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Commit | Line | Data |
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1a4d82fc JJ |
1 | //! A module for propagating forward dataflow information. The analysis |
2 | //! assumes that the items to be propagated can be represented as bits | |
3 | //! and thus uses bitvectors. Your job is simply to specify the so-called | |
4 | //! GEN and KILL bits for each expression. | |
970d7e83 | 5 | |
b7449926 XL |
6 | use rustc::cfg; |
7 | use rustc::cfg::CFGIndex; | |
8 | use rustc::ty::TyCtxt; | |
c34b1796 | 9 | use std::io; |
9cc50fc6 | 10 | use std::mem; |
85aaf69f | 11 | use std::usize; |
b039eaaf | 12 | use syntax::print::pprust::PrintState; |
9fa01778 | 13 | use log::debug; |
3b2f2976 | 14 | |
8faf50e0 | 15 | use rustc_data_structures::graph::implementation::OUTGOING; |
3b2f2976 | 16 | |
b7449926 XL |
17 | use rustc::util::nodemap::FxHashMap; |
18 | use rustc::hir; | |
9fa01778 | 19 | use rustc::hir::intravisit; |
b7449926 | 20 | use rustc::hir::print as pprust; |
e9174d1e | 21 | |
1a4d82fc | 22 | |
c34b1796 | 23 | #[derive(Copy, Clone, Debug)] |
1a4d82fc JJ |
24 | pub enum EntryOrExit { |
25 | Entry, | |
26 | Exit, | |
27 | } | |
970d7e83 | 28 | |
1a4d82fc JJ |
29 | #[derive(Clone)] |
30 | pub struct DataFlowContext<'a, 'tcx: 'a, O> { | |
a7813a04 | 31 | tcx: TyCtxt<'a, 'tcx, 'tcx>, |
1a4d82fc JJ |
32 | |
33 | /// a name for the analysis using this dataflow instance | |
34 | analysis_name: &'static str, | |
970d7e83 LB |
35 | |
36 | /// the data flow operator | |
1a4d82fc | 37 | oper: O, |
970d7e83 LB |
38 | |
39 | /// number of bits to propagate per id | |
c34b1796 | 40 | bits_per_id: usize, |
970d7e83 LB |
41 | |
42 | /// number of words we will use to store bits_per_id. | |
85aaf69f | 43 | /// equal to bits_per_id/usize::BITS rounded up. |
c34b1796 | 44 | words_per_id: usize, |
970d7e83 | 45 | |
1a4d82fc JJ |
46 | // mapping from node to cfg node index |
47 | // FIXME (#6298): Shouldn't this go with CFG? | |
ea8adc8c | 48 | local_id_to_index: FxHashMap<hir::ItemLocalId, Vec<CFGIndex>>, |
970d7e83 | 49 | |
1a4d82fc | 50 | // Bit sets per cfg node. The following three fields (`gens`, `kills`, |
970d7e83 LB |
51 | // and `on_entry`) all have the same structure. For each id in |
52 | // `id_range`, there is a range of words equal to `words_per_id`. | |
53 | // So, to access the bits for any given id, you take a slice of | |
54 | // the full vector (see the method `compute_id_range()`). | |
55 | ||
1a4d82fc | 56 | /// bits generated as we exit the cfg node. Updated by `add_gen()`. |
c34b1796 | 57 | gens: Vec<usize>, |
970d7e83 | 58 | |
9346a6ac AL |
59 | /// bits killed as we exit the cfg node, or non-locally jump over |
60 | /// it. Updated by `add_kill(KillFrom::ScopeEnd)`. | |
61 | scope_kills: Vec<usize>, | |
62 | ||
63 | /// bits killed as we exit the cfg node directly; if it is jumped | |
0731742a | 64 | /// over, e.g., via `break`, the kills are not reflected in the |
9346a6ac AL |
65 | /// jump's effects. Updated by `add_kill(KillFrom::Execution)`. |
66 | action_kills: Vec<usize>, | |
970d7e83 | 67 | |
1a4d82fc | 68 | /// bits that are valid on entry to the cfg node. Updated by |
970d7e83 | 69 | /// `propagate()`. |
c34b1796 | 70 | on_entry: Vec<usize>, |
1a4d82fc JJ |
71 | } |
72 | ||
73 | pub trait BitwiseOperator { | |
74 | /// Joins two predecessor bits together, typically either `|` or `&` | |
c34b1796 | 75 | fn join(&self, succ: usize, pred: usize) -> usize; |
970d7e83 LB |
76 | } |
77 | ||
78 | /// Parameterization for the precise form of data flow that is used. | |
1a4d82fc | 79 | pub trait DataFlowOperator : BitwiseOperator { |
970d7e83 LB |
80 | /// Specifies the initial value for each bit in the `on_entry` set |
