from the next statement. + + let first_unapplied_index = match from.effect { + Effect::Before => from.statement_index, + + Effect::Primary if from.statement_index == terminator_index => { + debug_assert_eq!(from, to); + + let location = Location { block, statement_index: terminator_index }; + let terminator = block_data.terminator(); + analysis.apply_terminator_effect(state, terminator, location); + return; + } + + Effect::Primary => { + let location = Location { block, statement_index: from.statement_index }; + let statement = &block_data.statements[from.statement_index]; + analysis.apply_statement_effect(state, statement, location); + + // If we only needed to apply the after effect of the statement at `idx`, we are done. + if from == to { + return; + } + + from.statement_index + 1 + } + }; + + // Handle all statements between `from` and `to` whose effects must be applied in full. + + for statement_index in first_unapplied_index..to.statement_index { + let location = Location { block, statement_index }; + let statement = &block_data.statements[statement_index]; + analysis.apply_before_statement_effect(state, statement, location); + analysis.apply_statement_effect(state, statement, location); + } + + // Handle the statement or terminator at `to`. + + let location = Location { block, statement_index: to.statement_index }; + if to.statement_index == terminator_index { + let terminator = block_data.terminator(); + analysis.apply_before_terminator_effect(state, terminator, location); + + if to.effect == Effect::Primary { + analysis.apply_terminator_effect(state, terminator, location); + } + } else { + let statement = &block_data.statements[to.statement_index]; + analysis.apply_before_statement_effect(state, statement, location); + + if to.effect == Effect::Primary { + analysis.apply_statement_effect(state, statement, location); + } + } + } + + fn visit_results_in_block( + state: &mut F, + block: BasicBlock, + block_data: &'mir mir::BasicBlockData<'tcx>, + results: &R, + vis: &mut impl ResultsVisitor<'mir, 'tcx, FlowState = F>, + ) where + R: ResultsVisitable<'tcx, FlowState = F>, + { + results.reset_to_block_entry(state, block); + + vis.visit_block_start(state, block_data, block); + + for (statement_index, stmt) in block_data.statements.iter().enumerate() { + let loc = Location { block, statement_index }; + results.reconstruct_before_statement_effect(state, stmt, loc); + vis.visit_statement_before_primary_effect(state, stmt, loc); + results.reconstruct_statement_effect(state, stmt, loc); + vis.visit_statement_after_primary_effect(state, stmt, loc); + } + + let loc = Location { block, statement_index: block_data.statements.len() }; + let term = block_data.terminator(); + results.reconstruct_before_terminator_effect(state, term, loc); + vis.visit_terminator_before_primary_effect(state, term, loc); + results.reconstruct_terminator_effect(state, term, loc); + vis.visit_terminator_after_primary_effect(state, term, loc); + + vis.visit_block_end(state, block_data, block); + } + + fn join_state_into_successors_of( + analysis: &A, + tcx: TyCtxt<'tcx>, + body: &mir::Body<'tcx>, + dead_unwinds: Option<&BitSet>, + exit_state: &mut BitSet, + (bb, bb_data): (BasicBlock, &'_ mir::BasicBlockData<'tcx>), + mut propagate: impl FnMut(BasicBlock, &BitSet), + ) where + A: Analysis<'tcx>, + { + use mir::TerminatorKind::*; + match bb_data.terminator().kind { + Return | Resume | Abort | GeneratorDrop | Unreachable => {} + + Goto { target } => propagate(target, exit_state), + + Assert { target, cleanup: unwind, expected: _, msg: _, cond: _ } + | Drop { target, unwind, location: _ } + | DropAndReplace { target, unwind, value: _, location: _ } + | FalseUnwind { real_target: target, unwind } => { + if let Some(unwind) = unwind { + if dead_unwinds.map_or(true, |dead| !dead.contains(bb)) { + propagate(unwind, exit_state); + } + } + + propagate(target, exit_state); + } + + FalseEdges { real_target, imaginary_target } => { + propagate(real_target, exit_state); + propagate(imaginary_target, exit_state); + } + + Yield { resume: target, drop, resume_arg, value: _ } => { + if let Some(drop) = drop { + propagate(drop, exit_state); + } + + analysis.apply_yield_resume_effect(exit_state, target, resume_arg); + propagate(target, exit_state); + } + + Call { cleanup, destination, ref func, ref args, from_hir_call: _ } => { + if let Some(unwind) = cleanup { + if dead_unwinds.map_or(true, |dead| !dead.contains(bb)) { + propagate(unwind, exit_state); + } + } + + if let Some((dest_place, target)) = destination { + // N.B.: This must be done *last*, otherwise the unwind path will see the call + // return effect. + analysis.apply_call_return_effect(exit_state, bb, func, args, dest_place); + propagate(target, exit_state); + } + } + + SwitchInt { ref targets, ref values, ref discr, switch_ty: _ } => { + let enum_ = discr + .place() + .and_then(|discr| switch_on_enum_discriminant(tcx, &body, bb_data, discr)); + match enum_ { + // If this is a switch on an enum discriminant, a custom effect may be applied + // along each outgoing edge. + Some((enum_place, enum_def)) => { + // 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 mut tmp = BitSet::new_empty(exit_state.domain_size()); + let mut discriminants = enum_def.discriminants(tcx); + for (value, target) in values.iter().zip(targets.iter().copied()) { + let (variant_idx, _) = + discriminants.find(|&(_, discr)| discr.val == *value).expect( + "Order of `AdtDef::discriminants` differed \ + from that of `SwitchInt::values`", + ); + + tmp.overwrite(exit_state); + analysis.apply_discriminant_switch_effect( + &mut tmp, + bb, + enum_place, + enum_def, + variant_idx, + ); + propagate(target, &tmp); + } + + // Move out of `tmp` so we don't accidentally use it below. + std::mem::drop(tmp); + + // Propagate dataflow state along the "otherwise" edge. + let otherwise = targets.last().copied().unwrap(); + propagate(otherwise, exit_state) + } + + // Otherwise, it's just a normal `SwitchInt`, and every successor sees the same + // exit state. + None => { + for target in targets.iter().copied() { + propagate(target, exit_state); + } + } + } + } + } + } +} + +/// 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: +/// _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( + tcx: TyCtxt<'tcx>, + body: &'mir mir::Body<'tcx>, + block: &'mir mir::BasicBlockData<'tcx>, + switch_on: mir::Place<'tcx>, +) -> Option<(mir::Place<'tcx>, &'tcx ty::AdtDef)> { + match block.statements.last().map(|stmt| &stmt.kind) { + Some(mir::StatementKind::Assign(box (lhs, mir::Rvalue::Discriminant(discriminated)))) + if *lhs == switch_on => + { + match &discriminated.ty(body, tcx).ty.kind { + ty::Adt(def, _) => 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(..) => None, + + t => bug!