src/librustc_mir/monomorphize/item.rs

   1 use crate::monomorphize::Instance;
   2 use rustc::hir;
   3 use rustc::hir::def_id::{DefId, LOCAL_CRATE};
   4 use rustc::mir::interpret::ConstValue;
   5 use rustc::session::config::OptLevel;
   6 use rustc::ty::{self, Ty, TyCtxt, Const, ClosureSubsts, GeneratorSubsts};
   7 use rustc::ty::subst::{SubstsRef, InternalSubsts};
   8 use syntax::ast;
   9 use syntax::attr::InlineAttr;
  10 use std::fmt::{self, Write};
  11 use std::iter;
  12 use rustc::mir::mono::Linkage;
  13 use syntax_pos::symbol::InternedString;
  14 use syntax::source_map::Span;
  15 pub use rustc::mir::mono::MonoItem;
  16
  17 /// Describes how a monomorphization will be instantiated in object files.
  18 #[derive(PartialEq, Eq, Clone, Copy, Debug, Hash)]
  19 pub enum InstantiationMode {
  20     /// There will be exactly one instance of the given MonoItem. It will have
  21     /// external linkage so that it can be linked to from other codegen units.
  22     GloballyShared {
  23         /// In some compilation scenarios we may decide to take functions that
  24         /// are typically `LocalCopy` and instead move them to `GloballyShared`
  25         /// to avoid codegenning them a bunch of times. In this situation,
  26         /// however, our local copy may conflict with other crates also
  27         /// inlining the same function.
  28         ///
  29         /// This flag indicates that this situation is occurring, and informs
  30         /// symbol name calculation that some extra mangling is needed to
  31         /// avoid conflicts. Note that this may eventually go away entirely if
  32         /// ThinLTO enables us to *always* have a globally shared instance of a
  33         /// function within one crate's compilation.
  34         may_conflict: bool,
  35     },
  36
  37     /// Each codegen unit containing a reference to the given MonoItem will
  38     /// have its own private copy of the function (with internal linkage).
  39     LocalCopy,
  40 }
  41
  42 pub trait MonoItemExt<'a, 'tcx>: fmt::Debug {
  43     fn as_mono_item(&self) -> &MonoItem<'tcx>;
  44
  45     fn is_generic_fn(&self) -> bool {
  46         match *self.as_mono_item() {
  47             MonoItem::Fn(ref instance) => {
  48                 instance.substs.non_erasable_generics().next().is_some()
  49             }
  50             MonoItem::Static(..) |
  51             MonoItem::GlobalAsm(..) => false,
  52         }
  53     }
  54
  55     fn symbol_name(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> ty::SymbolName {
  56         match *self.as_mono_item() {
  57             MonoItem::Fn(instance) => tcx.symbol_name(instance),
  58             MonoItem::Static(def_id) => {
  59                 tcx.symbol_name(Instance::mono(tcx, def_id))
  60             }
  61             MonoItem::GlobalAsm(hir_id) => {
  62                 let def_id = tcx.hir().local_def_id_from_hir_id(hir_id);
  63                 ty::SymbolName {
  64                     name: InternedString::intern(&format!("global_asm_{:?}", def_id))
  65                 }
  66             }
  67         }
  68     }
  69     fn instantiation_mode(&self,
  70                           tcx: TyCtxt<'a, 'tcx, 'tcx>)
  71                           -> InstantiationMode {
  72         let inline_in_all_cgus =
  73             tcx.sess.opts.debugging_opts.inline_in_all_cgus.unwrap_or_else(|| {
  74                 tcx.sess.opts.optimize != OptLevel::No
  75             }) && !tcx.sess.opts.cg.link_dead_code;
  76
  77         match *self.as_mono_item() {
  78             MonoItem::Fn(ref instance) => {
  79                 let entry_def_id = tcx.entry_fn(LOCAL_CRATE).map(|(id, _)| id);
  80                 // If this function isn't inlined or otherwise has explicit
  81                 // linkage, then we'll be creating a globally shared version.
