src/librustc_trans/trans_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 asm;
  18 use attributes;
  19 use base;
  20 use consts;
  21 use context::CrateContext;
  22 use common;
  23 use declare;
  24 use llvm;
  25 use monomorphize::Instance;
  26 use rustc::hir;
  27 use rustc::hir::def_id::DefId;
  28 use rustc::traits;
  29 use rustc::ty::{self, Ty, TyCtxt, TypeFoldable};
  30 use rustc::ty::subst::{Subst, Substs};
  31 use syntax::ast::{self, NodeId};
  32 use syntax::attr;
  33 use syntax_pos::Span;
  34 use syntax_pos::symbol::Symbol;
  35 use type_of;
  36 use std::fmt::Write;
  37 use std::iter;
  38
  39 #[derive(PartialEq, Eq, Clone, Copy, Debug, Hash)]
  40 pub enum TransItem<'tcx> {
  41     Fn(Instance<'tcx>),
  42     Static(NodeId),
  43     GlobalAsm(NodeId),
  44 }
  45
  46 /// Describes how a translation item will be instantiated in object files.
  47 #[derive(PartialEq, Eq, Clone, Copy, Debug, Hash)]
  48 pub enum InstantiationMode {
  49     /// There will be exactly one instance of the given TransItem. It will have
  50     /// external linkage so that it can be linked to from other codegen units.
  51     GloballyShared,
  52
  53     /// Each codegen unit containing a reference to the given TransItem will
  54     /// have its own private copy of the function (with internal linkage).
  55     LocalCopy,
  56 }
  57
  58 impl<'a, 'tcx> TransItem<'tcx> {
  59
  60     pub fn define(&self, ccx: &CrateContext<'a, 'tcx>) {
  61         debug!("BEGIN IMPLEMENTING '{} ({})' in cgu {}",
  62                   self.to_string(ccx.tcx()),
  63                   self.to_raw_string(),
  64                   ccx.codegen_unit().name());
  65
  66         match *self {
  67             TransItem::Static(node_id) => {
  68                 let tcx = ccx.tcx();
  69                 let item = tcx.hir.expect_item(node_id);
  70                 if let hir::ItemStatic(_, m, _) = item.node {
  71                     match consts::trans_static(&ccx, m, item.id, &item.attrs) {
  72                         Ok(_) => { /* Cool, everything's alright. */ },
  73                         Err(err) => {
  74                             err.report(tcx, item.span, "static");
  75                         }
  76                     };
  77                 } else {
  78                     span_bug!(item.span, "Mismatch between hir::Item type and TransItem type")
  79                 }
  80             }
  81             TransItem::GlobalAsm(node_id) => {
  82                 let item = ccx.tcx().hir.expect_item(node_id);
  83                 if let hir::ItemGlobalAsm(ref ga) = item.node {
  84                     asm::trans_global_asm(ccx, ga);
  85                 } else {
  86                     span_bug!(item.span, "Mismatch between hir::Item type and TransItem type")
  87                 }
  88             }
  89             TransItem::Fn(instance) => {
  90                 base::trans_instance(&ccx, instance);
  91             }
  92         }
  93
  94         debug!("END IMPLEMENTING '{} ({})' in cgu {}",
  95                self.to_string(ccx.tcx()),
  96                self.to_raw_string(),
  97                ccx.codegen_unit().name());
