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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; |
ba9703b0 XL |
17 | use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor}; |
18 | use rustc_middle::mir::*; | |
add651ee | 19 | use rustc_middle::ty::GenericArgs; |
fe692bf9 | 20 | use rustc_middle::ty::{self, List, Ty, TyCtxt, TypeVisitableExt}; |
fc512014 | 21 | use rustc_span::Span; |
a7813a04 | 22 | |
49aad941 | 23 | use rustc_index::{Idx, IndexSlice, IndexVec}; |
a7813a04 | 24 | |
60c5eb7d | 25 | use std::cell::Cell; |
ba9703b0 | 26 | use std::{cmp, iter, mem}; |
a7813a04 | 27 | |
3c0e092e | 28 | use crate::transform::check_consts::{qualifs, ConstCx}; |
e74abb32 | 29 | |
60c5eb7d XL |
30 | /// A `MirPass` for promotion. |
31 | /// | |
17df50a5 XL |
32 | /// Promotion is the extraction of promotable temps into separate MIR bodies so they can have |
33 | /// `'static` lifetime. | |
60c5eb7d XL |
34 | /// |
35 | /// After this pass is run, `promoted_fragments` will hold the MIR body corresponding to each | |
dfeec247 | 36 | /// newly created `Constant`. |
60c5eb7d XL |
37 | #[derive(Default)] |
38 | pub struct PromoteTemps<'tcx> { | |
f9f354fc | 39 | pub promoted_fragments: Cell<IndexVec<Promoted, Body<'tcx>>>, |
60c5eb7d XL |
40 | } |
41 | ||
42 | impl<'tcx> MirPass<'tcx> for PromoteTemps<'tcx> { | |
29967ef6 | 43 | fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { |
60c5eb7d XL |
44 | // There's not really any point in promoting errorful MIR. |
45 | // | |
46 | // This does not include MIR that failed const-checking, which we still try to promote. | |
487cf647 FG |
47 | if let Err(_) = body.return_ty().error_reported() { |
48 | debug!("PromoteTemps: MIR had errors"); | |
60c5eb7d XL |
49 | return; |
50 | } | |
29967ef6 | 51 | if body.source.promoted.is_some() { |
60c5eb7d XL |
52 | return; |
53 | } | |
54 | ||
29967ef6 | 55 | let ccx = ConstCx::new(tcx, body); |
fe692bf9 | 56 | let (mut temps, all_candidates) = collect_temps_and_candidates(&ccx); |
60c5eb7d | 57 | |
04454e1e | 58 | let promotable_candidates = validate_candidates(&ccx, &mut temps, &all_candidates); |
60c5eb7d | 59 | |
29967ef6 | 60 | let promoted = promote_candidates(body, tcx, temps, promotable_candidates); |
60c5eb7d XL |
61 | self.promoted_fragments.set(promoted); |
62 | } | |
63 | } | |
64 | ||
a7813a04 XL |
65 | /// State of a temporary during collection and promotion. |
66 | #[derive(Copy, Clone, PartialEq, Eq, Debug)] | |
67 | pub enum TempState { | |
68 | /// No references to this temp. | |
69 | Undefined, | |
70 | /// One direct assignment and any number of direct uses. | |
71 | /// A borrow of this temp is promotable if the assigned | |
72 | /// value is qualified as constant. | |
04454e1e | 73 | Defined { location: Location, uses: usize, valid: Result<(), ()> }, |
a7813a04 XL |
74 | /// Any other combination of assignments/uses. |
75 | Unpromotable, | |
76 | /// This temp was part of an rvalue which got extracted | |
77 | /// during promotion and needs cleanup. | |
dfeec247 | 78 | PromotedOut, |
a7813a04 XL |
79 | } |
80 | ||
81 | impl TempState { | |
82 | pub fn is_promotable(&self) -> bool { | |
13cf67c4 | 83 | debug!("is_promotable: self={:?}", self); |
5869c6ff | 84 | matches!(self, TempState::Defined { .. }) |
a7813a04 XL |
85 | } |
86 | } | |
87 | ||
88 | /// A "root candidate" for promotion, which will become the | |
89 | /// returned value in a promoted MIR, unless it's a subset | |
90 | /// of a larger candidate. | |
e74abb32 | 91 | #[derive(Copy, Clone, PartialEq, Eq, Debug)] |
3c0e092e XL |
92 | pub struct Candidate { |
93 | location: Location, | |
e74abb32 XL |
94 | } |
95 | ||
e74abb32 | 96 | struct Collector<'a, 'tcx> { |
f9f354fc | 97 | ccx: &'a ConstCx<'a, 'tcx>, |
c30ab7b3 | 98 | temps: IndexVec<Local, TempState>, |
e74abb32 | 99 | candidates: Vec<Candidate>, |
a7813a04 XL |
100 | } |
101 | ||
e74abb32 | 102 | impl<'tcx> Visitor<'tcx> for Collector<'_, 'tcx> { |
064997fb | 103 | fn visit_local(&mut self, index: Local, context: PlaceContext, location: Location) { |
13cf67c4 | 104 | debug!("visit_local: index={:?} context={:?} location={:?}", index, context, location); |
48663c56 | 105 | // We're only interested in temporaries and the return place |
f9f354fc | 106 | match self.ccx.body.local_kind(index) { |
353b0b11 FG |
107 | LocalKind::Arg => return, |
108 | LocalKind::Temp if self.ccx.body.local_decls[index].is_user_variable() => return, | |
109 | LocalKind::ReturnPointer | LocalKind::Temp => {} | |
ea8adc8c | 110 | } |
c30ab7b3 | 111 | |
ea8adc8c XL |
112 | // Ignore drops, if the temp gets promoted, |
113 | // then it's constant and thus drop is noop. | |
60c5eb7d | 114 | // Non-uses are also irrelevant. |
13cf67c4 XL |
115 | if context.is_drop() || !context.is_use() { |
116 | debug!( | |
117 | "visit_local: context.is_drop={:?} context.is_use={:?}", | |
dfeec247 XL |
118 | context.is_drop(), |
119 | context.is_use(), | |
13cf67c4 | 120 | ); |
ea8adc8c XL |
121 | return; |
122 | } | |
a7813a04 | 123 | |
ea8adc8c | 124 | let temp = &mut self.temps[index]; |
13cf67c4 | 125 | debug!("visit_local: temp={:?}", temp); |
ea8adc8c XL |
126 | if *temp == TempState::Undefined { |
127 | match context { | |
dfeec247 XL |
128 | PlaceContext::MutatingUse(MutatingUseContext::Store) |
129 | | PlaceContext::MutatingUse(MutatingUseContext::Call) => { | |
