1 #![feature(box_patterns)]
2 #![feature(box_syntax)]
3 #![feature(crate_visibility_modifier)]
5 #![feature(map_try_insert)]
6 #![feature(min_specialization)]
7 #![feature(option_get_or_insert_default)]
9 #![feature(never_type)]
10 #![feature(trusted_step)]
11 #![feature(try_blocks)]
12 #![recursion_limit = "256"]
17 extern crate rustc_middle;
19 use required_consts::RequiredConstsVisitor;
20 use rustc_const_eval::util;
21 use rustc_data_structures::fx::FxHashSet;
22 use rustc_data_structures::steal::Steal;
24 use rustc_hir::def_id::{DefId, LocalDefId};
25 use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
26 use rustc_index::vec::IndexVec;
27 use rustc_middle::mir::visit::Visitor as _;
28 use rustc_middle::mir::{traversal, Body, ConstQualifs, MirPass, MirPhase, Promoted};
29 use rustc_middle::ty::query::Providers;
30 use rustc_middle::ty::{self, TyCtxt, TypeFoldable};
31 use rustc_span::{Span, Symbol};
36 use pass_manager::{self as pm, Lint, MirLint, WithMinOptLevel};
38 mod abort_unwinding_calls;
40 mod add_moves_for_packed_drops;
42 mod check_const_item_mutation;
44 pub mod check_unsafety;
45 mod cleanup_post_borrowck;
51 mod deduplicate_blocks;
54 mod early_otherwise_branch;
56 mod function_item_references;
64 mod multiple_return_terminators;
65 mod normalize_array_len;
67 mod remove_false_edges;
68 mod remove_noop_landing_pads;
69 mod remove_storage_markers;
70 mod remove_uninit_drops;
71 mod remove_unneeded_drops;
75 mod separate_const_switch;
78 mod simplify_branches;
79 mod simplify_comparison_integral;
81 mod uninhabited_enum_branching;
84 use rustc_const_eval::transform::check_consts::{self, ConstCx};
85 use rustc_const_eval::transform::promote_consts;
86 use rustc_const_eval::transform::validate;
87 use rustc_mir_dataflow::rustc_peek;
89 pub fn provide(providers: &mut Providers) {
90 check_unsafety::provide(providers);
91 check_packed_ref::provide(providers);
92 coverage::query::provide(providers);
93 shim::provide(providers);
94 *providers = Providers {
97 mir_const_qualif: |tcx, def_id| {
98 let def_id = def_id.expect_local();
99 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
100 tcx.mir_const_qualif_const_arg(def)
102 mir_const_qualif(tcx, ty::WithOptConstParam::unknown(def_id))
105 mir_const_qualif_const_arg: |tcx, (did, param_did)| {
106 mir_const_qualif(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
109 mir_drops_elaborated_and_const_checked,
111 mir_for_ctfe_of_const_arg,
114 is_ctfe_mir_available: |tcx, did| is_mir_available(tcx, did),
115 mir_callgraph_reachable: inline::cycle::mir_callgraph_reachable,
116 mir_inliner_callees: inline::cycle::mir_inliner_callees,
117 promoted_mir: |tcx, def_id| {
118 let def_id = def_id.expect_local();
119 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
120 tcx.promoted_mir_of_const_arg(def)
122 promoted_mir(tcx, ty::WithOptConstParam::unknown(def_id))
125 promoted_mir_of_const_arg: |tcx, (did, param_did)| {
126 promoted_mir(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
132 fn is_mir_available(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
133 let def_id = def_id.expect_local();
134 tcx.mir_keys(()).contains(&def_id)
137 /// Finds the full set of `DefId`s within the current crate that have
138 /// MIR associated with them.
139 fn mir_keys(tcx: TyCtxt<'_>, (): ()) -> FxHashSet<LocalDefId> {
140 let mut set = FxHashSet::default();
142 // All body-owners have MIR associated with them.
143 set.extend(tcx.hir().body_owners());
145 // Additionally, tuple struct/variant constructors have MIR, but
146 // they don't have a BodyId, so we need to build them separately.
147 struct GatherCtors<'a, 'tcx> {
149 set: &'a mut FxHashSet<LocalDefId>,
151 impl<'tcx> Visitor<'tcx> for GatherCtors<'_, 'tcx> {
152 fn visit_variant_data(
154 v: &'tcx hir::VariantData<'tcx>,
156 _: &'tcx hir::Generics<'tcx>,
160 if let hir::VariantData::Tuple(_, hir_id) = *v {
161 self.set.insert(self.tcx.hir().local_def_id(hir_id));
163 intravisit::walk_struct_def(self, v)
165 type Map = intravisit::ErasedMap<'tcx>;
166 fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
167 NestedVisitorMap::None
170 tcx.hir().visit_all_item_likes(&mut GatherCtors { tcx, set: &mut set }.as_deep_visitor());
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!