  98     }
  99
 100     pub fn predefine(&self,
 101                      ccx: &CrateContext<'a, 'tcx>,
 102                      linkage: llvm::Linkage) {
 103         debug!("BEGIN PREDEFINING '{} ({})' in cgu {}",
 104                self.to_string(ccx.tcx()),
 105                self.to_raw_string(),
 106                ccx.codegen_unit().name());
 107
 108         let symbol_name = self.symbol_name(ccx.tcx());
 109
 110         debug!("symbol {}", &symbol_name);
 111
 112         match *self {
 113             TransItem::Static(node_id) => {
 114                 TransItem::predefine_static(ccx, node_id, linkage, &symbol_name);
 115             }
 116             TransItem::Fn(instance) => {
 117                 TransItem::predefine_fn(ccx, instance, linkage, &symbol_name);
 118             }
 119             TransItem::GlobalAsm(..) => {}
 120         }
 121
 122         debug!("END PREDEFINING '{} ({})' in cgu {}",
 123                self.to_string(ccx.tcx()),
 124                self.to_raw_string(),
 125                ccx.codegen_unit().name());
 126     }
 127
 128     fn predefine_static(ccx: &CrateContext<'a, 'tcx>,
 129                         node_id: ast::NodeId,
 130                         linkage: llvm::Linkage,
 131                         symbol_name: &str) {
 132         let def_id = ccx.tcx().hir.local_def_id(node_id);
 133         let instance = Instance::mono(ccx.tcx(), def_id);
 134         let ty = common::instance_ty(ccx.shared(), &instance);
 135         let llty = type_of::type_of(ccx, ty);
 136
 137         let g = declare::define_global(ccx, symbol_name, llty).unwrap_or_else(|| {
 138             ccx.sess().span_fatal(ccx.tcx().hir.span(node_id),
 139                 &format!("symbol `{}` is already defined", symbol_name))
 140         });
 141
 142         unsafe { llvm::LLVMRustSetLinkage(g, linkage) };
 143
 144         ccx.instances().borrow_mut().insert(instance, g);
 145         ccx.statics().borrow_mut().insert(g, def_id);
 146     }
 147
 148     fn predefine_fn(ccx: &CrateContext<'a, 'tcx>,
 149                     instance: Instance<'tcx>,
 150                     linkage: llvm::Linkage,
 151                     symbol_name: &str) {
 152         assert!(!instance.substs.needs_infer() &&
 153                 !instance.substs.has_param_types());
 154
 155         let mono_ty = common::instance_ty(ccx.shared(), &instance);
 156         let attrs = instance.def.attrs(ccx.tcx());
 157         let lldecl = declare::declare_fn(ccx, symbol_name, mono_ty);
 158         unsafe { llvm::LLVMRustSetLinkage(lldecl, linkage) };
 159         base::set_link_section(ccx, lldecl, &attrs);
 160         if linkage == llvm::Linkage::LinkOnceODRLinkage ||
 161             linkage == llvm::Linkage::WeakODRLinkage {
 162             llvm::SetUniqueComdat(ccx.llmod(), lldecl);
 163         }
 164
 165         // If we're compiling the compiler-builtins crate, e.g. the equivalent of
 166         // compiler-rt, then we want to implicitly compile everything with hidden
 167         // visibility as we're going to link this object all over the place but
 168         // don't want the symbols to get exported.