04454e1e | 130 | *temp = TempState::Defined { location, uses: 0, valid: Err(()) }; |
32a655c1 | 131 | return; |
a7813a04 | 132 | } |
ea8adc8c | 133 | _ => { /* mark as unpromotable below */ } |
a7813a04 | 134 | } |
9c376795 | 135 | } else if let TempState::Defined { uses, .. } = temp { |
ea8adc8c | 136 | // We always allow borrows, even mutable ones, as we need |
0731742a | 137 | // to promote mutable borrows of some ZSTs e.g., `&mut []`. |
dfeec247 XL |
138 | let allowed_use = match context { |
139 | PlaceContext::MutatingUse(MutatingUseContext::Borrow) | |
140 | | PlaceContext::NonMutatingUse(_) => true, | |
141 | PlaceContext::MutatingUse(_) | PlaceContext::NonUse(_) => false, | |
142 | }; | |
13cf67c4 | 143 | debug!("visit_local: allowed_use={:?}", allowed_use); |
ea8adc8c XL |
144 | if allowed_use { |
145 | *uses += 1; | |
146 | return; | |
147 | } | |
148 | /* mark as unpromotable below */ | |
a7813a04 | 149 | } |
ea8adc8c | 150 | *temp = TempState::Unpromotable; |
a7813a04 XL |
151 | } |
152 | ||
e74abb32 XL |
153 | fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) { |
154 | self.super_rvalue(rvalue, location); | |
155 | ||
156 | match *rvalue { | |
157 | Rvalue::Ref(..) => { | |
3c0e092e | 158 | self.candidates.push(Candidate { location }); |
e74abb32 | 159 | } |
e74abb32 XL |
160 | _ => {} |
161 | } | |
162 | } | |
a7813a04 XL |
163 | } |
164 | ||
a2a8927a XL |
165 | pub fn collect_temps_and_candidates<'tcx>( |
166 | ccx: &ConstCx<'_, 'tcx>, | |
e74abb32 XL |
167 | ) -> (IndexVec<Local, TempState>, Vec<Candidate>) { |
168 | let mut collector = Collector { | |
f9f354fc | 169 | temps: IndexVec::from_elem(TempState::Undefined, &ccx.body.local_decls), |
e74abb32 | 170 | candidates: vec![], |
f9f354fc | 171 | ccx, |
a7813a04 | 172 | }; |
fe692bf9 | 173 | for (bb, data) in traversal::reverse_postorder(ccx.body) { |
a7813a04 XL |
174 | collector.visit_basic_block_data(bb, data); |
175 | } | |
e74abb32 XL |
176 | (collector.temps, collector.candidates) |
177 | } | |
178 | ||
179 | /// Checks whether locals that appear in a promotion context (`Candidate`) are actually promotable. | |
180 | /// | |
181 | /// This wraps an `Item`, and has access to all fields of that `Item` via `Deref` coercion. | |
182 | struct Validator<'a, 'tcx> { | |
f9f354fc | 183 | ccx: &'a ConstCx<'a, 'tcx>, |
353b0b11 | 184 | temps: &'a mut IndexSlice<Local, TempState>, |
e74abb32 XL |
185 | } |
186 | ||
a2a8927a | 187 | impl<'a, 'tcx> std::ops::Deref for Validator<'a, 'tcx> { |
f9f354fc | 188 | type Target = ConstCx<'a, 'tcx>; |
e74abb32 XL |
189 | |
190 | fn deref(&self) -> &Self::Target { | |
f9f354fc | 191 | &self.ccx |
e74abb32 XL |
192 | } |
193 | } | |
194 | ||
195 | struct Unpromotable; | |
196 | ||
197 | impl<'tcx> Validator<'_, 'tcx> { | |
04454e1e | 198 | fn validate_candidate(&mut self, candidate: Candidate) -> Result<(), Unpromotable> { |
3c0e092e XL |
199 | let loc = candidate.location; |
200 | let statement = &self.body[loc.block].statements[loc.statement_index]; | |
201 | match &statement.kind { | |
202 | StatementKind::Assign(box (_, Rvalue::Ref(_, kind, place))) => { | |
203 | // We can only promote interior borrows of promotable temps (non-temps | |
204 | // don't get promoted anyway). | |
205 | self.validate_local(place.local)?; | |
206 | ||
207 | // The reference operation itself must be promotable. | |
208 | // (Needs to come after `validate_local` to avoid ICEs.) | |
209 | self.validate_ref(*kind, place)?; | |
e74abb32 | 210 | |
3c0e092e XL |
211 | // We do not check all the projections (they do not get promoted anyway), |
212 | // but we do stay away from promoting anything involving a dereference. | |
213 | if place.projection.contains(&ProjectionElem::Deref) { | |
214 | return Err(Unpromotable); | |
215 | } | |
e74abb32 | 216 | |
3c0e092e | 217 | Ok(()) |
e74abb32 | 218 | } |
3c0e092e | 219 | _ => bug!(), |
e74abb32 XL |
220 | } |
221 | } | |
222 | ||
223 | // FIXME(eddyb) maybe cache this? | |
04454e1e | 224 | fn qualif_local<Q: qualifs::Qualif>(&mut self, local: Local) -> bool { |
e74abb32 XL |
225 | if let TempState::Defined { location: loc, .. } = self.temps[local] { |
226 | let num_stmts = self.body[loc.block].statements.len(); | |
227 | ||
228 | if loc.statement_index < num_stmts { | |
229 | let statement = &self.body[loc.block].statements[loc.statement_index]; | |
230 | match &statement.kind { | |
ba9703b0 | 231 | StatementKind::Assign(box (_, rhs)) => qualifs::in_rvalue::<Q, _>( |
f9f354fc | 232 | &self.ccx, |
ba9703b0 XL |
233 | &mut |l| self.qualif_local::<Q>(l), |
234 | rhs, | |
235 | ), | |
e74abb32 | 236 | _ => { |
dfeec247 XL |
237 | span_bug!( |
238 | statement.source_info.span, | |
239 | "{:?} is not an assignment", | |
240 | statement | |
241 | ); | |
e74abb32 XL |
242 | } |
243 | } | |
244 | } else { | |
245 | let terminator = self.body[loc.block].terminator(); | |
246 | match &terminator.kind { | |
ba9703b0 | 247 | TerminatorKind::Call { .. } => { |
e74abb32 | 248 | let return_ty = self.body.local_decls[local].ty; |
f9f354fc | 249 | Q::in_any_value_of_ty(&self.ccx, return_ty) |
e74abb32 XL |
250 | } |
251 | kind => { | |
252 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); | |
253 | } | |
254 | } | |
255 | } | |
256 | } else { | |
9c376795 | 257 | false |
e74abb32 XL |
258 | } |