  82                 if self.explicit_linkage(tcx).is_some() ||
  83                     !instance.def.requires_local(tcx) ||
  84                     Some(instance.def_id()) == entry_def_id
  85                 {
  86                     return InstantiationMode::GloballyShared  { may_conflict: false }
  87                 }
  88
  89                 // At this point we don't have explicit linkage and we're an
  90                 // inlined function. If we're inlining into all CGUs then we'll
  91                 // be creating a local copy per CGU
  92                 if inline_in_all_cgus {
  93                     return InstantiationMode::LocalCopy
  94                 }
  95
  96                 // Finally, if this is `#[inline(always)]` we're sure to respect
  97                 // that with an inline copy per CGU, but otherwise we'll be
  98                 // creating one copy of this `#[inline]` function which may
  99                 // conflict with upstream crates as it could be an exported
 100                 // symbol.
 101                 match tcx.codegen_fn_attrs(instance.def_id()).inline {
 102                     InlineAttr::Always => InstantiationMode::LocalCopy,
 103                     _ => {
 104                         InstantiationMode::GloballyShared  { may_conflict: true }
 105                     }
 106                 }
 107             }
 108             MonoItem::Static(..) |
 109             MonoItem::GlobalAsm(..) => {
 110                 InstantiationMode::GloballyShared { may_conflict: false }
 111             }
 112         }
 113     }
 114
 115     fn explicit_linkage(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Option<Linkage> {
 116         let def_id = match *self.as_mono_item() {
 117             MonoItem::Fn(ref instance) => instance.def_id(),
 118             MonoItem::Static(def_id) => def_id,
 119             MonoItem::GlobalAsm(..) => return None,
 120         };
 121
 122         let codegen_fn_attrs = tcx.codegen_fn_attrs(def_id);
 123         codegen_fn_attrs.linkage
 124     }
 125
 126     /// Returns `true` if this instance is instantiable - whether it has no unsatisfied
 127     /// predicates.
 128     ///
 129     /// In order to codegen an item, all of its predicates must hold, because
 130     /// otherwise the item does not make sense. Type-checking ensures that
 131     /// the predicates of every item that is *used by* a valid item *do*
 132     /// hold, so we can rely on that.
 133     ///
 134     /// However, we codegen collector roots (reachable items) and functions
 135     /// in vtables when they are seen, even if they are not used, and so they
 136     /// might not be instantiable. For example, a programmer can define this
 137     /// public function:
 138     ///
 139     ///     pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone {
 140     ///         <&mut () as Clone>::clone(&s);
 141     ///     }
 142     ///
 143     /// That function can't be codegened, because the method `<&mut () as Clone>::clone`
 144     /// does not exist. Luckily for us, that function can't ever be used,
 145     /// because that would require for `&'a mut (): Clone` to hold, so we
 146     /// can just not emit any code, or even a linker reference for it.
 147     ///
 148     /// Similarly, if a vtable method has such a signature, and therefore can't
 149     /// be used, we can just not emit it and have a placeholder (a null pointer,
 150     /// which will never be accessed) in its place.