81 | fn initial_value(&self) -> bool; | |
1a4d82fc | 82 | } |
970d7e83 | 83 | |
9fa01778 | 84 | struct PropagationContext<'a, 'b: 'a, 'tcx: 'b, O> { |
1a4d82fc JJ |
85 | dfcx: &'a mut DataFlowContext<'b, 'tcx, O>, |
86 | changed: bool | |
87 | } | |
970d7e83 | 88 | |
ea8adc8c XL |
89 | fn get_cfg_indices<'a>(id: hir::ItemLocalId, |
90 | index: &'a FxHashMap<hir::ItemLocalId, Vec<CFGIndex>>) | |
91 | -> &'a [CFGIndex] { | |
92 | index.get(&id).map_or(&[], |v| &v[..]) | |
970d7e83 LB |
93 | } |
94 | ||
1a4d82fc | 95 | impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> { |
ea8adc8c XL |
96 | fn has_bitset_for_local_id(&self, n: hir::ItemLocalId) -> bool { |
97 | assert!(n != hir::DUMMY_ITEM_LOCAL_ID); | |
98 | self.local_id_to_index.contains_key(&n) | |
1a4d82fc | 99 | } |
970d7e83 LB |
100 | } |
101 | ||
1a4d82fc | 102 | impl<'a, 'tcx, O:DataFlowOperator> pprust::PpAnn for DataFlowContext<'a, 'tcx, O> { |
9fa01778 | 103 | fn nested(&self, state: &mut pprust::State<'_>, nested: pprust::Nested) -> io::Result<()> { |
0731742a | 104 | pprust::PpAnn::nested(self.tcx.hir(), state, nested) |
32a655c1 | 105 | } |
1a4d82fc | 106 | fn pre(&self, |
9fa01778 XL |
107 | ps: &mut pprust::State<'_>, |
108 | node: pprust::AnnNode<'_>) -> io::Result<()> { | |
1a4d82fc | 109 | let id = match node { |
b7449926 XL |
110 | pprust::AnnNode::Name(_) => return Ok(()), |
111 | pprust::AnnNode::Expr(expr) => expr.hir_id.local_id, | |
112 | pprust::AnnNode::Block(blk) => blk.hir_id.local_id, | |
113 | pprust::AnnNode::Item(_) | | |
114 | pprust::AnnNode::SubItem(_) => return Ok(()), | |
115 | pprust::AnnNode::Pat(pat) => pat.hir_id.local_id | |
1a4d82fc JJ |
116 | }; |
117 | ||
ea8adc8c | 118 | if !self.has_bitset_for_local_id(id) { |
c34b1796 AL |
119 | return Ok(()); |
120 | } | |
121 | ||
122 | assert!(self.bits_per_id > 0); | |
ea8adc8c | 123 | let indices = get_cfg_indices(id, &self.local_id_to_index); |
c34b1796 | 124 | for &cfgidx in indices { |
1a4d82fc | 125 | let (start, end) = self.compute_id_range(cfgidx); |
85aaf69f | 126 | let on_entry = &self.on_entry[start.. end]; |
1a4d82fc JJ |
127 | let entry_str = bits_to_string(on_entry); |
128 | ||
85aaf69f | 129 | let gens = &self.gens[start.. end]; |
1a4d82fc JJ |
130 | let gens_str = if gens.iter().any(|&u| u != 0) { |
131 | format!(" gen: {}", bits_to_string(gens)) | |
132 | } else { | |
b7449926 | 133 | String::new() |
1a4d82fc JJ |
134 | }; |
135 | ||
9346a6ac AL |
136 | let action_kills = &self.action_kills[start .. end]; |
137 | let action_kills_str = if action_kills.iter().any(|&u| u != 0) { | |
138 | format!(" action_kill: {}", bits_to_string(action_kills)) | |
139 | } else { | |
b7449926 | 140 | String::new() |
9346a6ac AL |
141 | }; |
142 | ||
143 | let scope_kills = &self.scope_kills[start .. end]; | |
144 | let scope_kills_str = if scope_kills.iter().any(|&u| u != 0) { | |
145 | format!(" scope_kill: {}", bits_to_string(scope_kills)) | |
1a4d82fc | 146 | } else { |
b7449926 | 147 | String::new() |
1a4d82fc | 148 | }; |
970d7e83 | 149 | |
54a0048b | 150 | ps.synth_comment( |
ea8adc8c | 151 | format!("id {}: {}{}{}{}", id.as_usize(), entry_str, |
54a0048b | 152 | gens_str, action_kills_str, scope_kills_str))?; |
041b39d2 | 153 | ps.s.space()?; |
1a4d82fc JJ |
154 | } |
155 | Ok(()) | |
156 | } | |
970d7e83 LB |
157 | } |
158 | ||
ea8adc8c XL |
159 | fn build_local_id_to_index(body: Option<&hir::Body>, |
160 | cfg: &cfg::CFG) | |
161 | -> FxHashMap<hir::ItemLocalId, Vec<CFGIndex>> { | |
0bf4aa26 | 162 | let mut index = FxHashMap::default(); |
1a4d82fc | 163 | |
abe05a73 | 164 | // FIXME(#15020) Would it be better to fold formals from decl |
0731742a | 165 | // into cfg itself? i.e., introduce a fn-based flow-graph in |
