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Diffstat (limited to 'compiler/rustc_mir_transform/src/lib.rs')
| -rw-r--r-- | compiler/rustc_mir_transform/src/lib.rs | 632 |
1 files changed, 632 insertions, 0 deletions
diff --git a/compiler/rustc_mir_transform/src/lib.rs b/compiler/rustc_mir_transform/src/lib.rs new file mode 100644 index 00000000000..93f0a7f3d04 --- /dev/null +++ b/compiler/rustc_mir_transform/src/lib.rs @@ -0,0 +1,632 @@ +#![feature(bindings_after_at)] +#![feature(box_patterns)] +#![feature(box_syntax)] +#![feature(crate_visibility_modifier)] +#![feature(const_panic)] +#![feature(in_band_lifetimes)] +#![feature(iter_zip)] +#![feature(map_try_insert)] +#![feature(min_specialization)] +#![feature(option_get_or_insert_default)] +#![feature(once_cell)] +#![feature(never_type)] +#![feature(trusted_step)] +#![feature(try_blocks)] + +#[macro_use] +extern crate tracing; +#[macro_use] +extern crate rustc_middle; + +use required_consts::RequiredConstsVisitor; +use rustc_data_structures::fx::FxHashSet; +use rustc_data_structures::steal::Steal; +use rustc_hir as hir; +use rustc_hir::def_id::{DefId, LocalDefId}; +use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor}; +use rustc_index::vec::IndexVec; +use rustc_middle::mir::visit::Visitor as _; +use rustc_middle::mir::{traversal, Body, ConstQualifs, MirPhase, Promoted}; +use rustc_middle::ty::query::Providers; +use rustc_middle::ty::{self, TyCtxt, TypeFoldable}; +use rustc_mir::util; +use rustc_span::{Span, Symbol}; + +mod abort_unwinding_calls; +mod add_call_guards; +mod add_moves_for_packed_drops; +mod add_retag; +mod check_const_item_mutation; +mod check_packed_ref; +pub mod check_unsafety; +mod cleanup_post_borrowck; +mod const_debuginfo; +mod const_goto; +mod const_prop; +mod coverage; +mod deaggregator; +mod deduplicate_blocks; +mod dest_prop; +pub mod dump_mir; +mod early_otherwise_branch; +mod elaborate_drops; +mod function_item_references; +mod generator; +mod inline; +mod instcombine; +mod lower_intrinsics; +mod lower_slice_len; +mod match_branches; +mod multiple_return_terminators; +mod nrvo; +mod remove_noop_landing_pads; +mod remove_storage_markers; +mod remove_unneeded_drops; +mod remove_zsts; +mod required_consts; +mod separate_const_switch; +mod shim; +mod simplify; +mod simplify_branches; +mod simplify_comparison_integral; +mod simplify_try; +mod uninhabited_enum_branching; +mod unreachable_prop; + +use rustc_mir::transform::check_consts; +use rustc_mir::transform::promote_consts; +use rustc_mir::transform::rustc_peek; +use rustc_mir::transform::validate; +use rustc_mir::transform::MirPass; + +pub fn provide(providers: &mut Providers) { + check_unsafety::provide(providers); + check_packed_ref::provide(providers); + coverage::query::provide(providers); + shim::provide(providers); + *providers = Providers { + mir_keys, + mir_const, + mir_const_qualif: |tcx, def_id| { + let def_id = def_id.expect_local(); + if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) { + tcx.mir_const_qualif_const_arg(def) + } else { + mir_const_qualif(tcx, ty::WithOptConstParam::unknown(def_id)) + } + }, + mir_const_qualif_const_arg: |tcx, (did, param_did)| { + mir_const_qualif(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) }) + }, + mir_promoted, + mir_drops_elaborated_and_const_checked, + mir_for_ctfe, + mir_for_ctfe_of_const_arg, + optimized_mir, + is_mir_available, + is_ctfe_mir_available: |tcx, did| is_mir_available(tcx, did), + mir_callgraph_reachable: inline::cycle::mir_callgraph_reachable, + mir_inliner_callees: inline::cycle::mir_inliner_callees, + promoted_mir: |tcx, def_id| { + let def_id = def_id.expect_local(); + if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) { + tcx.promoted_mir_of_const_arg(def) + } else { + promoted_mir(tcx, ty::WithOptConstParam::unknown(def_id)) + } + }, + promoted_mir_of_const_arg: |tcx, (did, param_did)| { + promoted_mir(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) }) + }, + ..