1 use crate::{shim, util};
2 use required_consts::RequiredConstsVisitor;
3 use rustc_data_structures::fx::FxHashSet;
4 use rustc_data_structures::steal::Steal;
6 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
7 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
8 use rustc_index::vec::IndexVec;
9 use rustc_middle::mir::visit::Visitor as _;
10 use rustc_middle::mir::{traversal, Body, ConstQualifs, MirPhase, Promoted};
11 use rustc_middle::ty::query::Providers;
12 use rustc_middle::ty::{self, TyCtxt, TypeFoldable};
13 use rustc_span::{Span, Symbol};
16 pub mod add_call_guards;
17 pub mod add_moves_for_packed_drops;
19 pub mod check_const_item_mutation;
21 pub mod check_packed_ref;
22 pub mod check_unsafety;
23 pub mod cleanup_post_borrowck;
24 pub mod const_debuginfo;
29 pub mod deduplicate_blocks;
32 pub mod early_otherwise_branch;
33 pub mod elaborate_drops;
34 pub mod function_item_references;
38 pub mod lower_intrinsics;
39 pub mod match_branches;
40 pub mod multiple_return_terminators;
41 pub mod no_landing_pads;
43 pub mod promote_consts;
44 pub mod remove_noop_landing_pads;
45 pub mod remove_storage_markers;
46 pub mod remove_unneeded_drops;
48 pub mod required_consts;
51 pub mod simplify_branches;
52 pub mod simplify_comparison_integral;
54 pub mod uninhabited_enum_branching;
55 pub mod unreachable_prop;
58 pub use rustc_middle::mir::MirSource;
60 pub(crate) fn provide(providers: &mut Providers) {
61 self::check_unsafety::provide(providers);
62 *providers = Providers {
65 mir_const_qualif: |tcx, def_id| {
66 let def_id = def_id.expect_local();
67 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
68 tcx.mir_const_qualif_const_arg(def)
70 mir_const_qualif(tcx, ty::WithOptConstParam::unknown(def_id))
73 mir_const_qualif_const_arg: |tcx, (did, param_did)| {
74 mir_const_qualif(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
77 mir_drops_elaborated_and_const_checked,
79 mir_for_ctfe_of_const_arg,
82 is_ctfe_mir_available: |tcx, did| is_mir_available(tcx, did),
83 promoted_mir: |tcx, def_id| {
84 let def_id = def_id.expect_local();
85 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
86 tcx.promoted_mir_of_const_arg(def)
88 promoted_mir(tcx, ty::WithOptConstParam::unknown(def_id))
91 promoted_mir_of_const_arg: |tcx, (did, param_did)| {
92 promoted_mir(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
96 coverage::query::provide(providers);
99 fn is_mir_available(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
100 tcx.mir_keys(def_id.krate).contains(&def_id.expect_local())
103 /// Finds the full set of `DefId`s within the current crate that have
104 /// MIR associated with them.
105 fn mir_keys(tcx: TyCtxt<'_>, krate: CrateNum) -> FxHashSet<LocalDefId> {
106 assert_eq!(krate, LOCAL_CRATE);
108 let mut set = FxHashSet::default();
110 // All body-owners have MIR associated with them.
111 set.extend(tcx.body_owners());
113 // Additionally, tuple struct/variant constructors have MIR, but
114 // they don't have a BodyId, so we need to build them separately.
115 struct GatherCtors<'a, 'tcx> {
117 set: &'a mut FxHashSet<LocalDefId>,
119 impl<'a, 'tcx> Visitor<'tcx> for GatherCtors<'a, 'tcx> {
120 fn visit_variant_data(
122 v: &'tcx hir::VariantData<'tcx>,
124 _: &'tcx hir::Generics<'tcx>,
128 if let hir::VariantData::Tuple(_, hir_id) = *v {
129 self.set.insert(self.tcx.hir().local_def_id(hir_id));
131 intravisit::walk_struct_def(self, v)
133 type Map = intravisit::ErasedMap<'tcx>;
134 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
135 NestedVisitorMap::None
140 .visit_all_item_likes(&mut GatherCtors { tcx, set: &mut set }.as_deep_visitor());
145 /// Generates a default name for the pass based on the name of the
147 pub fn default_name<T: ?Sized>() -> Cow<'static, str> {
148 let name = std::any::type_name::<T>();
149 if let Some(tail) = name.rfind(':') { Cow::from(&name[tail + 1..]) } else { Cow::from(name) }
152 /// A streamlined trait that you can implement to create a pass; the
153 /// pass will be named after the type, and it will consist of a main
154 /// loop that goes over each available MIR and applies `run_pass`.
