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Commit | Line | Data |
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04454e1e FG |
1 | use crate::MirPass; |
2 | use rustc_index::vec::IndexVec; | |
3 | use rustc_middle::mir::patch::MirPatch; | |
923072b8 | 4 | use rustc_middle::mir::visit::NonUseContext::VarDebugInfo; |
04454e1e FG |
5 | use rustc_middle::mir::visit::{MutVisitor, PlaceContext}; |
6 | use rustc_middle::mir::*; | |
7 | use rustc_middle::ty::TyCtxt; | |
923072b8 | 8 | |
04454e1e FG |
9 | pub struct Derefer; |
10 | ||
11 | pub struct DerefChecker<'tcx> { | |
12 | tcx: TyCtxt<'tcx>, | |
13 | patcher: MirPatch<'tcx>, | |
14 | local_decls: IndexVec<Local, LocalDecl<'tcx>>, | |
15 | } | |
16 | ||
17 | impl<'tcx> MutVisitor<'tcx> for DerefChecker<'tcx> { | |
18 | fn tcx(&self) -> TyCtxt<'tcx> { | |
19 | self.tcx | |
20 | } | |
21 | ||
923072b8 FG |
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; | |
04454e1e | 30 | |
923072b8 | 31 | let mut prev_temp: Option<Local> = None; |
04454e1e | 32 | |
923072b8 FG |
33 | for (idx, elem) in place.projection[0..].iter().enumerate() { |
34 | if *elem == ProjectionElem::Deref { | |
35 | last_deref_idx = idx; | |
04454e1e | 36 | } |
923072b8 | 37 | } |
064997fb | 38 | |
923072b8 FG |
39 | for (idx, (p_ref, p_elem)) in place.iter_projections().enumerate() { |
40 | if !p_ref.projection.is_empty() && p_elem == ProjectionElem::Deref { | |
41 | let ty = p_ref.ty(&self.local_decls, self.tcx).ty; | |
42 | let temp = self.patcher.new_local_with_info( | |
43 | ty, | |
44 | self.local_decls[p_ref.local].source_info.span, | |
45 | Some(Box::new(LocalInfo::DerefTemp)), | |
46 | ); | |
47 | ||
48 | self.patcher.add_statement(loc, StatementKind::StorageLive(temp)); | |
49 | ||
50 | // We are adding current p_ref's projections to our | |
51 | // temp value, excluding projections we already covered. | |
52 | 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), | |
064997fb | 58 | Rvalue::CopyForDeref(deref_place), |
923072b8 FG |
59 | ); |
60 | place_local = temp; | |
61 | last_len = p_ref.projection.len(); | |
62 | ||
63 | // Change `Place` only if we are actually at the Place's last deref | |
64 | if idx == last_deref_idx { | |
65 | let temp_place = | |
66 | Place::from(temp).project_deeper(&place.projection[idx..], self.tcx); | |
67 | *place = temp_place; | |
68 | } | |
69 | ||
70 | // We are destroying the previous temp since it's no longer used. | |
71 | if let Some(prev_temp) = prev_temp { | |
72 | self.patcher.add_statement(loc, StatementKind::StorageDead(prev_temp)); | |
73 | } | |
74 | ||
75 | prev_temp = Some(temp); | |
04454e1e | 76 | } |
04454e1e | 77 | } |
04454e1e | 78 | |
923072b8 FG |
79 | // Since we won't be able to reach final temp, we destroy it outside the loop. |
80 | if let Some(prev_temp) = prev_temp { | |
81 | let last_loc = | |
82 | Location { block: loc.block, statement_index: loc.statement_index + 1 }; | |
83 | self.patcher.add_statement(last_loc, StatementKind::StorageDead(prev_temp)); | |
84 | } | |
04454e1e FG |
85 | } |
86 | } | |
87 | } | |
88 | ||
89 | pub fn deref_finder<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { | |
90 | let patch = MirPatch::new(body); | |
91 | let mut checker = DerefChecker { tcx, patcher: patch, local_decls: body.local_decls.clone() }; | |
92 | ||
93 | for (bb, data) in body.basic_blocks_mut().iter_enumerated_mut() { | |
94 | checker.visit_basic_block_data(bb, data); | |
95 | } | |
96 | ||
97 | checker.patcher.apply(body); | |
98 | } | |
99 | ||
100 | impl<'tcx> MirPass<'tcx> for Derefer { | |
101 | fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { | |
102 | deref_finder(tcx, body); | |
923072b8 | 103 | body.phase = MirPhase::Derefered; |
04454e1e FG |
104 | } |
105 | } |