259 | } | |
260 | ||
04454e1e FG |
261 | fn validate_local(&mut self, local: Local) -> Result<(), Unpromotable> { |
262 | if let TempState::Defined { location: loc, uses, valid } = self.temps[local] { | |
9c376795 FG |
263 | // We cannot promote things that need dropping, since the promoted value |
264 | // would not get dropped. | |
265 | if self.qualif_local::<qualifs::NeedsDrop>(local) { | |
266 | return Err(Unpromotable); | |
267 | } | |
04454e1e FG |
268 | valid.or_else(|_| { |
269 | let ok = { | |
270 | let block = &self.body[loc.block]; | |
271 | let num_stmts = block.statements.len(); | |
272 | ||
273 | if loc.statement_index < num_stmts { | |
274 | let statement = &block.statements[loc.statement_index]; | |
275 | match &statement.kind { | |
276 | StatementKind::Assign(box (_, rhs)) => self.validate_rvalue(rhs), | |
277 | _ => { | |
278 | span_bug!( | |
279 | statement.source_info.span, | |
280 | "{:?} is not an assignment", | |
281 | statement | |
282 | ); | |
283 | } | |
284 | } | |
285 | } else { | |
286 | let terminator = block.terminator(); | |
287 | match &terminator.kind { | |
288 | TerminatorKind::Call { func, args, .. } => { | |
289 | self.validate_call(func, args) | |
290 | } | |
291 | TerminatorKind::Yield { .. } => Err(Unpromotable), | |
292 | kind => { | |
293 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); | |
294 | } | |
295 | } | |
e74abb32 | 296 | } |
04454e1e FG |
297 | }; |
298 | self.temps[local] = match ok { | |
299 | Ok(()) => TempState::Defined { location: loc, uses, valid: Ok(()) }, | |
300 | Err(_) => TempState::Unpromotable, | |
301 | }; | |
302 | ok | |
303 | }) | |
e74abb32 XL |
304 | } else { |
305 | Err(Unpromotable) | |
306 | } | |
307 | } | |
308 | ||
04454e1e | 309 | fn validate_place(&mut self, place: PlaceRef<'tcx>) -> Result<(), Unpromotable> { |
5869c6ff XL |
310 | match place.last_projection() { |
311 | None => self.validate_local(place.local), | |
312 | Some((place_base, elem)) => { | |
1b1a35ee | 313 | // Validate topmost projection, then recurse. |
5869c6ff | 314 | match elem { |
3dfed10e | 315 | ProjectionElem::Deref => { |
1b1a35ee | 316 | let mut promotable = false; |
487cf647 FG |
317 | // When a static is used by-value, that gets desugared to `*STATIC_ADDR`, |
318 | // and we need to be able to promote this. So check if this deref matches | |
319 | // that specific pattern. | |
320 | ||
5869c6ff XL |
321 | // We need to make sure this is a `Deref` of a local with no further projections. |
322 | // Discussion can be found at | |
323 | // https://github.com/rust-lang/rust/pull/74945#discussion_r463063247 | |
324 | if let Some(local) = place_base.as_local() { | |
5869c6ff XL |
325 | if let TempState::Defined { location, .. } = self.temps[local] { |
326 | let def_stmt = self.body[location.block] | |
327 | .statements | |
328 | .get(location.statement_index); | |
329 | if let Some(Statement { | |
330 | kind: | |
331 | StatementKind::Assign(box ( | |
332 | _, | |
333 | Rvalue::Use(Operand::Constant(c)), | |
334 | )), | |
335 | .. | |
336 | }) = def_stmt | |
337 | { | |
338 | if let Some(did) = c.check_static_ptr(self.tcx) { | |
339 | // Evaluating a promoted may not read statics except if it got | |
340 | // promoted from a static (this is a CTFE check). So we | |
341 | // can only promote static accesses inside statics. | |
342 | if let Some(hir::ConstContext::Static(..)) = self.const_kind | |
3dfed10e | 343 | { |
5869c6ff XL |
344 | if !self.tcx.is_thread_local_static(did) { |
345 | promotable = true; | |
346 | } | |
3dfed10e XL |
347 | } |
348 | } | |
349 | } | |
350 | } | |
351 | } | |
1b1a35ee | 352 | if !promotable { |
3dfed10e XL |
353 | return Err(Unpromotable); |
354 | } | |
355 | } | |
2b03887a | 356 | ProjectionElem::OpaqueCast(..) | ProjectionElem::Downcast(..) => { |
dfeec247 XL |
357 | return Err(Unpromotable); |
358 | } | |
e74abb32 | 359 | |
781aab86 FG |
360 | ProjectionElem::ConstantIndex { .. } |
361 | | ProjectionElem::Subtype(_) | |
362 | | 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. | |
9ffffee4 FG |
367 | let val = if let TempState::Defined { location: loc, .. } = |
368 | self.temps[local] | |
369 | { | |
370 | let block = &self.body[loc.block]; | |
371 | if loc.statement_index < block.statements.len() { | |
372 | let statement = &block.statements[loc.statement_index]; | |
373 | match &statement.kind { | |
374 | StatementKind::Assign(box ( | |
375 | _, | |
376 | Rvalue::Use(Operand::Constant(c)), | |
781aab86 | 377 | )) => c.const_.try_eval_target_usize(self.tcx, self.param_env), |
9ffffee4 | 378 | _ => None, |
5869c6ff XL |
379 | } |
380 | } else { | |
381 | None | |
9ffffee4 FG |
382 | } |
383 | } else { | |
384 | None | |
385 | }; | |
17df50a5 XL |
386 | if let Some(idx) = val { |
387 | // Determine the type of the thing we are indexing. | |
388 | let ty = place_base.ty(self.body, self.tcx).ty; | |
389 | match ty.kind() { | |
390 | ty::Array(_, len) => { | |
391 | // It's an array; determine its length. | |
9ffffee4 FG |
392 | if let Some(len) = |
393 | len.try_eval_target_usize(self.tcx, self.param_env) | |
17df50a5 XL |
394 | { |
395 | // If the index is in-bounds, go ahead. | |
396 | if idx < len { | |
397 | promotable = true; | |
5869c6ff XL |
398 | } |
399 | } | |
5869c6ff | 400 | } |
17df50a5 | 401 | _ => {} |
5869c6ff XL |
402 | } |
