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};
  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 translation item 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 translating 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::GlobalAsm(..) => false,
  67         }
  68     }
  69
  70     fn symbol_name(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> ty::SymbolName {
  71         match *self.as_mono_item() {
  72             MonoItem::Fn(instance) => tcx.symbol_name(instance),
  73             MonoItem::Static(def_id) => {
  74                 tcx.symbol_name(Instance::mono(tcx, def_id))
  75             }
  76             MonoItem::GlobalAsm(node_id) => {
  77                 let def_id = tcx.hir.local_def_id(node_id);
  78                 ty::SymbolName {
  79                     name: Symbol::intern(&format!("global_asm_{:?}", def_id)).as_interned_str()
  80                 }
  81             }
  82         }
  83     }
  84     fn instantiation_mode(&self,
  85                           tcx: TyCtxt<'a, 'tcx, 'tcx>)
  86                           -> InstantiationMode {
  87         let inline_in_all_cgus =
  88             tcx.sess.opts.debugging_opts.inline_in_all_cgus.unwrap_or_else(|| {
  89                 tcx.sess.opts.optimize != OptLevel::No
  90             }) && !tcx.sess.opts.cg.link_dead_code;
  91
  92         match *self.as_mono_item() {
  93             MonoItem::Fn(ref instance) => {
  94                 let entry_def_id =
  95                     tcx.sess.entry_fn.borrow().map(|(id, _, _)| tcx.hir.local_def_id(id));
  96                 // If this function isn't inlined or otherwise has explicit
  97                 // linkage, then we'll be creating a globally shared version.
  98                 if self.explicit_linkage(tcx).is_some() ||
  99                     !instance.def.requires_local(tcx) ||
 100                     Some(instance.def_id()) == entry_def_id
 101                 {
 102                     return InstantiationMode::GloballyShared  { may_conflict: false }
 103                 }
 104
 105                 // At this point we don't have explicit linkage and we're an
 106                 // inlined function. If we're inlining into all CGUs then we'll
 107                 // be creating a local copy per CGU
 108                 if inline_in_all_cgus {
 109                     return InstantiationMode::LocalCopy
 110                 }
 111
 112                 // Finally, if this is `#[inline(always)]` we're sure to respect
 113                 // that with an inline copy per CGU, but otherwise we'll be
 114                 // creating one copy of this `#[inline]` function which may
 115                 // conflict with upstream crates as it could be an exported
 116                 // symbol.
 117                 match tcx.trans_fn_attrs(instance.def_id()).inline {
 118                     InlineAttr::Always => InstantiationMode::LocalCopy,
 119                     _ => {
 120                         InstantiationMode::GloballyShared  { may_conflict: true }
 121                     }
 122                 }
 123             }
 124             MonoItem::Static(..) => {
 125                 InstantiationMode::GloballyShared { may_conflict: false }
 126             }
 127             MonoItem::GlobalAsm(..) => {
 128                 InstantiationMode::GloballyShared { may_conflict: false }
 129             }
 130         }
 131     }
 132
 133     fn explicit_linkage(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Option<Linkage> {
 134         let def_id = match *self.as_mono_item() {
 135             MonoItem::Fn(ref instance) => instance.def_id(),
 136             MonoItem::Static(def_id) => def_id,
 137             MonoItem::GlobalAsm(..) => return None,
 138         };
 139
 140         let trans_fn_attrs = tcx.trans_fn_attrs(def_id);
 141         trans_fn_attrs.linkage
 142     }
 143
 144     /// Returns whether this instance is instantiable - whether it has no unsatisfied
 145     /// predicates.
 146     ///
 147     /// In order to translate an item, all of its predicates must hold, because
 148     /// otherwise the item does not make sense. Type-checking ensures that
 149     /// the predicates of every item that is *used by* a valid item *do*
 150     /// hold, so we can rely on that.
