src/librustc_mir/monomorphize/item.rs

   1 // Copyright 2016 The Rust Project Developers. See the COPYRIGHT
   2 // file at the top-level directory of this distribution and at
   3 // http://rust-lang.org/COPYRIGHT.
   4 //
   5 // Licensed under the Apache License, Version 2.0 <LICENSE-APACHE or
   6 // http://www.apache.org/licenses/LICENSE-2.0> or the MIT license
   7 // <LICENSE-MIT or http://opensource.org/licenses/MIT>, at your
   8 // option. This file may not be copied, modified, or distributed
   9 // except according to those terms.
  10
  11 //! Walks the crate looking for items/impl-items/trait-items that have
  12 //! either a `rustc_symbol_name` or `rustc_item_path` attribute and
  13 //! generates an error giving, respectively, the symbol name or
  14 //! item-path. This is used for unit testing the code that generates
  15 //! paths etc in all kinds of annoying scenarios.
  16
  17 use monomorphize::Instance;
  18 use rustc::hir;
  19 use rustc::hir::def_id::DefId;
  20 use rustc::session::config::OptLevel;
  21 use rustc::ty::{self, Ty, TyCtxt, ClosureSubsts, GeneratorSubsts};
  22 use rustc::ty::subst::Substs;
  23 use syntax::ast;
  24 use syntax::attr::InlineAttr;
  25 use std::fmt::{self, Write};
  26 use std::iter;
  27 use rustc::mir::mono::Linkage;
  28 use syntax_pos::symbol::Symbol;
  29 use syntax::codemap::Span;
  30 pub use rustc::mir::mono::MonoItem;
  31
  32 /// Describes how a monomorphization will be instantiated in object files.
  33 #[derive(PartialEq, Eq, Clone, Copy, Debug, Hash)]
  34 pub enum InstantiationMode {
  35     /// There will be exactly one instance of the given MonoItem. It will have
  36     /// external linkage so that it can be linked to from other codegen units.
  37     GloballyShared {
  38         /// In some compilation scenarios we may decide to take functions that
  39         /// are typically `LocalCopy` and instead move them to `GloballyShared`
  40         /// to avoid codegenning them a bunch of times. In this situation,
  41         /// however, our local copy may conflict with other crates also
  42         /// inlining the same function.
  43         ///
  44         /// This flag indicates that this situation is occurring, and informs
  45         /// symbol name calculation that some extra mangling is needed to
  46         /// avoid conflicts. Note that this may eventually go away entirely if
  47         /// ThinLTO enables us to *always* have a globally shared instance of a
  48         /// function within one crate's compilation.
  49         may_conflict: bool,
  50     },
  51
  52     /// Each codegen unit containing a reference to the given MonoItem will
  53     /// have its own private copy of the function (with internal linkage).
  54     LocalCopy,
  55 }
  56
  57 pub trait MonoItemExt<'a, 'tcx>: fmt::Debug {
  58     fn as_mono_item(&self) -> &MonoItem<'tcx>;
  59
  60     fn is_generic_fn(&self) -> bool {
  61         match *self.as_mono_item() {
  62             MonoItem::Fn(ref instance) => {
  63                 instance.substs.types().next().is_some()
  64             }
  65             MonoItem::Static(..) |
  66             MonoItem::CustomSection(..) |
  67             MonoItem::GlobalAsm(..) => false,
  68         }
  69     }
  70
  71     fn symbol_name(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> ty::SymbolName {
  72         match *self.as_mono_item() {
  73             MonoItem::Fn(instance) => tcx.symbol_name(instance),
  74             MonoItem::Static(def_id) => {
  75                 tcx.symbol_name(Instance::mono(tcx, def_id))
  76             }
  77             MonoItem::CustomSection(def_id) => {
  78                 tcx.symbol_name(Instance::mono(tcx, def_id))
  79             }
  80             MonoItem::GlobalAsm(node_id) => {
  81                 let def_id = tcx.hir.local_def_id(node_id);
  82                 ty::SymbolName {
  83                     name: Symbol::intern(&format!("global_asm_{:?}", def_id)).as_interned_str()
  84                 }
  85             }
  86         }
  87     }
  88     fn instantiation_mode(&self,
  89                           tcx: TyCtxt<'a, 'tcx, 'tcx>)
  90                           -> InstantiationMode {
  91         let inline_in_all_cgus =
  92             tcx.sess.opts.debugging_opts.inline_in_all_cgus.unwrap_or_else(|| {
  93                 tcx.sess.opts.optimize != OptLevel::No
  94             }) && !tcx.sess.opts.cg.link_dead_code;
  95
  96         match *self.as_mono_item() {
  97             MonoItem::Fn(ref instance) => {
  98                 let entry_def_id =
  99                     tcx.sess.entry_fn.borrow().map(|(id, _, _)| tcx.hir.local_def_id(id));
 100                 // If this function isn't inlined or otherwise has explicit
 101                 // linkage, then we'll be creating a globally shared version.
