diff options
Diffstat (limited to 'compiler/rustc_mir_transform/src')
| -rw-r--r-- | compiler/rustc_mir_transform/src/copy_prop.rs | 41 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/gvn.rs | 18 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/normalize_array_len.rs | 3 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/ref_prop.rs | 3 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/ssa.rs | 55 |
5 files changed, 78 insertions, 42 deletions
diff --git a/compiler/rustc_mir_transform/src/copy_prop.rs b/compiler/rustc_mir_transform/src/copy_prop.rs index 0119b95cced..c1f9313a377 100644 --- a/compiler/rustc_mir_transform/src/copy_prop.rs +++ b/compiler/rustc_mir_transform/src/copy_prop.rs @@ -3,7 +3,6 @@ use rustc_index::IndexSlice; use rustc_middle::mir::visit::*; use rustc_middle::mir::*; use rustc_middle::ty::TyCtxt; -use rustc_mir_dataflow::impls::borrowed_locals; use crate::ssa::SsaLocals; @@ -32,8 +31,8 @@ impl<'tcx> MirPass<'tcx> for CopyProp { } fn propagate_ssa<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { - let borrowed_locals = borrowed_locals(body); - let ssa = SsaLocals::new(body); + let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id()); + let ssa = SsaLocals::new(tcx, body, param_env); let fully_moved = fully_moved_locals(&ssa, body); debug!(?fully_moved); @@ -51,7 +50,7 @@ fn propagate_ssa<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { tcx, copy_classes: ssa.copy_classes(), fully_moved, - borrowed_locals, + borrowed_locals: ssa.borrowed_locals(), storage_to_remove, } .visit_body_preserves_cfg(body); @@ -101,7 +100,7 @@ struct Replacer<'a, 'tcx> { tcx: TyCtxt<'tcx>, fully_moved: BitSet<Local>, storage_to_remove: BitSet<Local>, - borrowed_locals: BitSet<Local>, + borrowed_locals: &'a BitSet<Local>, copy_classes: &'a IndexSlice<Local, Local>, } @@ -112,6 +111,12 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> { 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) => {} @@ -122,32 +127,14 @@ impl<'tcx> MutVisitor<'tcx> for Replacer<'_, 'tcx> { } } - fn visit_place(&mut self, place: &mut Place<'tcx>, ctxt: PlaceContext, loc: Location) { + 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); } - let observes_address = match ctxt { - PlaceContext::NonMutatingUse( - NonMutatingUseContext::SharedBorrow - | NonMutatingUseContext::FakeBorrow - | NonMutatingUseContext::AddressOf, - ) => true, - // For debuginfo, merging locals is ok. - PlaceContext::NonUse(NonUseContext::VarDebugInfo) => { - self.borrowed_locals.contains(place.local) - } - _ => false, - }; - if observes_address && !place.is_indirect() { - // We observe the address of `place.local`. Do not replace it. - } else { - self.visit_local( - &mut place.local, - PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy), - loc, - ) - } + // Any non-mutating use context is ok. + let ctxt = PlaceContext::NonMutatingUse(NonMutatingUseContext::Copy); + self.visit_local(&mut place.local, ctxt, loc) } fn visit_operand(&mut self, operand: &mut Operand<'tcx>, loc: Location) { diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs index 24832086b16..4dd595ce1e1 100644 --- a/compiler/rustc_mir_transform/src/gvn.rs +++ b/compiler/rustc_mir_transform/src/gvn.rs @@ -121,7 +121,7 @@ impl<'tcx> MirPass<'tcx> for GVN { fn propagate_ssa<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id()); - let ssa = SsaLocals::new(body); + let ssa = SsaLocals::new(tcx, body, param_env); // Clone dominators as we need them while mutating the body. let dominators = body.basic_blocks.dominators().clone(); @@ -724,6 +724,14 @@ impl<'body, 'tcx> VnState<'body, 'tcx> { // Invariant: `value` holds the value up-to the `index`th projection excluded. let mut value = self.locals[place.local]?; for (index, proj) in place.projection.iter().enumerate() { + if