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::{traversal, Body, ConstQualifs, MirPass, MirPhase, Promoted};
30 use rustc_middle::ty::query::Providers;
31 use rustc_middle::ty::{self, TyCtxt, TypeVisitable};
32 use rustc_span::{Span, Symbol};
37 use pass_manager::{self as pm, Lint, MirLint, WithMinOptLevel};
39 mod abort_unwinding_calls;
41 mod add_moves_for_packed_drops;
43 mod check_const_item_mutation;
45 pub mod check_unsafety;
46 // This pass is public to allow external drivers to perform MIR cleanup
47 pub mod cleanup_post_borrowck;
53 mod dead_store_elimination;
55 mod deduplicate_blocks;
59 mod early_otherwise_branch;
60 mod elaborate_box_derefs;
63 mod function_item_references;
71 mod multiple_return_terminators;
72 mod normalize_array_len;
74 // This pass is public to allow external drivers to perform MIR cleanup
75 pub mod remove_false_edges;
76 mod remove_noop_landing_pads;
77 mod remove_storage_markers;
78 mod remove_uninit_drops;
79 mod remove_unneeded_drops;
83 mod separate_const_switch;
85 // This pass is public to allow external drivers to perform MIR cleanup
87 mod simplify_branches;
88 mod simplify_comparison_integral;
90 mod uninhabited_enum_branching;
93 use rustc_const_eval::transform::check_consts::{self, ConstCx};
94 use rustc_const_eval::transform::promote_consts;
95 use rustc_const_eval::transform::validate;
96 use rustc_mir_dataflow::rustc_peek;
98 pub fn provide(providers: &mut Providers) {
99 check_unsafety::provide(providers);
100 check_packed_ref::provide(providers);
101 coverage::query::provide(providers);
102 ffi_unwind_calls::provide(providers);
103 shim::provide(providers);
104 *providers = Providers {
107 mir_const_qualif: |tcx, def_id| {
108 let def_id = def_id.expect_local();
109 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
110 tcx.mir_const_qualif_const_arg(def)
112 mir_const_qualif(tcx, ty::WithOptConstParam::unknown(def_id))
115 mir_const_qualif_const_arg: |tcx, (did, param_did)| {
116 mir_const_qualif(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
119 mir_drops_elaborated_and_const_checked,
121 mir_for_ctfe_of_const_arg,
124 is_ctfe_mir_available: |tcx, did| is_mir_available(tcx, did),
125 mir_callgraph_reachable: inline::cycle::mir_callgraph_reachable,
126 mir_inliner_callees: inline::cycle::mir_inliner_callees,
127 promoted_mir: |tcx, def_id| {
128 let def_id = def_id.expect_local();
129 if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
130 tcx.promoted_mir_of_const_arg(def)
132 promoted_mir(tcx, ty::WithOptConstParam::unknown(def_id))
135 promoted_mir_of_const_arg: |tcx, (did, param_did)| {
136 promoted_mir(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
142 fn is_mir_available(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
143 let def_id = def_id.expect_local();
144 tcx.mir_keys(()).contains(&def_id)
147 /// Finds the full set of `DefId`s within the current crate that have
148 /// MIR associated with them.
149 fn mir_keys(tcx: TyCtxt<'_>, (): ()) -> FxIndexSet<LocalDefId> {
150 let mut set = FxIndexSet::default();
152 // All body-owners have MIR associated with them.
153 set.extend(tcx.hir().body_owners());
155 // Additionally, tuple struct/variant constructors have MIR, but
156 // they don't have a BodyId, so we need to build them separately.
