1 #![feature(box_patterns)]
2 #![feature(box_syntax)]
3 #![feature(crate_visibility_modifier)]
4 #![cfg_attr(bootstrap, feature(const_panic))]
5 #![feature(in_band_lifetimes)]
7 #![feature(map_try_insert)]
8 #![feature(min_specialization)]
9 #![feature(option_get_or_insert_default)]
10 #![feature(once_cell)]
11 #![feature(never_type)]
12 #![feature(trusted_step)]
13 #![feature(try_blocks)]
14 #![recursion_limit = "256"]
19 extern crate rustc_middle;
21 use required_consts::RequiredConstsVisitor;
22 use rustc_const_eval::util;
23 use rustc_data_structures::fx::FxHashSet;
24 use rustc_data_structures::steal::Steal;
26 use rustc_hir::def_id::{DefId, LocalDefId};
27 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
28 use rustc_index::vec::IndexVec;
29 use rustc_middle::mir::visit::Visitor as _;
30 use rustc_middle::mir::{traversal, Body, ConstQualifs, MirPhase, Promoted};
31 use rustc_middle::ty::query::Providers;
32 use rustc_middle::ty::{self, TyCtxt, TypeFoldable};
33 use rustc_span::{Span, Symbol};
35 mod abort_unwinding_calls;
37 mod add_moves_for_packed_drops;
39 mod check_const_item_mutation;
41 pub mod check_unsafety;
42 mod cleanup_post_borrowck;
48 mod deduplicate_blocks;
51 mod early_otherwise_branch;
53 mod function_item_references;
60 mod multiple_return_terminators;
62 mod remove_noop_landing_pads;
63 mod remove_storage_markers;
64 mod remove_unneeded_drops;
67 mod separate_const_switch;
70 mod simplify_branches;
71 mod simplify_comparison_integral;
73 mod uninhabited_enum_branching;
76 use rustc_const_eval::transform::check_consts;
77 use rustc_const_eval::transform::promote_consts;
78 use rustc_const_eval::transform::validate;
79 pub use rustc_const_eval::transform::MirPass;
80 use rustc_mir_dataflow::rustc_peek;
82 pub fn provide(providers: &mut Providers) {
83 check_unsafety::provide(providers);
84 check_packed_ref::provide(providers);
85 coverage::query::provide(providers);
86 shim::provide(providers);
87 *providers = Providers {
90 mir_const_qualif: |tcx, def_id| {
91 let def_id = def_id.expect_local();
92 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
93 tcx.mir_const_qualif_const_arg(def)
95 mir_const_qualif(tcx, ty::WithOptConstParam::unknown(def_id))
98 mir_const_qualif_const_arg: |tcx, (did, param_did)| {
99 mir_const_qualif(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
102 mir_drops_elaborated_and_const_checked,
104 mir_for_ctfe_of_const_arg,
107 is_ctfe_mir_available: |tcx, did| is_mir_available(tcx, did),
108 mir_callgraph_reachable: inline::cycle::mir_callgraph_reachable,
109 mir_inliner_callees: inline::cycle::mir_inliner_callees,
110 promoted_mir: |tcx, def_id| {
111 let def_id = def_id.expect_local();
112 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
113 tcx.promoted_mir_of_const_arg(def)
115 promoted_mir(tcx, ty::WithOptConstParam::unknown(def_id))
118 promoted_mir_of_const_arg: |tcx, (did, param_did)| {
119 promoted_mir(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
125 fn is_mir_available(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
126 let def_id = def_id.expect_local();
127 tcx.mir_keys(()).contains(&def_id)
130 /// Finds the full set of `DefId`s within the current crate that have
131 /// MIR associated with them.
132 fn mir_keys(tcx: TyCtxt<'_>, (): ()) -> FxHashSet<LocalDefId> {
133 let mut set = FxHashSet::default();
135 // All body-owners have MIR associated with them.
136 set.extend(tcx.hir().body_owners());
138 // Additionally, tuple struct/variant constructors have MIR, but
139 // they don't have a BodyId, so we need to build them separately.