403 | } | |
17df50a5 XL |
404 | if !promotable { |
405 | return Err(Unpromotable); | |
406 | } | |
407 | ||
e74abb32 XL |
408 | self.validate_local(local)?; |
409 | } | |
410 | ||
411 | ProjectionElem::Field(..) => { | |
5869c6ff | 412 | let base_ty = place_base.ty(self.body, self.tcx).ty; |
17df50a5 | 413 | if base_ty.is_union() { |
29967ef6 | 414 | // No promotion of union field accesses. |
17df50a5 | 415 | return Err(Unpromotable); |
e74abb32 XL |
416 | } |
417 | } | |
418 | } | |
419 | ||
5869c6ff | 420 | self.validate_place(place_base) |
e74abb32 XL |
421 | } |
422 | } | |
423 | } | |
424 | ||
04454e1e | 425 | fn validate_operand(&mut self, operand: &Operand<'tcx>) -> Result<(), Unpromotable> { |
e74abb32 | 426 | match operand { |
dfeec247 | 427 | Operand::Copy(place) | Operand::Move(place) => self.validate_place(place.as_ref()), |
e74abb32 | 428 | |
60c5eb7d XL |
429 | // The qualifs for a constant (e.g. `HasMutInterior`) are checked in |
430 | // `validate_rvalue` upon access. | |
431 | Operand::Constant(c) => { | |
432 | if let Some(def_id) = c.check_static_ptr(self.tcx) { | |
433 | // Only allow statics (not consts) to refer to other statics. | |
434 | // FIXME(eddyb) does this matter at all for promotion? | |
1b1a35ee XL |
435 | // FIXME(RalfJung) it makes little sense to not promote this in `fn`/`const fn`, |
436 | // and in `const` this cannot occur anyway. The only concern is that we might | |
437 | // promote even `let x = &STATIC` which would be useless, but this applies to | |
438 | // promotion inside statics as well. | |
f9f354fc | 439 | let is_static = matches!(self.const_kind, Some(hir::ConstContext::Static(_))); |
60c5eb7d XL |
440 | if !is_static { |
441 | return Err(Unpromotable); | |
442 | } | |
443 | ||
f9f354fc | 444 | let is_thread_local = self.tcx.is_thread_local_static(def_id); |
60c5eb7d XL |
445 | if is_thread_local { |
446 | return Err(Unpromotable); | |
e74abb32 XL |
447 | } |
448 | } | |
449 | ||
450 | Ok(()) | |
dfeec247 | 451 | } |
e74abb32 XL |
452 | } |
453 | } | |
454 | ||
04454e1e | 455 | fn validate_ref(&mut self, kind: BorrowKind, place: &Place<'tcx>) -> Result<(), Unpromotable> { |
5869c6ff XL |
456 | match kind { |
457 | // Reject these borrow types just to be safe. | |
458 | // FIXME(RalfJung): could we allow them? Should we? No point in it until we have a usecase. | |
781aab86 | 459 | BorrowKind::Fake | BorrowKind::Mut { kind: MutBorrowKind::ClosureCapture } => { |
fe692bf9 FG |
460 | return Err(Unpromotable); |
461 | } | |
5869c6ff XL |
462 | |
463 | BorrowKind::Shared => { | |
464 | let has_mut_interior = self.qualif_local::<qualifs::HasMutInterior>(place.local); | |
465 | if has_mut_interior { | |
1b1a35ee | 466 | return Err(Unpromotable); |
e74abb32 XL |
467 | } |
468 | } | |
469 | ||
fe692bf9 FG |
470 | // FIXME: consider changing this to only promote &mut [] for default borrows, |
471 | // also forbidding two phase borrows | |
472 | BorrowKind::Mut { kind: MutBorrowKind::Default | MutBorrowKind::TwoPhaseBorrow } => { | |
5869c6ff XL |
473 | let ty = place.ty(self.body, self.tcx).ty; |
474 | ||
475 | // In theory, any zero-sized value could be borrowed | |
476 | // mutably without consequences. However, only &mut [] | |
477 | // is allowed right now. | |
478 | if let ty::Array(_, len) = ty.kind() { | |
9ffffee4 | 479 | match len.try_eval_target_usize(self.tcx, self.param_env) { |
5869c6ff XL |
480 | Some(0) => {} |
481 | _ => return Err(Unpromotable), | |
482 | } | |
483 | } else { | |
e74abb32 XL |
484 | return Err(Unpromotable); |
485 | } | |
486 | } | |
e74abb32 XL |
487 | } |
488 | ||
5869c6ff XL |
489 | Ok(()) |
490 | } | |
491 | ||
04454e1e | 492 | fn validate_rvalue(&mut self, rvalue: &Rvalue<'tcx>) -> Result<(), Unpromotable> { |
e74abb32 | 493 | match rvalue { |
5869c6ff XL |
494 | Rvalue::Use(operand) | Rvalue::Repeat(operand, _) => { |
495 | self.validate_operand(operand)?; | |
496 | } | |
064997fb FG |
497 | Rvalue::CopyForDeref(place) => { |
498 | let op = &Operand::Copy(*place); | |
499 | self.validate_operand(op)? | |
500 | } | |
5869c6ff XL |
501 | |
502 | Rvalue::Discriminant(place) | Rvalue::Len(place) => { | |
503 | self.validate_place(place.as_ref())? | |
504 | } | |
505 | ||
506 | Rvalue::ThreadLocalRef(_) => return Err(Unpromotable), | |
507 | ||
923072b8 FG |
508 | // ptr-to-int casts are not possible in consts and thus not promotable |
509 | Rvalue::Cast(CastKind::PointerExposeAddress, _, _) => return Err(Unpromotable), | |
5869c6ff | 510 | |
923072b8 FG |
511 | // all other casts including int-to-ptr casts are fine, they just use the integer value |
512 | // at pointer type. | |
513 | Rvalue::Cast(_, operand, _) => { | |
5869c6ff XL |
514 | self.validate_operand(operand)?; |
515 | } | |
516 | ||
517 | Rvalue::NullaryOp(op, _) => match op { | |
5869c6ff | 518 | NullOp::SizeOf => {} |
c295e0f8 | 519 | NullOp::AlignOf => {} |
49aad941 | 520 | NullOp::OffsetOf(_) => {} |
5869c6ff | 521 | }, |
f9f354fc | 522 | |
c295e0f8 XL |
523 | Rvalue::ShallowInitBox(_, _) => return Err(Unpromotable), |
524 | ||
5869c6ff XL |
525 | Rvalue::UnaryOp(op, operand) => { |
526 | match op { | |
527 | // These operations can never fail. | |
528 | UnOp::Neg | UnOp::Not => {} | |
529 | } | |
e74abb32 | 530 | |
5869c6ff XL |
531 | self.validate_operand(operand)?; |
532 | } | |
533 | ||