("`discriminant` called on unexpected type {:?}", t), + } + } + + _ => None, + } +} diff --git a/src/librustc_mir/dataflow/framework/engine.rs b/src/librustc_mir/dataflow/framework/engine.rs index 2a9d2d99c8a..32e569fdc35 100644 --- a/src/librustc_mir/dataflow/framework/engine.rs +++ b/src/librustc_mir/dataflow/framework/engine.rs @@ -9,14 +9,58 @@ use rustc_hir::def_id::DefId; use rustc_index::bit_set::BitSet; use rustc_index::vec::IndexVec; -use rustc_middle::mir::{self, traversal, BasicBlock, Location}; +use rustc_middle::mir::{self, traversal, BasicBlock}; use rustc_middle::ty::{self, TyCtxt}; use rustc_span::symbol::{sym, Symbol}; use super::graphviz; -use super::{Analysis, GenKillAnalysis, GenKillSet, Results}; +use super::{ + visit_results, Analysis, Direction, GenKillAnalysis, GenKillSet, ResultsCursor, ResultsVisitor, +}; use crate::util::pretty::dump_enabled; +/// A dataflow analysis that has converged to fixpoint. +pub struct Results<'tcx, A> +where + A: Analysis<'tcx>, +{ + pub analysis: A, + pub(super) entry_sets: IndexVec>, +} + +impl Results<'tcx, A> +where + A: Analysis<'tcx>, +{ + /// Creates a `ResultsCursor` that can inspect these `Results`. + pub fn into_results_cursor(self, body: &'mir mir::Body<'tcx>) -> ResultsCursor<'mir, 'tcx, A> { + ResultsCursor::new(body, self) + } + + /// Gets the dataflow state for the given block. + pub fn entry_set_for_block(&self, block: BasicBlock) -> &BitSet { + &self.entry_sets[block] + } + + pub fn visit_with( + &self, + body: &'mir mir::Body<'tcx>, + blocks: impl IntoIterator, + vis: &mut impl ResultsVisitor<'mir, 'tcx, FlowState = BitSet>, + ) { + visit_results(body, blocks, self, vis) + } + + pub fn visit_in_rpo_with( + &self, + body: &'mir mir::Body<'tcx>, + vis: &mut impl ResultsVisitor<'mir, 'tcx, FlowState = BitSet>, + ) { + let blocks = mir::traversal::reverse_postorder(body); + visit_results(body, blocks.map(|(bb, _)| bb), self, vis) + } +} + /// A solver for dataflow problems. pub struct Engine<'a, 'tcx, A> where @@ -61,17 +105,7 @@ pub fn new_gen_kill( for (block, block_data) in body.basic_blocks().iter_enumerated() { let trans = &mut trans_for_block[block]; - - for (i, statement) in block_data.statements.iter().enumerate() { - let loc = Location { block, statement_index: i }; - analysis.before_statement_effect(trans, statement, loc); - analysis.statement_effect(trans, statement, loc); - } - - let terminator = block_data.terminator(); - let loc = Location { block, statement_index: block_data.statements.len() }; - analysis.before_terminator_effect(trans, terminator, loc); - analysis.terminator_effect(trans, terminator, loc); + A::Direction::gen_kill_effects_in_block(&analysis, trans, block, block_data); } Self::new(tcx, body, def_id, analysis, Some(trans_for_block)) @@ -111,9 +145,13 @@ fn new( BitSet::new_empty(bits_per_block) }; - let mut entry_sets = IndexVec::from_elem(bottom_value_set, body.basic_blocks()); + let mut entry_sets = IndexVec::from_elem(bottom_value_set.clone(), body.basic_blocks()); analysis.initialize_start_block(body, &mut entry_sets[mir::START_BLOCK]); + if A::Direction::is_backward() && entry_sets[mir::START_BLOCK] != bottom_value_set { + bug!("`initialize_start_block` is not yet supported for backward dataflow analyses"); + } + Engine { analysis, bits_per_block, @@ -137,251 +175,79 @@ pub fn dead_unwinds(mut self, dead_unwinds: &'a BitSet) -> Self { } /// Computes the fixpoint for this dataflow problem and returns it. - pub fn iterate_to_fixpoint(mut self) -> Results<'tcx, A> { - let mut temp_state = BitSet::new_empty(self.bits_per_block); + pub fn iterate_to_fixpoint(self) -> Results<'tcx, A> { + let Engine { + analysis, + bits_per_block, + body, + dead_unwinds, + def_id, + mut entry_sets, + tcx, + trans_for_block, + .. + } = self; let mut dirty_queue: WorkQueue = - WorkQueue::with_none(self.body.basic_blocks().len()); + WorkQueue::with_none(body.basic_blocks().len()); - for (bb, _) in traversal::reverse_postorder(self.body) { - dirty_queue.insert(bb); + if A::Direction::is_forward() { + for (bb, _) in traversal::reverse_postorder(body) { + dirty_queue.insert(bb); + } + } else { + // Reverse post-order on the reverse CFG may generate a better iteration order for + // backward dataflow analyses, but probably not enough to matter. + for (bb, _) in traversal::postorder(body) { + dirty_queue.insert(bb); + } } // Add blocks that are not reachable from START_BLOCK to the work queue. These blocks will // be processed after the ones added above. - for bb in self.body.basic_blocks().indices() { + // + // FIXME(ecstaticmorse): Is this actually necessary? In principle, we shouldn't need to + // know the dataflow state in unreachable basic blocks. + for bb in body.basic_blocks().indices() { dirty_queue.insert(bb); } + let mut state = BitSet::new_empty(bits_per_block); while let Some(bb) = dirty_queue.pop() { - let bb_data = &self.body[bb]; - let on_entry = &self.entry_sets[bb]; + let bb_data = &body[bb]; - temp_state.overwrite(on_entry); - self.apply_whole_block_effect(&mut temp_state, bb, bb_data); + // Apply the block transfer function, using the cached one if it exists. + state.overwrite(&entry_sets[bb]); + match &trans_for_block { + Some(trans_for_block) => trans_for_block[bb].apply(&mut state), + None => A::Direction::apply_effects_in_block(&analysis, &mut state, bb, bb_data), + } - self.propagate_bits_into_graph_successors_of( - &mut temp_state, + A::Direction::join_state_into_successors_of( + &analysis, + tcx, + body, + dead_unwinds, + &mut state, (bb, bb_data), - &mut dirty_queue, + |target: BasicBlock, state: &BitSet| { + let set_changed = analysis.join(&mut entry_sets[target], state); + if set_changed { + dirty_queue.insert(target); + } + }, ); } - let Engine { tcx, body, def_id, trans_for_block, entry_sets, analysis, .. } = self; let results = Results { analysis, entry_sets }; - let res = write_graphviz_results(tcx, def_id, body, &results, trans_for_block); + let res = write_graphviz_results(tcx, def_id, &body, &results, trans_for_block); if let Err(e) = res { warn!