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Commit | Line | Data |
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a7813a04 XL |
1 | //! A pass that promotes borrows of constant rvalues. |
2 | //! | |
3 | //! The rvalues considered constant are trees of temps, | |
4 | //! each with exactly one initialization, and holding | |
5 | //! a constant value with no interior mutability. | |
6 | //! They are placed into a new MIR constant body in | |
7 | //! `promoted` and the borrow rvalue is replaced with | |
8 | //! a `Literal::Promoted` using the index into `promoted` | |
9 | //! of that constant MIR. | |
10 | //! | |
11 | //! This pass assumes that every use is dominated by an | |
12 | //! initialization and can otherwise silence errors, if | |
13 | //! move analysis runs after promotion on broken MIR. | |
14 | ||
f9f354fc | 15 | use rustc_hir as hir; |
2b03887a | 16 | use rustc_middle::mir; |
04454e1e | 17 | use rustc_middle::mir::traversal::ReversePostorderIter; |
ba9703b0 XL |
18 | use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor}; |
19 | use rustc_middle::mir::*; | |
ba9703b0 | 20 | use rustc_middle::ty::subst::InternalSubsts; |
064997fb | 21 | use rustc_middle::ty::{self, List, TyCtxt, TypeVisitable}; |
fc512014 | 22 | use rustc_span::Span; |
a7813a04 | 23 | |
dfeec247 | 24 | use rustc_index::vec::{Idx, IndexVec}; |
a7813a04 | 25 | |
60c5eb7d | 26 | use std::cell::Cell; |
ba9703b0 | 27 | use std::{cmp, iter, mem}; |
a7813a04 | 28 | |
3c0e092e | 29 | use crate::transform::check_consts::{qualifs, ConstCx}; |
e74abb32 | 30 | |
60c5eb7d XL |
31 | /// A `MirPass` for promotion. |
32 | /// | |
17df50a5 XL |
33 | /// Promotion is the extraction of promotable temps into separate MIR bodies so they can have |
34 | /// `'static` lifetime. | |
60c5eb7d XL |
35 | /// |
36 | /// After this pass is run, `promoted_fragments` will hold the MIR body corresponding to each | |
dfeec247 | 37 | /// newly created `Constant`. |
60c5eb7d XL |
38 | #[derive(Default)] |
39 | pub struct PromoteTemps<'tcx> { | |
f9f354fc | 40 | pub promoted_fragments: Cell<IndexVec<Promoted, Body<'tcx>>>, |
60c5eb7d XL |
41 | } |
42 | ||
43 | impl<'tcx> MirPass<'tcx> for PromoteTemps<'tcx> { | |
29967ef6 | 44 | fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { |
60c5eb7d XL |
45 | // There's not really any point in promoting errorful MIR. |
46 | // | |
47 | // This does not include MIR that failed const-checking, which we still try to promote. | |
487cf647 FG |
48 | if let Err(_) = body.return_ty().error_reported() { |
49 | debug!("PromoteTemps: MIR had errors"); | |
60c5eb7d XL |
50 | return; |
51 | } | |
29967ef6 | 52 | if body.source.promoted.is_some() { |
60c5eb7d XL |
53 | return; |
54 | } | |
55 | ||
60c5eb7d | 56 | let mut rpo = traversal::reverse_postorder(body); |
29967ef6 | 57 | let ccx = ConstCx::new(tcx, body); |
04454e1e | 58 | let (mut temps, all_candidates) = collect_temps_and_candidates(&ccx, &mut rpo); |
60c5eb7d | 59 | |
04454e1e | 60 | let promotable_candidates = validate_candidates(&ccx, &mut temps, &all_candidates); |
60c5eb7d | 61 | |
29967ef6 | 62 | let promoted = promote_candidates(body, tcx, temps, promotable_candidates); |
60c5eb7d XL |
63 | self.promoted_fragments.set(promoted); |
64 | } | |
65 | } | |
66 | ||
a7813a04 XL |
67 | /// State of a temporary during collection and promotion. |
68 | #[derive(Copy, Clone, PartialEq, Eq, Debug)] | |
69 | pub enum TempState { | |
70 | /// No references to this temp. | |
71 | Undefined, | |
72 | /// One direct assignment and any number of direct uses. | |
73 | /// A borrow of this temp is promotable if the assigned | |
74 | /// value is qualified as constant. | |
04454e1e | 75 | Defined { location: Location, uses: usize, valid: Result<(), ()> }, |
a7813a04 XL |
76 | /// Any other combination of assignments/uses. |
77 | Unpromotable, | |
78 | /// This temp was part of an rvalue which got extracted | |
79 | /// during promotion and needs cleanup. | |
dfeec247 | 80 | PromotedOut, |
a7813a04 XL |
81 | } |
82 | ||
83 | impl TempState { | |
84 | pub fn is_promotable(&self) -> bool { | |
13cf67c4 | 85 | debug!("is_promotable: self={:?}", self); |
5869c6ff | 86 | matches!(self, TempState::Defined { .. }) |
a7813a04 XL |
87 | } |
88 | } | |
89 | ||
90 | /// A "root candidate" for promotion, which will become the | |
91 | /// returned value in a promoted MIR, unless it's a subset | |
92 | /// of a larger candidate. | |
e74abb32 | 93 | #[derive(Copy, Clone, PartialEq, Eq, Debug)] |
3c0e092e XL |
94 | pub struct Candidate { |
95 | location: Location, | |
e74abb32 XL |
96 | } |
97 | ||
e74abb32 | 98 | struct Collector<'a, 'tcx> { |
f9f354fc | 99 | ccx: &'a ConstCx<'a, 'tcx>, |
c30ab7b3 | 100 | temps: IndexVec<Local, TempState>, |
e74abb32 | 101 | candidates: Vec<Candidate>, |
a7813a04 XL |
102 | } |
103 | ||
e74abb32 | 104 | impl<'tcx> Visitor<'tcx> for Collector<'_, 'tcx> { |
064997fb | 105 | fn visit_local(&mut self, index: Local, context: PlaceContext, location: Location) { |
13cf67c4 | 106 | debug!("visit_local: index={:?} context={:?} location={:?}", index, context, location); |
48663c56 | 107 | // We're only interested in temporaries and the return place |
f9f354fc | 108 | match self.ccx.body.local_kind(index) { |
dfeec247 XL |
109 | LocalKind::Temp | LocalKind::ReturnPointer => {} |
