diff options
Diffstat (limited to 'compiler/rustc_mir_transform')
| -rw-r--r-- | compiler/rustc_mir_transform/src/coroutine.rs | 47 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/dataflow_const_prop.rs | 38 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/dest_prop.rs | 28 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/gvn.rs | 77 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/known_panics_lint.rs | 15 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/lib.rs | 4 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/lint.rs | 44 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/nrvo.rs | 234 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/promote_consts.rs | 4 | ||||
| -rw-r--r-- | compiler/rustc_mir_transform/src/validate.rs | 8 |
10 files changed, 97 insertions, 402 deletions
diff --git a/compiler/rustc_mir_transform/src/coroutine.rs b/compiler/rustc_mir_transform/src/coroutine.rs index 4603c695ded..08316aaed3b 100644 --- a/compiler/rustc_mir_transform/src/coroutine.rs +++ b/compiler/rustc_mir_transform/src/coroutine.rs @@ -1340,14 +1340,13 @@ fn create_cases<'tcx>( } } - if operation == Operation::Resume { + if operation == Operation::Resume && point.resume_arg != CTX_ARG.into() { // Move the resume argument to the destination place of the `Yield` terminator - let resume_arg = CTX_ARG; statements.push(Statement::new( source_info, StatementKind::Assign(Box::new(( point.resume_arg, - Rvalue::Use(Operand::Move(resume_arg.into())), + Rvalue::Use(Operand::Move(CTX_ARG.into())), ))), )); } @@ -1439,7 +1438,10 @@ fn check_field_tys_sized<'tcx>( } impl<'tcx> crate::MirPass<'tcx> for StateTransform { + #[instrument(level = "debug", skip(self, tcx, body), ret)] fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { + debug!(def_id = ?body.source.def_id()); + let Some(old_yield_ty) = body.yield_ty() else { // This only applies to coroutines return; @@ -1518,31 +1520,7 @@ impl<'tcx> crate::MirPass<'tcx> for StateTransform { cleanup_async_drops(body); } - // We also replace the resume argument and insert an `Assign`. - // This is needed because the resume argument `_2` might be live across a `yield`, in which - // case there is no `Assign` to it that the transform can turn into a store to the coroutine - // state. After the yield the slot in the coroutine state would then be uninitialized. - let resume_local = CTX_ARG; - let resume_ty = body.local_decls[resume_local].ty; - let old_resume_local = replace_local(resume_local, resume_ty, body, tcx); - - // When first entering the coroutine, move the resume argument into its old local - // (which is now a generator interior). - let source_info = SourceInfo::outermost(body.span); - let stmts = &mut body.basic_blocks_mut()[START_BLOCK].statements; - stmts.insert( - 0, - Statement::new( - source_info, - StatementKind::Assign(Box::new(( - old_resume_local.into(), - Rvalue::Use(Operand::Move(resume_local.into())), - ))), - ), - ); - let always_live_locals = always_storage_live_locals(body); - let movable = coroutine_kind.movability() == hir::Movability::Movable; let liveness_info = locals_live_across_suspend_points(tcx, body, &always_live_locals, movable); @@ -1583,6 +1561,21 @@ impl<'tcx> crate::MirPass<'tcx> for StateTransform { }; transform.visit_body(body); + // MIR parameters are not explicitly assigned-to when entering the MIR body. + // If we want to save their values inside the coroutine state, we need to do so explicitly. + let source_info = SourceInfo::outermost(body.span); + let args_iter = body.args_iter(); + body.basic_blocks.as_mut()[START_BLOCK].statements.splice( + 0..0, + args_iter.filter_map(|local| { + let (ty, variant_index, idx) = transform.remap[local]?; + let lhs = transform.make_field(variant_index, idx, ty); + let rhs = Rvalue::Use(Operand::Move(local.into())); + let assign = StatementKind::Assign(Box::new((lhs, rhs))); + Some(Statement::new(source_info, assign)) + }), + ); + // Update our MIR struct to reflect the changes we've made body.arg_count = 2; // self, resume arg body.spread_arg = None; diff --git a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs index fe53de31f75..5c984984d3c 100644 --- a/compiler/rustc_mir_transform/src/dataflow_const_prop.rs +++ b/compiler/rustc_mir_transform/src/dataflow_const_prop.rs @@ -412,18 +412,6 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> { state: &mut State<FlatSet<Scalar>>, ) -> ValueOrPlace<FlatSet<Scalar>> { let val = match rvalue { - Rvalue::Len(place) => { - let place_ty = place.ty(self.local_decls, self.tcx); - if let ty::Array(_, len) = place_ty.ty.kind() { - Const::Ty(self.tcx.types.usize, *len) - .try_eval_scalar(self.tcx, self.typing_env) - .map_or(FlatSet::Top, FlatSet::Elem) - } else if let [ProjectionElem::Deref] = place.projection[..] { - state.get_len(place.local.into(), &self.map) - } else { - FlatSet::Top - } - } Rvalue::Cast(CastKind::IntToInt | CastKind::IntToFloat, operand, ty) => { let Ok(layout) = self.tcx.layout_of(self.typing_env.as_query_input(*ty)) else { return ValueOrPlace::Value(FlatSet::Top); @@ -465,15 +453,23 @@ impl<'a, 'tcx> ConstAnalysis<'a, 'tcx> { let (val, _overflow) = self.binary_op(state, *op, left, right); val } - Rvalue::UnaryOp(op, operand) => match self.eval_operand(operand, state) { - FlatSet::Elem(value) => self - .ecx - .unary_op(*op, &value) - .discard_err() - .map_or(FlatSet::Top, |val| self.wrap_immediate(*val)), - FlatSet::Bottom => FlatSet::Bottom, - FlatSet::Top => FlatSet::Top, - }, + Rvalue::UnaryOp(op, operand) => { + if let UnOp::PtrMetadata = op + && let Some(place) = operand.place() + && let Some(len) = self.map.find_len(place.as_ref()) + { + return ValueOrPlace::Place(len); + } + match self.eval_operand(operand, state) { + FlatSet::Elem(value) => self + .ecx + .unary_op(*op, &value) + .discard_err() + .map_or(FlatSet::Top, |val| self.wrap_immediate(*val)), + FlatSet::Bottom => FlatSet::Bottom, + FlatSet::Top => FlatSet::Top, + } + } Rvalue::NullaryOp(null_op, ty) => { let Ok(layout) = self.tcx.layout_of(self.typing_env.as_query_input(*ty)) else { return ValueOrPlace::Value(FlatSet::Top); diff --git a/compiler/rustc_mir_transform/src/dest_prop.rs b/compiler/rustc_mir_transform/src/dest_prop.rs index c57483a6811..74c22ff10c1 100644 --- a/compiler/rustc_mir_transform/src/dest_prop.rs +++ b/compiler/rustc_mir_transform/src/dest_prop.rs @@ -141,7 +141,7 @@ use rustc_data_structures::union_find::UnionFind; use rustc_index::bit_set::DenseBitSet; use rustc_index::interval::SparseIntervalMatrix; use rustc_index::{IndexVec, newtype_index}; -use rustc_middle::mir::visit::{MutVisitor, PlaceContext, Visitor}; +use rustc_middle::mir::visit::{MutVisitor, PlaceContext, VisitPlacesWith, Visitor}; use rustc_middle::mir::*; use rustc_middle::ty::TyCtxt; use rustc_mir_dataflow::impls::{DefUse, MaybeLiveLocals}; @@ -153,15 +153,7 @@ pub(super) struct DestinationPropagation; impl<'tcx> crate::MirPass<'tcx> for DestinationPropagation { fn is_enabled(&self, sess: &rustc_session::Session) -> bool { - // For now, only run at MIR opt level 3. Two things need to be changed before this can be - // turned on by default: - // 1. Because of the overeager removal of storage statements, this can cause stack space - // regressions. This opt is not the place to fix this though, it's a more general - // problem in MIR. - // 2. Despite being an overall perf improvement, this still causes a 30% regression in - // keccak. We can temporarily fix this by bounding function size, but in the long term - // we should fix this by being smarter about invalidating analysis