compiler/rustc_mir_transform/src/lib.rs

   1 #![allow(rustc::potential_query_instability)]
   2 #![feature(box_patterns)]
   3 #![feature(let_chains)]
   4 #![feature(map_try_insert)]
   5 #![feature(min_specialization)]
   6 #![feature(never_type)]
   7 #![feature(once_cell)]
   8 #![feature(option_get_or_insert_default)]
   9 #![feature(trusted_step)]
  10 #![feature(try_blocks)]
  11 #![feature(yeet_expr)]
  12 #![feature(if_let_guard)]
  13 #![recursion_limit = "256"]
  14
  15 #[macro_use]
  16 extern crate tracing;
  17 #[macro_use]
  18 extern crate rustc_middle;
  19
  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;
  24 use rustc_hir as hir;
  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, Constant, LocalDecl, MirPass, MirPhase, Operand,
  31     Place, ProjectionElem, Promoted, RuntimePhase, Rvalue, SourceInfo, Statement, StatementKind,
  32     TerminatorKind,
  33 };
  34 use rustc_middle::ty::query::Providers;
  35 use rustc_middle::ty::{self, TyCtxt, TypeVisitable};
  36 use rustc_span::sym;
  37
  38 #[macro_use]
  39 mod pass_manager;
  40
  41 use pass_manager::{self as pm, Lint, MirLint, WithMinOptLevel};
  42
  43 mod abort_unwinding_calls;
  44 mod add_call_guards;
  45 mod add_moves_for_packed_drops;
  46 mod add_retag;
  47 mod check_const_item_mutation;
  48 mod check_packed_ref;
  49 pub mod check_unsafety;
  50 // This pass is public to allow external drivers to perform MIR cleanup
  51 pub mod cleanup_post_borrowck;
  52 mod const_debuginfo;
  53 mod const_goto;
  54 mod const_prop;
  55 mod const_prop_lint;
  56 mod coverage;
  57 mod dataflow_const_prop;
  58 mod dead_store_elimination;
  59 mod deaggregator;
  60 mod deduce_param_attrs;
  61 mod deduplicate_blocks;
  62 mod deref_separator;
  63 mod dest_prop;
  64 pub mod dump_mir;
  65 mod early_otherwise_branch;
  66 mod elaborate_box_derefs;
  67 mod elaborate_drops;
  68 mod ffi_unwind_calls;
  69 mod function_item_references;
  70 mod generator;
  71 mod inline;
  72 mod instcombine;
  73 mod lower_intrinsics;
  74 mod lower_slice_len;
  75 mod match_branches;
  76 mod multiple_return_terminators;
  77 mod normalize_array_len;
  78 mod nrvo;
  79 // This pass is public to allow external drivers to perform MIR cleanup
  80 pub mod remove_false_edges;
  81 mod remove_noop_landing_pads;
  82 mod remove_storage_markers;
  83 mod remove_uninit_drops;
  84 mod remove_unneeded_drops;
  85 mod remove_zsts;
  86 mod required_consts;
  87 mod reveal_all;
  88 mod separate_const_switch;
  89 mod shim;
  90 // This pass is public to allow external drivers to perform MIR cleanup
  91 pub mod simplify;
  92 mod simplify_branches;
  93 mod simplify_comparison_integral;
  94 mod simplify_try;
  95 mod uninhabited_enum_branching;
  96 mod unreachable_prop;
  97
  98 use rustc_const_eval::transform::check_consts::{self, ConstCx};
  99 use rustc_const_eval::transform::promote_consts;
 100 use rustc_const_eval::transform::validate;
 101 use rustc_mir_dataflow::rustc_peek;
 102
 103 pub fn provide(providers: &mut Providers) {
 104     check_unsafety::provide(providers);
 105     check_packed_ref::provide(providers);
 106     coverage::query::provide(providers);
 107     ffi_unwind_calls::provide(providers);
 108     shim::provide(providers);
 109     *providers = Providers {
 110         mir_keys,
 111         mir_const,
 112         mir_const_qualif: |tcx, def_id| {
 113             let def_id = def_id.expect_local();
 114             if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
 115                 tcx.mir_const_qualif_const_arg(def)
 116             } else {
 117                 mir_const_qualif(tcx, ty::WithOptConstParam::unknown(def_id))
 118             }
 119         },
 120         mir_const_qualif_const_arg: |tcx, (did, param_did)| {
 121             mir_const_qualif(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
 122         },
 123         mir_promoted,
 124         mir_drops_elaborated_and_const_checked,
 125         mir_for_ctfe,
 126         mir_for_ctfe_of_const_arg,
 127         optimized_mir,
 128         is_mir_available,
 129         is_ctfe_mir_available: |tcx, did| is_mir_available(tcx, did),
