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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; |
ba9703b0 XL |
16 | use rustc_middle::mir::traversal::ReversePostorder; |
17 | use rustc_middle::mir::visit::{MutVisitor, MutatingUseContext, PlaceContext, Visitor}; | |
18 | use rustc_middle::mir::*; | |
19 | use rustc_middle::ty::cast::CastTy; | |
20 | use rustc_middle::ty::subst::InternalSubsts; | |
21 | use rustc_middle::ty::{self, List, TyCtxt, TypeFoldable}; | |
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 | |
dfeec247 | 29 | use crate::const_eval::{is_const_fn, is_unstable_const_fn}; |
f9f354fc | 30 | use crate::transform::check_consts::{is_lang_panic_fn, qualifs, ConstCx}; |
29967ef6 | 31 | use crate::transform::MirPass; |
e74abb32 | 32 | |
60c5eb7d XL |
33 | /// A `MirPass` for promotion. |
34 | /// | |
17df50a5 XL |
35 | /// Promotion is the extraction of promotable temps into separate MIR bodies so they can have |
36 | /// `'static` lifetime. | |
60c5eb7d XL |
37 | /// |
38 | /// After this pass is run, `promoted_fragments` will hold the MIR body corresponding to each | |
dfeec247 | 39 | /// newly created `Constant`. |
60c5eb7d XL |
40 | #[derive(Default)] |
41 | pub struct PromoteTemps<'tcx> { | |
f9f354fc | 42 | pub promoted_fragments: Cell<IndexVec<Promoted, Body<'tcx>>>, |
60c5eb7d XL |
43 | } |
44 | ||
45 | impl<'tcx> MirPass<'tcx> for PromoteTemps<'tcx> { | |
29967ef6 | 46 | fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { |
60c5eb7d XL |
47 | // There's not really any point in promoting errorful MIR. |
48 | // | |
49 | // This does not include MIR that failed const-checking, which we still try to promote. | |
50 | if body.return_ty().references_error() { | |
51 | tcx.sess.delay_span_bug(body.span, "PromoteTemps: MIR had errors"); | |
52 | return; | |
53 | } | |
54 | ||
29967ef6 | 55 | if body.source.promoted.is_some() { |
60c5eb7d XL |
56 | return; |
57 | } | |
58 | ||
60c5eb7d | 59 | let mut rpo = traversal::reverse_postorder(body); |
29967ef6 | 60 | let ccx = ConstCx::new(tcx, body); |
f9f354fc | 61 | let (temps, all_candidates) = collect_temps_and_candidates(&ccx, &mut rpo); |
60c5eb7d | 62 | |
f9f354fc | 63 | let promotable_candidates = validate_candidates(&ccx, &temps, &all_candidates); |
60c5eb7d | 64 | |
29967ef6 | 65 | let promoted = promote_candidates(body, tcx, temps, promotable_candidates); |
60c5eb7d XL |
66 | self.promoted_fragments.set(promoted); |
67 | } | |
68 | } | |
69 | ||
a7813a04 XL |
70 | /// State of a temporary during collection and promotion. |
71 | #[derive(Copy, Clone, PartialEq, Eq, Debug)] | |
72 | pub enum TempState { | |
73 | /// No references to this temp. | |
74 | Undefined, | |
75 | /// One direct assignment and any number of direct uses. | |
76 | /// A borrow of this temp is promotable if the assigned | |
77 | /// value is qualified as constant. | |
dfeec247 | 78 | Defined { location: Location, uses: usize }, |
a7813a04 XL |
79 | /// Any other combination of assignments/uses. |
80 | Unpromotable, | |
81 | /// This temp was part of an rvalue which got extracted | |
82 | /// during promotion and needs cleanup. | |
dfeec247 | 83 | PromotedOut, |
a7813a04 XL |
84 | } |
85 | ||
86 | impl TempState { | |
87 | pub fn is_promotable(&self) -> bool { | |
13cf67c4 | 88 | debug!("is_promotable: self={:?}", self); |
5869c6ff | 89 | matches!(self, TempState::Defined { .. }) |
a7813a04 XL |
90 | } |
91 | } | |
92 | ||
93 | /// A "root candidate" for promotion, which will become the | |
94 | /// returned value in a promoted MIR, unless it's a subset | |
95 | /// of a larger candidate. | |
e74abb32 | 96 | #[derive(Copy, Clone, PartialEq, Eq, Debug)] |
a7813a04 | 97 | pub enum Candidate { |
3dfed10e | 98 | /// Borrow of a constant temporary, candidate for lifetime extension. |
a7813a04 | 99 | Ref(Location), |
a7813a04 XL |
100 | } |
101 | ||
e74abb32 | 102 | impl Candidate { |
29967ef6 XL |
103 | fn source_info(&self, body: &Body<'_>) -> SourceInfo { |
104 | match self { | |
5869c6ff | 105 | Candidate::Ref(location) => *body.source_info(*location), |
29967ef6 XL |
106 | } |
107 | } | |
e74abb32 XL |
108 | } |
109 | ||
e74abb32 | 110 | struct Collector<'a, 'tcx> { |
f9f354fc | 111 | ccx: &'a ConstCx<'a, 'tcx>, |
c30ab7b3 | 112 | temps: IndexVec<Local, TempState>, |
e74abb32 | 113 | candidates: Vec<Candidate>, |
a7813a04 XL |
114 | } |
115 | ||
e74abb32 | 116 | impl<'tcx> Visitor<'tcx> for Collector<'_, 'tcx> { |
dfeec247 | 117 | fn visit_local(&mut self, &index: &Local, context: PlaceContext, location: Location) { |
13cf67c4 | 118 | debug!("visit_local: index={:?} context={:?} location={:?}", index, context, location); |
48663c56 | 119 | // We're only interested in temporaries and the return place |
f9f354fc | 120 | match self.ccx.body.local_kind(index) { |
dfeec247 XL |
121 | LocalKind::Temp | LocalKind::ReturnPointer => {} |
122 | LocalKind::Arg | LocalKind::Var => return, | |
ea8adc8c | 123 | } |
c30ab7b3 | 124 | |
ea8adc8c XL |
125 | // Ignore drops, if the temp gets promoted, |
126 | // then it's constant and thus drop is noop. | |
60c5eb7d | 127 | // Non-uses are also irrelevant. |
13cf67c4 XL |
128 | if context.is_drop() || !context.is_use() { |