 102                 if self.explicit_linkage(tcx).is_some() ||
 103                     !instance.def.requires_local(tcx) ||
 104                     Some(instance.def_id()) == entry_def_id
 105                 {
 106                     return InstantiationMode::GloballyShared  { may_conflict: false }
 107                 }
 108
 109                 // At this point we don't have explicit linkage and we're an
 110                 // inlined function. If we're inlining into all CGUs then we'll
 111                 // be creating a local copy per CGU
 112                 if inline_in_all_cgus {
 113                     return InstantiationMode::LocalCopy
 114                 }
 115
 116                 // Finally, if this is `#[inline(always)]` we're sure to respect
 117                 // that with an inline copy per CGU, but otherwise we'll be
 118                 // creating one copy of this `#[inline]` function which may
 119                 // conflict with upstream crates as it could be an exported
 120                 // symbol.
 121                 match tcx.codegen_fn_attrs(instance.def_id()).inline {
 122                     InlineAttr::Always => InstantiationMode::LocalCopy,
 123                     _ => {
 124                         InstantiationMode::GloballyShared  { may_conflict: true }
 125                     }
 126                 }
 127             }
 128             MonoItem::Static(..) |
 129             MonoItem::CustomSection(..) |
 130             MonoItem::GlobalAsm(..) => {
 131                 InstantiationMode::GloballyShared { may_conflict: false }
 132             }
 133         }
 134     }
 135
 136     fn explicit_linkage(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Option<Linkage> {
 137         let def_id = match *self.as_mono_item() {
 138             MonoItem::Fn(ref instance) => instance.def_id(),
 139             MonoItem::Static(def_id) => def_id,
 140             MonoItem::CustomSection(..) => return None,
 141             MonoItem::GlobalAsm(..) => return None,
 142         };
 143
 144         let codegen_fn_attrs = tcx.codegen_fn_attrs(def_id);
 145         codegen_fn_attrs.linkage
 146     }
 147
 148     /// Returns whether this instance is instantiable - whether it has no unsatisfied
 149     /// predicates.
 150     ///
 151     /// In order to codegen an item, all of its predicates must hold, because
 152     /// otherwise the item does not make sense. Type-checking ensures that
 153     /// the predicates of every item that is *used by* a valid item *do*
 154     /// hold, so we can rely on that.
 155     ///
 156     /// However, we codegen collector roots (reachable items) and functions
 157     /// in vtables when they are seen, even if they are not used, and so they
 158     /// might not be instantiable. For example, a programmer can define this
 159     /// public function:
 160     ///
 161     ///     pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone {
 162     ///         <&mut () as Clone>::clone(&s);
 163     ///     }
 164     ///
 165     /// That function can't be codegened, because the method `<&mut () as Clone>::clone`
 166     /// does not exist. Luckily for us, that function can't ever be used,
 167     /// because that would require for `&'a mut (): Clone` to hold, so we
 168     /// can just not emit any code, or even a linker reference for it.