155 pub trait MirPass<'tcx> {
156 fn name(&self) -> Cow<'_, str> {
157 default_name::<Self>()
160 fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>);
165 body: &mut Body<'tcx>,
167 passes: &[&[&dyn MirPass<'tcx>]],
169 let phase_index = mir_phase.phase_index();
170 let validate = tcx.sess.opts.debugging_opts.validate_mir;
172 if body.phase >= mir_phase {
177 validate::Validator { when: format!("input to phase {:?}", mir_phase), mir_phase }
178 .run_pass(tcx, body);
182 let mut run_pass = |pass: &dyn MirPass<'tcx>| {
183 let run_hooks = |body: &_, index, is_after| {
184 dump_mir::on_mir_pass(
186 &format_args!("{:03}-{:03}", phase_index, index),
192 run_hooks(body, index, false);
193 pass.run_pass(tcx, body);
194 run_hooks(body, index, true);
197 validate::Validator {
198 when: format!("after {} in phase {:?}", pass.name(), mir_phase),
201 .run_pass(tcx, body);
207 for pass_group in passes {
208 for pass in *pass_group {
213 body.phase = mir_phase;
215 if mir_phase == MirPhase::Optimization {
216 validate::Validator { when: format!("end of phase {:?}", mir_phase), mir_phase }
217 .run_pass(tcx, body);
221 fn mir_const_qualif(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> ConstQualifs {
222 let const_kind = tcx.hir().body_const_context(def.did);
224 // No need to const-check a non-const `fn`.
225 if const_kind.is_none() {
226 return Default::default();
229 // N.B., this `borrow()` is guaranteed to be valid (i.e., the value
230 // cannot yet be stolen), because `mir_promoted()`, which steals
231 // from `mir_const(), forces this query to execute before
232 // performing the steal.
233 let body = &tcx.mir_const(def).borrow();
235 if body.return_ty().references_error() {
236 tcx.sess.delay_span_bug(body.span, "mir_const_qualif: MIR had errors");
237 return Default::default();
240 let ccx = check_consts::ConstCx { body, tcx, const_kind, param_env: tcx.param_env(def.did) };
242 let mut validator = check_consts::validation::Validator::new(&ccx);
243 validator.check_body();
245 // We return the qualifs in the return place for every MIR body, even though it is only used
246 // when deciding to promote a reference to a `const` for now.
247 validator.qualifs_in_return_place()
250 /// Make MIR ready for const evaluation. This is run on all MIR, not just on consts!
253 def: ty::WithOptConstParam<LocalDefId>,
254 ) -> &'tcx Steal<Body<'tcx>> {
255 if let Some(def) = def.try_upgrade(tcx) {
256 return tcx.mir_const(def);
259 // Unsafety check uses the raw mir, so make sure it is run.
260 if let Some(param_did) = def.const_param_did {
261 tcx.ensure().unsafety_check_result_for_const_arg((def.did, param_did));
263 tcx.ensure().unsafety_check_result(def.did);
266 let mut body = tcx.mir_built(def).steal();
268 util::dump_mir(tcx, None, "mir_map", &0, &body, |_, _| Ok(()));
276 &check_packed_ref::CheckPackedRef,
277 &check_const_item_mutation::CheckConstItemMutation,
278 &function_item_references::FunctionItemReferences,
279 // What we need to do constant evaluation.
280 &simplify::SimplifyCfg::new("initial"),
281 &rustc_peek::SanityCheck,
284 tcx.alloc_steal_mir(body)
287 /// Compute the main MIR body and the list of MIR bodies of the promoteds.