207 def: ty::WithOptConstParam<LocalDefId>,
208 ) -> &'tcx Steal<Body<'tcx>> {
209 if let Some(def) = def.try_upgrade(tcx) {
210 return tcx.mir_const(def);
213 // Unsafety check uses the raw mir, so make sure it is run.
214 if !tcx.sess.opts.debugging_opts.thir_unsafeck {
215 if let Some(param_did) = def.const_param_did {
216 tcx.ensure().unsafety_check_result_for_const_arg((def.did, param_did));
218 tcx.ensure().unsafety_check_result(def.did);
222 let mut body = tcx.mir_built(def).steal();
224 rustc_middle::mir::dump_mir(tcx, None, "mir_map", &0, &body, |_, _| Ok(()));
231 &Lint(check_packed_ref::CheckPackedRef),
232 &Lint(check_const_item_mutation::CheckConstItemMutation),
233 &Lint(function_item_references::FunctionItemReferences),
234 // What we need to do constant evaluation.
235 &simplify::SimplifyCfg::new("initial"),
236 &rustc_peek::SanityCheck, // Just a lint
237 &marker::PhaseChange(MirPhase::Const),
240 tcx.alloc_steal_mir(body)
243 /// Compute the main MIR body and the list of MIR bodies of the promoteds.
244 fn mir_promoted<'tcx>(
246 def: ty::WithOptConstParam<LocalDefId>,
247 ) -> (&'tcx Steal<Body<'tcx>>, &'tcx Steal<IndexVec<Promoted, Body<'tcx>>>) {
248 if let Some(def) = def.try_upgrade(tcx) {
249 return tcx.mir_promoted(def);
252 // Ensure that we compute the `mir_const_qualif` for constants at
253 // this point, before we steal the mir-const result.
254 // Also this means promotion can rely on all const checks having been done.
255 let _ = tcx.mir_const_qualif_opt_const_arg(def);
256 let mut body = tcx.mir_const(def).steal();
258 let mut required_consts = Vec::new();
259 let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
260 for (bb, bb_data) in traversal::reverse_postorder(&body) {
261 required_consts_visitor.visit_basic_block_data(bb, bb_data);
263 body.required_consts = required_consts;
265 // What we need to run borrowck etc.
266 let promote_pass = promote_consts::PromoteTemps::default();
272 &simplify::SimplifyCfg::new("promote-consts"),
273 &coverage::InstrumentCoverage,
277 let promoted = promote_pass.promoted_fragments.into_inner();
278 (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
281 /// Compute the MIR that is used during CTFE (and thus has no optimizations run on it)
282 fn mir_for_ctfe<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx Body<'tcx> {
283 let did = def_id.expect_local();
284 if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) {
285 tcx.mir_for_ctfe_of_const_arg(def)
287 tcx.arena.alloc(inner_mir_for_ctfe(tcx, ty::WithOptConstParam::unknown(did)))
291 /// Same as `mir_for_ctfe`, but used to get the MIR of a const generic parameter.
292 /// The docs on `WithOptConstParam` explain this a bit more, but the TLDR is that
293 /// we'd get cycle errors with `mir_for_ctfe`, because typeck would need to typeck
294 /// the const parameter while type checking the main body, which in turn would try
295 /// to type check the main body again.
296 fn mir_for_ctfe_of_const_arg<'tcx>(
298 (did, param_did): (LocalDefId, DefId),
299 ) -> &'tcx Body<'tcx> {
300 tcx.arena.alloc(inner_mir_for_ctfe(
302 ty::WithOptConstParam { did, const_param_did: Some(param_did) },
306 fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_> {
307 // FIXME: don't duplicate this between the optimized_mir/mir_for_ctfe queries
308 if tcx.is_constructor(def.did.to_def_id()) {
309 // There's no reason to run all of the MIR passes on constructors when
310 // we can just output the MIR we want directly. This also saves const
311 // qualification and borrow checking the trouble of special casing
313 return shim::build_adt_ctor(tcx, def.did.to_def_id());
318 .body_const_context(def.did)
319 .expect("mir_for_ctfe should not be used for runtime functions");
321 let mut body = tcx.mir_drops_elaborated_and_const_checked(def).borrow().clone();
324 // Do not const prop functions, either they get executed at runtime or exported to metadata,
325 // so we run const prop on them, or they don't, in which case we const evaluate some control
326 // flow paths of the function and any errors in those paths will get emitted as const eval
328 hir::ConstContext::ConstFn => {}
329 // Static items always get evaluated, so we can just let const eval see if any erroneous
330 // control flow paths get executed.
