nll: remove NllLivenessMap and LiveVar
Extract the `compute` logic (now renamed `compute_live_locals`) from `NllLivenessMap` to the `liveness` module. Remove the unused structures.
This commit is contained in:
Lucas Molas
parent
4ae4e0501b
commit
d6ede9192d
4 changed files with 71 additions and 117 deletions
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@ -2,7 +2,6 @@ use crate::borrow_check::borrow_set::BorrowSet;
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use crate::borrow_check::location::{LocationIndex, LocationTable};
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use crate::borrow_check::nll::facts::AllFactsExt;
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use crate::borrow_check::nll::type_check::{MirTypeckResults, MirTypeckRegionConstraints};
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use crate::borrow_check::nll::type_check::liveness::liveness_map::NllLivenessMap;
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use crate::borrow_check::nll::region_infer::values::RegionValueElements;
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use crate::dataflow::indexes::BorrowIndex;
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use crate::dataflow::move_paths::MoveData;
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@ -1,94 +0,0 @@
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//! For the NLL computation, we need to compute liveness, but only for those
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//! local variables whose types contain regions. The others are not of interest
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//! to us. This file defines a new index type (LiveVar) that indexes into
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//! a list of "variables whose type contain regions". It also defines a map from
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//! Local to LiveVar and vice versa -- this map can be given to the
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//! liveness code so that it only operates over variables with regions in their
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//! types, instead of all variables.
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use crate::borrow_check::nll::ToRegionVid;
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use crate::borrow_check::nll::facts::{AllFacts, AllFactsExt};
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use crate::util::liveness::LiveVariableMap;
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use rustc::mir::{Local, Mir};
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use rustc::ty::{RegionVid, TyCtxt};
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use rustc_data_structures::fx::FxHashSet;
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use rustc_data_structures::indexed_vec::{Idx, IndexVec};
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/// Map between Local and LiveVar indices: the purpose of this
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/// map is to define the subset of local variables for which we need
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/// to do a liveness computation. We only need to compute whether a
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/// variable `X` is live if that variable contains some region `R` in
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/// its type where `R` is not known to outlive a free region (i.e.,
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/// where `R` may be valid for just a subset of the fn body).
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crate struct NllLivenessMap {
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/// For each local variable, contains `Some(i)` if liveness is
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/// needed for this variable.
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pub from_local: IndexVec<Local, Option<LiveVar>>,
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/// For each `LiveVar`, maps back to the original `Local` index.
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pub to_local: IndexVec<LiveVar, Local>,
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}
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impl LiveVariableMap for NllLivenessMap {
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fn from_local(&self, local: Local) -> Option<Self::LiveVar> {
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self.from_local[local]
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}
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type LiveVar = LiveVar;
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fn from_live_var(&self, local: Self::LiveVar) -> Local {
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self.to_local[local]
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}
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fn num_variables(&self) -> usize {
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self.to_local.len()
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}
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}
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impl NllLivenessMap {
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crate fn compute(
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tcx: TyCtxt<'_, '_, 'tcx>,
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free_regions: &FxHashSet<RegionVid>,
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mir: &Mir<'tcx>,
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) -> Self {
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let mut to_local = IndexVec::default();
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let facts_enabled = AllFacts::enabled(tcx);
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let from_local: IndexVec<Local, Option<_>> = mir.local_decls
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.iter_enumerated()
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.map(|(local, local_decl)| {
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if tcx.all_free_regions_meet(&local_decl.ty, |r| {
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free_regions.contains(&r.to_region_vid())
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}) && !facts_enabled {
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// If all the regions in the type are free regions
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// (or there are no regions), then we don't need
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// to track liveness for this variable.
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None
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} else {
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Some(to_local.push(local))
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}
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})
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.collect();
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debug!("{} total variables", mir.local_decls.len());
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debug!("{} variables need liveness", to_local.len());
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debug!("{} regions outlive free regions", free_regions.len());
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Self {
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from_local,
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to_local,
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}
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}
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/// Returns `true` if there are no local variables that need liveness computation.
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crate fn is_empty(&self) -> bool {
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self.to_local.is_empty()
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}
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}
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/// Index given to each local variable for which we need to
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/// compute liveness information. For many locals, we are able to
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/// skip liveness information: for example, those variables whose
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/// types contain no regions.