157 struct GatherCtors<'a, 'tcx> {
159 set: &'a mut FxIndexSet<LocalDefId>,
161 impl<'tcx> Visitor<'tcx> for GatherCtors<'_, 'tcx> {
162 fn visit_variant_data(
164 v: &'tcx hir::VariantData<'tcx>,
166 _: &'tcx hir::Generics<'tcx>,
170 if let hir::VariantData::Tuple(_, hir_id) = *v {
171 self.set.insert(self.tcx.hir().local_def_id(hir_id));
173 intravisit::walk_struct_def(self, v)
176 tcx.hir().deep_visit_all_item_likes(&mut GatherCtors { tcx, set: &mut set });
181 fn mir_const_qualif(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> ConstQualifs {
182 let const_kind = tcx.hir().body_const_context(def.did);
184 // No need to const-check a non-const `fn`.
185 if const_kind.is_none() {
186 return Default::default();
189 // N.B., this `borrow()` is guaranteed to be valid (i.e., the value
190 // cannot yet be stolen), because `mir_promoted()`, which steals
191 // from `mir_const(), forces this query to execute before
192 // performing the steal.
193 let body = &tcx.mir_const(def).borrow();
195 if body.return_ty().references_error() {
196 tcx.sess.delay_span_bug(body.span, "mir_const_qualif: MIR had errors");
197 return Default::default();
200 let ccx = check_consts::ConstCx { body, tcx, const_kind, param_env: tcx.param_env(def.did) };
202 let mut validator = check_consts::check::Checker::new(&ccx);
203 validator.check_body();
205 // We return the qualifs in the return place for every MIR body, even though it is only used
206 // when deciding to promote a reference to a `const` for now.
207 validator.qualifs_in_return_place()
210 /// Make MIR ready for const evaluation. This is run on all MIR, not just on consts!
213 def: ty::WithOptConstParam<LocalDefId>,
214 ) -> &'tcx Steal<Body<'tcx>> {
215 if let Some(def) = def.try_upgrade(tcx) {
216 return tcx.mir_const(def);
219 // Unsafety check uses the raw mir, so make sure it is run.
220 if !tcx.sess.opts.debugging_opts.thir_unsafeck {
221 if let Some(param_did) = def.const_param_did {
222 tcx.ensure().unsafety_check_result_for_const_arg((def.did, param_did));
224 tcx.ensure().unsafety_check_result(def.did);
228 // has_ffi_unwind_calls query uses the raw mir, so make sure it is run.
229 tcx.ensure().has_ffi_unwind_calls(def.did);
231 let mut body = tcx.mir_built(def).steal();
233 rustc_middle::mir::dump_mir(tcx, None, "mir_map", &0, &body, |_, _| Ok(()));
240 &Lint(check_packed_ref::CheckPackedRef),
241 &Lint(check_const_item_mutation::CheckConstItemMutation),
242 &Lint(function_item_references::FunctionItemReferences),
243 // What we need to do constant evaluation.
244 &simplify::SimplifyCfg::new("initial"),
245 &rustc_peek::SanityCheck, // Just a lint
246 &marker::PhaseChange(MirPhase::Const),
249 tcx.alloc_steal_mir(body)
252 /// Compute the main MIR body and the list of MIR bodies of the promoteds.
253 fn mir_promoted<'tcx>(
255 def: ty::WithOptConstParam<LocalDefId>,
256 ) -> (&'tcx Steal<Body<'tcx>>, &'tcx Steal<IndexVec<Promoted, Body<'tcx>>>) {
257 if let Some(def) = def.try_upgrade(tcx) {
258 return tcx.mir_promoted(def);
261 // Ensure that we compute the `mir_const_qualif` for constants at
262 // this point, before we steal the mir-const result.
263 // Also this means promotion can rely on all const checks having been done.
264 let const_qualifs = tcx.mir_const_qualif_opt_const_arg(def);
265 let mut body = tcx.mir_const(def).steal();
266 if let Some(error_reported) = const_qualifs.tainted_by_errors {
267 body.tainted_by_errors = Some(error_reported);
270 let mut required_consts = Vec::new();
271 let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
272 for (bb, bb_data) in traversal::reverse_postorder(&body) {
273 required_consts_visitor.visit_basic_block_data(bb, bb_data);
275 body.required_consts = required_consts;
277 // What we need to run borrowck etc.
