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::FxIndexSet;
22 use rustc_data_structures::steal::Steal;
24 use rustc_hir::def_id::{DefId, LocalDefId};
25 use rustc_hir::intravisit::{self, 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<'_>, (): ()) -> FxIndexSet<LocalDefId> {
140 let mut set = FxIndexSet::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 FxIndexSet<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)
166 tcx.hir().visit_all_item_likes(&mut GatherCtors { tcx, set: &mut set }.as_deep_visitor());
171 fn mir_const_qualif(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> ConstQualifs {
172 let const_kind = tcx.hir().body_const_context(def.did);
174 // No need to const-check a non-const `fn`.
175 if const_kind.is_none() {
176 return Default::default();
179 // N.B., this `borrow()` is guaranteed to be valid (i.e., the value
180 // cannot yet be stolen), because `mir_promoted()`, which steals
181 // from `mir_const(), forces this query to execute before
182 // performing the steal.
183 let body = &tcx.mir_const(def).borrow();
185 if body.return_ty().references_error() {
186 tcx.sess.delay_span_bug(body.span, "mir_const_qualif: MIR had errors");
187 return Default::default();
190 let ccx = check_consts::ConstCx { body, tcx, const_kind, param_env: tcx.param_env(def.did) };
192 let mut validator = check_consts::check::Checker::new(&ccx);
193 validator.check_body();
195 // We return the qualifs in the return place for every MIR body, even though it is only used
196 // when deciding to promote a reference to a `const` for now.
197 validator.qualifs_in_return_place()
200 /// Make MIR ready for const evaluation. This is run on all MIR, not just on consts!
203 def: ty::WithOptConstParam<LocalDefId>,
204 ) -> &'tcx Steal<Body<'tcx>> {
205 if let Some(def) = def.try_upgrade(tcx) {
206 return tcx.mir_const(def);
209 // Unsafety check uses the raw mir, so make sure it is run.
210 if !tcx.sess.opts.debugging_opts.thir_unsafeck {
211 if let Some(param_did) = def.const_param_did {
212 tcx.ensure().unsafety_check_result_for_const_arg((def.did, param_did));
214 tcx.ensure().unsafety_check_result(def.did);
218 let mut body = tcx.mir_built(def).steal();
220 rustc_middle::mir::dump_mir(tcx, None, "mir_map", &0, &body, |_, _| Ok(()));
227 &Lint(check_packed_ref::CheckPackedRef),
228 &Lint(check_const_item_mutation::CheckConstItemMutation),
229 &Lint(function_item_references::FunctionItemReferences),
230 // What we need to do constant evaluation.
231 &simplify::SimplifyCfg::new("initial"),
232 &rustc_peek::SanityCheck, // Just a lint
233 &marker::PhaseChange(MirPhase::Const),
236 tcx.alloc_steal_mir(body)
239 /// Compute the main MIR body and the list of MIR bodies of the promoteds.
240 fn mir_promoted<'tcx>(
242 def: ty::WithOptConstParam<LocalDefId>,
243 ) -> (&'tcx Steal<Body<'tcx>>, &'tcx Steal<IndexVec<Promoted, Body<'tcx>>>) {
244 if let Some(def) = def.try_upgrade(tcx) {
245 return tcx.mir_promoted(def);
248 // Ensure that we compute the `mir_const_qualif` for constants at
249 // this point, before we steal the mir-const result.
250 // Also this means promotion can rely on all const checks having been done.
251 let _ = tcx.mir_const_qualif_opt_const_arg(def);
252 let mut body = tcx.mir_const(def).steal();
254 let mut required_consts = Vec::new();
255 let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
256 for (bb, bb_data) in traversal::reverse_postorder(&body) {
257 required_consts_visitor.visit_basic_block_data(bb, bb_data);
259 body.required_consts = required_consts;
261 // What we need to run borrowck etc.
262 let promote_pass = promote_consts::PromoteTemps::default();
268 &simplify::SimplifyCfg::new("promote-consts"),
269 &coverage::InstrumentCoverage,
273 let promoted = promote_pass.promoted_fragments.into_inner();
274 (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
277 /// Compute the MIR that is used during CTFE (and thus has no optimizations run on it)
278 fn mir_for_ctfe<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx Body<'tcx> {
279 let did = def_id.expect_local();
280 if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) {
281 tcx.mir_for_ctfe_of_const_arg(def)
283 tcx.arena.alloc(inner_mir_for_ctfe(tcx, ty::WithOptConstParam::unknown(did)))
287 /// Same as `mir_for_ctfe`, but used to get the MIR of a const generic parameter.
288 /// The docs on `WithOptConstParam` explain this a bit more, but the TLDR is that
289 /// we'd get cycle errors with `mir_for_ctfe`, because typeck would need to typeck
290 /// the const parameter while type checking the main body, which in turn would try
291 /// to type check the main body again.