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newtype_index! {
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pub struct LiveVar { .. }
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}
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@ -1,19 +1,19 @@
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use crate::borrow_check::location::LocationTable;
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use crate::borrow_check::nll::region_infer::values::RegionValueElements;
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use crate::borrow_check::nll::constraints::ConstraintSet;
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use crate::borrow_check::nll::NllLivenessMap;
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use crate::borrow_check::nll::facts::{AllFacts, AllFactsExt};
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use crate::borrow_check::nll::region_infer::values::RegionValueElements;
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use crate::borrow_check::nll::universal_regions::UniversalRegions;
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use crate::borrow_check::nll::ToRegionVid;
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use crate::dataflow::move_paths::MoveData;
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use crate::dataflow::MaybeInitializedPlaces;
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use crate::dataflow::FlowAtLocation;
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use rustc::mir::Mir;
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use rustc::ty::RegionVid;
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use crate::dataflow::MaybeInitializedPlaces;
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use rustc::mir::{Local, Mir};
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use rustc::ty::{RegionVid, TyCtxt};
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use rustc_data_structures::fx::FxHashSet;
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use std::rc::Rc;
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use super::TypeChecker;
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crate mod liveness_map;
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mod local_use_map;
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mod trace;
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@ -34,16 +34,71 @@ pub(super) fn generate<'gcx, 'tcx>(
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location_table: &LocationTable,
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) {
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debug!("liveness::generate");
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let free_regions = {
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let borrowck_context = typeck.borrowck_context.as_ref().unwrap();
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regions_that_outlive_free_regions(
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typeck.infcx.num_region_vars(),
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&borrowck_context.universal_regions,
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&borrowck_context.constraints.outlives_constraints,
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)
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let live_locals: Vec<Local> = if AllFacts::enabled(typeck.tcx()) {
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// If "dump facts from NLL analysis" was requested perform
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// the liveness analysis for all `Local`s. This case opens
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// the possibility of the variables being analyzed in `trace`
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// to be *any* `Local`, not just the "live" ones, so we can't
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// make any assumptions past this point as to the characteristics
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// of the `live_locals`.
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// FIXME: Review "live" terminology past this point, we should
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// not be naming the `Local`s as live.
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mir.local_decls.indices().collect()
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} else {
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let free_regions = {
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let borrowck_context = typeck.borrowck_context.as_ref().unwrap();
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regions_that_outlive_free_regions(
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typeck.infcx.num_region_vars(),
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&borrowck_context.universal_regions,
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&borrowck_context.constraints.outlives_constraints,
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)
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};
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compute_live_locals(typeck.tcx(), &free_regions, mir)
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};
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let liveness_map = NllLivenessMap::compute(typeck.tcx(), &free_regions, mir);
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trace::trace(typeck, mir, elements, flow_inits, move_data, &liveness_map, location_table);
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if !live_locals.is_empty() {
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trace::trace(
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typeck,
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mir,
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elements,
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flow_inits,
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move_data,
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live_locals,
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location_table,
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);
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}
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}
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// The purpose of `compute_live_locals` is to define the subset of `Local`
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// variables for which we need to do a liveness computation. We only need
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// to compute whether a variable `X` is live if that variable contains
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// some region `R` in its type where `R` is not known to outlive a free
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// region (i.e., where `R` may be valid for just a subset of the fn body).
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fn compute_live_locals(
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tcx: TyCtxt<'_, '_, 'tcx>,
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free_regions: &FxHashSet<RegionVid>,
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mir: &Mir<'tcx>,
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) -> Vec<Local> {
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let live_locals: Vec<Local> = mir
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.local_decls
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.iter_enumerated()
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.filter_map(|(local, local_decl)| {
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if tcx.all_free_regions_meet(&local_decl.ty, |r| {
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free_regions.contains(&r.to_region_vid())
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}) {
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None
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} else {
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Some(local)
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}
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})
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.collect();
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debug!("{} total variables", mir.local_decls.len());
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debug!("{} variables need liveness", live_locals.len());
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debug!("{} regions outlive free regions", free_regions.len());
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live_locals
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}
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/// Computes all regions that are (currently) known to outlive free
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@ -1,6 +1,5 @@
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use crate::borrow_check::location::LocationTable;
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use crate::borrow_check::nll::region_infer::values::{self, PointIndex, RegionValueElements};
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use crate::borrow_check::nll::type_check::liveness::liveness_map::NllLivenessMap;
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use crate::borrow_check::nll::type_check::liveness::local_use_map::LocalUseMap;
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use crate::borrow_check::nll::type_check::NormalizeLocation;
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use crate::borrow_check::nll::type_check::TypeChecker;
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@ -37,16 +36,11 @@ pub(super) fn trace(
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elements: &Rc<RegionValueElements>,
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flow_inits: &mut FlowAtLocation<'tcx, MaybeInitializedPlaces<'_, 'gcx, 'tcx>>,
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move_data: &MoveData<'tcx>,
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liveness_map: &NllLivenessMap,
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live_locals: Vec<Local>,
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location_table: &LocationTable,
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) {
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debug!("trace()");
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if liveness_map.is_empty() {
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return;
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}
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let live_locals: Vec<Local> = liveness_map.to_local.clone().into_iter().collect();
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let local_use_map = &LocalUseMap::build(&live_locals, elements, mir);
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let cx = LivenessContext {
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