1 #![allow(rustc::potential_query_instability)]
2 #![feature(box_patterns)]
3 #![feature(let_chains)]
5 #![feature(map_try_insert)]
6 #![feature(min_specialization)]
7 #![feature(never_type)]
9 #![feature(option_get_or_insert_default)]
10 #![feature(trusted_step)]
11 #![feature(try_blocks)]
12 #![feature(yeet_expr)]
13 #![recursion_limit = "256"]
18 extern crate rustc_middle;
20 use required_consts::RequiredConstsVisitor;
21 use rustc_const_eval::util;
22 use rustc_data_structures::fx::FxIndexSet;
23 use rustc_data_structures::steal::Steal;
25 use rustc_hir::def_id::{DefId, LocalDefId};
26 use rustc_hir::intravisit::{self, Visitor};
27 use rustc_index::vec::IndexVec;
28 use rustc_middle::mir::visit::Visitor as _;
29 use rustc_middle::mir::{
30 traversal, AnalysisPhase, Body, ConstQualifs, MirPass, MirPhase, Promoted, RuntimePhase,
32 use rustc_middle::ty::query::Providers;
33 use rustc_middle::ty::{self, TyCtxt, TypeVisitable};
38 use pass_manager::{self as pm, Lint, MirLint, WithMinOptLevel};
40 mod abort_unwinding_calls;
42 mod add_moves_for_packed_drops;
44 mod check_const_item_mutation;
46 pub mod check_unsafety;
47 // This pass is public to allow external drivers to perform MIR cleanup
48 pub mod cleanup_post_borrowck;
54 mod dead_store_elimination;
56 mod deduplicate_blocks;
60 mod early_otherwise_branch;
61 mod elaborate_box_derefs;
64 mod function_item_references;
72 mod multiple_return_terminators;
73 mod normalize_array_len;
75 // This pass is public to allow external drivers to perform MIR cleanup
76 pub mod remove_false_edges;
77 mod remove_noop_landing_pads;
78 mod remove_storage_markers;
79 mod remove_uninit_drops;
80 mod remove_unneeded_drops;
84 mod separate_const_switch;
86 // This pass is public to allow external drivers to perform MIR cleanup
88 mod simplify_branches;
89 mod simplify_comparison_integral;
91 mod uninhabited_enum_branching;
94 use rustc_const_eval::transform::check_consts::{self, ConstCx};
95 use rustc_const_eval::transform::promote_consts;
96 use rustc_const_eval::transform::validate;
97 use rustc_mir_dataflow::rustc_peek;
99 pub fn provide(providers: &mut Providers) {
100 check_unsafety::provide(providers);
101 check_packed_ref::provide(providers);
102 coverage::query::provide(providers);
103 ffi_unwind_calls::provide(providers);
104 shim::provide(providers);
105 *providers = Providers {
108 mir_const_qualif: |tcx, def_id| {
109 let def_id = def_id.expect_local();
110 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
111 tcx.mir_const_qualif_const_arg(def)
113 mir_const_qualif(tcx, ty::WithOptConstParam::unknown(def_id))
116 mir_const_qualif_const_arg: |tcx, (did, param_did)| {
117 mir_const_qualif(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
120 mir_drops_elaborated_and_const_checked,
122 mir_for_ctfe_of_const_arg,
125 is_ctfe_mir_available: |tcx, did| is_mir_available(tcx, did),
126 mir_callgraph_reachable: inline::cycle::mir_callgraph_reachable,
127 mir_inliner_callees: inline::cycle::mir_inliner_callees,
128 promoted_mir: |tcx, def_id| {
129 let def_id = def_id.expect_local();
130 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
131 tcx.promoted_mir_of_const_arg(def)
133 promoted_mir(tcx, ty::WithOptConstParam::unknown(def_id))
136 promoted_mir_of_const_arg: |tcx, (did, param_did)| {
137 promoted_mir(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
143 fn is_mir_available(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
144 let def_id = def_id.expect_local();
145 tcx.mir_keys(()).contains(&def_id)
148 /// Finds the full set of `DefId`s within the current crate that have
149 /// MIR associated with them.
150 fn mir_keys(tcx: TyCtxt<'_>, (): ()) -> FxIndexSet<LocalDefId> {
151 let mut set = FxIndexSet::default();
153 // All body-owners have MIR associated with them.
