1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
|
use rustc_data_structures::fx::FxHashMap;
use rustc_middle::mir::*;
/// Used for reverting changes made by `DerefSeparator`
#[derive(Default, Debug)]
pub(crate) struct UnDerefer<'tcx> {
deref_chains: FxHashMap<Local, Vec<PlaceRef<'tcx>>>,
}
impl<'tcx> UnDerefer<'tcx> {
#[inline]
pub(crate) fn insert(&mut self, local: Local, reffed: PlaceRef<'tcx>) {
let mut chain = self.deref_chains.remove(&reffed.local).unwrap_or_default();
chain.push(reffed);
self.deref_chains.insert(local, chain);
}
/// Returns the chain of places behind `DerefTemp` locals
#[inline]
pub(crate) fn deref_chain(&self, local: Local) -> &[PlaceRef<'tcx>] {
self.deref_chains.get(&local).map(Vec::as_slice).unwrap_or_default()
}
/// Iterates over the projections of a place and its deref chain.
///
/// See [`PlaceRef::iter_projections`]
#[inline]
pub(crate) fn iter_projections(
&self,
place: PlaceRef<'tcx>,
) -> impl Iterator<Item = (PlaceRef<'tcx>, PlaceElem<'tcx>)> + '_ {
ProjectionIter::new(self.deref_chain(place.local), place)
}
}
/// The iterator returned by [`UnDerefer::iter_projections`].
struct ProjectionIter<'a, 'tcx> {
places: SlicePlusOne<'a, PlaceRef<'tcx>>,
proj_idx: usize,
}
impl<'a, 'tcx> ProjectionIter<'a, 'tcx> {
#[inline]
fn new(deref_chain: &'a [PlaceRef<'tcx>], place: PlaceRef<'tcx>) -> Self {
// just return an empty iterator for a bare local
let last = if place.as_local().is_none() {
Some(place)
} else {
debug_assert!(deref_chain.is_empty());
None
};
ProjectionIter { places: SlicePlusOne { slice: deref_chain, last }, proj_idx: 0 }
}
}
impl<'tcx> Iterator for ProjectionIter<'_, 'tcx> {
type Item = (PlaceRef<'tcx>, PlaceElem<'tcx>);
#[inline]
fn next(&mut self) -> Option<(PlaceRef<'tcx>, PlaceElem<'tcx>)> {
let place = self.places.read()?;
// the projection should never be empty except for a bare local which is handled in new
let partial_place =
PlaceRef { local: place.local, projection: &place.projection[..self.proj_idx] };
let elem = place.projection[self.proj_idx];
if self.proj_idx == place.projection.len() - 1 {
self.proj_idx = 0;
self.places.advance();
} else {
self.proj_idx += 1;
}
Some((partial_place, elem))
}
}
struct SlicePlusOne<'a, T> {
slice: &'a [T],
last: Option<T>,
}
impl<T: Copy> SlicePlusOne<'_, T> {
#[inline]
fn read(&self) -> Option<T> {
self.slice.first().copied().or(self.last)
}
#[inline]
fn advance(&mut self) {
match self.slice {
[_, ref remainder @ ..] => {
self.slice = remainder;
}
[] => self.last = None,
}
}
}
|