110 | LocalKind::Arg | LocalKind::Var => return, | |
ea8adc8c | 111 | } |
c30ab7b3 | 112 | |
ea8adc8c XL |
113 | // Ignore drops, if the temp gets promoted, |
114 | // then it's constant and thus drop is noop. | |
60c5eb7d | 115 | // Non-uses are also irrelevant. |
13cf67c4 XL |
116 | if context.is_drop() || !context.is_use() { |
117 | debug!( | |
118 | "visit_local: context.is_drop={:?} context.is_use={:?}", | |
dfeec247 XL |
119 | context.is_drop(), |
120 | context.is_use(), | |
13cf67c4 | 121 | ); |
ea8adc8c XL |
122 | return; |
123 | } | |
a7813a04 | 124 | |
ea8adc8c | 125 | let temp = &mut self.temps[index]; |
13cf67c4 | 126 | debug!("visit_local: temp={:?}", temp); |
ea8adc8c XL |
127 | if *temp == TempState::Undefined { |
128 | match context { | |
dfeec247 XL |
129 | PlaceContext::MutatingUse(MutatingUseContext::Store) |
130 | | PlaceContext::MutatingUse(MutatingUseContext::Call) => { | |
04454e1e | 131 | *temp = TempState::Defined { location, uses: 0, valid: Err(()) }; |
32a655c1 | 132 | return; |
a7813a04 | 133 | } |
ea8adc8c | 134 | _ => { /* mark as unpromotable below */ } |
a7813a04 | 135 | } |
9c376795 | 136 | } else if let TempState::Defined { uses, .. } = temp { |
ea8adc8c | 137 | // We always allow borrows, even mutable ones, as we need |
0731742a | 138 | // to promote mutable borrows of some ZSTs e.g., `&mut []`. |
dfeec247 XL |
139 | let allowed_use = match context { |
140 | PlaceContext::MutatingUse(MutatingUseContext::Borrow) | |
141 | | PlaceContext::NonMutatingUse(_) => true, | |
142 | PlaceContext::MutatingUse(_) | PlaceContext::NonUse(_) => false, | |
143 | }; | |
13cf67c4 | 144 | debug!("visit_local: allowed_use={:?}", allowed_use); |
ea8adc8c XL |
145 | if allowed_use { |
146 | *uses += 1; | |
147 | return; | |
148 | } | |
149 | /* mark as unpromotable below */ | |
a7813a04 | 150 | } |
ea8adc8c | 151 | *temp = TempState::Unpromotable; |
a7813a04 XL |
152 | } |
153 | ||
e74abb32 XL |
154 | fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) { |
155 | self.super_rvalue(rvalue, location); | |
156 | ||
157 | match *rvalue { | |
158 | Rvalue::Ref(..) => { | |
3c0e092e | 159 | self.candidates.push(Candidate { location }); |
e74abb32 | 160 | } |
e74abb32 XL |
161 | _ => {} |
162 | } | |
163 | } | |
a7813a04 XL |
164 | } |
165 | ||
a2a8927a XL |
166 | pub fn collect_temps_and_candidates<'tcx>( |
167 | ccx: &ConstCx<'_, 'tcx>, | |
04454e1e | 168 | rpo: &mut ReversePostorderIter<'_, 'tcx>, |
e74abb32 XL |
169 | ) -> (IndexVec<Local, TempState>, Vec<Candidate>) { |
170 | let mut collector = Collector { | |
f9f354fc | 171 | temps: IndexVec::from_elem(TempState::Undefined, &ccx.body.local_decls), |
e74abb32 | 172 | candidates: vec![], |
f9f354fc | 173 | ccx, |
a7813a04 XL |
174 | }; |
175 | for (bb, data) in rpo { | |
176 | collector.visit_basic_block_data(bb, data); | |
177 | } | |
e74abb32 XL |
178 | (collector.temps, collector.candidates) |
179 | } | |
180 | ||
181 | /// Checks whether locals that appear in a promotion context (`Candidate`) are actually promotable. | |
182 | /// | |
183 | /// This wraps an `Item`, and has access to all fields of that `Item` via `Deref` coercion. | |
184 | struct Validator<'a, 'tcx> { | |
f9f354fc | 185 | ccx: &'a ConstCx<'a, 'tcx>, |
04454e1e | 186 | temps: &'a mut IndexVec<Local, TempState>, |
e74abb32 XL |
187 | } |
188 | ||
a2a8927a | 189 | impl<'a, 'tcx> std::ops::Deref for Validator<'a, 'tcx> { |
f9f354fc | 190 | type Target = ConstCx<'a, 'tcx>; |
e74abb32 XL |
191 | |
192 | fn deref(&self) -> &Self::Target { | |
f9f354fc | 193 | &self.ccx |
e74abb32 XL |
194 | } |
195 | } | |
196 | ||
197 | struct Unpromotable; | |
198 | ||
199 | impl<'tcx> Validator<'_, 'tcx> { | |
04454e1e | 200 | fn validate_candidate(&mut self, candidate: Candidate) -> Result<(), Unpromotable> { |
3c0e092e XL |
201 | let loc = candidate.location; |
202 | let statement = &self.body[loc.block].statements[loc.statement_index]; | |
203 | match &statement.kind { | |
204 | StatementKind::Assign(box (_, Rvalue::Ref(_, kind, place))) => { | |
205 | // We can only promote interior borrows of promotable temps (non-temps | |
206 | // don't get promoted anyway). | |
207 | self.validate_local(place.local)?; | |
208 | ||
209 | // The reference operation itself must be promotable. | |
210 | // (Needs to come after `validate_local` to avoid ICEs.) | |
211 | self.validate_ref(*kind, place)?; | |
e74abb32 | 212 | |
3c0e092e XL |
213 | // We do not check all the projections (they do not get promoted anyway), |
214 | // but we do stay away from promoting anything involving a dereference. | |
215 | if place.projection.contains(&ProjectionElem::Deref) { | |
216 | return Err(Unpromotable); | |
217 | } | |
e74abb32 | 218 | |
3c0e092e | 219 | Ok(()) |
e74abb32 | 220 | } |
3c0e092e | 221 | _ => bug!(), |
e74abb32 XL |
222 | } |
223 | } | |
224 | ||
225 | // FIXME(eddyb) maybe cache this? | |
04454e1e | 226 | fn qualif_local<Q: qualifs::Qualif>(&mut self, local: Local) -> bool { |
e74abb32 XL |
227 | if let TempState::Defined { location: loc, .. } = self.temps[local] { |
228 | let num_stmts = self.body[loc.block].statements.len(); | |
229 | ||
230 | if loc.statement_index < num_stmts { | |
231 | let statement = &self.body[loc.block].statements[loc.statement_index]; | |
232 | match &statement.kind { | |
ba9703b0 | 233 | StatementKind::Assign(box (_, rhs)) => qualifs::in_rvalue::<Q, _>( |
