src/librustc_mir/monomorphize/item.rs

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