*providers + }; +} + +fn is_mir_available(tcx: TyCtxt<'_>, def_id: DefId) -> bool { + let def_id = def_id.expect_local(); + tcx.mir_keys(()).contains(&def_id) +} + +/// Finds the full set of `DefId`s within the current crate that have +/// MIR associated with them. +fn mir_keys(tcx: TyCtxt<'_>, (): ()) -> FxHashSet<LocalDefId> { + let mut set = FxHashSet::default(); + + // All body-owners have MIR associated with them. + set.extend(tcx.body_owners()); + + // Additionally, tuple struct/variant constructors have MIR, but + // they don't have a BodyId, so we need to build them separately. + struct GatherCtors<'a, 'tcx> { + tcx: TyCtxt<'tcx>, + set: &'a mut FxHashSet<LocalDefId>, + } + impl<'a, 'tcx> Visitor<'tcx> for GatherCtors<'a, 'tcx> { + fn visit_variant_data( + &mut self, + v: &'tcx hir::VariantData<'tcx>, + _: Symbol, + _: &'tcx hir::Generics<'tcx>, + _: hir::HirId, + _: Span, + ) { + if let hir::VariantData::Tuple(_, hir_id) = *v { + self.set.insert(self.tcx.hir().local_def_id(hir_id)); + } + intravisit::walk_struct_def(self, v) + } + type Map = intravisit::ErasedMap<'tcx>; + fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> { + NestedVisitorMap::None + } + } + tcx.hir() + .krate() + .visit_all_item_likes(&mut GatherCtors { tcx, set: &mut set }.as_deep_visitor()); + + set +} + +fn run_passes( + tcx: TyCtxt<'tcx>, + body: &mut Body<'tcx>, + mir_phase: MirPhase, + passes: &[&[&dyn MirPass<'tcx>]], +) { + let phase_index = mir_phase.phase_index(); + let validate = tcx.sess.opts.debugging_opts.validate_mir; + + if body.phase >= mir_phase { + return; + } + + if validate { + validate::Validator { when: format!("input to phase {:?}", mir_phase), mir_phase } + .run_pass(tcx, body); + } + + let mut index = 0; + let mut run_pass = |pass: &dyn MirPass<'tcx>| { + let run_hooks = |body: &_, index, is_after| { + dump_mir::on_mir_pass( + tcx, + &format_args!("{:03}-{:03}", phase_index, index), + &pass.name(), + body, + is_after, + ); + }; + run_hooks(body, index, false); + pass.run_pass(tcx, body); + run_hooks(body, index, true); + + if validate { + validate::Validator { + when: format!("after {} in phase {:?}", pass.name(), mir_phase), + mir_phase, + } + .run_pass(tcx, body); + } + + index += 1; + }; + + for pass_group in passes { + for pass in *pass_group { + run_pass(*pass); + } + } + + body.phase = mir_phase; + + if mir_phase == MirPhase::Optimization { + validate::Validator { when: format!("end of phase {:?}", mir_phase), mir_phase } + .run_pass(tcx, body); + } +} + +fn mir_const_qualif(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> ConstQualifs { + let const_kind = tcx.hir().body_const_context(def.did); + + // No need to const-check a non-const `fn`. + if const_kind.is_none() { + return Default::default(); + } + + // N.B., this `borrow()` is guaranteed to be valid (i.e., the value + // cannot yet be stolen), because `mir_promoted()`, which steals + // from `mir_const(), forces this query to execute before + // performing the steal. + let body = &tcx.mir_const(def).borrow(); + + if body.return_ty().references_error() { + tcx.sess.delay_span_bug(body.span, "mir_const_qualif: MIR had errors"); + return Default::default(); + } + + let ccx = check_consts::ConstCx { body, tcx, const_kind, param_env: tcx.param_env(def.did) }; + + let mut validator = check_consts::check::Checker::new(&ccx); + validator.check_body(); + + // We return the qualifs in the return place for every MIR body, even though it is only used + // when deciding to promote a reference to a `const` for now. + validator.qualifs_in_return_place() +} + +/// Make MIR ready for const evaluation. This is run on all MIR, not just on consts! +fn mir_const<'tcx>( + tcx: TyCtxt<'tcx>, + def: ty::WithOptConstParam<LocalDefId>, +) -> &'tcx Steal<Body<'tcx>> { + if let Some(def) = def.try_upgrade(tcx) { + return tcx.mir_const(def); + } + + // Unsafety check uses the raw mir, so make sure it is run. + if !tcx.sess.opts.debugging_opts.thir_unsafeck { + if let Some(param_did) = def.const_param_did { + tcx.ensure().unsafety_check_result_for_const_arg((def.did, param_did)); + } else { + tcx.ensure().unsafety_check_result(def.did); + } + } + + let mut body = tcx.mir_built(def).steal(); + + util::dump_mir(tcx, None, "mir_map", &0, &body, |_, _| Ok(())); + + run_passes( + tcx, + &mut body, + MirPhase::Const, + &[&[ + // MIR-level lints. + &check_packed_ref::CheckPackedRef, + &check_const_item_mutation::CheckConstItemMutation, + &function_item_references::FunctionItemReferences, + // What we need to do constant evaluation. + &simplify::SimplifyCfg::new("initial"), + &rustc_peek::SanityCheck, + ]], + ); + tcx.alloc_steal_mir(body) +} + +/// Compute the main MIR body and the list of MIR bodies of the promoteds. +fn mir_promoted( + tcx: TyCtxt<'tcx>, + def: ty::WithOptConstParam<LocalDefId>, +) -> (&'tcx Steal<Body<'tcx>>, &'tcx Steal<IndexVec<Promoted, Body<'tcx>>>) { + if let Some(def) = def.try_upgrade(tcx) { + return tcx.mir_promoted(def); + } + + // Ensure that we compute the `mir_const_qualif` for constants at + // this point, before we steal the mir-const result. + // Also this means promotion can rely on all const checks having been done. + let _ = tcx.mir_const_qualif_opt_const_arg(def); + let _ = tcx.mir_abstract_const_opt_const_arg(def.to_global()); + let mut body = tcx.mir_const(def).steal(); + + let mut required_consts = Vec::new(); + let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts); + for (bb, bb_data) in traversal::reverse_postorder(&body) { + required_consts_visitor.visit_basic_block_data(bb, bb_data); + } + body.required_consts = required_consts; + + let promote_pass = promote_consts::PromoteTemps::default(); + let promote: &[&dyn MirPass<'tcx>] = &[ + // What we need to run borrowck etc. + &promote_pass, + &simplify::SimplifyCfg::new("promote-consts"), + ]; + + let opt_coverage: &[&dyn MirPass<'tcx>] = + if tcx.sess.instrument_coverage() { &[&coverage::InstrumentCoverage] } else { &[] }; + + run_passes(tcx, &mut body, MirPhase::ConstPromotion, &[promote, opt_coverage]); + + let promoted = promote_pass.promoted_fragments.into_inner(); + (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted)) +} + +/// Compute the MIR that is used during CTFE (and thus has no optimizations run on it) +fn mir_for_ctfe<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx Body<'tcx> { + let did = def_id.expect_local(); + if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) { + tcx.mir_for_ctfe_of_const_arg(def) + } else { + tcx.arena.alloc(inner_mir_for_ctfe(tcx, ty::WithOptConstParam::unknown(did))) + } +} + +/// Same as `mir_for_ctfe`, but used to get the MIR of a const generic