 169         if linkage != llvm::Linkage::InternalLinkage &&
 170            linkage != llvm::Linkage::PrivateLinkage &&
 171            attr::contains_name(ccx.tcx().hir.krate_attrs(), "compiler_builtins") {
 172             unsafe {
 173                 llvm::LLVMRustSetVisibility(lldecl, llvm::Visibility::Hidden);
 174             }
 175         }
 176
 177         debug!("predefine_fn: mono_ty = {:?} instance = {:?}", mono_ty, instance);
 178         if common::is_inline_instance(ccx.tcx(), &instance) {
 179             attributes::inline(lldecl, attributes::InlineAttr::Hint);
 180         }
 181         attributes::from_fn_attrs(ccx, &attrs, lldecl);
 182
 183         ccx.instances().borrow_mut().insert(instance, lldecl);
 184     }
 185
 186     pub fn symbol_name(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> ty::SymbolName {
 187         match *self {
 188             TransItem::Fn(instance) => tcx.symbol_name(instance),
 189             TransItem::Static(node_id) => {
 190                 let def_id = tcx.hir.local_def_id(node_id);
 191                 tcx.symbol_name(Instance::mono(tcx, def_id))
 192             }
 193             TransItem::GlobalAsm(node_id) => {
 194                 let def_id = tcx.hir.local_def_id(node_id);
 195                 ty::SymbolName {
 196                     name: Symbol::intern(&format!("global_asm_{:?}", def_id)).as_str()
 197                 }
 198             }
 199         }
 200     }
 201
 202     pub fn local_span(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Option<Span> {
 203         match *self {
 204             TransItem::Fn(Instance { def, .. }) => {
 205                 tcx.hir.as_local_node_id(def.def_id())
 206             }
 207             TransItem::Static(node_id) |
 208             TransItem::GlobalAsm(node_id) => {
 209                 Some(node_id)
 210             }
 211         }.map(|node_id| tcx.hir.span(node_id))
 212     }
 213
 214     pub fn instantiation_mode(&self,
 215                               tcx: TyCtxt<'a, 'tcx, 'tcx>)
 216                               -> InstantiationMode {
 217         match *self {
 218             TransItem::Fn(ref instance) => {
 219                 if self.explicit_linkage(tcx).is_none() &&
 220                     common::requests_inline(tcx, instance)
 221                 {
 222                     InstantiationMode::LocalCopy
 223                 } else {
 224                     InstantiationMode::GloballyShared
 225                 }
 226             }
 227             TransItem::Static(..) => InstantiationMode::GloballyShared,
 228             TransItem::GlobalAsm(..) => InstantiationMode::GloballyShared,
 229         }
 230     }
 231
 232     pub fn is_generic_fn(&self) -> bool {
 233         match *self {
 234             TransItem::Fn(ref instance) => {
 235                 instance.substs.types().next().is_some()
 236             }
 237             TransItem::Static(..) |
 238             TransItem::GlobalAsm(..) => false,
 239         }
 240     }
 241
 242     pub fn explicit_linkage(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> Option<llvm::Linkage> {
 243         let def_id = match *self {
 244             TransItem::Fn(ref instance) => instance.def_id(),
 245             TransItem::Static(node_id) => tcx.hir.local_def_id(node_id),
 246             TransItem::GlobalAsm(..) => return None,
 247         };
 248
 249         let attributes = tcx.get_attrs(def_id);
 250         if let Some(name) = attr::first_attr_value_str_by_name(&attributes, "linkage") {
 251             if let Some(linkage) = base::llvm_linkage_by_name(&name.as_str()) {
 252                 Some(linkage)
 253             } else {
 254                 let span = tcx.hir.span_if_local(def_id);
 255                 if let Some(span) = span {
 256                     tcx.sess.span_fatal(span, "invalid linkage specified")
 257                 } else {
 258                     tcx.sess.fatal(&format!("invalid linkage specified: {}", name))
 259                 }
 260             }
 261         } else {
 262             None
 263         }
 264     }
 265
 266     /// Returns whether this instance is instantiable - whether it has no unsatisfied
 267     /// predicates.
 268     ///
 269     /// In order to translate an item, all of its predicates must hold, because
 270     /// otherwise the item does not make sense. Type-checking ensures that
 271     /// the predicates of every item that is *used by* a valid item *do*
 272     /// hold, so we can rely on that.
 273     ///
 274     /// However, we translate collector roots (reachable items) and functions
 275     /// in vtables when they are seen, even if they are not used, and so they
 276     /// might not be instantiable. For example, a programmer can define this
 277     /// public function:
 278     ///
 279     ///     pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone {
 280     ///         <&mut () as Clone>::clone(&s);
 281     ///     }
 282     ///
 283     /// That function can't be translated, because the method `<&mut () as Clone>::clone`
 284     /// does not exist. Luckily for us, that function can't ever be used,
 285     /// because that would require for `&'a mut (): Clone` to hold, so we
 286     /// can just not emit any code, or even a linker reference for it.
