src/librustc_trans/trans/collector.rs

   1 // Copyright 2014 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 //! Translation Item Collection
  12 //! ===========================
  13 //!
  14 //! This module is responsible for discovering all items that will contribute to
  15 //! to code generation of the crate. The important part here is that it not only
  16 //! needs to find syntax-level items (functions, structs, etc) but also all
  17 //! their monomorphized instantiations. Every non-generic, non-const function
  18 //! maps to one LLVM artifact. Every generic function can produce
  19 //! from zero to N artifacts, depending on the sets of type arguments it
  20 //! is instantiated with.
  21 //! This also applies to generic items from other crates: A generic definition
  22 //! in crate X might produce monomorphizations that are compiled into crate Y.
  23 //! We also have to collect these here.
  24 //!
  25 //! The following kinds of "translation items" are handled here:
  26 //!
  27 //! - Functions
  28 //! - Methods
  29 //! - Closures
  30 //! - Statics
  31 //! - Drop glue
  32 //!
  33 //! The following things also result in LLVM artifacts, but are not collected
  34 //! here, since we instantiate them locally on demand when needed in a given
  35 //! codegen unit:
  36 //!
  37 //! - Constants
  38 //! - Vtables
  39 //! - Object Shims
  40 //!
  41 //!
  42 //! General Algorithm
  43 //! -----------------
  44 //! Let's define some terms first:
  45 //!
  46 //! - A "translation item" is something that results in a function or global in
  47 //!   the LLVM IR of a codegen unit. Translation items do not stand on their
  48 //!   own, they can reference other translation items. For example, if function
  49 //!   `foo()` calls function `bar()` then the translation item for `foo()`
  50 //!   references the translation item for function `bar()`. In general, the
  51 //!   definition for translation item A referencing a translation item B is that
  52 //!   the LLVM artifact produced for A references the LLVM artifact produced
  53 //!   for B.
  54 //!
  55 //! - Translation items and the references between them for a directed graph,
  56 //!   where the translation items are the nodes and references form the edges.
  57 //!   Let's call this graph the "translation item graph".
  58 //!
  59 //! - The translation item graph for a program contains all translation items
  60 //!   that are needed in order to produce the complete LLVM IR of the program.
  61 //!
  62 //! The purpose of the algorithm implemented in this module is to build the
  63 //! translation item graph for the current crate. It runs in two phases:
  64 //!
  65 //! 1. Discover the roots of the graph by traversing the HIR of the crate.
  66 //! 2. Starting from the roots, find neighboring nodes by inspecting the MIR
  67 //!    representation of the item corresponding to a given node, until no more
  68 //!    new nodes are found.
  69 //!
  70 //! ### Discovering roots
  71 //!
  72 //! The roots of the translation item graph correspond to the non-generic
  73 //! syntactic items in the source code. We find them by walking the HIR of the
  74 //! crate, and whenever we hit upon a function, method, or static item, we
  75 //! create a translation item consisting of the items DefId and, since we only
  76 //! consider non-generic items, an empty type-substitution set.
  77 //!
  78 //! ### Finding neighbor nodes
  79 //! Given a translation item node, we can discover neighbors by inspecting its
  80 //! MIR. We walk the MIR and any time we hit upon something that signifies a
  81 //! reference to another translation item, we have found a neighbor. Since the
  82 //! translation item we are currently at is always monomorphic, we also know the
  83 //! concrete type arguments of its neighbors, and so all neighbors again will be
  84 //! monomorphic. The specific forms a reference to a neighboring node can take
  85 //! in MIR are quite diverse. Here is an overview:
  86 //!
  87 //! #### Calling Functions/Methods
  88 //! The most obvious form of one translation item referencing another is a
  89 //! function or method call (represented by a CALL terminator in MIR). But
  90 //! calls are not the only thing that might introduce a reference between two
  91 //! function translation items, and as we will see below, they are just a
  92 //! specialized of the form described next, and consequently will don't get any
  93 //! special treatment in the algorithm.
  94 //!
  95 //! #### Taking a reference to a function or method
  96 //! A function does not need to actually be called in order to be a neighbor of
  97 //! another function. It suffices to just take a reference in order to introduce
  98 //! an edge. Consider the following example:
  99 //!
 100 //! ```rust
 101 //! fn print_val<T: Display>(x: T) {
 102 //!     println!("{}", x);
 103 //! }
 104 //!
 105 //! fn call_fn(f: &Fn(i32), x: i32) {
 106 //!     f(x);
 107 //! }
 108 //!
 109 //! fn main() {
 110 //!     let print_i32 = print_val::<i32>;
 111 //!     call_fn(&print_i32, 0);
 112 //! }
 113 //! ```
 114 //! The MIR of none of these functions will contain an explicit call to
 115 //! `print_val::<i32>`. Nonetheless, in order to translate this program, we need
 116 //! an instance of this function. Thus, whenever we encounter a function or
 117 //! method in operand position, we treat it as a neighbor of the current
 118 //! translation item. Calls are just a special case of that.
