6903273339
This allows constant propagation to evaluate `size_of` and `wrapping_*`, and unreachable propagation to propagate a call to `unreachable`. The lowering is performed as a MIR optimization, rather than during MIR building to preserve the special status of intrinsics with respect to unsafety checks and promotion.
518 lines
18 KiB
Rust
518 lines
18 KiB
Rust
use crate::{shim, util};
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use required_consts::RequiredConstsVisitor;
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use rustc_data_structures::fx::FxHashSet;
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use rustc_hir as hir;
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use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
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use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
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use rustc_index::vec::IndexVec;
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use rustc_middle::mir::visit::Visitor as _;
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use rustc_middle::mir::{traversal, Body, ConstQualifs, MirPhase, Promoted};
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use rustc_middle::ty::query::Providers;
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use rustc_middle::ty::steal::Steal;
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use rustc_middle::ty::{self, TyCtxt, TypeFoldable};
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use rustc_span::{Span, Symbol};
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use std::borrow::Cow;
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pub mod add_call_guards;
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pub mod add_moves_for_packed_drops;
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pub mod add_retag;
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pub mod check_const_item_mutation;
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pub mod check_consts;
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pub mod check_packed_ref;
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pub mod check_unsafety;
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pub mod cleanup_post_borrowck;
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pub mod const_prop;
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pub mod coverage;
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pub mod deaggregator;
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pub mod dest_prop;
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pub mod dump_mir;
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pub mod early_otherwise_branch;
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pub mod elaborate_drops;
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pub mod function_item_references;
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pub mod generator;
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pub mod inline;
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pub mod instcombine;
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pub mod lower_intrinsics;
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pub mod match_branches;
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pub mod multiple_return_terminators;
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pub mod no_landing_pads;
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pub mod nrvo;
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pub mod promote_consts;
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pub mod remove_noop_landing_pads;
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pub mod remove_unneeded_drops;
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pub mod required_consts;
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pub mod rustc_peek;
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pub mod simplify;
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pub mod simplify_branches;
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pub mod simplify_comparison_integral;
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pub mod simplify_try;
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pub mod uninhabited_enum_branching;
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pub mod unreachable_prop;
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pub mod validate;
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pub use rustc_middle::mir::MirSource;
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pub(crate) fn provide(providers: &mut Providers) {
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self::check_unsafety::provide(providers);
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*providers = Providers {
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mir_keys,
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mir_const,
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mir_const_qualif: |tcx, def_id| {
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let def_id = def_id.expect_local();
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if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
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tcx.mir_const_qualif_const_arg(def)
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} else {
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mir_const_qualif(tcx, ty::WithOptConstParam::unknown(def_id))
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}
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},
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mir_const_qualif_const_arg: |tcx, (did, param_did)| {
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mir_const_qualif(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
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},
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mir_promoted,
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mir_drops_elaborated_and_const_checked,
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optimized_mir,
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optimized_mir_of_const_arg,
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is_mir_available,
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promoted_mir: |tcx, def_id| {
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let def_id = def_id.expect_local();
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if let Some(def) = ty::WithOptConstParam::try_lookup(def_id, tcx) {
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tcx.promoted_mir_of_const_arg(def)
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} else {
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promoted_mir(tcx, ty::WithOptConstParam::unknown(def_id))
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}
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},
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promoted_mir_of_const_arg: |tcx, (did, param_did)| {
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promoted_mir(tcx, ty::WithOptConstParam { did, const_param_did: Some(param_did) })
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},
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..*providers
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};
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coverage::query::provide(providers);
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}
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fn is_mir_available(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
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tcx.mir_keys(def_id.krate).contains(&def_id.expect_local())
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}
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/// Finds the full set of `DefId`s within the current crate that have
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/// MIR associated with them.
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fn mir_keys(tcx: TyCtxt<'_>, krate: CrateNum) -> FxHashSet<LocalDefId> {
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assert_eq!(krate, LOCAL_CRATE);
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let mut set = FxHashSet::default();
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// All body-owners have MIR associated with them.
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set.extend(tcx.body_owners());
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// Additionally, tuple struct/variant constructors have MIR, but
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// they don't have a BodyId, so we need to build them separately.
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struct GatherCtors<'a, 'tcx> {
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tcx: TyCtxt<'tcx>,
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set: &'a mut FxHashSet<LocalDefId>,
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}
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impl<'a, 'tcx> Visitor<'tcx> for GatherCtors<'a, 'tcx> {
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fn visit_variant_data(
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&mut self,
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v: &'tcx hir::VariantData<'tcx>,
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_: Symbol,
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_: &'tcx hir::Generics<'tcx>,
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_: hir::HirId,
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_: Span,
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) {
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if let hir::VariantData::Tuple(_, hir_id) = *v {
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self.set.insert(self.tcx.hir().local_def_id(hir_id));
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}
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intravisit::walk_struct_def(self, v)
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}
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type Map = intravisit::ErasedMap<'tcx>;
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fn nested_visit_map(&mut self) -> NestedVisitorMap<Self::Map> {
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NestedVisitorMap::None
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}
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}
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tcx.hir()
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.krate()
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.visit_all_item_likes(&mut GatherCtors { tcx, set: &mut set }.as_deep_visitor());
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set
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}
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/// Generates a default name for the pass based on the name of the
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/// type `T`.