278 let promote_pass = promote_consts::PromoteTemps::default();
284 &simplify::SimplifyCfg::new("promote-consts"),
285 &coverage::InstrumentCoverage,
289 let promoted = promote_pass.promoted_fragments.into_inner();
290 (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
293 /// Compute the MIR that is used during CTFE (and thus has no optimizations run on it)
294 fn mir_for_ctfe<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx Body<'tcx> {
295 let did = def_id.expect_local();
296 if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) {
297 tcx.mir_for_ctfe_of_const_arg(def)
299 tcx.arena.alloc(inner_mir_for_ctfe(tcx, ty::WithOptConstParam::unknown(did)))
303 /// Same as `mir_for_ctfe`, but used to get the MIR of a const generic parameter.
304 /// The docs on `WithOptConstParam` explain this a bit more, but the TLDR is that
305 /// we'd get cycle errors with `mir_for_ctfe`, because typeck would need to typeck
306 /// the const parameter while type checking the main body, which in turn would try
307 /// to type check the main body again.
308 fn mir_for_ctfe_of_const_arg<'tcx>(
310 (did, param_did): (LocalDefId, DefId),
311 ) -> &'tcx Body<'tcx> {
312 tcx.arena.alloc(inner_mir_for_ctfe(
314 ty::WithOptConstParam { did, const_param_did: Some(param_did) },
318 fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_> {
319 // FIXME: don't duplicate this between the optimized_mir/mir_for_ctfe queries
320 if tcx.is_constructor(def.did.to_def_id()) {
321 // There's no reason to run all of the MIR passes on constructors when
322 // we can just output the MIR we want directly. This also saves const
323 // qualification and borrow checking the trouble of special casing
325 return shim::build_adt_ctor(tcx, def.did.to_def_id());
330 .body_const_context(def.did)
331 .expect("mir_for_ctfe should not be used for runtime functions");
333 let mut body = tcx.mir_drops_elaborated_and_const_checked(def).borrow().clone();
336 // Do not const prop functions, either they get executed at runtime or exported to metadata,
337 // so we run const prop on them, or they don't, in which case we const evaluate some control
338 // flow paths of the function and any errors in those paths will get emitted as const eval
340 hir::ConstContext::ConstFn => {}
341 // Static items always get evaluated, so we can just let const eval see if any erroneous
342 // control flow paths get executed.
343 hir::ConstContext::Static(_) => {}
344 // Associated constants get const prop run so we detect common failure situations in the
345 // crate that defined the constant.
346 // Technically we want to not run on regular const items, but oli-obk doesn't know how to
347 // conveniently detect that at this point without looking at the HIR.
348 hir::ConstContext::Const => {
352 &[&const_prop::ConstProp, &marker::PhaseChange(MirPhase::Optimized)],
357 debug_assert!(!body.has_free_regions(), "Free regions in MIR for CTFE");
362 /// Obtain just the main MIR (no promoteds) and run some cleanups on it. This also runs
363 /// mir borrowck *before* doing so in order to ensure that borrowck can be run and doesn't
364 /// end up missing the source MIR due to stealing happening.
365 fn mir_drops_elaborated_and_const_checked<'tcx>(
367 def: ty::WithOptConstParam<LocalDefId>,
368 ) -> &'tcx Steal<Body<'tcx>> {
369 if let Some(def) = def.try_upgrade(tcx) {
370 return tcx.mir_drops_elaborated_and_const_checked(def);
373 let mir_borrowck = tcx.mir_borrowck_opt_const_arg(def);
375 let is_fn_like = tcx.def_kind(def.did).is_fn_like();
377 let did = def.did.to_def_id();
378 let def = ty::WithOptConstParam::unknown(did);
380 // Do not compute the mir call graph without said call graph actually being used.