6a06907d | 534 | Rvalue::BinaryOp(op, box (lhs, rhs)) | Rvalue::CheckedBinaryOp(op, box (lhs, rhs)) => { |
5869c6ff XL |
535 | let op = *op; |
536 | let lhs_ty = lhs.ty(self.body, self.tcx); | |
537 | ||
538 | if let ty::RawPtr(_) | ty::FnPtr(..) = lhs_ty.kind() { | |
539 | // Raw and fn pointer operations are not allowed inside consts and thus not promotable. | |
540 | assert!(matches!( | |
541 | op, | |
542 | BinOp::Eq | |
543 | | BinOp::Ne | |
544 | | BinOp::Le | |
545 | | BinOp::Lt | |
546 | | BinOp::Ge | |
547 | | BinOp::Gt | |
548 | | BinOp::Offset | |
549 | )); | |
550 | return Err(Unpromotable); | |
551 | } | |
e74abb32 | 552 | |
5869c6ff XL |
553 | match op { |
554 | BinOp::Div | BinOp::Rem => { | |
17df50a5 | 555 | if lhs_ty.is_integral() { |
5869c6ff XL |
556 | // Integer division: the RHS must be a non-zero const. |
557 | let const_val = match rhs { | |
558 | Operand::Constant(c) => { | |
781aab86 | 559 | c.const_.try_eval_bits(self.tcx, self.param_env) |
5869c6ff XL |
560 | } |
561 | _ => None, | |
562 | }; | |
563 | match const_val { | |
564 | Some(x) if x != 0 => {} // okay | |
565 | _ => return Err(Unpromotable), // value not known or 0 -- not okay | |
566 | } | |
567 | } | |
568 | } | |
569 | // The remaining operations can never fail. | |
570 | BinOp::Eq | |
571 | | BinOp::Ne | |
572 | | BinOp::Le | |
573 | | BinOp::Lt | |
574 | | BinOp::Ge | |
575 | | BinOp::Gt | |
576 | | BinOp::Offset | |
577 | | BinOp::Add | |
fe692bf9 | 578 | | BinOp::AddUnchecked |
5869c6ff | 579 | | BinOp::Sub |
fe692bf9 | 580 | | BinOp::SubUnchecked |
5869c6ff | 581 | | BinOp::Mul |
fe692bf9 | 582 | | BinOp::MulUnchecked |
5869c6ff XL |
583 | | BinOp::BitXor |
584 | | BinOp::BitAnd | |
585 | | BinOp::BitOr | |
586 | | BinOp::Shl | |
fe692bf9 FG |
587 | | BinOp::ShlUnchecked |
588 | | BinOp::Shr | |
589 | | BinOp::ShrUnchecked => {} | |
5869c6ff | 590 | } |
e74abb32 | 591 | |
e74abb32 | 592 | self.validate_operand(lhs)?; |
5869c6ff | 593 | self.validate_operand(rhs)?; |
e74abb32 XL |
594 | } |
595 | ||
dfeec247 | 596 | Rvalue::AddressOf(_, place) => { |
1b1a35ee XL |
597 | // We accept `&raw *`, i.e., raw reborrows -- creating a raw pointer is |
598 | // no problem, only using it is. | |
5869c6ff XL |
599 | if let Some((place_base, ProjectionElem::Deref)) = place.as_ref().last_projection() |
600 | { | |
601 | let base_ty = place_base.ty(self.body, self.tcx).ty; | |
1b1a35ee | 602 | if let ty::Ref(..) = base_ty.kind() { |
5869c6ff | 603 | return self.validate_place(place_base); |
dfeec247 XL |
604 | } |
605 | } | |
5869c6ff | 606 | return Err(Unpromotable); |
dfeec247 XL |
607 | } |
608 | ||
e74abb32 | 609 | Rvalue::Ref(_, kind, place) => { |
e74abb32 | 610 | // Special-case reborrows to be more like a copy of the reference. |
5869c6ff XL |
611 | let mut place_simplified = place.as_ref(); |
612 | if let Some((place_base, ProjectionElem::Deref)) = | |
613 | place_simplified.last_projection() | |
614 | { | |
615 | let base_ty = place_base.ty(self.body, self.tcx).ty; | |
1b1a35ee | 616 | if let ty::Ref(..) = base_ty.kind() { |
5869c6ff | 617 | place_simplified = place_base; |
e74abb32 XL |
618 | } |
619 | } | |
620 | ||
5869c6ff | 621 | self.validate_place(place_simplified)?; |
e74abb32 | 622 | |
5869c6ff XL |
623 | // Check that the reference is fine (using the original place!). |
624 | // (Needs to come after `validate_place` to avoid ICEs.) | |
625 | self.validate_ref(*kind, place)?; | |
e74abb32 XL |
626 | } |
627 | ||
5869c6ff | 628 | Rvalue::Aggregate(_, operands) => { |
e74abb32 XL |
629 | for o in operands { |
630 | self.validate_operand(o)?; | |
631 | } | |
e74abb32 XL |
632 | } |
633 | } | |
5869c6ff XL |
634 | |
635 | Ok(()) | |
e74abb32 XL |
636 | } |
637 | ||
638 | fn validate_call( | |
04454e1e | 639 | &mut self, |
e74abb32 XL |
640 | callee: &Operand<'tcx>, |
641 | args: &[Operand<'tcx>], | |
642 | ) -> Result<(), Unpromotable> { | |
f9f354fc | 643 | let fn_ty = callee.ty(self.body, self.tcx); |
e74abb32 | 644 | |
17df50a5 | 645 | // Inside const/static items, we promote all (eligible) function calls. |
29967ef6 | 646 | // Everywhere else, we require `#[rustc_promotable]` on the callee. |
17df50a5 XL |
647 | let promote_all_const_fn = matches!( |
648 | self.const_kind, | |
781aab86 | 649 | Some(hir::ConstContext::Static(_) | hir::ConstContext::Const { inline: false }) |
17df50a5 | 650 | ); |
29967ef6 | 651 | if !promote_all_const_fn { |
1b1a35ee | 652 | if let ty::FnDef(def_id, _) = *fn_ty.kind() { |
e74abb32 XL |
653 | // Never promote runtime `const fn` calls of |
654 | // functions without `#[rustc_promotable]`. | |
655 | if !self.tcx.is_promotable_const_fn(def_id) { | |
656 | return Err(Unpromotable); | |
657 | } | |
658 | } | |
659 | } | |
660 | ||
1b1a35ee | 661 | let is_const_fn = match *fn_ty.kind() { |
3c0e092e | 662 | ty::FnDef(def_id, _) => self.tcx.is_const_fn_raw(def_id), |
e74abb32 XL |
663 | _ => false, |
664 | }; | |
665 | if !is_const_fn { | |
666 | return Err(Unpromotable); | |
667 | } | |
668 | ||
669 | self.validate_operand(callee)?; | |
670 | for arg in args { | |
671 | self.validate_operand(arg)?; | |
672 | } | |
673 | ||
674 | Ok(()) | |
675 | } | |
676 | } | |
677 | ||
678 | // FIXME(eddyb) remove the differences for promotability in `static`, `const`, `const fn`. | |
679 | pub fn validate_candidates( | |