 287     ///
 288     /// Similarly, if a vtable method has such a signature, and therefore can't
 289     /// be used, we can just not emit it and have a placeholder (a null pointer,
 290     /// which will never be accessed) in its place.
 291     pub fn is_instantiable(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> bool {
 292         debug!("is_instantiable({:?})", self);
 293         let (def_id, substs) = match *self {
 294             TransItem::Fn(ref instance) => (instance.def_id(), instance.substs),
 295             TransItem::Static(node_id) => (tcx.hir.local_def_id(node_id), Substs::empty()),
 296             // global asm never has predicates
 297             TransItem::GlobalAsm(..) => return true
 298         };
 299
 300         let predicates = tcx.predicates_of(def_id).predicates.subst(tcx, substs);
 301         traits::normalize_and_test_predicates(tcx, predicates)
 302     }
 303
 304     pub fn to_string(&self, tcx: TyCtxt<'a, 'tcx, 'tcx>) -> String {
 305         let hir_map = &tcx.hir;
 306
 307         return match *self {
 308             TransItem::Fn(instance) => {
 309                 to_string_internal(tcx, "fn ", instance)
 310             },
 311             TransItem::Static(node_id) => {
 312                 let def_id = hir_map.local_def_id(node_id);
 313                 let instance = Instance::new(def_id, tcx.intern_substs(&[]));
 314                 to_string_internal(tcx, "static ", instance)
 315             },
 316             TransItem::GlobalAsm(..) => {
 317                 "global_asm".to_string()
 318             }
 319         };
 320
 321         fn to_string_internal<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 322                                         prefix: &str,
 323                                         instance: Instance<'tcx>)
 324                                         -> String {
 325             let mut result = String::with_capacity(32);
 326             result.push_str(prefix);
 327             let printer = DefPathBasedNames::new(tcx, false, false);
 328             printer.push_instance_as_string(instance, &mut result);
 329             result
 330         }
 331     }
 332
 333     pub fn to_raw_string(&self) -> String {
 334         match *self {
 335             TransItem::Fn(instance) => {
 336                 format!("Fn({:?}, {})",
 337                          instance.def,
 338                          instance.substs.as_ptr() as usize)
 339             }
 340             TransItem::Static(id) => {
 341                 format!("Static({:?})", id)
 342             }
 343             TransItem::GlobalAsm(id) => {
 344                 format!("GlobalAsm({:?})", id)
 345             }
 346         }
 347     }
 348 }
 349
 350
 351 //=-----------------------------------------------------------------------------
 352 // TransItem String Keys
 353 //=-----------------------------------------------------------------------------
 354
 355 // The code below allows for producing a unique string key for a trans item.
 356 // These keys are used by the handwritten auto-tests, so they need to be
 357 // predictable and human-readable.
 358 //
 359 // Note: A lot of this could looks very similar to what's already in the
 360 //       ppaux module. It would be good to refactor things so we only have one
 361 //       parameterizable implementation for printing types.
 362
 363 /// Same as `unique_type_name()` but with the result pushed onto the given
 364 /// `output` parameter.
