diff options
Diffstat (limited to 'compiler/rustc_borrowck/src/type_check/liveness/mod.rs')
-rw-r--r-- | compiler/rustc_borrowck/src/type_check/liveness/mod.rs | 88 |
1 files changed, 83 insertions, 5 deletions
diff --git a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs index f1ad0ca55..dc4695fd2 100644 --- a/compiler/rustc_borrowck/src/type_check/liveness/mod.rs +++ b/compiler/rustc_borrowck/src/type_check/liveness/mod.rs @@ -1,7 +1,9 @@ use itertools::{Either, Itertools}; use rustc_data_structures::fx::FxHashSet; -use rustc_middle::mir::{Body, Local}; -use rustc_middle::ty::{RegionVid, TyCtxt}; +use rustc_middle::mir::visit::{TyContext, Visitor}; +use rustc_middle::mir::{Body, Local, Location, SourceInfo}; +use rustc_middle::ty::visit::TypeVisitable; +use rustc_middle::ty::{GenericArgsRef, Region, RegionVid, Ty, TyCtxt}; use rustc_mir_dataflow::impls::MaybeInitializedPlaces; use rustc_mir_dataflow::move_paths::MoveData; use rustc_mir_dataflow::ResultsCursor; @@ -11,7 +13,7 @@ use crate::{ constraints::OutlivesConstraintSet, facts::{AllFacts, AllFactsExt}, location::LocationTable, - region_infer::values::RegionValueElements, + region_infer::values::{LivenessValues, RegionValueElements}, universal_regions::UniversalRegions, }; @@ -42,11 +44,11 @@ pub(super) fn generate<'mir, 'tcx>( let free_regions = regions_that_outlive_free_regions( typeck.infcx.num_region_vars(), - &typeck.borrowck_context.universal_regions, + typeck.borrowck_context.universal_regions, &typeck.borrowck_context.constraints.outlives_constraints, ); let (relevant_live_locals, boring_locals) = - compute_relevant_live_locals(typeck.tcx(), &free_regions, &body); + compute_relevant_live_locals(typeck.tcx(), &free_regions, body); let facts_enabled = use_polonius || AllFacts::enabled(typeck.tcx()); let polonius_drop_used = facts_enabled.then(|| { @@ -65,6 +67,14 @@ pub(super) fn generate<'mir, 'tcx>( boring_locals, polonius_drop_used, ); + + // Mark regions that should be live where they appear within rvalues or within a call: like + // args, regions, and types. + record_regular_live_regions( + typeck.tcx(), + &mut typeck.borrowck_context.constraints.liveness_constraints, + body, + ); } // The purpose of `compute_relevant_live_locals` is to define the subset of `Local` @@ -132,3 +142,71 @@ fn regions_that_outlive_free_regions<'tcx>( // Return the final set of things we visited. outlives_free_region } + +/// Some variables are "regular live" at `location` -- i.e., they may be used later. This means that +/// all regions appearing in their type must be live at `location`. +fn record_regular_live_regions<'tcx>( + tcx: TyCtxt<'tcx>, + liveness_constraints: &mut LivenessValues, + body: &Body<'tcx>, +) { + let mut visitor = LiveVariablesVisitor { tcx, liveness_constraints }; + for (bb, data) in body.basic_blocks.iter_enumerated() { + visitor.visit_basic_block_data(bb, data); + } +} + +/// Visitor looking for regions that should be live within rvalues or calls. +struct LiveVariablesVisitor<'cx, 'tcx> { + tcx: TyCtxt<'tcx>, + liveness_constraints: &'cx mut LivenessValues, +} + +impl<'cx, 'tcx> Visitor<'tcx> for LiveVariablesVisitor<'cx, 'tcx> { + /// We sometimes have `args` within an rvalue, or within a + /// call. Make them live at the location where they appear. + fn visit_args(&mut self, args: &GenericArgsRef<'tcx>, location: Location) { + self.record_regions_live_at(*args, location); + self.super_args(args); + } + + /// We sometimes have `region`s within an rvalue, or within a + /// call. Make them live at the location where they appear. + fn visit_region(&mut self, region: Region<'tcx>, location: Location) { + self.record_regions_live_at(region, location); + self.super_region(region); + } + + /// We sometimes have `ty`s within an rvalue, or within a + /// call. Make them live at the location where they appear. + fn visit_ty(&mut self, ty: Ty<'tcx>, ty_context: TyContext) { + match ty_context { + TyContext::ReturnTy(SourceInfo { span, .. }) + | TyContext::YieldTy(SourceInfo { span, .. }) + | TyContext::UserTy(span) + | TyContext::LocalDecl { source_info: SourceInfo { span, .. }, .. } => { + span_bug!(span, "should not be visiting outside of the CFG: {:?}", ty_context); + } + TyContext::Location(location) => { + self.record_regions_live_at(ty, location); + } + } + + self.super_ty(ty); + } +} + +impl<'cx, 'tcx> LiveVariablesVisitor<'cx, 'tcx> { + /// Some variable is "regular live" at `location` -- i.e., it may be used later. This means that + /// all regions appearing in the type of `value` must be live at `location`. + fn record_regions_live_at<T>(&mut self, value: T, location: Location) + where + T: TypeVisitable<TyCtxt<'tcx>>, + { + debug!("record_regions_live_at(value={:?}, location={:?})", value, location); + self.tcx.for_each_free_region(&value, |live_region| { + let live_region_vid = live_region.as_var(); + self.liveness_constraints.add_location(live_region_vid, location); + }); + } +} |