140 struct GatherCtors<'a, 'tcx> {
142 set: &'a mut FxHashSet<LocalDefId>,
144 impl<'a, 'tcx> Visitor<'tcx> for GatherCtors<'a, 'tcx> {
145 fn visit_variant_data(
147 v: &'tcx hir::VariantData<'tcx>,
149 _: &'tcx hir::Generics<'tcx>,
153 if let hir::VariantData::Tuple(_, hir_id) = *v {
154 self.set.insert(self.tcx.hir().local_def_id(hir_id));
156 intravisit::walk_struct_def(self, v)
158 type Map = intravisit::ErasedMap<'tcx>;
159 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
160 NestedVisitorMap::None
163 tcx.hir().visit_all_item_likes(&mut GatherCtors { tcx, set: &mut set }.as_deep_visitor());
170 body: &mut Body<'tcx>,
172 passes: &[&[&dyn MirPass<'tcx>]],
174 let phase_index = mir_phase.phase_index();
175 let validate = tcx.sess.opts.debugging_opts.validate_mir;
177 if body.phase >= mir_phase {
182 validate::Validator { when: format!("input to phase {:?}", mir_phase), mir_phase }
183 .run_pass(tcx, body);
187 let mut run_pass = |pass: &dyn MirPass<'tcx>| {
188 let run_hooks = |body: &_, index, is_after| {
189 dump_mir::on_mir_pass(
191 &format_args!("{:03}-{:03}", phase_index, index),
197 run_hooks(body, index, false);
198 pass.run_pass(tcx, body);
199 run_hooks(body, index, true);
202 validate::Validator {
203 when: format!("after {} in phase {:?}", pass.name(), mir_phase),
206 .run_pass(tcx, body);
212 for pass_group in passes {
213 for pass in *pass_group {
218 body.phase = mir_phase;
220 if mir_phase == MirPhase::Optimization {
221 validate::Validator { when: format!("end of phase {:?}", mir_phase), mir_phase }
222 .run_pass(tcx, body);
226 fn mir_const_qualif(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> ConstQualifs {
227 let const_kind = tcx.hir().body_const_context(def.did);
229 // No need to const-check a non-const `fn`.
230 if const_kind.is_none() {
231 return Default::default();
234 // N.B., this `borrow()` is guaranteed to be valid (i.e., the value
235 // cannot yet be stolen), because `mir_promoted()`, which steals
236 // from `mir_const(), forces this query to execute before
237 // performing the steal.
238 let body = &tcx.mir_const(def).borrow();
240 if body.return_ty().references_error() {
241 tcx.sess.delay_span_bug(body.span, "mir_const_qualif: MIR had errors");
242 return Default::default();
245 let ccx = check_consts::ConstCx { body, tcx, const_kind, param_env: tcx.param_env(def.did) };
247 let mut validator = check_consts::check::Checker::new(&ccx);
248 validator.check_body();
250 // We return the qualifs in the return place for every MIR body, even though it is only used
251 // when deciding to promote a reference to a `const` for now.
252 validator.qualifs_in_return_place()
255 /// Make MIR ready for const evaluation. This is run on all MIR, not just on consts!
258 def: ty::WithOptConstParam<LocalDefId>,
259 ) -> &'tcx Steal<Body<'tcx>> {
260 if let Some(def) = def.try_upgrade(tcx) {
261 return tcx.mir_const(def);
264 // Unsafety check uses the raw mir, so make sure it is run.
265 if !tcx.sess.opts.debugging_opts.thir_unsafeck {
266 if let Some(param_did) = def.const_param_did {
267 tcx.ensure().unsafety_check_result_for_const_arg((def.did, param_did));
269 tcx.ensure().unsafety_check_result(def.did);
273 let mut body = tcx.mir_built(def).steal();
275 rustc_middle::mir::dump_mir(tcx, None, "mir_map", &0, &body, |_, _| Ok(()));
283 &check_packed_ref::CheckPackedRef,
284 &check_const_item_mutation::CheckConstItemMutation,
285 &function_item_references::FunctionItemReferences,
286 // What we need to do constant evaluation.
287 &simplify::SimplifyCfg::new("initial"),
288 &rustc_peek::SanityCheck,
291 tcx.alloc_steal_mir(body)
294 /// Compute the main MIR body and the list of MIR bodies of the promoteds.