292 fn mir_for_ctfe_of_const_arg<'tcx>(
294 (did, param_did): (LocalDefId, DefId),
295 ) -> &'tcx Body<'tcx> {
296 tcx.arena.alloc(inner_mir_for_ctfe(
298 ty::WithOptConstParam { did, const_param_did: Some(param_did) },
302 fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_> {
303 // FIXME: don't duplicate this between the optimized_mir/mir_for_ctfe queries
304 if tcx.is_constructor(def.did.to_def_id()) {
305 // There's no reason to run all of the MIR passes on constructors when
306 // we can just output the MIR we want directly. This also saves const
307 // qualification and borrow checking the trouble of special casing
309 return shim::build_adt_ctor(tcx, def.did.to_def_id());
314 .body_const_context(def.did)
315 .expect("mir_for_ctfe should not be used for runtime functions");
317 let mut body = tcx.mir_drops_elaborated_and_const_checked(def).borrow().clone();
320 // Do not const prop functions, either they get executed at runtime or exported to metadata,
321 // so we run const prop on them, or they don't, in which case we const evaluate some control
322 // flow paths of the function and any errors in those paths will get emitted as const eval
324 hir::ConstContext::ConstFn => {}
325 // Static items always get evaluated, so we can just let const eval see if any erroneous
326 // control flow paths get executed.
327 hir::ConstContext::Static(_) => {}
328 // Associated constants get const prop run so we detect common failure situations in the
329 // crate that defined the constant.
330 // Technically we want to not run on regular const items, but oli-obk doesn't know how to
331 // conveniently detect that at this point without looking at the HIR.
332 hir::ConstContext::Const => {
336 &[&const_prop::ConstProp, &marker::PhaseChange(MirPhase::Optimization)],
341 debug_assert!(!body.has_free_regions(), "Free regions in MIR for CTFE");
346 /// Obtain just the main MIR (no promoteds) and run some cleanups on it. This also runs
347 /// mir borrowck *before* doing so in order to ensure that borrowck can be run and doesn't
348 /// end up missing the source MIR due to stealing happening.
349 fn mir_drops_elaborated_and_const_checked<'tcx>(
351 def: ty::WithOptConstParam<LocalDefId>,
352 ) -> &'tcx Steal<Body<'tcx>> {
353 if let Some(def) = def.try_upgrade(tcx) {
354 return tcx.mir_drops_elaborated_and_const_checked(def);
357 // (Mir-)Borrowck uses `mir_promoted`, so we have to force it to
358 // execute before we can steal.
359 if let Some(param_did) = def.const_param_did {
360 tcx.ensure().mir_borrowck_const_arg((def.did, param_did));
362 tcx.ensure().mir_borrowck(def.did);
365 let is_fn_like = tcx.hir().get_by_def_id(def.did).fn_kind().is_some();
367 let did = def.did.to_def_id();
368 let def = ty::WithOptConstParam::unknown(did);
370 // Do not compute the mir call graph without said call graph actually being used.
371 if inline::Inline.is_enabled(&tcx.sess) {
372 let _ = tcx.mir_inliner_callees(ty::InstanceDef::Item(def));
376 let (body, _) = tcx.mir_promoted(def);
377 let mut body = body.steal();
380 pm::run_passes(tcx, &mut body, &[&remove_false_edges::RemoveFalseEdges]);
382 // Do a little drop elaboration before const-checking if `const_precise_live_drops` is enabled.
383 if check_consts::post_drop_elaboration::checking_enabled(&ConstCx::new(tcx, &body)) {
388 &simplify::SimplifyCfg::new("remove-false-edges"),
389 &remove_uninit_drops::RemoveUninitDrops,
392 check_consts::post_drop_elaboration::check_live_drops(tcx, &body); // FIXME: make this a MIR lint
395 run_post_borrowck_cleanup_passes(tcx, &mut body);
396 assert!(body.phase == MirPhase::DropLowering);
397 tcx.alloc_steal_mir(body)
400 /// After this series of passes, no lifetime analysis based on borrowing can be done.
401 fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
402 debug!("post_borrowck_cleanup({:?})", body.source.def_id());
404 let post_borrowck_cleanup: &[&dyn MirPass<'tcx>] = &[
405 // Remove all things only needed by analysis
406 &simplify_branches::SimplifyConstCondition::new("initial"),
407 &remove_noop_landing_pads::RemoveNoopLandingPads,
408 &cleanup_post_borrowck::CleanupNonCodegenStatements,
409 &simplify::SimplifyCfg::new("early-opt"),
410 // These next passes must be executed together
411 &add_call_guards::CriticalCallEdges,
412 &elaborate_drops::ElaborateDrops,
413 // This will remove extraneous landing pads which are no longer
414 // necessary as well as well as forcing any call in a non-unwinding
415 // function calling a possibly-unwinding function to abort the process.
416 &abort_unwinding_calls::AbortUnwindingCalls,
417 // AddMovesForPackedDrops needs to run after drop
419 &add_moves_for_packed_drops::AddMovesForPackedDrops,
420 // `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
421 // but before optimizations begin.
422 &add_retag::AddRetag,
423 &lower_intrinsics::LowerIntrinsics,
424 &simplify::SimplifyCfg::new("elaborate-drops"),
425 // `Deaggregator` is conceptually part of MIR building, some backends rely on it happening
426 // and it can help optimizations.