("Failed to write graphviz dataflow results: {}", e); } results } - - /// Applies the cumulative effect of an entire block, excluding the call return effect if one - /// exists. - fn apply_whole_block_effect( - &self, - state: &mut BitSet, - block: BasicBlock, - block_data: &mir::BasicBlockData<'tcx>, - ) { - // Use the cached block transfer function if available. - if let Some(trans_for_block) = &self.trans_for_block { - trans_for_block[block].apply(state); - return; - } - - // Otherwise apply effects one-by-one. - - for (statement_index, statement) in block_data.statements.iter().enumerate() { - let location = Location { block, statement_index }; - self.analysis.apply_before_statement_effect(state, statement, location); - self.analysis.apply_statement_effect(state, statement, location); - } - - let terminator = block_data.terminator(); - let location = Location { block, statement_index: block_data.statements.len() }; - self.analysis.apply_before_terminator_effect(state, terminator, location); - self.analysis.apply_terminator_effect(state, terminator, location); - } - - fn propagate_bits_into_graph_successors_of( - &mut self, - in_out: &mut BitSet, - (bb, bb_data): (BasicBlock, &'a mir::BasicBlockData<'tcx>), - dirty_list: &mut WorkQueue, - ) { - use mir::TerminatorKind::*; - - match bb_data.terminator().kind { - Return | Resume | Abort | GeneratorDrop | Unreachable => {} - - Goto { target } - | Assert { target, cleanup: None, .. } - | Drop { target, location: _, unwind: None } - | DropAndReplace { target, value: _, location: _, unwind: None } => { - self.propagate_bits_into_entry_set_for(in_out, target, dirty_list) - } - - Yield { resume: target, drop, resume_arg, .. } => { - if let Some(drop) = drop { - self.propagate_bits_into_entry_set_for(in_out, drop, dirty_list); - } - - self.analysis.apply_yield_resume_effect(in_out, target, resume_arg); - self.propagate_bits_into_entry_set_for(in_out, target, dirty_list); - } - - Assert { target, cleanup: Some(unwind), .. } - | Drop { target, location: _, unwind: Some(unwind) } - | DropAndReplace { target, value: _, location: _, unwind: Some(unwind) } => { - self.propagate_bits_into_entry_set_for(in_out, target, dirty_list); - if self.dead_unwinds.map_or(true, |bbs| !bbs.contains(bb)) { - self.propagate_bits_into_entry_set_for(in_out, unwind, dirty_list); - } - } - - SwitchInt { ref targets, ref values, ref discr, .. } => { - let Engine { tcx, body, .. } = *self; - let enum_ = discr - .place() - .and_then(|discr| switch_on_enum_discriminant(tcx, body, bb_data, discr)); - match enum_ { - // If this is a switch on an enum discriminant, a custom effect may be applied - // along each outgoing edge. - Some((enum_place, enum_def)) => { - self.propagate_bits_into_enum_discriminant_switch_successors( - in_out, bb, enum_def, enum_place, dirty_list, &*values, &*targets, - ); - } - - // Otherwise, it's just a normal `SwitchInt`, and every successor sees the same - // exit state. - None => { - for target in targets.iter().copied() { - self.propagate_bits_into_entry_set_for(&in_out, target, dirty_list); - } - } - } - } - - Call { cleanup, ref destination, ref func, ref args, .. } => { - if let Some(unwind) = cleanup { - if self.dead_unwinds.map_or(true, |bbs| !bbs.contains(bb)) { - self.propagate_bits_into_entry_set_for(in_out, unwind, dirty_list); - } - } - - if let Some((dest_place, dest_bb)) = *destination { - // N.B.: This must be done *last*, otherwise the unwind path will see the call - // return effect. - self.analysis.apply_call_return_effect(in_out, bb, func, args, dest_place); - self.propagate_bits_into_entry_set_for(in_out, dest_bb, dirty_list); - } - } - - FalseEdges { real_target, imaginary_target } => { - self.propagate_bits_into_entry_set_for(in_out, real_target, dirty_list); - self.propagate_bits_into_entry_set_for(in_out, imaginary_target, dirty_list); - } - - FalseUnwind { real_target, unwind } => { - self.propagate_bits_into_entry_set_for(in_out, real_target, dirty_list); - if let Some(unwind) = unwind { - if self.dead_unwinds.map_or(true, |bbs| !bbs.contains(bb)) { - self.propagate_bits_into_entry_set_for(in_out, unwind, dirty_list); - } - } - } - } - } - - fn propagate_bits_into_entry_set_for( - &mut self, - in_out: &BitSet, - bb: BasicBlock, - dirty_queue: &mut WorkQueue, - ) { - let entry_set = &mut self.entry_sets[bb]; - let set_changed = self.analysis.join(entry_set, &in_out); - if set_changed { - dirty_queue.insert(bb); - } - } - - fn propagate_bits_into_enum_discriminant_switch_successors( - &mut self, - in_out: &mut BitSet, - bb: BasicBlock, - enum_def: &'tcx ty::AdtDef, - enum_place: mir::Place<'tcx>, - dirty_list: &mut WorkQueue, - values: &[u128], - targets: &[BasicBlock], - ) { - // 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 mut tmp = BitSet::new_empty(in_out.domain_size()); - let mut discriminants = enum_def.discriminants(self.tcx); - for (value, target) in values.iter().zip(targets.iter().copied()) { - let (variant_idx, _) = discriminants.find(|&(_, discr)| discr.val == *value).expect( - "Order of `AdtDef::discriminants` differed from that of `SwitchInt::values`", - ); - - tmp.overwrite(in_out); - self.analysis.apply_discriminant_switch_effect( - &mut tmp, - bb, - enum_place, - enum_def, - variant_idx, - ); - self.propagate_bits_into_entry_set_for(&tmp, target, dirty_list); - } - - std::mem::drop(tmp); - - // Propagate dataflow state along the "otherwise" edge. - let otherwise = targets.last().copied().unwrap(); - self.propagate_bits_into_entry_set_for(&in_out, otherwise, dirty_list); - } -} - -/// 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: -/// _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( - tcx: TyCtxt<'tcx>, - body: &'mir mir::Body<'tcx>, - block: &'mir mir::BasicBlockData<'tcx>, - switch_on: mir::Place<'tcx>, -) -> Option<(mir::Place<'tcx>, &'tcx ty::AdtDef)> { - match block.statements.last().map(|stmt| &stmt.kind) { - Some(mir::StatementKind::Assign(box (lhs, mir::Rvalue::Discriminant(discriminated)))) - if *lhs == switch_on => - { - match &discriminated.ty(body, tcx).ty.kind { - ty::Adt(def, _) => 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(..) => None, - - t => bug!("`discriminant` called on unexpected type {:?}", t), - } - } - - _ => None, - } } // Graphviz @@ -431,12 +297,12 @@ fn write_graphviz_results( if let Some(trans_for_block) = block_transfer_functions { Box::new(graphviz::BlockTransferFunc::new(body, trans_for_block)) } else { - Box::new(graphviz::SimpleDiff::new(bits_per_block)) + Box::new(graphviz::SimpleDiff::new(body, &results)) } } // Default to the `SimpleDiff` output style. - _ => Box::new(graphviz::SimpleDiff::new(bits_per_block)), + _ => Box::new(graphviz::SimpleDiff::new(body, &results)), }; debug!("printing dataflow results for {:?