diff options
Diffstat (limited to 'compiler/rustc_mir_transform/src')
| -rw-r--r-- | compiler/rustc_mir_transform/src/copy_prop.rs | 34 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/ssa.rs | 23 |
2 files changed, 30 insertions, 27 deletions
diff --git a/compiler/rustc_mir_transform/src/copy_prop.rs b/compiler/rustc_mir_transform/src/copy_prop.rs index 27af5818982..fe78a104fa0 100644 --- a/compiler/rustc_mir_transform/src/copy_prop.rs +++ b/compiler/rustc_mir_transform/src/copy_prop.rs @@ -30,6 +30,8 @@ impl<'tcx> crate::MirPass<'tcx> for CopyProp { let typing_env = body.typing_env(tcx); let ssa = SsaLocals::new(tcx, body, typing_env); + debug!(borrowed_locals = ?ssa.borrowed_locals()); + debug!(copy_classes = ?ssa.copy_classes()); let fully_moved = fully_moved_locals(&ssa, body); debug!(?fully_moved); @@ -43,14 +45,8 @@ impl<'tcx> crate::MirPass<'tcx> for CopyProp { let any_replacement = ssa.copy_classes().iter_enumerated().any(|(l, &h)| l != h); - Replacer { - tcx, - copy_classes: ssa.copy_classes(), - fully_moved, - borrowed_locals: ssa.borrowed_locals(), - storage_to_remove, - } - .visit_body_preserves_cfg(body); + Replacer { tcx, copy_classes: ssa.copy_classes(), fully_moved, storage_to_remove } + .visit_body_preserves_cfg(body); if any_replacement { crate::simplify::remove_unused_definitions(body); @@ -102,7 +98,6 @@ struct Replacer<'a, 'tcx> { tcx: TyCtxt<'tcx>, fully_moved: DenseBitSet<Local>, storage_to_remove: DenseBitSet<Local>, - borrowed_locals: &'a DenseBitSet<Local>, copy_classes: &'a IndexSlice<Local, Local>, } @@ -111,34 +106,18 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> { self.tcx } + #[tracing::instrument(level = "trace", skip(self))] fn visit_local(&mut self, local: &mut Local, ctxt: PlaceContext, _: Location) { let new_local = self.copy_classes[*local]; - // We must not unify two locals that are borrowed. But this is fine if one is borrowed and - // the other is not. We chose to check the original local, and not the target. That way, if - // the original local is borrowed and the target is not, we do not pessimize the whole class. - if self.borrowed_locals.contains(*local) { - return; - } match ctxt { // Do not modify the local in storage statements. PlaceContext::NonUse(NonUseContext::StorageLive | NonUseContext::StorageDead) => {} - // The local should have been marked as non-SSA. - PlaceContext::MutatingUse(_) => assert_eq!(*local, new_local), // We access the value. _ => *local = new_local, } } - fn visit_place(&mut self, place: &mut Place<'tcx>, _: PlaceContext, loc: Location) { - if let Some(new_projection) = self.process_projection(place.projection, loc) { - place.projection = self.tcx().mk_place_elems(&new_projection); - } - - // Any non-mutating use context is ok. - let ctxt = PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy); - self.visit_local(&mut place.local, ctxt, loc) - } - + #[tracing::instrument(level = "trace", skip(self))] fn visit_operand(&mut self, operand: &mut Operand<'tcx>, loc: Location) { if let Operand::Move(place) = *operand // A move out of a projection of a copy is equivalent to a copy of the original @@ -151,6 +130,7 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> { self.super_operand(operand, loc); } + #[tracing::instrument(level = "trace", skip(self))] fn visit_statement(&mut self, stmt: &mut Statement<'tcx>, loc: Location) { // When removing storage statements, we need to remove both (#107511). if let StatementKind::StorageLive(l) | StatementKind::StorageDead(l) = stmt.kind diff --git a/compiler/rustc_mir_transform/src/ssa.rs b/compiler/rustc_mir_transform/src/ssa.rs index edd0cabca49..03b6f9b7ff3 100644 --- a/compiler/rustc_mir_transform/src/ssa.rs +++ b/compiler/rustc_mir_transform/src/ssa.rs @@ -293,6 +293,10 @@ impl<'tcx> Visitor<'tcx> for SsaVisitor<'_, 'tcx> { fn compute_copy_classes(ssa: &mut SsaLocals, body: &Body<'_>) { let mut direct_uses = std::mem::take(&mut ssa.direct_uses); let mut copies = IndexVec::from_fn_n(|l| l, body.local_decls.len()); + // We must not unify two locals that are borrowed. But this is fine if one is borrowed and + // the other is not. This bitset is keyed by *class head* and contains whether any member of + // the class is borrowed. + let mut borrowed_classes = ssa.borrowed_locals().clone(); for (local, rvalue, _) in ssa.assignments(body) { let (Rvalue::Use(Operand::Copy(place) | Operand::Move(place)) @@ -318,6 +322,11 @@ fn compute_copy_classes(ssa: &mut SsaLocals, body: &Body<'_>) { // visited before `local`, and we just have to copy the representing local. let head = copies[rhs]; + // Do not unify two borrowed locals. + if borrowed_classes.contains(local) && borrowed_classes.contains(head) { + continue; + } + if local == RETURN_PLACE { // `_0` is special, we cannot rename it. Instead, rename the class of `rhs` to // `RETURN_PLACE`. This is only possible if the class head is a temporary, not an @@ -330,14 +339,21 @@ fn compute_copy_classes(ssa: &mut SsaLocals, body: &Body<'_>) { *h = RETURN_PLACE; } } + if borrowed_classes.contains(head) { + borrowed_classes.insert(RETURN_PLACE); + } } else { copies[local] = head; + if borrowed_classes.contains(local) { + borrowed_classes.insert(head); + } } direct_uses[rhs] -= 1; } debug!(?copies); debug!(?direct_uses); + debug!(?borrowed_classes); // Invariant: `copies` must point to the head of an equivalence class. #[cfg(debug_assertions)] @@ -346,6 +362,13 @@ fn compute_copy_classes(ssa: &mut SsaLocals, body: &Body<'_>) { } debug_assert_eq!(copies[RETURN_PLACE], RETURN_PLACE); + // Invariant: `borrowed_classes` must be true if any member of the class is borrowed. + #[cfg(debug_assertions)] + for &head in copies.iter() { + let any_borrowed = ssa.borrowed_locals.iter().any(|l| copies[l] == head); + assert_eq!(borrowed_classes.contains(head), any_borrowed); + } + ssa.direct_uses = direct_uses; ssa.copy_classes = copies; } |