154 set.extend(tcx.hir().body_owners());
156 // Additionally, tuple struct/variant constructors have MIR, but
157 // they don't have a BodyId, so we need to build them separately.
158 struct GatherCtors<'a, 'tcx> {
160 set: &'a mut FxIndexSet<LocalDefId>,
162 impl<'tcx> Visitor<'tcx> for GatherCtors<'_, 'tcx> {
163 fn visit_variant_data(&mut self, v: &'tcx hir::VariantData<'tcx>) {
164 if let hir::VariantData::Tuple(_, hir_id) = *v {
165 self.set.insert(self.tcx.hir().local_def_id(hir_id));
167 intravisit::walk_struct_def(self, v)
170 tcx.hir().visit_all_item_likes_in_crate(&mut GatherCtors { tcx, set: &mut set });
175 fn mir_const_qualif(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> ConstQualifs {
176 let const_kind = tcx.hir().body_const_context(def.did);
178 // No need to const-check a non-const `fn`.
179 if const_kind.is_none() {
180 return Default::default();
183 // N.B., this `borrow()` is guaranteed to be valid (i.e., the value
184 // cannot yet be stolen), because `mir_promoted()`, which steals
185 // from `mir_const(), forces this query to execute before
186 // performing the steal.
187 let body = &tcx.mir_const(def).borrow();
189 if body.return_ty().references_error() {
190 tcx.sess.delay_span_bug(body.span, "mir_const_qualif: MIR had errors");
191 return Default::default();
194 let ccx = check_consts::ConstCx { body, tcx, const_kind, param_env: tcx.param_env(def.did) };
196 let mut validator = check_consts::check::Checker::new(&ccx);
197 validator.check_body();
199 // We return the qualifs in the return place for every MIR body, even though it is only used
200 // when deciding to promote a reference to a `const` for now.
201 validator.qualifs_in_return_place()
204 /// Make MIR ready for const evaluation. This is run on all MIR, not just on consts!
205 /// FIXME(oli-obk): it's unclear whether we still need this phase (and its corresponding query).
206 /// We used to have this for pre-miri MIR based const eval.
209 def: ty::WithOptConstParam<LocalDefId>,
210 ) -> &'tcx Steal<Body<'tcx>> {
211 if let Some(def) = def.try_upgrade(tcx) {
212 return tcx.mir_const(def);
215 // Unsafety check uses the raw mir, so make sure it is run.
216 if !tcx.sess.opts.unstable_opts.thir_unsafeck {
217 if let Some(param_did) = def.const_param_did {
218 tcx.ensure().unsafety_check_result_for_const_arg((def.did, param_did));
220 tcx.ensure().unsafety_check_result(def.did);
224 // has_ffi_unwind_calls query uses the raw mir, so make sure it is run.
225 tcx.ensure().has_ffi_unwind_calls(def.did);
227 let mut body = tcx.mir_built(def).steal();
229 rustc_middle::mir::dump_mir(tcx, None, "mir_map", &0, &body, |_, _| Ok(()));
236 &Lint(check_packed_ref::CheckPackedRef),
237 &Lint(check_const_item_mutation::CheckConstItemMutation),
238 &Lint(function_item_references::FunctionItemReferences),
239 // What we need to do constant evaluation.
240 &simplify::SimplifyCfg::new("initial"),
241 &rustc_peek::SanityCheck, // Just a lint
244 tcx.alloc_steal_mir(body)
247 /// Compute the main MIR body and the list of MIR bodies of the promoteds.
248 fn mir_promoted<'tcx>(
250 def: ty::WithOptConstParam<LocalDefId>,
251 ) -> (&'tcx Steal<Body<'tcx>>, &'tcx Steal<IndexVec<Promoted, Body<'tcx>>>) {
252 if let Some(def) = def.try_upgrade(tcx) {
253 return tcx.mir_promoted(def);
256 // Ensure that we compute the `mir_const_qualif` for constants at
257 // this point, before we steal the mir-const result.
258 // Also this means promotion can rely on all const checks having been done.
259 let const_qualifs = tcx.mir_const_qualif_opt_const_arg(def);
260 let mut body = tcx.mir_const(def).steal();
261 if let Some(error_reported) = const_qualifs.tainted_by_errors {
262 body.tainted_by_errors = Some(error_reported);
265 let mut required_consts = Vec::new();
266 let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
267 for (bb, bb_data) in traversal::reverse_postorder(&body) {
268 required_consts_visitor.visit_basic_block_data(bb, bb_data);
270 body.required_consts = required_consts;
272 // What we need to run borrowck etc.