} to {}", def_id, path.display()); diff --git a/src/librustc_mir/dataflow/framework/graphviz.rs b/src/librustc_mir/dataflow/framework/graphviz.rs index bdd41121359..e3ba26eaf8b 100644 --- a/src/librustc_mir/dataflow/framework/graphviz.rs +++ b/src/librustc_mir/dataflow/framework/graphviz.rs @@ -8,7 +8,7 @@ use rustc_index::vec::{Idx, IndexVec}; use rustc_middle::mir::{self, BasicBlock, Body, Location}; -use super::{Analysis, GenKillSet, Results, ResultsRefCursor}; +use super::{Analysis, Direction, GenKillSet, Results, ResultsRefCursor}; use crate::util::graphviz_safe_def_name; pub struct Formatter<'a, 'tcx, A> @@ -49,7 +49,7 @@ pub struct CfgEdge { index: usize, } -fn outgoing_edges(body: &Body<'_>, bb: BasicBlock) -> Vec { +fn dataflow_successors(body: &Body<'tcx>, bb: BasicBlock) -> Vec { body[bb] .terminator() .successors() @@ -105,7 +105,7 @@ fn edges(&self) -> dot::Edges<'_, Self::Edge> { self.body .basic_blocks() .indices() - .flat_map(|bb| outgoing_edges(self.body, bb)) + .flat_map(|bb| dataflow_successors(self.body, bb)) .collect::>() .into() } @@ -192,12 +192,12 @@ fn write_node_label( self.write_block_header_with_state_columns(w, block)?; } - // C: Entry state + // C: State at start of block self.bg = Background::Light; self.results.seek_to_block_start(block); let block_entry_state = self.results.get().clone(); - self.write_row_with_full_state(w, "", "(on entry)")?; + self.write_row_with_full_state(w, "", "(on start)")?; // D: Statement transfer functions for (i, statement) in body[block].statements.iter().enumerate() { @@ -214,37 +214,72 @@ fn write_node_label( self.write_row_for_location(w, "T", &terminator_str, terminator_loc)?; - // F: Exit state + // F: State at end of block // Write the full dataflow state immediately after the terminator if it differs from the // state at block entry. - self.results.seek_after(terminator_loc); - if self.results.get() != &block_entry_state { + self.results.seek_to_block_end(block); + if self.results.get() != &block_entry_state || A::Direction::is_backward() { let after_terminator_name = match terminator.kind { mir::TerminatorKind::Call { destination: Some(_), .. } => "(on unwind)", - _ => "(on exit)", + _ => "(on end)", }; self.write_row_with_full_state(w, "", after_terminator_name)?; } // Write any changes caused by terminator-specific effects - if let mir::TerminatorKind::Call { destination: Some(_), .. } = terminator.kind { - let num_state_columns = self.num_state_columns(); - self.write_row(w, "", "(on successful return)", |this, w, fmt| { - write!( - w, - r#""#, - colspan = num_state_columns, - fmt = fmt, - )?; - - let state_on_unwind = this.results.get().clone(); - this.results.seek_after_assume_success(terminator_loc); - write_diff(w, this.results.analysis(), &state_on_unwind, this.results.get())?; - - write!(w, "") - })?; + let num_state_columns = self.num_state_columns(); + match terminator.kind { + mir::TerminatorKind::Call { + destination: Some((return_place, _)), + ref func, + ref args, + .. + } => { + self.write_row(w, "", "(on successful return)", |this, w, fmt| { + write!( + w, + r#""#, + colspan = num_state_columns, + fmt = fmt, + )?; + + let state_on_unwind = this.results.get().clone(); + this.results.apply_custom_effect(|analysis, state| { + analysis.apply_call_return_effect(state, block, func, args, return_place); + }); + + write_diff(w, this.results.analysis(), &state_on_unwind, this.results.get())?; + write!(w, "") + })?; + } + + mir::TerminatorKind::Yield { resume, resume_arg, .. } => { + self.write_row(w, "", "(on yield resume)", |this, w, fmt| { + write!( + w, + r#""#, + colspan = num_state_columns, + fmt = fmt, + )?; + + let state_on_generator_drop = this.results.get().clone(); + this.results.apply_custom_effect(|analysis, state| { + analysis.apply_yield_resume_effect(state, resume, resume_arg); + }); + + write_diff( + w, + this.results.analysis(), + &state_on_generator_drop, + this.results.get(), + )?; + write!(w, "") + })?; + } + + _ => {} }; write!(w, "") @@ -403,18 +438,23 @@ fn write_state_for_location( } /// Prints a single column containing the state vector immediately *after* each statement. -pub struct SimpleDiff { - prev_state: BitSet, - prev_loc: Location, +pub struct SimpleDiff<'a, 'tcx, A> +where + A: Analysis<'tcx>, +{ + prev_state: ResultsRefCursor<'a, 'a, 'tcx, A>, } -impl SimpleDiff { - pub fn new(bits_per_block: usize) -> Self { - SimpleDiff { prev_state: BitSet::new_empty(bits_per_block), prev_loc: Location::START } +impl SimpleDiff<'a, 'tcx, A> +where + A: Analysis<'tcx>, +{ + pub fn new(body: &'a Body<'tcx>, results: &'a Results<'tcx, A>) -> Self { + SimpleDiff { prev_state: ResultsRefCursor::new(body, results) } } } -impl StateFormatter<'tcx, A> for SimpleDiff +impl StateFormatter<'tcx, A> for SimpleDiff<'_, 'tcx, A> where A: Analysis<'tcx>, { @@ -429,20 +469,27 @@ fn write_state_for_location( results: &mut ResultsRefCursor<'_, '_, 'tcx, A>, location: Location, ) -> io::Result<()> { - if location.statement_index == 0 { - results.seek_to_block_start(location.block); - self.prev_state.overwrite(results.get()); + if A::Direction::is_forward() { + if location.statement_index == 0 { + self.prev_state.seek_to_block_start(location.block); + } else { + self.prev_state.seek_after_primary_effect(Location { + statement_index: location.statement_index - 1, + ..location + }); + } } else { - // Ensure that we are visiting statements in order, so `prev_state` is correct. - assert_eq!(self.prev_loc.successor_within_block(), location); + if location == results.body().terminator_loc(location.block) { + self.prev_state.seek_to_block_end(location.block); + } else { + self.prev_state.seek_after_primary_effect(location.successor_within_block()); + } } - self.prev_loc = location; write!(w, r#""#, fmt = fmt)?; - results.seek_after(location); + results.seek_after_primary_effect(location); let curr_state = results.get(); - write_diff(&mut w, results.analysis(), &self.prev_state, curr_state)?; - self.prev_state.overwrite(curr_state); + write_diff(&mut w, results.analysis(), self.prev_state.get(), curr_state)?; write!(w, "") } } @@ -476,7 +523,7 @@ fn write_state_for_location( location: Location, ) -> io::Result<()> { if location.statement_index == 0 { - results.seek_to_block_start(location.block); + results.seek_to_block_entry(location.block); self.prev_state.overwrite(results.get()); } else { // Ensure that we are visiting statements in order, so `prev_state` is correct. @@ -488,7 +535,7 @@ fn write_state_for_location( // Before write!(w, r#""#, fmt = fmt)?; - results.seek_before(location); + results.seek_before_primary_effect(location); let curr_state = results.get(); write_diff(&mut w, results.analysis(), &self.prev_state, curr_state)?; self.prev_state.overwrite(curr_state); @@ -497,7 +544,7 @@ fn write_state_for_location( // After write!