129 | debug!( | |
130 | "visit_local: context.is_drop={:?} context.is_use={:?}", | |
dfeec247 XL |
131 | context.is_drop(), |
132 | context.is_use(), | |
13cf67c4 | 133 | ); |
ea8adc8c XL |
134 | return; |
135 | } | |
a7813a04 | 136 | |
ea8adc8c | 137 | let temp = &mut self.temps[index]; |
13cf67c4 | 138 | debug!("visit_local: temp={:?}", temp); |
ea8adc8c XL |
139 | if *temp == TempState::Undefined { |
140 | match context { | |
dfeec247 XL |
141 | PlaceContext::MutatingUse(MutatingUseContext::Store) |
142 | | PlaceContext::MutatingUse(MutatingUseContext::Call) => { | |
143 | *temp = TempState::Defined { location, uses: 0 }; | |
32a655c1 | 144 | return; |
a7813a04 | 145 | } |
ea8adc8c | 146 | _ => { /* mark as unpromotable below */ } |
a7813a04 | 147 | } |
ea8adc8c XL |
148 | } else if let TempState::Defined { ref mut uses, .. } = *temp { |
149 | // We always allow borrows, even mutable ones, as we need | |
0731742a | 150 | // to promote mutable borrows of some ZSTs e.g., `&mut []`. |
dfeec247 XL |
151 | let allowed_use = match context { |
152 | PlaceContext::MutatingUse(MutatingUseContext::Borrow) | |
153 | | PlaceContext::NonMutatingUse(_) => true, | |
154 | PlaceContext::MutatingUse(_) | PlaceContext::NonUse(_) => false, | |
155 | }; | |
13cf67c4 | 156 | debug!("visit_local: allowed_use={:?}", allowed_use); |
ea8adc8c XL |
157 | if allowed_use { |
158 | *uses += 1; | |
159 | return; | |
160 | } | |
161 | /* mark as unpromotable below */ | |
a7813a04 | 162 | } |
ea8adc8c | 163 | *temp = TempState::Unpromotable; |
a7813a04 XL |
164 | } |
165 | ||
e74abb32 XL |
166 | fn visit_rvalue(&mut self, rvalue: &Rvalue<'tcx>, location: Location) { |
167 | self.super_rvalue(rvalue, location); | |
168 | ||
169 | match *rvalue { | |
170 | Rvalue::Ref(..) => { | |
171 | self.candidates.push(Candidate::Ref(location)); | |
172 | } | |
e74abb32 XL |
173 | _ => {} |
174 | } | |
175 | } | |
a7813a04 XL |
176 | } |
177 | ||
e74abb32 | 178 | pub fn collect_temps_and_candidates( |
f9f354fc | 179 | ccx: &ConstCx<'mir, 'tcx>, |
e74abb32 XL |
180 | rpo: &mut ReversePostorder<'_, 'tcx>, |
181 | ) -> (IndexVec<Local, TempState>, Vec<Candidate>) { | |
182 | let mut collector = Collector { | |
f9f354fc | 183 | temps: IndexVec::from_elem(TempState::Undefined, &ccx.body.local_decls), |
e74abb32 | 184 | candidates: vec![], |
f9f354fc | 185 | ccx, |
a7813a04 XL |
186 | }; |
187 | for (bb, data) in rpo { | |
188 | collector.visit_basic_block_data(bb, data); | |
189 | } | |
e74abb32 XL |
190 | (collector.temps, collector.candidates) |
191 | } | |
192 | ||
193 | /// Checks whether locals that appear in a promotion context (`Candidate`) are actually promotable. | |
194 | /// | |
195 | /// This wraps an `Item`, and has access to all fields of that `Item` via `Deref` coercion. | |
196 | struct Validator<'a, 'tcx> { | |
f9f354fc | 197 | ccx: &'a ConstCx<'a, 'tcx>, |
e74abb32 | 198 | temps: &'a IndexVec<Local, TempState>, |
e74abb32 XL |
199 | } |
200 | ||
201 | impl std::ops::Deref for Validator<'a, 'tcx> { | |
f9f354fc | 202 | type Target = ConstCx<'a, 'tcx>; |
e74abb32 XL |
203 | |
204 | fn deref(&self) -> &Self::Target { | |
f9f354fc | 205 | &self.ccx |
e74abb32 XL |
206 | } |
207 | } | |
208 | ||
209 | struct Unpromotable; | |
210 | ||
211 | impl<'tcx> Validator<'_, 'tcx> { | |
212 | fn validate_candidate(&self, candidate: Candidate) -> Result<(), Unpromotable> { | |
213 | match candidate { | |
214 | Candidate::Ref(loc) => { | |
e74abb32 XL |
215 | let statement = &self.body[loc.block].statements[loc.statement_index]; |
216 | match &statement.kind { | |
dfeec247 | 217 | StatementKind::Assign(box (_, Rvalue::Ref(_, kind, place))) => { |
e74abb32 XL |
218 | // We can only promote interior borrows of promotable temps (non-temps |
219 | // don't get promoted anyway). | |
dfeec247 | 220 | self.validate_local(place.local)?; |
e74abb32 | 221 | |
5869c6ff XL |
222 | // The reference operation itself must be promotable. |
223 | // (Needs to come after `validate_local` to avoid ICEs.) | |
224 | self.validate_ref(*kind, place)?; | |
225 | ||
226 | // We do not check all the projections (they do not get promoted anyway), | |
227 | // but we do stay away from promoting anything involving a dereference. | |
e74abb32 XL |
228 | if place.projection.contains(&ProjectionElem::Deref) { |
229 | return Err(Unpromotable); | |
230 | } | |
e74abb32 | 231 | |
5869c6ff XL |
232 | // We cannot promote things that need dropping, since the promoted value |
233 | // would not get dropped. | |
234 | if self.qualif_local::<qualifs::NeedsDrop>(place.local) { | |
e74abb32 XL |
235 | return Err(Unpromotable); |
236 | } | |
e74abb32 | 237 | |
e74abb32 XL |
238 | Ok(()) |
239 | } | |
dfeec247 | 240 | _ => bug!(), |
e74abb32 XL |
241 | } |
242 | } | |
e74abb32 XL |
243 | } |
244 | } | |
245 | ||
246 | // FIXME(eddyb) maybe cache this? | |
247 | fn qualif_local<Q: qualifs::Qualif>(&self, local: Local) -> bool { | |
e74abb32 XL |
248 | if let TempState::Defined { location: loc, .. } = self.temps[local] { |
249 | let num_stmts = self.body[loc.block].statements.len(); | |
250 | ||
251 | if loc.statement_index < num_stmts { | |