427 &deaggregator::Deaggregator,
430 pm::run_passes(tcx, body, post_borrowck_cleanup);
433 fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
434 fn o1<T>(x: T) -> WithMinOptLevel<T> {
435 WithMinOptLevel(1, x)
438 // Lowering generator control-flow and variables has to happen before we do anything else
439 // to them. We run some optimizations before that, because they may be harder to do on the state
440 // machine than on MIR with async primitives.
445 &reveal_all::RevealAll, // has to be done before inlining, since inlined code is in RevealAll mode.
446 &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
447 &normalize_array_len::NormalizeArrayLen, // has to run after `slice::len` lowering
448 &unreachable_prop::UnreachablePropagation,
449 &uninhabited_enum_branching::UninhabitedEnumBranching,
450 &o1(simplify::SimplifyCfg::new("after-uninhabited-enum-branching")),
452 &generator::StateTransform,
456 assert!(body.phase == MirPhase::GeneratorLowering);
458 // The main optimizations that we do on MIR.
463 &remove_storage_markers::RemoveStorageMarkers,
464 &remove_zsts::RemoveZsts,
465 &const_goto::ConstGoto,
466 &remove_unneeded_drops::RemoveUnneededDrops,
467 &match_branches::MatchBranchSimplification,
468 // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
469 &multiple_return_terminators::MultipleReturnTerminators,
470 &instcombine::InstCombine,
471 &separate_const_switch::SeparateConstSwitch,
473 // FIXME(#70073): This pass is responsible for both optimization as well as some lints.
474 &const_prop::ConstProp,
476 // Const-prop runs unconditionally, but doesn't mutate the MIR at mir-opt-level=0.
477 &o1(simplify_branches::SimplifyConstCondition::new("after-const-prop")),
478 &early_otherwise_branch::EarlyOtherwiseBranch,
479 &simplify_comparison_integral::SimplifyComparisonIntegral,
480 &simplify_try::SimplifyArmIdentity,
481 &simplify_try::SimplifyBranchSame,
482 &dest_prop::DestinationPropagation,
483 &o1(simplify_branches::SimplifyConstCondition::new("final")),
484 &o1(remove_noop_landing_pads::RemoveNoopLandingPads),
485 &o1(simplify::SimplifyCfg::new("final")),
486 &nrvo::RenameReturnPlace,
487 &const_debuginfo::ConstDebugInfo,
488 &simplify::SimplifyLocals,
489 &multiple_return_terminators::MultipleReturnTerminators,
490 &deduplicate_blocks::DeduplicateBlocks,
491 // Some cleanup necessary at least for LLVM and potentially other codegen backends.
492 &add_call_guards::CriticalCallEdges,
493 &marker::PhaseChange(MirPhase::Optimization),
494 // Dump the end result for testing and debugging purposes.
495 &dump_mir::Marker("PreCodegen"),
500 /// Optimize the MIR and prepare it for codegen.
501 fn optimized_mir<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx Body<'tcx> {
502 let did = did.expect_local();
503 assert_eq!(ty::WithOptConstParam::try_lookup(did, tcx), None);
504 tcx.arena.alloc(inner_optimized_mir(tcx, did))
507 fn inner_optimized_mir(tcx: TyCtxt<'_>, did: LocalDefId) -> Body<'_> {
508 if tcx.is_constructor(did.to_def_id()) {
509 // There's no reason to run all of the MIR passes on constructors when
510 // we can just output the MIR we want directly. This also saves const
511 // qualification and borrow checking the trouble of special casing
513 return shim::build_adt_ctor(tcx, did.to_def_id());
516 match tcx.hir().body_const_context(did) {
517 // Run the `mir_for_ctfe` query, which depends on `mir_drops_elaborated_and_const_checked`
518 // which we are going to steal below. Thus we need to run `mir_for_ctfe` first, so it
519 // computes and caches its result.
520 Some(hir::ConstContext::ConstFn) => tcx.ensure().mir_for_ctfe(did),
522 Some(other) => panic!("do not use `optimized_mir` for constants: {:?}", other),
525 tcx.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(did)).steal();
526 run_optimization_passes(tcx, &mut body);
528 debug_assert!(!body.has_free_regions(), "Free regions in optimized MIR");
533 /// Fetch all the promoteds of an item and prepare their MIR bodies to be ready for
534 /// constant evaluation once all substitutions become known.
535 fn promoted_mir<'tcx>(
537 def: ty::WithOptConstParam<LocalDefId>,
538 ) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
539 if tcx.is_constructor(def.did.to_def_id()) {
540 return tcx.arena.alloc(IndexVec::new());
543 if let Some(param_did) = def.const_param_did {
544 tcx.ensure().mir_borrowck_const_arg((def.did, param_did));
546 tcx.ensure().mir_borrowck(def.did);
548 let (_, promoted) = tcx.mir_promoted(def);
549 let mut promoted = promoted.steal();
551 for body in &mut promoted {
552 run_post_borrowck_cleanup_passes(tcx, body);
555 debug_assert!(!promoted.has_free_regions(), "Free regions in promoted MIR");
557 tcx.arena.alloc(promoted)