 119 //!
 120 //! #### Closures
 121 //! In a way, closures are a simple case. Since every closure object needs to be
 122 //! constructed somewhere, we can reliably discover them by observing
 123 //! `RValue::Aggregate` expressions with `AggregateKind::Closure`. This is also
 124 //! true for closures inlined from other crates.
 125 //!
 126 //! #### Drop glue
 127 //! Drop glue translation items are introduced by MIR drop-statements. The
 128 //! generated translation item will again have drop-glue item neighbors if the
 129 //! type to be dropped contains nested values that also need to be dropped. It
 130 //! might also have a function item neighbor for the explicit `Drop::drop`
 131 //! implementation of its type.
 132 //!
 133 //! #### Unsizing Casts
 134 //! A subtle way of introducing neighbor edges is by casting to a trait object.
 135 //! Since the resulting fat-pointer contains a reference to a vtable, we need to
 136 //! instantiate all object-save methods of the trait, as we need to store
 137 //! pointers to these functions even if they never get called anywhere. This can
 138 //! be seen as a special case of taking a function reference.
 139 //!
 140 //! #### Boxes
 141 //! Since `Box` expression have special compiler support, no explicit calls to
 142 //! `exchange_malloc()` and `exchange_free()` may show up in MIR, even if the
 143 //! compiler will generate them. We have to observe `Rvalue::Box` expressions
 144 //! and Box-typed drop-statements for that purpose.
 145 //!
 146 //!
 147 //! Interaction with Cross-Crate Inlining
 148 //! -------------------------------------
 149 //! The binary of a crate will not only contain machine code for the items
 150 //! defined in the source code of that crate. It will also contain monomorphic
 151 //! instantiations of any extern generic functions and of functions marked with
 152 //! #[inline].
 153 //! The collection algorithm handles this more or less transparently. If it is
 154 //! about to create a translation item for something with an external `DefId`,
 155 //! it will take a look if the MIR for that item is available, and if so just
 156 //! proceed normally. If the MIR is not available, it assumes that that item is
 157 //! just linked to and no node is created; which is exactly what we want, since
 158 //! no machine code should be generated in the current crate for such an item.
 159 //!
 160 //! Eager and Lazy Collection Mode
 161 //! ------------------------------
 162 //! Translation item collection can be performed in one of two modes:
 163 //!
 164 //! - Lazy mode means that items will only be instantiated when actually
 165 //!   referenced. The goal is to produce the least amount of machine code
 166 //!   possible.
 167 //!
 168 //! - Eager mode is meant to be used in conjunction with incremental compilation
 169 //!   where a stable set of translation items is more important than a minimal
 170 //!   one. Thus, eager mode will instantiate drop-glue for every drop-able type
 171 //!   in the crate, even of no drop call for that type exists (yet). It will
 172 //!   also instantiate default implementations of trait methods, something that
 173 //!   otherwise is only done on demand.
 174 //!
 175 //!
 176 //! Open Issues
 177 //! -----------
 178 //! Some things are not yet fully implemented in the current version of this
 179 //! module.
 180 //!
 181 //! ### Initializers of Constants and Statics
 182 //! Since no MIR is constructed yet for initializer expressions of constants and
 183 //! statics we cannot inspect these properly.
 184 //!
 185 //! ### Const Fns
 186 //! Ideally, no translation item should be generated for const fns unless there
 187 //! is a call to them that cannot be evaluated at compile time. At the moment
 188 //! this is not implemented however: a translation item will be produced
 189 //! regardless of whether it is actually needed or not.