297 def: ty::WithOptConstParam<LocalDefId>,
298 ) -> (&'tcx Steal<Body<'tcx>>, &'tcx Steal<IndexVec<Promoted, Body<'tcx>>>) {
299 if let Some(def) = def.try_upgrade(tcx) {
300 return tcx.mir_promoted(def);
303 // Ensure that we compute the `mir_const_qualif` for constants at
304 // this point, before we steal the mir-const result.
305 // Also this means promotion can rely on all const checks having been done.
306 let _ = tcx.mir_const_qualif_opt_const_arg(def);
307 let mut body = tcx.mir_const(def).steal();
309 let mut required_consts = Vec::new();
310 let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
311 for (bb, bb_data) in traversal::reverse_postorder(&body) {
312 required_consts_visitor.visit_basic_block_data(bb, bb_data);
314 body.required_consts = required_consts;
316 let promote_pass = promote_consts::PromoteTemps::default();
317 let promote: &[&dyn MirPass<'tcx>] = &[
318 // What we need to run borrowck etc.
320 &simplify::SimplifyCfg::new("promote-consts"),
323 let opt_coverage: &[&dyn MirPass<'tcx>] =
324 if tcx.sess.instrument_coverage() { &[&coverage::InstrumentCoverage] } else { &[] };
326 run_passes(tcx, &mut body, MirPhase::ConstPromotion, &[promote, opt_coverage]);
328 let promoted = promote_pass.promoted_fragments.into_inner();
329 (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
332 /// Compute the MIR that is used during CTFE (and thus has no optimizations run on it)
333 fn mir_for_ctfe<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx Body<'tcx> {
334 let did = def_id.expect_local();
335 if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) {
336 tcx.mir_for_ctfe_of_const_arg(def)
338 tcx.arena.alloc(inner_mir_for_ctfe(tcx, ty::WithOptConstParam::unknown(did)))
342 /// Same as `mir_for_ctfe`, but used to get the MIR of a const generic parameter.
343 /// The docs on `WithOptConstParam` explain this a bit more, but the TLDR is that
344 /// we'd get cycle errors with `mir_for_ctfe`, because typeck would need to typeck
345 /// the const parameter while type checking the main body, which in turn would try
346 /// to type check the main body again.
347 fn mir_for_ctfe_of_const_arg<'tcx>(
349 (did, param_did): (LocalDefId, DefId),
350 ) -> &'tcx Body<'tcx> {
351 tcx.arena.alloc(inner_mir_for_ctfe(
353 ty::WithOptConstParam { did, const_param_did: Some(param_did) },
357 fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_> {
358 // FIXME: don't duplicate this between the optimized_mir/mir_for_ctfe queries
359 if tcx.is_constructor(def.did.to_def_id()) {
360 // There's no reason to run all of the MIR passes on constructors when
361 // we can just output the MIR we want directly. This also saves const
362 // qualification and borrow checking the trouble of special casing
364 return shim::build_adt_ctor(tcx, def.did.to_def_id());
369 .body_const_context(def.did)
370 .expect("mir_for_ctfe should not be used for runtime functions");
372 let mut body = tcx.mir_drops_elaborated_and_const_checked(def).borrow().clone();
375 // Do not const prop functions, either they get executed at runtime or exported to metadata,
376 // so we run const prop on them, or they don't, in which case we const evaluate some control
377 // flow paths of the function and any errors in those paths will get emitted as const eval
379 hir::ConstContext::ConstFn => {}
380 // Static items always get evaluated, so we can just let const eval see if any erroneous
381 // control flow paths get executed.
382 hir::ConstContext::Static(_) => {}
383 // Associated constants get const prop run so we detect common failure situations in the
384 // crate that defined the constant.
385 // Technically we want to not run on regular const items, but oli-obk doesn't know how to
386 // conveniently detect that at this point without looking at the HIR.
387 hir::ConstContext::Const => {
389 let optimizations: &[&dyn MirPass<'_>] = &[
390 &const_prop::ConstProp,
397 MirPhase::Optimization,
405 debug_assert!(!body.has_free_regions(tcx), "Free regions in MIR for CTFE");
410 /// Obtain just the main MIR (no promoteds) and run some cleanups on it. This also runs
411 /// mir borrowck *before* doing so in order to ensure that borrowck can be run and doesn't
412 /// end up missing the source MIR due to stealing happening.
