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;
30 pub mod early_otherwise_branch;
31 pub mod elaborate_drops;
32 pub mod function_item_references;
36 pub mod lower_intrinsics;
37 pub mod match_branches;
38 pub mod multiple_return_terminators;
39 pub mod no_landing_pads;
41 pub mod promote_consts;
42 pub mod remove_noop_landing_pads;
43 pub mod remove_unneeded_drops;
44 pub mod required_consts;
47 pub mod simplify_branches;
48 pub mod simplify_comparison_integral;
50 pub mod uninhabited_enum_branching;
51 pub mod unreachable_prop;
54 pub use rustc_middle::mir::MirSource;
56 pub(crate) fn provide(providers: &mut Providers) {
57 self::check_unsafety::provide(providers);
58 *providers = Providers {
61 mir_const_qualif: |tcx, def_id| {
62 let def_id = def_id.expect_local();
63 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
64 tcx.mir_const_qualif_const_arg(def)
66 mir_const_qualif(tcx, ty::WithOptConstParam::unknown(def_id))
69 mir_const_qualif_const_arg: |tcx, (did, param_did)| {
70 mir_const_qualif(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
73 mir_drops_elaborated_and_const_checked,
75 mir_for_ctfe_of_const_arg,
78 is_ctfe_mir_available: |tcx, did| is_mir_available(tcx, did),
79 promoted_mir: |tcx, def_id| {
80 let def_id = def_id.expect_local();
81 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
82 tcx.promoted_mir_of_const_arg(def)
84 promoted_mir(tcx, ty::WithOptConstParam::unknown(def_id))
87 promoted_mir_of_const_arg: |tcx, (did, param_did)| {
88 promoted_mir(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
92 coverage::query::provide(providers);
95 fn is_mir_available(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
96 tcx.mir_keys(def_id.krate).contains(&def_id.expect_local())
99 /// Finds the full set of `DefId`s within the current crate that have
100 /// MIR associated with them.
101 fn mir_keys(tcx: TyCtxt<'_>, krate: CrateNum) -> FxHashSet<LocalDefId> {
102 assert_eq!(krate, LOCAL_CRATE);
104 let mut set = FxHashSet::default();
106 // All body-owners have MIR associated with them.
107 set.extend(tcx.body_owners());
109 // Additionally, tuple struct/variant constructors have MIR, but
110 // they don't have a BodyId, so we need to build them separately.
111 struct GatherCtors<'a, 'tcx> {
113 set: &'a mut FxHashSet<LocalDefId>,
115 impl<'a, 'tcx> Visitor<'tcx> for GatherCtors<'a, 'tcx> {
116 fn visit_variant_data(
118 v: &'tcx hir::VariantData<'tcx>,
120 _: &'tcx hir::Generics<'tcx>,
124 if let hir::VariantData::Tuple(_, hir_id) = *v {
125 self.set.insert(self.tcx.hir().local_def_id(hir_id));
127 intravisit::walk_struct_def(self, v)
129 type Map = intravisit::ErasedMap<'tcx>;
130 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
131 NestedVisitorMap::None
136 .visit_all_item_likes(&mut GatherCtors { tcx, set: &mut set }.as_deep_visitor());
141 /// Generates a default name for the pass based on the name of the
143 pub fn default_name<T: ?Sized>() -> Cow<'static, str> {
144 let name = std::any::type_name::<T>();
145 if let Some(tail) = name.rfind(':') { Cow::from(&name[tail + 1..]) } else { Cow::from(name) }
148 /// A streamlined trait that you can implement to create a pass; the
149 /// pass will be named after the type, and it will consist of a main
150 /// loop that goes over each available MIR and applies `run_pass`.
