src/librustc_mir/transform/mod.rs

   1 use crate::{build, shim};
   2 use rustc_index::vec::IndexVec;
   3 use rustc::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
   4 use rustc::mir::{Body, MirPhase, Promoted};
   5 use rustc::ty::{TyCtxt, InstanceDef};
   6 use rustc::ty::query::Providers;
   7 use rustc::ty::steal::Steal;
   8 use rustc::hir;
   9 use rustc::hir::intravisit::{self, Visitor, NestedVisitorMap};
  10 use rustc::util::nodemap::DefIdSet;
  11 use std::borrow::Cow;
  12 use syntax::ast;
  13 use syntax_pos::Span;
  14
  15 pub mod add_retag;
  16 pub mod add_moves_for_packed_drops;
  17 pub mod cleanup_post_borrowck;
  18 pub mod check_consts;
  19 pub mod check_unsafety;
  20 pub mod simplify_branches;
  21 pub mod simplify;
  22 pub mod erase_regions;
  23 pub mod no_landing_pads;
  24 pub mod rustc_peek;
  25 pub mod elaborate_drops;
  26 pub mod add_call_guards;
  27 pub mod promote_consts;
  28 pub mod qualify_consts;
  29 pub mod qualify_min_const_fn;
  30 pub mod remove_noop_landing_pads;
  31 pub mod dump_mir;
  32 pub mod deaggregator;
  33 pub mod instcombine;
  34 pub mod copy_prop;
  35 pub mod const_prop;
  36 pub mod generator;
  37 pub mod inline;
  38 pub mod uniform_array_move_out;
  39
  40 pub(crate) fn provide(providers: &mut Providers<'_>) {
  41     self::qualify_consts::provide(providers);
  42     self::check_unsafety::provide(providers);
  43     *providers = Providers {
  44         mir_keys,
  45         mir_built,
  46         mir_const,
  47         mir_validated,
  48         optimized_mir,
  49         is_mir_available,
  50         promoted_mir,
  51         ..*providers
  52     };
  53 }
  54
  55 fn is_mir_available(tcx: TyCtxt<'_>, def_id: DefId) -> bool {
  56     tcx.mir_keys(def_id.krate).contains(&def_id)
  57 }
  58
  59 /// Finds the full set of `DefId`s within the current crate that have
  60 /// MIR associated with them.
  61 fn mir_keys(tcx: TyCtxt<'_>, krate: CrateNum) -> &DefIdSet {
  62     assert_eq!(krate, LOCAL_CRATE);
  63
  64     let mut set = DefIdSet::default();
  65
  66     // All body-owners have MIR associated with them.
  67     set.extend(tcx.body_owners());
  68
  69     // Additionally, tuple struct/variant constructors have MIR, but
  70     // they don't have a BodyId, so we need to build them separately.
  71     struct GatherCtors<'a, 'tcx> {
  72         tcx: TyCtxt<'tcx>,
  73         set: &'a mut DefIdSet,
  74     }
  75     impl<'a, 'tcx> Visitor<'tcx> for GatherCtors<'a, 'tcx> {
  76         fn visit_variant_data(&mut self,
  77                               v: &'tcx hir::VariantData,
  78                               _: ast::Name,
  79                               _: &'tcx hir::Generics,
  80                               _: hir::HirId,
  81                               _: Span) {
  82             if let hir::VariantData::Tuple(_, hir_id) = *v {
  83                 self.set.insert(self.tcx.hir().local_def_id(hir_id));
  84             }
  85             intravisit::walk_struct_def(self, v)
  86         }
  87         fn nested_visit_map<'b>(&'b mut self) -> NestedVisitorMap<'b, 'tcx> {
  88             NestedVisitorMap::None
  89         }
  90     }
  91     tcx.hir().krate().visit_all_item_likes(&mut GatherCtors {
  92         tcx,
  93         set: &mut set,
  94     }.as_deep_visitor());
  95
  96     tcx.arena.alloc(set)
  97 }
  98
  99 fn mir_built(tcx: TyCtxt<'_>, def_id: DefId) -> &Steal<Body<'_>> {
 100     let mir = build::mir_build(tcx, def_id);
 101     tcx.alloc_steal_mir(mir)
 102 }
 103
 104 /// Where a specific `mir::Body` comes from.
 105 #[derive(Debug, Copy, Clone)]
 106 pub struct MirSource<'tcx> {
 107     pub instance: InstanceDef<'tcx>,
 108
 109     /// If `Some`, this is a promoted rvalue within the parent function.