252 | let statement = &self.body[loc.block].statements[loc.statement_index]; | |
253 | match &statement.kind { | |
ba9703b0 | 254 | StatementKind::Assign(box (_, rhs)) => qualifs::in_rvalue::<Q, _>( |
f9f354fc | 255 | &self.ccx, |
ba9703b0 XL |
256 | &mut |l| self.qualif_local::<Q>(l), |
257 | rhs, | |
258 | ), | |
e74abb32 | 259 | _ => { |
dfeec247 XL |
260 | span_bug!( |
261 | statement.source_info.span, | |
262 | "{:?} is not an assignment", | |
263 | statement | |
264 | ); | |
e74abb32 XL |
265 | } |
266 | } | |
267 | } else { | |
268 | let terminator = self.body[loc.block].terminator(); | |
269 | match &terminator.kind { | |
ba9703b0 | 270 | TerminatorKind::Call { .. } => { |
e74abb32 | 271 | let return_ty = self.body.local_decls[local].ty; |
f9f354fc | 272 | Q::in_any_value_of_ty(&self.ccx, return_ty) |
e74abb32 XL |
273 | } |
274 | kind => { | |
275 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); | |
276 | } | |
277 | } | |
278 | } | |
279 | } else { | |
280 | let span = self.body.local_decls[local].source_info.span; | |
281 | span_bug!(span, "{:?} not promotable, qualif_local shouldn't have been called", local); | |
282 | } | |
283 | } | |
284 | ||
285 | // FIXME(eddyb) maybe cache this? | |
286 | fn validate_local(&self, local: Local) -> Result<(), Unpromotable> { | |
287 | if let TempState::Defined { location: loc, .. } = self.temps[local] { | |
5869c6ff XL |
288 | let block = &self.body[loc.block]; |
289 | let num_stmts = block.statements.len(); | |
e74abb32 XL |
290 | |
291 | if loc.statement_index < num_stmts { | |
5869c6ff | 292 | let statement = &block.statements[loc.statement_index]; |
e74abb32 | 293 | match &statement.kind { |
dfeec247 | 294 | StatementKind::Assign(box (_, rhs)) => self.validate_rvalue(rhs), |
e74abb32 | 295 | _ => { |
dfeec247 XL |
296 | span_bug!( |
297 | statement.source_info.span, | |
298 | "{:?} is not an assignment", | |
299 | statement | |
300 | ); | |
e74abb32 XL |
301 | } |
302 | } | |
303 | } else { | |
5869c6ff | 304 | let terminator = block.terminator(); |
e74abb32 XL |
305 | match &terminator.kind { |
306 | TerminatorKind::Call { func, args, .. } => self.validate_call(func, args), | |
74b04a01 | 307 | TerminatorKind::Yield { .. } => Err(Unpromotable), |
e74abb32 XL |
308 | kind => { |
309 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); | |
310 | } | |
311 | } | |
312 | } | |
313 | } else { | |
314 | Err(Unpromotable) | |
315 | } | |
316 | } | |
317 | ||
74b04a01 | 318 | fn validate_place(&self, place: PlaceRef<'tcx>) -> Result<(), Unpromotable> { |
5869c6ff XL |
319 | match place.last_projection() { |
320 | None => self.validate_local(place.local), | |
321 | Some((place_base, elem)) => { | |
1b1a35ee | 322 | // Validate topmost projection, then recurse. |
5869c6ff | 323 | match elem { |
3dfed10e | 324 | ProjectionElem::Deref => { |
1b1a35ee | 325 | let mut promotable = false; |
5869c6ff XL |
326 | // We need to make sure this is a `Deref` of a local with no further projections. |
327 | // Discussion can be found at | |
328 | // https://github.com/rust-lang/rust/pull/74945#discussion_r463063247 | |
329 | if let Some(local) = place_base.as_local() { | |
330 | // This is a special treatment for cases like *&STATIC where STATIC is a | |
331 | // global static variable. | |
332 | // This pattern is generated only when global static variables are directly | |
333 | // accessed and is qualified for promotion safely. | |
334 | if let TempState::Defined { location, .. } = self.temps[local] { | |
335 | let def_stmt = self.body[location.block] | |
336 | .statements | |
337 | .get(location.statement_index); | |
338 | if let Some(Statement { | |
339 | kind: | |
340 | StatementKind::Assign(box ( | |
341 | _, | |
342 | Rvalue::Use(Operand::Constant(c)), | |
343 | )), | |
344 | .. | |
345 | }) = def_stmt | |
346 | { | |
347 | if let Some(did) = c.check_static_ptr(self.tcx) { | |
348 | // Evaluating a promoted may not read statics except if it got | |
349 | // promoted from a static (this is a CTFE check). So we | |
350 | // can only promote static accesses inside statics. | |
351 | if let Some(hir::ConstContext::Static(..)) = self.const_kind | |
3dfed10e | 352 | { |
5869c6ff XL |
353 | if !self.tcx.is_thread_local_static(did) { |
354 | promotable = true; | |
355 | } | |
3dfed10e XL |
356 | } |
357 | } | |
358 | } | |
359 | } | |
360 | } | |
1b1a35ee | 361 | if !promotable { |
3dfed10e XL |
362 | return Err(Unpromotable); |
363 | } | |
364 | } | |
365 | ProjectionElem::Downcast(..) => { | |
dfeec247 XL |
366 | return Err(Unpromotable); |
367 | } | |
e74abb32 | 368 | |
dfeec247 | 369 | ProjectionElem::ConstantIndex { .. } | ProjectionElem::Subslice { .. } => {} |
e74abb32 XL |
370 | |
371 | ProjectionElem::Index(local) => { | |
17df50a5 XL |
372 | let mut promotable = false; |
373 | // Only accept if we can predict the index and are indexing an array. | |
374 | let val = | |
375 | if let TempState::Defined { location: loc, .. } = self.temps[local] { | |
5869c6ff XL |
376 | let block = &self.body[loc.block]; |
377 | if loc.statement_index < block.statements.len() { | |
378 | let statement = &block.statements[loc.statement_index]; | |
379 | match &statement.kind { | |
380 | StatementKind::Assign(box ( | |