151 pub trait MirPass<'tcx> {
152 fn name(&self) -> Cow<'_, str> {
153 default_name::<Self>()
156 fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>);
161 body: &mut Body<'tcx>,
163 passes: &[&[&dyn MirPass<'tcx>]],
165 let phase_index = mir_phase.phase_index();
166 let validate = tcx.sess.opts.debugging_opts.validate_mir;
168 if body.phase >= mir_phase {
173 validate::Validator { when: format!("input to phase {:?}", mir_phase), mir_phase }
174 .run_pass(tcx, body);
178 let mut run_pass = |pass: &dyn MirPass<'tcx>| {
179 let run_hooks = |body: &_, index, is_after| {
180 dump_mir::on_mir_pass(
182 &format_args!("{:03}-{:03}", phase_index, index),
188 run_hooks(body, index, false);
189 pass.run_pass(tcx, body);
190 run_hooks(body, index, true);
193 validate::Validator {
194 when: format!("after {} in phase {:?}", pass.name(), mir_phase),
197 .run_pass(tcx, body);
203 for pass_group in passes {
204 for pass in *pass_group {
209 body.phase = mir_phase;
211 if mir_phase == MirPhase::Optimization {
212 validate::Validator { when: format!("end of phase {:?}", mir_phase), mir_phase }
213 .run_pass(tcx, body);
217 fn mir_const_qualif(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> ConstQualifs {
218 let const_kind = tcx.hir().body_const_context(def.did);
220 // No need to const-check a non-const `fn`.
221 if const_kind.is_none() {
222 return Default::default();
225 // N.B., this `borrow()` is guaranteed to be valid (i.e., the value
226 // cannot yet be stolen), because `mir_promoted()`, which steals
227 // from `mir_const(), forces this query to execute before
228 // performing the steal.
229 let body = &tcx.mir_const(def).borrow();
231 if body.return_ty().references_error() {
232 tcx.sess.delay_span_bug(body.span, "mir_const_qualif: MIR had errors");
233 return Default::default();
236 let ccx = check_consts::ConstCx { body, tcx, const_kind, param_env: tcx.param_env(def.did) };
238 let mut validator = check_consts::validation::Validator::new(&ccx);
239 validator.check_body();
241 // We return the qualifs in the return place for every MIR body, even though it is only used
242 // when deciding to promote a reference to a `const` for now.
243 validator.qualifs_in_return_place()
246 /// Make MIR ready for const evaluation. This is run on all MIR, not just on consts!
249 def: ty::WithOptConstParam<LocalDefId>,
250 ) -> &'tcx Steal<Body<'tcx>> {
251 if let Some(def) = def.try_upgrade(tcx) {
252 return tcx.mir_const(def);
255 // Unsafety check uses the raw mir, so make sure it is run.
256 if let Some(param_did) = def.const_param_did {
257 tcx.ensure().unsafety_check_result_for_const_arg((def.did, param_did));
259 tcx.ensure().unsafety_check_result(def.did);
262 let mut body = tcx.mir_built(def).steal();
264 util::dump_mir(tcx, None, "mir_map", &0, &body, |_, _| Ok(()));
272 &check_packed_ref::CheckPackedRef,
273 &check_const_item_mutation::CheckConstItemMutation,
274 &function_item_references::FunctionItemReferences,
275 // What we need to do constant evaluation.
276 &simplify::SimplifyCfg::new("initial"),
277 &rustc_peek::SanityCheck,
280 tcx.alloc_steal_mir(body)
283 /// Compute the main MIR body and the list of MIR bodies of the promoteds.
286 def: ty::WithOptConstParam<LocalDefId>,
287 ) -> (&'tcx Steal<Body<'tcx>>, &'tcx Steal<IndexVec<Promoted, Body<'tcx>>>) {
288 if let Some(def) = def.try_upgrade(tcx) {
289 return tcx.mir_promoted(def);
292 // Ensure that we compute the `mir_const_qualif` for constants at
293 // this point, before we steal the mir-const result.
294 // Also this means promotion can rely on all const checks having been done.