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pub fn default_name<T: ?Sized>() -> Cow<'static, str> {
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let name = std::any::type_name::<T>();
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if let Some(tail) = name.rfind(':') { Cow::from(&name[tail + 1..]) } else { Cow::from(name) }
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}
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/// A streamlined trait that you can implement to create a pass; the
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/// pass will be named after the type, and it will consist of a main
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/// loop that goes over each available MIR and applies `run_pass`.
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pub trait MirPass<'tcx> {
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fn name(&self) -> Cow<'_, str> {
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default_name::<Self>()
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}
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fn run_pass(&self, tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>);
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}
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pub fn run_passes(
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tcx: TyCtxt<'tcx>,
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body: &mut Body<'tcx>,
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mir_phase: MirPhase,
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passes: &[&[&dyn MirPass<'tcx>]],
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) {
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let phase_index = mir_phase.phase_index();
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let validate = tcx.sess.opts.debugging_opts.validate_mir;
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if body.phase >= mir_phase {
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return;
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}
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if validate {
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validate::Validator { when: format!("input to phase {:?}", mir_phase), mir_phase }
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.run_pass(tcx, body);
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}
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let mut index = 0;
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let mut run_pass = |pass: &dyn MirPass<'tcx>| {
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let run_hooks = |body: &_, index, is_after| {
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dump_mir::on_mir_pass(
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tcx,
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&format_args!("{:03}-{:03}", phase_index, index),
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&pass.name(),
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body,
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is_after,
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);
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};
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run_hooks(body, index, false);
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pass.run_pass(tcx, body);
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run_hooks(body, index, true);
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if validate {
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validate::Validator {
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when: format!("after {} in phase {:?}", pass.name(), mir_phase),
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mir_phase,
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}
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.run_pass(tcx, body);
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}
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index += 1;
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};
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for pass_group in passes {
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for pass in *pass_group {
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run_pass(*pass);
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}
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}
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body.phase = mir_phase;
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if mir_phase == MirPhase::Optimization {
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validate::Validator { when: format!("end of phase {:?}", mir_phase), mir_phase }
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.run_pass(tcx, body);
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}
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}
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fn mir_const_qualif(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> ConstQualifs {
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let const_kind = tcx.hir().body_const_context(def.did);
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// No need to const-check a non-const `fn`.
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if const_kind.is_none() {
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return Default::default();
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}
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// N.B., this `borrow()` is guaranteed to be valid (i.e., the value
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// cannot yet be stolen), because `mir_promoted()`, which steals
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// from `mir_const(), forces this query to execute before
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// performing the steal.
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let body = &tcx.mir_const(def).borrow();
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if body.return_ty().references_error() {
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tcx.sess.delay_span_bug(body.span, "mir_const_qualif: MIR had errors");
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return Default::default();
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}
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let ccx = check_consts::ConstCx { body, tcx, const_kind, param_env: tcx.param_env(def.did) };
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let mut validator = check_consts::validation::Validator::new(&ccx);
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validator.check_body();
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// We return the qualifs in the return place for every MIR body, even though it is only used
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// when deciding to promote a reference to a `const` for now.
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validator.qualifs_in_return_place()
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}
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/// Make MIR ready for const evaluation. This is run on all MIR, not just on consts!
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fn mir_const<'tcx>(
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tcx: TyCtxt<'tcx>,
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def: ty::WithOptConstParam<LocalDefId>,
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) -> &'tcx Steal<Body<'tcx>> {
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if let Some(def) = def.try_upgrade(tcx) {
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return tcx.mir_const(def);
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}
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// Unsafety check uses the raw mir, so make sure it is run.
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if let Some(param_did) = def.const_param_did {
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tcx.ensure().unsafety_check_result_for_const_arg((def.did, param_did));
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} else {
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tcx.ensure().unsafety_check_result(def.did);
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}
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let mut body = tcx.mir_built(def).steal();
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util::dump_mir(tcx, None, "mir_map", &0, &body, |_, _| Ok(()));
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run_passes(
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tcx,
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&mut body,
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MirPhase::Const,
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&[&[
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// MIR-level lints.