381 | _, | |
382 | Rvalue::Use(Operand::Constant(c)), | |
383 | )) => c.literal.try_eval_usize(self.tcx, self.param_env), | |
384 | _ => None, | |
385 | } | |
386 | } else { | |
387 | None | |
388 | } | |
389 | } else { | |
390 | None | |
391 | }; | |
17df50a5 XL |
392 | if let Some(idx) = val { |
393 | // Determine the type of the thing we are indexing. | |
394 | let ty = place_base.ty(self.body, self.tcx).ty; | |
395 | match ty.kind() { | |
396 | ty::Array(_, len) => { | |
397 | // It's an array; determine its length. | |
398 | if let Some(len) = len.try_eval_usize(self.tcx, self.param_env) | |
399 | { | |
400 | // If the index is in-bounds, go ahead. | |
401 | if idx < len { | |
402 | promotable = true; | |
5869c6ff XL |
403 | } |
404 | } | |
5869c6ff | 405 | } |
17df50a5 | 406 | _ => {} |
5869c6ff XL |
407 | } |
408 | } | |
17df50a5 XL |
409 | if !promotable { |
410 | return Err(Unpromotable); | |
411 | } | |
412 | ||
e74abb32 XL |
413 | self.validate_local(local)?; |
414 | } | |
415 | ||
416 | ProjectionElem::Field(..) => { | |
5869c6ff | 417 | let base_ty = place_base.ty(self.body, self.tcx).ty; |
17df50a5 | 418 | if base_ty.is_union() { |
29967ef6 | 419 | // No promotion of union field accesses. |
17df50a5 | 420 | return Err(Unpromotable); |
e74abb32 XL |
421 | } |
422 | } | |
423 | } | |
424 | ||
5869c6ff | 425 | self.validate_place(place_base) |
e74abb32 XL |
426 | } |
427 | } | |
428 | } | |
429 | ||
430 | fn validate_operand(&self, operand: &Operand<'tcx>) -> Result<(), Unpromotable> { | |
431 | match operand { | |
dfeec247 | 432 | Operand::Copy(place) | Operand::Move(place) => self.validate_place(place.as_ref()), |
e74abb32 | 433 | |
60c5eb7d XL |
434 | // The qualifs for a constant (e.g. `HasMutInterior`) are checked in |
435 | // `validate_rvalue` upon access. | |
436 | Operand::Constant(c) => { | |
437 | if let Some(def_id) = c.check_static_ptr(self.tcx) { | |
438 | // Only allow statics (not consts) to refer to other statics. | |
439 | // FIXME(eddyb) does this matter at all for promotion? | |
1b1a35ee XL |
440 | // FIXME(RalfJung) it makes little sense to not promote this in `fn`/`const fn`, |
441 | // and in `const` this cannot occur anyway. The only concern is that we might | |
442 | // promote even `let x = &STATIC` which would be useless, but this applies to | |
443 | // promotion inside statics as well. | |
f9f354fc | 444 | let is_static = matches!(self.const_kind, Some(hir::ConstContext::Static(_))); |
60c5eb7d XL |
445 | if !is_static { |
446 | return Err(Unpromotable); | |
447 | } | |
448 | ||
f9f354fc | 449 | let is_thread_local = self.tcx.is_thread_local_static(def_id); |
60c5eb7d XL |
450 | if is_thread_local { |
451 | return Err(Unpromotable); | |
e74abb32 XL |
452 | } |
453 | } | |
454 | ||
455 | Ok(()) | |
dfeec247 | 456 | } |
e74abb32 XL |
457 | } |
458 | } | |
459 | ||
5869c6ff XL |
460 | fn validate_ref(&self, kind: BorrowKind, place: &Place<'tcx>) -> Result<(), Unpromotable> { |
461 | match kind { | |
462 | // Reject these borrow types just to be safe. | |
463 | // FIXME(RalfJung): could we allow them? Should we? No point in it until we have a usecase. | |
464 | BorrowKind::Shallow | BorrowKind::Unique => return Err(Unpromotable), | |
465 | ||
466 | BorrowKind::Shared => { | |
467 | let has_mut_interior = self.qualif_local::<qualifs::HasMutInterior>(place.local); | |
468 | if has_mut_interior { | |
1b1a35ee | 469 | return Err(Unpromotable); |
e74abb32 XL |
470 | } |
471 | } | |
472 | ||
5869c6ff XL |
473 | BorrowKind::Mut { .. } => { |
474 | let ty = place.ty(self.body, self.tcx).ty; | |
475 | ||
476 | // In theory, any zero-sized value could be borrowed | |
477 | // mutably without consequences. However, only &mut [] | |
478 | // is allowed right now. | |
479 | if let ty::Array(_, len) = ty.kind() { | |
480 | match len.try_eval_usize(self.tcx, self.param_env) { | |
481 | Some(0) => {} | |
482 | _ => return Err(Unpromotable), | |
483 | } | |
484 | } else { | |
e74abb32 XL |
485 | return Err(Unpromotable); |
486 | } | |
487 | } | |
e74abb32 XL |
488 | } |
489 | ||
5869c6ff XL |
490 | Ok(()) |
491 | } | |
492 | ||
493 | fn validate_rvalue(&self, rvalue: &Rvalue<'tcx>) -> Result<(), Unpromotable> { | |
e74abb32 | 494 | match rvalue { |
5869c6ff XL |
495 | Rvalue::Use(operand) | Rvalue::Repeat(operand, _) => { |
496 | self.validate_operand(operand)?; | |
497 | } | |
498 | ||
499 | Rvalue::Discriminant(place) | Rvalue::Len(place) => { | |
500 | self.validate_place(place.as_ref())? | |
501 | } | |
502 | ||
503 | Rvalue::ThreadLocalRef(_) => return Err(Unpromotable), | |
504 | ||
505 | Rvalue::Cast(kind, operand, cast_ty) => { | |
506 | if matches!(kind, CastKind::Misc) { | |
507 | let operand_ty = operand.ty(self.body, self.tcx); | |
508 | let cast_in = CastTy::from_ty(operand_ty).expect("bad input type for cast"); | |
509 | let cast_out = CastTy::from_ty(cast_ty).expect("bad output type for cast"); | |
510 | if let (CastTy::Ptr(_) | CastTy::FnPtr, CastTy::Int(_)) = (cast_in, cast_out) { | |
511 | // ptr-to-int casts are not possible in consts and thus not promotable | |
512 | return Err(Unpromotable); | |
513 | } | |