f9f354fc | 234 | &self.ccx, |
ba9703b0 XL |
235 | &mut |l| self.qualif_local::<Q>(l), |
236 | rhs, | |
237 | ), | |
e74abb32 | 238 | _ => { |
dfeec247 XL |
239 | span_bug!( |
240 | statement.source_info.span, | |
241 | "{:?} is not an assignment", | |
242 | statement | |
243 | ); | |
e74abb32 XL |
244 | } |
245 | } | |
246 | } else { | |
247 | let terminator = self.body[loc.block].terminator(); | |
248 | match &terminator.kind { | |
ba9703b0 | 249 | TerminatorKind::Call { .. } => { |
e74abb32 | 250 | let return_ty = self.body.local_decls[local].ty; |
f9f354fc | 251 | Q::in_any_value_of_ty(&self.ccx, return_ty) |
e74abb32 XL |
252 | } |
253 | kind => { | |
254 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); | |
255 | } | |
256 | } | |
257 | } | |
258 | } else { | |
9c376795 | 259 | false |
e74abb32 XL |
260 | } |
261 | } | |
262 | ||
04454e1e FG |
263 | fn validate_local(&mut self, local: Local) -> Result<(), Unpromotable> { |
264 | if let TempState::Defined { location: loc, uses, valid } = self.temps[local] { | |
9c376795 FG |
265 | // We cannot promote things that need dropping, since the promoted value |
266 | // would not get dropped. | |
267 | if self.qualif_local::<qualifs::NeedsDrop>(local) { | |
268 | return Err(Unpromotable); | |
269 | } | |
04454e1e FG |
270 | valid.or_else(|_| { |
271 | let ok = { | |
272 | let block = &self.body[loc.block]; | |
273 | let num_stmts = block.statements.len(); | |
274 | ||
275 | if loc.statement_index < num_stmts { | |
276 | let statement = &block.statements[loc.statement_index]; | |
277 | match &statement.kind { | |
278 | StatementKind::Assign(box (_, rhs)) => self.validate_rvalue(rhs), | |
279 | _ => { | |
280 | span_bug!( | |
281 | statement.source_info.span, | |
282 | "{:?} is not an assignment", | |
283 | statement | |
284 | ); | |
285 | } | |
286 | } | |
287 | } else { | |
288 | let terminator = block.terminator(); | |
289 | match &terminator.kind { | |
290 | TerminatorKind::Call { func, args, .. } => { | |
291 | self.validate_call(func, args) | |
292 | } | |
293 | TerminatorKind::Yield { .. } => Err(Unpromotable), | |
294 | kind => { | |
295 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); | |
296 | } | |
297 | } | |
e74abb32 | 298 | } |
04454e1e FG |
299 | }; |
300 | self.temps[local] = match ok { | |
301 | Ok(()) => TempState::Defined { location: loc, uses, valid: Ok(()) }, | |
302 | Err(_) => TempState::Unpromotable, | |
303 | }; | |
304 | ok | |
305 | }) | |
e74abb32 XL |
306 | } else { |
307 | Err(Unpromotable) | |
308 | } | |
309 | } | |
310 | ||
04454e1e | 311 | fn validate_place(&mut self, place: PlaceRef<'tcx>) -> Result<(), Unpromotable> { |
5869c6ff XL |
312 | match place.last_projection() { |
313 | None => self.validate_local(place.local), | |
314 | Some((place_base, elem)) => { | |
1b1a35ee | 315 | // Validate topmost projection, then recurse. |
5869c6ff | 316 | match elem { |
3dfed10e | 317 | ProjectionElem::Deref => { |
1b1a35ee | 318 | let mut promotable = false; |
487cf647 FG |
319 | // When a static is used by-value, that gets desugared to `*STATIC_ADDR`, |
320 | // and we need to be able to promote this. So check if this deref matches | |
321 | // that specific pattern. | |
322 | ||
5869c6ff XL |
323 | // We need to make sure this is a `Deref` of a local with no further projections. |
324 | // Discussion can be found at | |
325 | // https://github.com/rust-lang/rust/pull/74945#discussion_r463063247 | |
326 | if let Some(local) = place_base.as_local() { | |
5869c6ff XL |
327 | if let TempState::Defined { location, .. } = self.temps[local] { |
328 | let def_stmt = self.body[location.block] | |
329 | .statements | |
330 | .get(location.statement_index); | |
331 | if let Some(Statement { | |
332 | kind: | |
333 | StatementKind::Assign(box ( | |
334 | _, | |
335 | Rvalue::Use(Operand::Constant(c)), | |
336 | )), | |
337 | .. | |
338 | }) = def_stmt | |
339 | { | |
340 | if let Some(did) = c.check_static_ptr(self.tcx) { | |
341 | // Evaluating a promoted may not read statics except if it got | |
342 | // promoted from a static (this is a CTFE check). So we | |
343 | // can only promote static accesses inside statics. | |
344 | if let Some(hir::ConstContext::Static(..)) = self.const_kind | |
3dfed10e | 345 | { |
5869c6ff XL |
346 | if !self.tcx.is_thread_local_static(did) { |
347 | promotable = true; | |
348 | } | |
3dfed10e XL |
349 | } |
350 | } | |
351 | } | |
352 | } | |
353 | } | |
1b1a35ee | 354 | if !promotable { |
3dfed10e XL |
355 | return Err(Unpromotable); |
356 | } | |
357 | } | |
2b03887a | 358 | ProjectionElem::OpaqueCast(..) | ProjectionElem::Downcast(..) => { |
dfeec247 XL |
359 | return Err(Unpromotable); |
360 | } | |
e74abb32 | 361 | |
dfeec247 | 362 | ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => {} |
e74abb32 XL |
363 | |
364 | ProjectionElem::Index(local) => { | |
17df50a5 XL |
365 | let mut promotable = false; |
366 | // Only accept if we can predict the index and are indexing an array. | |
367 | let val = | |
368 | if let TempState::Defined { location: loc, .. } = self.temps[local] { | |
5869c6ff XL |
369 | let block = &self.body[loc.block]; |
370 | if loc.statement_index < block.statements.len() { | |
371 | let statement = &block.statements[loc.statement_index]; | |
372 | match &statement.kind { | |