results. - sess.mir_opt_level() >= 3 + sess.mir_opt_level() >= 2 } #[tracing::instrument(level = "trace", skip(self, tcx, body))] @@ -511,22 +503,6 @@ impl TwoStepIndex { } } -struct VisitPlacesWith<F>(F); - -impl<'tcx, F> Visitor<'tcx> for VisitPlacesWith<F> -where - F: FnMut(Place<'tcx>, PlaceContext), -{ - fn visit_local(&mut self, local: Local, ctxt: PlaceContext, _: Location) { - (self.0)(local.into(), ctxt); - } - - fn visit_place(&mut self, place: &Place<'tcx>, ctxt: PlaceContext, location: Location) { - (self.0)(*place, ctxt); - self.visit_projection(place.as_ref(), ctxt, location); - } -} - /// Add points depending on the result of the given dataflow analysis. fn save_as_intervals<'tcx>( elements: &DenseLocationMap, diff --git a/compiler/rustc_mir_transform/src/gvn.rs b/compiler/rustc_mir_transform/src/gvn.rs index bf6aa800d20..30e68a3f650 100644 --- a/compiler/rustc_mir_transform/src/gvn.rs +++ b/compiler/rustc_mir_transform/src/gvn.rs @@ -200,8 +200,6 @@ enum Value<'tcx> { Projection(VnIndex, ProjectionElem<VnIndex, ()>), /// Discriminant of the given value. Discriminant(VnIndex), - /// Length of an array or slice. - Len(VnIndex), // Operations. NullaryOp(NullOp<'tcx>, Ty<'tcx>), @@ -477,11 +475,6 @@ impl<'body, 'tcx> VnState<'body, 'tcx> { self.ecx.discriminant_for_variant(base.layout.ty, variant).discard_err()?; discr_value.into() } - Len(slice) => { - let slice = self.evaluated[slice].as_ref()?; - let len = slice.len(&self.ecx).discard_err()?; - ImmTy::from_uint(len, ty).into() - } NullaryOp(null_op, arg_ty) => { let arg_layout = self.ecx.layout_of(arg_ty).ok()?; if let NullOp::SizeOf | NullOp::AlignOf = null_op @@ -841,7 +834,6 @@ impl<'body, 'tcx> VnState<'body, 'tcx> { } // Operations. - Rvalue::Len(ref mut place) => return self.simplify_len(place, location), Rvalue::Cast(ref mut kind, ref mut value, to) => { return self.simplify_cast(kind, value, to, location); } @@ -1049,7 +1041,7 @@ impl<'body, 'tcx> VnState<'body, 'tcx> { if op == UnOp::PtrMetadata { let mut was_updated = false; loop { - match self.get(arg_index) { + arg_index = match self.get(arg_index) { // Pointer casts that preserve metadata, such as // `*const [i32]` <-> `*mut [i32]` <-> `*mut [f32]`. // It's critical that this not eliminate cases like @@ -1061,9 +1053,19 @@ impl<'body, 'tcx> VnState<'body, 'tcx> { Value::Cast { kind: CastKind::PtrToPtr, value: inner } if self.pointers_have_same_metadata(self.ty(*inner), arg_ty) => { - arg_index = *inner; - was_updated = true; - continue; + *inner + } + + // We have an unsizing cast, which assigns the length to wide pointer metadata. + Value::Cast { + kind: CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize, _), + value: from, + } if let Some(from) = self.ty(*from).builtin_deref(true) + && let ty::Array(_, len) = from.kind() + && let Some(to) = self.ty(arg_index).builtin_deref(true) + && let ty::Slice(..) = to.kind() => + { + return Some(self.insert_constant(Const::Ty(self.tcx.types.usize, *len))); } // `&mut *p`, `&raw *p`, etc don't change metadata. @@ -1072,18 +1074,16 @@ impl<'body, 'tcx> VnState<'body, 'tcx> { place.as_ref() && let Some(local_index) = self.locals[local] => { - arg_index = local_index; - was_updated = true; - continue; + local_index } - _ => { - if was_updated && let Some(op) = self.try_as_operand(arg_index, location) { - *arg_op = op; - } - break; - } - } + _ => break, + }; + was_updated = true; + } + + if was_updated && let Some(op) = self.try_as_operand(arg_index, location) { + *arg_op = op; } } @@ -1407,39 +1407,6 @@ impl<'body, 'tcx> VnState<'body, 'tcx> { Some(self.insert(to, Value::Cast { kind, value })) } - fn simplify_len(&mut self, place: &mut Place<'tcx>, location: Location) -> Option<VnIndex> { - // Trivial case: we are fetching a statically known length. - let