514 | // int-to-ptr casts are fine, they just use the integer value at pointer type. | |
515 | } | |
516 | ||
517 | self.validate_operand(operand)?; | |
518 | } | |
519 | ||
520 | Rvalue::NullaryOp(op, _) => match op { | |
521 | NullOp::Box => return Err(Unpromotable), | |
522 | NullOp::SizeOf => {} | |
523 | }, | |
f9f354fc | 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) => { | |
559 | c.literal.try_eval_bits(self.tcx, self.param_env, lhs_ty) | |
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 | |
578 | | BinOp::Sub | |
579 | | BinOp::Mul | |
580 | | BinOp::BitXor | |
581 | | BinOp::BitAnd | |
582 | | BinOp::BitOr | |
583 | | BinOp::Shl | |
584 | | BinOp::Shr => {} | |
585 | } | |
e74abb32 | 586 | |
e74abb32 | 587 | self.validate_operand(lhs)?; |
5869c6ff | 588 | self.validate_operand(rhs)?; |
e74abb32 XL |
589 | } |
590 | ||
dfeec247 | 591 | Rvalue::AddressOf(_, place) => { |
1b1a35ee XL |
592 | // We accept `&raw *`, i.e., raw reborrows -- creating a raw pointer is |
593 | // no problem, only using it is. | |
5869c6ff XL |
594 | if let Some((place_base, ProjectionElem::Deref)) = place.as_ref().last_projection() |
595 | { | |
596 | let base_ty = place_base.ty(self.body, self.tcx).ty; | |
1b1a35ee | 597 | if let ty::Ref(..) = base_ty.kind() { |
5869c6ff | 598 | return self.validate_place(place_base); |
dfeec247 XL |
599 | } |
600 | } | |
5869c6ff | 601 | return Err(Unpromotable); |
dfeec247 XL |
602 | } |
603 | ||
e74abb32 | 604 | Rvalue::Ref(_, kind, place) => { |
e74abb32 | 605 | // Special-case reborrows to be more like a copy of the reference. |
5869c6ff XL |
606 | let mut place_simplified = place.as_ref(); |
607 | if let Some((place_base, ProjectionElem::Deref)) = | |
608 | place_simplified.last_projection() | |
609 | { | |
610 | let base_ty = place_base.ty(self.body, self.tcx).ty; | |
1b1a35ee | 611 | if let ty::Ref(..) = base_ty.kind() { |
5869c6ff | 612 | place_simplified = place_base; |
e74abb32 XL |
613 | } |
614 | } | |
615 | ||
5869c6ff | 616 | self.validate_place(place_simplified)?; |
e74abb32 | 617 | |
5869c6ff XL |
618 | // Check that the reference is fine (using the original place!). |
619 | // (Needs to come after `validate_place` to avoid ICEs.) | |
620 | self.validate_ref(*kind, place)?; | |
e74abb32 XL |
621 | } |
622 | ||
5869c6ff | 623 | Rvalue::Aggregate(_, operands) => { |
e74abb32 XL |
624 | for o in operands { |
625 | self.validate_operand(o)?; | |
626 | } | |
e74abb32 XL |
627 | } |
628 | } | |
5869c6ff XL |
629 | |
630 | Ok(()) | |
e74abb32 XL |
631 | } |
632 | ||
633 | fn validate_call( | |
634 | &self, | |
635 | callee: &Operand<'tcx>, | |
636 | args: &[Operand<'tcx>], | |
637 | ) -> Result<(), Unpromotable> { | |
f9f354fc | 638 | let fn_ty = callee.ty(self.body, self.tcx); |
e74abb32 | 639 | |
17df50a5 | 640 | // Inside const/static items, we promote all (eligible) function calls. |
29967ef6 | 641 | // Everywhere else, we require `#[rustc_promotable]` on the callee. |
17df50a5 XL |
642 | let promote_all_const_fn = matches!( |
643 | self.const_kind, | |
644 | Some(hir::ConstContext::Static(_) | hir::ConstContext::Const) | |
645 | ); | |
29967ef6 | 646 | if !promote_all_const_fn { |
1b1a35ee | 647 | if let ty::FnDef(def_id, _) = *fn_ty.kind() { |
e74abb32 XL |
648 | // Never promote runtime `const fn` calls of |
649 | // functions without `#[rustc_promotable]`. | |
650 | if !self.tcx.is_promotable_const_fn(def_id) { | |
651 | return Err(Unpromotable); | |
652 | } | |
653 | } | |
654 | } | |
655 | ||
1b1a35ee | 656 | let is_const_fn = match *fn_ty.kind() { |
e74abb32 | 657 | ty::FnDef(def_id, _) => { |
dfeec247 XL |
658 | is_const_fn(self.tcx, def_id) |
659 | || is_unstable_const_fn(self.tcx, def_id).is_some() | |
29967ef6 | 660 | || is_lang_panic_fn(self.tcx, def_id) |
e74abb32 XL |
661 | } |
662 | _ => false, | |
663 | }; | |
664 | if !is_const_fn { | |
665 | return Err(Unpromotable); | |
666 | } | |
667 | ||
668 | self.validate_operand(callee)?; | |
669 | for arg in args { | |
670 | self.validate_operand(arg)?; | |
671 | } | |
672 | ||
673 | Ok(()) | |
674 | } | |
675 | } | |
676 | ||
677 | // FIXME(eddyb) remove the differences for promotability in `static`, `const`, `const fn`. | |
678 | pub fn validate_candidates( | |
f9f354fc | 679 | ccx: &ConstCx<'_, '_>, |
e74abb32 XL |
680 | temps: &IndexVec<Local, TempState>, |
681 | candidates: &[Candidate], | |
682 | ) -> Vec<Candidate> { | |
17df50a5 | 683 | let validator = Validator { ccx, temps }; |
e74abb32 | 684 | |
dfeec247 XL |
685 | candidates |
686 | .iter() | |
687 | .copied() | |
17df50a5 | 688 | .filter(|&candidate| validator.validate_candidate(candidate).is_ok()) |
dfeec247 | 689 | .collect() |
a7813a04 XL |
690 | } |
691 | ||
dc9dc135 XL |
692 | struct Promoter<'a, 'tcx> { |
693 | tcx: TyCtxt<'tcx>, | |
f9f354fc XL |
694 | source: &'a mut Body<'tcx>, |
695 | promoted: Body<'tcx>, | |
c30ab7b3 | 696 | temps: &'a mut IndexVec<Local, TempState>, |
dfeec247 | 697 | extra_statements: &'a mut Vec<(Location, Statement<'tcx>)>, |
a7813a04 XL |
698 | |
699 | /// If true, all nested temps are also kept in the | |
700 | /// source MIR, not moved to the promoted MIR. | |
dc9dc135 | 701 | keep_original: bool, |
a7813a04 XL |
702 | } |
703 | ||