373 | StatementKind::Assign(box ( | |
374 | _, | |
375 | Rvalue::Use(Operand::Constant(c)), | |
376 | )) => c.literal.try_eval_usize(self.tcx, self.param_env), | |
377 | _ => None, | |
378 | } | |
379 | } else { | |
380 | None | |
381 | } | |
382 | } else { | |
383 | None | |
384 | }; | |
17df50a5 XL |
385 | if let Some(idx) = val { |
386 | // Determine the type of the thing we are indexing. | |
387 | let ty = place_base.ty(self.body, self.tcx).ty; | |
388 | match ty.kind() { | |
389 | ty::Array(_, len) => { | |
390 | // It's an array; determine its length. | |
391 | if let Some(len) = len.try_eval_usize(self.tcx, self.param_env) | |
392 | { | |
393 | // If the index is in-bounds, go ahead. | |
394 | if idx < len { | |
395 | promotable = true; | |
5869c6ff XL |
396 | } |
397 | } | |
5869c6ff | 398 | } |
17df50a5 | 399 | _ => {} |
5869c6ff XL |
400 | } |
401 | } | |
17df50a5 XL |
402 | if !promotable { |
403 | return Err(Unpromotable); | |
404 | } | |
405 | ||
e74abb32 XL |
406 | self.validate_local(local)?; |
407 | } | |
408 | ||
409 | ProjectionElem::Field(..) => { | |
5869c6ff | 410 | let base_ty = place_base.ty(self.body, self.tcx).ty; |
17df50a5 | 411 | if base_ty.is_union() { |
29967ef6 | 412 | // No promotion of union field accesses. |
17df50a5 | 413 | return Err(Unpromotable); |
e74abb32 XL |
414 | } |
415 | } | |
416 | } | |
417 | ||
5869c6ff | 418 | self.validate_place(place_base) |
e74abb32 XL |
419 | } |
420 | } | |
421 | } | |
422 | ||
04454e1e | 423 | fn validate_operand(&mut self, operand: &Operand<'tcx>) -> Result<(), Unpromotable> { |
e74abb32 | 424 | match operand { |
dfeec247 | 425 | Operand::Copy(place) | Operand::Move(place) => self.validate_place(place.as_ref()), |
e74abb32 | 426 | |
60c5eb7d XL |
427 | // The qualifs for a constant (e.g. `HasMutInterior`) are checked in |
428 | // `validate_rvalue` upon access. | |
429 | Operand::Constant(c) => { | |
430 | if let Some(def_id) = c.check_static_ptr(self.tcx) { | |
431 | // Only allow statics (not consts) to refer to other statics. | |
432 | // FIXME(eddyb) does this matter at all for promotion? | |
1b1a35ee XL |
433 | // FIXME(RalfJung) it makes little sense to not promote this in `fn`/`const fn`, |
434 | // and in `const` this cannot occur anyway. The only concern is that we might | |
435 | // promote even `let x = &STATIC` which would be useless, but this applies to | |
436 | // promotion inside statics as well. | |
f9f354fc | 437 | let is_static = matches!(self.const_kind, Some(hir::ConstContext::Static(_))); |
60c5eb7d XL |
438 | if !is_static { |
439 | return Err(Unpromotable); | |
440 | } | |
441 | ||
f9f354fc | 442 | let is_thread_local = self.tcx.is_thread_local_static(def_id); |
60c5eb7d XL |
443 | if is_thread_local { |
444 | return Err(Unpromotable); | |
e74abb32 XL |
445 | } |
446 | } | |
447 | ||
448 | Ok(()) | |
dfeec247 | 449 | } |
e74abb32 XL |
450 | } |
451 | } | |
452 | ||
04454e1e | 453 | fn validate_ref(&mut self, kind: BorrowKind, place: &Place<'tcx>) -> Result<(), Unpromotable> { |
5869c6ff XL |
454 | match kind { |
455 | // Reject these borrow types just to be safe. | |
456 | // FIXME(RalfJung): could we allow them? Should we? No point in it until we have a usecase. | |
457 | BorrowKind::Shallow | BorrowKind::Unique => return Err(Unpromotable), | |
458 | ||
459 | BorrowKind::Shared => { | |
460 | let has_mut_interior = self.qualif_local::<qualifs::HasMutInterior>(place.local); | |
461 | if has_mut_interior { | |
1b1a35ee | 462 | return Err(Unpromotable); |
e74abb32 XL |
463 | } |
464 | } | |
465 | ||
5869c6ff XL |
466 | BorrowKind::Mut { .. } => { |
467 | let ty = place.ty(self.body, self.tcx).ty; | |
468 | ||
469 | // In theory, any zero-sized value could be borrowed | |
470 | // mutably without consequences. However, only &mut [] | |
471 | // is allowed right now. | |
472 | if let ty::Array(_, len) = ty.kind() { | |
473 | match len.try_eval_usize(self.tcx, self.param_env) { | |
474 | Some(0) => {} | |
475 | _ => return Err(Unpromotable), | |
476 | } | |
477 | } else { | |
e74abb32 XL |
478 | return Err(Unpromotable); |
479 | } | |
480 | } | |
e74abb32 XL |
481 | } |
482 | ||
5869c6ff XL |
483 | Ok(()) |
484 | } | |
485 | ||
04454e1e | 486 | fn validate_rvalue(&mut self, rvalue: &Rvalue<'tcx>) -> Result<(), Unpromotable> { |
e74abb32 | 487 | match rvalue { |
5869c6ff XL |
488 | Rvalue::Use(operand) | Rvalue::Repeat(operand, _) => { |
489 | self.validate_operand(operand)?; | |
490 | } | |
064997fb FG |
491 | Rvalue::CopyForDeref(place) => { |
492 | let op = &Operand::Copy(*place); | |
493 | self.validate_operand(op)? | |
494 | } | |
5869c6ff XL |
495 | |
496 | Rvalue::Discriminant(place) | Rvalue::Len(place) => { | |
497 | self.validate_place(place.as_ref())? | |
498 | } | |
499 | ||
500 | Rvalue::ThreadLocalRef(_) => return Err(Unpromotable), | |
501 | ||
923072b8 FG |
502 | // ptr-to-int casts are not possible in consts and thus not promotable |
503 | Rvalue::Cast(CastKind::PointerExposeAddress, _, _) => return Err(Unpromotable), | |
5869c6ff | 504 | |
923072b8 FG |
505 | // all other casts including int-to-ptr casts are fine, they just use the integer value |
506 | // at pointer type. | |
507 | Rvalue::Cast(_, operand, _) => { | |
5869c6ff XL |
508 | self.validate_operand(operand)?; |
509 | } | |
510 | ||
511 | Rvalue::NullaryOp(op, _) => match op { | |