 130         mir_callgraph_reachable: inline::cycle::mir_callgraph_reachable,
 131         mir_inliner_callees: inline::cycle::mir_inliner_callees,
 132         promoted_mir: |tcx, def_id| {
 133             let def_id = def_id.expect_local();
 134             if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
 135                 tcx.promoted_mir_of_const_arg(def)
 136             } else {
 137                 promoted_mir(tcx, ty::WithOptConstParam::unknown(def_id))
 138             }
 139         },
 140         promoted_mir_of_const_arg: |tcx, (did, param_did)| {
 141             promoted_mir(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
 142         },
 143         deduced_param_attrs: deduce_param_attrs::deduced_param_attrs,
 144         ..*providers
 145     };
 146 }
 147
 148 fn remap_mir_for_const_eval_select<'tcx>(
 149     tcx: TyCtxt<'tcx>,
 150     mut body: Body<'tcx>,
 151     context: hir::Constness,
 152 ) -> Body<'tcx> {
 153     for bb in body.basic_blocks.as_mut().iter_mut() {
 154         let terminator = bb.terminator.as_mut().expect("invalid terminator");
 155         match terminator.kind {
 156             TerminatorKind::Call {
 157                 func: Operand::Constant(box Constant { ref literal, .. }),
 158                 ref mut args,
 159                 destination,
 160                 target,
 161                 cleanup,
 162                 fn_span,
 163                 ..
 164             } if let ty::FnDef(def_id, _) = *literal.ty().kind()
 165                 && tcx.item_name(def_id) == sym::const_eval_select
 166                 && tcx.is_intrinsic(def_id) =>
 167             {
 168                 let [tupled_args, called_in_const, called_at_rt]: [_; 3] = std::mem::take(args).try_into().unwrap();
 169                 let ty = tupled_args.ty(&body.local_decls, tcx);
 170                 let fields = ty.tuple_fields();
 171                 let num_args = fields.len();
 172                 let func = if context == hir::Constness::Const { called_in_const } else { called_at_rt };
 173                 let (method, place): (fn(Place<'tcx>) -> Operand<'tcx>, Place<'tcx>) = match tupled_args {
 174                     Operand::Constant(_) => {
 175                         // there is no good way of extracting a tuple arg from a constant (const generic stuff)
 176                         // so we just create a temporary and deconstruct that.
 177                         let local = body.local_decls.push(LocalDecl::new(ty, fn_span));
 178                         bb.statements.push(Statement {
 179                             source_info: SourceInfo::outermost(fn_span),
 180                             kind: StatementKind::Assign(Box::new((local.into(), Rvalue::Use(tupled_args.clone())))),
 181                         });
 182                         (Operand::Move, local.into())
 183                     }
 184                     Operand::Move(place) => (Operand::Move, place),
 185                     Operand::Copy(place) => (Operand::Copy, place),
 186                 };
 187                 let place_elems = place.projection;
 188                 let arguments = (0..num_args).map(|x| {
 189                     let mut place_elems = place_elems.to_vec();
 190                     place_elems.push(ProjectionElem::Field(x.into(), fields[x]));
 191                     let projection = tcx.intern_place_elems(&place_elems);
 192                     let place = Place {
 193                         local: place.local,
 194                         projection,
 195                     };
 196                     method(place)
 197                 }).collect();
 198                 terminator.kind = TerminatorKind::Call { func, args: arguments, destination, target, cleanup, from_hir_call: false, fn_span };
 199             }
 200             _ => {}
 201         }
 202     }
 203     body
 204 }
 205
 206 fn is_mir_available(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
 207     let def_id = def_id.expect_local();
 208     tcx.mir_keys(()).contains(&def_id)
 209 }
 210
 211 /// Finds the full set of `DefId`s within the current crate that have
 212 /// MIR associated with them.