1a4d82fc JJ |
166 | // addition to the current block-based flow-graph, rather than |
167 | // have to put traversals like this here? | |
32a655c1 SL |
168 | if let Some(body) = body { |
169 | add_entries_from_fn_body(&mut index, body, cfg.entry); | |
1a4d82fc JJ |
170 | } |
171 | ||
172 | cfg.graph.each_node(|node_idx, node| { | |
c34b1796 | 173 | if let cfg::CFGNodeData::AST(id) = node.data { |
b7449926 | 174 | index.entry(id).or_default().push(node_idx); |
1a4d82fc JJ |
175 | } |
176 | true | |
177 | }); | |
178 | ||
179 | return index; | |
180 | ||
9fa01778 | 181 | /// Adds mappings from the ast nodes for the formal bindings to |
32a655c1 | 182 | /// the entry-node in the graph. |
ea8adc8c | 183 | fn add_entries_from_fn_body(index: &mut FxHashMap<hir::ItemLocalId, Vec<CFGIndex>>, |
32a655c1 | 184 | body: &hir::Body, |
1a4d82fc | 185 | entry: CFGIndex) { |
b7449926 | 186 | use rustc::hir::intravisit::Visitor; |
32a655c1 | 187 | |
1a4d82fc JJ |
188 | struct Formals<'a> { |
189 | entry: CFGIndex, | |
ea8adc8c | 190 | index: &'a mut FxHashMap<hir::ItemLocalId, Vec<CFGIndex>>, |
1a4d82fc JJ |
191 | } |
192 | let mut formals = Formals { entry: entry, index: index }; | |
32a655c1 SL |
193 | for arg in &body.arguments { |
194 | formals.visit_pat(&arg.pat); | |
195 | } | |
196 | impl<'a, 'v> Visitor<'v> for Formals<'a> { | |
476ff2be | 197 | fn nested_visit_map<'this>(&'this mut self) -> intravisit::NestedVisitorMap<'this, 'v> { |
32a655c1 | 198 | intravisit::NestedVisitorMap::None |
476ff2be SL |
199 | } |
200 | ||
e9174d1e | 201 | fn visit_pat(&mut self, p: &hir::Pat) { |
b7449926 | 202 | self.index.entry(p.hir_id.local_id).or_default().push(self.entry); |
92a42be0 | 203 | intravisit::walk_pat(self, p) |
1a4d82fc JJ |
204 | } |
205 | } | |
206 | } | |
970d7e83 LB |
207 | } |
208 | ||
9346a6ac AL |
209 | /// Flag used by `add_kill` to indicate whether the provided kill |
210 | /// takes effect only when control flows directly through the node in | |
211 | /// question, or if the kill's effect is associated with any | |
212 | /// control-flow directly through or indirectly over the node. | |
213 | #[derive(Copy, Clone, PartialEq, Debug)] | |
214 | pub enum KillFrom { | |
215 | /// A `ScopeEnd` kill is one that takes effect when any control | |
216 | /// flow goes over the node. A kill associated with the end of the | |
217 | /// scope of a variable declaration `let x;` is an example of a | |
218 | /// `ScopeEnd` kill. | |
219 | ScopeEnd, | |
220 | ||
221 | /// An `Execution` kill is one that takes effect only when control | |
222 | /// flow goes through the node to completion. A kill associated | |
223 | /// with an assignment statement `x = expr;` is an example of an | |
224 | /// `Execution` kill. | |
225 | Execution, | |
226 | } | |
227 | ||
1a4d82fc | 228 | impl<'a, 'tcx, O:DataFlowOperator> DataFlowContext<'a, 'tcx, O> { |
a7813a04 | 229 | pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>, |
1a4d82fc | 230 | analysis_name: &'static str, |
32a655c1 | 231 | body: Option<&hir::Body>, |
1a4d82fc | 232 | cfg: &cfg::CFG, |
970d7e83 | 233 | oper: O, |
c34b1796 | 234 | bits_per_id: usize) -> DataFlowContext<'a, 'tcx, O> { |
9cc50fc6 SL |
235 | let usize_bits = mem::size_of::<usize>() * 8; |
236 | let words_per_id = (bits_per_id + usize_bits - 1) / usize_bits; | |
1a4d82fc JJ |
237 | let num_nodes = cfg.graph.all_nodes().len(); |
238 | ||
9fa01778 | 239 | debug!("DataFlowContext::new(analysis_name: {}, \ |
1a4d82fc JJ |
240 | bits_per_id={}, words_per_id={}) \ |
241 | num_nodes: {}", | |
9fa01778 | 242 | analysis_name, bits_per_id, words_per_id, |
1a4d82fc | 243 | num_nodes); |
970d7e83 | 244 | |
