compiler/rustc_mir_dataflow/src/rustc_peek.rs

   1 use std::borrow::Borrow;
   2
   3 use rustc_ast::ast;
   4 use rustc_span::symbol::sym;
   5 use rustc_span::Span;
   6 use rustc_target::spec::abi::Abi;
   7
   8 use rustc_index::bit_set::BitSet;
   9 use rustc_middle::mir::MirPass;
  10 use rustc_middle::mir::{self, Body, Local, Location};
  11 use rustc_middle::ty::{self, Ty, TyCtxt};
  12
  13 use crate::impls::{
  14     DefinitelyInitializedPlaces, MaybeInitializedPlaces, MaybeLiveLocals, MaybeUninitializedPlaces,
  15 };
  16 use crate::move_paths::{HasMoveData, MoveData};
  17 use crate::move_paths::{LookupResult, MovePathIndex};
  18 use crate::MoveDataParamEnv;
  19 use crate::{Analysis, JoinSemiLattice, Results, ResultsCursor};
  20
  21 pub struct SanityCheck;
  22
  23 // FIXME: This should be a `MirLint`, but it needs to be moved back to `rustc_mir_transform` first.
  24 impl<'tcx> MirPass<'tcx> for SanityCheck {
  25     fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
  26         use crate::has_rustc_mir_with;
  27         let def_id = body.source.def_id();
  28         if !tcx.has_attr(def_id, sym::rustc_mir) {
  29             debug!("skipping rustc_peek::SanityCheck on {}", tcx.def_path_str(def_id));
  30             return;
  31         } else {
  32             debug!("running rustc_peek::SanityCheck on {}", tcx.def_path_str(def_id));
  33         }
  34
  35         let attributes = tcx.get_attrs(def_id);
  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         let sess = &tcx.sess;
  40
  41         if has_rustc_mir_with(sess, &attributes, sym::rustc_peek_maybe_init).is_some() {
  42             let flow_inits = MaybeInitializedPlaces::new(tcx, body, &mdpe)
  43                 .into_engine(tcx, body)
  44                 .iterate_to_fixpoint();
  45
  46             sanity_check_via_rustc_peek(tcx, body, &attributes, &flow_inits);
  47         }
  48
  49         if has_rustc_mir_with(sess, &attributes, sym::rustc_peek_maybe_uninit).is_some() {
  50             let flow_uninits = MaybeUninitializedPlaces::new(tcx, body, &mdpe)
  51                 .into_engine(tcx, body)
  52                 .iterate_to_fixpoint();
  53
  54             sanity_check_via_rustc_peek(tcx, body, &attributes, &flow_uninits);
  55         }
  56
  57         if has_rustc_mir_with(sess, &attributes, sym::rustc_peek_definite_init).is_some() {
  58             let flow_def_inits = DefinitelyInitializedPlaces::new(tcx, body, &mdpe)
  59                 .into_engine(tcx, body)
  60                 .iterate_to_fixpoint();
  61
  62             sanity_check_via_rustc_peek(tcx, body, &attributes, &flow_def_inits);
  63         }
  64
  65         if has_rustc_mir_with(sess, &attributes, sym::rustc_peek_liveness).is_some() {
  66             let flow_liveness = MaybeLiveLocals.into_engine(tcx, body).iterate_to_fixpoint();
  67
  68             sanity_check_via_rustc_peek(tcx, body, &attributes, &flow_liveness);
  69         }
  70
  71         if has_rustc_mir_with(sess, &attributes, sym::stop_after_dataflow).is_some() {
  72             tcx.sess.fatal("stop_after_dataflow ended compilation");
  73         }
  74     }
  75 }
  76
  77 /// This function scans `mir` for all calls to the intrinsic
  78 /// `rustc_peek` that have the expression form `rustc_peek(&expr)`.
  79 ///
  80 /// For each such call, determines what the dataflow bit-state is for
  81 /// the L-value corresponding to `expr`; if the bit-state is a 1, then
  82 /// that call to `rustc_peek` is ignored by the sanity check. If the
  83 /// bit-state is a 0, then this pass emits an error message saying
  84 /// "rustc_peek: bit not set".