 110     pub promoted: Option<Promoted>,
 111 }
 112
 113 impl<'tcx> MirSource<'tcx> {
 114     pub fn item(def_id: DefId) -> Self {
 115         MirSource {
 116             instance: InstanceDef::Item(def_id),
 117             promoted: None
 118         }
 119     }
 120
 121     #[inline]
 122     pub fn def_id(&self) -> DefId {
 123         self.instance.def_id()
 124     }
 125 }
 126
 127 /// Generates a default name for the pass based on the name of the
 128 /// type `T`.
 129 pub fn default_name<T: ?Sized>() -> Cow<'static, str> {
 130     let name = ::std::any::type_name::<T>();
 131     if let Some(tail) = name.rfind(":") {
 132         Cow::from(&name[tail+1..])
 133     } else {
 134         Cow::from(name)
 135     }
 136 }
 137
 138 /// A streamlined trait that you can implement to create a pass; the
 139 /// pass will be named after the type, and it will consist of a main
 140 /// loop that goes over each available MIR and applies `run_pass`.
 141 pub trait MirPass<'tcx> {
 142     fn name(&self) -> Cow<'_, str> {
 143         default_name::<Self>()
 144     }
 145
 146     fn run_pass(&self, tcx: TyCtxt<'tcx>, source: MirSource<'tcx>, body: &mut Body<'tcx>);
 147 }
 148
 149 pub fn run_passes(
 150     tcx: TyCtxt<'tcx>,
 151     body: &mut Body<'tcx>,
 152     instance: InstanceDef<'tcx>,
 153     promoted: Option<Promoted>,
 154     mir_phase: MirPhase,
 155     passes: &[&dyn MirPass<'tcx>],
 156 ) {
 157     let phase_index = mir_phase.phase_index();
 158
 159     if body.phase >= mir_phase {
 160         return;
 161     }
 162
 163     let source = MirSource {
 164         instance,
 165         promoted,
 166     };
 167     let mut index = 0;
 168     let mut run_pass = |pass: &dyn MirPass<'tcx>| {
 169         let run_hooks = |body: &_, index, is_after| {
 170             dump_mir::on_mir_pass(tcx, &format_args!("{:03}-{:03}", phase_index, index),
 171                                     &pass.name(), source, body, is_after);
 172         };
 173         run_hooks(body, index, false);
 174         pass.run_pass(tcx, source, body);
 175         run_hooks(body, index, true);
 176
 177         index += 1;
 178     };
 179
 180     for pass in passes {
 181         run_pass(*pass);
 182     }
 183
 184     body.phase = mir_phase;
 185 }
 186
 187 fn mir_const(tcx: TyCtxt<'_>, def_id: DefId) -> &Steal<Body<'_>> {
 188     // Unsafety check uses the raw mir, so make sure it is run
 189     let _ = tcx.unsafety_check_result(def_id);
 190
 191     let mut body = tcx.mir_built(def_id).steal();
 192     run_passes(tcx, &mut body, InstanceDef::Item(def_id), None, MirPhase::Const, &[
 193         // What we need to do constant evaluation.
 194         &simplify::SimplifyCfg::new("initial"),
 195         &rustc_peek::SanityCheck,
 196         &uniform_array_move_out::UniformArrayMoveOut,
 197     ]);
 198     tcx.alloc_steal_mir(body)
 199 }
 200
 201 fn mir_validated(
 202     tcx: TyCtxt<'tcx>,
 203     def_id: DefId,
 204 ) -> (&'tcx Steal<Body<'tcx>>, &'tcx Steal<IndexVec<Promoted, Body<'tcx>>>) {
 205     let hir_id = tcx.hir().as_local_hir_id(def_id).unwrap();
 206     if let hir::BodyOwnerKind::Const = tcx.hir().body_owner_kind(hir_id) {
 207         // Ensure that we compute the `mir_const_qualif` for constants at
 208         // this point, before we steal the mir-const result.
 209         let _ = tcx.mir_const_qualif(def_id);
 210     }
 211
 212     let mut body = tcx.mir_const(def_id).steal();
 213     let qualify_and_promote_pass = qualify_consts::QualifyAndPromoteConstants::default();
 214     run_passes(tcx, &mut body, InstanceDef::Item(def_id), None, MirPhase::Validated, &[
 215         // What we need to run borrowck etc.