 151     ///
 152     /// However, we translate collector roots (reachable items) and functions
 153     /// in vtables when they are seen, even if they are not used, and so they
 154     /// might not be instantiable. For example, a programmer can define this
 155     /// public function:
 156     ///
 157     ///     pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone {
 158     ///         <&mut () as Clone>::clone(&s);
 159     ///     }
 160     ///
 161     /// That function can't be translated, because the method `<&mut () as Clone>::clone`
 162     /// does not exist. Luckily for us, that function can't ever be used,
 163     /// because that would require for `&'a mut (): Clone` to hold, so we
 164     /// can just not emit any code, or even a linker reference for it.
 165     ///
 166     /// Similarly, if a vtable method has such a signature, and therefore can't
 167     /// be used, we can just not emit it and have a placeholder (a null pointer,
 168     /// which will never be accessed) in its place.
 169     fn is_instantiable(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> bool {
 170         debug!("is_instantiable({:?})", self);
 171         let (def_id, substs) = match *self.as_mono_item() {
 172             MonoItem::Fn(ref instance) => (instance.def_id(), instance.substs),
 173             MonoItem::Static(def_id) => (def_id, Substs::empty()),
 174             // global asm never has predicates
 175             MonoItem::GlobalAsm(..) => return true
 176         };
 177
 178         tcx.substitute_normalize_and_test_predicates((def_id, &substs))
 179     }
 180
 181     fn to_string(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> String {
 182         return match *self.as_mono_item() {
 183             MonoItem::Fn(instance) => {
 184                 to_string_internal(tcx, "fn ", instance)
 185             },
 186             MonoItem::Static(def_id) => {
 187                 let instance = Instance::new(def_id, tcx.intern_substs(&[]));
 188                 to_string_internal(tcx, "static ", instance)
 189             },
 190             MonoItem::GlobalAsm(..) => {
 191                 "global_asm".to_string()
 192             }
 193         };
 194
 195         fn to_string_internal<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 196                                         prefix: &str,
 197                                         instance: Instance<'tcx>)
 198                                         -> String {
 199             let mut result = String::with_capacity(32);
 200             result.push_str(prefix);
 201             let printer = DefPathBasedNames::new(tcx, false, false);
 202             printer.push_instance_as_string(instance, &mut result);
 203             result
 204         }
 205     }
 206
 207     fn local_span(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Option<Span> {
 208         match *self.as_mono_item() {
 209             MonoItem::Fn(Instance { def, .. }) => {
 210                 tcx.hir.as_local_node_id(def.def_id())
 211             }
 212             MonoItem::Static(def_id) => {
 213                 tcx.hir.as_local_node_id(def_id)
 214             }
 215             MonoItem::GlobalAsm(node_id) => {
 216                 Some(node_id)
 217             }
 218         }.map(|node_id| tcx.hir.span(node_id))
 219     }
 220 }
 221
 222 impl<'a, 'tcx> MonoItemExt<'a, 'tcx> for MonoItem<'tcx> {
 223     fn as_mono_item(&self) -> &MonoItem<'tcx> {
 224         self
 225     }
 226 }
 227
 228 //=-----------------------------------------------------------------------------
 229 // MonoItem String Keys
 230 //=-----------------------------------------------------------------------------
 231
 232 // The code below allows for producing a unique string key for a trans item.
 233 // These keys are used by the handwritten auto-tests, so they need to be
 234 // predictable and human-readable.
 235 //
 236 // Note: A lot of this could looks very similar to what's already in the
 237 //       ppaux module. It would be good to refactor things so we only have one
 238 //       parameterizable implementation for printing types.
 239
 240 /// Same as `unique_type_name()` but with the result pushed onto the given
 241 /// `output` parameter.