290 def: ty::WithOptConstParam<LocalDefId>,
291 ) -> (&'tcx Steal<Body<'tcx>>, &'tcx Steal<IndexVec<Promoted, Body<'tcx>>>) {
292 if let Some(def) = def.try_upgrade(tcx) {
293 return tcx.mir_promoted(def);
296 // Ensure that we compute the `mir_const_qualif` for constants at
297 // this point, before we steal the mir-const result.
298 // Also this means promotion can rely on all const checks having been done.
299 let _ = tcx.mir_const_qualif_opt_const_arg(def);
300 let _ = tcx.mir_abstract_const_opt_const_arg(def.to_global());
301 let mut body = tcx.mir_const(def).steal();
303 let mut required_consts = Vec::new();
304 let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
305 for (bb, bb_data) in traversal::reverse_postorder(&body) {
306 required_consts_visitor.visit_basic_block_data(bb, bb_data);
308 body.required_consts = required_consts;
310 let promote_pass = promote_consts::PromoteTemps::default();
311 let promote: &[&dyn MirPass<'tcx>] = &[
312 // What we need to run borrowck etc.
314 &simplify::SimplifyCfg::new("promote-consts"),
317 let opt_coverage: &[&dyn MirPass<'tcx>] = if tcx.sess.opts.debugging_opts.instrument_coverage {
318 &[&coverage::InstrumentCoverage]
323 run_passes(tcx, &mut body, MirPhase::ConstPromotion, &[promote, opt_coverage]);
325 let promoted = promote_pass.promoted_fragments.into_inner();
326 (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
329 /// Compute the MIR that is used during CTFE (and thus has no optimizations run on it)
330 fn mir_for_ctfe<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx Body<'tcx> {
331 let did = def_id.expect_local();
332 if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) {
333 tcx.mir_for_ctfe_of_const_arg(def)
335 tcx.arena.alloc(inner_mir_for_ctfe(tcx, ty::WithOptConstParam::unknown(did)))
339 /// Same as `mir_for_ctfe`, but used to get the MIR of a const generic parameter.
340 /// The docs on `WithOptConstParam` explain this a bit more, but the TLDR is that
341 /// we'd get cycle errors with `mir_for_ctfe`, because typeck would need to typeck
342 /// the const parameter while type checking the main body, which in turn would try
343 /// to type check the main body again.
344 fn mir_for_ctfe_of_const_arg<'tcx>(
346 (did, param_did): (LocalDefId, DefId),
347 ) -> &'tcx Body<'tcx> {
348 tcx.arena.alloc(inner_mir_for_ctfe(
350 ty::WithOptConstParam { did, const_param_did: Some(param_did) },
354 fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_> {
355 // FIXME: don't duplicate this between the optimized_mir/mir_for_ctfe queries
356 if tcx.is_constructor(def.did.to_def_id()) {
357 // There's no reason to run all of the MIR passes on constructors when
358 // we can just output the MIR we want directly. This also saves const
359 // qualification and borrow checking the trouble of special casing
361 return shim::build_adt_ctor(tcx, def.did.to_def_id());
366 .body_const_context(def.did)
367 .expect("mir_for_ctfe should not be used for runtime functions");
369 let mut body = tcx.mir_drops_elaborated_and_const_checked(def).borrow().clone();
372 // Do not const prop functions, either they get executed at runtime or exported to metadata,
373 // so we run const prop on them, or they don't, in which case we const evaluate some control
374 // flow paths of the function and any errors in those paths will get emitted as const eval
376 hir::ConstContext::ConstFn => {}
377 // Static items always get evaluated, so we can just let const eval see if any erroneous
378 // control flow paths get executed.
379 hir::ConstContext::Static(_) => {}
380 // Associated constants get const prop run so we detect common failure situations in the
381 // crate that defined the constant.
382 // Technically we want to not run on regular const items, but oli-obk doesn't know how to
383 // conveniently detect that at this point without looking at the HIR.
384 hir::ConstContext::Const => {
386 let optimizations: &[&dyn MirPass<'_>] = &[
387 &const_prop::ConstProp,
394 MirPhase::Optimization,
402 debug_assert!(!body.has_free_regions(), "Free regions in MIR for CTFE");
407 /// Obtain just the main MIR (no promoteds) and run some cleanups on it. This also runs
408 /// mir borrowck *before* doing so in order to ensure that borrowck can be run and doesn't
409 /// end up missing the source MIR due to stealing happening.