413 fn mir_drops_elaborated_and_const_checked<'tcx>(
415 def: ty::WithOptConstParam<LocalDefId>,
416 ) -> &'tcx Steal<Body<'tcx>> {
417 if let Some(def) = def.try_upgrade(tcx) {
418 return tcx.mir_drops_elaborated_and_const_checked(def);
421 // (Mir-)Borrowck uses `mir_promoted`, so we have to force it to
422 // execute before we can steal.
423 if let Some(param_did) = def.const_param_did {
424 tcx.ensure().mir_borrowck_const_arg((def.did, param_did));
426 tcx.ensure().mir_borrowck(def.did);
429 let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
430 use rustc_middle::hir::map::blocks::FnLikeNode;
431 let is_fn_like = FnLikeNode::from_node(tcx.hir().get(hir_id)).is_some();
433 let did = def.did.to_def_id();
434 let def = ty::WithOptConstParam::unknown(did);
436 // Do not compute the mir call graph without said call graph actually being used.
437 if inline::is_enabled(tcx) {
438 let _ = tcx.mir_inliner_callees(ty::InstanceDef::Item(def));
442 let (body, _) = tcx.mir_promoted(def);
443 let mut body = body.steal();
445 run_post_borrowck_cleanup_passes(tcx, &mut body);
446 check_consts::post_drop_elaboration::check_live_drops(tcx, &body);
447 tcx.alloc_steal_mir(body)
450 /// After this series of passes, no lifetime analysis based on borrowing can be done.
451 fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
452 debug!("post_borrowck_cleanup({:?})", body.source.def_id());
454 let post_borrowck_cleanup: &[&dyn MirPass<'tcx>] = &[
455 // Remove all things only needed by analysis
456 &simplify_branches::SimplifyBranches::new("initial"),
457 &remove_noop_landing_pads::RemoveNoopLandingPads,
458 &cleanup_post_borrowck::CleanupNonCodegenStatements,
459 &simplify::SimplifyCfg::new("early-opt"),
460 // These next passes must be executed together
461 &add_call_guards::CriticalCallEdges,
462 &elaborate_drops::ElaborateDrops,
463 // This will remove extraneous landing pads which are no longer
464 // necessary as well as well as forcing any call in a non-unwinding
465 // function calling a possibly-unwinding function to abort the process.
466 &abort_unwinding_calls::AbortUnwindingCalls,
467 // AddMovesForPackedDrops needs to run after drop
469 &add_moves_for_packed_drops::AddMovesForPackedDrops,
470 // `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
471 // but before optimizations begin.
472 &add_retag::AddRetag,
473 &lower_intrinsics::LowerIntrinsics,
474 &simplify::SimplifyCfg::new("elaborate-drops"),
475 // `Deaggregator` is conceptually part of MIR building, some backends rely on it happening
476 // and it can help optimizations.
477 &deaggregator::Deaggregator,
480 run_passes(tcx, body, MirPhase::DropLowering, &[post_borrowck_cleanup]);
483 fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
484 let mir_opt_level = tcx.sess.mir_opt_level();
486 // Lowering generator control-flow and variables has to happen before we do anything else
487 // to them. We run some optimizations before that, because they may be harder to do on the state
488 // machine than on MIR with async primitives.
489 let optimizations_with_generators: &[&dyn MirPass<'tcx>] = &[
490 &lower_slice_len::LowerSliceLenCalls, // has to be done before inlining, otherwise actual call will be almost always inlined. Also simple, so can just do first
491 &unreachable_prop::UnreachablePropagation,
492 &uninhabited_enum_branching::UninhabitedEnumBranching,
493 &simplify::SimplifyCfg::new("after-uninhabited-enum-branching"),
495 &generator::StateTransform,
498 // Even if we don't do optimizations, we still have to lower generators for codegen.
499 let no_optimizations_with_generators: &[&dyn MirPass<'tcx>] = &[&generator::StateTransform];
501 // The main optimizations that we do on MIR.