  85 ///
  86 /// The intention is that one can write unit tests for dataflow by
  87 /// putting code into a UI test and using `rustc_peek` to
  88 /// make observations about the results of dataflow static analyses.
  89 ///
  90 /// (If there are any calls to `rustc_peek` that do not match the
  91 /// expression form above, then that emits an error as well, but those
  92 /// errors are not intended to be used for unit tests.)
  93 pub fn sanity_check_via_rustc_peek<'tcx, A>(
  94     tcx: TyCtxt<'tcx>,
  95     body: &Body<'tcx>,
  96     _attributes: &[ast::Attribute],
  97     results: &Results<'tcx, A>,
  98 ) where
  99     A: RustcPeekAt<'tcx>,
 100 {
 101     let def_id = body.source.def_id();
 102     debug!("sanity_check_via_rustc_peek def_id: {:?}", def_id);
 103
 104     let mut cursor = ResultsCursor::new(body, results);
 105
 106     let peek_calls = body.basic_blocks().iter_enumerated().filter_map(|(bb, block_data)| {
 107         PeekCall::from_terminator(tcx, block_data.terminator()).map(|call| (bb, block_data, call))
 108     });
 109
 110     for (bb, block_data, call) in peek_calls {
 111         // Look for a sequence like the following to indicate that we should be peeking at `_1`:
 112         //    _2 = &_1;
 113         //    rustc_peek(_2);
 114         //
 115         //    /* or */
 116         //
 117         //    _2 = _1;
 118         //    rustc_peek(_2);
 119         let (statement_index, peek_rval) = block_data
 120             .statements
 121             .iter()
 122             .enumerate()
 123             .find_map(|(i, stmt)| value_assigned_to_local(stmt, call.arg).map(|rval| (i, rval)))
 124             .expect(
 125                 "call to rustc_peek should be preceded by \
 126                     assignment to temporary holding its argument",
 127             );
 128
 129         match (call.kind, peek_rval) {
 130             (PeekCallKind::ByRef, mir::Rvalue::Ref(_, _, place))
 131             | (
 132                 PeekCallKind::ByVal,
 133                 mir::Rvalue::Use(mir::Operand::Move(place) | mir::Operand::Copy(place)),
 134             ) => {
 135                 let loc = Location { block: bb, statement_index };
 136                 cursor.seek_before_primary_effect(loc);
 137                 let state = cursor.get();
 138                 results.analysis.peek_at(tcx, *place, state, call);
 139             }
 140
 141             _ => {
 142                 let msg = "rustc_peek: argument expression \
 143                            must be either `place` or `&place`";
 144                 tcx.sess.span_err(call.span, msg);
 145             }
 146         }
 147     }
 148 }
 149
 150 /// If `stmt` is an assignment where the LHS is the given local (with no projections), returns the
 151 /// RHS of the assignment.