704 | impl<'a, 'tcx> Promoter<'a, 'tcx> { | |
705 | fn new_block(&mut self) -> BasicBlock { | |
3157f602 XL |
706 | let span = self.promoted.span; |
707 | self.promoted.basic_blocks_mut().push(BasicBlockData { | |
a7813a04 XL |
708 | statements: vec![], |
709 | terminator: Some(Terminator { | |
f9f354fc | 710 | source_info: SourceInfo::outermost(span), |
dfeec247 | 711 | kind: TerminatorKind::Return, |
a7813a04 | 712 | }), |
dfeec247 | 713 | is_cleanup: false, |
3157f602 | 714 | }) |
a7813a04 XL |
715 | } |
716 | ||
c30ab7b3 | 717 | fn assign(&mut self, dest: Local, rvalue: Rvalue<'tcx>, span: Span) { |
3157f602 XL |
718 | let last = self.promoted.basic_blocks().last().unwrap(); |
719 | let data = &mut self.promoted[last]; | |
a7813a04 | 720 | data.statements.push(Statement { |
f9f354fc | 721 | source_info: SourceInfo::outermost(span), |
94222f64 | 722 | kind: StatementKind::Assign(Box::new((Place::from(dest), rvalue))), |
a7813a04 XL |
723 | }); |
724 | } | |
725 | ||
e74abb32 XL |
726 | fn is_temp_kind(&self, local: Local) -> bool { |
727 | self.source.local_kind(local) == LocalKind::Temp | |
728 | } | |
729 | ||
9fa01778 | 730 | /// Copies the initialization of this temp to the |
a7813a04 | 731 | /// promoted MIR, recursing through temps. |
c30ab7b3 | 732 | fn promote_temp(&mut self, temp: Local) -> Local { |
a7813a04 | 733 | let old_keep_original = self.keep_original; |
476ff2be SL |
734 | let loc = match self.temps[temp] { |
735 | TempState::Defined { location, uses } if uses > 0 => { | |
a7813a04 XL |
736 | if uses > 1 { |
737 | self.keep_original = true; | |
738 | } | |
476ff2be | 739 | location |
a7813a04 | 740 | } |
dfeec247 XL |
741 | state => { |
742 | span_bug!(self.promoted.span, "{:?} not promotable: {:?}", temp, state); | |
a7813a04 XL |
743 | } |
744 | }; | |
745 | if !self.keep_original { | |
3157f602 | 746 | self.temps[temp] = TempState::PromotedOut; |
a7813a04 XL |
747 | } |
748 | ||
e74abb32 | 749 | let num_stmts = self.source[loc.block].statements.len(); |
f9f354fc | 750 | let new_temp = self.promoted.local_decls.push(LocalDecl::new( |
dfeec247 XL |
751 | self.source.local_decls[temp].ty, |
752 | self.source.local_decls[temp].source_info.span, | |
753 | )); | |
476ff2be | 754 | |
dfeec247 | 755 | debug!("promote({:?} @ {:?}/{:?}, {:?})", temp, loc, num_stmts, self.keep_original); |
a7813a04 XL |
756 | |
757 | // First, take the Rvalue or Call out of the source MIR, | |
758 | // or duplicate it, depending on keep_original. | |
e74abb32 | 759 | if loc.statement_index < num_stmts { |
e1599b0c | 760 | let (mut rvalue, source_info) = { |
476ff2be SL |
761 | let statement = &mut self.source[loc.block].statements[loc.statement_index]; |
762 | let rhs = match statement.kind { | |
dfeec247 | 763 | StatementKind::Assign(box (_, ref mut rhs)) => rhs, |
476ff2be | 764 | _ => { |
dfeec247 XL |
765 | span_bug!( |
766 | statement.source_info.span, | |
767 | "{:?} is not an assignment", | |
768 | statement | |
769 | ); | |
476ff2be SL |
770 | } |
771 | }; | |
772 | ||
dfeec247 XL |
773 | ( |
774 | if self.keep_original { | |
775 | rhs.clone() | |
776 | } else { | |
94222f64 | 777 | let unit = Rvalue::Use(Operand::Constant(Box::new(Constant { |
ba9703b0 XL |
778 | span: statement.source_info.span, |
779 | user_ty: None, | |
6a06907d | 780 | literal: ty::Const::zero_sized(self.tcx, self.tcx.types.unit).into(), |
94222f64 | 781 | }))); |
dfeec247 XL |
782 | mem::replace(rhs, unit) |
783 | }, | |
784 | statement.source_info, | |
785 | ) | |
5bcae85e | 786 | }; |
476ff2be SL |
787 | |
788 | self.visit_rvalue(&mut rvalue, loc); | |
789 | self.assign(new_temp, rvalue, source_info.span); | |
a7813a04 | 790 | } else { |
476ff2be SL |
791 | let terminator = if self.keep_original { |
792 | self.source[loc.block].terminator().clone() | |
793 | } else { | |
794 | let terminator = self.source[loc.block].terminator_mut(); | |
795 | let target = match terminator.kind { | |
796 | TerminatorKind::Call { destination: Some((_, target)), .. } => target, | |
797 | ref kind => { | |
798 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); | |
799 | } | |
800 | }; | |
801 | Terminator { | |
802 | source_info: terminator.source_info, | |
dfeec247 | 803 | kind: mem::replace(&mut terminator.kind, TerminatorKind::Goto { target }), |
a7813a04 XL |
804 | } |
805 | }; | |
a7813a04 | 806 | |
476ff2be | 807 | match terminator.kind { |
f035d41b | 808 | TerminatorKind::Call { mut func, mut args, from_hir_call, fn_span, .. } => { |
476ff2be SL |
809 | self.visit_operand(&mut func, loc); |
810 | for arg in &mut args { | |
811 | self.visit_operand(arg, loc); | |
812 | } | |
a7813a04 | 813 | |
476ff2be SL |
814 | let last = self.promoted.basic_blocks().last().unwrap(); |
815 | let new_target = self.new_block(); | |
a7813a04 | 816 | |
476ff2be SL |
817 | *self.promoted[last].terminator_mut() = Terminator { |
818 | kind: TerminatorKind::Call { | |
3b2f2976 XL |
819 | func, |
820 | args, | |
476ff2be | 821 | cleanup: None, |
dfeec247 | 822 | destination: Some((Place::from(new_temp), new_target)), |
0bf4aa26 | 823 | from_hir_call, |
f035d41b | 824 | fn_span, |
476ff2be | 825 | }, |
29967ef6 | 826 | source_info: SourceInfo::outermost(terminator.source_info.span), |