295 let _ = tcx.mir_const_qualif_opt_const_arg(def);
296 let _ = tcx.mir_abstract_const_opt_const_arg(def.to_global());
297 let mut body = tcx.mir_const(def).steal();
299 let mut required_consts = Vec::new();
300 let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
301 for (bb, bb_data) in traversal::reverse_postorder(&body) {
302 required_consts_visitor.visit_basic_block_data(bb, bb_data);
304 body.required_consts = required_consts;
306 let promote_pass = promote_consts::PromoteTemps::default();
307 let promote: &[&dyn MirPass<'tcx>] = &[
308 // What we need to run borrowck etc.
310 &simplify::SimplifyCfg::new("promote-consts"),
313 let opt_coverage: &[&dyn MirPass<'tcx>] = if tcx.sess.opts.debugging_opts.instrument_coverage {
314 &[&coverage::InstrumentCoverage]
319 run_passes(tcx, &mut body, MirPhase::ConstPromotion, &[promote, opt_coverage]);
321 let promoted = promote_pass.promoted_fragments.into_inner();
322 (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
325 /// Compute the MIR that is used during CTFE (and thus has no optimizations run on it)
326 fn mir_for_ctfe<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx Body<'tcx> {
327 let did = def_id.expect_local();
328 if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) {
329 tcx.mir_for_ctfe_of_const_arg(def)
331 tcx.arena.alloc(inner_mir_for_ctfe(tcx, ty::WithOptConstParam::unknown(did)))
335 /// Same as `mir_for_ctfe`, but used to get the MIR of a const generic parameter.
336 /// The docs on `WithOptConstParam` explain this a bit more, but the TLDR is that
337 /// we'd get cycle errors with `mir_for_ctfe`, because typeck would need to typeck
338 /// the const parameter while type checking the main body, which in turn would try
339 /// to type check the main body again.
340 fn mir_for_ctfe_of_const_arg<'tcx>(
342 (did, param_did): (LocalDefId, DefId),
343 ) -> &'tcx Body<'tcx> {
344 tcx.arena.alloc(inner_mir_for_ctfe(
346 ty::WithOptConstParam { did, const_param_did: Some(param_did) },
350 fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_> {
351 // FIXME: don't duplicate this between the optimized_mir/mir_for_ctfe queries
352 if tcx.is_constructor(def.did.to_def_id()) {
353 // There's no reason to run all of the MIR passes on constructors when
354 // we can just output the MIR we want directly. This also saves const
355 // qualification and borrow checking the trouble of special casing
357 return shim::build_adt_ctor(tcx, def.did.to_def_id());
362 .body_const_context(def.did)
363 .expect("mir_for_ctfe should not be used for runtime functions");
365 let mut body = tcx.mir_drops_elaborated_and_const_checked(def).borrow().clone();
368 // Do not const prop functions, either they get executed at runtime or exported to metadata,
369 // so we run const prop on them, or they don't, in which case we const evaluate some control
370 // flow paths of the function and any errors in those paths will get emitted as const eval
372 hir::ConstContext::ConstFn => {}
373 // Static items always get evaluated, so we can just let const eval see if any erroneous
374 // control flow paths get executed.
375 hir::ConstContext::Static(_) => {}
376 // Associated constants get const prop run so we detect common failure situations in the
377 // crate that defined the constant.
378 // Technically we want to not run on regular const items, but oli-obk doesn't know how to
379 // conveniently detect that at this point without looking at the HIR.
380 hir::ConstContext::Const => {
382 let optimizations: &[&dyn MirPass<'_>] = &[
383 &const_prop::ConstProp,
390 MirPhase::Optimization,
398 debug_assert!(!body.has_free_regions(), "Free regions in MIR for CTFE");
403 /// Obtain just the main MIR (no promoteds) and run some cleanups on it. This also runs
404 /// mir borrowck *before* doing so in order to ensure that borrowck can be run and doesn't
405 /// end up missing the source MIR due to stealing happening.
406 fn mir_drops_elaborated_and_const_checked<'tcx>(
408 def: ty::WithOptConstParam<LocalDefId>,
409 ) -> &'tcx Steal<Body<'tcx>> {
410 if let Some(def) = def.try_upgrade(tcx) {
411 return tcx.mir_drops_elaborated_and_const_checked(def);
414 // (Mir-)Borrowck uses `mir_promoted`, so we have to force it to
415 // execute before we can steal.