 242 pub struct DefPathBasedNames<'a, 'tcx: 'a> {
 243     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 244     omit_disambiguators: bool,
 245     omit_local_crate_name: bool,
 246 }
 247
 248 impl<'a, 'tcx> DefPathBasedNames<'a, 'tcx> {
 249     pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 250                omit_disambiguators: bool,
 251                omit_local_crate_name: bool)
 252                -> Self {
 253         DefPathBasedNames {
 254             tcx,
 255             omit_disambiguators,
 256             omit_local_crate_name,
 257         }
 258     }
 259
 260     pub fn push_type_name(&self, t: Ty<'tcx>, output: &mut String) {
 261         match t.sty {
 262             ty::TyBool              => output.push_str("bool"),
 263             ty::TyChar              => output.push_str("char"),
 264             ty::TyStr               => output.push_str("str"),
 265             ty::TyNever             => output.push_str("!"),
 266             ty::TyInt(ast::IntTy::Isize)    => output.push_str("isize"),
 267             ty::TyInt(ast::IntTy::I8)    => output.push_str("i8"),
 268             ty::TyInt(ast::IntTy::I16)   => output.push_str("i16"),
 269             ty::TyInt(ast::IntTy::I32)   => output.push_str("i32"),
 270             ty::TyInt(ast::IntTy::I64)   => output.push_str("i64"),
 271             ty::TyInt(ast::IntTy::I128)   => output.push_str("i128"),
 272             ty::TyUint(ast::UintTy::Usize)   => output.push_str("usize"),
 273             ty::TyUint(ast::UintTy::U8)   => output.push_str("u8"),
 274             ty::TyUint(ast::UintTy::U16)  => output.push_str("u16"),
 275             ty::TyUint(ast::UintTy::U32)  => output.push_str("u32"),
 276             ty::TyUint(ast::UintTy::U64)  => output.push_str("u64"),
 277             ty::TyUint(ast::UintTy::U128)  => output.push_str("u128"),
 278             ty::TyFloat(ast::FloatTy::F32) => output.push_str("f32"),
 279             ty::TyFloat(ast::FloatTy::F64) => output.push_str("f64"),
 280             ty::TyAdt(adt_def, substs) => {
 281                 self.push_def_path(adt_def.did, output);
 282                 self.push_type_params(substs, iter::empty(), output);
 283             },
 284             ty::TyTuple(component_types) => {
 285                 output.push('(');
 286                 for &component_type in component_types {
 287                     self.push_type_name(component_type, output);
 288                     output.push_str(", ");
 289                 }
 290                 if !component_types.is_empty() {
 291                     output.pop();
 292                     output.pop();
 293                 }
 294                 output.push(')');
 295             },
 296             ty::TyRawPtr(ty::TypeAndMut { ty: inner_type, mutbl } ) => {
 297                 output.push('*');
 298                 match mutbl {
 299                     hir::MutImmutable => output.push_str("const "),
 300                     hir::MutMutable => output.push_str("mut "),
 301                 }
 302
 303                 self.push_type_name(inner_type, output);
 304             },
 305             ty::TyRef(_, ty::TypeAndMut { ty: inner_type, mutbl }) => {
 306                 output.push('&');
 307                 if mutbl == hir::MutMutable {
 308                     output.push_str("mut ");
 309                 }
 310
 311                 self.push_type_name(inner_type, output);
 312             },
 313             ty::TyArray(inner_type, len) => {
 314                 output.push('[');
 315                 self.push_type_name(inner_type, output);
 316                 write!(output, "; {}",
 317                     len.val.unwrap_u64()).unwrap();
 318                 output.push(']');
 319             },
 320             ty::TySlice(inner_type) => {
 321                 output.push('[');
 322                 self.push_type_name(inner_type, output);
 323                 output.push(']');
 324             },
 325             ty::TyDynamic(ref trait_data, ..) => {
 326                 if let Some(principal) = trait_data.principal() {
 327                     self.push_def_path(principal.def_id(), output);
 328                     self.push_type_params(principal.skip_binder().substs,
 329                         trait_data.projection_bounds(),
 330                         output);
 331                 }
 332             },
 333             ty::TyForeign(did) => self.push_def_path(did, output),
 334             ty::TyFnDef(..) |
 335             ty::TyFnPtr(_) => {
 336                 let sig = t.fn_sig(self.tcx);
 337                 if sig.unsafety() == hir::Unsafety::Unsafe {
 338                     output.push_str("unsafe ");
 339                 }
 340
 341                 let abi = sig.abi();
