src/librustc_mir/transform/rustc_peek.rs

   1 use rustc_ast::ast;
   2 use rustc_span::symbol::sym;
   3 use rustc_span::Span;
   4 use rustc_target::spec::abi::Abi;
   5
   6 use crate::transform::{MirPass, MirSource};
   7 use rustc_hir::def_id::DefId;
   8 use rustc_index::bit_set::BitSet;
   9 use rustc_middle::mir::{self, Body, Local, Location};
  10 use rustc_middle::ty::{self, Ty, TyCtxt};
  11
  12 use crate::dataflow::move_paths::{HasMoveData, MoveData};
  13 use crate::dataflow::move_paths::{LookupResult, MovePathIndex};
  14 use crate::dataflow::MaybeMutBorrowedLocals;
  15 use crate::dataflow::MoveDataParamEnv;
  16 use crate::dataflow::{Analysis, Results, ResultsCursor};
  17 use crate::dataflow::{
  18     DefinitelyInitializedPlaces, MaybeInitializedPlaces, MaybeUninitializedPlaces,
  19 };
  20
  21 pub struct SanityCheck;
  22
  23 impl<'tcx> MirPass<'tcx> for SanityCheck {
  24     fn run_pass(&self, tcx: TyCtxt<'tcx>, src: MirSource<'tcx>, body: &mut Body<'tcx>) {
  25         use crate::dataflow::has_rustc_mir_with;
  26         let def_id = src.def_id();
  27         if !tcx.has_attr(def_id, sym::rustc_mir) {
  28             debug!("skipping rustc_peek::SanityCheck on {}", tcx.def_path_str(def_id));
  29             return;
  30         } else {
  31             debug!("running rustc_peek::SanityCheck on {}", tcx.def_path_str(def_id));
  32         }
  33
  34         let attributes = tcx.get_attrs(def_id);
  35         let param_env = tcx.param_env(def_id);
  36         let move_data = MoveData::gather_moves(body, tcx, param_env).unwrap();
  37         let mdpe = MoveDataParamEnv { move_data, param_env };
  38
  39         let flow_inits = MaybeInitializedPlaces::new(tcx, body, &mdpe)
  40             .into_engine(tcx, body, def_id)
  41             .iterate_to_fixpoint();
  42         let flow_uninits = MaybeUninitializedPlaces::new(tcx, body, &mdpe)
  43             .into_engine(tcx, body, def_id)
  44             .iterate_to_fixpoint();
  45         let flow_def_inits = DefinitelyInitializedPlaces::new(tcx, body, &mdpe)
  46             .into_engine(tcx, body, def_id)
  47             .iterate_to_fixpoint();
  48         let flow_mut_borrowed = MaybeMutBorrowedLocals::mut_borrows_only(tcx, body, param_env)
  49             .into_engine(tcx, body, def_id)
  50             .iterate_to_fixpoint();
  51
  52         if has_rustc_mir_with(&attributes, sym::rustc_peek_maybe_init).is_some() {
  53             sanity_check_via_rustc_peek(tcx, body, def_id, &attributes, &flow_inits);
  54         }
  55         if has_rustc_mir_with(&attributes, sym::rustc_peek_maybe_uninit).is_some() {
  56             sanity_check_via_rustc_peek(tcx, body, def_id, &attributes, &flow_uninits);
  57         }
  58         if has_rustc_mir_with(&attributes, sym::rustc_peek_definite_init).is_some() {
  59             sanity_check_via_rustc_peek(tcx, body, def_id, &attributes, &flow_def_inits);
  60         }
  61         if has_rustc_mir_with(&attributes, sym::rustc_peek_indirectly_mutable).is_some() {
  62             sanity_check_via_rustc_peek(tcx, body, def_id, &attributes, &flow_mut_borrowed);
  63         }
  64         if has_rustc_mir_with(&attributes, sym::stop_after_dataflow).is_some() {
  65             tcx.sess.fatal("stop_after_dataflow ended compilation");
  66         }
  67     }
  68 }
  69
  70 /// This function scans `mir` for all calls to the intrinsic
  71 /// `rustc_peek` that have the expression form `rustc_peek(&expr)`.
