diff options
Diffstat (limited to 'compiler/rustc_mir_transform/src')
| -rw-r--r-- | compiler/rustc_mir_transform/src/elaborate_drops.rs | 57 |
1 files changed, 39 insertions, 18 deletions
diff --git a/compiler/rustc_mir_transform/src/elaborate_drops.rs b/compiler/rustc_mir_transform/src/elaborate_drops.rs index c2ff8645635..bdfd8dc6e99 100644 --- a/compiler/rustc_mir_transform/src/elaborate_drops.rs +++ b/compiler/rustc_mir_transform/src/elaborate_drops.rs @@ -67,13 +67,11 @@ impl<'tcx> MirPass<'tcx> for ElaborateDrops { }; let un_derefer = UnDerefer { tcx: tcx, derefer_sidetable: side_table }; let elaborate_patch = { - let body = &*body; let env = MoveDataParamEnv { move_data, param_env }; - let dead_unwinds = find_dead_unwinds(tcx, body, &env, &un_derefer); + remove_dead_unwinds(tcx, body, &env, &un_derefer); let inits = MaybeInitializedPlaces::new(tcx, body, &env) .into_engine(tcx, body) - .dead_unwinds(&dead_unwinds) .pass_name("elaborate_drops") .iterate_to_fixpoint() .into_results_cursor(body); @@ -81,11 +79,12 @@ impl<'tcx> MirPass<'tcx> for ElaborateDrops { let uninits = MaybeUninitializedPlaces::new(tcx, body, &env) .mark_inactive_variants_as_uninit() .into_engine(tcx, body) - .dead_unwinds(&dead_unwinds) .pass_name("elaborate_drops") .iterate_to_fixpoint() .into_results_cursor(body); + let reachable = traversal::reachable_as_bitset(body); + ElaborateDropsCtxt { tcx, body, @@ -94,6 +93,7 @@ impl<'tcx> MirPass<'tcx> for ElaborateDrops { drop_flags: Default::default(), patch: MirPatch::new(body), un_derefer: un_derefer, + reachable, } .elaborate() }; @@ -102,22 +102,21 @@ impl<'tcx> MirPass<'tcx> for ElaborateDrops { } } -/// Returns the set of basic blocks whose unwind edges are known -/// to not be reachable, because they are `drop` terminators +/// Removes unwind edges which are known to be unreachable, because they are in `drop` terminators /// that can't drop anything. -fn find_dead_unwinds<'tcx>( +fn remove_dead_unwinds<'tcx>( tcx: TyCtxt<'tcx>, - body: &Body<'tcx>, + body: &mut Body<'tcx>, env: &MoveDataParamEnv<'tcx>, und: &UnDerefer<'tcx>, -) -> BitSet<BasicBlock> { - debug!("find_dead_unwinds({:?})", body.span); +) { + debug!("remove_dead_unwinds({:?})", body.span); // We only need to do this pass once, because unwind edges can only // reach cleanup blocks, which can't have unwind edges themselves. - let mut dead_unwinds = BitSet::new_empty(body.basic_blocks.len()); + let mut dead_unwinds = Vec::new(); let mut flow_inits = MaybeInitializedPlaces::new(tcx, body, &env) .into_engine(tcx, body) - .pass_name("find_dead_unwinds") + .pass_name("remove_dead_unwinds") .iterate_to_fixpoint() .into_results_cursor(body); for (bb, bb_data) in body.basic_blocks.iter_enumerated() { @@ -129,16 +128,16 @@ fn find_dead_unwinds<'tcx>( _ => continue, }; - debug!("find_dead_unwinds @ {:?}: {:?}", bb, bb_data); + debug!("remove_dead_unwinds @ {:?}: {:?}", bb, bb_data); let LookupResult::Exact(path) = env.move_data.rev_lookup.find(place.as_ref()) else { - debug!("find_dead_unwinds: has parent; skipping"); + debug!("remove_dead_unwinds: has parent; skipping"); continue; }; flow_inits.seek_before_primary_effect(body.terminator_loc(bb)); debug!( - "find_dead_unwinds @ {:?}: path({:?})={:?}; init_data={:?}", + "remove_dead_unwinds @ {:?}: path({:?})={:?}; init_data={:?}", bb, place, path, @@ -150,13 +149,22 @@ fn find_dead_unwinds<'tcx>( maybe_live |= flow_inits.contains(child); }); - debug!("find_dead_unwinds @ {:?}: maybe_live={}", bb, maybe_live); + debug!("remove_dead_unwinds @ {:?}: maybe_live={}", bb, maybe_live); if !maybe_live { - dead_unwinds.insert(bb); + dead_unwinds.push(bb); } } - dead_unwinds + if dead_unwinds.is_empty() { + return; + } + + let basic_blocks = body.basic_blocks.as_mut(); + for &bb in dead_unwinds.iter() { + if let Some(unwind) = basic_blocks[bb].terminator_mut().unwind_mut() { + *unwind = None; + } + } } struct InitializationData<'mir, 'tcx> { @@ -290,6 +298,7 @@ struct ElaborateDropsCtxt<'a, 'tcx> { drop_flags: FxHashMap<MovePathIndex, Local>, patch: MirPatch<'tcx>, un_derefer: UnDerefer<'tcx>, + reachable: BitSet<BasicBlock>, } impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> { @@ -329,6 +338,9 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> { fn collect_drop_flags(&mut self) { for (bb, data) in self.body.basic_blocks.iter_enumerated() { + if !self.reachable.contains(bb) { + continue; + } let terminator = data.terminator(); let place = match terminator.kind { TerminatorKind::Drop { ref place, .. } @@ -384,6 +396,9 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> { fn elaborate_drops(&mut self) { for (bb, data) in self.body.basic_blocks.iter_enumerated() { + if !self.reachable.contains(bb) { + continue; + } let loc = Location { block: bb, statement_index: data.statements.len() }; let terminator = data.terminator(); @@ -541,6 +556,9 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> { fn drop_flags_for_fn_rets(&mut self) { for (bb, data) in self.body.basic_blocks.iter_enumerated() { + if !self.reachable.contains(bb) { + continue; + } if let TerminatorKind::Call { destination, target: Some(tgt), cleanup: Some(_), .. } = data.terminator().kind @@ -576,6 +594,9 @@ impl<'b, 'tcx> ElaborateDropsCtxt<'b, 'tcx> { // clobbered before they are read. for (bb, data) in self.body.basic_blocks.iter_enumerated() { + if !self.reachable.contains(bb) { + continue; + } debug!("drop_flags_for_locs({:?})", data); for i in 0..(data.statements.len() + 1) { debug!("drop_flag_for_locs: stmt {}", i); |