rustc_mir_transform/
deref_separator.rs1use rustc_middle::mir::visit::NonUseContext::VarDebugInfo;
2use rustc_middle::mir::visit::{MutVisitor, PlaceContext};
3use rustc_middle::mir::*;
4use rustc_middle::ty::TyCtxt;
5
6use crate::patch::MirPatch;
7
8pub(super) struct Derefer;
9
10struct DerefChecker<'a, 'tcx> {
11 tcx: TyCtxt<'tcx>,
12 patcher: MirPatch<'tcx>,
13 local_decls: &'a LocalDecls<'tcx>,
14 add_deref_metadata: bool,
15}
16
17impl<'a, 'tcx> MutVisitor<'tcx> for DerefChecker<'a, 'tcx> {
18 fn tcx(&self) -> TyCtxt<'tcx> {
19 self.tcx
20 }
21
22 fn visit_place(&mut self, place: &mut Place<'tcx>, cntxt: PlaceContext, loc: Location) {
23 if !place.projection.is_empty()
24 && cntxt != PlaceContext::NonUse(VarDebugInfo)
25 && place.projection[1..].contains(&ProjectionElem::Deref)
26 {
27 let mut place_local = place.local;
28 let mut last_len = 0;
29 let mut last_deref_idx = 0;
30
31 for (idx, elem) in place.projection[0..].iter().enumerate() {
32 if *elem == ProjectionElem::Deref {
33 last_deref_idx = idx;
34 }
35 }
36
37 for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() {
38 if !p_ref.projection.is_empty() && p_elem == ProjectionElem::Deref {
39 let ty = p_ref.ty(self.local_decls, self.tcx).ty;
40 let temp = self.patcher.new_local_with_info(
41 ty,
42 self.local_decls[p_ref.local].source_info.span,
43 if self.add_deref_metadata {
44 LocalInfo::DerefTemp
45 } else {
46 LocalInfo::Boring
47 },
48 );
49
50 let deref_place = Place::from(place_local)
53 .project_deeper(&p_ref.projection[last_len..], self.tcx);
54
55 self.patcher.add_assign(
56 loc,
57 Place::from(temp),
58 if self.add_deref_metadata {
59 Rvalue::CopyForDeref(deref_place)
60 } else {
61 Rvalue::Use(Operand::Copy(deref_place))
62 },
63 );
64 place_local = temp;
65 last_len = p_ref.projection.len();
66
67 if idx == last_deref_idx {
69 let temp_place =
70 Place::from(temp).project_deeper(&place.projection[idx..], self.tcx);
71 *place = temp_place;
72 }
73 }
74 }
75 }
76 }
77}
78
79pub(super) fn deref_finder<'tcx>(
80 tcx: TyCtxt<'tcx>,
81 body: &mut Body<'tcx>,
82 add_deref_metadata: bool,
83) {
84 let patch = MirPatch::new(body);
85 let mut checker =
86 DerefChecker { tcx, patcher: patch, local_decls: &body.local_decls, add_deref_metadata };
87
88 for (bb, data) in body.basic_blocks.as_mut_preserves_cfg().iter_enumerated_mut() {
89 checker.visit_basic_block_data(bb, data);
90 }
91
92 checker.patcher.apply(body);
93}
94
95impl<'tcx> crate::MirPass<'tcx> for Derefer {
96 fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
97 deref_finder(tcx, body, true);
98 }
99
100 fn is_required(&self) -> bool {
101 true
102 }
103}