502 let optimizations: &[&dyn MirPass<'tcx>] = &[
503 &remove_storage_markers::RemoveStorageMarkers,
504 &remove_zsts::RemoveZsts,
505 &const_goto::ConstGoto,
506 &remove_unneeded_drops::RemoveUnneededDrops,
507 &match_branches::MatchBranchSimplification,
508 // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
509 &multiple_return_terminators::MultipleReturnTerminators,
510 &instcombine::InstCombine,
511 &separate_const_switch::SeparateConstSwitch,
512 &const_prop::ConstProp,
513 &simplify_branches::SimplifyBranches::new("after-const-prop"),
514 &early_otherwise_branch::EarlyOtherwiseBranch,
515 &simplify_comparison_integral::SimplifyComparisonIntegral,
516 &simplify_try::SimplifyArmIdentity,
517 &simplify_try::SimplifyBranchSame,
518 &dest_prop::DestinationPropagation,
519 &simplify_branches::SimplifyBranches::new("final"),
520 &remove_noop_landing_pads::RemoveNoopLandingPads,
521 &simplify::SimplifyCfg::new("final"),
522 &nrvo::RenameReturnPlace,
523 &const_debuginfo::ConstDebugInfo,
524 &simplify::SimplifyLocals,
525 &multiple_return_terminators::MultipleReturnTerminators,
526 &deduplicate_blocks::DeduplicateBlocks,
529 // Optimizations to run even if mir optimizations have been disabled.
530 let no_optimizations: &[&dyn MirPass<'tcx>] = &[
531 // FIXME(#70073): This pass is responsible for both optimization as well as some lints.
532 &const_prop::ConstProp,
535 // Some cleanup necessary at least for LLVM and potentially other codegen backends.
536 let pre_codegen_cleanup: &[&dyn MirPass<'tcx>] = &[
537 &add_call_guards::CriticalCallEdges,
538 // Dump the end result for testing and debugging purposes.
539 &dump_mir::Marker("PreCodegen"),
542 // End of pass declarations, now actually run the passes.
543 // Generator Lowering
548 MirPhase::GeneratorLowering,
550 if mir_opt_level > 0 {
551 optimizations_with_generators
553 no_optimizations_with_generators
558 // Main optimization passes
563 MirPhase::Optimization,
565 if mir_opt_level > 0 { optimizations } else { no_optimizations },
571 /// Optimize the MIR and prepare it for codegen.
572 fn optimized_mir<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx Body<'tcx> {
573 let did = did.expect_local();
574 assert_eq!(ty::WithOptConstParam::try_lookup(did, tcx), None);
575 tcx.arena.alloc(inner_optimized_mir(tcx, did))
578 fn inner_optimized_mir(tcx: TyCtxt<'_>, did: LocalDefId) -> Body<'_> {
579 if tcx.is_constructor(did.to_def_id()) {
580 // There's no reason to run all of the MIR passes on constructors when
581 // we can just output the MIR we want directly. This also saves const
582 // qualification and borrow checking the trouble of special casing
584 return shim::build_adt_ctor(tcx, did.to_def_id());
587 match tcx.hir().body_const_context(did) {
588 // Run the `mir_for_ctfe` query, which depends on `mir_drops_elaborated_and_const_checked`
589 // which we are going to steal below. Thus we need to run `mir_for_ctfe` first, so it
590 // computes and caches its result.
591 Some(hir::ConstContext::ConstFn) => tcx.ensure().mir_for_ctfe(did),
593 Some(other) => panic!("do not use `optimized_mir` for constants: {:?}", other),
596 tcx.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(did)).steal();
597 run_optimization_passes(tcx, &mut body);
599 debug_assert!(!body.has_free_regions(tcx), "Free regions in optimized MIR");
604 /// Fetch all the promoteds of an item and prepare their MIR bodies to be ready for
605 /// constant evaluation once all substitutions become known.
606 fn promoted_mir<'tcx>(
608 def: ty::WithOptConstParam<LocalDefId>,
609 ) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
610 if tcx.is_constructor(def.did.to_def_id()) {
611 return tcx.arena.alloc(IndexVec::new());
614 if let Some(param_did) = def.const_param_did {
615 tcx.ensure().mir_borrowck_const_arg((def.did, param_did));
617 tcx.ensure().mir_borrowck(def.did);
619 let (_, promoted) = tcx.mir_promoted(def);
620 let mut promoted = promoted.steal();
622 for body in &mut promoted {
623 run_post_borrowck_cleanup_passes(tcx, body);
626 debug_assert!(!promoted.has_free_regions(tcx), "Free regions in promoted MIR");
628 tcx.arena.alloc(promoted)