 213 fn mir_keys(tcx: TyCtxt<'_>, (): ()) -> FxIndexSet<LocalDefId> {
 214     let mut set = FxIndexSet::default();
 215
 216     // All body-owners have MIR associated with them.
 217     set.extend(tcx.hir().body_owners());
 218
 219     // Additionally, tuple struct/variant constructors have MIR, but
 220     // they don't have a BodyId, so we need to build them separately.
 221     struct GatherCtors<'a, 'tcx> {
 222         tcx: TyCtxt<'tcx>,
 223         set: &'a mut FxIndexSet<LocalDefId>,
 224     }
 225     impl<'tcx> Visitor<'tcx> for GatherCtors<'_, 'tcx> {
 226         fn visit_variant_data(&mut self, v: &'tcx hir::VariantData<'tcx>) {
 227             if let hir::VariantData::Tuple(_, hir_id) = *v {
 228                 self.set.insert(self.tcx.hir().local_def_id(hir_id));
 229             }
 230             intravisit::walk_struct_def(self, v)
 231         }
 232     }
 233     tcx.hir().visit_all_item_likes_in_crate(&mut GatherCtors { tcx, set: &mut set });
 234
 235     set
 236 }
 237
 238 fn mir_const_qualif(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> ConstQualifs {
 239     let const_kind = tcx.hir().body_const_context(def.did);
 240
 241     // No need to const-check a non-const `fn`.
 242     if const_kind.is_none() {
 243         return Default::default();
 244     }
 245
 246     // N.B., this `borrow()` is guaranteed to be valid (i.e., the value
 247     // cannot yet be stolen), because `mir_promoted()`, which steals
 248     // from `mir_const(), forces this query to execute before
 249     // performing the steal.
 250     let body = &tcx.mir_const(def).borrow();
 251
 252     if body.return_ty().references_error() {
 253         tcx.sess.delay_span_bug(body.span, "mir_const_qualif: MIR had errors");
 254         return Default::default();
 255     }
 256
 257     let ccx = check_consts::ConstCx { body, tcx, const_kind, param_env: tcx.param_env(def.did) };
 258
 259     let mut validator = check_consts::check::Checker::new(&ccx);
 260     validator.check_body();
 261
 262     // We return the qualifs in the return place for every MIR body, even though it is only used
 263     // when deciding to promote a reference to a `const` for now.
 264     validator.qualifs_in_return_place()
 265 }
 266
 267 /// Make MIR ready for const evaluation. This is run on all MIR, not just on consts!
 268 /// FIXME(oli-obk): it's unclear whether we still need this phase (and its corresponding query).
 269 /// We used to have this for pre-miri MIR based const eval.
 270 fn mir_const<'tcx>(
 271     tcx: TyCtxt<'tcx>,
 272     def: ty::WithOptConstParam<LocalDefId>,
 273 ) -> &'tcx Steal<Body<'tcx>> {
 274     if let Some(def) = def.try_upgrade(tcx) {
 275         return tcx.mir_const(def);
 276     }
 277
 278     // Unsafety check uses the raw mir, so make sure it is run.
 279     if !tcx.sess.opts.unstable_opts.thir_unsafeck {
 280         if let Some(param_did) = def.const_param_did {
 281             tcx.ensure().unsafety_check_result_for_const_arg((def.did, param_did));
 282         } else {
 283             tcx.ensure().unsafety_check_result(def.did);
 284         }
 285     }
 286
 287     // has_ffi_unwind_calls query uses the raw mir, so make sure it is run.
 288     tcx.ensure().has_ffi_unwind_calls(def.did);
 289
 290     let mut body = tcx.mir_built(def).steal();
 291
 292     pass_manager::dump_mir_for_phase_change(tcx, &body);
 293
 294     pm::run_passes(
 295         tcx,
 296         &mut body,
 297         &[
 298             // MIR-level lints.
 299             &Lint(check_packed_ref::CheckPackedRef),
 300             &Lint(check_const_item_mutation::CheckConstItemMutation),
 301             &Lint(function_item_references::FunctionItemReferences),
 302             // What we need to do constant evaluation.