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&check_packed_ref::CheckPackedRef,
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&check_const_item_mutation::CheckConstItemMutation,
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&function_item_references::FunctionItemReferences,
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// What we need to do constant evaluation.
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&simplify::SimplifyCfg::new("initial"),
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&rustc_peek::SanityCheck,
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]],
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);
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tcx.alloc_steal_mir(body)
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}
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fn mir_promoted(
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tcx: TyCtxt<'tcx>,
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def: ty::WithOptConstParam<LocalDefId>,
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) -> (&'tcx Steal<Body<'tcx>>, &'tcx Steal<IndexVec<Promoted, Body<'tcx>>>) {
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if let Some(def) = def.try_upgrade(tcx) {
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return tcx.mir_promoted(def);
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}
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// Ensure that we compute the `mir_const_qualif` for constants at
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// this point, before we steal the mir-const result.
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// Also this means promotion can rely on all const checks having been done.
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let _ = tcx.mir_const_qualif_opt_const_arg(def);
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let _ = tcx.mir_abstract_const_opt_const_arg(def.to_global());
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let mut body = tcx.mir_const(def).steal();
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let mut required_consts = Vec::new();
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let mut required_consts_visitor = RequiredConstsVisitor::new(&mut required_consts);
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for (bb, bb_data) in traversal::reverse_postorder(&body) {
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required_consts_visitor.visit_basic_block_data(bb, bb_data);
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}
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body.required_consts = required_consts;
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let promote_pass = promote_consts::PromoteTemps::default();
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let promote: &[&dyn MirPass<'tcx>] = &[
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// What we need to run borrowck etc.
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&promote_pass,
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&simplify::SimplifyCfg::new("promote-consts"),
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];
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let opt_coverage: &[&dyn MirPass<'tcx>] = if tcx.sess.opts.debugging_opts.instrument_coverage {
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&[&coverage::InstrumentCoverage]
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} else {
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&[]
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};
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run_passes(tcx, &mut body, MirPhase::ConstPromotion, &[promote, opt_coverage]);
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let promoted = promote_pass.promoted_fragments.into_inner();
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(tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
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}
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fn mir_drops_elaborated_and_const_checked<'tcx>(
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tcx: TyCtxt<'tcx>,
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def: ty::WithOptConstParam<LocalDefId>,
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) -> &'tcx Steal<Body<'tcx>> {
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if let Some(def) = def.try_upgrade(tcx) {
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return tcx.mir_drops_elaborated_and_const_checked(def);
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}
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// (Mir-)Borrowck uses `mir_promoted`, so we have to force it to
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// execute before we can steal.
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if let Some(param_did) = def.const_param_did {
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tcx.ensure().mir_borrowck_const_arg((def.did, param_did));
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} else {
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tcx.ensure().mir_borrowck(def.did);
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}
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let (body, _) = tcx.mir_promoted(def);
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let mut body = body.steal();
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run_post_borrowck_cleanup_passes(tcx, &mut body);
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check_consts::post_drop_elaboration::check_live_drops(tcx, &body);
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tcx.alloc_steal_mir(body)
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}
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/// After this series of passes, no lifetime analysis based on borrowing can be done.
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fn run_post_borrowck_cleanup_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
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debug!("post_borrowck_cleanup({:?})", body.source.def_id());
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let post_borrowck_cleanup: &[&dyn MirPass<'tcx>] = &[
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// Remove all things only needed by analysis
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&no_landing_pads::NoLandingPads::new(tcx),
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&simplify_branches::SimplifyBranches::new("initial"),
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&remove_noop_landing_pads::RemoveNoopLandingPads,
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&cleanup_post_borrowck::CleanupNonCodegenStatements,
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&simplify::SimplifyCfg::new("early-opt"),
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// These next passes must be executed together
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&add_call_guards::CriticalCallEdges,
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&elaborate_drops::ElaborateDrops,
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&no_landing_pads::NoLandingPads::new(tcx),
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// AddMovesForPackedDrops needs to run after drop
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// elaboration.
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&add_moves_for_packed_drops::AddMovesForPackedDrops,
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// `AddRetag` needs to run after `ElaborateDrops`. Otherwise it should run fairly late,
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// but before optimizations begin.
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&add_retag::AddRetag,
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&simplify::SimplifyCfg::new("elaborate-drops"),
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// `Deaggregator` is conceptually part of MIR building, some backends rely on it happening
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// and it can help optimizations.
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&deaggregator::Deaggregator,
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];
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run_passes(tcx, body, MirPhase::DropLowering, &[post_borrowck_cleanup]);
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}
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fn run_optimization_passes<'tcx>(tcx: TyCtxt<'tcx>, body: &mut Body<'tcx>) {
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let mir_opt_level = tcx.sess.opts.debugging_opts.mir_opt_level;
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// Lowering generator control-flow and variables has to happen before we do anything else
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// to them. We run some optimizations before that, because they may be harder to do on the state
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// machine than on MIR with async primitives.