(w, r#""#, fmt = fmt)?; - results.seek_after(location); + results.seek_after_primary_effect(location); let curr_state = results.get(); write_diff(&mut w, results.analysis(), &self.prev_state, curr_state)?; self.prev_state.overwrite(curr_state); diff --git a/src/librustc_mir/dataflow/framework/mod.rs b/src/librustc_mir/dataflow/framework/mod.rs index 06da8799dd4..a21bbacb467 100644 --- a/src/librustc_mir/dataflow/framework/mod.rs +++ b/src/librustc_mir/dataflow/framework/mod.rs @@ -30,67 +30,28 @@ //! //! [gen-kill]: https://en.wikipedia.org/wiki/Data-flow_analysis#Bit_vector_problems +use std::cmp::Ordering; use std::io; use rustc_hir::def_id::DefId; use rustc_index::bit_set::{BitSet, HybridBitSet}; -use rustc_index::vec::{Idx, IndexVec}; +use rustc_index::vec::Idx; use rustc_middle::mir::{self, BasicBlock, Location}; use rustc_middle::ty::{self, TyCtxt}; use rustc_target::abi::VariantIdx; mod cursor; +mod direction; mod engine; mod graphviz; mod visitor; pub use self::cursor::{ResultsCursor, ResultsRefCursor}; -pub use self::engine::Engine; +pub use self::direction::{Backward, Direction, Forward}; +pub use self::engine::{Engine, Results}; pub use self::visitor::{visit_results, ResultsVisitor}; pub use self::visitor::{BorrowckFlowState, BorrowckResults}; -/// A dataflow analysis that has converged to fixpoint. -pub struct Results<'tcx, A> -where - A: Analysis<'tcx>, -{ - pub analysis: A, - entry_sets: IndexVec>, -} - -impl Results<'tcx, A> -where - A: Analysis<'tcx>, -{ - /// Creates a `ResultsCursor` that can inspect these `Results`. - pub fn into_results_cursor(self, body: &'mir mir::Body<'tcx>) -> ResultsCursor<'mir, 'tcx, A> { - ResultsCursor::new(body, self) - } - - /// Gets the entry set for the given block. - pub fn entry_set_for_block(&self, block: BasicBlock) -> &BitSet { - &self.entry_sets[block] - } - - pub fn visit_with( - &self, - body: &'mir mir::Body<'tcx>, - blocks: impl IntoIterator, - vis: &mut impl ResultsVisitor<'mir, 'tcx, FlowState = BitSet>, - ) { - visit_results(body, blocks, self, vis) - } - - pub fn visit_in_rpo_with( - &self, - body: &'mir mir::Body<'tcx>, - vis: &mut impl ResultsVisitor<'mir, 'tcx, FlowState = BitSet>, - ) { - let blocks = mir::traversal::reverse_postorder(body); - visit_results(body, blocks.map(|(bb, _)| bb), self, vis) - } -} - /// Parameterization for the precise form of data flow that is used. /// /// `BottomValue` determines whether the initial entry set for each basic block is empty or full. @@ -144,6 +105,9 @@ pub trait AnalysisDomain<'tcx>: BottomValue { /// The type of the elements in the state vector. type Idx: Idx; + /// The direction of this analyis. Either `Forward` or `Backward`. + type Direction: Direction = Forward; + /// A descriptive name for this analysis. Used only for debugging. /// /// This name should be brief and contain no spaces, periods or other characters that are not @@ -155,6 +119,13 @@ pub trait AnalysisDomain<'tcx>: BottomValue { /// Mutates the entry set of the `START_BLOCK` to contain the initial state for dataflow /// analysis. + /// + /// For backward analyses, initial state besides the bottom value is not yet supported. Trying + /// to mutate the initial state will result in a panic. + // + // FIXME: For backward dataflow analyses, the initial state should be applied to every basic + // 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 generators, however. fn initialize_start_block(&self, body: &mir::Body<'tcx>, state: &mut BitSet); /// Prints an element in the state vector for debugging. @@ -247,6 +218,8 @@ fn apply_yield_resume_effect( /// /// Much like `apply_call_return_effect`, this effect is only propagated along a single /// outgoing edge from this basic block. + /// + /// FIXME: This class of effects is not supported for backward dataflow analyses. fn apply_discriminant_switch_effect( &self, _state: &mut BitSet, @@ -338,7 +311,7 @@ fn call_return_effect( /// See `Analysis::apply_yield_resume_effect`. fn yield_resume_effect( &self, - _trans: &mut BitSet, + _trans: &mut impl GenKill, _resume_block: BasicBlock, _resume_place: mir::Place<'tcx>, ) { @@ -520,5 +493,64 @@ fn kill(&mut self, elem: T) { } } +// NOTE: DO NOT CHANGE VARIANT ORDER. The derived `Ord` impls rely on the current order. +#[derive(Clone, Copy, Debug, PartialEq, Eq, PartialOrd, Ord)] +pub enum Effect { + /// The "before" effect (e.g., `apply_before_statement_effect`) for a statement (or + /// terminator). + Before, + + /// The "primary" effect (e.g., `apply_statement_effect`) for a statement (or terminator). + Primary, +} + +impl Effect { + pub const fn at_index(self, statement_index: usize) -> EffectIndex { + EffectIndex { effect: self, statement_index } + } +} + +#[derive(Clone, Copy, Debug, PartialEq, Eq)] +pub struct EffectIndex { + statement_index: usize, + effect: Effect, +} + +impl EffectIndex { + fn next_in_forward_order(self) -> Self { + match self.effect { + Effect::Before => Effect::Primary.at_index(self.statement_index), + Effect::Primary => Effect::Before.at_index(self.statement_index + 1), + } + } + + fn next_in_backward_order(self) -> Self { + match self.effect { + Effect::Before => Effect::Primary.at_index(self.statement_index), + Effect::Primary => Effect::Before.at_index(self.statement_index - 1), + } + } + + /// Returns `true` if the effect at `self` should be applied eariler than the effect at `other` + /// in forward order. + fn precedes_in_forward_order(self, other: Self) -> bool { + let ord = self + .statement_index + .cmp(&other.statement_index) + .then_with(|| self.effect.cmp(&other.effect)); + ord == Ordering::Less + } + + /// Returns `true` if the effect at `self` should be applied earlier than the effect at `other` + /// in backward order. + fn precedes_in_backward_order(self, other: Self) -> bool { + let ord = other + .statement_index + .cmp(&self.statement_index) + .then_with(|| self.effect.cmp(&other.effect)); + ord == Ordering::Less + } +} + #[cfg(test)] mod tests; diff --git a/src/librustc_mir/dataflow/framework/tests.rs b/src/librustc_mir/dataflow/framework/tests.rs index 8c65b7452d1..a8dce7079b7 100644 --- a/src/librustc_mir/dataflow/framework/tests.rs +++ b/src/librustc_mir/dataflow/framework/tests.rs @@ -1,5 +1,7 @@ //! A test for the logic that updates the state in a `ResultsCursor` during seek. +use std::marker::PhantomData; + use rustc_index::bit_set::BitSet; use rustc_index::vec::IndexVec; use rustc_middle::mir::{self, BasicBlock, Location}; @@ -9,16 +11,6 @@ use super::*; use crate::dataflow::BottomValue; -/// Returns `true` if the given location points to a `Call` terminator that can return -/// successfully. -fn is_call_terminator_non_diverging(body: &mir::Body<'_>, loc: Location) -> bool { - loc == body.terminator_loc(loc.block) - && matches!