5869c6ff | 512 | NullOp::SizeOf => {} |
c295e0f8 | 513 | NullOp::AlignOf => {} |
5869c6ff | 514 | }, |
f9f354fc | 515 | |
c295e0f8 XL |
516 | Rvalue::ShallowInitBox(_, _) => return Err(Unpromotable), |
517 | ||
5869c6ff XL |
518 | Rvalue::UnaryOp(op, operand) => { |
519 | match op { | |
520 | // These operations can never fail. | |
521 | UnOp::Neg | UnOp::Not => {} | |
522 | } | |
e74abb32 | 523 | |
5869c6ff XL |
524 | self.validate_operand(operand)?; |
525 | } | |
526 | ||
6a06907d | 527 | Rvalue::BinaryOp(op, box (lhs, rhs)) | Rvalue::CheckedBinaryOp(op, box (lhs, rhs)) => { |
5869c6ff XL |
528 | let op = *op; |
529 | let lhs_ty = lhs.ty(self.body, self.tcx); | |
530 | ||
531 | if let ty::RawPtr(_) | ty::FnPtr(..) = lhs_ty.kind() { | |
532 | // Raw and fn pointer operations are not allowed inside consts and thus not promotable. | |
533 | assert!(matches!( | |
534 | op, | |
535 | BinOp::Eq | |
536 | | BinOp::Ne | |
537 | | BinOp::Le | |
538 | | BinOp::Lt | |
539 | | BinOp::Ge | |
540 | | BinOp::Gt | |
541 | | BinOp::Offset | |
542 | )); | |
543 | return Err(Unpromotable); | |
544 | } | |
e74abb32 | 545 | |
5869c6ff XL |
546 | match op { |
547 | BinOp::Div | BinOp::Rem => { | |
17df50a5 | 548 | if lhs_ty.is_integral() { |
5869c6ff XL |
549 | // Integer division: the RHS must be a non-zero const. |
550 | let const_val = match rhs { | |
551 | Operand::Constant(c) => { | |
552 | c.literal.try_eval_bits(self.tcx, self.param_env, lhs_ty) | |
553 | } | |
554 | _ => None, | |
555 | }; | |
556 | match const_val { | |
557 | Some(x) if x != 0 => {} // okay | |
558 | _ => return Err(Unpromotable), // value not known or 0 -- not okay | |
559 | } | |
560 | } | |
561 | } | |
562 | // The remaining operations can never fail. | |
563 | BinOp::Eq | |
564 | | BinOp::Ne | |
565 | | BinOp::Le | |
566 | | BinOp::Lt | |
567 | | BinOp::Ge | |
568 | | BinOp::Gt | |
569 | | BinOp::Offset | |
570 | | BinOp::Add | |
571 | | BinOp::Sub | |
572 | | BinOp::Mul | |
573 | | BinOp::BitXor | |
574 | | BinOp::BitAnd | |
575 | | BinOp::BitOr | |
576 | | BinOp::Shl | |
577 | | BinOp::Shr => {} | |
578 | } | |
e74abb32 | 579 | |
e74abb32 | 580 | self.validate_operand(lhs)?; |
5869c6ff | 581 | self.validate_operand(rhs)?; |
e74abb32 XL |
582 | } |
583 | ||
dfeec247 | 584 | Rvalue::AddressOf(_, place) => { |
1b1a35ee XL |
585 | // We accept `&raw *`, i.e., raw reborrows -- creating a raw pointer is |
586 | // no problem, only using it is. | |
5869c6ff XL |
587 | if let Some((place_base, ProjectionElem::Deref)) = place.as_ref().last_projection() |
588 | { | |
589 | let base_ty = place_base.ty(self.body, self.tcx).ty; | |
1b1a35ee | 590 | if let ty::Ref(..) = base_ty.kind() { |
5869c6ff | 591 | return self.validate_place(place_base); |
dfeec247 XL |
592 | } |
593 | } | |
5869c6ff | 594 | return Err(Unpromotable); |
dfeec247 XL |
595 | } |
596 | ||
e74abb32 | 597 | Rvalue::Ref(_, kind, place) => { |
e74abb32 | 598 | // Special-case reborrows to be more like a copy of the reference. |
5869c6ff XL |
599 | let mut place_simplified = place.as_ref(); |
600 | if let Some((place_base, ProjectionElem::Deref)) = | |
601 | place_simplified.last_projection() | |
602 | { | |
603 | let base_ty = place_base.ty(self.body, self.tcx).ty; | |
1b1a35ee | 604 | if let ty::Ref(..) = base_ty.kind() { |
5869c6ff | 605 | place_simplified = place_base; |
e74abb32 XL |
606 | } |
607 | } | |
608 | ||
5869c6ff | 609 | self.validate_place(place_simplified)?; |
e74abb32 | 610 | |
5869c6ff XL |
611 | // Check that the reference is fine (using the original place!). |
612 | // (Needs to come after `validate_place` to avoid ICEs.) | |
613 | self.validate_ref(*kind, place)?; | |
e74abb32 XL |
614 | } |
615 | ||
5869c6ff | 616 | Rvalue::Aggregate(_, operands) => { |
e74abb32 XL |
617 | for o in operands { |
618 | self.validate_operand(o)?; | |
619 | } | |
e74abb32 XL |
620 | } |
621 | } | |
5869c6ff XL |
622 | |
623 | Ok(()) | |
e74abb32 XL |
624 | } |
625 | ||
626 | fn validate_call( | |
04454e1e | 627 | &mut self, |
e74abb32 XL |
628 | callee: &Operand<'tcx>, |
629 | args: &[Operand<'tcx>], | |
630 | ) -> Result<(), Unpromotable> { | |
f9f354fc | 631 | let fn_ty = callee.ty(self.body, self.tcx); |
e74abb32 | 632 | |
17df50a5 | 633 | // Inside const/static items, we promote all (eligible) function calls. |
29967ef6 | 634 | // Everywhere else, we require `#[rustc_promotable]` on the callee. |
17df50a5 XL |
635 | let promote_all_const_fn = matches!( |
636 | self.const_kind, | |
637 | Some(hir::ConstContext::Static(_) | hir::ConstContext::Const) | |
638 | ); | |
29967ef6 | 639 | if !promote_all_const_fn { |
1b1a35ee | 640 | if let ty::FnDef(def_id, _) = *fn_ty.kind() { |
e74abb32 XL |
641 | // Never promote runtime `const fn` calls of |
642 | // functions without `#[rustc_promotable]`. | |
643 | if !self.tcx.is_promotable_const_fn(def_id) { | |
644 | return Err(Unpromotable); | |
645 | } | |
646 | } | |
647 | } | |
648 | ||
1b1a35ee | 649 | let is_const_fn = match *fn_ty.kind() { |
3c0e092e | 650 | ty::FnDef(def_id, _) => self.tcx.is_const_fn_raw(def_id), |
e74abb32 XL |
651 | _ => false, |
652 | }; | |
653 | if !is_const_fn { | |
654 | return Err(Unpromotable); | |
655 | } | |
656 | ||
657 | self.validate_operand(callee)?; | |
658 | for arg in args { | |
659 | self.validate_operand(arg)?; | |
660 | } | |
661 | ||
662 | Ok(()) | |