 169     ///
 170     /// Similarly, if a vtable method has such a signature, and therefore can't
 171     /// be used, we can just not emit it and have a placeholder (a null pointer,
 172     /// which will never be accessed) in its place.
 173     fn is_instantiable(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> bool {
 174         debug!("is_instantiable({:?})", self);
 175         let (def_id, substs) = match *self.as_mono_item() {
 176             MonoItem::Fn(ref instance) => (instance.def_id(), instance.substs),
 177             MonoItem::Static(def_id) => (def_id, Substs::empty()),
 178             MonoItem::CustomSection(..) => return true,
 179             // global asm never has predicates
 180             MonoItem::GlobalAsm(..) => return true
 181         };
 182
 183         tcx.substitute_normalize_and_test_predicates((def_id, &substs))
 184     }
 185
 186     fn to_string(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> String {
 187         return match *self.as_mono_item() {
 188             MonoItem::Fn(instance) => {
 189                 to_string_internal(tcx, "fn ", instance)
 190             },
 191             MonoItem::Static(def_id) => {
 192                 let instance = Instance::new(def_id, tcx.intern_substs(&[]));
 193                 to_string_internal(tcx, "static ", instance)
 194             },
 195             MonoItem::CustomSection(def_id) => {
 196                 let instance = Instance::new(def_id, tcx.intern_substs(&[]));
 197                 to_string_internal(tcx, "custom-section ", instance)
 198             },
 199             MonoItem::GlobalAsm(..) => {
 200                 "global_asm".to_string()
 201             }
 202         };
 203
 204         fn to_string_internal<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 205                                         prefix: &str,
 206                                         instance: Instance<'tcx>)
 207                                         -> String {
 208             let mut result = String::with_capacity(32);
 209             result.push_str(prefix);
 210             let printer = DefPathBasedNames::new(tcx, false, false);
 211             printer.push_instance_as_string(instance, &mut result);
 212             result
 213         }
 214     }
 215
 216     fn local_span(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Option<Span> {
 217         match *self.as_mono_item() {
 218             MonoItem::Fn(Instance { def, .. }) => {
 219                 tcx.hir.as_local_node_id(def.def_id())
 220             }
 221             MonoItem::Static(def_id) => {
 222                 tcx.hir.as_local_node_id(def_id)
 223             }
 224             MonoItem::CustomSection(def_id) => {
 225                 tcx.hir.as_local_node_id(def_id)
 226             }
 227             MonoItem::GlobalAsm(node_id) => {
 228                 Some(node_id)
 229             }
 230         }.map(|node_id| tcx.hir.span(node_id))
 231     }
 232 }
 233
 234 impl<'a, 'tcx> MonoItemExt<'a, 'tcx> for MonoItem<'tcx> {
 235     fn as_mono_item(&self) -> &MonoItem<'tcx> {
 236         self
 237     }
 238 }
 239
 240 //=-----------------------------------------------------------------------------
 241 // MonoItem String Keys
 242 //=-----------------------------------------------------------------------------
 243
 244 // The code below allows for producing a unique string key for a mono item.
 245 // These keys are used by the handwritten auto-tests, so they need to be
 246 // predictable and human-readable.
 247 //
 248 // Note: A lot of this could looks very similar to what's already in the
 249 //       ppaux module. It would be good to refactor things so we only have one
 250 //       parameterizable implementation for printing types.
 251
 252 /// Same as `unique_type_name()` but with the result pushed onto the given
 253 /// `output` parameter.