f9f354fc | 680 | ccx: &ConstCx<'_, '_>, |
353b0b11 | 681 | temps: &mut IndexSlice<Local, TempState>, |
e74abb32 XL |
682 | candidates: &[Candidate], |
683 | ) -> Vec<Candidate> { | |
04454e1e | 684 | let mut validator = Validator { ccx, temps }; |
e74abb32 | 685 | |
dfeec247 XL |
686 | candidates |
687 | .iter() | |
688 | .copied() | |
17df50a5 | 689 | .filter(|&candidate| validator.validate_candidate(candidate).is_ok()) |
dfeec247 | 690 | .collect() |
a7813a04 XL |
691 | } |
692 | ||
dc9dc135 XL |
693 | struct Promoter<'a, 'tcx> { |
694 | tcx: TyCtxt<'tcx>, | |
f9f354fc XL |
695 | source: &'a mut Body<'tcx>, |
696 | promoted: Body<'tcx>, | |
c30ab7b3 | 697 | temps: &'a mut IndexVec<Local, TempState>, |
dfeec247 | 698 | extra_statements: &'a mut Vec<(Location, Statement<'tcx>)>, |
a7813a04 XL |
699 | |
700 | /// If true, all nested temps are also kept in the | |
701 | /// source MIR, not moved to the promoted MIR. | |
dc9dc135 | 702 | keep_original: bool, |
a7813a04 XL |
703 | } |
704 | ||
705 | impl<'a, 'tcx> Promoter<'a, 'tcx> { | |
706 | fn new_block(&mut self) -> BasicBlock { | |
3157f602 XL |
707 | let span = self.promoted.span; |
708 | self.promoted.basic_blocks_mut().push(BasicBlockData { | |
a7813a04 XL |
709 | statements: vec![], |
710 | terminator: Some(Terminator { | |
f9f354fc | 711 | source_info: SourceInfo::outermost(span), |
dfeec247 | 712 | kind: TerminatorKind::Return, |
a7813a04 | 713 | }), |
dfeec247 | 714 | is_cleanup: false, |
3157f602 | 715 | }) |
a7813a04 XL |
716 | } |
717 | ||
c30ab7b3 | 718 | fn assign(&mut self, dest: Local, rvalue: Rvalue<'tcx>, span: Span) { |
353b0b11 | 719 | let last = self.promoted.basic_blocks.last_index().unwrap(); |
3157f602 | 720 | let data = &mut self.promoted[last]; |
a7813a04 | 721 | data.statements.push(Statement { |
f9f354fc | 722 | source_info: SourceInfo::outermost(span), |
94222f64 | 723 | kind: StatementKind::Assign(Box::new((Place::from(dest), rvalue))), |
a7813a04 XL |
724 | }); |
725 | } | |
726 | ||
e74abb32 XL |
727 | fn is_temp_kind(&self, local: Local) -> bool { |
728 | self.source.local_kind(local) == LocalKind::Temp | |
729 | } | |
730 | ||
9fa01778 | 731 | /// Copies the initialization of this temp to the |
a7813a04 | 732 | /// promoted MIR, recursing through temps. |
c30ab7b3 | 733 | fn promote_temp(&mut self, temp: Local) -> Local { |
a7813a04 | 734 | let old_keep_original = self.keep_original; |
476ff2be | 735 | let loc = match self.temps[temp] { |
04454e1e | 736 | TempState::Defined { location, uses, .. } if uses > 0 => { |
a7813a04 XL |
737 | if uses > 1 { |
738 | self.keep_original = true; | |
739 | } | |
476ff2be | 740 | location |
a7813a04 | 741 | } |
dfeec247 XL |
742 | state => { |
743 | span_bug!(self.promoted.span, "{:?} not promotable: {:?}", temp, state); | |
a7813a04 XL |
744 | } |
745 | }; | |
746 | if !self.keep_original { | |
3157f602 | 747 | self.temps[temp] = TempState::PromotedOut; |
a7813a04 XL |
748 | } |
749 | ||
e74abb32 | 750 | let num_stmts = self.source[loc.block].statements.len(); |
f9f354fc | 751 | let new_temp = self.promoted.local_decls.push(LocalDecl::new( |
dfeec247 XL |
752 | self.source.local_decls[temp].ty, |
753 | self.source.local_decls[temp].source_info.span, | |
754 | )); | |
476ff2be | 755 | |
dfeec247 | 756 | debug!("promote({:?} @ {:?}/{:?}, {:?})", temp, loc, num_stmts, self.keep_original); |
a7813a04 XL |
757 | |
758 | // First, take the Rvalue or Call out of the source MIR, | |
759 | // or duplicate it, depending on keep_original. | |
e74abb32 | 760 | if loc.statement_index < num_stmts { |
e1599b0c | 761 | let (mut rvalue, source_info) = { |
476ff2be | 762 | let statement = &mut self.source[loc.block].statements[loc.statement_index]; |
9c376795 | 763 | let StatementKind::Assign(box (_, rhs)) = &mut statement.kind else { |
add651ee | 764 | span_bug!(statement.source_info.span, "{:?} is not an assignment", statement); |
476ff2be SL |
765 | }; |
766 | ||
dfeec247 XL |
767 | ( |
768 | if self.keep_original { | |
769 | rhs.clone() | |
770 | } else { | |
781aab86 | 771 | let unit = Rvalue::Use(Operand::Constant(Box::new(ConstOperand { |
ba9703b0 XL |
772 | span: statement.source_info.span, |
773 | user_ty: None, | |
781aab86 | 774 | const_: Const::zero_sized(self.tcx.types.unit), |
94222f64 | 775 | }))); |
dfeec247 XL |
776 | mem::replace(rhs, unit) |
777 | }, | |
778 | statement.source_info, | |
779 | ) | |
5bcae85e | 780 | }; |
476ff2be SL |
781 | |
782 | self.visit_rvalue(&mut rvalue, loc); | |
783 | self.assign(new_temp, rvalue, source_info.span); | |
a7813a04 | 784 | } else { |
476ff2be SL |
785 | let terminator = if self.keep_original { |
786 | self.source[loc.block].terminator().clone() | |
787 | } else { | |
788 | let terminator = self.source[loc.block].terminator_mut(); | |
9c376795 FG |
789 | let target = match &terminator.kind { |
790 | TerminatorKind::Call { target: Some(target), .. } => *target, | |
791 | kind => { | |
476ff2be SL |
792 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); |
793 | } | |
794 | }; | |
795 | Terminator { | |
796 | source_info: terminator.source_info, | |
dfeec247 | 797 | kind: mem::replace(&mut terminator.kind, TerminatorKind::Goto { target }), |
a7813a04 XL |
798 | } |
799 | }; | |
a7813a04 | 800 | |
476ff2be | 801 | match terminator.kind { |
fe692bf9 FG |
802 | TerminatorKind::Call { |