( - body[loc.block].terminator().kind, - mir::TerminatorKind::Call { destination: Some(_), .. } - ) -} - /// Creates a `mir::Body` with a few disconnected basic blocks. /// /// This is the `Body` that will be used by the `MockAnalysis` below. The shape of its CFG is not @@ -79,20 +71,20 @@ fn mock_body() -> mir::Body<'static> { /// | Location | Before | After | /// |------------------------|-------------------|--------| /// | (on_entry) | {102} || -/// | Statement 0 | +0 | +1 | +/// | statement 0 | +0 | +1 | /// | statement 1 | +2 | +3 | /// | `Call` terminator | +4 | +5 | /// | (on unwind) | {102,0,1,2,3,4,5} || -/// | (on successful return) | +6 || /// /// The `102` in the block's entry set is derived from the basic block index and ensures that the /// expected state is unique across all basic blocks. Remember, it is generated by /// `mock_entry_sets`, not from actually running `MockAnalysis` to fixpoint. -struct MockAnalysis<'tcx> { +struct MockAnalysis<'tcx, D> { body: &'tcx mir::Body<'tcx>, + dir: PhantomData, } -impl MockAnalysis<'tcx> { +impl MockAnalysis<'tcx, D> { const BASIC_BLOCK_OFFSET: usize = 100; /// The entry set for each `BasicBlock` is the ID of that block offset by a fixed amount to @@ -115,25 +107,14 @@ fn mock_entry_sets(&self) -> IndexVec> { } /// Returns the index that should be added to the dataflow state at the given target. - /// - /// This index is only unique within a given basic block. `SeekAfter` and - /// `SeekAfterAssumeCallReturns` have the same effect unless `target` is a `Call` terminator. - fn effect_at_target(&self, target: SeekTarget) -> Option { - use SeekTarget::*; - - let idx = match target { - BlockStart(_) => return None, - - AfterAssumeCallReturns(loc) if is_call_terminator_non_diverging(self.body, loc) => { - loc.statement_index * 2 + 2 - } - - Before(loc) => loc.statement_index * 2, - After(loc) | AfterAssumeCallReturns(loc) => loc.statement_index * 2 + 1, + fn effect(&self, loc: EffectIndex) -> usize { + let idx = match loc.effect { + Effect::Before => loc.statement_index * 2, + Effect::Primary => loc.statement_index * 2 + 1, }; assert!(idx < Self::BASIC_BLOCK_OFFSET, "Too many statements in basic block"); - Some(idx) + idx } /// Returns the expected state at the given `SeekTarget`. @@ -143,27 +124,48 @@ fn effect_at_target(&self, target: SeekTarget) -> Option { /// basic block. /// /// For example, the expected state when calling - /// `seek_before(Location { block: 2, statement_index: 2 })` would be `[102, 0, 1, 2, 3, 4]`. + /// `seek_before_primary_effect(Location { block: 2, statement_index: 2 })` + /// would be `[102, 0, 1, 2, 3, 4]`. fn expected_state_at_target(&self, target: SeekTarget) -> BitSet { + let block = target.block(); let mut ret = BitSet::new_empty(self.bits_per_block(self.body)); - ret.insert(Self::BASIC_BLOCK_OFFSET + target.block().index()); + ret.insert(Self::BASIC_BLOCK_OFFSET + block.index()); - if let Some(target_effect) = self.effect_at_target(target) { - for i in 0..=target_effect { - ret.insert(i); + let target = match target { + SeekTarget::BlockEntry { .. } => return ret, + SeekTarget::Before(loc) => Effect::Before.at_index(loc.statement_index), + SeekTarget::After(loc) => Effect::Primary.at_index(loc.statement_index), + }; + + let mut pos = if D::is_forward() { + Effect::Before.at_index(0) + } else { + Effect::Before.at_index(self.body[block].statements.len()) + }; + + loop { + ret.insert(self.effect(pos)); + + if pos == target { + return ret; } - } - ret + if D::is_forward() { + pos = pos.next_in_forward_order(); + } else { + pos = pos.next_in_backward_order(); + } + } } } -impl BottomValue for MockAnalysis<'tcx> { +impl BottomValue for MockAnalysis<'tcx, D> { const BOTTOM_VALUE: bool = false; } -impl AnalysisDomain<'tcx> for MockAnalysis<'tcx> { +impl AnalysisDomain<'tcx> for MockAnalysis<'tcx, D> { type Idx = usize; + type Direction = D; const NAME: &'static str = "mock"; @@ -176,14 +178,14 @@ fn initialize_start_block(&self, _: &mir::Body<'tcx>, _: &mut BitSet) } } -impl Analysis<'tcx> for MockAnalysis<'tcx> { +impl Analysis<'tcx> for MockAnalysis<'tcx, D> { fn apply_statement_effect( &self, state: &mut BitSet, _statement: &mir::Statement<'tcx>, location: Location, ) { - let idx = self.effect_at_target(SeekTarget::After(location)).unwrap(); + let idx = self.effect(Effect::Primary.at_index(location.statement_index)); assert!(state.insert(idx)); } @@ -193,7 +195,7 @@ fn apply_before_statement_effect( _statement: &mir::Statement<'tcx>, location: Location, ) { - let idx = self.effect_at_target(SeekTarget::Before(location)).unwrap(); + let idx = self.effect(Effect::Before.at_index(location.statement_index)); assert!(state.insert(idx)); } @@ -203,7 +205,7 @@ fn apply_terminator_effect( _terminator: &mir::Terminator<'tcx>, location: Location, ) { - let idx = self.effect_at_target(SeekTarget::After(location)).unwrap(); + let idx = self.effect(Effect::Primary.at_index(location.statement_index)); assert!(state.insert(idx)); } @@ -213,30 +215,26 @@ fn apply_before_terminator_effect( _terminator: &mir::Terminator<'tcx>, location: Location, ) { - let idx = self.effect_at_target(SeekTarget::Before(location)).unwrap(); + let idx = self.effect(Effect::Before.at_index(location.statement_index)); assert!(state.insert(idx)); } fn apply_call_return_effect( &self, - state: &mut BitSet, - block: BasicBlock, + _state: &mut BitSet, + _block: BasicBlock, _func: &mir::Operand<'tcx>, _args: &[mir::Operand<'tcx>], _return_place: mir::Place<'tcx>, ) { - let location = self.body.terminator_loc(block); - let idx = self.effect_at_target(SeekTarget::AfterAssumeCallReturns(location)).unwrap(); - assert!(state.insert(idx)); } } #[derive(Clone, Copy, Debug, PartialEq, Eq)] enum SeekTarget { - BlockStart(BasicBlock), + BlockEntry(BasicBlock), Before(Location), After(Location), - AfterAssumeCallReturns(Location), } impl SeekTarget { @@ -244,59 +242,35 @@ fn block(&self) -> BasicBlock { use SeekTarget::*; match *self { - BlockStart(block) => block, - Before(loc) | After(loc) | AfterAssumeCallReturns(loc) => loc.block, + BlockEntry(block) => block, + Before(loc) | After(loc) => loc.block, } } /// An iterator over all possible `SeekTarget`s in a given block in order, starting with - /// `BlockStart`. - /// - /// This includes both `After` and `AfterAssumeCallReturns` for every `Location`. + /// `BlockEntry`. fn iter_in_block(body: &mir::Body<'_>, block: BasicBlock) -> impl Iterator { let statements_and_terminator = (0..=body[block].statements.len()) - .flat_map(|i| (0..3).map(move |j| (i, j))) + .flat_map(|i| (0..2).map(move |j| (i, j))) .map(move |(i, kind)| { let loc = Location { block, statement_index: i }; match kind { 0 => SeekTarget::Before(loc), 1 => SeekTarget::After(loc), - 2 => SeekTarget::AfterAssumeCallReturns(loc), _ => unreachable!(), } }); - std::iter::once(SeekTarget::BlockStart(block)).chain(statements_and_terminator) + std::iter::once(SeekTarget::BlockEntry(block)).chain(statements_and_terminator) } } -#[test] -fn cursor_seek() { - let body = mock_body(); - let body = &body; - let analysis = MockAnalysis { body }; +fn test_cursor(analysis: MockAnalysis<'tcx, D>) { + let body = analysis.body; let mut cursor = Results { entry_sets: analysis.mock_entry_sets(), analysis }.into_results_cursor(body); - // Sanity check: the mock call return effect is unique and actually being applied. - let call_terminator_loc = Location { block: BasicBlock::from_usize(2), statement_index: 2 }; - assert!