85aaf69f | 245 | let entry = if oper.initial_value() { usize::MAX } else {0}; |
970d7e83 | 246 | |
c1a9b12d SL |
247 | let zeroes = vec![0; num_nodes * words_per_id]; |
248 | let gens = zeroes.clone(); | |
249 | let kills1 = zeroes.clone(); | |
250 | let kills2 = zeroes; | |
251 | let on_entry = vec![entry; num_nodes * words_per_id]; | |
1a4d82fc | 252 | |
ea8adc8c | 253 | let local_id_to_index = build_local_id_to_index(body, cfg); |
970d7e83 LB |
254 | |
255 | DataFlowContext { | |
041b39d2 XL |
256 | tcx, |
257 | analysis_name, | |
258 | words_per_id, | |
ea8adc8c | 259 | local_id_to_index, |
041b39d2 XL |
260 | bits_per_id, |
261 | oper, | |
262 | gens, | |
9346a6ac AL |
263 | action_kills: kills1, |
264 | scope_kills: kills2, | |
041b39d2 | 265 | on_entry, |
970d7e83 LB |
266 | } |
267 | } | |
268 | ||
ea8adc8c | 269 | pub fn add_gen(&mut self, id: hir::ItemLocalId, bit: usize) { |
970d7e83 | 270 | //! Indicates that `id` generates `bit` |
ea8adc8c | 271 | debug!("{} add_gen(id={:?}, bit={})", |
1a4d82fc | 272 | self.analysis_name, id, bit); |
ea8adc8c | 273 | assert!(self.local_id_to_index.contains_key(&id)); |
1a4d82fc | 274 | assert!(self.bits_per_id > 0); |
970d7e83 | 275 | |
ea8adc8c | 276 | let indices = get_cfg_indices(id, &self.local_id_to_index); |
c34b1796 AL |
277 | for &cfgidx in indices { |
278 | let (start, end) = self.compute_id_range(cfgidx); | |
279 | let gens = &mut self.gens[start.. end]; | |
280 | set_bit(gens, bit); | |
281 | } | |
970d7e83 LB |
282 | } |
283 | ||
ea8adc8c | 284 | pub fn add_kill(&mut self, kind: KillFrom, id: hir::ItemLocalId, bit: usize) { |
970d7e83 | 285 | //! Indicates that `id` kills `bit` |
ea8adc8c | 286 | debug!("{} add_kill(id={:?}, bit={})", |
1a4d82fc | 287 | self.analysis_name, id, bit); |
ea8adc8c | 288 | assert!(self.local_id_to_index.contains_key(&id)); |
1a4d82fc | 289 | assert!(self.bits_per_id > 0); |
970d7e83 | 290 | |
ea8adc8c | 291 | let indices = get_cfg_indices(id, &self.local_id_to_index); |
c34b1796 AL |
292 | for &cfgidx in indices { |
293 | let (start, end) = self.compute_id_range(cfgidx); | |
9346a6ac AL |
294 | let kills = match kind { |
295 | KillFrom::Execution => &mut self.action_kills[start.. end], | |
296 | KillFrom::ScopeEnd => &mut self.scope_kills[start.. end], | |
297 | }; | |
c34b1796 AL |
298 | set_bit(kills, bit); |
299 | } | |
970d7e83 LB |
300 | } |
301 | ||
c34b1796 | 302 | fn apply_gen_kill(&self, cfgidx: CFGIndex, bits: &mut [usize]) { |
1a4d82fc JJ |
303 | //! Applies the gen and kill sets for `cfgidx` to `bits` |
304 | debug!("{} apply_gen_kill(cfgidx={:?}, bits={}) [before]", | |
305 | self.analysis_name, cfgidx, mut_bits_to_string(bits)); | |
306 | assert!(self.bits_per_id > 0); | |
970d7e83 | 307 | |
1a4d82fc | 308 | let (start, end) = self.compute_id_range(cfgidx); |
85aaf69f | 309 | let gens = &self.gens[start.. end]; |
1a4d82fc | 310 | bitwise(bits, gens, &Union); |
9346a6ac AL |
311 | let kills = &self.action_kills[start.. end]; |
312 | bitwise(bits, kills, &Subtract); | |
313 | let kills = &self.scope_kills[start.. end]; | |
1a4d82fc | 314 | bitwise(bits, kills, &Subtract); |
970d7e83 | 315 | |
1a4d82fc JJ |
316 | debug!("{} apply_gen_kill(cfgidx={:?}, bits={}) [after]", |
317 | self.analysis_name, cfgidx, mut_bits_to_string(bits)); | |
970d7e83 LB |
318 | } |
319 | ||
c34b1796 | 320 | fn compute_id_range(&self, cfgidx: CFGIndex) -> (usize, usize) { |
1a4d82fc | 321 | let n = cfgidx.node_id(); |
970d7e83 LB |
322 | let start = n * self.words_per_id; |
323 | let end = start + self.words_per_id; | |
970d7e83 LB |
324 | |
325 | assert!(start < self.gens.len()); | |
326 | assert!(end <= self.gens.len()); | |
9346a6ac AL |
327 | assert!(self.gens.len() == self.action_kills.len()); |