 365 pub struct DefPathBasedNames<'a, 'tcx: 'a> {
 366     tcx: TyCtxt<'a, 'tcx, 'tcx>,
 367     omit_disambiguators: bool,
 368     omit_local_crate_name: bool,
 369 }
 370
 371 impl<'a, 'tcx> DefPathBasedNames<'a, 'tcx> {
 372     pub fn new(tcx: TyCtxt<'a, 'tcx, 'tcx>,
 373                omit_disambiguators: bool,
 374                omit_local_crate_name: bool)
 375                -> Self {
 376         DefPathBasedNames {
 377             tcx: tcx,
 378             omit_disambiguators: omit_disambiguators,
 379             omit_local_crate_name: omit_local_crate_name,
 380         }
 381     }
 382
 383     pub fn push_type_name(&self, t: Ty<'tcx>, output: &mut String) {
 384         match t.sty {
 385             ty::TyBool              => output.push_str("bool"),
 386             ty::TyChar              => output.push_str("char"),
 387             ty::TyStr               => output.push_str("str"),
 388             ty::TyNever             => output.push_str("!"),
 389             ty::TyInt(ast::IntTy::Is)    => output.push_str("isize"),
 390             ty::TyInt(ast::IntTy::I8)    => output.push_str("i8"),
 391             ty::TyInt(ast::IntTy::I16)   => output.push_str("i16"),
 392             ty::TyInt(ast::IntTy::I32)   => output.push_str("i32"),
 393             ty::TyInt(ast::IntTy::I64)   => output.push_str("i64"),
 394             ty::TyInt(ast::IntTy::I128)   => output.push_str("i128"),
 395             ty::TyUint(ast::UintTy::Us)   => output.push_str("usize"),
 396             ty::TyUint(ast::UintTy::U8)   => output.push_str("u8"),
 397             ty::TyUint(ast::UintTy::U16)  => output.push_str("u16"),
 398             ty::TyUint(ast::UintTy::U32)  => output.push_str("u32"),
 399             ty::TyUint(ast::UintTy::U64)  => output.push_str("u64"),
 400             ty::TyUint(ast::UintTy::U128)  => output.push_str("u128"),
 401             ty::TyFloat(ast::FloatTy::F32) => output.push_str("f32"),
 402             ty::TyFloat(ast::FloatTy::F64) => output.push_str("f64"),
 403             ty::TyAdt(adt_def, substs) => {
 404                 self.push_def_path(adt_def.did, output);
 405                 self.push_type_params(substs, iter::empty(), output);
 406             },
 407             ty::TyTuple(component_types, _) => {
 408                 output.push('(');
 409                 for &component_type in component_types {
 410                     self.push_type_name(component_type, output);
 411                     output.push_str(", ");
 412                 }
 413                 if !component_types.is_empty() {
 414                     output.pop();
 415                     output.pop();
 416                 }
 417                 output.push(')');
 418             },
 419             ty::TyRawPtr(ty::TypeAndMut { ty: inner_type, mutbl } ) => {
 420                 output.push('*');
 421                 match mutbl {
 422                     hir::MutImmutable => output.push_str("const "),
 423                     hir::MutMutable => output.push_str("mut "),
 424                 }
 425
 426                 self.push_type_name(inner_type, output);
 427             },
 428             ty::TyRef(_, ty::TypeAndMut { ty: inner_type, mutbl }) => {
 429                 output.push('&');
 430                 if mutbl == hir::MutMutable {
 431                     output.push_str("mut ");
 432                 }
 433
 434                 self.push_type_name(inner_type, output);
 435             },
 436             ty::TyArray(inner_type, len) => {
 437                 output.push('[');
 438                 self.push_type_name(inner_type, output);
 439                 write!(output, "; {}", len).unwrap();
 440                 output.push(']');
 441             },
 442             ty::TySlice(inner_type) => {
 443                 output.push('[');
 444                 self.push_type_name(inner_type, output);
 445                 output.push(']');
 446             },
 447             ty::TyDynamic(ref trait_data, ..) => {
 448                 if let Some(principal) = trait_data.principal() {
 449                     self.push_def_path(principal.def_id(), output);
 450                     self.push_type_params(principal.skip_binder().substs,
 451                         trait_data.projection_bounds(),
 452                         output);
 453                 }
 454             },
 455             ty::TyFnDef(..) |
 456             ty::TyFnPtr(_) => {
 457                 let sig = t.fn_sig(self.tcx);
 458                 if sig.unsafety() == hir::Unsafety::Unsafe {
 459                     output.push_str("unsafe ");
 460                 }
