diff options
Diffstat (limited to 'compiler/rustc_mir_dataflow/src/rustc_peek.rs')
| -rw-r--r-- | compiler/rustc_mir_dataflow/src/rustc_peek.rs | 287 |
1 files changed, 287 insertions, 0 deletions
diff --git a/compiler/rustc_mir_dataflow/src/rustc_peek.rs b/compiler/rustc_mir_dataflow/src/rustc_peek.rs new file mode 100644 index 000000000..f2471f37a --- /dev/null +++ b/compiler/rustc_mir_dataflow/src/rustc_peek.rs @@ -0,0 +1,287 @@ +use rustc_span::symbol::sym; +use rustc_span::Span; + +use rustc_index::bit_set::ChunkedBitSet; +use rustc_middle::mir::MirPass; +use rustc_middle::mir::{self, Body, Local, Location}; +use rustc_middle::ty::{self, Ty, TyCtxt}; + +use crate::framework::BitSetExt; +use crate::impls::{ + DefinitelyInitializedPlaces, MaybeInitializedPlaces, MaybeLiveLocals, MaybeUninitializedPlaces, +}; +use crate::move_paths::{HasMoveData, MoveData}; +use crate::move_paths::{LookupResult, MovePathIndex}; +use crate::MoveDataParamEnv; +use crate::{Analysis, JoinSemiLattice, Results, ResultsCursor}; + +pub struct SanityCheck; + +// FIXME: This should be a `MirLint`, but it needs to be moved back to `rustc_mir_transform` first. +impl<'tcx> MirPass<'tcx> for SanityCheck { + fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { + use crate::has_rustc_mir_with; + let def_id = body.source.def_id(); + if !tcx.has_attr(def_id, sym::rustc_mir) { + debug!("skipping rustc_peek::SanityCheck on {}", tcx.def_path_str(def_id)); + return; + } else { + debug!("running rustc_peek::SanityCheck on {}", tcx.def_path_str(def_id)); + } + + let param_env = tcx.param_env(def_id); + let (_, move_data) = MoveData::gather_moves(body, tcx, param_env).unwrap(); + let mdpe = MoveDataParamEnv { move_data, param_env }; + + if has_rustc_mir_with(tcx, def_id, sym::rustc_peek_maybe_init).is_some() { + let flow_inits = MaybeInitializedPlaces::new(tcx, body, &mdpe) + .into_engine(tcx, body) + .iterate_to_fixpoint(); + + sanity_check_via_rustc_peek(tcx, body, &flow_inits); + } + + if has_rustc_mir_with(tcx, def_id, sym::rustc_peek_maybe_uninit).is_some() { + let flow_uninits = MaybeUninitializedPlaces::new(tcx, body, &mdpe) + .into_engine(tcx, body) + .iterate_to_fixpoint(); + + sanity_check_via_rustc_peek(tcx, body, &flow_uninits); + } + + if has_rustc_mir_with(tcx, def_id, sym::rustc_peek_definite_init).is_some() { + let flow_def_inits = DefinitelyInitializedPlaces::new(tcx, body, &mdpe) + .into_engine(tcx, body) + .iterate_to_fixpoint(); + + sanity_check_via_rustc_peek(tcx, body, &flow_def_inits); + } + + if has_rustc_mir_with(tcx, def_id, sym::rustc_peek_liveness).is_some() { + let flow_liveness = MaybeLiveLocals.into_engine(tcx, body).iterate_to_fixpoint(); + + sanity_check_via_rustc_peek(tcx, body, &flow_liveness); + } + + if has_rustc_mir_with(tcx, def_id, sym::stop_after_dataflow).is_some() { + tcx.sess.fatal("stop_after_dataflow ended compilation"); + } + } +} + +/// This function scans `mir` for all calls to the intrinsic +/// `rustc_peek` that have the expression form `rustc_peek(&expr)`. +/// +/// For each such call, determines what the dataflow bit-state is for +/// the L-value corresponding to `expr`; if the bit-state is a 1, then +/// that call to `rustc_peek` is ignored by the sanity check. If the +/// bit-state is a 0, then this pass emits an error message saying +/// "rustc_peek: bit not set". +/// +/// The intention is that one can write unit tests for dataflow by +/// putting code into a UI test and using `rustc_peek` to +/// make observations about the results of dataflow static analyses. +/// +/// (If there are any calls to `rustc_peek` that do not match the +/// expression form above, then that emits an error as well, but those +/// errors are not intended to be used for unit tests.) +pub fn sanity_check_via_rustc_peek<'tcx, A>( + tcx: TyCtxt<'tcx>, + body: &Body<'tcx>, + results: &Results<'tcx, A>, +) where + A: RustcPeekAt<'tcx>, +{ + let def_id = body.source.def_id(); + debug!("sanity_check_via_rustc_peek def_id: {:?