328 | assert!(self.gens.len() == self.scope_kills.len()); | |
970d7e83 LB |
329 | assert!(self.gens.len() == self.on_entry.len()); |
330 | ||
331 | (start, end) | |
332 | } | |
333 | ||
334 | ||
ea8adc8c | 335 | pub fn each_bit_on_entry<F>(&self, id: hir::ItemLocalId, mut f: F) -> bool where |
c34b1796 | 336 | F: FnMut(usize) -> bool, |
1a4d82fc | 337 | { |
970d7e83 LB |
338 | //! Iterates through each bit that is set on entry to `id`. |
339 | //! Only useful after `propagate()` has been called. | |
ea8adc8c | 340 | if !self.has_bitset_for_local_id(id) { |
970d7e83 LB |
341 | return true; |
342 | } | |
ea8adc8c | 343 | let indices = get_cfg_indices(id, &self.local_id_to_index); |
c34b1796 | 344 | for &cfgidx in indices { |
92a42be0 | 345 | if !self.each_bit_for_node(EntryOrExit::Entry, cfgidx, |i| f(i)) { |
c34b1796 AL |
346 | return false; |
347 | } | |
348 | } | |
349 | return true; | |
970d7e83 LB |
350 | } |
351 | ||
1a4d82fc | 352 | pub fn each_bit_for_node<F>(&self, e: EntryOrExit, cfgidx: CFGIndex, f: F) -> bool where |
c34b1796 | 353 | F: FnMut(usize) -> bool, |
1a4d82fc JJ |
354 | { |
355 | //! Iterates through each bit that is set on entry/exit to `cfgidx`. | |
970d7e83 LB |
356 | //! Only useful after `propagate()` has been called. |
357 | ||
1a4d82fc JJ |
358 | if self.bits_per_id == 0 { |
359 | // Skip the surprisingly common degenerate case. (Note | |
360 | // compute_id_range requires self.words_per_id > 0.) | |
361 | return true; | |
362 | } | |
363 | ||
364 | let (start, end) = self.compute_id_range(cfgidx); | |
85aaf69f | 365 | let on_entry = &self.on_entry[start.. end]; |
1a4d82fc JJ |
366 | let temp_bits; |
367 | let slice = match e { | |
92a42be0 SL |
368 | EntryOrExit::Entry => on_entry, |
369 | EntryOrExit::Exit => { | |
1a4d82fc | 370 | let mut t = on_entry.to_vec(); |
85aaf69f | 371 | self.apply_gen_kill(cfgidx, &mut t); |
1a4d82fc | 372 | temp_bits = t; |
85aaf69f | 373 | &temp_bits[..] |
1a4d82fc JJ |
374 | } |
375 | }; | |
376 | debug!("{} each_bit_for_node({:?}, cfgidx={:?}) bits={}", | |
377 | self.analysis_name, e, cfgidx, bits_to_string(slice)); | |
378 | self.each_bit(slice, f) | |
970d7e83 LB |
379 | } |
380 | ||
ea8adc8c | 381 | pub fn each_gen_bit<F>(&self, id: hir::ItemLocalId, mut f: F) -> bool where |
c34b1796 | 382 | F: FnMut(usize) -> bool, |
1a4d82fc | 383 | { |
970d7e83 | 384 | //! Iterates through each bit in the gen set for `id`. |
ea8adc8c | 385 | if !self.has_bitset_for_local_id(id) { |
1a4d82fc JJ |
386 | return true; |
387 | } | |
970d7e83 | 388 | |
1a4d82fc JJ |
389 | if self.bits_per_id == 0 { |
390 | // Skip the surprisingly common degenerate case. (Note | |
391 | // compute_id_range requires self.words_per_id > 0.) | |
970d7e83 LB |
392 | return true; |
393 | } | |
1a4d82fc | 394 | |
ea8adc8c | 395 | let indices = get_cfg_indices(id, &self.local_id_to_index); |
c34b1796 AL |
396 | for &cfgidx in indices { |
397 | let (start, end) = self.compute_id_range(cfgidx); | |
398 | let gens = &self.gens[start.. end]; | |
ea8adc8c | 399 | debug!("{} each_gen_bit(id={:?}, gens={})", |
c34b1796 AL |
400 | self.analysis_name, id, bits_to_string(gens)); |
401 | if !self.each_bit(gens, |i| f(i)) { | |
402 | return false; | |
403 | } | |
404 | } | |
405 | return true; | |
970d7e83 LB |
406 | } |
407 | ||
c34b1796 AL |
408 | fn each_bit<F>(&self, words: &[usize], mut f: F) -> bool where |
409 | F: FnMut(usize) -> bool, | |
1a4d82fc | 410 | { |
970d7e83 | 411 | //! Helper for iterating over the bits in a bit set. |
1a4d82fc JJ |
412 | //! Returns false on the first call to `f` that returns false; |
413 | //! if all calls to `f` return true, then returns true. | |
970d7e83 | 414 | |
9cc50fc6 | 415 | let usize_bits = mem::size_of::<usize>() * 8; |
