src/librustc_mir/transform/rustc_peek.rs

use rustc_target::spec::abi::{Abi};
use syntax::ast;
use syntax::symbol::sym;
use syntax_pos::Span;

use rustc::ty::{self, TyCtxt};
use rustc::hir::def_id::DefId;
use rustc::mir::{self, Body, Location};
use rustc_data_structures::bit_set::BitSet;
use crate::transform::{MirPass, MirSource};

use crate::dataflow::{do_dataflow, DebugFormatted};
use crate::dataflow::MoveDataParamEnv;
use crate::dataflow::BitDenotation;
use crate::dataflow::DataflowResults;
use crate::dataflow::{
    DefinitelyInitializedPlaces, MaybeInitializedPlaces, MaybeUninitializedPlaces
};
use crate::dataflow::move_paths::{MovePathIndex, LookupResult};
use crate::dataflow::move_paths::{HasMoveData, MoveData};

use crate::dataflow::has_rustc_mir_with;

pub struct SanityCheck;

impl<'tcx> MirPass<'tcx> for SanityCheck {
    fn run_pass(&self, tcx: TyCtxt<'tcx>, src: MirSource<'tcx>, body: &mut Body<'tcx>) {
        let def_id = src.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 attributes = tcx.get_attrs(def_id);
        let param_env = tcx.param_env(def_id);
        let move_data = MoveData::gather_moves(body, tcx).unwrap();
        let mdpe = MoveDataParamEnv { move_data: move_data, param_env: param_env };
        let dead_unwinds = BitSet::new_empty(body.basic_blocks().len());
        let flow_inits =
            do_dataflow(tcx, body, def_id, &attributes, &dead_unwinds,
                        MaybeInitializedPlaces::new(tcx, body, &mdpe),
                        |bd, i| DebugFormatted::new(&bd.move_data().move_paths[i]));
        let flow_uninits =
            do_dataflow(tcx, body, def_id, &attributes, &dead_unwinds,
                        MaybeUninitializedPlaces::new(tcx, body, &mdpe),
                        |bd, i| DebugFormatted::new(&bd.move_data().move_paths[i]));
        let flow_def_inits =
            do_dataflow(tcx, body, def_id, &attributes, &dead_unwinds,
                        DefinitelyInitializedPlaces::new(tcx, body, &mdpe),
                        |bd, i| DebugFormatted::new(&bd.move_data().move_paths[i]));

        if has_rustc_mir_with(&attributes, sym::rustc_peek_maybe_init).is_some() {
            sanity_check_via_rustc_peek(tcx, body, def_id, &attributes, &flow_inits);
        }
        if has_rustc_mir_with(&attributes, sym::rustc_peek_maybe_uninit).is_some() {
            sanity_check_via_rustc_peek(tcx, body, def_id, &attributes, &flow_uninits);
        }
        if has_rustc_mir_with(&attributes, sym::rustc_peek_definite_init).is_some() {
            sanity_check_via_rustc_peek(tcx, body, def_id, &attributes, &flow_def_inits);
        }
        if has_rustc_mir_with(&attributes, 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 a error message saying
/// "rustc_peek: bit not set".
///
/// The intention is that one can write unit tests for dataflow by
/// putting code into a compile-fail 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, O>(
    tcx: TyCtxt<'tcx>,
    body: &Body<'tcx>,
    def_id: DefId,
    _attributes: &[ast::Attribute],
    results: &DataflowResults<'tcx, O>,
) where
    O: BitDenotation<'tcx, Idx = MovePathIndex> + HasMoveData<'tcx>,
{
    debug!("sanity_check_via_rustc_peek def_id: {:?}", def_id);
    // FIXME: this is not DRY. Figure out way to abstract this and
    // `dataflow::build_sets`. (But note it is doing non-standard
    // stuff, so such generalization may not be realistic.)

    for bb in body.basic_blocks().indices() {
        each_block(tcx, body, results, bb);
    }
}

fn each_block<'tcx, O>(
    tcx: TyCtxt<'tcx>,
    body: &Body<'tcx>,
    results: &DataflowResults<'tcx, O>,
    bb: mir::BasicBlock,
) where
    O: BitDenotation<'tcx, Idx = MovePathIndex> + HasMoveData<'tcx>,
{
    let move_data = results.0.operator.move_data();
    let mir::BasicBlockData { ref statements, ref terminator, is_cleanup: _ } = body[bb];