663 | } | |
664 | } | |
665 | ||
666 | // FIXME(eddyb) remove the differences for promotability in `static`, `const`, `const fn`. | |
667 | pub fn validate_candidates( | |
f9f354fc | 668 | ccx: &ConstCx<'_, '_>, |
04454e1e | 669 | temps: &mut IndexVec<Local, TempState>, |
e74abb32 XL |
670 | candidates: &[Candidate], |
671 | ) -> Vec<Candidate> { | |
04454e1e | 672 | let mut validator = Validator { ccx, temps }; |
e74abb32 | 673 | |
dfeec247 XL |
674 | candidates |
675 | .iter() | |
676 | .copied() | |
17df50a5 | 677 | .filter(|&candidate| validator.validate_candidate(candidate).is_ok()) |
dfeec247 | 678 | .collect() |
a7813a04 XL |
679 | } |
680 | ||
dc9dc135 XL |
681 | struct Promoter<'a, 'tcx> { |
682 | tcx: TyCtxt<'tcx>, | |
f9f354fc XL |
683 | source: &'a mut Body<'tcx>, |
684 | promoted: Body<'tcx>, | |
c30ab7b3 | 685 | temps: &'a mut IndexVec<Local, TempState>, |
dfeec247 | 686 | extra_statements: &'a mut Vec<(Location, Statement<'tcx>)>, |
a7813a04 XL |
687 | |
688 | /// If true, all nested temps are also kept in the | |
689 | /// source MIR, not moved to the promoted MIR. | |
dc9dc135 | 690 | keep_original: bool, |
a7813a04 XL |
691 | } |
692 | ||
693 | impl<'a, 'tcx> Promoter<'a, 'tcx> { | |
694 | fn new_block(&mut self) -> BasicBlock { | |
3157f602 XL |
695 | let span = self.promoted.span; |
696 | self.promoted.basic_blocks_mut().push(BasicBlockData { | |
a7813a04 XL |
697 | statements: vec![], |
698 | terminator: Some(Terminator { | |
f9f354fc | 699 | source_info: SourceInfo::outermost(span), |
dfeec247 | 700 | kind: TerminatorKind::Return, |
a7813a04 | 701 | }), |
dfeec247 | 702 | is_cleanup: false, |
3157f602 | 703 | }) |
a7813a04 XL |
704 | } |
705 | ||
c30ab7b3 | 706 | fn assign(&mut self, dest: Local, rvalue: Rvalue<'tcx>, span: Span) { |
f2b60f7d | 707 | let last = self.promoted.basic_blocks.last().unwrap(); |
3157f602 | 708 | let data = &mut self.promoted[last]; |
a7813a04 | 709 | data.statements.push(Statement { |
f9f354fc | 710 | source_info: SourceInfo::outermost(span), |
94222f64 | 711 | kind: StatementKind::Assign(Box::new((Place::from(dest), rvalue))), |
a7813a04 XL |
712 | }); |
713 | } | |
714 | ||
e74abb32 XL |
715 | fn is_temp_kind(&self, local: Local) -> bool { |
716 | self.source.local_kind(local) == LocalKind::Temp | |
717 | } | |
718 | ||
9fa01778 | 719 | /// Copies the initialization of this temp to the |
a7813a04 | 720 | /// promoted MIR, recursing through temps. |
c30ab7b3 | 721 | fn promote_temp(&mut self, temp: Local) -> Local { |
a7813a04 | 722 | let old_keep_original = self.keep_original; |
476ff2be | 723 | let loc = match self.temps[temp] { |
04454e1e | 724 | TempState::Defined { location, uses, .. } if uses > 0 => { |
a7813a04 XL |
725 | if uses > 1 { |
726 | self.keep_original = true; | |
727 | } | |
476ff2be | 728 | location |
a7813a04 | 729 | } |
dfeec247 XL |
730 | state => { |
731 | span_bug!(self.promoted.span, "{:?} not promotable: {:?}", temp, state); | |
a7813a04 XL |
732 | } |
733 | }; | |
734 | if !self.keep_original { | |
3157f602 | 735 | self.temps[temp] = TempState::PromotedOut; |
a7813a04 XL |
736 | } |
737 | ||
e74abb32 | 738 | let num_stmts = self.source[loc.block].statements.len(); |
f9f354fc | 739 | let new_temp = self.promoted.local_decls.push(LocalDecl::new( |
dfeec247 XL |
740 | self.source.local_decls[temp].ty, |
741 | self.source.local_decls[temp].source_info.span, | |
742 | )); | |
476ff2be | 743 | |
dfeec247 | 744 | debug!("promote({:?} @ {:?}/{:?}, {:?})", temp, loc, num_stmts, self.keep_original); |
a7813a04 XL |
745 | |
746 | // First, take the Rvalue or Call out of the source MIR, | |
747 | // or duplicate it, depending on keep_original. | |
e74abb32 | 748 | if loc.statement_index < num_stmts { |
e1599b0c | 749 | let (mut rvalue, source_info) = { |
476ff2be | 750 | let statement = &mut self.source[loc.block].statements[loc.statement_index]; |
9c376795 | 751 | let StatementKind::Assign(box (_, rhs)) = &mut statement.kind else { |
5e7ed085 FG |
752 | span_bug!( |
753 | statement.source_info.span, | |
754 | "{:?} is not an assignment", | |
755 | statement | |
756 | ); | |
476ff2be SL |
757 | }; |
758 | ||
dfeec247 XL |
759 | ( |
760 | if self.keep_original { | |
761 | rhs.clone() | |
762 | } else { | |
94222f64 | 763 | let unit = Rvalue::Use(Operand::Constant(Box::new(Constant { |
ba9703b0 XL |
764 | span: statement.source_info.span, |
765 | user_ty: None, | |
923072b8 | 766 | literal: ConstantKind::zero_sized(self.tcx.types.unit), |
94222f64 | 767 | }))); |
dfeec247 XL |
768 | mem::replace(rhs, unit) |
769 | }, | |
770 | statement.source_info, | |
771 | ) | |
5bcae85e | 772 | }; |
476ff2be SL |
773 | |
774 | self.visit_rvalue(&mut rvalue, loc); | |
775 | self.assign(new_temp, rvalue, source_info.span); | |
a7813a04 | 776 | } else { |
476ff2be SL |
777 | let terminator = if self.keep_original { |
778 | self.source[loc.block].terminator().clone() | |
779 | } else { | |
780 | let terminator = self.source[loc.block].terminator_mut(); | |
9c376795 FG |
781 | let target = match &terminator.kind { |
782 | TerminatorKind::Call { target: Some(target), .. } => *target, | |
783 | kind => { | |
476ff2be SL |
784 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); |
785 | } | |
786 | }; | |
787 | Terminator { | |
788 | source_info: terminator.source_info, | |
