src/librustc_mir/borrow_check/type_check/liveness/polonius.rs

   1 use crate::borrow_check::location::{LocationIndex, LocationTable};
   2 use crate::dataflow::indexes::MovePathIndex;
   3 use crate::dataflow::move_paths::{LookupResult, MoveData};
   4 use crate::util::liveness::{categorize, DefUse};
   5 use rustc::mir::visit::{MutatingUseContext, PlaceContext, Visitor};
   6 use rustc::mir::{Local, Location, Place, ReadOnlyBodyAndCache};
   7 use rustc::ty::subst::GenericArg;
   8
   9 use super::TypeChecker;
  10
  11 type VarPointRelation = Vec<(Local, LocationIndex)>;
  12 type PathPointRelation = Vec<(MovePathIndex, LocationIndex)>;
  13
  14 struct UseFactsExtractor<'me> {
  15     var_defined_at: &'me mut VarPointRelation,
  16     var_used_at: &'me mut VarPointRelation,
  17     location_table: &'me LocationTable,
  18     var_dropped_at: &'me mut VarPointRelation,
  19     move_data: &'me MoveData<'me>,
  20     path_accessed_at_base: &'me mut PathPointRelation,
  21 }
  22
  23 // A Visitor to walk through the MIR and extract point-wise facts
  24 impl UseFactsExtractor<'_> {
  25     fn location_to_index(&self, location: Location) -> LocationIndex {
  26         self.location_table.mid_index(location)
  27     }
  28
  29     fn insert_def(&mut self, local: Local, location: Location) {
  30         debug!("UseFactsExtractor::insert_def()");
  31         self.var_defined_at.push((local, self.location_to_index(location)));
  32     }
  33
  34     fn insert_use(&mut self, local: Local, location: Location) {
  35         debug!("UseFactsExtractor::insert_use()");
  36         self.var_used_at.push((local, self.location_to_index(location)));
  37     }
  38
  39     fn insert_drop_use(&mut self, local: Local, location: Location) {
  40         debug!("UseFactsExtractor::insert_drop_use()");
  41         self.var_dropped_at.push((local, self.location_to_index(location)));
  42     }
  43
  44     fn insert_path_access(&mut self, path: MovePathIndex, location: Location) {
  45         debug!("UseFactsExtractor::insert_path_access({:?}, {:?})", path, location);
  46         self.path_accessed_at_base.push((path, self.location_table.start_index(location)));
  47     }
  48
  49     fn place_to_mpi(&self, place: &Place<'_>) -> Option<MovePathIndex> {
  50         match self.move_data.rev_lookup.find(place.as_ref()) {
  51             LookupResult::Exact(mpi) => Some(mpi),
  52             LookupResult::Parent(mmpi) => mmpi,
  53         }
  54     }
  55 }
  56
  57 impl Visitor<'tcx> for UseFactsExtractor<'_> {
  58     fn visit_local(&mut self, &local: &Local, context: PlaceContext, location: Location) {
  59         match categorize(context) {
  60             Some(DefUse::Def) => self.insert_def(local, location),
  61             Some(DefUse::Use) => self.insert_use(local, location),
  62             Some(DefUse::Drop) => self.insert_drop_use(local, location),
  63             _ => (),
  64         }
  65     }
  66
  67     fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
  68         self.super_place(place, context, location);
  69         match context {
  70             PlaceContext::NonMutatingUse(_) => {
  71                 if let Some(mpi) = self.place_to_mpi(place) {
  72                     self.insert_path_access(mpi, location);
  73                 }
  74             }
  75
  76             PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
  77                 if let Some(mpi) = self.place_to_mpi(place) {
  78                     self.insert_path_access(mpi, location);
  79                 }
  80             }
  81             _ => (),
  82         }
  83     }
  84 }
  85
  86 pub(super) fn populate_access_facts(
  87     typeck: &mut TypeChecker<'_, 'tcx>,
  88     body: ReadOnlyBodyAndCache<'_, 'tcx>,
  89     location_table: &LocationTable,
  90     move_data: &MoveData<'_>,
  91     dropped_at: &mut Vec<(Local, Location)>,
  92 ) {
  93     debug!("populate_access_facts()");
  94
  95     if let Some(facts) = typeck.borrowck_context.all_facts.as_mut() {
  96         let mut extractor = UseFactsExtractor {
  97             var_defined_at: &mut facts.var_defined_at,
  98             var_used_at: &mut facts.var_used_at,
  99             var_dropped_at: &mut facts.var_dropped_at,
 100             path_accessed_at_base: &mut facts.path_accessed_at_base,
 101             location_table,
 102             move_data,
 103         };
 104         extractor.visit_body(body);
 105
 106         facts.var_dropped_at.extend(
 107             dropped_at.iter().map(|&(local, location)| (local, location_table.mid_index(location))),
 108         );
 109
 110         for (local, local_decl) in body.local_decls.iter_enumerated() {
 111             debug!(
 112                 "add use_of_var_derefs_origin facts - local={:?}, type={:?}",
 113                 local, local_decl.ty
 114             );
 115             let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
 116             let universal_regions = &typeck.borrowck_context.universal_regions;
 117             typeck.infcx.tcx.for_each_free_region(&local_decl.ty, |region| {
 118                 let region_vid = universal_regions.to_region_vid(region);
 119                 facts.use_of_var_derefs_origin.push((local, region_vid));
 120             });
 121         }
 122     }
 123 }
 124
 125 // For every potentially drop()-touched region `region` in `local`'s type
 126 // (`kind`), emit a Polonius `use_of_var_derefs_origin(local, origin)` fact.
 127 pub(super) fn add_drop_of_var_derefs_origin(
 128     typeck: &mut TypeChecker<'_, 'tcx>,
 129     local: Local,
 130     kind: &GenericArg<'tcx>,
 131 ) {
 132     debug!("add_drop_of_var_derefs_origin(local={:?}, kind={:?}", local, kind);
 133     if let Some(facts) = typeck.borrowck_context.all_facts.as_mut() {
 134         let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
 135         let universal_regions = &typeck.borrowck_context.universal_regions;
 136         typeck.infcx.tcx.for_each_free_region(kind, |drop_live_region| {
 137             let region_vid = universal_regions.to_region_vid(drop_live_region);
 138             facts.drop_of_var_derefs_origin.push((local, region_vid));
 139         });
 140     }
 141 }