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1 | use crate::mir::traversal::Postorder; |
2 | use crate::mir::{BasicBlock, BasicBlockData, Successors, Terminator, TerminatorKind, START_BLOCK}; | |
064997fb | 3 | |
9ffffee4 | 4 | use rustc_data_structures::fx::FxHashMap; |
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5 | use rustc_data_structures::graph; |
6 | use rustc_data_structures::graph::dominators::{dominators, Dominators}; | |
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7 | use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; |
8 | use rustc_data_structures::sync::OnceCell; | |
353b0b11 | 9 | use rustc_index::vec::{IndexSlice, IndexVec}; |
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10 | use rustc_serialize::{Decodable, Decoder, Encodable, Encoder}; |
11 | use smallvec::SmallVec; | |
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12 | |
13 | #[derive(Clone, TyEncodable, TyDecodable, Debug, HashStable, TypeFoldable, TypeVisitable)] | |
14 | pub struct BasicBlocks<'tcx> { | |
15 | basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>, | |
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16 | cache: Cache, |
17 | } | |
18 | ||
19 | // Typically 95%+ of basic blocks have 4 or fewer predecessors. | |
20 | pub type Predecessors = IndexVec<BasicBlock, SmallVec<[BasicBlock; 4]>>; | |
21 | ||
22 | pub type SwitchSources = FxHashMap<(BasicBlock, BasicBlock), SmallVec<[Option<u128>; 1]>>; | |
23 | ||
24 | #[derive(Clone, Default, Debug)] | |
25 | struct Cache { | |
26 | predecessors: OnceCell<Predecessors>, | |
27 | switch_sources: OnceCell<SwitchSources>, | |
28 | is_cyclic: OnceCell<bool>, | |
29 | postorder: OnceCell<Vec<BasicBlock>>, | |
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30 | } |
31 | ||
32 | impl<'tcx> BasicBlocks<'tcx> { | |
33 | #[inline] | |
34 | pub fn new(basic_blocks: IndexVec<BasicBlock, BasicBlockData<'tcx>>) -> Self { | |
9ffffee4 | 35 | BasicBlocks { basic_blocks, cache: Cache::default() } |
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36 | } |
37 | ||
38 | /// Returns true if control-flow graph contains a cycle reachable from the `START_BLOCK`. | |
39 | #[inline] | |
40 | pub fn is_cfg_cyclic(&self) -> bool { | |
9ffffee4 | 41 | *self.cache.is_cyclic.get_or_init(|| graph::is_cyclic(self)) |
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42 | } |
43 | ||
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44 | pub fn dominators(&self) -> Dominators<BasicBlock> { |
45 | dominators(&self) | |
46 | } | |
47 | ||
48 | /// Returns predecessors for each basic block. | |
49 | #[inline] | |
50 | pub fn predecessors(&self) -> &Predecessors { | |
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51 | self.cache.predecessors.get_or_init(|| { |
52 | let mut preds = IndexVec::from_elem(SmallVec::new(), &self.basic_blocks); | |
53 | for (bb, data) in self.basic_blocks.iter_enumerated() { | |
54 | if let Some(term) = &data.terminator { | |
55 | for succ in term.successors() { | |
56 | preds[succ].push(bb); | |
57 | } | |
58 | } | |
59 | } | |
60 | preds | |
61 | }) | |
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62 | } |
63 | ||
64 | /// Returns basic blocks in a postorder. | |
65 | #[inline] | |
66 | pub fn postorder(&self) -> &[BasicBlock] { | |
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67 | self.cache.postorder.get_or_init(|| { |
68 | Postorder::new(&self.basic_blocks, START_BLOCK).map(|(bb, _)| bb).collect() | |
69 | }) | |
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70 | } |
71 | ||
72 | /// `switch_sources()[&(target, switch)]` returns a list of switch | |
73 | /// values that lead to a `target` block from a `switch` block. | |
74 | #[inline] | |
75 | pub fn switch_sources(&self) -> &SwitchSources { | |
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76 | self.cache.switch_sources.get_or_init(|| { |
77 | let mut switch_sources: SwitchSources = FxHashMap::default(); | |
78 | for (bb, data) in self.basic_blocks.iter_enumerated() { | |
79 | if let Some(Terminator { | |
80 | kind: TerminatorKind::SwitchInt { targets, .. }, .. | |
81 | }) = &data.terminator | |
82 | { | |
83 | for (value, target) in targets.iter() { | |
84 | switch_sources.entry((target, bb)).or_default().push(Some(value)); | |
85 | } | |
