compiler/rustc_mir_dataflow/src/rustc_peek.rs

   1 use rustc_span::symbol::sym;
   2 use rustc_span::Span;
   3
   4 use rustc_index::bit_set::ChunkedBitSet;
   5 use rustc_middle::mir::MirPass;
   6 use rustc_middle::mir::{self, Body, Local, Location};
   7 use rustc_middle::ty::{self, Ty, TyCtxt};
   8
   9 use crate::errors::{
  10     PeekArgumentNotALocal, PeekArgumentUntracked, PeekBitNotSet, PeekMustBeNotTemporary,
  11     PeekMustBePlaceOrRefPlace, StopAfterDataFlowEndedCompilation,
  12 };
  13 use crate::framework::BitSetExt;
  14 use crate::impls::{
  15     DefinitelyInitializedPlaces, MaybeInitializedPlaces, MaybeLiveLocals, MaybeUninitializedPlaces,
  16 };
  17 use crate::move_paths::{HasMoveData, MoveData};
  18 use crate::move_paths::{LookupResult, MovePathIndex};
  19 use crate::MoveDataParamEnv;
  20 use crate::{Analysis, JoinSemiLattice, Results, ResultsCursor};
  21
  22 pub struct SanityCheck;
  23
  24 // FIXME: This should be a `MirLint`, but it needs to be moved back to `rustc_mir_transform` first.
  25 impl<'tcx> MirPass<'tcx> for SanityCheck {
  26     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
  27         use crate::has_rustc_mir_with;
  28         let def_id = body.source.def_id();
  29         if !tcx.has_attr(def_id, sym::rustc_mir) {
  30             debug!("skipping rustc_peek::SanityCheck on {}", tcx.def_path_str(def_id));
  31             return;
  32         } else {
  33             debug!("running rustc_peek::SanityCheck on {}", tcx.def_path_str(def_id));
  34         }
  35
  36         let param_env = tcx.param_env(def_id);
  37         let (_, move_data) = MoveData::gather_moves(body, tcx, param_env).unwrap();
  38         let mdpe = MoveDataParamEnv { move_data, param_env };
  39
  40         if has_rustc_mir_with(tcx, def_id, sym::rustc_peek_maybe_init).is_some() {
  41             let flow_inits = MaybeInitializedPlaces::new(tcx, body, &mdpe)
  42                 .into_engine(tcx, body)
  43                 .iterate_to_fixpoint();
  44
  45             sanity_check_via_rustc_peek(tcx, body, &flow_inits);
  46         }
  47
  48         if has_rustc_mir_with(tcx, def_id, sym::rustc_peek_maybe_uninit).is_some() {
  49             let flow_uninits = MaybeUninitializedPlaces::new(tcx, body, &mdpe)
  50                 .into_engine(tcx, body)
  51                 .iterate_to_fixpoint();
  52
  53             sanity_check_via_rustc_peek(tcx, body, &flow_uninits);
  54         }
  55
  56         if has_rustc_mir_with(tcx, def_id, sym::rustc_peek_definite_init).is_some() {
  57             let flow_def_inits = DefinitelyInitializedPlaces::new(tcx, body, &mdpe)
  58                 .into_engine(tcx, body)
  59                 .iterate_to_fixpoint();
  60
  61             sanity_check_via_rustc_peek(tcx, body, &flow_def_inits);
  62         }
  63
  64         if has_rustc_mir_with(tcx, def_id, sym::rustc_peek_liveness).is_some() {
  65             let flow_liveness = MaybeLiveLocals.into_engine(tcx, body).iterate_to_fixpoint();
  66
  67             sanity_check_via_rustc_peek(tcx, body, &flow_liveness);
  68         }
  69
  70         if has_rustc_mir_with(tcx, def_id, sym::stop_after_dataflow).is_some() {
  71             tcx.sess.emit_fatal(StopAfterDataFlowEndedCompilation);
  72         }
  73     }
  74 }
  75
  76 /// This function scans `mir` for all calls to the intrinsic
  77 /// `rustc_peek` that have the expression form `rustc_peek(&expr)`.