 303             &simplify::SimplifyCfg::new("initial"),
 304             &rustc_peek::SanityCheck, // Just a lint
 305         ],
 306         None,
 307     );
 308     tcx.alloc_steal_mir(body)
 309 }
 310
 311 /// Compute the main MIR body and the list of MIR bodies of the promoteds.
 312 fn mir_promoted<'tcx>(
 313     tcx: TyCtxt<'tcx>,
 314     def: ty::WithOptConstParam<LocalDefId>,
 315 ) -> (&'tcx Steal<Body<'tcx>>, &'tcx Steal<IndexVec<Promoted, Body<'tcx>>>) {
 316     if let Some(def) = def.try_upgrade(tcx) {
 317         return tcx.mir_promoted(def);
 318     }
 319
 320     // Ensure that we compute the `mir_const_qualif` for constants at
 321     // this point, before we steal the mir-const result.
 322     // Also this means promotion can rely on all const checks having been done.
 323     let const_qualifs = tcx.mir_const_qualif_opt_const_arg(def);
 324     let mut body = tcx.mir_const(def).steal();
 325     if let Some(error_reported) = const_qualifs.tainted_by_errors {
 326         body.tainted_by_errors = Some(error_reported);
 327     }
 328
 329     let mut required_consts = Vec::new();
 330     let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
 331     for (bb, bb_data) in traversal::reverse_postorder(&body) {
 332         required_consts_visitor.visit_basic_block_data(bb, bb_data);
 333     }
 334     body.required_consts = required_consts;
 335
 336     // What we need to run borrowck etc.
 337     let promote_pass = promote_consts::PromoteTemps::default();
 338     pm::run_passes(
 339         tcx,
 340         &mut body,
 341         &[
 342             &promote_pass,
 343             &simplify::SimplifyCfg::new("promote-consts"),
 344             &coverage::InstrumentCoverage,
 345         ],
 346         Some(MirPhase::Analysis(AnalysisPhase::Initial)),
 347     );
 348
 349     let promoted = promote_pass.promoted_fragments.into_inner();
 350     (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
 351 }
 352
 353 /// Compute the MIR that is used during CTFE (and thus has no optimizations run on it)
 354 fn mir_for_ctfe<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx Body<'tcx> {
 355     let did = def_id.expect_local();
 356     if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) {
 357         tcx.mir_for_ctfe_of_const_arg(def)
 358     } else {
 359         tcx.arena.alloc(inner_mir_for_ctfe(tcx, ty::WithOptConstParam::unknown(did)))
 360     }
 361 }
 362
 363 /// Same as `mir_for_ctfe`, but used to get the MIR of a const generic parameter.
 364 /// The docs on `WithOptConstParam` explain this a bit more, but the TLDR is that
 365 /// we'd get cycle errors with `mir_for_ctfe`, because typeck would need to typeck
 366 /// the const parameter while type checking the main body, which in turn would try
 367 /// to type check the main body again.
 368 fn mir_for_ctfe_of_const_arg<'tcx>(
 369     tcx: TyCtxt<'tcx>,
 370     (did, param_did): (LocalDefId, DefId),
 371 ) -> &'tcx Body<'tcx> {
 372     tcx.arena.alloc(inner_mir_for_ctfe(
 373         tcx,
 374         ty::WithOptConstParam { did, const_param_did: Some(param_did) },
 375     ))
 376 }
 377
 378 fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_> {
 379     // FIXME: don't duplicate this between the optimized_mir/mir_for_ctfe queries
 380     if tcx.is_constructor(def.did.to_def_id()) {
 381         // There's no reason to run all of the MIR passes on constructors when
 382         // we can just output the MIR we want directly. This also saves const
 383         // qualification and borrow checking the trouble of special casing
 384         // constructors.
 385         return shim::build_adt_ctor(tcx, def.did.to_def_id());
 386     }
 387
 388     let context = tcx
 389         .hir()
 390         .body_const_context(def.did)
 391         .expect("mir_for_ctfe should not be used for runtime functions");
 392
 393     let body = tcx.mir_drops_elaborated_and_const_checked(def).borrow().clone();
 394
 395     let mut body = remap_mir_for_const_eval_select(tcx, body, hir::Constness::Const);
 396
 397     match context {
 398         // Do not const prop functions, either they get executed at runtime or exported to metadata,
 399         // so we run const prop on them, or they don't, in which case we const evaluate some control
 400         // flow paths of the function and any errors in those paths will get emitted as const eval
 401         // errors.