331 hir::ConstContext::Static(_) => {}
332 // Associated constants get const prop run so we detect common failure situations in the
333 // crate that defined the constant.
334 // Technically we want to not run on regular const items, but oli-obk doesn't know how to
335 // conveniently detect that at this point without looking at the HIR.
336 hir::ConstContext::Const => {
340 &[&const_prop::ConstProp, &marker::PhaseChange(MirPhase::Optimization)],
345 debug_assert!(!body.has_free_regions(tcx), "Free regions in MIR for CTFE");
350 /// Obtain just the main MIR (no promoteds) and run some cleanups on it. This also runs
351 /// mir borrowck *before* doing so in order to ensure that borrowck can be run and doesn't
352 /// end up missing the source MIR due to stealing happening.
353 fn mir_drops_elaborated_and_const_checked<'tcx>(
355 def: ty::WithOptConstParam<LocalDefId>,
356 ) -> &'tcx Steal<Body<'tcx>> {
357 if let Some(def) = def.try_upgrade(tcx) {
358 return tcx.mir_drops_elaborated_and_const_checked(def);
361 // (Mir-)Borrowck uses `mir_promoted`, so we have to force it to
362 // execute before we can steal.
363 if let Some(param_did) = def.const_param_did {
364 tcx.ensure().mir_borrowck_const_arg((def.did, param_did));
366 tcx.ensure().mir_borrowck(def.did);
369 let is_fn_like = tcx.hir().get_by_def_id(def.did).fn_kind().is_some();
371 let did = def.did.to_def_id();
372 let def = ty::WithOptConstParam::unknown(did);
374 // Do not compute the mir call graph without said call graph actually being used.
375 if inline::Inline.is_enabled(&tcx.sess) {
376 let _ = tcx.mir_inliner_callees(ty::InstanceDef::Item(def));
380 let (body, _) = tcx.mir_promoted(def);
381 let mut body = body.steal();
384 pm::run_passes(tcx, &mut body, &[&remove_false_edges::RemoveFalseEdges]);
386 // Do a little drop elaboration before const-checking if `const_precise_live_drops` is enabled.
387 if check_consts::post_drop_elaboration::checking_enabled(&ConstCx::new(tcx, &body)) {
392 &simplify::SimplifyCfg::new("remove-false-edges"),
393 &remove_uninit_drops::RemoveUninitDrops,
396 check_consts::post_drop_elaboration::check_live_drops(tcx, &body); // FIXME: make this a MIR lint
399 run_post_borrowck_cleanup_passes(tcx, &mut body);
400 assert!(body.phase == MirPhase::DropLowering);
401 tcx.alloc_steal_mir(body)
404 /// After this series of passes, no lifetime analysis based on borrowing can be done.
405 fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
406 debug!("post_borrowck_cleanup({:?})", body.source.def_id());
408 let post_borrowck_cleanup: &[&dyn MirPass<'tcx>] = &[
409 // Remove all things only needed by analysis
410 &simplify_branches::SimplifyConstCondition::new("initial"),
411 &remove_noop_landing_pads::RemoveNoopLandingPads,
412 &cleanup_post_borrowck::CleanupNonCodegenStatements,
413 &simplify::SimplifyCfg::new("early-opt"),
414 // These next passes must be executed together
415 &add_call_guards::CriticalCallEdges,
416 &elaborate_drops::ElaborateDrops,
417 // This will remove extraneous landing pads which are no longer
418 // necessary as well as well as forcing any call in a non-unwinding
419 // function calling a possibly-unwinding function to abort the process.
420 &abort_unwinding_calls::AbortUnwindingCalls,
421 // AddMovesForPackedDrops needs to run after drop
423 &add_moves_for_packed_drops::AddMovesForPackedDrops,
424 // `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
425 // but before optimizations begin.
426 &add_retag::AddRetag,
427 &lower_intrinsics::LowerIntrinsics,
428 &simplify::SimplifyCfg::new("elaborate-drops"),
429 // `Deaggregator` is conceptually part of MIR building, some backends rely on it happening
430 // and it can help optimizations.
431 &deaggregator::Deaggregator,
434 pm::run_passes(tcx, body, post_borrowck_cleanup);
437 fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
438 fn o1<T>(x: T) -> WithMinOptLevel<T> {
439 WithMinOptLevel(1, x)
442 // Lowering generator control-flow and variables has to happen before we do anything else
443 // to them. We run some optimizations before that, because they may be harder to do on the state
444 // machine than on MIR with async primitives.
449 &reveal_all::RevealAll, // has to be done before inlining, since inlined code is in RevealAll mode.