1a4d82fc | 416 | for (word_index, &word) in words.iter().enumerate() { |
970d7e83 | 417 | if word != 0 { |
9cc50fc6 SL |
418 | let base_index = word_index * usize_bits; |
419 | for offset in 0..usize_bits { | |
970d7e83 LB |
420 | let bit = 1 << offset; |
421 | if (word & bit) != 0 { | |
0731742a | 422 | // N.B., we round up the total number of bits |
970d7e83 | 423 | // that we store in any given bit set so that |
85aaf69f | 424 | // it is an even multiple of usize::BITS. This |
970d7e83 LB |
425 | // means that there may be some stray bits at |
426 | // the end that do not correspond to any | |
427 | // actual value. So before we callback, check | |
428 | // whether the bit_index is greater than the | |
429 | // actual value the user specified and stop | |
430 | // iterating if so. | |
c34b1796 | 431 | let bit_index = base_index + offset as usize; |
970d7e83 LB |
432 | if bit_index >= self.bits_per_id { |
433 | return true; | |
434 | } else if !f(bit_index) { | |
435 | return false; | |
436 | } | |
437 | } | |
438 | } | |
439 | } | |
440 | } | |
441 | return true; | |
442 | } | |
970d7e83 | 443 | |
1a4d82fc JJ |
444 | pub fn add_kills_from_flow_exits(&mut self, cfg: &cfg::CFG) { |
445 | //! Whenever you have a `break` or `continue` statement, flow | |
446 | //! exits through any number of enclosing scopes on its way to | |
447 | //! the new destination. This function infers the kill bits of | |
448 | //! those control operators based on the kill bits associated | |
449 | //! with those scopes. | |
450 | //! | |
451 | //! This is usually called (if it is called at all), after | |
452 | //! all add_gen and add_kill calls, but before propagate. | |
970d7e83 | 453 | |
1a4d82fc | 454 | debug!("{} add_kills_from_flow_exits", self.analysis_name); |
970d7e83 | 455 | if self.bits_per_id == 0 { |
1a4d82fc JJ |
456 | // Skip the surprisingly common degenerate case. (Note |
457 | // compute_id_range requires self.words_per_id > 0.) | |
970d7e83 LB |
458 | return; |
459 | } | |
1a4d82fc JJ |
460 | cfg.graph.each_edge(|_edge_index, edge| { |
461 | let flow_exit = edge.source(); | |
462 | let (start, end) = self.compute_id_range(flow_exit); | |
9346a6ac | 463 | let mut orig_kills = self.scope_kills[start.. end].to_vec(); |
1a4d82fc JJ |
464 | |
465 | let mut changed = false; | |
ea8adc8c XL |
466 | for &id in &edge.data.exiting_scopes { |
467 | let opt_cfg_idx = self.local_id_to_index.get(&id); | |
1a4d82fc | 468 | match opt_cfg_idx { |
c34b1796 AL |
469 | Some(indices) => { |
470 | for &cfg_idx in indices { | |
471 | let (start, end) = self.compute_id_range(cfg_idx); | |
9346a6ac | 472 | let kills = &self.scope_kills[start.. end]; |
c34b1796 | 473 | if bitwise(&mut orig_kills, kills, &Union) { |
ea8adc8c | 474 | debug!("scope exits: scope id={:?} \ |
9346a6ac | 475 | (node={:?} of {:?}) added killset: {}", |
ea8adc8c | 476 | id, cfg_idx, indices, |
9346a6ac | 477 | bits_to_string(kills)); |
c34b1796 AL |
478 | changed = true; |
479 | } | |
1a4d82fc | 480 | } |
970d7e83 | 481 | } |
1a4d82fc JJ |
482 | None => { |
483 | debug!("{} add_kills_from_flow_exits flow_exit={:?} \ | |
ea8adc8c XL |
484 | no cfg_idx for exiting_scope={:?}", |
485 | self.analysis_name, flow_exit, id); | |
970d7e83 LB |
486 | } |
487 | } | |
970d7e83 LB |
488 | } |
489 | ||
1a4d82fc | 490 | if changed { |
9346a6ac | 491 | let bits = &mut self.scope_kills[start.. end]; |
1a4d82fc JJ |
492 | debug!("{} add_kills_from_flow_exits flow_exit={:?} bits={} [before]", |
493 | self.analysis_name, flow_exit, mut_bits_to_string(bits)); | |
7453a54e | 494 | bits.copy_from_slice(&orig_kills[..]); |
1a4d82fc JJ |
495 | debug!("{} add_kills_from_flow_exits flow_exit={:?} bits={} [after]", |
