diff --git a/src/librustc_mir/dataflow/impls/mod.rs b/src/librustc_mir/dataflow/impls/mod.rs index d5def038912..ed01d6b01ea 100644 --- a/src/librustc_mir/dataflow/impls/mod.rs +++ b/src/librustc_mir/dataflow/impls/mod.rs @@ -30,7 +30,7 @@ pub use self::borrows::Borrows; pub use self::init_locals::MaybeInitializedLocals; pub use self::liveness::MaybeLiveLocals; -pub use self::storage_liveness::{MaybeRequiresStorage, MaybeStorageLive}; +pub use self::storage_liveness::MaybeStorageLive; /// `MaybeInitializedPlaces` tracks all places that might be /// initialized upon reaching a particular point in the control flow diff --git a/src/librustc_mir/dataflow/impls/storage_liveness.rs b/src/librustc_mir/dataflow/impls/storage_liveness.rs index bbc4942030e..2a2be069b1e 100644 --- a/src/librustc_mir/dataflow/impls/storage_liveness.rs +++ b/src/librustc_mir/dataflow/impls/storage_liveness.rs @@ -1,11 +1,9 @@ pub use super::*; use crate::dataflow::BottomValue; -use crate::dataflow::{self, GenKill, Results, ResultsRefCursor}; +use crate::dataflow::{self, GenKill}; use crate::util::storage::AlwaysLiveLocals; -use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor}; use rustc_middle::mir::*; -use std::cell::RefCell; #[derive(Clone)] pub struct MaybeStorageLive { @@ -78,233 +76,3 @@ impl BottomValue for MaybeStorageLive { /// bottom = dead const BOTTOM_VALUE: bool = false; } - -type BorrowedLocalsResults<'a, 'tcx> = ResultsRefCursor<'a, 'a, 'tcx, MaybeBorrowedLocals>; - -/// Dataflow analysis that determines whether each local requires storage at a -/// given location; i.e. whether its storage can go away without being observed. -pub struct MaybeRequiresStorage<'mir, 'tcx> { - body: &'mir Body<'tcx>, - borrowed_locals: RefCell>, -} - -impl<'mir, 'tcx> MaybeRequiresStorage<'mir, 'tcx> { - pub fn new( - body: &'mir Body<'tcx>, - borrowed_locals: &'mir Results<'tcx, MaybeBorrowedLocals>, - ) -> Self { - MaybeRequiresStorage { - body, - borrowed_locals: RefCell::new(ResultsRefCursor::new(&body, borrowed_locals)), - } - } -} - -impl<'mir, 'tcx> dataflow::AnalysisDomain<'tcx> for MaybeRequiresStorage<'mir, 'tcx> { - type Idx = Local; - - const NAME: &'static str = "requires_storage"; - - fn bits_per_block(&self, body: &mir::Body<'tcx>) -> usize { - body.local_decls.len() - } - - fn initialize_start_block(&self, body: &mir::Body<'tcx>, on_entry: &mut BitSet) { - // The resume argument is live on function entry (we don't care about - // the `self` argument) - for arg in body.args_iter().skip(1) { - on_entry.insert(arg); - } - } -} - -impl<'mir, 'tcx> dataflow::GenKillAnalysis<'tcx> for MaybeRequiresStorage<'mir, 'tcx> { - fn before_statement_effect( - &self, - trans: &mut impl GenKill, - stmt: &mir::Statement<'tcx>, - loc: Location, - ) { - // If a place is borrowed in a statement, it needs storage for that statement. - self.borrowed_locals.borrow().analysis().statement_effect(trans, stmt, loc); - - match &stmt.kind { - StatementKind::StorageDead(l) => trans.kill(*l), - - // If a place is assigned to in a statement, it needs storage for that statement. - StatementKind::Assign(box (place, _)) - | StatementKind::SetDiscriminant { box place, .. } => { - trans.gen(place.local); - } - StatementKind::LlvmInlineAsm(asm) => { - for place in &*asm.outputs { - trans.gen(place.local); - } - } - - // Nothing to do for these. Match exhaustively so this fails to compile when new - // variants are added. - StatementKind::AscribeUserType(..) - | StatementKind::FakeRead(..) - | StatementKind::Nop - | StatementKind::Retag(..) - | StatementKind::StorageLive(..) => {} - } - } - - fn statement_effect( - &self, - trans: &mut impl GenKill, - _: &mir::Statement<'tcx>, - loc: Location, - ) { - // If we move from a place then only stops needing storage *after* - // that statement. - self.check_for_move(trans, loc); - } - - fn before_terminator_effect( - &self, - trans: &mut impl GenKill, - terminator: &mir::Terminator<'tcx>, - loc: Location, - ) { - // If a place is borrowed in a terminator, it needs storage for that terminator. - self.borrowed_locals.borrow().analysis().terminator_effect(trans, terminator, loc); - - match &terminator.kind { - TerminatorKind::Call { destination: Some((place, _)), .. } => { - trans.gen(place.local); - } - - // Note that we do *not* gen the `resume_arg` of `Yield` terminators. The reason for - // that is that a `yield` will return from the function, and `resume_arg` is written - // only when the generator is later resumed. Unlike `Call`, this doesn't require the - // place to have storage *before* the yield, only after. - TerminatorKind::Yield { .. } => {} - - TerminatorKind::InlineAsm { operands, .. } => { - for op in operands { - match op { - InlineAsmOperand::Out { place, .. } - | InlineAsmOperand::InOut { out_place: place, .. } => { - if let Some(place) = place { - trans.gen(place.local); - } - } - InlineAsmOperand::In { .. } - | InlineAsmOperand::Const { .. } - | InlineAsmOperand::SymFn { .. } - | InlineAsmOperand::SymStatic { .. } => {} - } - } - } - - // Nothing to do for these. Match exhaustively so this fails to compile when new - // variants are added. - TerminatorKind::Call { destination: None, .. } - | TerminatorKind::Abort - | TerminatorKind::Assert { .. } - | TerminatorKind::Drop { .. } - | TerminatorKind::DropAndReplace { .. } - | TerminatorKind::FalseEdges { .. } - | TerminatorKind::FalseUnwind { .. } - | TerminatorKind::GeneratorDrop - | TerminatorKind::Goto { .. } - | TerminatorKind::Resume - | TerminatorKind::Return - | TerminatorKind::SwitchInt { .. } - | TerminatorKind::Unreachable => {} - } - } - - fn terminator_effect( - &self, - trans: &mut impl GenKill, - terminator: &mir::Terminator<'tcx>, - loc: Location, - ) { - match &terminator.kind { - // For call terminators the destination requires storage for the call - // and after the call returns successfully, but not after a panic. - // Since `propagate_call_unwind` doesn't exist, we have to kill the - // destination here, and then gen it again in `call_return_effect`. - TerminatorKind::Call { destination: Some((place, _)), .. } => { - trans.kill(place.local); - } - - // Nothing to do for these. Match exhaustively so this fails to compile when new - // variants are added. - TerminatorKind::Call { destination: None, .. } - | TerminatorKind::Yield { .. } - | TerminatorKind::Abort - | TerminatorKind::Assert { .. } - | TerminatorKind::Drop { .. } - | TerminatorKind::DropAndReplace { .. } - | TerminatorKind::FalseEdges { .. } - | TerminatorKind::FalseUnwind { .. } - | TerminatorKind::GeneratorDrop - | TerminatorKind::Goto { .. } - | TerminatorKind::InlineAsm { .. } - | TerminatorKind::Resume - | TerminatorKind::Return - | TerminatorKind::SwitchInt { .. } - | TerminatorKind::Unreachable => {} - } - - self.check_for_move(trans, loc); - } - - fn call_return_effect( - &self, - trans: &mut impl GenKill, - _block: BasicBlock, - _func: &mir::Operand<'tcx>, - _args: &[mir::Operand<'tcx>], - return_place: mir::Place<'tcx>, - ) { - trans.gen(return_place.local); - } - - fn yield_resume_effect( - &self, - trans: &mut impl GenKill, - _resume_block: BasicBlock, - resume_place: mir::Place<'tcx>, - ) { - trans.gen(resume_place.local); - } -} - -impl<'mir, 'tcx> MaybeRequiresStorage<'mir, 'tcx> { - /// Kill locals that are fully moved and have not been borrowed. - fn check_for_move(&self, trans: &mut impl GenKill, loc: Location) { - let mut visitor = MoveVisitor { trans, borrowed_locals: &self.borrowed_locals }; - visitor.visit_location(&self.body, loc); - } -} - -impl<'mir, 'tcx> BottomValue for MaybeRequiresStorage<'mir, 'tcx> { - /// bottom = dead - const BOTTOM_VALUE: bool = false; -} - -struct MoveVisitor<'a, 'mir, 'tcx, T> { - borrowed_locals: &'a RefCell>, - trans: &'a mut T, -} - -impl<'a, 'mir, 'tcx, T> Visitor<'tcx> for MoveVisitor<'a, 'mir, 'tcx, T> -where - T: GenKill, -{ - fn visit_local(&mut self, local: &Local, context: PlaceContext, loc: Location) { - if PlaceContext::NonMutatingUse(NonMutatingUseContext::Move) == context { - let mut borrowed_locals = self.borrowed_locals.borrow_mut(); - borrowed_locals.seek_before_primary_effect(loc); - if !borrowed_locals.contains(*local) { - self.trans.kill(*local); - } - } - } -}