416 if let Some(param_did) = def.const_param_did {
417 tcx.ensure().mir_borrowck_const_arg((def.did, param_did));
419 tcx.ensure().mir_borrowck(def.did);
422 let hir_id = tcx.hir().local_def_id_to_hir_id(def.did);
423 use rustc_middle::hir::map::blocks::FnLikeNode;
424 let is_fn_like = FnLikeNode::from_node(tcx.hir().get(hir_id)).is_some();
426 let did = def.did.to_def_id();
427 let def = ty::WithOptConstParam::unknown(did);
429 // Do not compute the mir call graph without said call graph actually being used.
430 // Keep this in sync with the mir inliner's optimization level.
431 if tcx.sess.opts.debugging_opts.mir_opt_level >= 2 {
432 let _ = tcx.mir_inliner_callees(ty::InstanceDef::Item(def));
436 let (body, _) = tcx.mir_promoted(def);
437 let mut body = body.steal();
439 run_post_borrowck_cleanup_passes(tcx, &mut body);
440 check_consts::post_drop_elaboration::check_live_drops(tcx, &body);
441 tcx.alloc_steal_mir(body)
444 /// After this series of passes, no lifetime analysis based on borrowing can be done.
445 fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
446 debug!("post_borrowck_cleanup({:?})", body.source.def_id());
448 let post_borrowck_cleanup: &[&dyn MirPass<'tcx>] = &[
449 // Remove all things only needed by analysis
450 &no_landing_pads::NoLandingPads,
451 &simplify_branches::SimplifyBranches::new("initial"),
452 &remove_noop_landing_pads::RemoveNoopLandingPads,
453 &cleanup_post_borrowck::CleanupNonCodegenStatements,
454 &simplify::SimplifyCfg::new("early-opt"),
455 // These next passes must be executed together
456 &add_call_guards::CriticalCallEdges,
457 &elaborate_drops::ElaborateDrops,
458 &no_landing_pads::NoLandingPads,
459 // AddMovesForPackedDrops needs to run after drop
461 &add_moves_for_packed_drops::AddMovesForPackedDrops,
462 // `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
463 // but before optimizations begin.
464 &add_retag::AddRetag,
465 &lower_intrinsics::LowerIntrinsics,
466 &simplify::SimplifyCfg::new("elaborate-drops"),
467 // `Deaggregator` is conceptually part of MIR building, some backends rely on it happening
468 // and it can help optimizations.
469 &deaggregator::Deaggregator,
472 run_passes(tcx, body, MirPhase::DropLowering, &[post_borrowck_cleanup]);
475 fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
476 let mir_opt_level = tcx.sess.opts.debugging_opts.mir_opt_level;
478 // Lowering generator control-flow and variables has to happen before we do anything else
479 // to them. We run some optimizations before that, because they may be harder to do on the state
480 // machine than on MIR with async primitives.
481 let optimizations_with_generators: &[&dyn MirPass<'tcx>] = &[
482 &unreachable_prop::UnreachablePropagation,
483 &uninhabited_enum_branching::UninhabitedEnumBranching,
484 &simplify::SimplifyCfg::new("after-uninhabited-enum-branching"),
486 &generator::StateTransform,
489 // Even if we don't do optimizations, we still have to lower generators for codegen.
490 let no_optimizations_with_generators: &[&dyn MirPass<'tcx>] = &[&generator::StateTransform];
492 // The main optimizations that we do on MIR.