parameter. +/// The docs on `WithOptConstParam` explain this a bit more, but the TLDR is that +/// we'd get cycle errors with `mir_for_ctfe`, because typeck would need to typeck +/// the const parameter while type checking the main body, which in turn would try +/// to type check the main body again. +fn mir_for_ctfe_of_const_arg<'tcx>( + tcx: TyCtxt<'tcx>, + (did, param_did): (LocalDefId, DefId), +) -> &'tcx Body<'tcx> { + tcx.arena.alloc(inner_mir_for_ctfe( + tcx, + ty::WithOptConstParam { did, const_param_did: Some(param_did) }, + )) +} + +fn inner_mir_for_ctfe(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_> { + // FIXME: don't duplicate this between the optimized_mir/mir_for_ctfe queries + if tcx.is_constructor(def.did.to_def_id()) { + // There's no reason to run all of the MIR passes on constructors when + // we can just output the MIR we want directly. This also saves const + // qualification and borrow checking the trouble of special casing + // constructors. + return shim::build_adt_ctor(tcx, def.did.to_def_id()); + } + + let context = tcx + .hir() + .body_const_context(def.did) + .expect("mir_for_ctfe should not be used for runtime functions"); + + let mut body = tcx.mir_drops_elaborated_and_const_checked(def).borrow().clone(); + + match context { + // Do not const prop functions, either they get executed at runtime or exported to metadata, + // so we run const prop on them, or they don't, in which case we const evaluate some control + // flow paths of the function and any errors in those paths will get emitted as const eval + // errors. + hir::ConstContext::ConstFn => {} + // Static items always get evaluated, so we can just let const eval see if any erroneous + // control flow paths get executed. + hir::ConstContext::Static(_) => {} + // Associated constants get const prop run so we detect common failure situations in the + // crate that defined the constant. + // Technically we want to not run on regular const items, but oli-obk doesn't know how to + // conveniently detect that at this point without looking at the HIR. + hir::ConstContext::Const => { + #[rustfmt::skip] + let optimizations: &[&dyn MirPass<'_>] = &[ + &const_prop::ConstProp, + ]; + + #[rustfmt::skip] + run_passes( + tcx, + &mut body, + MirPhase::Optimization, + &[ + optimizations, + ], + ); + } + } + + debug_assert!(!body.has_free_regions(tcx), "Free regions in MIR for CTFE"); + + body +} + +/// Obtain just the main MIR (no promoteds) and run some cleanups on it. This also runs +/// mir borrowck *before* doing so in order to ensure that borrowck can be run and doesn't +/// end up missing the source MIR due to stealing happening. +fn mir_drops_elaborated_and_const_checked<'tcx>( + tcx: TyCtxt<'tcx>, + def: ty::WithOptConstParam<LocalDefId>, +) -> &'tcx Steal<Body<'tcx>> { + if let Some(def) = def.try_upgrade(tcx) { + return tcx.mir_drops_elaborated_and_const_checked(def); + } + + // (Mir-)Borrowck uses `mir_promoted`, so we have to force it to + // execute before we can steal. + if let Some(param_did) = def.const_param_did { + tcx.ensure().mir_borrowck_const_arg((def.did, param_did)); + } else { + tcx.ensure().mir_borrowck(def.did); + } + + let hir_id = tcx.hir().local_def_id_to_hir_id(def.did); + use rustc_middle::hir::map::blocks::FnLikeNode; + let is_fn_like = FnLikeNode::from_node(tcx.hir().get(hir_id)).is_some(); + if is_fn_like { + let did = def.did.to_def_id(); + let def = ty::WithOptConstParam::unknown(did); + + // Do not compute the mir call graph without said call graph actually being used. + if inline::is_enabled(tcx) { + let _ = tcx.mir_inliner_callees(ty::InstanceDef::Item(def)); + } + } + + let (body, _) = tcx.mir_promoted(def); + let mut body = body.steal(); + + run_post_borrowck_cleanup_passes(tcx, &mut body); + check_consts::post_drop_elaboration::check_live_drops(tcx, &body); + tcx.alloc_steal_mir(body) +} + +/// After this series of passes, no lifetime analysis based on borrowing can be done. +fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { + debug!