 254 pub struct DefPathBasedNames<'a, 'tcx: 'a> {
 255     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 256     omit_disambiguators: bool,
 257     omit_local_crate_name: bool,
 258 }
 259
 260 impl<'a, 'tcx> DefPathBasedNames<'a, 'tcx> {
 261     pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 262                omit_disambiguators: bool,
 263                omit_local_crate_name: bool)
 264                -> Self {
 265         DefPathBasedNames {
 266             tcx,
 267             omit_disambiguators,
 268             omit_local_crate_name,
 269         }
 270     }
 271
 272     pub fn push_type_name(&self, t: Ty<'tcx>, output: &mut String) {
 273         match t.sty {
 274             ty::TyBool              => output.push_str("bool"),
 275             ty::TyChar              => output.push_str("char"),
 276             ty::TyStr               => output.push_str("str"),
 277             ty::TyNever             => output.push_str("!"),
 278             ty::TyInt(ast::IntTy::Isize)    => output.push_str("isize"),
 279             ty::TyInt(ast::IntTy::I8)    => output.push_str("i8"),
 280             ty::TyInt(ast::IntTy::I16)   => output.push_str("i16"),
 281             ty::TyInt(ast::IntTy::I32)   => output.push_str("i32"),
 282             ty::TyInt(ast::IntTy::I64)   => output.push_str("i64"),
 283             ty::TyInt(ast::IntTy::I128)   => output.push_str("i128"),
 284             ty::TyUint(ast::UintTy::Usize)   => output.push_str("usize"),
 285             ty::TyUint(ast::UintTy::U8)   => output.push_str("u8"),
 286             ty::TyUint(ast::UintTy::U16)  => output.push_str("u16"),
 287             ty::TyUint(ast::UintTy::U32)  => output.push_str("u32"),
 288             ty::TyUint(ast::UintTy::U64)  => output.push_str("u64"),
 289             ty::TyUint(ast::UintTy::U128)  => output.push_str("u128"),
 290             ty::TyFloat(ast::FloatTy::F32) => output.push_str("f32"),
 291             ty::TyFloat(ast::FloatTy::F64) => output.push_str("f64"),
 292             ty::TyAdt(adt_def, substs) => {
 293                 self.push_def_path(adt_def.did, output);
 294                 self.push_type_params(substs, iter::empty(), output);
 295             },
 296             ty::TyTuple(component_types) => {
 297                 output.push('(');
 298                 for &component_type in component_types {
 299                     self.push_type_name(component_type, output);
 300                     output.push_str(", ");
 301                 }
 302                 if !component_types.is_empty() {
 303                     output.pop();
 304                     output.pop();
 305                 }
 306                 output.push(')');
 307             },
 308             ty::TyRawPtr(ty::TypeAndMut { ty: inner_type, mutbl } ) => {
 309                 output.push('*');
 310                 match mutbl {
 311                     hir::MutImmutable => output.push_str("const "),
 312                     hir::MutMutable => output.push_str("mut "),
 313                 }
 314
 315                 self.push_type_name(inner_type, output);
 316             },
 317             ty::TyRef(_, inner_type, mutbl) => {
 318                 output.push('&');
 319                 if mutbl == hir::MutMutable {
 320                     output.push_str("mut ");
 321                 }
 322
 323                 self.push_type_name(inner_type, output);
 324             },
 325             ty::TyArray(inner_type, len) => {
 326                 output.push('[');
 327                 self.push_type_name(inner_type, output);
 328                 write!(output, "; {}", len.unwrap_usize(self.tcx)).unwrap();
 329                 output.push(']');
 330             },
 331             ty::TySlice(inner_type) => {
 332                 output.push('[');
 333                 self.push_type_name(inner_type, output);
 334                 output.push(']');
 335             },
 336             ty::TyDynamic(ref trait_data, ..) => {
 337                 if let Some(principal) = trait_data.principal() {
 338                     self.push_def_path(principal.def_id(), output);
 339                     self.push_type_params(principal.skip_binder().substs,
 340                         trait_data.projection_bounds(),
 341                         output);
 342                 }
 343             },
 344             ty::TyForeign(did) => self.push_def_path(did, output),
 345             ty::TyFnDef(..) |
 346             ty::TyFnPtr(_) => {
 347                 let sig = t.fn_sig(self.tcx);
 348                 if sig.unsafety() == hir::Unsafety::Unsafe {
 349                     output.push_str("unsafe ");
 350                 }
 351
 352                 let abi = sig.abi();
 353                 if abi != ::rustc_target::spec::abi::Abi::Rust {