 151     fn is_instantiable(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> bool {
 152         debug!("is_instantiable({:?})", self);
 153         let (def_id, substs) = match *self.as_mono_item() {
 154             MonoItem::Fn(ref instance) => (instance.def_id(), instance.substs),
 155             MonoItem::Static(def_id) => (def_id, InternalSubsts::empty()),
 156             // global asm never has predicates
 157             MonoItem::GlobalAsm(..) => return true
 158         };
 159
 160         tcx.substitute_normalize_and_test_predicates((def_id, &substs))
 161     }
 162
 163     fn to_string(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>, debug: bool) -> String {
 164         return match *self.as_mono_item() {
 165             MonoItem::Fn(instance) => {
 166                 to_string_internal(tcx, "fn ", instance, debug)
 167             },
 168             MonoItem::Static(def_id) => {
 169                 let instance = Instance::new(def_id, tcx.intern_substs(&[]));
 170                 to_string_internal(tcx, "static ", instance, debug)
 171             },
 172             MonoItem::GlobalAsm(..) => {
 173                 "global_asm".to_string()
 174             }
 175         };
 176
 177         fn to_string_internal<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 178                                         prefix: &str,
 179                                         instance: Instance<'tcx>,
 180                                         debug: bool)
 181                                         -> String {
 182             let mut result = String::with_capacity(32);
 183             result.push_str(prefix);
 184             let printer = DefPathBasedNames::new(tcx, false, false);
 185             printer.push_instance_as_string(instance, &mut result, debug);
 186             result
 187         }
 188     }
 189
 190     fn local_span(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Option<Span> {
 191         match *self.as_mono_item() {
 192             MonoItem::Fn(Instance { def, .. }) => {
 193                 tcx.hir().as_local_hir_id(def.def_id())
 194             }
 195             MonoItem::Static(def_id) => {
 196                 tcx.hir().as_local_hir_id(def_id)
 197             }
 198             MonoItem::GlobalAsm(hir_id) => {
 199                 Some(hir_id)
 200             }
 201         }.map(|hir_id| tcx.hir().span_by_hir_id(hir_id))
 202     }
 203 }
 204
 205 impl<'a, 'tcx> MonoItemExt<'a, 'tcx> for MonoItem<'tcx> {
 206     fn as_mono_item(&self) -> &MonoItem<'tcx> {
 207         self
 208     }
 209 }
 210
 211 //=-----------------------------------------------------------------------------
 212 // MonoItem String Keys
 213 //=-----------------------------------------------------------------------------
 214
 215 // The code below allows for producing a unique string key for a mono item.
 216 // These keys are used by the handwritten auto-tests, so they need to be
 217 // predictable and human-readable.
 218 //
 219 // Note: A lot of this could looks very similar to what's already in `ty::print`.
 220 // FIXME(eddyb) implement a custom `PrettyPrinter` for this.
 221
 222 /// Same as `unique_type_name()` but with the result pushed onto the given
 223 /// `output` parameter.
 224 pub struct DefPathBasedNames<'a, 'tcx: 'a> {
 225     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 226     omit_disambiguators: bool,
 227     omit_local_crate_name: bool,
 228 }
 229
 230 impl<'a, 'tcx> DefPathBasedNames<'a, 'tcx> {
 231     pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 232                omit_disambiguators: bool,
 233                omit_local_crate_name: bool)
 234                -> Self {
 235         DefPathBasedNames {
 236             tcx,
 237             omit_disambiguators,
 238             omit_local_crate_name,
 239         }
 240     }
 241
 242     // Pushes the type name of the specified type to the provided string.
 243     // If `debug` is true, printing normally unprintable types is allowed
 244     // (e.g. `ty::GeneratorWitness`). This parameter should only be set when
 245     // this method is being used for logging purposes (e.g. with `debug!` or `info!`)
 246     // When being used for codegen purposes, `debug` should be set to `false`
 247     // in order to catch unexpected types that should never end up in a type name.
 248     pub fn push_type_name(&self, t: Ty<'tcx>, output: &mut String, debug: bool) {
 249         match t.sty {
 250             ty::Bool              => output.push_str("bool"),
 251             ty::Char              => output.push_str("char"),
 252             ty::Str               => output.push_str("str"),
 253             ty::Never             => output.push_str("!"),
 254             ty::Int(ast::IntTy::Isize)    => output.push_str("isize"),
 255             ty::Int(ast::IntTy::I8)    => output.push_str("i8"),
 256             ty::Int(ast::IntTy::I16)   => output.push_str("i16"),
 257             ty::Int(ast::IntTy::I32)   => output.push_str("i32"),
 258             ty::Int(ast::IntTy::I64)   => output.push_str("i64"),
 259             ty::Int(ast::IntTy::I128)   => output.push_str("i128"),
 260             ty::Uint(ast::UintTy::Usize)   => output.push_str("usize"),
 261             ty::Uint(ast::UintTy::U8)   => output.push_str("u8"),
 262             ty::Uint(ast::UintTy::U16)  => output.push_str("u16"),
 263             ty::Uint(ast::UintTy::U32)  => output.push_str("u32"),
 264             ty::Uint(ast::UintTy::U64)  => output.push_str("u64"),
 265             ty::Uint(ast::UintTy::U128)  => output.push_str("u128"),
 266             ty::Float(ast::FloatTy::F32) => output.push_str("f32"),