place_ty = place.ty(self.local_decls, self.tcx).ty; - if let ty::Array(_, len) = place_ty.kind() { - return Some(self.insert_constant(Const::Ty(self.tcx.types.usize, *len))); - } - - let mut inner = self.simplify_place_value(place, location)?; - - // The length information is stored in the wide pointer. - // Reborrowing copies length information from one pointer to the other. - while let Value::Address { place: borrowed, .. } = self.get(inner) - && let [PlaceElem::Deref] = borrowed.projection[..] - && let Some(borrowed) = self.locals[borrowed.local] - { - inner = borrowed; - } - - // We have an unsizing cast, which assigns the length to wide pointer metadata. - if let Value::Cast { kind, value: from } = self.get(inner) - && let CastKind::PointerCoercion(ty::adjustment::PointerCoercion::Unsize, _) = kind - && let Some(from) = self.ty(*from).builtin_deref(true) - && let ty::Array(_, len) = from.kind() - && let Some(to) = self.ty(inner).builtin_deref(true) - && let ty::Slice(..) = to.kind() - { - return Some(self.insert_constant(Const::Ty(self.tcx.types.usize, *len))); - } - - // Fallback: a symbolic `Len`. - Some(self.insert(self.tcx.types.usize, Value::Len(inner))) - } - fn pointers_have_same_metadata(&self, left_ptr_ty: Ty<'tcx>, right_ptr_ty: Ty<'tcx>) -> bool { let left_meta_ty = left_ptr_ty.pointee_metadata_ty_or_projection(self.tcx); let right_meta_ty = right_ptr_ty.pointee_metadata_ty_or_projection(self.tcx); diff --git a/compiler/rustc_mir_transform/src/known_panics_lint.rs b/compiler/rustc_mir_transform/src/known_panics_lint.rs index 481c7941909..aaacc5866a2 100644 --- a/compiler/rustc_mir_transform/src/known_panics_lint.rs +++ b/compiler/rustc_mir_transform/src/known_panics_lint.rs @@ -441,7 +441,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { | Rvalue::Use(..) | Rvalue::CopyForDeref(..) | Rvalue::Repeat(..) - | Rvalue::Len(..) | Rvalue::Cast(..) | Rvalue::ShallowInitBox(..) | Rvalue::Discriminant(..) @@ -604,20 +603,6 @@ impl<'mir, 'tcx> ConstPropagator<'mir, 'tcx> { return None; } - Len(place) => { - let len = if let ty::Array(_, n) = place.ty(self.local_decls(), self.tcx).ty.kind() - { - n.try_to_target_usize(self.tcx)? - } else { - match self.get_const(place)? { - Value::Immediate(src) => src.len(&self.ecx).discard_err()?, - Value::Aggregate { fields, .. } => fields.len() as u64, - Value::Uninit => return None, - } - }; - ImmTy::from_scalar(Scalar::from_target_usize(len, self), layout).into() - } - Ref(..) | RawPtr(..) => return None, NullaryOp(ref null_op, ty) => { diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs index 1663dfa744f..9ff7e0b5500 100644 --- a/compiler/rustc_mir_transform/src/lib.rs +++ b/compiler/rustc_mir_transform/src/lib.rs @@ -156,7 +156,6 @@ declare_passes! { mod match_branches : MatchBranchSimplification; mod mentioned_items : MentionedItems; mod multiple_return_terminators : MultipleReturnTerminators; - mod nrvo : RenameReturnPlace; mod post_drop_elaboration : CheckLiveDrops; mod prettify : ReorderBasicBlocks, ReorderLocals; mod promote_consts : PromoteTemps; @@ -715,7 +714,6 @@ pub(crate) fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<' &jump_threading::JumpThreading, &early_otherwise_branch::EarlyOtherwiseBranch, &simplify_comparison_integral::SimplifyComparisonIntegral, - &dest_prop::DestinationPropagation, &o1(simplify_branches::SimplifyConstCondition::Final), &o1(remove_noop_landing_pads::RemoveNoopLandingPads), &o1(simplify::SimplifyCfg::Final), @@ -723,7 +721,7 @@ pub(crate) fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<' &strip_debuginfo::StripDebugInfo, ©_prop::CopyProp, &dead_store_elimination::DeadStoreElimination::Final, - &nrvo::RenameReturnPlace, + &dest_prop::DestinationPropagation, &simplify::SimplifyLocals::Final, &multiple_return_terminators::MultipleReturnTerminators, &large_enums::EnumSizeOpt { discrepancy: 128 }, diff --git a/compiler/rustc_mir_transform/src/lint.rs b/compiler/rustc_mir_transform/src/lint.rs index f472c7cb493..2ab49645dc4 100644 --- a/compiler/rustc_mir_transform/src/lint.rs +++ b/compiler/rustc_mir_transform/src/lint.rs @@ -6,7 +6,7 @@ use std::borrow::Cow; use rustc_data_structures::fx::FxHashSet; use rustc_index::bit_set::DenseBitSet; -use rustc_middle::mir::visit::{PlaceContext, Visitor}; +use rustc_middle::mir::visit::{PlaceContext, VisitPlacesWith, Visitor}; use rustc_middle::mir::*; use rustc_middle::ty::TyCtxt; use rustc_mir_dataflow::impls::{MaybeStorageDead, MaybeStorageLive, always_storage_live_locals}; @@ -79,15 +79,39 @@ impl<'a, 'tcx> Visitor<'tcx> for Lint<'a, 'tcx> { fn visit_statement(&mut self, statement: &Statement<'tcx>, location: Location) { match &statement.kind { StatementKind::Assign(box (dest, rvalue)) => { - if let Rvalue::Use(Operand::Copy(src) | Operand::Move(src)) = rvalue { - // The sides of an assignment must not alias. Currently this just checks whether - // the places are identical. - if dest == src { - self.fail( - location, - "encountered `Assign` statement with overlapping memory", - ); - } + let forbid_aliasing = match rvalue { + Rvalue::Use(..) + | Rvalue::CopyForDeref(..) + | Rvalue::Repeat(..) + | Rvalue::Aggregate(..) + | Rvalue::Cast(..) + | Rvalue::ShallowInitBox(..) + | Rvalue::WrapUnsafeBinder(..) => true, + Rvalue::ThreadLocalRef(..) + | Rvalue::NullaryOp(..) + | Rvalue::UnaryOp(..) + | Rvalue::BinaryOp(..) + | Rvalue::Ref(..) + | Rvalue::RawPtr(..) + | Rvalue::Discriminant(..) => false, + }; + // The sides of an assignment must not alias. + if forbid_aliasing { + VisitPlacesWith(|src: Place<'tcx>, _| { + if *dest == src + || (dest.local == src.local + && !dest.is_indirect() + && !src.is_indirect()) + { + self.fail( + location, + format!( + "encountered `{statement:?}` statement with overlapping memory" + ), + ); + } + }) + .visit_rvalue(rvalue, location); } } StatementKind::StorageLive(local) => { diff --git a/compiler/rustc_mir_transform/src/nrvo.rs b/compiler/rustc_mir_transform/src/nrvo.rs deleted file mode 100644 index 965002aae04..00000000000 --- a/compiler/rustc_mir_transform/src/nrvo.rs +++ /dev/null @@ -1,234 +0,0 @@ -//! See the docs for [`RenameReturnPlace`]. - -use rustc_hir::Mutability; -use rustc_index::bit_set::DenseBitSet; -use rustc_middle::bug; -use rustc_middle::mir::visit::{MutVisitor, NonUseContext, PlaceContext, Visitor}; -use rustc_middle::mir::{self, BasicBlock, Local, Location}; -use rustc_middle::ty::TyCtxt; -use tracing::{debug, trace}; - -/// This pass looks for MIR that always copies the same local into the return place and eliminates -/// the copy by renaming all uses of that local to `_0`. -/// -/// This allows LLVM to perform an optimization similar to the named return value optimization -/// (NRVO) that is guaranteed in C++. This avoids a stack allocation and `memcpy` for the -/// relatively common pattern of allocating a buffer on the stack, mutating it, and returning it by -/// value like so: -/// -/// ```rust -/// fn foo(init: fn(&mut [u8; 1024])) -> [u8; 1024] { -/// let mut buf = [0; 1024]; -/// init(&mut buf); -/// buf -/// } -/// ``` -/// -/// For now, this pass is very simple and only capable of eliminating a single copy. A more general -/// version of copy propagation, such as the one based on non-overlapping live ranges in [#47954] and -/// [#71003], could yield even more benefits. -/// -/// [#47954]: https://github.com/rust-lang/rust/pull/47954 -/// [#71003]: https://github.com/rust-lang/rust/pull/71003 -pub(super) struct RenameReturnPlace; - -impl<'tcx> crate::MirPass<'tcx> for RenameReturnPlace { - fn is_enabled(&self, sess: &rustc_session::Session) -> bool { - // unsound: #111005 - sess.mir_opt_level() > 0 && sess.opts.unstable_opts.unsound_mir_opts - } - - fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut mir::Body<'tcx>) { - let def_id = body.source.def_id(); - let Some(returned_local) = local_eligible_for_nrvo(body) else { - debug!