(is_call_terminator_non_diverging(body, call_terminator_loc)); - - let call_return_effect = cursor - .analysis() - .effect_at_target(SeekTarget::AfterAssumeCallReturns(call_terminator_loc)) - .unwrap(); - assert_ne!( - call_return_effect, - cursor.analysis().effect_at_target(SeekTarget::After(call_terminator_loc)).unwrap() - ); - - cursor.seek_after(call_terminator_loc); - assert!(!cursor.get().contains(call_return_effect)); - cursor.seek_after_assume_success(call_terminator_loc); - assert!(cursor.get().contains(call_return_effect)); - let every_target = || { body.basic_blocks() .iter_enumerated() @@ -307,10 +281,9 @@ fn cursor_seek() { use SeekTarget::*; match targ { - BlockStart(block) => cursor.seek_to_block_start(block), - Before(loc) => cursor.seek_before(loc), - After(loc) => cursor.seek_after(loc), - AfterAssumeCallReturns(loc) => cursor.seek_after_assume_success(loc), + BlockEntry(block) => cursor.seek_to_block_entry(block), + Before(loc) => cursor.seek_before_primary_effect(loc), + After(loc) => cursor.seek_after_primary_effect(loc), } assert_eq!(cursor.get(), &cursor.analysis().expected_state_at_target(targ)); @@ -325,8 +298,26 @@ fn cursor_seek() { seek_to_target(from); for to in every_target() { + dbg!(from); + dbg!(to); seek_to_target(to); seek_to_target(from); } } } + +#[test] +fn backward_cursor() { + let body = mock_body(); + let body = &body; + let analysis = MockAnalysis { body, dir: PhantomData:: }; + test_cursor(analysis) +} + +#[test] +fn forward_cursor() { + let body = mock_body(); + let body = &body; + let analysis = MockAnalysis { body, dir: PhantomData:: }; + test_cursor(analysis) +} diff --git a/src/librustc_mir/dataflow/framework/visitor.rs b/src/librustc_mir/dataflow/framework/visitor.rs index 9561b68398d..0df9322e7fe 100644 --- a/src/librustc_mir/dataflow/framework/visitor.rs +++ b/src/librustc_mir/dataflow/framework/visitor.rs @@ -1,50 +1,41 @@ use rustc_index::bit_set::BitSet; use rustc_middle::mir::{self, BasicBlock, Location}; -use super::{Analysis, Results}; +use super::{Analysis, Direction, Results}; use crate::dataflow::impls::{borrows::Borrows, EverInitializedPlaces, MaybeUninitializedPlaces}; /// Calls the corresponding method in `ResultsVisitor` for every location in a `mir::Body` with the /// dataflow state at that location. -pub fn visit_results( +pub fn visit_results( body: &'mir mir::Body<'tcx>, blocks: impl IntoIterator, - results: &impl ResultsVisitable<'tcx, FlowState = F>, + results: &V, vis: &mut impl ResultsVisitor<'mir, 'tcx, FlowState = F>, -) { +) where + V: ResultsVisitable<'tcx, FlowState = F>, +{ let mut state = results.new_flow_state(body); for block in blocks { let block_data = &body[block]; - results.reset_to_block_start(&mut state, block); - - for (statement_index, stmt) in block_data.statements.iter().enumerate() { - let loc = Location { block, statement_index }; - - results.reconstruct_before_statement_effect(&mut state, stmt, loc); - vis.visit_statement(&state, stmt, loc); - - results.reconstruct_statement_effect(&mut state, stmt, loc); - vis.visit_statement_exit(&state, stmt, loc); - } - - let loc = body.terminator_loc(block); - let term = block_data.terminator(); - - results.reconstruct_before_terminator_effect(&mut state, term, loc); - vis.visit_terminator(&state, term, loc); - - results.reconstruct_terminator_effect(&mut state, term, loc); - vis.visit_terminator_exit(&state, term, loc); + V::Direction::visit_results_in_block(&mut state, block, block_data, results, vis); } } pub trait ResultsVisitor<'mir, 'tcx> { type FlowState; + fn visit_block_start( + &mut self, + _state: &Self::FlowState, + _block_data: &'mir mir::BasicBlockData<'tcx>, + _block: BasicBlock, + ) { + } + /// Called with the `before_statement_effect` of the given statement applied to `state` but not /// its `statement_effect`. - fn visit_statement( + fn visit_statement_before_primary_effect( &mut self, _state: &Self::FlowState, _statement: &'mir mir::Statement<'tcx>, @@ -54,7 +45,7 @@ fn visit_statement( /// Called with both the `before_statement_effect` and the `statement_effect` of the given /// statement applied to `state`. - fn visit_statement_exit( + fn visit_statement_after_primary_effect( &mut self, _state: &Self::FlowState, _statement: &'mir mir::Statement<'tcx>, @@ -64,7 +55,7 @@ fn visit_statement_exit( /// Called with the `before_terminator_effect` of the given terminator applied to `state` but not /// its `terminator_effect`. - fn visit_terminator( + fn visit_terminator_before_primary_effect( &mut self, _state: &Self::FlowState, _terminator: &'mir mir::Terminator<'tcx>, @@ -76,13 +67,21 @@ fn visit_terminator( /// terminator applied to `state`. /// /// The `call_return_effect` (if one exists) will *not* be applied to `state`. - fn visit_terminator_exit( + fn visit_terminator_after_primary_effect( &mut self, _state: &Self::FlowState, _terminator: &'mir mir::Terminator<'tcx>, _location: Location, ) { } + + fn visit_block_end( + &mut self, + _state: &Self::FlowState, + _block_data: &'mir mir::BasicBlockData<'tcx>, + _block: BasicBlock, + ) { + } } /// Things that can be visited by a `ResultsVisitor`. @@ -90,15 +89,16 @@ fn visit_terminator_exit( /// This trait exists so that we can visit the results of multiple dataflow analyses simultaneously. /// DO NOT IMPLEMENT MANUALLY. Instead, use the `impl_visitable` macro below. pub trait ResultsVisitable<'tcx> { + type Direction: Direction; type FlowState; /// Creates an empty `FlowState` to hold the transient state for these dataflow results. /// - /// The value of the newly created `FlowState` will be overwritten by `reset_to_block_start` + /// The value of the newly created `FlowState` will be overwritten by `reset_to_block_entry` /// before it can be observed by a `ResultsVisitor`. fn new_flow_state(&self, body: &mir::Body<'tcx>) -> Self::FlowState; - fn reset_to_block_start(&self, state: &mut Self::FlowState, block: BasicBlock); + fn reset_to_block_entry(&self, state: &mut Self::FlowState, block: BasicBlock); fn reconstruct_before_statement_effect( &self, @@ -135,11 +135,13 @@ impl<'tcx, A> ResultsVisitable<'tcx> for Results<'tcx, A> { type FlowState = BitSet; + type Direction = A::Direction; + fn new_flow_state(&self, body: &mir::Body<'tcx>) -> Self::FlowState { BitSet::new_empty(self.analysis.bits_per_block(body)) } - fn reset_to_block_start(&self, state: &mut Self::FlowState, block: BasicBlock) { + fn reset_to_block_entry(&self, state: &mut Self::FlowState, block: BasicBlock) { state.overwrite(&self.entry_set_for_block(block)); } @@ -204,10 +206,11 @@ pub struct BorrowckAnalyses { ( $( $T:ident { $( $field:ident : $A:ident ),* $(,)? } )* ) => { $( - impl<'tcx, $($A),*> ResultsVisitable<'tcx> for $T<$( Results<'tcx, $A> ),*> + impl<'tcx, $($A),*, D: Direction> ResultsVisitable<'tcx> for $T<$( Results<'tcx, $A> ),*> where - $( $A: Analysis<'tcx>, )* + $( $A: Analysis<'tcx, Direction = D>, )* { + type Direction = D; type FlowState = $T<$( BitSet<$A::Idx> ),*>; fn new_flow_state(&self, body: &mir::Body<'tcx>) -> Self::FlowState { @@ -216,12 +219,12 @@ fn new_flow_state(&self, body: &mir::Body<'tcx>) -> Self::FlowState { } } - fn reset_to_block_start( + fn reset_to_block_entry( &self, state: &mut Self::FlowState, block: BasicBlock, ) { - $( state.