dfeec247 | 789 | kind: mem::replace(&mut terminator.kind, TerminatorKind::Goto { target }), |
a7813a04 XL |
790 | } |
791 | }; | |
a7813a04 | 792 | |
476ff2be | 793 | match terminator.kind { |
f035d41b | 794 | TerminatorKind::Call { mut func, mut args, from_hir_call, fn_span, .. } => { |
476ff2be SL |
795 | self.visit_operand(&mut func, loc); |
796 | for arg in &mut args { | |
797 | self.visit_operand(arg, loc); | |
798 | } | |
a7813a04 | 799 | |
f2b60f7d | 800 | let last = self.promoted.basic_blocks.last().unwrap(); |
476ff2be | 801 | let new_target = self.new_block(); |
a7813a04 | 802 | |
476ff2be SL |
803 | *self.promoted[last].terminator_mut() = Terminator { |
804 | kind: TerminatorKind::Call { | |
3b2f2976 XL |
805 | func, |
806 | args, | |
476ff2be | 807 | cleanup: None, |
923072b8 FG |
808 | destination: Place::from(new_temp), |
809 | target: Some(new_target), | |
0bf4aa26 | 810 | from_hir_call, |
f035d41b | 811 | fn_span, |
476ff2be | 812 | }, |
29967ef6 | 813 | source_info: SourceInfo::outermost(terminator.source_info.span), |
476ff2be SL |
814 | ..terminator |
815 | }; | |
a7813a04 | 816 | } |
9c376795 | 817 | kind => { |
476ff2be SL |
818 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); |
819 | } | |
820 | }; | |
821 | }; | |
a7813a04 | 822 | |
a7813a04 | 823 | self.keep_original = old_keep_original; |
3157f602 | 824 | new_temp |
a7813a04 XL |
825 | } |
826 | ||
3c0e092e | 827 | fn promote_candidate(mut self, candidate: Candidate, next_promoted_id: usize) -> Body<'tcx> { |
29967ef6 | 828 | let def = self.source.source.with_opt_param(); |
dfeec247 | 829 | let mut rvalue = { |
94b46f34 | 830 | let promoted = &mut self.promoted; |
e1599b0c XL |
831 | let promoted_id = Promoted::new(next_promoted_id); |
832 | let tcx = self.tcx; | |
dfeec247 | 833 | let mut promoted_operand = |ty, span| { |
94b46f34 | 834 | promoted.span = span; |
f9f354fc | 835 | promoted.local_decls[RETURN_PLACE] = LocalDecl::new(ty, span); |
f2b60f7d | 836 | let substs = tcx.erase_regions(InternalSubsts::identity_for_item(tcx, def.did)); |
2b03887a | 837 | let uneval = mir::UnevaluatedConst { def, substs, promoted: Some(promoted_id) }; |
dfeec247 XL |
838 | |
839 | Operand::Constant(Box::new(Constant { | |
840 | span, | |
841 | user_ty: None, | |
f2b60f7d | 842 | literal: ConstantKind::Unevaluated(uneval, ty), |
dfeec247 | 843 | })) |
94b46f34 | 844 | }; |
f2b60f7d | 845 | |
064997fb FG |
846 | let blocks = self.source.basic_blocks.as_mut(); |
847 | let local_decls = &mut self.source.local_decls; | |
3c0e092e XL |
848 | let loc = candidate.location; |
849 | let statement = &mut blocks[loc.block].statements[loc.statement_index]; | |
9c376795 FG |
850 | let StatementKind::Assign(box (_, Rvalue::Ref(region, borrow_kind, place))) = &mut statement.kind else { |
851 | bug!() | |
852 | }; | |
3c0e092e | 853 | |
9c376795 FG |
854 | // Use the underlying local for this (necessarily interior) borrow. |
855 | let ty = local_decls[place.local].ty; | |
856 | let span = statement.source_info.span; | |
857 | ||
858 | let ref_ty = tcx.mk_ref( | |
859 | tcx.lifetimes.re_erased, | |
860 | ty::TypeAndMut { ty, mutbl: borrow_kind.to_mutbl_lossy() }, | |
861 | ); | |
862 | ||
863 | *region = tcx.lifetimes.re_erased; | |
864 | ||
865 | let mut projection = vec![PlaceElem::Deref]; | |
866 | projection.extend(place.projection); | |
867 | place.projection = tcx.intern_place_elems(&projection); | |
868 | ||
869 | // Create a temp to hold the promoted reference. | |
870 | // This is because `*r` requires `r` to be a local, | |
871 | // otherwise we would use the `promoted` directly. | |
872 | let mut promoted_ref = LocalDecl::new(ref_ty, span); | |
873 | promoted_ref.source_info = statement.source_info; | |
874 | let promoted_ref = local_decls.push(promoted_ref); | |
875 | assert_eq!(self.temps.push(TempState::Unpromotable), promoted_ref); | |
876 | ||
877 | let promoted_ref_statement = Statement { | |
878 | source_info: statement.source_info, | |
879 | kind: StatementKind::Assign(Box::new(( | |
880 | Place::from(promoted_ref), | |
881 | Rvalue::Use(promoted_operand(ref_ty, span)), | |
882 | ))), | |
883 | }; | |
884 | self.extra_statements.push((loc, promoted_ref_statement)); | |
885 | ||
886 | Rvalue::Ref( | |
887 | tcx.lifetimes.re_erased, | |
888 | *borrow_kind, | |
889 | Place { | |
890 | local: mem::replace(&mut place.local, promoted_ref), | |
891 | projection: List::empty(), | |
892 | }, | |
893 | ) | |
a7813a04 | 894 | }; |
94b46f34 XL |
895 | |
896 | assert_eq!(self.new_block(), START_BLOCK); | |
dfeec247 XL |
897 | self.visit_rvalue( |
898 | &mut rvalue, | |
899 | Location { block: BasicBlock::new(0), statement_index: usize::MAX }, | |
900 | ); | |
c30ab7b3 | 901 | |
94b46f34 | 902 | let span = self.promoted.span; |
dfeec247 | 903 | self.assign(RETURN_PLACE, rvalue, span); |
3c0e092e | 904 | self.promoted |
a7813a04 XL |
905 | } |
906 | } | |
907 | ||
908 | /// Replaces all temporaries with their promoted counterparts. | |
909 | impl<'a, 'tcx> MutVisitor<'tcx> for Promoter<'a, 'tcx> { | |
e74abb32 XL |
910 | fn tcx(&self) -> TyCtxt<'tcx> { |
911 | self.tcx | |
912 | } | |
913 | ||
dfeec247 | 914 | fn visit_local(&mut self, local: &mut Local, _: PlaceContext, _: Location) { |
e74abb32 | 915 | if self.is_temp_kind(*local) { |
ea8adc8c | 916 | *local = self.promote_temp(*local); |
a7813a04 | 917 | } |