("`{:?}` was ineligible for NRVO", def_id); - return; - }; - - debug!( - "`{:?}` was eligible for NRVO, making {:?} the return place", - def_id, returned_local - ); - - RenameToReturnPlace { tcx, to_rename: returned_local }.visit_body_preserves_cfg(body); - - // Clean up the `NOP`s we inserted for statements made useless by our renaming. - for block_data in body.basic_blocks.as_mut_preserves_cfg() { - block_data.statements.retain(|stmt| stmt.kind != mir::StatementKind::Nop); - } - - // Overwrite the debuginfo of `_0` with that of the renamed local. - let (renamed_decl, ret_decl) = - body.local_decls.pick2_mut(returned_local, mir::RETURN_PLACE); - - // Sometimes, the return place is assigned a local of a different but coercible type, for - // example `&mut T` instead of `&T`. Overwriting the `LocalInfo` for the return place means - // its type may no longer match the return type of its function. This doesn't cause a - // problem in codegen because these two types are layout-compatible, but may be unexpected. - debug!("_0: {:?} = {:?}: {:?}", ret_decl.ty, returned_local, renamed_decl.ty); - ret_decl.clone_from(renamed_decl); - - // The return place is always mutable. - ret_decl.mutability = Mutability::Mut; - } - - fn is_required(&self) -> bool { - false - } -} - -/// MIR that is eligible for the NRVO must fulfill two conditions: -/// 1. The return place must not be read prior to the `Return` terminator. -/// 2. A simple assignment of a whole local to the return place (e.g., `_0 = _1`) must be the -/// only definition of the return place reaching the `Return` terminator. -/// -/// If the MIR fulfills both these conditions, this function returns the `Local` that is assigned -/// to the return place along all possible paths through the control-flow graph. -fn local_eligible_for_nrvo(body: &mir::Body<'_>) -> Option<Local> { - if IsReturnPlaceRead::run(body) { - return None; - } - - let mut copied_to_return_place = None; - for block in body.basic_blocks.indices() { - // Look for blocks with a `Return` terminator. - if !matches!(body[block].terminator().kind, mir::TerminatorKind::Return) { - continue; - } - - // Look for an assignment of a single local to the return place prior to the `Return`. - let returned_local = find_local_assigned_to_return_place(block, body)?; - match body.local_kind(returned_local) { - // FIXME: Can we do this for arguments as well? - mir::LocalKind::Arg => return None, - - mir::LocalKind::ReturnPointer => bug!("Return place was assigned to itself?"), - mir::LocalKind::Temp => {} - } - - // If multiple different locals are copied to the return place. We can't pick a - // single one to rename. - if copied_to_return_place.is_some_and(|old| old != returned_local) { - return None; - } - - copied_to_return_place = Some(returned_local); - } - - copied_to_return_place -} - -fn find_local_assigned_to_return_place(start: BasicBlock, body: &mir::Body<'_>) -> Option<Local> { - let mut block = start; - let mut seen = DenseBitSet::new_empty(body.basic_blocks.len()); - - // Iterate as long as `block` has exactly one predecessor that we have not yet visited. - while seen.insert(block) { - trace!("Looking for assignments to `_0` in {:?