476ff2be SL |
827 | ..terminator |
828 | }; | |
a7813a04 | 829 | } |
476ff2be SL |
830 | ref kind => { |
831 | span_bug!(terminator.source_info.span, "{:?} not promotable", kind); | |
832 | } | |
833 | }; | |
834 | }; | |
a7813a04 | 835 | |
a7813a04 | 836 | self.keep_original = old_keep_original; |
3157f602 | 837 | new_temp |
a7813a04 XL |
838 | } |
839 | ||
e1599b0c XL |
840 | fn promote_candidate( |
841 | mut self, | |
e1599b0c XL |
842 | candidate: Candidate, |
843 | next_promoted_id: usize, | |
f9f354fc | 844 | ) -> Option<Body<'tcx>> { |
29967ef6 | 845 | let def = self.source.source.with_opt_param(); |
dfeec247 | 846 | let mut rvalue = { |
94b46f34 | 847 | let promoted = &mut self.promoted; |
e1599b0c XL |
848 | let promoted_id = Promoted::new(next_promoted_id); |
849 | let tcx = self.tcx; | |
dfeec247 | 850 | let mut promoted_operand = |ty, span| { |
94b46f34 | 851 | promoted.span = span; |
f9f354fc | 852 | promoted.local_decls[RETURN_PLACE] = LocalDecl::new(ty, span); |
dfeec247 XL |
853 | |
854 | Operand::Constant(Box::new(Constant { | |
855 | span, | |
856 | user_ty: None, | |
6a06907d XL |
857 | literal: tcx |
858 | .mk_const(ty::Const { | |
859 | ty, | |
cdc7bbd5 | 860 | val: ty::ConstKind::Unevaluated(ty::Unevaluated { |
6a06907d | 861 | def, |
94222f64 XL |
862 | substs_: Some(InternalSubsts::for_item( |
863 | tcx, | |
864 | def.did, | |
865 | |param, _| { | |
866 | if let ty::GenericParamDefKind::Lifetime = param.kind { | |
867 | tcx.lifetimes.re_erased.into() | |
868 | } else { | |
869 | tcx.mk_param_from_def(param) | |
870 | } | |
871 | }, | |
872 | )), | |
cdc7bbd5 XL |
873 | promoted: Some(promoted_id), |
874 | }), | |
6a06907d XL |
875 | }) |
876 | .into(), | |
dfeec247 | 877 | })) |
94b46f34 XL |
878 | }; |
879 | let (blocks, local_decls) = self.source.basic_blocks_and_local_decls_mut(); | |
880 | match candidate { | |
881 | Candidate::Ref(loc) => { | |
74b04a01 | 882 | let statement = &mut blocks[loc.block].statements[loc.statement_index]; |
94b46f34 | 883 | match statement.kind { |
dfeec247 XL |
884 | StatementKind::Assign(box ( |
885 | _, | |
886 | Rvalue::Ref(ref mut region, borrow_kind, ref mut place), | |
887 | )) => { | |
416331ca | 888 | // Use the underlying local for this (necessarily interior) borrow. |
dfeec247 | 889 | let ty = local_decls.local_decls()[place.local].ty; |
94b46f34 XL |
890 | let span = statement.source_info.span; |
891 | ||
dfeec247 XL |
892 | let ref_ty = tcx.mk_ref( |
893 | tcx.lifetimes.re_erased, | |
894 | ty::TypeAndMut { ty, mutbl: borrow_kind.to_mutbl_lossy() }, | |
895 | ); | |
896 | ||
897 | *region = tcx.lifetimes.re_erased; | |
898 | ||
899 | let mut projection = vec![PlaceElem::Deref]; | |
900 | projection.extend(place.projection); | |
901 | place.projection = tcx.intern_place_elems(&projection); | |
902 | ||
903 | // Create a temp to hold the promoted reference. | |
904 | // This is because `*r` requires `r` to be a local, | |
905 | // otherwise we would use the `promoted` directly. | |
f9f354fc | 906 | let mut promoted_ref = LocalDecl::new(ref_ty, span); |
dfeec247 XL |
907 | promoted_ref.source_info = statement.source_info; |
908 | let promoted_ref = local_decls.push(promoted_ref); | |
909 | assert_eq!(self.temps.push(TempState::Unpromotable), promoted_ref); | |
910 | ||
911 | let promoted_ref_statement = Statement { | |
912 | source_info: statement.source_info, | |
913 | kind: StatementKind::Assign(Box::new(( | |
914 | Place::from(promoted_ref), | |
915 | Rvalue::Use(promoted_operand(ref_ty, span)), | |
916 | ))), | |
917 | }; | |
918 | self.extra_statements.push((loc, promoted_ref_statement)); | |
919 | ||
920 | Rvalue::Ref( | |
921 | tcx.lifetimes.re_erased, | |
922 | borrow_kind, | |
923 | Place { | |
924 | local: mem::replace(&mut place.local, promoted_ref), | |
925 | projection: List::empty(), | |
926 | }, | |
927 | ) | |
94b46f34 | 928 | } |
dfeec247 | 929 | _ => bug!(), |
a7813a04 XL |
930 | } |
931 | } | |
a7813a04 XL |
932 | } |
933 | }; | |
94b46f34 XL |
934 | |
935 | assert_eq!(self.new_block(), START_BLOCK); | |
dfeec247 XL |
936 | self.visit_rvalue( |
937 | &mut rvalue, | |
938 | Location { block: BasicBlock::new(0), statement_index: usize::MAX }, | |
939 | ); | |
c30ab7b3 | 940 | |
94b46f34 | 941 | let span = self.promoted.span; |
dfeec247 | 942 | self.assign(RETURN_PLACE, rvalue, span); |
e1599b0c | 943 | Some(self.promoted) |
a7813a04 XL |
944 | } |
945 | } | |
946 | ||
947 | /// Replaces all temporaries with their promoted counterparts. | |
948 | impl<'a, 'tcx> MutVisitor<'tcx> for Promoter<'a, 'tcx> { | |
e74abb32 XL |
949 | fn tcx(&self) -> TyCtxt<'tcx> { |
950 | self.tcx | |
951 | } | |
952 | ||
dfeec247 | 953 | fn visit_local(&mut self, local: &mut Local, _: PlaceContext, _: Location) { |
e74abb32 | 954 | if self.is_temp_kind(*local) { |
ea8adc8c | 955 | *local = self.promote_temp(*local); |
a7813a04 | 956 | } |
a7813a04 XL |
957 | } |
958 | } | |
959 | ||
dc9dc135 | 960 | pub fn promote_candidates<'tcx>( |
f9f354fc | 961 | body: &mut Body<'tcx>, |
dc9dc135 XL |
962 | tcx: TyCtxt<'tcx>, |
963 | mut temps: IndexVec<Local, TempState>, | |
964 | candidates: Vec<Candidate>, | |