803 | mut func, mut args, call_source: desugar, fn_span, .. | |
804 | } => { | |
476ff2be SL |
805 | self.visit_operand(&mut func, loc); |
806 | for arg in &mut args { | |
807 | self.visit_operand(arg, loc); | |
808 | } | |
a7813a04 | 809 | |
353b0b11 | 810 | let last = self.promoted.basic_blocks.last_index().unwrap(); |
476ff2be | 811 | let new_target = self.new_block(); |
a7813a04 | 812 | |
476ff2be SL |
813 | *self.promoted[last].terminator_mut() = Terminator { |
814 | kind: TerminatorKind::Call { | |
3b2f2976 XL |
815 | func, |
816 | args, | |
353b0b11 | 817 | unwind: UnwindAction::Continue, |
923072b8 FG |
818 | destination: Place::from(new_temp), |
819 | target: Some(new_target), | |
fe692bf9 | 820 | call_source: desugar, |
f035d41b | 821 | fn_span, |
476ff2be | 822 | }, |
29967ef6 | 823 | source_info: SourceInfo::outermost(terminator.source_info.span), |
476ff2be SL |
824 | ..terminator |
825 | }; | |
a7813a04 | 826 | } |
9c376795 | 827 | kind => { |
476ff2be SL |
828 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); |
829 | } | |
830 | }; | |
831 | }; | |
a7813a04 | 832 | |
a7813a04 | 833 | self.keep_original = old_keep_original; |
3157f602 | 834 | new_temp |
a7813a04 XL |
835 | } |
836 | ||
3c0e092e | 837 | fn promote_candidate(mut self, candidate: Candidate, next_promoted_id: usize) -> Body<'tcx> { |
49aad941 | 838 | let def = self.source.source.def_id(); |
dfeec247 | 839 | let mut rvalue = { |
94b46f34 | 840 | let promoted = &mut self.promoted; |
e1599b0c XL |
841 | let promoted_id = Promoted::new(next_promoted_id); |
842 | let tcx = self.tcx; | |
dfeec247 | 843 | let mut promoted_operand = |ty, span| { |
94b46f34 | 844 | promoted.span = span; |
f9f354fc | 845 | promoted.local_decls[RETURN_PLACE] = LocalDecl::new(ty, span); |
add651ee FG |
846 | let args = tcx.erase_regions(GenericArgs::identity_for_item(tcx, def)); |
847 | let uneval = mir::UnevaluatedConst { def, args, promoted: Some(promoted_id) }; | |
dfeec247 | 848 | |
781aab86 | 849 | Operand::Constant(Box::new(ConstOperand { |
dfeec247 XL |
850 | span, |
851 | user_ty: None, | |
781aab86 | 852 | const_: Const::Unevaluated(uneval, ty), |
dfeec247 | 853 | })) |
94b46f34 | 854 | }; |
f2b60f7d | 855 | |
064997fb FG |
856 | let blocks = self.source.basic_blocks.as_mut(); |
857 | let local_decls = &mut self.source.local_decls; | |
3c0e092e XL |
858 | let loc = candidate.location; |
859 | let statement = &mut blocks[loc.block].statements[loc.statement_index]; | |
add651ee FG |
860 | let StatementKind::Assign(box (_, Rvalue::Ref(region, borrow_kind, place))) = |
861 | &mut statement.kind | |
862 | else { | |
9c376795 FG |
863 | bug!() |
864 | }; | |
3c0e092e | 865 | |
9c376795 FG |
866 | // Use the underlying local for this (necessarily interior) borrow. |
867 | let ty = local_decls[place.local].ty; | |
868 | let span = statement.source_info.span; | |
869 | ||
fe692bf9 FG |
870 | let ref_ty = Ty::new_ref( |
871 | tcx, | |
9c376795 FG |
872 | tcx.lifetimes.re_erased, |
873 | ty::TypeAndMut { ty, mutbl: borrow_kind.to_mutbl_lossy() }, | |
874 | ); | |
875 | ||
876 | *region = tcx.lifetimes.re_erased; | |
877 | ||
878 | let mut projection = vec![PlaceElem::Deref]; | |
879 | projection.extend(place.projection); | |
9ffffee4 | 880 | place.projection = tcx.mk_place_elems(&projection); |
9c376795 FG |
881 | |
882 | // Create a temp to hold the promoted reference. | |
883 | // This is because `*r` requires `r` to be a local, | |
884 | // otherwise we would use the `promoted` directly. | |
885 | let mut promoted_ref = LocalDecl::new(ref_ty, span); | |
886 | promoted_ref.source_info = statement.source_info; | |
887 | let promoted_ref = local_decls.push(promoted_ref); | |
888 | assert_eq!(self.temps.push(TempState::Unpromotable), promoted_ref); | |
889 | ||
890 | let promoted_ref_statement = Statement { | |
891 | source_info: statement.source_info, | |
892 | kind: StatementKind::Assign(Box::new(( | |
893 | Place::from(promoted_ref), | |
894 | Rvalue::Use(promoted_operand(ref_ty, span)), | |
895 | ))), | |
896 | }; | |
897 | self.extra_statements.push((loc, promoted_ref_statement)); | |
898 | ||
899 | Rvalue::Ref( | |
900 | tcx.lifetimes.re_erased, | |
901 | *borrow_kind, | |
902 | Place { | |
903 | local: mem::replace(&mut place.local, promoted_ref), | |
904 | projection: List::empty(), | |
905 | }, | |
906 | ) | |
a7813a04 | 907 | }; |
94b46f34 XL |
908 | |
909 | assert_eq!(self.new_block(), START_BLOCK); | |
dfeec247 XL |
910 | self.visit_rvalue( |
911 | &mut rvalue, | |
9ffffee4 | 912 | Location { block: START_BLOCK, statement_index: usize::MAX }, |
dfeec247 | 913 | ); |
c30ab7b3 | 914 | |
94b46f34 | 915 | let span = self.promoted.span; |
dfeec247 | 916 | self.assign(RETURN_PLACE, rvalue, span); |
3c0e092e | 917 | self.promoted |
a7813a04 XL |
918 | } |
919 | } | |
920 | ||
921 | /// Replaces all temporaries with their promoted counterparts. | |
922 | impl<'a, 'tcx> MutVisitor<'tcx> for Promoter<'a, 'tcx> { | |
e74abb32 XL |
923 | fn tcx(&self) -> TyCtxt<'tcx> { |
924 | self.tcx | |
925 | } | |
926 | ||
dfeec247 | 927 | fn visit_local(&mut self, local: &mut Local, _: PlaceContext, _: Location) { |
e74abb32 | 928 | if self.is_temp_kind(*local) { |
ea8adc8c | 929 | *local = self.promote_temp(*local); |
a7813a04 | 930 | } |
a7813a04 XL |
931 | } |
932 | } | |
