1 files changed, 422 insertions, 0 deletions
diff --git a/compiler/rustc_mir_dataflow/src/move_paths/mod.rs b/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
new file mode 100644
index 000000000..a951c5b0b
--- /dev/null
+++ b/compiler/rustc_mir_dataflow/src/move_paths/mod.rs
@@ -0,0 +1,422 @@
+use crate::move_paths::builder::MoveDat;
+use rustc_data_structures::fx::FxHashMap;
+use rustc_index::vec::IndexVec;
+use rustc_middle::mir::*;
+use rustc_middle::ty::{ParamEnv, Ty, TyCtxt};
+use rustc_span::Span;
+use smallvec::SmallVec;
+
+use std::fmt;
+use std::ops::{Index, IndexMut};
+
+use self::abs_domain::{AbstractElem, Lift};
+
+mod abs_domain;
+
+rustc_index::newtype_index! {
+    pub struct MovePathIndex {
+        DEBUG_FORMAT = "mp{}"
+    }
+}
+
+impl polonius_engine::Atom for MovePathIndex {
+    fn index(self) -> usize {
+        rustc_index::vec::Idx::index(self)
+    }
+}
+
+rustc_index::newtype_index! {
+    pub struct MoveOutIndex {
+        DEBUG_FORMAT = "mo{}"
+    }
+}
+
+rustc_index::newtype_index! {
+    pub struct InitIndex {
+        DEBUG_FORMAT = "in{}"
+    }
+}
+
+impl MoveOutIndex {
+    pub fn move_path_index(self, move_data: &MoveData<'_>) -> MovePathIndex {
+        move_data.moves[self].path
+    }
+}
+
+/// `MovePath` is a canonicalized representation of a path that is
+/// moved or assigned to.
+///
+/// It follows a tree structure.
+///
+/// Given `struct X { m: M, n: N }` and `x: X`, moves like `drop x.m;`
+/// move *out* of the place `x.m`.
+///
+/// The MovePaths representing `x.m` and `x.n` are siblings (that is,
+/// one of them will link to the other via the `next_sibling` field,
+/// and the other will have no entry in its `next_sibling` field), and
+/// they both have the MovePath representing `x` as their parent.
+#[derive(Clone)]
+pub struct MovePath<'tcx> {
+    pub next_sibling: Option<MovePathIndex>,
+    pub first_child: Option<MovePathIndex>,
+    pub parent: Option<MovePathIndex>,
+    pub place: Place<'tcx>,
+}
+
+impl<'tcx> MovePath<'tcx> {
+    /// Returns an iterator over the parents of `self`.
+    pub fn parents<'a>(
+        &self,
+        move_paths: &'a IndexVec<MovePathIndex, MovePath<'tcx>>,
+    ) -> impl 'a + Iterator<Item = (MovePathIndex, &'a MovePath<'tcx>)> {
+        let first = self.parent.map(|mpi| (mpi, &move_paths[mpi]));
+        MovePathLinearIter {
+            next: first,
+            fetch_next: move |_, parent: &MovePath<'_>| {
+                parent.parent.map(|mpi| (mpi, &move_paths[mpi]))
+            },
+        }
+    }
+
+    /// Returns an iterator over the immediate children of `self`.
+    pub fn children<'a>(
+        &self,
+        move_paths: &'a IndexVec<MovePathIndex, MovePath<'tcx>>,
+    ) -> impl 'a + Iterator<Item = (MovePathIndex, &'a MovePath<'tcx>)> {
+        let first = self.first_child.map(|mpi| (mpi, &move_paths[mpi]));
+        MovePathLinearIter {
+            next: first,
+            fetch_next: move |_, child: &MovePath<'_>| {
+                child.next_sibling.map(|mpi| (mpi, &move_paths[mpi]))
+            },
+        }
+    }
+
+    /// Finds the closest descendant of `self` for which `f` returns `true` using a breadth-first
+    /// search.
+    ///
+    /// `f` will **not** be called on `self`.
+    pub fn find_descendant(
+        &self,
+        move_paths: &IndexVec<MovePathIndex, MovePath<'_>>,
+        f: impl Fn(MovePathIndex) -> bool,
+    ) -> Option<MovePathIndex> {
+        let mut todo = if let Some(child) = self.first_child {
+            vec![child]
+        } else {
+            return None;
+        };
+
+        while let Some(mpi) = todo.pop() {
+            if f(mpi) {
+                return Some(mpi);
+            }
+
+            let move_path = &move_paths[mpi];
+            if let Some(child) = move_path.first_child {
+                todo.push(child);
+            }
+
+            // After we've processed the original `mpi`, we should always
+            // traverse the siblings of any of its children.