496 | self.analysis_name, flow_exit, mut_bits_to_string(bits)); | |
970d7e83 | 497 | } |
1a4d82fc JJ |
498 | true |
499 | }); | |
500 | } | |
501 | } | |
970d7e83 | 502 | |
1a4d82fc JJ |
503 | impl<'a, 'tcx, O:DataFlowOperator+Clone+'static> DataFlowContext<'a, 'tcx, O> { |
504 | // ^^^^^^^^^^^^^ only needed for pretty printing | |
32a655c1 | 505 | pub fn propagate(&mut self, cfg: &cfg::CFG, body: &hir::Body) { |
1a4d82fc | 506 | //! Performs the data flow analysis. |
970d7e83 | 507 | |
1a4d82fc JJ |
508 | if self.bits_per_id == 0 { |
509 | // Optimize the surprisingly common degenerate case. | |
510 | return; | |
970d7e83 LB |
511 | } |
512 | ||
1a4d82fc JJ |
513 | { |
514 | let words_per_id = self.words_per_id; | |
515 | let mut propcx = PropagationContext { | |
516 | dfcx: &mut *self, | |
517 | changed: true | |
518 | }; | |
970d7e83 | 519 | |
3b2f2976 | 520 | let nodes_po = cfg.graph.nodes_in_postorder(OUTGOING, cfg.entry); |
c1a9b12d | 521 | let mut temp = vec![0; words_per_id]; |
3b2f2976 | 522 | let mut num_passes = 0; |
1a4d82fc | 523 | while propcx.changed { |
3b2f2976 | 524 | num_passes += 1; |
1a4d82fc | 525 | propcx.changed = false; |
85aaf69f | 526 | propcx.reset(&mut temp); |
3b2f2976 | 527 | propcx.walk_cfg(cfg, &nodes_po, &mut temp); |
970d7e83 | 528 | } |
3b2f2976 | 529 | debug!("finished in {} iterations", num_passes); |
970d7e83 | 530 | } |
970d7e83 | 531 | |
1a4d82fc | 532 | debug!("Dataflow result for {}:", self.analysis_name); |
32a655c1 SL |
533 | debug!("{}", pprust::to_string(self, |s| { |
534 | s.cbox(pprust::indent_unit)?; | |
535 | s.ibox(0)?; | |
536 | s.print_expr(&body.value) | |
537 | })); | |
970d7e83 | 538 | } |
1a4d82fc | 539 | } |
970d7e83 | 540 | |
1a4d82fc JJ |
541 | impl<'a, 'b, 'tcx, O:DataFlowOperator> PropagationContext<'a, 'b, 'tcx, O> { |
542 | fn walk_cfg(&mut self, | |
543 | cfg: &cfg::CFG, | |
3b2f2976 | 544 | nodes_po: &[CFGIndex], |
c34b1796 | 545 | in_out: &mut [usize]) { |
1a4d82fc JJ |
546 | debug!("DataFlowContext::walk_cfg(in_out={}) {}", |
547 | bits_to_string(in_out), self.dfcx.analysis_name); | |
548 | assert!(self.dfcx.bits_per_id > 0); | |
970d7e83 | 549 | |
3b2f2976 XL |
550 | // Iterate over nodes in reverse postorder |
551 | for &node_index in nodes_po.iter().rev() { | |
552 | let node = cfg.graph.node(node_index); | |
ea8adc8c | 553 | debug!("DataFlowContext::walk_cfg idx={:?} id={:?} begin in_out={}", |
c34b1796 | 554 | node_index, node.data.id(), bits_to_string(in_out)); |
970d7e83 | 555 | |
1a4d82fc | 556 | let (start, end) = self.dfcx.compute_id_range(node_index); |
970d7e83 | 557 | |
1a4d82fc | 558 | // Initialize local bitvector with state on-entry. |
7453a54e | 559 | in_out.copy_from_slice(&self.dfcx.on_entry[start.. end]); |
970d7e83 | 560 | |
1a4d82fc JJ |
561 | // Compute state on-exit by applying transfer function to |
562 | // state on-entry. | |
563 | self.dfcx.apply_gen_kill(node_index, in_out); | |
970d7e83 | 564 | |
1a4d82fc JJ |
565 | // Propagate state on-exit from node into its successors. |
566 | self.propagate_bits_into_graph_successors_of(in_out, cfg, node_index); | |
3b2f2976 | 567 | } |
970d7e83 LB |
568 | } |
569 | ||
c34b1796 | 570 | fn reset(&mut self, bits: &mut [usize]) { |
85aaf69f SL |
571 | let e = if self.dfcx.oper.initial_value() {usize::MAX} else {0}; |
572 | for b in bits { | |
1a4d82fc JJ |
573 | *b = e; |
574 | } | |
970d7e83 LB |
575 | } |
576 | ||
1a4d82fc | 577 | fn propagate_bits_into_graph_successors_of(&mut self, |
c34b1796 | 578 | pred_bits: &[usize], |
1a4d82fc JJ |
579 | cfg: &cfg::CFG, |
580 | cfgidx: CFGIndex) { | |
d9579d0f | 581 | for (_, edge) in cfg.graph.outgoing_edges(cfgidx) { |
1a4d82fc | 582 | self.propagate_bits_into_entry_set_for(pred_bits, edge); |