 354                     output.push_str("extern \"");
 355                     output.push_str(abi.name());
 356                     output.push_str("\" ");
 357                 }
 358
 359                 output.push_str("fn(");
 360
 361                 let sig = self.tcx.normalize_erasing_late_bound_regions(
 362                     ty::ParamEnv::reveal_all(),
 363                     &sig,
 364                 );
 365
 366                 if !sig.inputs().is_empty() {
 367                     for &parameter_type in sig.inputs() {
 368                         self.push_type_name(parameter_type, output);
 369                         output.push_str(", ");
 370                     }
 371                     output.pop();
 372                     output.pop();
 373                 }
 374
 375                 if sig.variadic {
 376                     if !sig.inputs().is_empty() {
 377                         output.push_str(", ...");
 378                     } else {
 379                         output.push_str("...");
 380                     }
 381                 }
 382
 383                 output.push(')');
 384
 385                 if !sig.output().is_nil() {
 386                     output.push_str(" -> ");
 387                     self.push_type_name(sig.output(), output);
 388                 }
 389             },
 390             ty::TyGenerator(def_id, GeneratorSubsts { ref substs }, _) |
 391             ty::TyClosure(def_id, ClosureSubsts { ref substs }) => {
 392                 self.push_def_path(def_id, output);
 393                 let generics = self.tcx.generics_of(self.tcx.closure_base_def_id(def_id));
 394                 let substs = substs.truncate_to(self.tcx, generics);
 395                 self.push_type_params(substs, iter::empty(), output);
 396             }
 397             ty::TyError |
 398             ty::TyInfer(_) |
 399             ty::TyProjection(..) |
 400             ty::TyParam(_) |
 401             ty::TyGeneratorWitness(_) |
 402             ty::TyAnon(..) => {
 403                 bug!("DefPathBasedNames: Trying to create type name for \
 404                                          unexpected type: {:?}", t);
 405             }
 406         }
 407     }
 408
 409     pub fn push_def_path(&self,
 410                          def_id: DefId,
 411                          output: &mut String) {
 412         let def_path = self.tcx.def_path(def_id);
 413
 414         // some_crate::
 415         if !(self.omit_local_crate_name && def_id.is_local()) {
 416             output.push_str(&self.tcx.crate_name(def_path.krate).as_str());
 417             output.push_str("::");
 418         }
 419
 420         // foo::bar::ItemName::
 421         for part in self.tcx.def_path(def_id).data {
 422             if self.omit_disambiguators {
 423                 write!(output, "{}::", part.data.as_interned_str()).unwrap();
 424             } else {
 425                 write!(output, "{}[{}]::",
 426                        part.data.as_interned_str(),
 427                        part.disambiguator).unwrap();
 428             }
 429         }
 430
 431         // remove final "::"
 432         output.pop();
 433         output.pop();
 434     }
 435
 436     fn push_type_params<I>(&self,
 437                             substs: &Substs<'tcx>,
 438                             projections: I,
 439                             output: &mut String)
 440         where I: Iterator<Item=ty::PolyExistentialProjection<'tcx>>
 441     {
 442         let mut projections = projections.peekable();
 443         if substs.types().next().is_none() && projections.peek().is_none() {
 444             return;
 445         }
 446
 447         output.push('<');
 448
 449         for type_parameter in substs.types() {
 450             self.push_type_name(type_parameter, output);
 451             output.push_str(", ");
 452         }
 453
 454         for projection in projections {
 455             let projection = projection.skip_binder();
 456             let name = &self.tcx.associated_item(projection.item_def_id).ident.as_str();
 457             output.push_str(name);
 458             output.push_str("=");
 459             self.push_type_name(projection.ty, output);
 460             output.push_str(", ");
 461         }
 462
 463         output.pop();
 464         output.pop();
 465
 466         output.push('>');
 467     }
 468
 469     pub fn push_instance_as_string(&self,
 470                                    instance: Instance<'tcx>,
 471                                    output: &mut String) {
 472         self.push_def_path(instance.def_id(), output);
 473         self.push_type_params(instance.substs, iter::empty(), output);
 474     }
 475 }