86 | switch_sources.entry((targets.otherwise(), bb)).or_default().push(None); | |
87 | } | |
88 | } | |
89 | switch_sources | |
90 | }) | |
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91 | } |
92 | ||
93 | /// Returns mutable reference to basic blocks. Invalidates CFG cache. | |
94 | #[inline] | |
95 | pub fn as_mut(&mut self) -> &mut IndexVec<BasicBlock, BasicBlockData<'tcx>> { | |
96 | self.invalidate_cfg_cache(); | |
97 | &mut self.basic_blocks | |
98 | } | |
99 | ||
100 | /// Get mutable access to basic blocks without invalidating the CFG cache. | |
101 | /// | |
102 | /// By calling this method instead of e.g. [`BasicBlocks::as_mut`] you promise not to change | |
103 | /// the CFG. This means that | |
104 | /// | |
105 | /// 1) The number of basic blocks remains unchanged | |
106 | /// 2) The set of successors of each terminator remains unchanged. | |
107 | /// 3) For each `TerminatorKind::SwitchInt`, the `targets` remains the same and the terminator | |
108 | /// kind is not changed. | |
109 | /// | |
110 | /// If any of these conditions cannot be upheld, you should call [`BasicBlocks::invalidate_cfg_cache`]. | |
111 | #[inline] | |
112 | pub fn as_mut_preserves_cfg(&mut self) -> &mut IndexVec<BasicBlock, BasicBlockData<'tcx>> { | |
113 | &mut self.basic_blocks | |
114 | } | |
115 | ||
116 | /// Invalidates cached information about the CFG. | |
117 | /// | |
118 | /// You will only ever need this if you have also called [`BasicBlocks::as_mut_preserves_cfg`]. | |
119 | /// All other methods that allow you to mutate the basic blocks also call this method | |
f2b60f7d | 120 | /// themselves, thereby avoiding any risk of accidentally cache invalidation. |
064997fb | 121 | pub fn invalidate_cfg_cache(&mut self) { |
9ffffee4 | 122 | self.cache = Cache::default(); |
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123 | } |
124 | } | |
125 | ||
126 | impl<'tcx> std::ops::Deref for BasicBlocks<'tcx> { | |
353b0b11 | 127 | type Target = IndexSlice<BasicBlock, BasicBlockData<'tcx>>; |
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128 | |
129 | #[inline] | |
353b0b11 | 130 | fn deref(&self) -> &IndexSlice<BasicBlock, BasicBlockData<'tcx>> { |
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131 | &self.basic_blocks |
132 | } | |
133 | } | |
134 | ||
135 | impl<'tcx> graph::DirectedGraph for BasicBlocks<'tcx> { | |
136 | type Node = BasicBlock; | |
137 | } | |
138 | ||
139 | impl<'tcx> graph::WithNumNodes for BasicBlocks<'tcx> { | |
140 | #[inline] | |
141 | fn num_nodes(&self) -> usize { | |
142 | self.basic_blocks.len() | |
143 | } | |
144 | } | |
145 | ||
146 | impl<'tcx> graph::WithStartNode for BasicBlocks<'tcx> { | |
147 | #[inline] | |
148 | fn start_node(&self) -> Self::Node { | |
149 | START_BLOCK | |
150 | } | |
151 | } | |
152 | ||
153 | impl<'tcx> graph::WithSuccessors for BasicBlocks<'tcx> { | |
154 | #[inline] | |
155 | fn successors(&self, node: Self::Node) -> <Self as graph::GraphSuccessors<'_>>::Iter { | |
156 | self.basic_blocks[node].terminator().successors() | |
157 | } | |
158 | } | |
159 | ||
160 | impl<'a, 'b> graph::GraphSuccessors<'b> for BasicBlocks<'a> { | |
161 | type Item = BasicBlock; | |
162 | type Iter = Successors<'b>; | |
163 | } | |
164 | ||
165 | impl<'tcx, 'graph> graph::GraphPredecessors<'graph> for BasicBlocks<'tcx> { | |
166 | type Item = BasicBlock; | |
167 | type Iter = std::iter::Copied<std::slice::Iter<'graph, BasicBlock>>; | |
168 | } | |
169 | ||
170 | impl<'tcx> graph::WithPredecessors for BasicBlocks<'tcx> { | |
171 | #[inline] | |
172 | fn predecessors(&self, node: Self::Node) -> <Self as graph::GraphPredecessors<'_>>::Iter { | |
173 | self.predecessors()[node].iter().copied() | |
174 | } | |
175 | } | |
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176 | |
177 | TrivialTypeTraversalAndLiftImpls! { | |
178 | Cache, | |
179 | } | |
180 | ||
181 | impl<S: Encoder> Encodable<S> for Cache { | |
182 | #[inline] | |
183 | fn encode(&self, _s: &mut S) {} | |
184 | } | |
185 | ||
186 | impl<D: Decoder> Decodable<D> for Cache { | |
187 | #[inline] | |
188 | fn decode(_: &mut D) -> Self { | |
189 | Default::default() | |
190 | } | |
191 | } | |
192 | ||
193 | impl<CTX> HashStable<CTX> for Cache { | |
194 | #[inline] | |
195 | fn hash_stable(&self, _: &mut CTX, _: &mut StableHasher) {} | |
196 | } |