let Value::Projection(pointer, ProjectionElem::Deref) = *self.get(value) + && let Value::Address { place: mut pointee, kind, .. } = *self.get(pointer) + && let AddressKind::Ref(BorrowKind::Shared) = kind + && let Some(v) = self.simplify_place_value(&mut pointee, location) + { + value = v; + place_ref = pointee.project_deeper(&place.projection[index..], self.tcx).as_ref(); + } if let Some(local) = self.try_as_local(value, location) { // Both `local` and `Place { local: place.local, projection: projection[..index] }` // hold the same value. Therefore, following place holds the value in the original @@ -735,6 +743,14 @@ impl<'body, 'tcx> VnState<'body, 'tcx> { value = self.project(base, value, proj)?; } + if let Value::Projection(pointer, ProjectionElem::Deref) = *self.get(value) + && let Value::Address { place: mut pointee, kind, .. } = *self.get(pointer) + && let AddressKind::Ref(BorrowKind::Shared) = kind + && let Some(v) = self.simplify_place_value(&mut pointee, location) + { + value = v; + place_ref = pointee.project_deeper(&[], self.tcx).as_ref(); + } if let Some(new_local) = self.try_as_local(value, location) { place_ref = PlaceRef { local: new_local, projection: &[] }; } diff --git a/compiler/rustc_mir_transform/src/normalize_array_len.rs b/compiler/rustc_mir_transform/src/normalize_array_len.rs index 128634bd7f2..c26a5461633 100644 --- a/compiler/rustc_mir_transform/src/normalize_array_len.rs +++ b/compiler/rustc_mir_transform/src/normalize_array_len.rs @@ -22,7 +22,8 @@ impl<'tcx> MirPass<'tcx> for NormalizeArrayLen { } fn normalize_array_len_calls<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { - let ssa = SsaLocals::new(body); + let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id()); + let ssa = SsaLocals::new(tcx, body, param_env); let slice_lengths = compute_slice_length(tcx, &ssa, body); debug!(?slice_lengths); diff --git a/compiler/rustc_mir_transform/src/ref_prop.rs b/compiler/rustc_mir_transform/src/ref_prop.rs index d5642be5513..044ae32c1d4 100644 --- a/compiler/rustc_mir_transform/src/ref_prop.rs +++ b/compiler/rustc_mir_transform/src/ref_prop.rs @@ -82,7 +82,8 @@ impl<'tcx> MirPass<'tcx> for ReferencePropagation { } fn propagate_ssa<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) -> bool { - let ssa = SsaLocals::new(body); + let param_env = tcx.param_env_reveal_all_normalized(body.source.def_id()); + let ssa = SsaLocals::new(tcx, body, param_env); let mut replacer = compute_replacement(tcx, body, &ssa); debug!(?replacer.targets); diff --git a/compiler/rustc_mir_transform/src/ssa.rs b/compiler/rustc_mir_transform/src/ssa.rs index fddc62e6652..55fed7d9da2 100644 --- a/compiler/rustc_mir_transform/src/ssa.rs +++ b/compiler/rustc_mir_transform/src/ssa.rs @@ -2,8 +2,9 @@ //! 1/ They are only assigned-to once, either as a function parameter, or in an assign statement; //! 2/ This single assignment dominates all uses; //! -//! As a consequence of rule 2, we consider that borrowed locals are not SSA, even if they are -//! `Freeze`, as we do not track that the assignment dominates all uses of the borrow. +//! As we do not track indirect assignments, a local that has its address taken (either by +//! AddressOf or by borrowing) is considered non-SSA. However, it is UB to modify through an +//! immutable borrow of a `Freeze` local. Those can still be considered to be SSA. use rustc_data_structures::graph::dominators::Dominators; use rustc_index::bit_set::BitSet; @@ -11,6 +12,7 @@ use rustc_index::{IndexSlice, IndexVec}; use rustc_middle::middle::resolve_bound_vars::Set1; use rustc_middle::mir::visit::*; use rustc_middle::mir::*; +use rustc_middle::ty::{ParamEnv, TyCtxt}; pub struct SsaLocals { /// Assignments to each local. This defines whether the local is SSA. @@ -24,6 +26,8 @@ pub struct SsaLocals { /// Number