410 fn mir_drops_elaborated_and_const_checked<'tcx>(
412 def: ty::WithOptConstParam<LocalDefId>,
413 ) -> &'tcx Steal<Body<'tcx>> {
414 if let Some(def) = def.try_upgrade(tcx) {
415 return tcx.mir_drops_elaborated_and_const_checked(def);
418 // (Mir-)Borrowck uses `mir_promoted`, so we have to force it to
419 // execute before we can steal.
420 if let Some(param_did) = def.const_param_did {
421 tcx.ensure().mir_borrowck_const_arg((def.did, param_did));
423 tcx.ensure().mir_borrowck(def.did);
426 let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
427 use rustc_middle::hir::map::blocks::FnLikeNode;
428 let is_fn_like = FnLikeNode::from_node(tcx.hir().get(hir_id)).is_some();
430 let did = def.did.to_def_id();
431 let def = ty::WithOptConstParam::unknown(did);
433 // Do not compute the mir call graph without said call graph actually being used.
434 if inline::is_enabled(tcx) {
435 let _ = tcx.mir_inliner_callees(ty::InstanceDef::Item(def));
439 let (body, _) = tcx.mir_promoted(def);
440 let mut body = body.steal();
442 run_post_borrowck_cleanup_passes(tcx, &mut body);
443 check_consts::post_drop_elaboration::check_live_drops(tcx, &body);
444 tcx.alloc_steal_mir(body)
447 /// After this series of passes, no lifetime analysis based on borrowing can be done.
448 fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
449 debug!("post_borrowck_cleanup({:?})", body.source.def_id());
451 let post_borrowck_cleanup: &[&dyn MirPass<'tcx>] = &[
452 // Remove all things only needed by analysis
453 &no_landing_pads::NoLandingPads,
454 &simplify_branches::SimplifyBranches::new("initial"),
455 &remove_noop_landing_pads::RemoveNoopLandingPads,
456 &cleanup_post_borrowck::CleanupNonCodegenStatements,
457 &simplify::SimplifyCfg::new("early-opt"),
458 // These next passes must be executed together
459 &add_call_guards::CriticalCallEdges,
460 &elaborate_drops::ElaborateDrops,
461 &no_landing_pads::NoLandingPads,
462 // AddMovesForPackedDrops needs to run after drop
464 &add_moves_for_packed_drops::AddMovesForPackedDrops,
465 // `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
466 // but before optimizations begin.
467 &add_retag::AddRetag,
468 &lower_intrinsics::LowerIntrinsics,
469 &simplify::SimplifyCfg::new("elaborate-drops"),
470 // `Deaggregator` is conceptually part of MIR building, some backends rely on it happening
471 // and it can help optimizations.
472 &deaggregator::Deaggregator,
475 run_passes(tcx, body, MirPhase::DropLowering, &[post_borrowck_cleanup]);
478 fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
479 let mir_opt_level = tcx.sess.mir_opt_level();
481 // Lowering generator control-flow and variables has to happen before we do anything else
482 // to them. We run some optimizations before that, because they may be harder to do on the state
483 // machine than on MIR with async primitives.
484 let optimizations_with_generators: &[&dyn MirPass<'tcx>] = &[
485 &unreachable_prop::UnreachablePropagation,
486 &uninhabited_enum_branching::UninhabitedEnumBranching,
487 &simplify::SimplifyCfg::new("after-uninhabited-enum-branching"),
489 &generator::StateTransform,
492 // Even if we don't do optimizations, we still have to lower generators for codegen.
493 let no_optimizations_with_generators: &[&dyn MirPass<'tcx>] = &[&generator::StateTransform];
495 // The main optimizations that we do on MIR.