493 let optimizations: &[&dyn MirPass<'tcx>] = &[
494 &remove_unneeded_drops::RemoveUnneededDrops,
495 &match_branches::MatchBranchSimplification,
496 // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
497 &multiple_return_terminators::MultipleReturnTerminators,
498 &instcombine::InstCombine,
499 &const_prop::ConstProp,
500 &simplify_branches::SimplifyBranches::new("after-const-prop"),
501 &early_otherwise_branch::EarlyOtherwiseBranch,
502 &simplify_comparison_integral::SimplifyComparisonIntegral,
503 &simplify_try::SimplifyArmIdentity,
504 &simplify_try::SimplifyBranchSame,
505 &dest_prop::DestinationPropagation,
506 &simplify_branches::SimplifyBranches::new("final"),
507 &remove_noop_landing_pads::RemoveNoopLandingPads,
508 &simplify::SimplifyCfg::new("final"),
509 &nrvo::RenameReturnPlace,
510 &const_debuginfo::ConstDebugInfo,
511 &simplify::SimplifyLocals,
512 &multiple_return_terminators::MultipleReturnTerminators,
515 // Optimizations to run even if mir optimizations have been disabled.
516 let no_optimizations: &[&dyn MirPass<'tcx>] = &[
517 // FIXME(#70073): This pass is responsible for both optimization as well as some lints.
518 &const_prop::ConstProp,
521 // Some cleanup necessary at least for LLVM and potentially other codegen backends.
522 let pre_codegen_cleanup: &[&dyn MirPass<'tcx>] = &[
523 &add_call_guards::CriticalCallEdges,
524 // Dump the end result for testing and debugging purposes.
525 &dump_mir::Marker("PreCodegen"),
528 // End of pass declarations, now actually run the passes.
529 // Generator Lowering
534 MirPhase::GeneratorLowering,
536 if mir_opt_level > 0 {
537 optimizations_with_generators
539 no_optimizations_with_generators
544 // Main optimization passes
549 MirPhase::Optimization,
551 if mir_opt_level > 0 { optimizations } else { no_optimizations },
557 /// Optimize the MIR and prepare it for codegen.
558 fn optimized_mir<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx Body<'tcx> {
559 let did = did.expect_local();
560 assert_eq!(ty::WithOptConstParam::try_lookup(did, tcx), None);
561 tcx.arena.alloc(inner_optimized_mir(tcx, did))
564 fn inner_optimized_mir(tcx: TyCtxt<'_>, did: LocalDefId) -> Body<'_> {
565 if tcx.is_constructor(did.to_def_id()) {
566 // There's no reason to run all of the MIR passes on constructors when
567 // we can just output the MIR we want directly. This also saves const
568 // qualification and borrow checking the trouble of special casing
570 return shim::build_adt_ctor(tcx, did.to_def_id());
573 match tcx.hir().body_const_context(did) {
574 // Run the `mir_for_ctfe` query, which depends on `mir_drops_elaborated_and_const_checked`
575 // which we are going to steal below. Thus we need to run `mir_for_ctfe` first, so it
576 // computes and caches its result.
577 Some(hir::ConstContext::ConstFn) => tcx.ensure().mir_for_ctfe(did),
579 Some(other) => panic!("do not use `optimized_mir` for constants: {:?}", other),
582 tcx.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(did)).steal();
583 run_optimization_passes(tcx, &mut body);
585 debug_assert!(!body.has_free_regions(), "Free regions in optimized MIR");
590 /// Fetch all the promoteds of an item and prepare their MIR bodies to be ready for
591 /// constant evaluation once all substitutions become known.
592 fn promoted_mir<'tcx>(
594 def: ty::WithOptConstParam<LocalDefId>,
595 ) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
596 if tcx.is_constructor(def.did.to_def_id()) {
597 return tcx.arena.alloc(IndexVec::new());
600 if let Some(param_did) = def.const_param_did {
601 tcx.ensure().mir_borrowck_const_arg((def.did, param_did));
603 tcx.ensure().mir_borrowck(def.did);
605 let (_, promoted) = tcx.mir_promoted(def);
606 let mut promoted = promoted.steal();
608 for body in &mut promoted {
609 run_post_borrowck_cleanup_passes(tcx, body);
612 debug_assert!(!promoted.has_free_regions(), "Free regions in promoted MIR");
614 tcx.arena.alloc(promoted)