of "direct" uses of each local, ie. uses that are not dereferences. /// We ignore non-uses (Storage statements, debuginfo). direct_uses: IndexVec<Local, u32>, + /// Set of SSA locals that are immutably borrowed. + borrowed_locals: BitSet<Local>, } pub enum AssignedValue<'a, 'tcx> { @@ -33,15 +37,22 @@ pub enum AssignedValue<'a, 'tcx> { } impl SsaLocals { - pub fn new<'tcx>(body: &Body<'tcx>) -> SsaLocals { + pub fn new<'tcx>(tcx: TyCtxt<'tcx>, body: &Body<'tcx>, param_env: ParamEnv<'tcx>) -> SsaLocals { let assignment_order = Vec::with_capacity(body.local_decls.len()); let assignments = IndexVec::from_elem(Set1::Empty, &body.local_decls); let dominators = body.basic_blocks.dominators(); let direct_uses = IndexVec::from_elem(0, &body.local_decls); - let mut visitor = - SsaVisitor { body, assignments, assignment_order, dominators, direct_uses }; + let borrowed_locals = BitSet::new_empty(body.local_decls.len()); + let mut visitor = SsaVisitor { + body, + assignments, + assignment_order, + dominators, + direct_uses, + borrowed_locals, + }; for local in body.args_iter() { visitor.assignments[local] = Set1::One(DefLocation::Argument); @@ -58,6 +69,16 @@ impl SsaLocals { visitor.visit_var_debug_info(var_debug_info); } + // The immutability of shared borrows only works on `Freeze` locals. If the visitor found + // borrows, we need to check the types. For raw pointers and mutable borrows, the locals + // have already been marked as non-SSA. + debug!(?visitor.borrowed_locals); + for local in visitor.borrowed_locals.iter() { + if !body.local_decls[local].ty.is_freeze(tcx, param_env) { + visitor.assignments[local] = Set1::Many; + } + } + debug!(?visitor.assignments); debug!(?visitor.direct_uses); @@ -70,6 +91,7 @@ impl SsaLocals { assignments: visitor.assignments, assignment_order: visitor.assignment_order, direct_uses: visitor.direct_uses, + borrowed_locals: visitor.borrowed_locals, // This is filled by `compute_copy_classes`. copy_classes: IndexVec::default(), }; @@ -174,6 +196,11 @@ impl SsaLocals { &self.copy_classes } + /// Set of SSA locals that are immutably borrowed. + pub fn borrowed_locals(&self) -> &BitSet<Local> { + &self.borrowed_locals + } + /// Make a property uniform on a copy equivalence class by removing elements. pub fn meet_copy_equivalence(&self, property: &mut BitSet<Local>) { // Consolidate to have a local iff all its copies are. @@ -208,6 +235,8 @@ struct SsaVisitor<'tcx, 'a> { assignments: IndexVec<Local, Set1<DefLocation>>, assignment_order: Vec<Local>, direct_uses: IndexVec<Local, u32>, + // Track locals that are immutably borrowed, so we can check their type is `Freeze` later. + borrowed_locals: BitSet<Local>, } impl SsaVisitor<'_, '_> { @@ -232,16 +261,18 @@ impl<'tcx> Visitor<'tcx> for SsaVisitor<'tcx, '_> { PlaceContext::MutatingUse(MutatingUseContext::Projection) | PlaceContext::NonMutatingUse(NonMutatingUseContext::Projection) => bug!(), // Anything can happen with raw pointers, so remove them. - // We do not verify that all uses of the borrow dominate the assignment to `local`, - // so we have to remove them too. - PlaceContext::NonMutatingUse( - NonMutatingUseContext::SharedBorrow - | NonMutatingUseContext::FakeBorrow - | NonMutatingUseContext::AddressOf, - ) + PlaceContext::NonMutatingUse(NonMutatingUseContext::AddressOf) | PlaceContext::MutatingUse(_) => { self.assignments[local] = Set1::Many; } + // Immutable borrows are ok, but we need to delay a check that the type is `Freeze`. + PlaceContext::NonMutatingUse( + NonMutatingUseContext::SharedBorrow | NonMutatingUseContext::FakeBorrow, + ) => { + self.borrowed_locals.insert(local); + self.check_dominates(local, loc); + self.direct_uses[local] += 1; + } PlaceContext::NonMutatingUse(_) => { self.check_dominates(local, loc); self.direct_uses[local] += 1; |