 267             ty::Float(ast::FloatTy::F64) => output.push_str("f64"),
 268             ty::Adt(adt_def, substs) => {
 269                 self.push_def_path(adt_def.did, output);
 270                 self.push_generic_params(substs, iter::empty(), output, debug);
 271             },
 272             ty::Tuple(component_types) => {
 273                 output.push('(');
 274                 for &component_type in component_types {
 275                     self.push_type_name(component_type.expect_ty(), output, debug);
 276                     output.push_str(", ");
 277                 }
 278                 if !component_types.is_empty() {
 279                     output.pop();
 280                     output.pop();
 281                 }
 282                 output.push(')');
 283             },
 284             ty::RawPtr(ty::TypeAndMut { ty: inner_type, mutbl } ) => {
 285                 output.push('*');
 286                 match mutbl {
 287                     hir::MutImmutable => output.push_str("const "),
 288                     hir::MutMutable => output.push_str("mut "),
 289                 }
 290
 291                 self.push_type_name(inner_type, output, debug);
 292             },
 293             ty::Ref(_, inner_type, mutbl) => {
 294                 output.push('&');
 295                 if mutbl == hir::MutMutable {
 296                     output.push_str("mut ");
 297                 }
 298
 299                 self.push_type_name(inner_type, output, debug);
 300             },
 301             ty::Array(inner_type, len) => {
 302                 output.push('[');
 303                 self.push_type_name(inner_type, output, debug);
 304                 write!(output, "; {}", len.unwrap_usize(self.tcx)).unwrap();
 305                 output.push(']');
 306             },
 307             ty::Slice(inner_type) => {
 308                 output.push('[');
 309                 self.push_type_name(inner_type, output, debug);
 310                 output.push(']');
 311             },
 312             ty::Dynamic(ref trait_data, ..) => {
 313                 if let Some(principal) = trait_data.principal() {
 314                     self.push_def_path(principal.def_id(), output);
 315                     self.push_generic_params(
 316                         principal.skip_binder().substs,
 317                         trait_data.projection_bounds(),
 318                         output,
 319                         debug
 320                     );
 321                 } else {
 322                     output.push_str("dyn '_");
 323                 }
 324             },
 325             ty::Foreign(did) => self.push_def_path(did, output),
 326             ty::FnDef(..) |
 327             ty::FnPtr(_) => {
 328                 let sig = t.fn_sig(self.tcx);
 329                 if sig.unsafety() == hir::Unsafety::Unsafe {
 330                     output.push_str("unsafe ");
 331                 }
 332
 333                 let abi = sig.abi();
 334                 if abi != ::rustc_target::spec::abi::Abi::Rust {
 335                     output.push_str("extern \"");
 336                     output.push_str(abi.name());
 337                     output.push_str("\" ");
 338                 }
 339
 340                 output.push_str("fn(");
 341
 342                 let sig = self.tcx.normalize_erasing_late_bound_regions(
 343                     ty::ParamEnv::reveal_all(),
 344                     &sig,
 345                 );
 346
 347                 if !sig.inputs().is_empty() {
 348                     for &parameter_type in sig.inputs() {
 349                         self.push_type_name(parameter_type, output, debug);
 350                         output.push_str(", ");
 351                     }
 352                     output.pop();
 353                     output.pop();
 354                 }
 355
 356                 if sig.c_variadic {
 357                     if !sig.inputs().is_empty() {
 358                         output.push_str(", ...");
 359                     } else {
 360                         output.push_str("...");
 361                     }
 362                 }
 363
 364                 output.push(')');
 365
 366                 if !sig.output().is_unit() {
 367                     output.push_str(" -> ");
 368                     self.push_type_name(sig.output(), output, debug);
 369                 }
 370             },
 371             ty::Generator(def_id, GeneratorSubsts { ref substs }, _) |
 372             ty::Closure(def_id, ClosureSubsts { ref substs }) => {
 373                 self.push_def_path(def_id, output);
 374                 let generics = self.tcx.generics_of(self.tcx.closure_base_def_id(def_id));
 375                 let substs = substs.truncate_to(self.tcx, generics);
 376                 self.push_generic_params(substs, iter::empty(), output, debug);
 377             }
 378             ty::Error |
 379             ty::Bound(..) |
 380             ty::Infer(_) |
 381             ty::Placeholder(..) |
 382             ty::UnnormalizedProjection(..) |
 383             ty::Projection(..) |
 384             ty::Param(_) |
 385             ty::GeneratorWitness(_) |
 386             ty::Opaque(..) => {
 387                 if debug {
 388                     output.push_str(&format!("`{:?}`", t));
 389                 } else {
 390                     bug!(
 391                         "DefPathBasedNames: trying to create type name for unexpected type: {:?}",
 392                         t,
 393                     );
 394                 }
 395             }
 396         }
 397     }
 398
 399     // Pushes the the name of the specified const to the provided string.