 402         hir::ConstContext::ConstFn => {}
 403         // Static items always get evaluated, so we can just let const eval see if any erroneous
 404         // control flow paths get executed.
 405         hir::ConstContext::Static(_) => {}
 406         // Associated constants get const prop run so we detect common failure situations in the
 407         // crate that defined the constant.
 408         // Technically we want to not run on regular const items, but oli-obk doesn't know how to
 409         // conveniently detect that at this point without looking at the HIR.
 410         hir::ConstContext::Const => {
 411             pm::run_passes(
 412                 tcx,
 413                 &mut body,
 414                 &[&const_prop::ConstProp],
 415                 Some(MirPhase::Runtime(RuntimePhase::Optimized)),
 416             );
 417         }
 418     }
 419
 420     debug_assert!(!body.has_free_regions(), "Free regions in MIR for CTFE");
 421
 422     body
 423 }
 424
 425 /// Obtain just the main MIR (no promoteds) and run some cleanups on it. This also runs
 426 /// mir borrowck *before* doing so in order to ensure that borrowck can be run and doesn't
 427 /// end up missing the source MIR due to stealing happening.
 428 fn mir_drops_elaborated_and_const_checked<'tcx>(
 429     tcx: TyCtxt<'tcx>,
 430     def: ty::WithOptConstParam<LocalDefId>,
 431 ) -> &'tcx Steal<Body<'tcx>> {
 432     if let Some(def) = def.try_upgrade(tcx) {
 433         return tcx.mir_drops_elaborated_and_const_checked(def);
 434     }
 435
 436     let mir_borrowck = tcx.mir_borrowck_opt_const_arg(def);
 437
 438     let is_fn_like = tcx.def_kind(def.did).is_fn_like();
 439     if is_fn_like {
 440         let did = def.did.to_def_id();
 441         let def = ty::WithOptConstParam::unknown(did);
 442
 443         // Do not compute the mir call graph without said call graph actually being used.
 444         if inline::Inline.is_enabled(&tcx.sess) {
 445             let _ = tcx.mir_inliner_callees(ty::InstanceDef::Item(def));
 446         }
 447     }
 448
 449     let (body, _) = tcx.mir_promoted(def);
 450     let mut body = body.steal();
 451     if let Some(error_reported) = mir_borrowck.tainted_by_errors {
 452         body.tainted_by_errors = Some(error_reported);
 453     }
 454
 455     run_analysis_to_runtime_passes(tcx, &mut body);
 456
 457     tcx.alloc_steal_mir(body)
 458 }
 459
 460 fn run_analysis_to_runtime_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
 461     assert!(body.phase == MirPhase::Analysis(AnalysisPhase::Initial));
 462     let did = body.source.def_id();
 463
 464     debug!("analysis_mir_cleanup({:?})", did);
 465     run_analysis_cleanup_passes(tcx, body);
 466     assert!(body.phase == MirPhase::Analysis(AnalysisPhase::PostCleanup));
 467
 468     // Do a little drop elaboration before const-checking if `const_precise_live_drops` is enabled.
 469     if check_consts::post_drop_elaboration::checking_enabled(&ConstCx::new(tcx, &body)) {
 470         pm::run_passes(
 471             tcx,
 472             body,
 473             &[
 474                 &remove_uninit_drops::RemoveUninitDrops,
 475                 &simplify::SimplifyCfg::new("remove-false-edges"),
 476             ],
 477             None,
 478         );
 479         check_consts::post_drop_elaboration::check_live_drops(tcx, &body); // FIXME: make this a MIR lint
 480     }
 481
 482     debug!("runtime_mir_lowering({:?})", did);
 483     run_runtime_lowering_passes(tcx, body);
 484     assert!(body.phase == MirPhase::Runtime(RuntimePhase::Initial));
 485
 486     debug!("runtime_mir_cleanup({:?})", did);
 487     run_runtime_cleanup_passes(tcx, body);
 488     assert!(body.phase == MirPhase::Runtime(RuntimePhase::PostCleanup));
 489 }
 490
 491 // FIXME(JakobDegen): Can we make these lists of passes consts?