+            if let Some(sibling) = move_path.next_sibling {
+                todo.push(sibling);
+            }
+        }
+
+        None
+    }
+}
+
+impl<'tcx> fmt::Debug for MovePath<'tcx> {
+    fn fmt(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(w, "MovePath {{")?;
+        if let Some(parent) = self.parent {
+            write!(w, " parent: {:?},", parent)?;
+        }
+        if let Some(first_child) = self.first_child {
+            write!(w, " first_child: {:?},", first_child)?;
+        }
+        if let Some(next_sibling) = self.next_sibling {
+            write!(w, " next_sibling: {:?}", next_sibling)?;
+        }
+        write!(w, " place: {:?} }}", self.place)
+    }
+}
+
+impl<'tcx> fmt::Display for MovePath<'tcx> {
+    fn fmt(&self, w: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(w, "{:?}", self.place)
+    }
+}
+
+struct MovePathLinearIter<'a, 'tcx, F> {
+    next: Option<(MovePathIndex, &'a MovePath<'tcx>)>,
+    fetch_next: F,
+}
+
+impl<'a, 'tcx, F> Iterator for MovePathLinearIter<'a, 'tcx, F>
+where
+    F: FnMut(MovePathIndex, &'a MovePath<'tcx>) -> Option<(MovePathIndex, &'a MovePath<'tcx>)>,
+{
+    type Item = (MovePathIndex, &'a MovePath<'tcx>);
+
+    fn next(&mut self) -> Option<Self::Item> {
+        let ret = self.next.take()?;
+        self.next = (self.fetch_next)(ret.0, ret.1);
+        Some(ret)
+    }
+}
+
+#[derive(Debug)]
+pub struct MoveData<'tcx> {
+    pub move_paths: IndexVec<MovePathIndex, MovePath<'tcx>>,
+    pub moves: IndexVec<MoveOutIndex, MoveOut>,
+    /// Each Location `l` is mapped to the MoveOut's that are effects
+    /// of executing the code at `l`. (There can be multiple MoveOut's
+    /// for a given `l` because each MoveOut is associated with one
+    /// particular path being moved.)
+    pub loc_map: LocationMap<SmallVec<[MoveOutIndex; 4]>>,
+    pub path_map: IndexVec<MovePathIndex, SmallVec<[MoveOutIndex; 4]>>,
+    pub rev_lookup: MovePathLookup,
+    pub inits: IndexVec<InitIndex, Init>,
+    /// Each Location `l` is mapped to the Inits that are effects
+    /// of executing the code at `l`.
+    pub init_loc_map: LocationMap<SmallVec<[InitIndex; 4]>>,
+    pub init_path_map: IndexVec<MovePathIndex, SmallVec<[InitIndex; 4]>>,
+}
+
+pub trait HasMoveData<'tcx> {
+    fn move_data(&self) -> &MoveData<'tcx>;
+}
+
+#[derive(Debug)]
+pub struct LocationMap<T> {
+    /// Location-indexed (BasicBlock for outer index, index within BB
+    /// for inner index) map.
+    pub(crate) map: IndexVec<BasicBlock, Vec<T>>,
+}
+
+impl<T> Index<Location> for LocationMap<T> {
+    type Output = T;
+    fn index(&self, index: Location) -> &Self::Output {
+        &self.map[index.block][index.statement_index]
+    }
+}
+
+impl<T> IndexMut<Location> for LocationMap<T> {
+    fn index_mut(&mut self, index: Location) -> &mut Self::Output {
+        &mut self.map[index.block][index.statement_index]
+    }
+}
+
+impl<T> LocationMap<T>
+where
+    T: Default + Clone,
+{
+    fn new(body: &Body<'_>) -> Self {
+        LocationMap {
+            map: body
+                .basic_blocks()
+                .iter()
+                .map(|block| vec![T::default(); block.statements.len() + 1])
+                .collect(),
+        }
+    }
+}
+
+/// `MoveOut` represents a point in a program that moves out of some
+/// L-value; i.e., "creates" uninitialized memory.
+///
+/// With respect to dataflow analysis:
+/// - Generated by moves and declaration of uninitialized variables.
+/// - Killed by assignments to the memory.
+#[derive(Copy, Clone)]
+pub struct MoveOut {
+    /// path being moved
+    pub path: MovePathIndex,
+    /// location of move
+    pub source: Location,
+}
+
+impl fmt::Debug for MoveOut {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(fmt, "{:?}@{:?}", self.path, self.source)
+    }
+}
+
+/// `Init` represents a point in a program that initializes some L-value;
+#[derive(Copy, Clone)]
+pub struct Init {
+    /// path being initialized
+    pub path: MovePathIndex,
+    /// location of initialization
+    pub location: InitLocation,
+    /// Extra information about this initialization
+    pub kind: InitKind,
+}
+
+/// Initializations can be from an argument or from a statement. Arguments
+/// do not have locations, in those cases the `Local` is kept..
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum InitLocation {
+    Argument(Local),
+    Statement(Location),
+}
+
+/// Additional information about the initialization.
+#[derive(Copy, Clone, Debug, PartialEq, Eq)]
+pub enum InitKind {
+    /// Deep init, even on panic
+    Deep,
+    /// Only does a shallow init
+    Shallow,
+    /// This doesn't initialize the variable on panic (and a panic is possible).