f9f354fc | 965 | ) -> IndexVec<Promoted, Body<'tcx>> { |
a7813a04 | 966 | // Visit candidates in reverse, in case they're nested. |
476ff2be | 967 | debug!("promote_candidates({:?})", candidates); |
94b46f34 | 968 | |
e1599b0c XL |
969 | let mut promotions = IndexVec::new(); |
970 | ||
dfeec247 | 971 | let mut extra_statements = vec![]; |
a7813a04 | 972 | for candidate in candidates.into_iter().rev() { |
94b46f34 | 973 | match candidate { |
5869c6ff | 974 | Candidate::Ref(Location { block, statement_index }) => { |
ba9703b0 XL |
975 | if let StatementKind::Assign(box (place, _)) = |
976 | &body[block].statements[statement_index].kind | |
977 | { | |
978 | if let Some(local) = place.as_local() { | |
979 | if temps[local] == TempState::PromotedOut { | |
980 | // Already promoted. | |
981 | continue; | |
94b46f34 | 982 | } |
a7813a04 XL |
983 | } |
984 | } | |
a7813a04 | 985 | } |
94b46f34 XL |
986 | } |
987 | ||
dc9dc135 | 988 | // Declare return place local so that `mir::Body::new` doesn't complain. |
f9f354fc | 989 | let initial_locals = iter::once(LocalDecl::new(tcx.types.never, body.span)).collect(); |
dfeec247 | 990 | |
29967ef6 XL |
991 | let mut scope = body.source_scopes[candidate.source_info(body).scope].clone(); |
992 | scope.parent_scope = None; | |
993 | ||
994 | let promoted = Body::new( | |
94222f64 | 995 | tcx, |
29967ef6 | 996 | body.source, // `promoted` gets filled in below |
dfeec247 | 997 | IndexVec::new(), |
29967ef6 | 998 | IndexVec::from_elem_n(scope, 1), |
dfeec247 XL |
999 | initial_locals, |
1000 | IndexVec::new(), | |
1001 | 0, | |
1002 | vec![], | |
1003 | body.span, | |
6a06907d | 1004 | body.generator_kind(), |
dfeec247 | 1005 | ); |
c30ab7b3 | 1006 | |
8faf50e0 | 1007 | let promoter = Promoter { |
f9f354fc | 1008 | promoted, |
94b46f34 | 1009 | tcx, |
dc9dc135 | 1010 | source: body, |
a7813a04 | 1011 | temps: &mut temps, |
dfeec247 XL |
1012 | extra_statements: &mut extra_statements, |
1013 | keep_original: false, | |
a7813a04 | 1014 | }; |
e1599b0c XL |
1015 | |
1016 | //FIXME(oli-obk): having a `maybe_push()` method on `IndexVec` might be nice | |
29967ef6 XL |
1017 | if let Some(mut promoted) = promoter.promote_candidate(candidate, promotions.len()) { |
1018 | promoted.source.promoted = Some(promotions.next_index()); | |
e1599b0c XL |
1019 | promotions.push(promoted); |
1020 | } | |
a7813a04 XL |
1021 | } |
1022 | ||
dfeec247 XL |
1023 | // Insert each of `extra_statements` before its indicated location, which |
1024 | // has to be done in reverse location order, to not invalidate the rest. | |
1025 | extra_statements.sort_by_key(|&(loc, _)| cmp::Reverse(loc)); | |
1026 | for (loc, statement) in extra_statements { | |
1027 | body[loc.block].statements.insert(loc.statement_index, statement); | |
1028 | } | |
1029 | ||
a7813a04 | 1030 | // Eliminate assignments to, and drops of promoted temps. |
c30ab7b3 | 1031 | let promoted = |index: Local| temps[index] == TempState::PromotedOut; |
dc9dc135 | 1032 | for block in body.basic_blocks_mut() { |
dfeec247 XL |
1033 | block.statements.retain(|statement| match &statement.kind { |
1034 | StatementKind::Assign(box (place, _)) => { | |
1035 | if let Some(index) = place.as_local() { | |
1036 | !promoted(index) | |
1037 | } else { | |
1038 | true | |
a7813a04 | 1039 | } |
a7813a04 | 1040 | } |
dfeec247 XL |
1041 | StatementKind::StorageLive(index) | StatementKind::StorageDead(index) => { |
1042 | !promoted(*index) | |
1043 | } | |
1044 | _ => true, | |
a7813a04 XL |
1045 | }); |
1046 | let terminator = block.terminator_mut(); | |
f035d41b | 1047 | if let TerminatorKind::Drop { place, target, .. } = &terminator.kind { |
ba9703b0 XL |
1048 | if let Some(index) = place.as_local() { |
1049 | if promoted(index) { | |
1050 | terminator.kind = TerminatorKind::Goto { target: *target }; | |
a7813a04 XL |
1051 | } |
1052 | } | |
a7813a04 XL |
1053 | } |
1054 | } | |
e1599b0c XL |
1055 | |
1056 | promotions | |
a7813a04 | 1057 | } |
6a06907d XL |
1058 | |
1059 | /// This function returns `true` if the function being called in the array | |
1060 | /// repeat expression is a `const` function. | |
1061 | crate fn is_const_fn_in_array_repeat_expression<'tcx>( | |
1062 | ccx: &ConstCx<'_, 'tcx>, | |
1063 | place: &Place<'tcx>, | |
1064 | body: &Body<'tcx>, | |
1065 | ) -> bool { | |
1066 | match place.as_local() { | |
1067 | // rule out cases such as: `let my_var = some_fn(); [my_var; N]` | |
1068 | Some(local) if body.local_decls[local].is_user_variable() => return false, | |
1069 | None => return false, | |
1070 | _ => {} | |
1071 | } | |
1072 | ||
1073 | for block in body.basic_blocks() { | |
1074 | if let Some(Terminator { kind: TerminatorKind::Call { func, destination, .. }, .. }) = | |
1075 | &block.terminator | |
1076 | { | |
1077 | if let Operand::Constant(box Constant { literal, .. }) = func { | |
1078 | if let ty::FnDef(def_id, _) = *literal.ty().kind() { | |
1079 | if let Some((destination_place, _)) = destination { | |
1080 | if destination_place == place { | |
1081 | if is_const_fn(ccx.tcx, def_id) { | |
1082 | return true; | |
1083 | } | |
1084 | } | |
1085 | } | |
1086 | } | |
1087 | } | |
1088 | } | |
1089 | } | |
1090 | ||
1091 | false | |
1092 | } |