381 if inline::Inline.is_enabled(&tcx.sess) {
382 let _ = tcx.mir_inliner_callees(ty::InstanceDef::Item(def));
386 let (body, _) = tcx.mir_promoted(def);
387 let mut body = body.steal();
388 if let Some(error_reported) = mir_borrowck.tainted_by_errors {
389 body.tainted_by_errors = Some(error_reported);
393 pm::run_passes(tcx, &mut body, &[&remove_false_edges::RemoveFalseEdges]);
395 // Do a little drop elaboration before const-checking if `const_precise_live_drops` is enabled.
396 if check_consts::post_drop_elaboration::checking_enabled(&ConstCx::new(tcx, &body)) {
401 &simplify::SimplifyCfg::new("remove-false-edges"),
402 &remove_uninit_drops::RemoveUninitDrops,
405 check_consts::post_drop_elaboration::check_live_drops(tcx, &body); // FIXME: make this a MIR lint
408 run_post_borrowck_cleanup_passes(tcx, &mut body);
409 assert!(body.phase == MirPhase::Deaggregated);
410 tcx.alloc_steal_mir(body)
413 /// After this series of passes, no lifetime analysis based on borrowing can be done.
414 fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
415 debug!("post_borrowck_cleanup({:?})", body.source.def_id());
417 let post_borrowck_cleanup: &[&dyn MirPass<'tcx>] = &[
418 // Remove all things only needed by analysis
419 &simplify_branches::SimplifyConstCondition::new("initial"),
420 &remove_noop_landing_pads::RemoveNoopLandingPads,
421 &cleanup_post_borrowck::CleanupNonCodegenStatements,
422 &simplify::SimplifyCfg::new("early-opt"),
423 // These next passes must be executed together
424 &add_call_guards::CriticalCallEdges,
425 &elaborate_drops::ElaborateDrops,
426 // This will remove extraneous landing pads which are no longer
427 // necessary as well as well as forcing any call in a non-unwinding
428 // function calling a possibly-unwinding function to abort the process.
429 &abort_unwinding_calls::AbortUnwindingCalls,
430 // AddMovesForPackedDrops needs to run after drop
432 &add_moves_for_packed_drops::AddMovesForPackedDrops,
433 // `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
434 // but before optimizations begin.
435 &deref_separator::Derefer,
436 &elaborate_box_derefs::ElaborateBoxDerefs,
437 &add_retag::AddRetag,
438 &lower_intrinsics::LowerIntrinsics,
439 &simplify::SimplifyCfg::new("elaborate-drops"),
440 // `Deaggregator` is conceptually part of MIR building, some backends rely on it happening
441 // and it can help optimizations.
442 &deaggregator::Deaggregator,
443 &Lint(const_prop_lint::ConstProp),
446 pm::run_passes(tcx, body, post_borrowck_cleanup);
449 fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
450 fn o1<T>(x: T) -> WithMinOptLevel<T> {
451 WithMinOptLevel(1, x)
454 // Lowering generator control-flow and variables has to happen before we do anything else
455 // to them. We run some optimizations before that, because they may be harder to do on the state
456 // machine than on MIR with async primitives.
461 &reveal_all::RevealAll, // has to be done before inlining, since inlined code is in RevealAll mode.
462 &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
463 &normalize_array_len::NormalizeArrayLen, // has to run after `slice::len` lowering
464 &unreachable_prop::UnreachablePropagation,
465 &uninhabited_enum_branching::UninhabitedEnumBranching,
466 &o1(simplify::SimplifyCfg::new("after-uninhabited-enum-branching")),
468 &generator::StateTransform,
472 assert!(body.phase == MirPhase::GeneratorsLowered);
474 // The main optimizations that we do on MIR.
479 &remove_storage_markers::RemoveStorageMarkers,
480 &remove_zsts::RemoveZsts,
481 &const_goto::ConstGoto,
482 &remove_unneeded_drops::RemoveUnneededDrops,
483 &match_branches::MatchBranchSimplification,
484 // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
485 &multiple_return_terminators::MultipleReturnTerminators,
486 &instcombine::InstCombine,
487 &separate_const_switch::SeparateConstSwitch,
489 // FIXME(#70073): This pass is responsible for both optimization as well as some lints.