a7813a04 XL |
918 | } |
919 | } | |
920 | ||
dc9dc135 | 921 | pub fn promote_candidates<'tcx>( |
f9f354fc | 922 | body: &mut Body<'tcx>, |
dc9dc135 XL |
923 | tcx: TyCtxt<'tcx>, |
924 | mut temps: IndexVec<Local, TempState>, | |
925 | candidates: Vec<Candidate>, | |
f9f354fc | 926 | ) -> IndexVec<Promoted, Body<'tcx>> { |
a7813a04 | 927 | // Visit candidates in reverse, in case they're nested. |
476ff2be | 928 | debug!("promote_candidates({:?})", candidates); |
94b46f34 | 929 | |
e1599b0c XL |
930 | let mut promotions = IndexVec::new(); |
931 | ||
dfeec247 | 932 | let mut extra_statements = vec![]; |
a7813a04 | 933 | for candidate in candidates.into_iter().rev() { |
3c0e092e XL |
934 | let Location { block, statement_index } = candidate.location; |
935 | if let StatementKind::Assign(box (place, _)) = &body[block].statements[statement_index].kind | |
936 | { | |
937 | if let Some(local) = place.as_local() { | |
938 | if temps[local] == TempState::PromotedOut { | |
939 | // Already promoted. | |
940 | continue; | |
a7813a04 | 941 | } |
a7813a04 | 942 | } |
94b46f34 XL |
943 | } |
944 | ||
dc9dc135 | 945 | // Declare return place local so that `mir::Body::new` doesn't complain. |
f9f354fc | 946 | let initial_locals = iter::once(LocalDecl::new(tcx.types.never, body.span)).collect(); |
dfeec247 | 947 | |
3c0e092e | 948 | let mut scope = body.source_scopes[body.source_info(candidate.location).scope].clone(); |
29967ef6 XL |
949 | scope.parent_scope = None; |
950 | ||
f2b60f7d | 951 | let mut promoted = Body::new( |
29967ef6 | 952 | body.source, // `promoted` gets filled in below |
dfeec247 | 953 | IndexVec::new(), |
29967ef6 | 954 | IndexVec::from_elem_n(scope, 1), |
dfeec247 XL |
955 | initial_locals, |
956 | IndexVec::new(), | |
957 | 0, | |
958 | vec![], | |
959 | body.span, | |
6a06907d | 960 | body.generator_kind(), |
5099ac24 | 961 | body.tainted_by_errors, |
dfeec247 | 962 | ); |
f2b60f7d | 963 | promoted.phase = MirPhase::Analysis(AnalysisPhase::Initial); |
c30ab7b3 | 964 | |
8faf50e0 | 965 | let promoter = Promoter { |
f9f354fc | 966 | promoted, |
94b46f34 | 967 | tcx, |
dc9dc135 | 968 | source: body, |
a7813a04 | 969 | temps: &mut temps, |
dfeec247 XL |
970 | extra_statements: &mut extra_statements, |
971 | keep_original: false, | |
a7813a04 | 972 | }; |
e1599b0c | 973 | |
3c0e092e XL |
974 | let mut promoted = promoter.promote_candidate(candidate, promotions.len()); |
975 | promoted.source.promoted = Some(promotions.next_index()); | |
976 | promotions.push(promoted); | |
a7813a04 XL |
977 | } |
978 | ||
dfeec247 XL |
979 | // Insert each of `extra_statements` before its indicated location, which |
980 | // has to be done in reverse location order, to not invalidate the rest. | |
981 | extra_statements.sort_by_key(|&(loc, _)| cmp::Reverse(loc)); | |
982 | for (loc, statement) in extra_statements { | |
983 | body[loc.block].statements.insert(loc.statement_index, statement); | |
984 | } | |
985 | ||
a7813a04 | 986 | // Eliminate assignments to, and drops of promoted temps. |
c30ab7b3 | 987 | let promoted = |index: Local| temps[index] == TempState::PromotedOut; |
dc9dc135 | 988 | for block in body.basic_blocks_mut() { |
dfeec247 XL |
989 | block.statements.retain(|statement| match &statement.kind { |
990 | StatementKind::Assign(box (place, _)) => { | |
991 | if let Some(index) = place.as_local() { | |
992 | !promoted(index) | |
993 | } else { | |
994 | true | |
a7813a04 | 995 | } |
a7813a04 | 996 | } |
dfeec247 XL |
997 | StatementKind::StorageLive(index) | StatementKind::StorageDead(index) => { |
998 | !promoted(*index) | |
999 | } | |
1000 | _ => true, | |
a7813a04 XL |
1001 | }); |
1002 | let terminator = block.terminator_mut(); | |
f035d41b | 1003 | if let TerminatorKind::Drop { place, target, .. } = &terminator.kind { |
ba9703b0 XL |
1004 | if let Some(index) = place.as_local() { |
1005 | if promoted(index) { | |
1006 | terminator.kind = TerminatorKind::Goto { target: *target }; | |
a7813a04 XL |
1007 | } |
1008 | } | |
a7813a04 XL |
1009 | } |
1010 | } | |
e1599b0c XL |
1011 | |
1012 | promotions | |
a7813a04 | 1013 | } |
6a06907d XL |
1014 | |
1015 | /// This function returns `true` if the function being called in the array | |
1016 | /// repeat expression is a `const` function. | |
c295e0f8 | 1017 | pub fn is_const_fn_in_array_repeat_expression<'tcx>( |
6a06907d XL |
1018 | ccx: &ConstCx<'_, 'tcx>, |
1019 | place: &Place<'tcx>, | |
1020 | body: &Body<'tcx>, | |
1021 | ) -> bool { | |
1022 | match place.as_local() { | |
1023 | // rule out cases such as: `let my_var = some_fn(); [my_var; N]` | |
1024 | Some(local) if body.local_decls[local].is_user_variable() => return false, | |
1025 | None => return false, | |
1026 | _ => {} | |
1027 | } | |
1028 | ||
f2b60f7d | 1029 | for block in body.basic_blocks.iter() { |
6a06907d XL |
1030 | if let Some(Terminator { kind: TerminatorKind::Call { func, destination, .. }, .. }) = |
1031 | &block.terminator | |
1032 | { | |
1033 | if let Operand::Constant(box Constant { literal, .. }) = func { | |
1034 | if let ty::FnDef(def_id, _) = *literal.ty().kind() { | |
923072b8 FG |
1035 | if destination == place { |
1036 | if ccx.tcx.is_const_fn(def_id) { | |
1037 | return true; | |
6a06907d XL |
1038 | } |
1039 | } | |
1040 | } | |
1041 | } | |
1042 | } | |
1043 | } | |
1044 | ||
1045 | false | |
1046 | } |