refactor access fact generation

- use consistent names
- inline single use functions
- dedupe and simplify some paths
- fix fact generation timer activity: it was missing the walk and
  extraction process

Author: lqd

compiler/rustc_borrowck/src/type_check/liveness/mod.rs

@@ -45,7 +45,7 @@ pub(super) fn generate<'a, 'tcx>(
     let (relevant_live_locals, boring_locals) =
         compute_relevant_live_locals(typeck.tcx(), &free_regions, body);
 
-    polonius::populate_access_facts(typeck, body, move_data);
+    polonius::emit_access_facts(typeck, body, move_data);
 
     trace::trace(
         typeck,

compiler/rustc_borrowck/src/type_check/liveness/polonius.rs

@@ -11,88 +11,19 @@ use crate::location::{LocationIndex, LocationTable};
 type VarPointRelation = Vec<(Local, LocationIndex)>;
 type PathPointRelation = Vec<(MovePathIndex, LocationIndex)>;
 
-struct UseFactsExtractor<'a, 'tcx> {
-    var_defined_at: &'a mut VarPointRelation,
-    var_used_at: &'a mut VarPointRelation,
-    location_table: &'a LocationTable,
-    var_dropped_at: &'a mut VarPointRelation,
-    move_data: &'a MoveData<'tcx>,
-    path_accessed_at_base: &'a mut PathPointRelation,
-}
-
-// A Visitor to walk through the MIR and extract point-wise facts
-impl<'tcx> UseFactsExtractor<'_, 'tcx> {
-    fn location_to_index(&self, location: Location) -> LocationIndex {
-        self.location_table.mid_index(location)
-    }
-
-    fn insert_def(&mut self, local: Local, location: Location) {
-        debug!("UseFactsExtractor::insert_def()");
-        self.var_defined_at.push((local, self.location_to_index(location)));
-    }
-
-    fn insert_use(&mut self, local: Local, location: Location) {
-        debug!("UseFactsExtractor::insert_use()");
-        self.var_used_at.push((local, self.location_to_index(location)));
-    }
-
-    fn insert_drop_use(&mut self, local: Local, location: Location) {
-        debug!("UseFactsExtractor::insert_drop_use()");
-        self.var_dropped_at.push((local, self.location_to_index(location)));
-    }
-
-    fn insert_path_access(&mut self, path: MovePathIndex, location: Location) {
-        debug!("UseFactsExtractor::insert_path_access({:?}, {:?})", path, location);
-        self.path_accessed_at_base.push((path, self.location_to_index(location)));
-    }
-
-    fn place_to_mpi(&self, place: &Place<'tcx>) -> Option<MovePathIndex> {
-        match self.move_data.rev_lookup.find(place.as_ref()) {
-            LookupResult::Exact(mpi) => Some(mpi),
-            LookupResult::Parent(mmpi) => mmpi,
-        }
-    }
-}
-
-impl<'a, 'tcx> Visitor<'tcx> for UseFactsExtractor<'a, 'tcx> {
-    fn visit_local(&mut self, local: Local, context: PlaceContext, location: Location) {
-        match def_use::categorize(context) {
-            Some(DefUse::Def) => self.insert_def(local, location),
-            Some(DefUse::Use) => self.insert_use(local, location),
-            Some(DefUse::Drop) => self.insert_drop_use(local, location),
-            _ => (),
-        }
-    }
-
-    fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
-        self.super_place(place, context, location);
-        match context {
-            PlaceContext::NonMutatingUse(_) => {
-                if let Some(mpi) = self.place_to_mpi(place) {
-                    self.insert_path_access(mpi, location);
-                }
-            }
-
-            PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
-                if let Some(mpi) = self.place_to_mpi(place) {
-                    self.insert_path_access(mpi, location);
-                }
-            }
-            _ => (),
-        }
-    }
-}
-
-pub(super) fn populate_access_facts<'a, 'tcx>(
+/// Emit polonius facts for variable defs, uses, drops, and path accesses.
+pub(super) fn emit_access_facts<'a, 'tcx>(
     typeck: &mut TypeChecker<'a, 'tcx>,
     body: &Body<'tcx>,
     move_data: &MoveData<'tcx>,
 ) {
     if let Some(facts) = typeck.all_facts.as_mut() {
-        debug!("populate_access_facts()");
+        debug!("emit_access_facts()");
+
+        let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
         let location_table = typeck.location_table;
 