("post_borrowck_cleanup({:?})", body.source.def_id()); + + let post_borrowck_cleanup: &[&dyn MirPass<'tcx>] = &[ + // Remove all things only needed by analysis + &simplify_branches::SimplifyBranches::new("initial"), + &remove_noop_landing_pads::RemoveNoopLandingPads, + &cleanup_post_borrowck::CleanupNonCodegenStatements, + &simplify::SimplifyCfg::new("early-opt"), + // These next passes must be executed together + &add_call_guards::CriticalCallEdges, + &elaborate_drops::ElaborateDrops, + // This will remove extraneous landing pads which are no longer + // necessary as well as well as forcing any call in a non-unwinding + // function calling a possibly-unwinding function to abort the process. + &abort_unwinding_calls::AbortUnwindingCalls, + // AddMovesForPackedDrops needs to run after drop + // elaboration. + &add_moves_for_packed_drops::AddMovesForPackedDrops, + // `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late, + // but before optimizations begin. + &add_retag::AddRetag, + &lower_intrinsics::LowerIntrinsics, + &simplify::SimplifyCfg::new("elaborate-drops"), + // `Deaggregator` is conceptually part of MIR building, some backends rely on it happening + // and it can help optimizations. + &deaggregator::Deaggregator, + ]; + + run_passes(tcx, body, MirPhase::DropLowering, &[post_borrowck_cleanup]); +} + +fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) { + let mir_opt_level = tcx.sess.mir_opt_level(); + + // Lowering generator control-flow and variables has to happen before we do anything else + // to them. We run some optimizations before that, because they may be harder to do on the state + // machine than on MIR with async primitives. + let optimizations_with_generators: &[&dyn MirPass<'tcx>] = &[ + &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 + &unreachable_prop::UnreachablePropagation, + &uninhabited_enum_branching::UninhabitedEnumBranching, + &simplify::SimplifyCfg::new("after-uninhabited-enum-branching"), + &inline::Inline, + &generator::StateTransform, + ]; + + // Even if we don't do optimizations, we still have to lower generators for codegen. + let no_optimizations_with_generators: &[&dyn MirPass<'tcx>] = &[&generator::StateTransform]; + + // The main optimizations that we do on MIR. + let optimizations: &[&dyn MirPass<'tcx>] = &[ + &remove_storage_markers::RemoveStorageMarkers, + &remove_zsts::RemoveZsts, + &const_goto::ConstGoto, + &remove_unneeded_drops::RemoveUnneededDrops, + &match_branches::MatchBranchSimplification, + // inst combine is after MatchBranchSimplification to clean up Ne(_1, false) + &multiple_return_terminators::MultipleReturnTerminators, + &instcombine::InstCombine, + &separate_const_switch::SeparateConstSwitch, + &const_prop::ConstProp, + &simplify_branches::SimplifyBranches::new("after-const-prop"), + &early_otherwise_branch::EarlyOtherwiseBranch, + &simplify_comparison_integral::SimplifyComparisonIntegral, + &simplify_try::SimplifyArmIdentity, + &simplify_try::SimplifyBranchSame, + &dest_prop::DestinationPropagation, + &simplify_branches::SimplifyBranches::new("final"), + &remove_noop_landing_pads::RemoveNoopLandingPads, + &simplify::SimplifyCfg::new("final"), + &nrvo::RenameReturnPlace, + &const_debuginfo::ConstDebugInfo, + &simplify::SimplifyLocals, + &multiple_return_terminators::MultipleReturnTerminators, + &deduplicate_blocks::DeduplicateBlocks, + ]; + + // Optimizations