  72 ///
  73 /// For each such call, determines what the dataflow bit-state is for
  74 /// the L-value corresponding to `expr`; if the bit-state is a 1, then
  75 /// that call to `rustc_peek` is ignored by the sanity check. If the
  76 /// bit-state is a 0, then this pass emits a error message saying
  77 /// "rustc_peek: bit not set".
  78 ///
  79 /// The intention is that one can write unit tests for dataflow by
  80 /// putting code into a compile-fail test and using `rustc_peek` to
  81 /// make observations about the results of dataflow static analyses.
  82 ///
  83 /// (If there are any calls to `rustc_peek` that do not match the
  84 /// expression form above, then that emits an error as well, but those
  85 /// errors are not intended to be used for unit tests.)
  86 pub fn sanity_check_via_rustc_peek<'tcx, A>(
  87     tcx: TyCtxt<'tcx>,
  88     body: &Body<'tcx>,
  89     def_id: DefId,
  90     _attributes: &[ast::Attribute],
  91     results: &Results<'tcx, A>,
  92 ) where
  93     A: RustcPeekAt<'tcx>,
  94 {
  95     debug!("sanity_check_via_rustc_peek def_id: {:?}", def_id);
  96
  97     let mut cursor = ResultsCursor::new(body, results);
  98
  99     let peek_calls = body.basic_blocks().iter_enumerated().filter_map(|(bb, block_data)| {
 100         PeekCall::from_terminator(tcx, block_data.terminator()).map(|call| (bb, block_data, call))
 101     });
 102
 103     for (bb, block_data, call) in peek_calls {
 104         // Look for a sequence like the following to indicate that we should be peeking at `_1`:
 105         //    _2 = &_1;
 106         //    rustc_peek(_2);
 107         //
 108         //    /* or */
 109         //
 110         //    _2 = _1;
 111         //    rustc_peek(_2);
 112         let (statement_index, peek_rval) = block_data
 113             .statements
 114             .iter()
 115             .enumerate()
 116             .filter_map(|(i, stmt)| value_assigned_to_local(stmt, call.arg).map(|rval| (i, rval)))
 117             .next()
 118             .expect(
 119                 "call to rustc_peek should be preceded by \
 120                     assignment to temporary holding its argument",
 121             );
 122
 123         match (call.kind, peek_rval) {
 124             (PeekCallKind::ByRef, mir::Rvalue::Ref(_, _, place))
 125             | (
 126                 PeekCallKind::ByVal,
 127                 mir::Rvalue::Use(mir::Operand::Move(place) | mir::Operand::Copy(place)),
 128             ) => {
 129                 let loc = Location { block: bb, statement_index };
 130                 cursor.seek_before(loc);
 131                 let state = cursor.get();
 132                 results.analysis.peek_at(tcx, *place, state, call);
 133             }
 134
 135             _ => {
 136                 let msg = "rustc_peek: argument expression \
 137                            must be either `place` or `&place`";
 138                 tcx.sess.span_err(call.span, msg);
 139             }
 140         }
 141     }
 142 }
 143
 144 /// If `stmt` is an assignment where the LHS is the given local (with no projections), returns the
 145 /// RHS of the assignment.