$field.overwrite(&self.$field.entry_sets[block]); )* + $( state.$field.overwrite(&self.$field.entry_set_for_block(block)); )* } fn reconstruct_before_statement_effect( diff --git a/src/librustc_mir/dataflow/impls/storage_liveness.rs b/src/librustc_mir/dataflow/impls/storage_liveness.rs index 5d130213e1f..4c784c3f1a1 100644 --- a/src/librustc_mir/dataflow/impls/storage_liveness.rs +++ b/src/librustc_mir/dataflow/impls/storage_liveness.rs @@ -250,7 +250,7 @@ fn call_return_effect( fn yield_resume_effect( &self, - trans: &mut BitSet, + trans: &mut impl GenKill, _resume_block: BasicBlock, resume_place: mir::Place<'tcx>, ) { @@ -283,7 +283,7 @@ impl<'a, 'mir, 'tcx, T> Visitor<'tcx> for MoveVisitor<'a, 'mir, 'tcx, T> fn visit_local(&mut self, local: &Local, context: PlaceContext, loc: Location) { if PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) == context { let mut borrowed_locals = self.borrowed_locals.borrow_mut(); - borrowed_locals.seek_before(loc); + borrowed_locals.seek_before_primary_effect(loc); if !borrowed_locals.contains(*local) { self.trans.kill(*local); } diff --git a/src/librustc_mir/dataflow/mod.rs b/src/librustc_mir/dataflow/mod.rs index d244587fcc8..41b7821707c 100644 --- a/src/librustc_mir/dataflow/mod.rs +++ b/src/librustc_mir/dataflow/mod.rs @@ -4,8 +4,9 @@ pub(crate) use self::drop_flag_effects::*; pub use self::framework::{ - visit_results, Analysis, AnalysisDomain, BorrowckFlowState, BorrowckResults, BottomValue, - Engine, GenKill, GenKillAnalysis, Results, ResultsCursor, ResultsRefCursor, ResultsVisitor, + visit_results, Analysis, AnalysisDomain, Backward, BorrowckFlowState, BorrowckResults, + BottomValue, Engine, Forward, GenKill, GenKillAnalysis, Results, ResultsCursor, + ResultsRefCursor, ResultsVisitor, }; pub use self::impls::{ borrows::Borrows, DefinitelyInitializedPlaces, EverInitializedPlaces, MaybeBorrowedLocals, diff --git a/src/librustc_mir/lib.rs b/src/librustc_mir/lib.rs index ae7bbe9f36a..09f8588cee2 100644 --- a/src/librustc_mir/lib.rs +++ b/src/librustc_mir/lib.rs @@ -9,8 +9,9 @@ #![feature(bool_to_option)] #![feature(box_patterns)] #![feature(box_syntax)] -#![feature(const_if_match)] #![feature(const_fn)] +#![feature(const_if_match)] +#![feature(const_loop)] #![feature(const_panic)] #![feature(crate_visibility_modifier)] #![feature(decl_macro)] @@ -22,6 +23,7 @@ #![feature(trusted_len)] #![feature(try_blocks)] #![feature(associated_type_bounds)] +#![feature(associated_type_defaults)] #![feature(range_is_empty)] #![feature(stmt_expr_attributes)] #![feature(trait_alias)] diff --git a/src/librustc_mir/transform/check_consts/validation.rs b/src/librustc_mir/transform/check_consts/validation.rs index 78cb60ea484..24dc54294b7 100644 --- a/src/librustc_mir/transform/check_consts/validation.rs +++ b/src/librustc_mir/transform/check_consts/validation.rs @@ -61,7 +61,7 @@ fn indirectly_mutable( .into_results_cursor(&body) }); - indirectly_mutable.seek_before(location); + indirectly_mutable.seek_before_primary_effect(location); indirectly_mutable.get().contains(local) } @@ -88,7 +88,7 @@ fn needs_drop( .into_results_cursor(&body) }); - needs_drop.seek_before(location); + needs_drop.seek_before_primary_effect(location); needs_drop.get().contains(local) || self.indirectly_mutable(ccx, local, location) } @@ -115,7 +115,7 @@ fn has_mut_interior( .into_results_cursor(&body) }); - has_mut_interior.seek_before(location); + has_mut_interior.seek_before_primary_effect(location); has_mut_interior.get().contains(local) || self.indirectly_mutable(ccx, local, location) } diff --git a/src/librustc_mir/transform/elaborate_drops.rs b/src/librustc_mir/transform/elaborate_drops.rs index 6074619dd15..a1becf062ee 100644 --- a/src/librustc_mir/transform/elaborate_drops.rs +++ b/src/librustc_mir/transform/elaborate_drops.rs @@ -101,7 +101,7 @@ fn find_dead_unwinds<'tcx>( } }; - flow_inits.seek_before(body.terminator_loc(bb)); + flow_inits.seek_before_primary_effect(body.terminator_loc(bb)); debug!( "find_dead_unwinds @ {:?}: path({:?})={:?}; init_data={:?}", bb, @@ -131,8 +131,8 @@ struct InitializationData<'mir, 'tcx> { impl InitializationData<'_, '_> { fn seek_before(&mut self, loc: Location) { - self.inits.seek_before(loc); - self.uninits.seek_before(loc); + self.inits.seek_before_primary_effect(loc); + self.uninits.seek_before_primary_effect(loc); } fn maybe_live_dead(&self, path: MovePathIndex) -> (bool, bool) { diff --git a/src/librustc_mir/transform/generator.rs b/src/librustc_mir/transform/generator.rs index 24b77a7fdd6..a95c5bce5b1 100644 --- a/src/librustc_mir/transform/generator.rs +++ b/src/librustc_mir/transform/generator.rs @@ -490,21 +490,16 @@ fn locals_live_across_suspend_points( // If a borrow is converted to a raw reference, we must also assume that it lives // forever. Note that the final liveness is still bounded by the storage liveness // of the local, which happens using the `intersect` operation below. - borrowed_locals_cursor.seek_before(loc); + borrowed_locals_cursor.seek_before_primary_effect(loc); liveness.outs[block].union(borrowed_locals_cursor.get()); } - storage_live.seek_before(loc); - let mut storage_liveness = storage_live.get().clone(); - - // Later passes handle the generator's `self` argument separately. - storage_liveness.remove(SELF_ARG); - // Store the storage liveness for later use so we can restore the state // after a suspension point - storage_liveness_map[block] = Some(storage_liveness); + storage_live.seek_before_primary_effect(loc); + storage_liveness_map[block] = Some(storage_live.get().clone()); - requires_storage_cursor.seek_before(loc); + requires_storage_cursor.seek_before_primary_effect(loc); let storage_required = requires_storage_cursor.get().clone(); // Locals live are live at this point only if they are used across diff --git a/src/librustc_mir/transform/rustc_peek.rs b/src/librustc_mir/transform/rustc_peek.rs index b9302d58cd5..1beecb42c0b 100644 --- a/src/librustc_mir/transform/rustc_peek.rs +++ b/src/librustc_mir/transform/rustc_peek.rs @@ -126,7 +126,7 @@ pub fn sanity_check_via_rustc_peek<'tcx, A>( mir::Rvalue::Use(mir::Operand::Move(place) | mir::Operand::Copy(place)), ) => { let loc = Location { block: bb, statement_index }; - cursor.seek_before(loc); + cursor.seek_before_primary_effect(loc); let state = cursor.get(); results.analysis.peek_at(tcx, *place, state, call); } -- GitLab