273 let promote_pass = promote_consts::PromoteTemps::default();
279 &simplify::SimplifyCfg::new("promote-consts"),
280 &coverage::InstrumentCoverage,
284 let promoted = promote_pass.promoted_fragments.into_inner();
285 (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
288 /// Compute the MIR that is used during CTFE (and thus has no optimizations run on it)
289 fn mir_for_ctfe<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx Body<'tcx> {
290 let did = def_id.expect_local();
291 if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) {
292 tcx.mir_for_ctfe_of_const_arg(def)
294 tcx.arena.alloc(inner_mir_for_ctfe(tcx, ty::WithOptConstParam::unknown(did)))
298 /// Same as `mir_for_ctfe`, but used to get the MIR of a const generic parameter.
299 /// The docs on `WithOptConstParam` explain this a bit more, but the TLDR is that
300 /// we'd get cycle errors with `mir_for_ctfe`, because typeck would need to typeck
301 /// the const parameter while type checking the main body, which in turn would try
302 /// to type check the main body again.
303 fn mir_for_ctfe_of_const_arg<'tcx>(
305 (did, param_did): (LocalDefId, DefId),
306 ) -> &'tcx Body<'tcx> {
307 tcx.arena.alloc(inner_mir_for_ctfe(
309 ty::WithOptConstParam { did, const_param_did: Some(param_did) },
313 fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_> {
314 // FIXME: don't duplicate this between the optimized_mir/mir_for_ctfe queries
315 if tcx.is_constructor(def.did.to_def_id()) {
316 // There's no reason to run all of the MIR passes on constructors when
317 // we can just output the MIR we want directly. This also saves const
318 // qualification and borrow checking the trouble of special casing
320 return shim::build_adt_ctor(tcx, def.did.to_def_id());
325 .body_const_context(def.did)
326 .expect("mir_for_ctfe should not be used for runtime functions");
328 let mut body = tcx.mir_drops_elaborated_and_const_checked(def).borrow().clone();
331 // Do not const prop functions, either they get executed at runtime or exported to metadata,
332 // so we run const prop on them, or they don't, in which case we const evaluate some control
333 // flow paths of the function and any errors in those paths will get emitted as const eval
335 hir::ConstContext::ConstFn => {}
336 // Static items always get evaluated, so we can just let const eval see if any erroneous
337 // control flow paths get executed.
338 hir::ConstContext::Static(_) => {}
339 // Associated constants get const prop run so we detect common failure situations in the
340 // crate that defined the constant.
341 // Technically we want to not run on regular const items, but oli-obk doesn't know how to
342 // conveniently detect that at this point without looking at the HIR.
343 hir::ConstContext::Const => {
348 &const_prop::ConstProp,
349 &marker::PhaseChange(MirPhase::Runtime(RuntimePhase::Optimized)),
355 debug_assert!(!body.has_free_regions(), "Free regions in MIR for CTFE");
360 /// Obtain just the main MIR (no promoteds) and run some cleanups on it. This also runs
361 /// mir borrowck *before* doing so in order to ensure that borrowck can be run and doesn't
362 /// end up missing the source MIR due to stealing happening.
363 fn mir_drops_elaborated_and_const_checked<'tcx>(
365 def: ty::WithOptConstParam<LocalDefId>,
366 ) -> &'tcx Steal<Body<'tcx>> {
367 if let Some(def) = def.try_upgrade(tcx) {
368 return tcx.mir_drops_elaborated_and_const_checked(def);
371 let mir_borrowck = tcx.mir_borrowck_opt_const_arg(def);
373 let is_fn_like = tcx.def_kind(def.did).is_fn_like();
375 let did = def.did.to_def_id();
376 let def = ty::WithOptConstParam::unknown(did);
378 // Do not compute the mir call graph without said call graph actually being used.