490 &const_prop::ConstProp,
492 // Const-prop runs unconditionally, but doesn't mutate the MIR at mir-opt-level=0.
493 &const_debuginfo::ConstDebugInfo,
494 &o1(simplify_branches::SimplifyConstCondition::new("after-const-prop")),
495 &early_otherwise_branch::EarlyOtherwiseBranch,
496 &simplify_comparison_integral::SimplifyComparisonIntegral,
497 &simplify_try::SimplifyArmIdentity,
498 &simplify_try::SimplifyBranchSame,
499 &dead_store_elimination::DeadStoreElimination,
500 &dest_prop::DestinationPropagation,
501 &o1(simplify_branches::SimplifyConstCondition::new("final")),
502 &o1(remove_noop_landing_pads::RemoveNoopLandingPads),
503 &o1(simplify::SimplifyCfg::new("final")),
504 &nrvo::RenameReturnPlace,
505 &simplify::SimplifyLocals,
506 &multiple_return_terminators::MultipleReturnTerminators,
507 &deduplicate_blocks::DeduplicateBlocks,
508 // Some cleanup necessary at least for LLVM and potentially other codegen backends.
509 &add_call_guards::CriticalCallEdges,
510 &marker::PhaseChange(MirPhase::Optimized),
511 // Dump the end result for testing and debugging purposes.
512 &dump_mir::Marker("PreCodegen"),
517 /// Optimize the MIR and prepare it for codegen.
518 fn optimized_mir<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx Body<'tcx> {
519 let did = did.expect_local();
520 assert_eq!(ty::WithOptConstParam::try_lookup(did, tcx), None);
521 tcx.arena.alloc(inner_optimized_mir(tcx, did))
524 fn inner_optimized_mir(tcx: TyCtxt<'_>, did: LocalDefId) -> Body<'_> {
525 if tcx.is_constructor(did.to_def_id()) {
526 // There's no reason to run all of the MIR passes on constructors when
527 // we can just output the MIR we want directly. This also saves const
528 // qualification and borrow checking the trouble of special casing
530 return shim::build_adt_ctor(tcx, did.to_def_id());
533 match tcx.hir().body_const_context(did) {
534 // Run the `mir_for_ctfe` query, which depends on `mir_drops_elaborated_and_const_checked`
535 // which we are going to steal below. Thus we need to run `mir_for_ctfe` first, so it
536 // computes and caches its result.
537 Some(hir::ConstContext::ConstFn) => tcx.ensure().mir_for_ctfe(did),
539 Some(other) => panic!("do not use `optimized_mir` for constants: {:?}", other),
541 debug!("about to call mir_drops_elaborated...");
543 tcx.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(did)).steal();
544 debug!("body: {:#?}", body);
545 run_optimization_passes(tcx, &mut body);
547 debug_assert!(!body.has_free_regions(), "Free regions in optimized MIR");
552 /// Fetch all the promoteds of an item and prepare their MIR bodies to be ready for
553 /// constant evaluation once all substitutions become known.
554 fn promoted_mir<'tcx>(
556 def: ty::WithOptConstParam<LocalDefId>,
557 ) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
558 if tcx.is_constructor(def.did.to_def_id()) {
559 return tcx.arena.alloc(IndexVec::new());
562 let tainted_by_errors = tcx.mir_borrowck_opt_const_arg(def).tainted_by_errors;
563 let mut promoted = tcx.mir_promoted(def).1.steal();
565 for body in &mut promoted {
566 if let Some(error_reported) = tainted_by_errors {
567 body.tainted_by_errors = Some(error_reported);
569 run_post_borrowck_cleanup_passes(tcx, body);
572 debug_assert!(!promoted.has_free_regions(), "Free regions in promoted MIR");
574 tcx.arena.alloc(promoted)