-        let mut extractor = UseFactsExtractor {
+        let mut extractor = AccessFactsExtractor {
             var_defined_at: &mut facts.var_defined_at,
             var_used_at: &mut facts.var_used_at,
             var_dropped_at: &mut facts.var_dropped_at,
@@ -107,7 +38,6 @@ pub(super) fn populate_access_facts<'a, 'tcx>(
                 "add use_of_var_derefs_origin facts - local={:?}, type={:?}",
                 local, local_decl.ty
             );
-            let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
             let universal_regions = &typeck.universal_regions;
             typeck.infcx.tcx.for_each_free_region(&local_decl.ty, |region| {
                 let region_vid = universal_regions.to_region_vid(region);
@@ -119,12 +49,12 @@ pub(super) fn populate_access_facts<'a, 'tcx>(
 
 /// For every potentially drop()-touched region `region` in `local`'s type
 /// (`kind`), emit a Polonius `use_of_var_derefs_origin(local, origin)` fact.
-pub(super) fn add_drop_of_var_derefs_origin<'tcx>(
+pub(super) fn emit_drop_facts<'tcx>(
     typeck: &mut TypeChecker<'_, 'tcx>,
     local: Local,
     kind: &GenericArg<'tcx>,
 ) {
-    debug!("add_drop_of_var_derefs_origin(local={:?}, kind={:?}", local, kind);
+    debug!("emit_drop_facts(local={:?}, kind={:?}", local, kind);
     if let Some(facts) = typeck.all_facts.as_mut() {
         let _prof_timer = typeck.infcx.tcx.prof.generic_activity("polonius_fact_generation");
         let universal_regions = &typeck.universal_regions;
@@ -134,3 +64,60 @@ pub(super) fn add_drop_of_var_derefs_origin<'tcx>(
         });
     }
 }
+
+/// MIR visitor extracting point-wise facts about accesses.
+struct AccessFactsExtractor<'a, 'tcx> {
+    var_defined_at: &'a mut VarPointRelation,
+    var_used_at: &'a mut VarPointRelation,
+    location_table: &'a LocationTable,
+    var_dropped_at: &'a mut VarPointRelation,
+    move_data: &'a MoveData<'tcx>,
+    path_accessed_at_base: &'a mut PathPointRelation,
+}
+
+impl<'tcx> AccessFactsExtractor<'_, 'tcx> {
+    fn location_to_index(&self, location: Location) -> LocationIndex {
+        self.location_table.mid_index(location)
+    }
+}
+
+impl<'a, 'tcx> Visitor<'tcx> for AccessFactsExtractor<'a, 'tcx> {
+    fn visit_local(&mut self, local: Local, context: PlaceContext, location: Location) {
+        match def_use::categorize(context) {
+            Some(DefUse::Def) => {
+                debug!("AccessFactsExtractor - emit def");
+                self.var_defined_at.push((local, self.location_to_index(location)));
+            }
+            Some(DefUse::Use) => {
+                debug!("AccessFactsExtractor - emit use");
+                self.var_used_at.push((local, self.location_to_index(location)));
+            }
+            Some(DefUse::Drop) => {
+                debug!("AccessFactsExtractor - emit drop");
+                self.var_dropped_at.push((local, self.location_to_index(location)));
+            }
+            _ => (),
+        }
+    }
+
+    fn visit_place(&mut self, place: &Place<'tcx>, context: PlaceContext, location: Location) {
+        self.super_place(place, context, location);
+
+        match context {
+            PlaceContext::NonMutatingUse(_)
+            | PlaceContext::MutatingUse(MutatingUseContext::Borrow) => {
+                let path = match self.move_data.rev_lookup.find(place.as_ref()) {
+                    LookupResult::Exact(path) | LookupResult::Parent(Some(path)) => path,
+                    _ => {
+                        // There's no path access to emit.
+                        return;
+                    }
+                };
+                debug!("AccessFactsExtractor - emit path access ({path:?}, {location:?})");
+                self.path_accessed_at_base.push((path, self.location_to_index(location)));
+            }
+
+            _ => {}
+        }
+    }
+}

compiler/rustc_borrowck/src/type_check/liveness/trace.rs

@@ -590,7 +590,7 @@ impl<'tcx> LivenessContext<'_, '_, '_, 'tcx> {
         // the destructor and must be live at this point.
         for &kind in &drop_data.dropck_result.kinds {
             Self::make_all_regions_live(self.elements, self.typeck, kind, live_at);
-            polonius::add_drop_of_var_derefs_origin(self.typeck, dropped_local, &kind);
+            polonius::emit_drop_facts(self.typeck, dropped_local, &kind);
         }
     }