}", def_id); + + let mut cursor = ResultsCursor::new(body, results); + + let peek_calls = body.basic_blocks().iter_enumerated().filter_map(|(bb, block_data)| { + PeekCall::from_terminator(tcx, block_data.terminator()).map(|call| (bb, block_data, call)) + }); + + for (bb, block_data, call) in peek_calls { + // Look for a sequence like the following to indicate that we should be peeking at `_1`: + // _2 = &_1; + // rustc_peek(_2); + // + // /* or */ + // + // _2 = _1; + // rustc_peek(_2); + let (statement_index, peek_rval) = block_data + .statements + .iter() + .enumerate() + .find_map(|(i, stmt)| value_assigned_to_local(stmt, call.arg).map(|rval| (i, rval))) + .expect( + "call to rustc_peek should be preceded by \ + assignment to temporary holding its argument", + ); + + match (call.kind, peek_rval) { + (PeekCallKind::ByRef, mir::Rvalue::Ref(_, _, place)) + | ( + PeekCallKind::ByVal, + mir::Rvalue::Use(mir::Operand::Move(place) | mir::Operand::Copy(place)), + ) => { + let loc = Location { block: bb, statement_index }; + cursor.seek_before_primary_effect(loc); + let state = cursor.get(); + results.analysis.peek_at(tcx, *place, state, call); + } + + _ => { + let msg = "rustc_peek: argument expression \ + must be either `place` or `&place`"; + tcx.sess.span_err(call.span, msg); + } + } + } +} + +/// If `stmt` is an assignment where the LHS is the given local (with no projections), returns the +/// RHS of the assignment. +fn value_assigned_to_local<'a, 'tcx>( + stmt: &'a mir::Statement<'tcx>, + local: Local, +) -> Option<&'a mir::Rvalue<'tcx>> { + if let mir::StatementKind::Assign(box (place, rvalue)) = &stmt.kind { + if let Some(l) = place.as_local() { + if local == l { + return Some(&*rvalue); + } + } + } + + None +} + +#[derive(Clone, Copy, Debug)] +enum PeekCallKind { + ByVal, + ByRef, +} + +impl PeekCallKind { + fn from_arg_ty(arg: Ty<'_>) -> Self { + match arg.kind() { + ty::Ref(_, _, _) => PeekCallKind::ByRef, + _ => PeekCallKind::ByVal, + } + } +} + +#[derive(Clone, Copy, Debug)] +pub struct PeekCall { + arg: Local, + kind: PeekCallKind, + span: Span, +} + +impl PeekCall { + fn from_terminator<'tcx>( + tcx: TyCtxt<'tcx>, + terminator: &mir::Terminator<'tcx>, + ) -> Option<Self> { + use mir::Operand; + + let span = terminator.source_info.span; + if let mir::TerminatorKind::Call { func: Operand::Constant(func), args, .. } = + &terminator.kind + { + if let ty::FnDef(def_id, substs) = *func.literal.ty().kind() { + let name = tcx.item_name(def_id); + if !tcx.is_intrinsic(def_id) || name != sym::rustc_peek { + return None; + } + + assert_eq!(args.len(), 1); + let kind = PeekCallKind::from_arg_ty(substs.type_at(0)); + let arg = match &args[0] { + Operand::Copy(place) | Operand::Move(place) => { + if let Some(local) = place.as_local() { + local + } else { + tcx.sess.diagnostic().span_err( + span, + "dataflow::sanity_check cannot feed a non-temp to rustc_peek.", + ); + return None; + } + } + _ => { + tcx.sess.diagnostic().span_err( + span, + "dataflow::sanity_check cannot feed a non-temp to rustc_peek.", + ); + return None; + } + }; + + return Some(PeekCall { arg, kind, span }); + } + } + + None + } +} + +pub trait RustcPeekAt<'tcx>: Analysis<'tcx> { + fn peek_at( + &self, + tcx: TyCtxt<'tcx>, + place: mir::Place<'tcx>, + flow_state: &Self::Domain, + call: PeekCall, + ); +} + +impl<'tcx, A, D> RustcPeekAt<'tcx> for A +where + A: Analysis<'tcx, Domain = D> + HasMoveData<'tcx>, + D: JoinSemiLattice + Clone + BitSetExt<MovePathIndex>, +{ + fn peek_at( + &self, + tcx: TyCtxt<'tcx>, + place: mir::Place<'tcx>, + flow_state: &Self::Domain, + call: PeekCall, + ) { + match self.move_data().rev_lookup.find(place.as_ref()) { + LookupResult::Exact(peek_mpi) => { + let bit_state = flow_state.contains(peek_mpi); + debug!("rustc_peek({:?} = &{:?}) bit_state: {}", call.arg, place, bit_state); + if !bit_state { + tcx.sess.span_err(call.span, "rustc_peek: bit not set"); + } + } + + LookupResult::Parent(..) => { + tcx.sess.span_err(call.span, "rustc_peek: argument untracked"); + } + } + } +} + +impl<'tcx> RustcPeekAt<'tcx> for MaybeLiveLocals { + fn peek_at( + &self, + tcx: TyCtxt<'tcx>, + place: mir::Place<'tcx>, + flow_state: &ChunkedBitSet<Local>, + call: PeekCall, + ) { + info!(?place, "peek_at"); + let Some(local) = place.as_local() else { + tcx.sess.span_err(call.span, "rustc_peek: argument was not a local"); + return; + }; + + if !flow_state.contains(local) { + tcx.sess.span_err(call.span, "rustc_peek: bit not set"); + } + } +} |