 146 fn value_assigned_to_local<'a, 'tcx>(
 147     stmt: &'a mir::Statement<'tcx>,
 148     local: Local,
 149 ) -> Option<&'a mir::Rvalue<'tcx>> {
 150     if let mir::StatementKind::Assign(box (place, rvalue)) = &stmt.kind {
 151         if let Some(l) = place.as_local() {
 152             if local == l {
 153                 return Some(&*rvalue);
 154             }
 155         }
 156     }
 157
 158     None
 159 }
 160
 161 #[derive(Clone, Copy, Debug)]
 162 enum PeekCallKind {
 163     ByVal,
 164     ByRef,
 165 }
 166
 167 impl PeekCallKind {
 168     fn from_arg_ty(arg: Ty<'_>) -> Self {
 169         match arg.kind {
 170             ty::Ref(_, _, _) => PeekCallKind::ByRef,
 171             _ => PeekCallKind::ByVal,
 172         }
 173     }
 174 }
 175
 176 #[derive(Clone, Copy, Debug)]
 177 pub struct PeekCall {
 178     arg: Local,
 179     kind: PeekCallKind,
 180     span: Span,
 181 }
 182
 183 impl PeekCall {
 184     fn from_terminator<'tcx>(
 185         tcx: TyCtxt<'tcx>,
 186         terminator: &mir::Terminator<'tcx>,
 187     ) -> Option<Self> {
 188         use mir::Operand;
 189
 190         let span = terminator.source_info.span;
 191         if let mir::TerminatorKind::Call { func: Operand::Constant(func), args, .. } =
 192             &terminator.kind
 193         {
 194             if let ty::FnDef(def_id, substs) = func.literal.ty.kind {
 195                 let sig = tcx.fn_sig(def_id);
 196                 let name = tcx.item_name(def_id);
 197                 if sig.abi() != Abi::RustIntrinsic || name != sym::rustc_peek {
 198                     return None;
 199                 }
 200
 201                 assert_eq!(args.len(), 1);
 202                 let kind = PeekCallKind::from_arg_ty(substs.type_at(0));
 203                 let arg = match &args[0] {
 204                     Operand::Copy(place) | Operand::Move(place) => {
 205                         if let Some(local) = place.as_local() {
 206                             local
 207                         } else {
 208                             tcx.sess.diagnostic().span_err(
 209                                 span,
 210                                 "dataflow::sanity_check cannot feed a non-temp to rustc_peek.",
 211                             );
 212                             return None;
 213                         }
 214                     }
 215                     _ => {
 216                         tcx.sess.diagnostic().span_err(
 217                             span,
 218                             "dataflow::sanity_check cannot feed a non-temp to rustc_peek.",
 219                         );
 220                         return None;
 221                     }
 222                 };
 223
 224                 return Some(PeekCall { arg, kind, span });
 225             }
 226         }
 227
 228         None
 229     }
 230 }
 231
 232 pub trait RustcPeekAt<'tcx>: Analysis<'tcx> {
 233     fn peek_at(
 234         &self,
 235         tcx: TyCtxt<'tcx>,
 236         place: mir::Place<'tcx>,
 237         flow_state: &BitSet<Self::Idx>,
 238         call: PeekCall,
 239     );
 240 }
 241
 242 impl<'tcx, A> RustcPeekAt<'tcx> for A
 243 where
 244     A: Analysis<'tcx, Idx = MovePathIndex> + HasMoveData<'tcx>,
 245 {
 246     fn peek_at(
 247         &self,
 248         tcx: TyCtxt<'tcx>,
 249         place: mir::Place<'tcx>,
 250         flow_state: &BitSet<Self::Idx>,
 251         call: PeekCall,
 252     ) {
 253         match self.move_data().rev_lookup.find(place.as_ref()) {
 254             LookupResult::Exact(peek_mpi) => {
 255                 let bit_state = flow_state.contains(peek_mpi);
 256                 debug!("rustc_peek({:?} = &{:?}) bit_state: {}", call.arg, place, bit_state);
 257                 if !bit_state {
 258                     tcx.sess.span_err(call.span, "rustc_peek: bit not set");
 259                 }
 260             }
 261
 262             LookupResult::Parent(..) => {
 263                 tcx.sess.span_err(call.span, "rustc_peek: argument untracked");
 264             }
 265         }
 266     }
 267 }
 268
 269 impl<'tcx> RustcPeekAt<'tcx> for MaybeMutBorrowedLocals<'_, 'tcx> {
 270     fn peek_at(
 271         &self,
 272         tcx: TyCtxt<'tcx>,
 273         place: mir::Place<'tcx>,
 274         flow_state: &BitSet<Local>,
 275         call: PeekCall,
 276     ) {
 277         warn!("peek_at: place={:?}", place);
 278         let local = if let Some(l) = place.as_local() {
 279             l
 280         } else {
 281             tcx.sess.span_err(call.span, "rustc_peek: argument was not a local");
 282             return;
 283         };
 284
 285         if !flow_state.contains(local) {
 286             tcx.sess.span_err(call.span, "rustc_peek: bit not set");
 287         }
 288     }
 289 }