  78 ///
  79 /// For each such call, determines what the dataflow bit-state is for
  80 /// the L-value corresponding to `expr`; if the bit-state is a 1, then
  81 /// that call to `rustc_peek` is ignored by the sanity check. If the
  82 /// bit-state is a 0, then this pass emits an error message saying
  83 /// "rustc_peek: bit not set".
  84 ///
  85 /// The intention is that one can write unit tests for dataflow by
  86 /// putting code into a UI test and using `rustc_peek` to
  87 /// make observations about the results of dataflow static analyses.
  88 ///
  89 /// (If there are any calls to `rustc_peek` that do not match the
  90 /// expression form above, then that emits an error as well, but those
  91 /// errors are not intended to be used for unit tests.)
  92 pub fn sanity_check_via_rustc_peek<'tcx, A>(
  93     tcx: TyCtxt<'tcx>,
  94     body: &Body<'tcx>,
  95     results: &Results<'tcx, A>,
  96 ) where
  97     A: RustcPeekAt<'tcx>,
  98 {
  99     let def_id = body.source.def_id();
 100     debug!("sanity_check_via_rustc_peek def_id: {:?}", def_id);
 101
 102     let mut cursor = ResultsCursor::new(body, results);
 103
 104     let peek_calls = body.basic_blocks.iter_enumerated().filter_map(|(bb, block_data)| {
 105         PeekCall::from_terminator(tcx, block_data.terminator()).map(|call| (bb, block_data, call))
 106     });
 107
 108     for (bb, block_data, call) in peek_calls {
 109         // Look for a sequence like the following to indicate that we should be peeking at `_1`:
 110         //    _2 = &_1;
 111         //    rustc_peek(_2);
 112         //
 113         //    /* or */
 114         //
 115         //    _2 = _1;
 116         //    rustc_peek(_2);
 117         let (statement_index, peek_rval) = block_data
 118             .statements
 119             .iter()
 120             .enumerate()
 121             .find_map(|(i, stmt)| value_assigned_to_local(stmt, call.arg).map(|rval| (i, rval)))
 122             .expect(
 123                 "call to rustc_peek should be preceded by \
 124                     assignment to temporary holding its argument",
 125             );
 126
 127         match (call.kind, peek_rval) {
 128             (PeekCallKind::ByRef, mir::Rvalue::Ref(_, _, place))
 129             | (
 130                 PeekCallKind::ByVal,
 131                 mir::Rvalue::Use(mir::Operand::Move(place) | mir::Operand::Copy(place)),
 132             ) => {
 133                 let loc = Location { block: bb, statement_index };
 134                 cursor.seek_before_primary_effect(loc);
 135                 let state = cursor.get();
 136                 results.analysis.peek_at(tcx, *place, state, call);
 137             }
 138
 139             _ => {
 140                 tcx.sess.emit_err(PeekMustBePlaceOrRefPlace { span: call.span });
 141             }
 142         }
 143     }
 144 }
 145
 146 /// If `stmt` is an assignment where the LHS is the given local (with no projections), returns the
 147 /// RHS of the assignment.