933 | ||
dc9dc135 | 934 | pub fn promote_candidates<'tcx>( |
f9f354fc | 935 | body: &mut Body<'tcx>, |
dc9dc135 XL |
936 | tcx: TyCtxt<'tcx>, |
937 | mut temps: IndexVec<Local, TempState>, | |
938 | candidates: Vec<Candidate>, | |
f9f354fc | 939 | ) -> IndexVec<Promoted, Body<'tcx>> { |
a7813a04 | 940 | // Visit candidates in reverse, in case they're nested. |
476ff2be | 941 | debug!("promote_candidates({:?})", candidates); |
94b46f34 | 942 | |
e1599b0c XL |
943 | let mut promotions = IndexVec::new(); |
944 | ||
dfeec247 | 945 | let mut extra_statements = vec![]; |
a7813a04 | 946 | for candidate in candidates.into_iter().rev() { |
3c0e092e XL |
947 | let Location { block, statement_index } = candidate.location; |
948 | if let StatementKind::Assign(box (place, _)) = &body[block].statements[statement_index].kind | |
949 | { | |
950 | if let Some(local) = place.as_local() { | |
951 | if temps[local] == TempState::PromotedOut { | |
952 | // Already promoted. | |
953 | continue; | |
a7813a04 | 954 | } |
a7813a04 | 955 | } |
94b46f34 XL |
956 | } |
957 | ||
dc9dc135 | 958 | // Declare return place local so that `mir::Body::new` doesn't complain. |
f9f354fc | 959 | let initial_locals = iter::once(LocalDecl::new(tcx.types.never, body.span)).collect(); |
dfeec247 | 960 | |
3c0e092e | 961 | let mut scope = body.source_scopes[body.source_info(candidate.location).scope].clone(); |
29967ef6 XL |
962 | scope.parent_scope = None; |
963 | ||
f2b60f7d | 964 | let mut promoted = Body::new( |
29967ef6 | 965 | body.source, // `promoted` gets filled in below |
dfeec247 | 966 | IndexVec::new(), |
29967ef6 | 967 | IndexVec::from_elem_n(scope, 1), |
dfeec247 XL |
968 | initial_locals, |
969 | IndexVec::new(), | |
970 | 0, | |
971 | vec![], | |
972 | body.span, | |
6a06907d | 973 | body.generator_kind(), |
5099ac24 | 974 | body.tainted_by_errors, |
dfeec247 | 975 | ); |
f2b60f7d | 976 | promoted.phase = MirPhase::Analysis(AnalysisPhase::Initial); |
c30ab7b3 | 977 | |
8faf50e0 | 978 | let promoter = Promoter { |
f9f354fc | 979 | promoted, |
94b46f34 | 980 | tcx, |
dc9dc135 | 981 | source: body, |
a7813a04 | 982 | temps: &mut temps, |
dfeec247 XL |
983 | extra_statements: &mut extra_statements, |
984 | keep_original: false, | |
a7813a04 | 985 | }; |
e1599b0c | 986 | |
3c0e092e XL |
987 | let mut promoted = promoter.promote_candidate(candidate, promotions.len()); |
988 | promoted.source.promoted = Some(promotions.next_index()); | |
989 | promotions.push(promoted); | |
a7813a04 XL |
990 | } |
991 | ||
dfeec247 XL |
992 | // Insert each of `extra_statements` before its indicated location, which |
993 | // has to be done in reverse location order, to not invalidate the rest. | |
994 | extra_statements.sort_by_key(|&(loc, _)| cmp::Reverse(loc)); | |
995 | for (loc, statement) in extra_statements { | |
996 | body[loc.block].statements.insert(loc.statement_index, statement); | |
997 | } | |
998 | ||
a7813a04 | 999 | // Eliminate assignments to, and drops of promoted temps. |
c30ab7b3 | 1000 | let promoted = |index: Local| temps[index] == TempState::PromotedOut; |
dc9dc135 | 1001 | for block in body.basic_blocks_mut() { |
dfeec247 XL |
1002 | block.statements.retain(|statement| match &statement.kind { |
1003 | StatementKind::Assign(box (place, _)) => { | |
1004 | if let Some(index) = place.as_local() { | |
1005 | !promoted(index) | |
1006 | } else { | |
1007 | true | |
a7813a04 | 1008 | } |
a7813a04 | 1009 | } |
dfeec247 XL |
1010 | StatementKind::StorageLive(index) | StatementKind::StorageDead(index) => { |
1011 | !promoted(*index) | |
1012 | } | |
1013 | _ => true, | |
a7813a04 XL |
1014 | }); |
1015 | let terminator = block.terminator_mut(); | |
f035d41b | 1016 | if let TerminatorKind::Drop { place, target, .. } = &terminator.kind { |
ba9703b0 XL |
1017 | if let Some(index) = place.as_local() { |
1018 | if promoted(index) { | |
1019 | terminator.kind = TerminatorKind::Goto { target: *target }; | |
a7813a04 XL |
1020 | } |
1021 | } | |
a7813a04 XL |
1022 | } |
1023 | } | |
e1599b0c XL |
1024 | |
1025 | promotions | |
a7813a04 | 1026 | } |
6a06907d XL |
1027 | |
1028 | /// This function returns `true` if the function being called in the array | |
1029 | /// repeat expression is a `const` function. | |
c295e0f8 | 1030 | pub fn is_const_fn_in_array_repeat_expression<'tcx>( |
6a06907d XL |
1031 | ccx: &ConstCx<'_, 'tcx>, |
1032 | place: &Place<'tcx>, | |
1033 | body: &Body<'tcx>, | |
1034 | ) -> bool { | |
1035 | match place.as_local() { | |
1036 | // rule out cases such as: `let my_var = some_fn(); [my_var; N]` | |
1037 | Some(local) if body.local_decls[local].is_user_variable() => return false, | |
1038 | None => return false, | |
1039 | _ => {} | |
1040 | } | |
1041 | ||
f2b60f7d | 1042 | for block in body.basic_blocks.iter() { |
6a06907d XL |
1043 | if let Some(Terminator { kind: TerminatorKind::Call { func, destination, .. }, .. }) = |
1044 | &block.terminator | |
1045 | { | |
781aab86 FG |
1046 | if let Operand::Constant(box ConstOperand { const_, .. }) = func { |
1047 | if let ty::FnDef(def_id, _) = *const_.ty().kind() { | |
923072b8 FG |
1048 | if destination == place { |
1049 | if ccx.tcx.is_const_fn(def_id) { | |
1050 | return true; | |
6a06907d XL |
1051 | } |
1052 | } | |
1053 | } | |
1054 | } | |
1055 | } | |
1056 | } | |
1057 | ||
1058 | false | |
1059 | } |