 492
 493 /// After this series of passes, no lifetime analysis based on borrowing can be done.
 494 fn run_analysis_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
 495     let passes: &[&dyn MirPass<'tcx>] = &[
 496         &remove_false_edges::RemoveFalseEdges,
 497         &simplify_branches::SimplifyConstCondition::new("initial"),
 498         &remove_noop_landing_pads::RemoveNoopLandingPads,
 499         &cleanup_post_borrowck::CleanupNonCodegenStatements,
 500         &simplify::SimplifyCfg::new("early-opt"),
 501         &deref_separator::Derefer,
 502     ];
 503
 504     pm::run_passes(tcx, body, passes, Some(MirPhase::Analysis(AnalysisPhase::PostCleanup)));
 505 }
 506
 507 /// Returns the sequence of passes that lowers analysis to runtime MIR.
 508 fn run_runtime_lowering_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
 509     let passes: &[&dyn MirPass<'tcx>] = &[
 510         // These next passes must be executed together
 511         &add_call_guards::CriticalCallEdges,
 512         &elaborate_drops::ElaborateDrops,
 513         // This will remove extraneous landing pads which are no longer
 514         // necessary as well as well as forcing any call in a non-unwinding
 515         // function calling a possibly-unwinding function to abort the process.
 516         &abort_unwinding_calls::AbortUnwindingCalls,
 517         // AddMovesForPackedDrops needs to run after drop
 518         // elaboration.
 519         &add_moves_for_packed_drops::AddMovesForPackedDrops,
 520         // `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
 521         // but before optimizations begin.
 522         &elaborate_box_derefs::ElaborateBoxDerefs,
 523         &generator::StateTransform,
 524         &add_retag::AddRetag,
 525         // Deaggregator is necessary for const prop. We may want to consider implementing
 526         // CTFE support for aggregates.
 527         &deaggregator::Deaggregator,
 528         &Lint(const_prop_lint::ConstProp),
 529     ];
 530     pm::run_passes_no_validate(tcx, body, passes, Some(MirPhase::Runtime(RuntimePhase::Initial)));
 531 }
 532
 533 /// Returns the sequence of passes that do the initial cleanup of runtime MIR.
 534 fn run_runtime_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
 535     let passes: &[&dyn MirPass<'tcx>] = &[
 536         &elaborate_box_derefs::ElaborateBoxDerefs,
 537         &lower_intrinsics::LowerIntrinsics,
 538         &simplify::SimplifyCfg::new("elaborate-drops"),
 539     ];
 540
 541     pm::run_passes(tcx, body, passes, Some(MirPhase::Runtime(RuntimePhase::PostCleanup)));
 542 }
 543
 544 fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
 545     fn o1<T>(x: T) -> WithMinOptLevel<T> {
 546         WithMinOptLevel(1, x)
 547     }
 548
 549     // The main optimizations that we do on MIR.
 550     pm::run_passes(
 551         tcx,
 552         body,
 553         &[
 554             &reveal_all::RevealAll, // has to be done before inlining, since inlined code is in RevealAll mode.
 555             &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
 556             &normalize_array_len::NormalizeArrayLen, // has to run after `slice::len` lowering
 557             &unreachable_prop::UnreachablePropagation,
 558             &uninhabited_enum_branching::UninhabitedEnumBranching,
 559             &o1(simplify::SimplifyCfg::new("after-uninhabited-enum-branching")),
 560             &inline::Inline,
 561             &remove_storage_markers::RemoveStorageMarkers,
 562             &remove_zsts::RemoveZsts,
 563             &const_goto::ConstGoto,
 564             &remove_unneeded_drops::RemoveUnneededDrops,
 565             &match_branches::MatchBranchSimplification,
 566             // inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
 567             &multiple_return_terminators::MultipleReturnTerminators,
 568             &instcombine::InstCombine,
 569             &separate_const_switch::SeparateConstSwitch,
 570             //
 571             // FIXME(#70073): This pass is responsible for both optimization as well as some lints.
 572             &const_prop::ConstProp,
 573             &dataflow_const_prop::DataflowConstProp,
 574             //
 575             // Const-prop runs unconditionally, but doesn't mutate the MIR at mir-opt-level=0.