d9579d0f | 583 | } |
970d7e83 LB |
584 | } |
585 | ||
1a4d82fc | 586 | fn propagate_bits_into_entry_set_for(&mut self, |
c34b1796 | 587 | pred_bits: &[usize], |
1a4d82fc JJ |
588 | edge: &cfg::CFGEdge) { |
589 | let source = edge.source(); | |
590 | let cfgidx = edge.target(); | |
591 | debug!("{} propagate_bits_into_entry_set_for(pred_bits={}, {:?} to {:?})", | |
592 | self.dfcx.analysis_name, bits_to_string(pred_bits), source, cfgidx); | |
593 | assert!(self.dfcx.bits_per_id > 0); | |
594 | ||
595 | let (start, end) = self.dfcx.compute_id_range(cfgidx); | |
596 | let changed = { | |
597 | // (scoping mutable borrow of self.dfcx.on_entry) | |
85aaf69f | 598 | let on_entry = &mut self.dfcx.on_entry[start.. end]; |
1a4d82fc | 599 | bitwise(on_entry, pred_bits, &self.dfcx.oper) |
970d7e83 LB |
600 | }; |
601 | if changed { | |
1a4d82fc JJ |
602 | debug!("{} changed entry set for {:?} to {}", |
603 | self.dfcx.analysis_name, cfgidx, | |
85aaf69f | 604 | bits_to_string(&self.dfcx.on_entry[start.. end])); |
970d7e83 LB |
605 | self.changed = true; |
606 | } | |
607 | } | |
608 | } | |
609 | ||
c34b1796 | 610 | fn mut_bits_to_string(words: &mut [usize]) -> String { |
1a4d82fc | 611 | bits_to_string(words) |
970d7e83 LB |
612 | } |
613 | ||
c34b1796 | 614 | fn bits_to_string(words: &[usize]) -> String { |
1a4d82fc | 615 | let mut result = String::new(); |
970d7e83 LB |
616 | let mut sep = '['; |
617 | ||
618 | // Note: this is a little endian printout of bytes. | |
619 | ||
85aaf69f | 620 | for &word in words { |
970d7e83 | 621 | let mut v = word; |
9cc50fc6 | 622 | for _ in 0..mem::size_of::<usize>() { |
1a4d82fc | 623 | result.push(sep); |
c34b1796 | 624 | result.push_str(&format!("{:02x}", v & 0xFF)); |
970d7e83 LB |
625 | v >>= 8; |
626 | sep = '-'; | |
627 | } | |
628 | } | |
1a4d82fc JJ |
629 | result.push(']'); |
630 | return result | |
970d7e83 LB |
631 | } |
632 | ||
633 | #[inline] | |
c34b1796 AL |
634 | fn bitwise<Op:BitwiseOperator>(out_vec: &mut [usize], |
635 | in_vec: &[usize], | |
1a4d82fc | 636 | op: &Op) -> bool { |
970d7e83 LB |
637 | assert_eq!(out_vec.len(), in_vec.len()); |
638 | let mut changed = false; | |
62682a34 | 639 | for (out_elt, in_elt) in out_vec.iter_mut().zip(in_vec) { |
1a4d82fc JJ |
640 | let old_val = *out_elt; |
641 | let new_val = op.join(old_val, *in_elt); | |
642 | *out_elt = new_val; | |
643 | changed |= old_val != new_val; | |
970d7e83 | 644 | } |
1a4d82fc | 645 | changed |
970d7e83 LB |
646 | } |
647 | ||
c34b1796 | 648 | fn set_bit(words: &mut [usize], bit: usize) -> bool { |
1a4d82fc JJ |
649 | debug!("set_bit: words={} bit={}", |
650 | mut_bits_to_string(words), bit_str(bit)); | |
9cc50fc6 SL |
651 | let usize_bits = mem::size_of::<usize>() * 8; |
652 | let word = bit / usize_bits; | |
653 | let bit_in_word = bit % usize_bits; | |
970d7e83 | 654 | let bit_mask = 1 << bit_in_word; |
54a0048b | 655 | debug!("word={} bit_in_word={} bit_mask={}", word, bit_in_word, bit_mask); |
970d7e83 LB |
656 | let oldv = words[word]; |
657 | let newv = oldv | bit_mask; | |
658 | words[word] = newv; | |
659 | oldv != newv | |
660 | } | |
661 | ||
c34b1796 | 662 | fn bit_str(bit: usize) -> String { |
3157f602 XL |
663 | let byte = bit >> 3; |
664 | let lobits = 1 << (bit & 0b111); | |
1a4d82fc | 665 | format!("[{}:{}-{:02x}]", bit, byte, lobits) |
970d7e83 LB |
666 | } |
667 | ||
1a4d82fc JJ |
668 | struct Union; |
669 | impl BitwiseOperator for Union { | |
c34b1796 | 670 | fn join(&self, a: usize, b: usize) -> usize { a | b } |
1a4d82fc JJ |
671 | } |
672 | struct Subtract; | |
673 | impl BitwiseOperator for Subtract { | |
c34b1796 | 674 | fn join(&self, a: usize, b: usize) -> usize { a & !b } |
970d7e83 | 675 | } |