+    NonPanicPathOnly,
+}
+
+impl fmt::Debug for Init {
+    fn fmt(&self, fmt: &mut fmt::Formatter<'_>) -> fmt::Result {
+        write!(fmt, "{:?}@{:?} ({:?})", self.path, self.location, self.kind)
+    }
+}
+
+impl Init {
+    pub fn span<'tcx>(&self, body: &Body<'tcx>) -> Span {
+        match self.location {
+            InitLocation::Argument(local) => body.local_decls[local].source_info.span,
+            InitLocation::Statement(location) => body.source_info(location).span,
+        }
+    }
+}
+
+/// Tables mapping from a place to its MovePathIndex.
+#[derive(Debug)]
+pub struct MovePathLookup {
+    locals: IndexVec<Local, MovePathIndex>,
+
+    /// projections are made from a base-place and a projection
+    /// elem. The base-place will have a unique MovePathIndex; we use
+    /// the latter as the index into the outer vector (narrowing
+    /// subsequent search so that it is solely relative to that
+    /// base-place). For the remaining lookup, we map the projection
+    /// elem to the associated MovePathIndex.
+    projections: FxHashMap<(MovePathIndex, AbstractElem), MovePathIndex>,
+}
+
+mod builder;
+
+#[derive(Copy, Clone, Debug)]
+pub enum LookupResult {
+    Exact(MovePathIndex),
+    Parent(Option<MovePathIndex>),
+}
+
+impl MovePathLookup {
+    // Unlike the builder `fn move_path_for` below, this lookup
+    // alternative will *not* create a MovePath on the fly for an
+    // unknown place, but will rather return the nearest available
+    // parent.
+    pub fn find(&self, place: PlaceRef<'_>) -> LookupResult {
+        let mut result = self.locals[place.local];
+
+        for elem in place.projection.iter() {
+            if let Some(&subpath) = self.projections.get(&(result, elem.lift())) {
+                result = subpath;
+            } else {
+                return LookupResult::Parent(Some(result));
+            }
+        }
+
+        LookupResult::Exact(result)
+    }
+
+    pub fn find_local(&self, local: Local) -> MovePathIndex {
+        self.locals[local]
+    }
+
+    /// An enumerated iterator of `local`s and their associated
+    /// `MovePathIndex`es.
+    pub fn iter_locals_enumerated(
+        &self,
+    ) -> impl DoubleEndedIterator<Item = (Local, MovePathIndex)> + ExactSizeIterator + '_ {
+        self.locals.iter_enumerated().map(|(l, &idx)| (l, idx))
+    }
+}
+
+#[derive(Debug)]
+pub struct IllegalMoveOrigin<'tcx> {
+    pub location: Location,
+    pub kind: IllegalMoveOriginKind<'tcx>,
+}
+
+#[derive(Debug)]
+pub enum IllegalMoveOriginKind<'tcx> {
+    /// Illegal move due to attempt to move from behind a reference.
+    BorrowedContent {
+        /// The place the reference refers to: if erroneous code was trying to
+        /// move from `(*x).f` this will be `*x`.
+        target_place: Place<'tcx>,
+    },
+
+    /// Illegal move due to attempt to move from field of an ADT that
+    /// implements `Drop`. Rust maintains invariant that all `Drop`
+    /// ADT's remain fully-initialized so that user-defined destructor
+    /// can safely read from all of the ADT's fields.
+    InteriorOfTypeWithDestructor { container_ty: Ty<'tcx> },
+
+    /// Illegal move due to attempt to move out of a slice or array.
+    InteriorOfSliceOrArray { ty: Ty<'tcx>, is_index: bool },
+}
+
+#[derive(Debug)]
+pub enum MoveError<'tcx> {
+    IllegalMove { cannot_move_out_of: IllegalMoveOrigin<'tcx> },
+    UnionMove { path: MovePathIndex },
+}
+
+impl<'tcx> MoveError<'tcx> {
+    fn cannot_move_out_of(location: Location, kind: IllegalMoveOriginKind<'tcx>) -> Self {
+        let origin = IllegalMoveOrigin { location, kind };
+        MoveError::IllegalMove { cannot_move_out_of: origin }
+    }
+}
+
+impl<'tcx> MoveData<'tcx> {
+    pub fn gather_moves(
+        body: &Body<'tcx>,
+        tcx: TyCtxt<'tcx>,
+        param_env: ParamEnv<'tcx>,
+    ) -> MoveDat<'tcx> {
+        builder::gather_moves(body, tcx, param_env)
+    }
+
+    /// For the move path `mpi`, returns the root local variable (if any) that starts the path.
+    /// (e.g., for a path like `a.b.c` returns `Some(a)`)
+    pub fn base_local(&self, mut mpi: MovePathIndex) -> Option<Local> {
+        loop {
+            let path = &self.move_paths[mpi];
+            if let Some(l) = path.place.as_local() {
+                return Some(l);
+            }
+            if let Some(parent) = path.parent {
+                mpi = parent;
+                continue;
+            } else {
+                return None;
+            }
+        }
+    }
+
+    pub fn find_in_move_path_or_its_descendants(
+        &self,
+        root: MovePathIndex,
+        pred: impl Fn(MovePathIndex) -> bool,
+    ) -> Option<MovePathIndex> {
+        if pred(root) {
+            return Some(root);
+        }
+
+        self.move_paths[root].find_descendant(&self.move_paths, pred)
+    }
+}