}", block); - - let local = body[block].statements.iter().rev().find_map(as_local_assigned_to_return_place); - if local.is_some() { - return local; - } - - match body.basic_blocks.predecessors()[block].as_slice() { - &[pred] => block = pred, - _ => return None, - } - } - - None -} - -// If this statement is an assignment of an unprojected local to the return place, -// return that local. -fn as_local_assigned_to_return_place(stmt: &mir::Statement<'_>) -> Option<Local> { - if let mir::StatementKind::Assign(box (lhs, rhs)) = &stmt.kind { - if lhs.as_local() == Some(mir::RETURN_PLACE) { - if let mir::Rvalue::Use(mir::Operand::Copy(rhs) | mir::Operand::Move(rhs)) = rhs { - return rhs.as_local(); - } - } - } - - None -} - -struct RenameToReturnPlace<'tcx> { - to_rename: Local, - tcx: TyCtxt<'tcx>, -} - -/// Replaces all uses of `self.to_rename` with `_0`. -impl<'tcx> MutVisitor<'tcx> for RenameToReturnPlace<'tcx> { - fn tcx(&self) -> TyCtxt<'tcx> { - self.tcx - } - - fn visit_statement(&mut self, stmt: &mut mir::Statement<'tcx>, loc: Location) { - // Remove assignments of the local being replaced to the return place, since it is now the - // return place: - // _0 = _1 - if as_local_assigned_to_return_place(stmt) == Some(self.to_rename) { - stmt.kind = mir::StatementKind::Nop; - return; - } - - // Remove storage annotations for the local being replaced: - // StorageLive(_1) - if let mir::StatementKind::StorageLive(local) | mir::StatementKind::StorageDead(local) = - stmt.kind - { - if local == self.to_rename { - stmt.kind = mir::StatementKind::Nop; - return; - } - } - - self.super_statement(stmt, loc) - } - - fn visit_terminator(&mut self, terminator: &mut mir::Terminator<'tcx>, loc: Location) { - // Ignore the implicit "use" of the return place in a `Return` statement. - if let mir::TerminatorKind::Return = terminator.kind { - return; - } - - self.super_terminator(terminator, loc); - } - - fn visit_local(&mut self, l: &mut Local, ctxt: PlaceContext, _: Location) { - if *l == mir::RETURN_PLACE { - assert_eq!(ctxt, PlaceContext::NonUse(NonUseContext::VarDebugInfo)); - } else if *l == self.to_rename { - *l = mir::RETURN_PLACE; - } - } -} - -struct IsReturnPlaceRead(bool); - -impl IsReturnPlaceRead { - fn run(body: &mir::Body<'_>) -> bool { - let mut vis = IsReturnPlaceRead(false); - vis.visit_body(body); - vis.0 - } -} - -impl<'tcx> Visitor<'tcx> for IsReturnPlaceRead { - fn visit_local(&mut self, l: Local, ctxt: PlaceContext, _: Location) { - if l == mir::RETURN_PLACE && ctxt.is_use() && !ctxt.is_place_assignment() { - self.0 = true; - } - } - - fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, loc: Location) { - // Ignore the implicit "use" of the return place in a `Return` statement. - if let mir::TerminatorKind::Return = terminator.kind { - return; - } - - self.super_terminator(terminator, loc); - } -} diff --git a/compiler/rustc_mir_transform/src/promote_consts.rs b/compiler/rustc_mir_transform/src/promote_consts.rs index 9ea2eb4f25d..a0b0c8c990f 100644 --- a/compiler/rustc_mir_transform/src/promote_consts.rs +++ b/compiler/rustc_mir_transform/src/promote_consts.rs @@ -437,9 +437,7 @@ impl<'tcx> Validator<'_, 'tcx> { self.validate_operand(op)? } - Rvalue::Discriminant(place) | Rvalue::Len(place) => { - self.validate_place(place.as_ref())? - } + Rvalue::Discriminant(place) => self.validate_place(place.as_ref())?, Rvalue::ThreadLocalRef(_) => return Err(Unpromotable), diff --git a/compiler/rustc_mir_transform/src/validate.rs b/compiler/rustc_mir_transform/src/validate.rs index 99e4782e470..c8a9a88dc3f 100644 --- a/compiler/rustc_mir_transform/src/validate.rs +++ b/compiler/rustc_mir_transform/src/validate.rs @@ -1064,14 +1064,6 @@ impl<'a, 'tcx> Visitor<'tcx> for TypeChecker<'a, 'tcx> { } } Rvalue::Ref(..) => {} - Rvalue::Len(p) => { - let pty = p.ty(&self.body.local_decls, self.tcx).ty; - check_kinds!( - pty, - "Cannot compute length of non-array type {:?}", - ty::Array(..) | ty::Slice(..) - ); - } Rvalue::BinaryOp(op, vals) => { use BinOp::*; let a = vals.0.ty(&self.body.local_decls, self.tcx); |