 576             &const_debuginfo::ConstDebugInfo,
 577             &o1(simplify_branches::SimplifyConstCondition::new("after-const-prop")),
 578             &early_otherwise_branch::EarlyOtherwiseBranch,
 579             &simplify_comparison_integral::SimplifyComparisonIntegral,
 580             &simplify_try::SimplifyArmIdentity,
 581             &simplify_try::SimplifyBranchSame,
 582             &dead_store_elimination::DeadStoreElimination,
 583             &dest_prop::DestinationPropagation,
 584             &o1(simplify_branches::SimplifyConstCondition::new("final")),
 585             &o1(remove_noop_landing_pads::RemoveNoopLandingPads),
 586             &o1(simplify::SimplifyCfg::new("final")),
 587             &nrvo::RenameReturnPlace,
 588             &simplify::SimplifyLocals,
 589             &multiple_return_terminators::MultipleReturnTerminators,
 590             &deduplicate_blocks::DeduplicateBlocks,
 591             // Some cleanup necessary at least for LLVM and potentially other codegen backends.
 592             &add_call_guards::CriticalCallEdges,
 593             // Dump the end result for testing and debugging purposes.
 594             &dump_mir::Marker("PreCodegen"),
 595         ],
 596         Some(MirPhase::Runtime(RuntimePhase::Optimized)),
 597     );
 598 }
 599
 600 /// Optimize the MIR and prepare it for codegen.
 601 fn optimized_mir<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx Body<'tcx> {
 602     let did = did.expect_local();
 603     assert_eq!(ty::WithOptConstParam::try_lookup(did, tcx), None);
 604     tcx.arena.alloc(inner_optimized_mir(tcx, did))
 605 }
 606
 607 fn inner_optimized_mir(tcx: TyCtxt<'_>, did: LocalDefId) -> Body<'_> {
 608     if tcx.is_constructor(did.to_def_id()) {
 609         // There's no reason to run all of the MIR passes on constructors when
 610         // we can just output the MIR we want directly. This also saves const
 611         // qualification and borrow checking the trouble of special casing
 612         // constructors.
 613         return shim::build_adt_ctor(tcx, did.to_def_id());
 614     }
 615
 616     match tcx.hir().body_const_context(did) {
 617         // Run the `mir_for_ctfe` query, which depends on `mir_drops_elaborated_and_const_checked`
 618         // which we are going to steal below. Thus we need to run `mir_for_ctfe` first, so it
 619         // computes and caches its result.
 620         Some(hir::ConstContext::ConstFn) => tcx.ensure().mir_for_ctfe(did),
 621         None => {}
 622         Some(other) => panic!("do not use `optimized_mir` for constants: {:?}", other),
 623     }
 624     debug!("about to call mir_drops_elaborated...");
 625     let body =
 626         tcx.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(did)).steal();
 627     let mut body = remap_mir_for_const_eval_select(tcx, body, hir::Constness::NotConst);
 628     debug!("body: {:#?}", body);
 629     run_optimization_passes(tcx, &mut body);
 630
 631     debug_assert!(!body.has_free_regions(), "Free regions in optimized MIR");
 632
 633     body
 634 }
 635
 636 /// Fetch all the promoteds of an item and prepare their MIR bodies to be ready for
 637 /// constant evaluation once all substitutions become known.
 638 fn promoted_mir<'tcx>(
 639     tcx: TyCtxt<'tcx>,
 640     def: ty::WithOptConstParam<LocalDefId>,
 641 ) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
 642     if tcx.is_constructor(def.did.to_def_id()) {
 643         return tcx.arena.alloc(IndexVec::new());
 644     }
 645
 646     let tainted_by_errors = tcx.mir_borrowck_opt_const_arg(def).tainted_by_errors;
 647     let mut promoted = tcx.mir_promoted(def).1.steal();
 648
 649     for body in &mut promoted {
 650         if let Some(error_reported) = tainted_by_errors {
 651             body.tainted_by_errors = Some(error_reported);
 652         }
 653         run_analysis_to_runtime_passes(tcx, body);
 654     }
 655
 656     debug_assert!(!promoted.has_free_regions(), "Free regions in promoted MIR");
 657
 658     tcx.arena.alloc(promoted)
 659 }