to run even if mir optimizations have been disabled. + let no_optimizations: &[&dyn MirPass<'tcx>] = &[ + // FIXME(#70073): This pass is responsible for both optimization as well as some lints. + &const_prop::ConstProp, + ]; + + // Some cleanup necessary at least for LLVM and potentially other codegen backends. + let pre_codegen_cleanup: &[&dyn MirPass<'tcx>] = &[ + &add_call_guards::CriticalCallEdges, + // Dump the end result for testing and debugging purposes. + &dump_mir::Marker("PreCodegen"), + ]; + + // End of pass declarations, now actually run the passes. + // Generator Lowering + #[rustfmt::skip] + run_passes( + tcx, + body, + MirPhase::GeneratorLowering, + &[ + if mir_opt_level > 0 { + optimizations_with_generators + } else { + no_optimizations_with_generators + } + ], + ); + + // Main optimization passes + #[rustfmt::skip] + run_passes( + tcx, + body, + MirPhase::Optimization, + &[ + if mir_opt_level > 0 { optimizations } else { no_optimizations }, + pre_codegen_cleanup, + ], + ); +} + +/// Optimize the MIR and prepare it for codegen. +fn optimized_mir<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx Body<'tcx> { + let did = did.expect_local(); + assert_eq!(ty::WithOptConstParam::try_lookup(did, tcx), None); + tcx.arena.alloc(inner_optimized_mir(tcx, did)) +} + +fn inner_optimized_mir(tcx: TyCtxt<'_>, did: LocalDefId) -> Body<'_> { + if tcx.is_constructor(did.to_def_id()) { + // There's no reason to run all of the MIR passes on constructors when + // we can just output the MIR we want directly. This also saves const + // qualification and borrow checking the trouble of special casing + // constructors. + return shim::build_adt_ctor(tcx, did.to_def_id()); + } + + match tcx.hir().body_const_context(did) { + // Run the `mir_for_ctfe` query, which depends on `mir_drops_elaborated_and_const_checked` + // which we are going to steal below. Thus we need to run `mir_for_ctfe` first, so it + // computes and caches its result. + Some(hir::ConstContext::ConstFn) => tcx.ensure().mir_for_ctfe(did), + None => {} + Some(other) => panic!("do not use `optimized_mir` for constants: {:?}", other), + } + let mut body = + tcx.mir_drops_elaborated_and_const_checked(ty::WithOptConstParam::unknown(did)).steal(); + run_optimization_passes(tcx, &mut body); + + debug_assert!(!body.has_free_regions(tcx), "Free regions in optimized MIR"); + + body +} + +/// Fetch all the promoteds of an item and prepare their MIR bodies to be ready for +/// constant evaluation once all substitutions become known. +fn promoted_mir<'tcx>( + tcx: TyCtxt<'tcx>, + def: ty::WithOptConstParam<LocalDefId>, +) -> &'tcx IndexVec<Promoted, Body<'tcx>> { + if tcx.is_constructor(def.did.to_def_id()) { + return tcx.arena.alloc(IndexVec::new()); + } + + if let Some(param_did) = def.const_param_did { + tcx.ensure().mir_borrowck_const_arg((def.did, param_did)); + } else { + tcx.ensure().mir_borrowck(def.did); + } + let (_, promoted) = tcx.mir_promoted(def); + let mut promoted = promoted.steal(); + + for body in &mut promoted { + run_post_borrowck_cleanup_passes(tcx, body); + } + + debug_assert!(!promoted.has_free_regions(tcx), "Free regions in promoted MIR"); + + tcx.arena.alloc(promoted) +} |