450 &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
451 &normalize_array_len::NormalizeArrayLen, // has to run after `slice::len` lowering
452 &unreachable_prop::UnreachablePropagation,
453 &uninhabited_enum_branching::UninhabitedEnumBranching,
454 &o1(simplify::SimplifyCfg::new("after-uninhabited-enum-branching")),
456 &generator::StateTransform,
460 assert!(body.phase == MirPhase::GeneratorLowering);
462 // The main optimizations that we do on MIR.
467 &remove_storage_markers::RemoveStorageMarkers,
468 &remove_zsts::RemoveZsts,
469 &const_goto::ConstGoto,
470 &remove_unneeded_drops::RemoveUnneededDrops,
471 &match_branches::MatchBranchSimplification,
472 // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
473 &multiple_return_terminators::MultipleReturnTerminators,
474 &instcombine::InstCombine,
475 &separate_const_switch::SeparateConstSwitch,
477 // FIXME(#70073): This pass is responsible for both optimization as well as some lints.
478 &const_prop::ConstProp,
480 // Const-prop runs unconditionally, but doesn't mutate the MIR at mir-opt-level=0.
481 &o1(simplify_branches::SimplifyConstCondition::new("after-const-prop")),
482 &early_otherwise_branch::EarlyOtherwiseBranch,
483 &simplify_comparison_integral::SimplifyComparisonIntegral,
484 &simplify_try::SimplifyArmIdentity,
485 &simplify_try::SimplifyBranchSame,
486 &dest_prop::DestinationPropagation,
487 &o1(simplify_branches::SimplifyConstCondition::new("final")),
488 &o1(remove_noop_landing_pads::RemoveNoopLandingPads),
489 &o1(simplify::SimplifyCfg::new("final")),
490 &nrvo::RenameReturnPlace,
491 &const_debuginfo::ConstDebugInfo,
492 &simplify::SimplifyLocals,
493 &multiple_return_terminators::MultipleReturnTerminators,
494 &deduplicate_blocks::DeduplicateBlocks,
495 // Some cleanup necessary at least for LLVM and potentially other codegen backends.
496 &add_call_guards::CriticalCallEdges,
497 &marker::PhaseChange(MirPhase::Optimization),
498 // Dump the end result for testing and debugging purposes.
499 &dump_mir::Marker("PreCodegen"),
504 /// Optimize the MIR and prepare it for codegen.
505 fn optimized_mir<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx Body<'tcx> {
506 let did = did.expect_local();
507 assert_eq!(ty::WithOptConstParam::try_lookup(did, tcx), None);
508 tcx.arena.alloc(inner_optimized_mir(tcx, did))
511 fn inner_optimized_mir(tcx: TyCtxt<'_>, did: LocalDefId) -> Body<'_> {
512 if tcx.is_constructor(did.to_def_id()) {
513 // There's no reason to run all of the MIR passes on constructors when
514 // we can just output the MIR we want directly. This also saves const
515 // qualification and borrow checking the trouble of special casing
517 return shim::build_adt_ctor(tcx, did.to_def_id());
520 match tcx.hir().body_const_context(did) {
521 // Run the `mir_for_ctfe` query, which depends on `mir_drops_elaborated_and_const_checked`
522 // which we are going to steal below. Thus we need to run `mir_for_ctfe` first, so it
523 // computes and caches its result.
524 Some(hir::ConstContext::ConstFn) => tcx.ensure().mir_for_ctfe(did),
526 Some(other) => panic!("do not use `optimized_mir` for constants: {:?}", other),
529 tcx.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(did)).steal();
530 run_optimization_passes(tcx, &mut body);
532 debug_assert!(!body.has_free_regions(tcx), "Free regions in optimized MIR");
537 /// Fetch all the promoteds of an item and prepare their MIR bodies to be ready for
538 /// constant evaluation once all substitutions become known.
539 fn promoted_mir<'tcx>(
541 def: ty::WithOptConstParam<LocalDefId>,
542 ) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
543 if tcx.is_constructor(def.did.to_def_id()) {
544 return tcx.arena.alloc(IndexVec::new());
547 if let Some(param_did) = def.const_param_did {
548 tcx.ensure().mir_borrowck_const_arg((def.did, param_did));
550 tcx.ensure().mir_borrowck(def.did);
552 let (_, promoted) = tcx.mir_promoted(def);
553 let mut promoted = promoted.steal();
555 for body in &mut promoted {
556 run_post_borrowck_cleanup_passes(tcx, body);
559 debug_assert!(!promoted.has_free_regions(tcx), "Free regions in promoted MIR");
561 tcx.arena.alloc(promoted)