 152 fn value_assigned_to_local<'a, 'tcx>(
 153     stmt: &'a mir::Statement<'tcx>,
 154     local: Local,
 155 ) -> Option<&'a mir::Rvalue<'tcx>> {
 156     if let mir::StatementKind::Assign(box (place, rvalue)) = &stmt.kind {
 157         if let Some(l) = place.as_local() {
 158             if local == l {
 159                 return Some(&*rvalue);
 160             }
 161         }
 162     }
 163
 164     None
 165 }
 166
 167 #[derive(Clone, Copy, Debug)]
 168 enum PeekCallKind {
 169     ByVal,
 170     ByRef,
 171 }
 172
 173 impl PeekCallKind {
 174     fn from_arg_ty(arg: Ty<'_>) -> Self {
 175         match arg.kind() {
 176             ty::Ref(_, _, _) => PeekCallKind::ByRef,
 177             _ => PeekCallKind::ByVal,
 178         }
 179     }
 180 }
 181
 182 #[derive(Clone, Copy, Debug)]
 183 pub struct PeekCall {
 184     arg: Local,
 185     kind: PeekCallKind,
 186     span: Span,
 187 }
 188
 189 impl PeekCall {
 190     fn from_terminator<'tcx>(
 191         tcx: TyCtxt<'tcx>,
 192         terminator: &mir::Terminator<'tcx>,
 193     ) -> Option<Self> {
 194         use mir::Operand;
 195
 196         let span = terminator.source_info.span;
 197         if let mir::TerminatorKind::Call { func: Operand::Constant(func), args, .. } =
 198             &terminator.kind
 199         {
 200             if let ty::FnDef(def_id, substs) = *func.literal.ty().kind() {
 201                 let sig = tcx.fn_sig(def_id);
 202                 let name = tcx.item_name(def_id);
 203                 if sig.abi() != Abi::RustIntrinsic || name != sym::rustc_peek {
 204                     return None;
 205                 }
 206
 207                 assert_eq!(args.len(), 1);
 208                 let kind = PeekCallKind::from_arg_ty(substs.type_at(0));
 209                 let arg = match &args[0] {
 210                     Operand::Copy(place) | Operand::Move(place) => {
 211                         if let Some(local) = place.as_local() {
 212                             local
 213                         } else {
 214                             tcx.sess.diagnostic().span_err(
 215                                 span,
 216                                 "dataflow::sanity_check cannot feed a non-temp to rustc_peek.",
 217                             );
 218                             return None;
 219                         }
 220                     }
 221                     _ => {
 222                         tcx.sess.diagnostic().span_err(
 223                             span,
 224                             "dataflow::sanity_check cannot feed a non-temp to rustc_peek.",
 225                         );
 226                         return None;
 227                     }
 228                 };
 229
 230                 return Some(PeekCall { arg, kind, span });
 231             }
 232         }
 233
 234         None
 235     }
 236 }
 237
 238 pub trait RustcPeekAt<'tcx>: Analysis<'tcx> {
 239     fn peek_at(
 240         &self,
 241         tcx: TyCtxt<'tcx>,
 242         place: mir::Place<'tcx>,
 243         flow_state: &Self::Domain,
 244         call: PeekCall,
 245     );
 246 }
 247
 248 impl<'tcx, A, D> RustcPeekAt<'tcx> for A
 249 where
 250     A: Analysis<'tcx, Domain = D> + HasMoveData<'tcx>,
 251     D: JoinSemiLattice + Clone + Borrow<BitSet<MovePathIndex>>,
 252 {
 253     fn peek_at(
 254         &self,
 255         tcx: TyCtxt<'tcx>,
 256         place: mir::Place<'tcx>,
 257         flow_state: &Self::Domain,
 258         call: PeekCall,
 259     ) {
 260         match self.move_data().rev_lookup.find(place.as_ref()) {
 261             LookupResult::Exact(peek_mpi) => {
 262                 let bit_state = flow_state.borrow().contains(peek_mpi);
 263                 debug!("rustc_peek({:?} = &{:?}) bit_state: {}", call.arg, place, bit_state);
 264                 if !bit_state {
 265                     tcx.sess.span_err(call.span, "rustc_peek: bit not set");
 266                 }
 267             }
 268
 269             LookupResult::Parent(..) => {
 270                 tcx.sess.span_err(call.span, "rustc_peek: argument untracked");
 271             }
 272         }
 273     }
 274 }
 275
 276 impl<'tcx> RustcPeekAt<'tcx> for MaybeLiveLocals {
 277     fn peek_at(
 278         &self,
 279         tcx: TyCtxt<'tcx>,
 280         place: mir::Place<'tcx>,
 281         flow_state: &BitSet<Local>,
 282         call: PeekCall,
 283     ) {
 284         info!(?place, "peek_at");
 285         let Some(local) = place.as_local() else {
 286             tcx.sess.span_err(call.span, "rustc_peek: argument was not a local");
 287             return;
 288         };
 289
 290         if !flow_state.contains(local) {
 291             tcx.sess.span_err(call.span, "rustc_peek: bit not set");
 292         }
 293     }
 294 }