    let (args, span) = match is_rustc_peek(tcx, terminator) {
        Some(args_and_span) => args_and_span,
        None => return,
    };
    assert!(args.len() == 1);
    let peek_arg_place = match args[0] {
        mir::Operand::Copy(ref place @ mir::Place {
            base: mir::PlaceBase::Local(_),
            projection: None,
        }) |
        mir::Operand::Move(ref place @ mir::Place {
            base: mir::PlaceBase::Local(_),
            projection: None,
        }) => Some(place),
        _ => None,
    };

    let peek_arg_place = match peek_arg_place {
        Some(arg) => arg,
        None => {
            tcx.sess.diagnostic().span_err(
                span, "dataflow::sanity_check cannot feed a non-temp to rustc_peek.");
            return;
        }
    };

    let mut on_entry = results.0.sets.entry_set_for(bb.index()).to_owned();
    let mut trans = results.0.sets.trans_for(bb.index()).clone();

    // Emulate effect of all statements in the block up to (but not
    // including) the borrow within `peek_arg_place`. Do *not* include
    // call to `peek_arg_place` itself (since we are peeking the state
    // of the argument at time immediate preceding Call to
    // `rustc_peek`).

    for (j, stmt) in statements.iter().enumerate() {
        debug!("rustc_peek: ({:?},{}) {:?}", bb, j, stmt);
        let (place, rvalue) = match stmt.kind {
            mir::StatementKind::Assign(ref place, ref rvalue) => {
                (place, rvalue)
            }
            mir::StatementKind::FakeRead(..) |
            mir::StatementKind::StorageLive(_) |
            mir::StatementKind::StorageDead(_) |
            mir::StatementKind::InlineAsm { .. } |
            mir::StatementKind::Retag { .. } |
            mir::StatementKind::AscribeUserType(..) |
            mir::StatementKind::Nop => continue,
            mir::StatementKind::SetDiscriminant{ .. } =>
                span_bug!(stmt.source_info.span,
                          "sanity_check should run before Deaggregator inserts SetDiscriminant"),
        };

        if place == peek_arg_place {
            if let mir::Rvalue::Ref(_, mir::BorrowKind::Shared, ref peeking_at_place) = **rvalue {
                // Okay, our search is over.
                match move_data.rev_lookup.find(peeking_at_place.as_ref()) {
                    LookupResult::Exact(peek_mpi) => {
                        let bit_state = on_entry.contains(peek_mpi);
                        debug!("rustc_peek({:?} = &{:?}) bit_state: {}",
                               place, peeking_at_place, bit_state);
                        if !bit_state {
                            tcx.sess.span_err(span, "rustc_peek: bit not set");
                        }
                    }
                    LookupResult::Parent(..) => {
                        tcx.sess.span_err(span, "rustc_peek: argument untracked");
                    }
                }
                return;
            } else {
                // Our search should have been over, but the input
                // does not match expectations of `rustc_peek` for
                // this sanity_check.
                let msg = "rustc_peek: argument expression \
                           must be immediate borrow of form `&expr`";
                tcx.sess.span_err(span, msg);
            }
        }

        let lhs_mpi = move_data.rev_lookup.find(place.as_ref());

        debug!("rustc_peek: computing effect on place: {:?} ({:?}) in stmt: {:?}",
               place, lhs_mpi, stmt);
        // reset GEN and KILL sets before emulating their effect.
        trans.clear();
        results.0.operator.before_statement_effect(
            &mut trans,
            Location { block: bb, statement_index: j });
        results.0.operator.statement_effect(
            &mut trans,
            Location { block: bb, statement_index: j });
        trans.apply(&mut on_entry);
    }

    results.0.operator.before_terminator_effect(
        &mut trans,
        Location { block: bb, statement_index: statements.len() });

    tcx.sess.span_err(span, &format!("rustc_peek: MIR did not match \
                                      anticipated pattern; note that \
                                      rustc_peek expects input of \
                                      form `&expr`"));
}

fn is_rustc_peek<'a, 'tcx>(
    tcx: TyCtxt<'tcx>,
    terminator: &'a Option<mir::Terminator<'tcx>>,
) -> Option<(&'a [mir::Operand<'tcx>], Span)> {
    if let Some(mir::Terminator { ref kind, source_info, .. }) = *terminator {
        if let mir::TerminatorKind::Call { func: ref oper, ref args, .. } = *kind {
            if let mir::Operand::Constant(ref func) = *oper {
                if let ty::FnDef(def_id, _) = func.literal.ty.sty {
                    let abi = tcx.fn_sig(def_id).abi();
                    let name = tcx.item_name(def_id);
                    if abi == Abi::RustIntrinsic && name == sym::rustc_peek {
                        return Some((args, source_info.span));
                    }
                }
            }
        }
    }
    return None;
}