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let optimizations_with_generators: &[&dyn MirPass<'tcx>] = &[
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&unreachable_prop::UnreachablePropagation,
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&uninhabited_enum_branching::UninhabitedEnumBranching,
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&simplify::SimplifyCfg::new("after-uninhabited-enum-branching"),
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&inline::Inline,
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&generator::StateTransform,
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];
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// Even if we don't do optimizations, we still have to lower generators for codegen.
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let no_optimizations_with_generators: &[&dyn MirPass<'tcx>] = &[&generator::StateTransform];
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// The main optimizations that we do on MIR.
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let optimizations: &[&dyn MirPass<'tcx>] = &[
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&lower_intrinsics::LowerIntrinsics,
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&remove_unneeded_drops::RemoveUnneededDrops,
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&match_branches::MatchBranchSimplification,
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// inst combine is after MatchBranchSimplification to clean up Ne(_1, false)
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&multiple_return_terminators::MultipleReturnTerminators,
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&instcombine::InstCombine,
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&const_prop::ConstProp,
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&simplify_branches::SimplifyBranches::new("after-const-prop"),
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&early_otherwise_branch::EarlyOtherwiseBranch,
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&simplify_comparison_integral::SimplifyComparisonIntegral,
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&simplify_try::SimplifyArmIdentity,
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&simplify_try::SimplifyBranchSame,
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&dest_prop::DestinationPropagation,
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&simplify_branches::SimplifyBranches::new("final"),
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&remove_noop_landing_pads::RemoveNoopLandingPads,
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&simplify::SimplifyCfg::new("final"),
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&nrvo::RenameReturnPlace,
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&simplify::SimplifyLocals,
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&multiple_return_terminators::MultipleReturnTerminators,
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];
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// Optimizations to run even if mir optimizations have been disabled.
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let no_optimizations: &[&dyn MirPass<'tcx>] = &[
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// FIXME(#70073): This pass is responsible for both optimization as well as some lints.
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&const_prop::ConstProp,
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];
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// Some cleanup necessary at least for LLVM and potentially other codegen backends.
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let pre_codegen_cleanup: &[&dyn MirPass<'tcx>] = &[
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&add_call_guards::CriticalCallEdges,
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// Dump the end result for testing and debugging purposes.
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&dump_mir::Marker("PreCodegen"),
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];
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// End of pass declarations, now actually run the passes.
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// Generator Lowering
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#[rustfmt::skip]
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run_passes(
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tcx,
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body,
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MirPhase::GeneratorLowering,
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&[
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if mir_opt_level > 0 {
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optimizations_with_generators
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} else {
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no_optimizations_with_generators
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}
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],
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);
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// Main optimization passes
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#[rustfmt::skip]
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run_passes(
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tcx,
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body,
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MirPhase::Optimization,
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&[
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if mir_opt_level > 0 { optimizations } else { no_optimizations },
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pre_codegen_cleanup,
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],
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|
);
|
|
}
|
|
|
|
fn optimized_mir<'tcx>(tcx: TyCtxt<'tcx>, did: DefId) -> &'tcx Body<'tcx> {
|
|
let did = did.expect_local();
|
|
if let Some(def) = ty::WithOptConstParam::try_lookup(did, tcx) {
|
|
tcx.optimized_mir_of_const_arg(def)
|
|
} else {
|
|
tcx.arena.alloc(inner_optimized_mir(tcx, ty::WithOptConstParam::unknown(did)))
|
|
}
|
|
}
|
|
|
|
fn optimized_mir_of_const_arg<'tcx>(
|
|
tcx: TyCtxt<'tcx>,
|
|
(did, param_did): (LocalDefId, DefId),
|
|
) -> &'tcx Body<'tcx> {
|
|
tcx.arena.alloc(inner_optimized_mir(
|
|
tcx,
|
|
ty::WithOptConstParam { did, const_param_did: Some(param_did) },
|
|
))
|
|
}
|
|
|
|
fn inner_optimized_mir(tcx: TyCtxt<'_>, def: ty::WithOptConstParam<LocalDefId>) -> Body<'_> {
|
|
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 mut body = tcx.mir_drops_elaborated_and_const_checked(def).steal();
|
|
run_optimization_passes(tcx, &mut body);
|
|
|
|
debug_assert!(!body.has_free_regions(), "Free regions in optimized MIR");
|
|
|
|
body
|
|
}
|
|
|
|
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);
|
|
run_optimization_passes(tcx, body);
|
|
}
|
|
|
|
debug_assert!(!promoted.has_free_regions(), "Free regions in promoted MIR");
|
|
|
|
tcx.arena.alloc(promoted)
|
|
}
|