379 if inline::Inline.is_enabled(&tcx.sess) {
380 let _ = tcx.mir_inliner_callees(ty::InstanceDef::Item(def));
384 let (body, _) = tcx.mir_promoted(def);
385 let mut body = body.steal();
386 if let Some(error_reported) = mir_borrowck.tainted_by_errors {
387 body.tainted_by_errors = Some(error_reported);
390 run_analysis_to_runtime_passes(tcx, &mut body);
392 tcx.alloc_steal_mir(body)
395 fn run_analysis_to_runtime_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
396 assert!(body.phase == MirPhase::Analysis(AnalysisPhase::Initial));
397 let did = body.source.def_id();
399 debug!("analysis_mir_cleanup({:?})", did);
400 run_analysis_cleanup_passes(tcx, body);
401 assert!(body.phase == MirPhase::Analysis(AnalysisPhase::PostCleanup));
403 // Do a little drop elaboration before const-checking if `const_precise_live_drops` is enabled.
404 if check_consts::post_drop_elaboration::checking_enabled(&ConstCx::new(tcx, &body)) {
409 &remove_uninit_drops::RemoveUninitDrops,
410 &simplify::SimplifyCfg::new("remove-false-edges"),
413 check_consts::post_drop_elaboration::check_live_drops(tcx, &body); // FIXME: make this a MIR lint
416 debug!("runtime_mir_lowering({:?})", did);
417 run_runtime_lowering_passes(tcx, body);
418 assert!(body.phase == MirPhase::Runtime(RuntimePhase::Initial));
420 debug!("runtime_mir_cleanup({:?})", did);
421 run_runtime_cleanup_passes(tcx, body);
422 assert!(body.phase == MirPhase::Runtime(RuntimePhase::PostCleanup));
425 // FIXME(JakobDegen): Can we make these lists of passes consts?
427 /// After this series of passes, no lifetime analysis based on borrowing can be done.
428 fn run_analysis_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
429 let passes: &[&dyn MirPass<'tcx>] = &[
430 &remove_false_edges::RemoveFalseEdges,
431 &simplify_branches::SimplifyConstCondition::new("initial"),
432 &remove_noop_landing_pads::RemoveNoopLandingPads,
433 &cleanup_post_borrowck::CleanupNonCodegenStatements,
434 &simplify::SimplifyCfg::new("early-opt"),
435 &deref_separator::Derefer,
436 &marker::PhaseChange(MirPhase::Analysis(AnalysisPhase::PostCleanup)),
439 pm::run_passes(tcx, body, passes);
442 /// Returns the sequence of passes that lowers analysis to runtime MIR.
443 fn run_runtime_lowering_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
444 let passes: &[&dyn MirPass<'tcx>] = &[
445 // These next passes must be executed together
446 &add_call_guards::CriticalCallEdges,
447 &elaborate_drops::ElaborateDrops,
448 // This will remove extraneous landing pads which are no longer
449 // necessary as well as well as forcing any call in a non-unwinding
450 // function calling a possibly-unwinding function to abort the process.
451 &abort_unwinding_calls::AbortUnwindingCalls,
452 // AddMovesForPackedDrops needs to run after drop
454 &add_moves_for_packed_drops::AddMovesForPackedDrops,
455 // `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
456 // but before optimizations begin.
457 &elaborate_box_derefs::ElaborateBoxDerefs,
458 &generator::StateTransform,
459 &add_retag::AddRetag,
460 // Deaggregator is necessary for const prop. We may want to consider implementing
461 // CTFE support for aggregates.
462 &deaggregator::Deaggregator,
463 &Lint(const_prop_lint::ConstProp),
464 &marker::PhaseChange(MirPhase::Runtime(RuntimePhase::Initial)),
466 pm::run_passes_no_validate(tcx, body, passes);
469 /// Returns the sequence of passes that do the initial cleanup of runtime MIR.
470 fn run_runtime_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
471 let passes: &[&dyn MirPass<'tcx>] = &[
472 &elaborate_box_derefs::ElaborateBoxDerefs,
473 &lower_intrinsics::LowerIntrinsics,
474 &simplify::SimplifyCfg::new("elaborate-drops"),
475 &marker::PhaseChange(MirPhase::Runtime(RuntimePhase::PostCleanup)),
478 pm::run_passes(tcx, body, passes);
481 fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
482 fn o1<T>(x: T) -> WithMinOptLevel<T> {
483 WithMinOptLevel(1, x)
486 // The main optimizations that we do on MIR.
491 &reveal_all::RevealAll, // has to be done before inlining, since inlined code is in RevealAll mode.