 461
 462                 let abi = sig.abi();
 463                 if abi != ::abi::Abi::Rust {
 464                     output.push_str("extern \"");
 465                     output.push_str(abi.name());
 466                     output.push_str("\" ");
 467                 }
 468
 469                 output.push_str("fn(");
 470
 471                 let sig = self.tcx.erase_late_bound_regions_and_normalize(&sig);
 472
 473                 if !sig.inputs().is_empty() {
 474                     for &parameter_type in sig.inputs() {
 475                         self.push_type_name(parameter_type, output);
 476                         output.push_str(", ");
 477                     }
 478                     output.pop();
 479                     output.pop();
 480                 }
 481
 482                 if sig.variadic {
 483                     if !sig.inputs().is_empty() {
 484                         output.push_str(", ...");
 485                     } else {
 486                         output.push_str("...");
 487                     }
 488                 }
 489
 490                 output.push(')');
 491
 492                 if !sig.output().is_nil() {
 493                     output.push_str(" -> ");
 494                     self.push_type_name(sig.output(), output);
 495                 }
 496             },
 497             ty::TyClosure(def_id, ref closure_substs) => {
 498                 self.push_def_path(def_id, output);
 499                 let generics = self.tcx.generics_of(self.tcx.closure_base_def_id(def_id));
 500                 let substs = closure_substs.substs.truncate_to(self.tcx, generics);
 501                 self.push_type_params(substs, iter::empty(), output);
 502             }
 503             ty::TyError |
 504             ty::TyInfer(_) |
 505             ty::TyProjection(..) |
 506             ty::TyParam(_) |
 507             ty::TyAnon(..) => {
 508                 bug!("DefPathBasedNames: Trying to create type name for \
 509                                          unexpected type: {:?}", t);
 510             }
 511         }
 512     }
 513
 514     pub fn push_def_path(&self,
 515                          def_id: DefId,
 516                          output: &mut String) {
 517         let def_path = self.tcx.def_path(def_id);
 518
 519         // some_crate::
 520         if !(self.omit_local_crate_name && def_id.is_local()) {
 521             output.push_str(&self.tcx.crate_name(def_path.krate).as_str());
 522             output.push_str("::");
 523         }
 524
 525         // foo::bar::ItemName::
 526         for part in self.tcx.def_path(def_id).data {
 527             if self.omit_disambiguators {
 528                 write!(output, "{}::", part.data.as_interned_str()).unwrap();
 529             } else {
 530                 write!(output, "{}[{}]::",
 531                        part.data.as_interned_str(),
 532                        part.disambiguator).unwrap();
 533             }
 534         }
 535
 536         // remove final "::"
 537         output.pop();
 538         output.pop();
 539     }
 540
 541     fn push_type_params<I>(&self,
 542                             substs: &Substs<'tcx>,
 543                             projections: I,
 544                             output: &mut String)
 545         where I: Iterator<Item=ty::PolyExistentialProjection<'tcx>>
 546     {
 547         let mut projections = projections.peekable();
 548         if substs.types().next().is_none() && projections.peek().is_none() {
 549             return;
 550         }
 551
 552         output.push('<');
 553
 554         for type_parameter in substs.types() {
 555             self.push_type_name(type_parameter, output);
 556             output.push_str(", ");
 557         }
 558
 559         for projection in projections {
 560             let projection = projection.skip_binder();
 561             let name = &self.tcx.associated_item(projection.item_def_id).name.as_str();
 562             output.push_str(name);
 563             output.push_str("=");
 564             self.push_type_name(projection.ty, output);
 565             output.push_str(", ");
 566         }
 567
 568         output.pop();
 569         output.pop();
 570
 571         output.push('>');
 572     }
 573
 574     pub fn push_instance_as_string(&self,
 575                                    instance: Instance<'tcx>,
 576                                    output: &mut String) {
 577         self.push_def_path(instance.def_id(), output);
 578         self.push_type_params(instance.substs, iter::empty(), output);
 579     }
 580 }