496 let optimizations: &[&dyn MirPass<'tcx>] = &[
497 &remove_storage_markers::RemoveStorageMarkers,
498 &remove_zsts::RemoveZsts,
499 &const_goto::ConstGoto,
500 &remove_unneeded_drops::RemoveUnneededDrops,
501 &match_branches::MatchBranchSimplification,
502 // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
503 &multiple_return_terminators::MultipleReturnTerminators,
504 &instcombine::InstCombine,
505 &const_prop::ConstProp,
506 &simplify_branches::SimplifyBranches::new("after-const-prop"),
507 &early_otherwise_branch::EarlyOtherwiseBranch,
508 &simplify_comparison_integral::SimplifyComparisonIntegral,
509 &simplify_try::SimplifyArmIdentity,
510 &simplify_try::SimplifyBranchSame,
511 &dest_prop::DestinationPropagation,
512 &simplify_branches::SimplifyBranches::new("final"),
513 &remove_noop_landing_pads::RemoveNoopLandingPads,
514 &simplify::SimplifyCfg::new("final"),
515 &nrvo::RenameReturnPlace,
516 &const_debuginfo::ConstDebugInfo,
517 &simplify::SimplifyLocals,
518 &multiple_return_terminators::MultipleReturnTerminators,
519 &deduplicate_blocks::DeduplicateBlocks,
522 // Optimizations to run even if mir optimizations have been disabled.
523 let no_optimizations: &[&dyn MirPass<'tcx>] = &[
524 // FIXME(#70073): This pass is responsible for both optimization as well as some lints.
525 &const_prop::ConstProp,
528 // Some cleanup necessary at least for LLVM and potentially other codegen backends.
529 let pre_codegen_cleanup: &[&dyn MirPass<'tcx>] = &[
530 &add_call_guards::CriticalCallEdges,
531 // Dump the end result for testing and debugging purposes.
532 &dump_mir::Marker("PreCodegen"),
535 // End of pass declarations, now actually run the passes.
536 // Generator Lowering
541 MirPhase::GeneratorLowering,
543 if mir_opt_level > 0 {
544 optimizations_with_generators
546 no_optimizations_with_generators
551 // Main optimization passes
556 MirPhase::Optimization,
558 if mir_opt_level > 0 { optimizations } else { no_optimizations },
564 /// Optimize the MIR and prepare it for codegen.
565 fn optimized_mir<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx Body<'tcx> {
566 let did = did.expect_local();
567 assert_eq!(ty::WithOptConstParam::try_lookup(did, tcx), None);
568 tcx.arena.alloc(inner_optimized_mir(tcx, did))
571 fn inner_optimized_mir(tcx: TyCtxt<'_>, did: LocalDefId) -> Body<'_> {
572 if tcx.is_constructor(did.to_def_id()) {
573 // There's no reason to run all of the MIR passes on constructors when
574 // we can just output the MIR we want directly. This also saves const
575 // qualification and borrow checking the trouble of special casing
577 return shim::build_adt_ctor(tcx, did.to_def_id());
580 match tcx.hir().body_const_context(did) {
581 // Run the `mir_for_ctfe` query, which depends on `mir_drops_elaborated_and_const_checked`
582 // which we are going to steal below. Thus we need to run `mir_for_ctfe` first, so it
583 // computes and caches its result.
584 Some(hir::ConstContext::ConstFn) => tcx.ensure().mir_for_ctfe(did),
586 Some(other) => panic!("do not use `optimized_mir` for constants: {:?}", other),
589 tcx.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(did)).steal();
590 run_optimization_passes(tcx, &mut body);
592 debug_assert!(!body.has_free_regions(), "Free regions in optimized MIR");
597 /// Fetch all the promoteds of an item and prepare their MIR bodies to be ready for
598 /// constant evaluation once all substitutions become known.
599 fn promoted_mir<'tcx>(
601 def: ty::WithOptConstParam<LocalDefId>,
602 ) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
603 if tcx.is_constructor(def.did.to_def_id()) {
604 return tcx.arena.alloc(IndexVec::new());
607 if let Some(param_did) = def.const_param_did {
608 tcx.ensure().mir_borrowck_const_arg((def.did, param_did));
610 tcx.ensure().mir_borrowck(def.did);
612 let (_, promoted) = tcx.mir_promoted(def);
613 let mut promoted = promoted.steal();
615 for body in &mut promoted {
616 run_post_borrowck_cleanup_passes(tcx, body);
619 debug_assert!(!promoted.has_free_regions(), "Free regions in promoted MIR");
621 tcx.arena.alloc(promoted)