 342                 if abi != ::rustc_target::spec::abi::Abi::Rust {
 343                     output.push_str("extern \"");
 344                     output.push_str(abi.name());
 345                     output.push_str("\" ");
 346                 }
 347
 348                 output.push_str("fn(");
 349
 350                 let sig = self.tcx.normalize_erasing_late_bound_regions(
 351                     ty::ParamEnv::reveal_all(),
 352                     &sig,
 353                 );
 354
 355                 if !sig.inputs().is_empty() {
 356                     for &parameter_type in sig.inputs() {
 357                         self.push_type_name(parameter_type, output);
 358                         output.push_str(", ");
 359                     }
 360                     output.pop();
 361                     output.pop();
 362                 }
 363
 364                 if sig.variadic {
 365                     if !sig.inputs().is_empty() {
 366                         output.push_str(", ...");
 367                     } else {
 368                         output.push_str("...");
 369                     }
 370                 }
 371
 372                 output.push(')');
 373
 374                 if !sig.output().is_nil() {
 375                     output.push_str(" -> ");
 376                     self.push_type_name(sig.output(), output);
 377                 }
 378             },
 379             ty::TyGenerator(def_id, ref closure_substs, _) |
 380             ty::TyClosure(def_id, ref closure_substs) => {
 381                 self.push_def_path(def_id, output);
 382                 let generics = self.tcx.generics_of(self.tcx.closure_base_def_id(def_id));
 383                 let substs = closure_substs.substs.truncate_to(self.tcx, generics);
 384                 self.push_type_params(substs, iter::empty(), output);
 385             }
 386             ty::TyError |
 387             ty::TyInfer(_) |
 388             ty::TyProjection(..) |
 389             ty::TyParam(_) |
 390             ty::TyGeneratorWitness(_) |
 391             ty::TyAnon(..) => {
 392                 bug!("DefPathBasedNames: Trying to create type name for \
 393                                          unexpected type: {:?}", t);
 394             }
 395         }
 396     }
 397
 398     pub fn push_def_path(&self,
 399                          def_id: DefId,
 400                          output: &mut String) {
 401         let def_path = self.tcx.def_path(def_id);
 402
 403         // some_crate::
 404         if !(self.omit_local_crate_name && def_id.is_local()) {
 405             output.push_str(&self.tcx.crate_name(def_path.krate).as_str());
 406             output.push_str("::");
 407         }
 408
 409         // foo::bar::ItemName::
 410         for part in self.tcx.def_path(def_id).data {
 411             if self.omit_disambiguators {
 412                 write!(output, "{}::", part.data.as_interned_str()).unwrap();
 413             } else {
 414                 write!(output, "{}[{}]::",
 415                        part.data.as_interned_str(),
 416                        part.disambiguator).unwrap();
 417             }
 418         }
 419
 420         // remove final "::"
 421         output.pop();
 422         output.pop();
 423     }
 424
 425     fn push_type_params<I>(&self,
 426                             substs: &Substs<'tcx>,
 427                             projections: I,
 428                             output: &mut String)
 429         where I: Iterator<Item=ty::PolyExistentialProjection<'tcx>>
 430     {
 431         let mut projections = projections.peekable();
 432         if substs.types().next().is_none() && projections.peek().is_none() {
 433             return;
 434         }
 435
 436         output.push('<');
 437
 438         for type_parameter in substs.types() {
 439             self.push_type_name(type_parameter, output);
 440             output.push_str(", ");
 441         }
 442
 443         for projection in projections {
 444             let projection = projection.skip_binder();
 445             let name = &self.tcx.associated_item(projection.item_def_id).name.as_str();
 446             output.push_str(name);
 447             output.push_str("=");
 448             self.push_type_name(projection.ty, output);
 449             output.push_str(", ");
 450         }
 451
 452         output.pop();
 453         output.pop();
 454
 455         output.push('>');
 456     }
 457
 458     pub fn push_instance_as_string(&self,
 459                                    instance: Instance<'tcx>,
 460                                    output: &mut String) {
 461         self.push_def_path(instance.def_id(), output);
 462         self.push_type_params(instance.substs, iter::empty(), output);
 463     }
 464 }