492 &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
493 &normalize_array_len::NormalizeArrayLen, // has to run after `slice::len` lowering
494 &unreachable_prop::UnreachablePropagation,
495 &uninhabited_enum_branching::UninhabitedEnumBranching,
496 &o1(simplify::SimplifyCfg::new("after-uninhabited-enum-branching")),
498 &remove_storage_markers::RemoveStorageMarkers,
499 &remove_zsts::RemoveZsts,
500 &const_goto::ConstGoto,
501 &remove_unneeded_drops::RemoveUnneededDrops,
502 &match_branches::MatchBranchSimplification,
503 // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
504 &multiple_return_terminators::MultipleReturnTerminators,
505 &instcombine::InstCombine,
506 &separate_const_switch::SeparateConstSwitch,
508 // FIXME(#70073): This pass is responsible for both optimization as well as some lints.
509 &const_prop::ConstProp,
511 // Const-prop runs unconditionally, but doesn't mutate the MIR at mir-opt-level=0.
512 &const_debuginfo::ConstDebugInfo,
513 &o1(simplify_branches::SimplifyConstCondition::new("after-const-prop")),
514 &early_otherwise_branch::EarlyOtherwiseBranch,
515 &simplify_comparison_integral::SimplifyComparisonIntegral,
516 &simplify_try::SimplifyArmIdentity,
517 &simplify_try::SimplifyBranchSame,
518 &dead_store_elimination::DeadStoreElimination,
519 &dest_prop::DestinationPropagation,
520 &o1(simplify_branches::SimplifyConstCondition::new("final")),
521 &o1(remove_noop_landing_pads::RemoveNoopLandingPads),
522 &o1(simplify::SimplifyCfg::new("final")),
523 &nrvo::RenameReturnPlace,
524 &simplify::SimplifyLocals,
525 &multiple_return_terminators::MultipleReturnTerminators,
526 &deduplicate_blocks::DeduplicateBlocks,
527 // Some cleanup necessary at least for LLVM and potentially other codegen backends.
528 &add_call_guards::CriticalCallEdges,
529 &marker::PhaseChange(MirPhase::Runtime(RuntimePhase::Optimized)),
530 // Dump the end result for testing and debugging purposes.
531 &dump_mir::Marker("PreCodegen"),
536 /// Optimize the MIR and prepare it for codegen.
537 fn optimized_mir<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx Body<'tcx> {
538 let did = did.expect_local();
539 assert_eq!(ty::WithOptConstParam::try_lookup(did, tcx), None);
540 tcx.arena.alloc(inner_optimized_mir(tcx, did))
543 fn inner_optimized_mir(tcx: TyCtxt<'_>, did: LocalDefId) -> Body<'_> {
544 if tcx.is_constructor(did.to_def_id()) {
545 // There's no reason to run all of the MIR passes on constructors when
546 // we can just output the MIR we want directly. This also saves const
547 // qualification and borrow checking the trouble of special casing
549 return shim::build_adt_ctor(tcx, did.to_def_id());
552 match tcx.hir().body_const_context(did) {
553 // Run the `mir_for_ctfe` query, which depends on `mir_drops_elaborated_and_const_checked`
554 // which we are going to steal below. Thus we need to run `mir_for_ctfe` first, so it
555 // computes and caches its result.
556 Some(hir::ConstContext::ConstFn) => tcx.ensure().mir_for_ctfe(did),
558 Some(other) => panic!("do not use `optimized_mir` for constants: {:?}", other),
560 debug!("about to call mir_drops_elaborated...");
562 tcx.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(did)).steal();
563 debug!("body: {:#?}", body);
564 run_optimization_passes(tcx, &mut body);
566 debug_assert!(!body.has_free_regions(), "Free regions in optimized MIR");
571 /// Fetch all the promoteds of an item and prepare their MIR bodies to be ready for
572 /// constant evaluation once all substitutions become known.
573 fn promoted_mir<'tcx>(
575 def: ty::WithOptConstParam<LocalDefId>,
576 ) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
577 if tcx.is_constructor(def.did.to_def_id()) {
578 return tcx.arena.alloc(IndexVec::new());
581 let tainted_by_errors = tcx.mir_borrowck_opt_const_arg(def).tainted_by_errors;
582 let mut promoted = tcx.mir_promoted(def).1.steal();
584 for body in &mut promoted {
585 if let Some(error_reported) = tainted_by_errors {
586 body.tainted_by_errors = Some(error_reported);
588 run_analysis_to_runtime_passes(tcx, body);
591 debug_assert!(!promoted.has_free_regions(), "Free regions in promoted MIR");
593 tcx.arena.alloc(promoted)