 400     // If `debug` is true, usually-unprintable consts (such as `Infer`) will be printed,
 401     // as well as the unprintable types of constants (see `push_type_name` for more details).
 402     pub fn push_const_name(&self, c: &Const<'tcx>, output: &mut String, debug: bool) {
 403         match c.val {
 404             ConstValue::Scalar(..) | ConstValue::Slice(..) | ConstValue::ByRef(..) => {
 405                 // FIXME(const_generics): we could probably do a better job here.
 406                 write!(output, "{:?}", c).unwrap()
 407             }
 408             _ => {
 409                 if debug {
 410                     write!(output, "{:?}", c).unwrap()
 411                 } else {
 412                     bug!(
 413                         "DefPathBasedNames: trying to create const name for unexpected const: {:?}",
 414                         c,
 415                     );
 416                 }
 417             }
 418         }
 419         output.push_str(": ");
 420         self.push_type_name(c.ty, output, debug);
 421     }
 422
 423     pub fn push_def_path(&self,
 424                          def_id: DefId,
 425                          output: &mut String) {
 426         let def_path = self.tcx.def_path(def_id);
 427
 428         // some_crate::
 429         if !(self.omit_local_crate_name && def_id.is_local()) {
 430             output.push_str(&self.tcx.crate_name(def_path.krate).as_str());
 431             output.push_str("::");
 432         }
 433
 434         // foo::bar::ItemName::
 435         for part in self.tcx.def_path(def_id).data {
 436             if self.omit_disambiguators {
 437                 write!(output, "{}::", part.data.as_interned_str()).unwrap();
 438             } else {
 439                 write!(output, "{}[{}]::",
 440                        part.data.as_interned_str(),
 441                        part.disambiguator).unwrap();
 442             }
 443         }
 444
 445         // remove final "::"
 446         output.pop();
 447         output.pop();
 448     }
 449
 450     fn push_generic_params<I>(
 451         &self,
 452         substs: SubstsRef<'tcx>,
 453         projections: I,
 454         output: &mut String,
 455         debug: bool,
 456     ) where I: Iterator<Item=ty::PolyExistentialProjection<'tcx>> {
 457         let mut projections = projections.peekable();
 458         if substs.non_erasable_generics().next().is_none() && projections.peek().is_none() {
 459             return;
 460         }
 461
 462         output.push('<');
 463
 464         for type_parameter in substs.types() {
 465             self.push_type_name(type_parameter, output, debug);
 466             output.push_str(", ");
 467         }
 468
 469         for projection in projections {
 470             let projection = projection.skip_binder();
 471             let name = &self.tcx.associated_item(projection.item_def_id).ident.as_str();
 472             output.push_str(name);
 473             output.push_str("=");
 474             self.push_type_name(projection.ty, output, debug);
 475             output.push_str(", ");
 476         }
 477
 478         for const_parameter in substs.consts() {
 479             self.push_const_name(const_parameter, output, debug);
 480             output.push_str(", ");
 481         }
 482
 483         output.pop();
 484         output.pop();
 485
 486         output.push('>');
 487     }
 488
 489     pub fn push_instance_as_string(&self,
 490                                    instance: Instance<'tcx>,
 491                                    output: &mut String,
 492                                    debug: bool) {
 493         self.push_def_path(instance.def_id(), output);
 494         self.push_generic_params(instance.substs, iter::empty(), output, debug);
 495     }
 496 }