 216         &qualify_and_promote_pass,
 217         &simplify::SimplifyCfg::new("qualify-consts"),
 218     ]);
 219     let promoted = qualify_and_promote_pass.promoted.into_inner();
 220     (tcx.alloc_steal_mir(body), tcx.alloc_steal_promoted(promoted))
 221 }
 222
 223 fn run_optimization_passes<'tcx>(
 224     tcx: TyCtxt<'tcx>,
 225     body: &mut Body<'tcx>,
 226     def_id: DefId,
 227     promoted: Option<Promoted>,
 228 ) {
 229     run_passes(tcx, body, InstanceDef::Item(def_id), promoted, MirPhase::Optimized, &[
 230         // Remove all things only needed by analysis
 231         &no_landing_pads::NoLandingPads::new(tcx),
 232         &simplify_branches::SimplifyBranches::new("initial"),
 233         &remove_noop_landing_pads::RemoveNoopLandingPads,
 234         &cleanup_post_borrowck::CleanupNonCodegenStatements,
 235
 236         &simplify::SimplifyCfg::new("early-opt"),
 237
 238         // These next passes must be executed together
 239         &add_call_guards::CriticalCallEdges,
 240         &elaborate_drops::ElaborateDrops,
 241         &no_landing_pads::NoLandingPads::new(tcx),
 242         // AddMovesForPackedDrops needs to run after drop
 243         // elaboration.
 244         &add_moves_for_packed_drops::AddMovesForPackedDrops,
 245         // AddRetag needs to run after ElaborateDrops, and it needs
 246         // an AllCallEdges pass right before it.  Otherwise it should
 247         // run fairly late, but before optimizations begin.
 248         &add_call_guards::AllCallEdges,
 249         &add_retag::AddRetag,
 250
 251         &simplify::SimplifyCfg::new("elaborate-drops"),
 252
 253         // No lifetime analysis based on borrowing can be done from here on out.
 254
 255         // From here on out, regions are gone.
 256         &erase_regions::EraseRegions,
 257
 258
 259         // Optimizations begin.
 260         &uniform_array_move_out::RestoreSubsliceArrayMoveOut::new(tcx),
 261         &inline::Inline,
 262
 263         // Lowering generator control-flow and variables
 264         // has to happen before we do anything else to them.
 265         &generator::StateTransform,
 266
 267         &instcombine::InstCombine,
 268         &const_prop::ConstProp,
 269         &simplify_branches::SimplifyBranches::new("after-const-prop"),
 270         &deaggregator::Deaggregator,
 271         &copy_prop::CopyPropagation,
 272         &simplify_branches::SimplifyBranches::new("after-copy-prop"),
 273         &remove_noop_landing_pads::RemoveNoopLandingPads,
 274         &simplify::SimplifyCfg::new("final"),
 275         &simplify::SimplifyLocals,
 276
 277         &add_call_guards::CriticalCallEdges,
 278         &dump_mir::Marker("PreCodegen"),
 279     ]);
 280 }
 281
 282 fn optimized_mir(tcx: TyCtxt<'_>, def_id: DefId) -> &Body<'_> {
 283     if tcx.is_constructor(def_id) {
 284         // There's no reason to run all of the MIR passes on constructors when
 285         // we can just output the MIR we want directly. This also saves const
 286         // qualification and borrow checking the trouble of special casing
 287         // constructors.
 288         return shim::build_adt_ctor(tcx, def_id);
 289     }
 290
 291     // (Mir-)Borrowck uses `mir_validated`, so we have to force it to
 292     // execute before we can steal.
 293     tcx.ensure().mir_borrowck(def_id);
 294
 295     let (body, _) = tcx.mir_validated(def_id);
 296     let mut body = body.steal();
 297     run_optimization_passes(tcx, &mut body, def_id, None);
 298     tcx.arena.alloc(body)
 299 }
 300
 301 fn promoted_mir<'tcx>(tcx: TyCtxt<'tcx>, def_id: DefId) -> &'tcx IndexVec<Promoted, Body<'tcx>> {
 302     if tcx.is_constructor(def_id) {
 303         return tcx.intern_promoted(IndexVec::new());
 304     }
 305
 306     tcx.ensure().mir_borrowck(def_id);
 307     let (_, promoted) = tcx.mir_validated(def_id);
 308     let mut promoted = promoted.steal();
 309
 310     for (p, mut body) in promoted.iter_enumerated_mut() {
 311         run_optimization_passes(tcx, &mut body, def_id, Some(p));
 312     }
 313
 314     tcx.intern_promoted(promoted)
 315 }