 148 fn value_assigned_to_local<'a, 'tcx>(
 149     stmt: &'a mir::Statement<'tcx>,
 150     local: Local,
 151 ) -> Option<&'a mir::Rvalue<'tcx>> {
 152     if let mir::StatementKind::Assign(box (place, rvalue)) = &stmt.kind {
 153         if let Some(l) = place.as_local() {
 154             if local == l {
 155                 return Some(&*rvalue);
 156             }
 157         }
 158     }
 159
 160     None
 161 }
 162
 163 #[derive(Clone, Copy, Debug)]
 164 enum PeekCallKind {
 165     ByVal,
 166     ByRef,
 167 }
 168
 169 impl PeekCallKind {
 170     fn from_arg_ty(arg: Ty<'_>) -> Self {
 171         match arg.kind() {
 172             ty::Ref(_, _, _) => PeekCallKind::ByRef,
 173             _ => PeekCallKind::ByVal,
 174         }
 175     }
 176 }
 177
 178 #[derive(Clone, Copy, Debug)]
 179 pub struct PeekCall {
 180     arg: Local,
 181     kind: PeekCallKind,
 182     span: Span,
 183 }
 184
 185 impl PeekCall {
 186     fn from_terminator<'tcx>(
 187         tcx: TyCtxt<'tcx>,
 188         terminator: &mir::Terminator<'tcx>,
 189     ) -> Option<Self> {
 190         use mir::Operand;
 191
 192         let span = terminator.source_info.span;
 193         if let mir::TerminatorKind::Call { func: Operand::Constant(func), args, .. } =
 194             &terminator.kind
 195         {
 196             if let ty::FnDef(def_id, substs) = *func.literal.ty().kind() {
 197                 let name = tcx.item_name(def_id);
 198                 if !tcx.is_intrinsic(def_id) || name != sym::rustc_peek {
 199                     return None;
 200                 }
 201
 202                 assert_eq!(args.len(), 1);
 203                 let kind = PeekCallKind::from_arg_ty(substs.type_at(0));
 204                 let arg = match &args[0] {
 205                     Operand::Copy(place) | Operand::Move(place) => {
 206                         if let Some(local) = place.as_local() {
 207                             local
 208                         } else {
 209                             tcx.sess.emit_err(PeekMustBeNotTemporary { span });
 210                             return None;
 211                         }
 212                     }
 213                     _ => {
 214                         tcx.sess.emit_err(PeekMustBeNotTemporary { span });
 215                         return None;
 216                     }
 217                 };
 218
 219                 return Some(PeekCall { arg, kind, span });
 220             }
 221         }
 222
 223         None
 224     }
 225 }
 226
 227 pub trait RustcPeekAt<'tcx>: Analysis<'tcx> {
 228     fn peek_at(
 229         &self,
 230         tcx: TyCtxt<'tcx>,
 231         place: mir::Place<'tcx>,
 232         flow_state: &Self::Domain,
 233         call: PeekCall,
 234     );
 235 }
 236
 237 impl<'tcx, A, D> RustcPeekAt<'tcx> for A
 238 where
 239     A: Analysis<'tcx, Domain = D> + HasMoveData<'tcx>,
 240     D: JoinSemiLattice + Clone + BitSetExt<MovePathIndex>,
 241 {
 242     fn peek_at(
 243         &self,
 244         tcx: TyCtxt<'tcx>,
 245         place: mir::Place<'tcx>,
 246         flow_state: &Self::Domain,
 247         call: PeekCall,
 248     ) {
 249         match self.move_data().rev_lookup.find(place.as_ref()) {
 250             LookupResult::Exact(peek_mpi) => {
 251                 let bit_state = flow_state.contains(peek_mpi);
 252                 debug!("rustc_peek({:?} = &{:?}) bit_state: {}", call.arg, place, bit_state);
 253                 if !bit_state {
 254                     tcx.sess.emit_err(PeekBitNotSet { span: call.span });
 255                 }
 256             }
 257
 258             LookupResult::Parent(..) => {
 259                 tcx.sess.emit_err(PeekArgumentUntracked { span: call.span });
 260             }
 261         }
 262     }
 263 }
 264
 265 impl<'tcx> RustcPeekAt<'tcx> for MaybeLiveLocals {
 266     fn peek_at(
 267         &self,
 268         tcx: TyCtxt<'tcx>,
 269         place: mir::Place<'tcx>,
 270         flow_state: &ChunkedBitSet<Local>,
 271         call: PeekCall,
 272     ) {
 273         info!(?place, "peek_at");
 274         let Some(local) = place.as_local() else {
 275             tcx.sess.emit_err(PeekArgumentNotALocal { span: call.span });
 276             return;
 277         };
 278
 279         if !flow_state.contains(local) {
 280             tcx.sess.emit_err(PeekBitNotSet { span: call.span });
 281         }
 282     }
 283 }