 190
 191 use rustc_front::hir;
 192 use rustc_front::intravisit as hir_visit;
 193
 194 use rustc::front::map as hir_map;
 195 use rustc::middle::def_id::DefId;
 196 use rustc::middle::lang_items::{ExchangeFreeFnLangItem, ExchangeMallocFnLangItem};
 197 use rustc::middle::{ty, traits};
 198 use rustc::middle::subst::{self, Substs, Subst};
 199 use rustc::middle::ty::adjustment::CustomCoerceUnsized;
 200 use rustc::middle::ty::fold::TypeFoldable;
 201 use rustc::mir::repr as mir;
 202 use rustc::mir::visit as mir_visit;
 203 use rustc::mir::visit::Visitor as MirVisitor;
 204
 205 use syntax::ast::{self, NodeId};
 206 use syntax::codemap::DUMMY_SP;
 207 use syntax::errors;
 208 use syntax::parse::token;
 209
 210 use trans::base::custom_coerce_unsize_info;
 211 use trans::context::CrateContext;
 212 use trans::common::{fulfill_obligation, normalize_and_test_predicates,
 213                     type_is_sized};
 214 use trans::glue;
 215 use trans::meth;
 216 use trans::monomorphize;
 217 use util::nodemap::{FnvHashSet, FnvHashMap, DefIdMap};
 218
 219 use std::hash::{Hash, Hasher};
 220 use std::rc::Rc;
 221
 222 #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
 223 pub enum TransItemCollectionMode {
 224     Eager,
 225     Lazy
 226 }
 227
 228 #[derive(Eq, Clone, Copy, Debug)]
 229 pub enum TransItem<'tcx> {
 230     DropGlue(ty::Ty<'tcx>),
 231     Fn {
 232         def_id: DefId,
 233         substs: &'tcx Substs<'tcx>
 234     },
 235     Static(NodeId)
 236 }
 237
 238 impl<'tcx> Hash for TransItem<'tcx> {
 239     fn hash<H: Hasher>(&self, s: &mut H) {
 240         match *self {
 241             TransItem::DropGlue(t) => {
 242                 0u8.hash(s);
 243                 t.hash(s);
 244             },
 245             TransItem::Fn { def_id, substs } => {
 246                 1u8.hash(s);
 247                 def_id.hash(s);
 248                 (substs as *const Substs<'tcx> as usize).hash(s);
 249             }
 250             TransItem::Static(node_id) => {
 251                 3u8.hash(s);
 252                 node_id.hash(s);
 253             }
 254         };
 255     }
 256 }
 257
 258 impl<'tcx> PartialEq for TransItem<'tcx> {
 259     fn eq(&self, other: &Self) -> bool {
 260         match (*self, *other) {
 261             (TransItem::DropGlue(t1), TransItem::DropGlue(t2)) => t1 == t2,
 262             (TransItem::Fn { def_id: def_id1, substs: substs1 },
 263              TransItem::Fn { def_id: def_id2, substs: substs2 }) => {
 264                 def_id1 == def_id2 && substs1 == substs2
 265             },
 266             (TransItem::Static(node_id1), TransItem::Static(node_id2)) => {
 267                 node_id1 == node_id2
 268             },
 269             _ => false
 270         }
 271     }
 272 }
 273
 274 pub fn collect_crate_translation_items<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 275                                                  mode: TransItemCollectionMode)
 276                                                  -> FnvHashSet<TransItem<'tcx>> {
 277     // We are not tracking dependencies of this pass as it has to be re-executed
 278     // every time no matter what.
 279     ccx.tcx().dep_graph.with_ignore(|| {
 280         let roots = collect_roots(ccx, mode);
 281
 282         debug!("Building translation item graph, beginning at roots");
 283         let mut visited = FnvHashSet();
 284         let mut recursion_depths = DefIdMap();
 285         let mut mir_cache = DefIdMap();
 286
 287         for root in roots {
 288             collect_items_rec(ccx,
 289                               root,
 290                               &mut visited,
 291                               &mut recursion_depths,
 292                               &mut mir_cache);
 293         }
 294
 295         visited
 296     })
 297 }
 298
 299 // Find all non-generic items by walking the HIR. These items serve as roots to
 300 // start monomorphizing from.
 301 fn collect_roots<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 302                            mode: TransItemCollectionMode)
 303                            -> Vec<TransItem<'tcx>> {
 304     debug!("Collecting roots");
 305     let mut roots = Vec::new();
 306
 307     {
 308         let mut visitor = RootCollector {
 309             ccx: ccx,
 310             mode: mode,
 311             output: &mut roots,
 312             enclosing_item: None,
 313             trans_empty_substs: ccx.tcx().mk_substs(Substs::trans_empty()),
 314         };
 315
 316         ccx.tcx().map.krate().visit_all_items(&mut visitor);
 317     }
 318
 319     roots
 320 }
 321
 322 #[derive(Clone)]
 323 enum CachedMir<'mir, 'tcx: 'mir> {
 324     Ref(&'mir mir::Mir<'tcx>),
 325     Owned(Rc<mir::Mir<'tcx>>)
 326 }
 327
 328 impl<'mir, 'tcx: 'mir> CachedMir<'mir, 'tcx> {
 329     fn get_ref<'a>(&'a self) -> &'a mir::Mir<'tcx> {
 330         match *self {
 331             CachedMir::Ref(r) => r,
 332             CachedMir::Owned(ref rc) => &**rc,
 333         }
 334     }
 335 }
 336
 337 // Collect all monomorphized translation items reachable from `starting_point`
 338 fn collect_items_rec<'a, 'tcx: 'a>(ccx: &CrateContext<'a, 'tcx>,
 339                                    starting_point: TransItem<'tcx>,
 340                                    visited: &mut FnvHashSet<TransItem<'tcx>>,
 341                                    recursion_depths: &mut DefIdMap<usize>,
 342                                    mir_cache: &mut DefIdMap<CachedMir<'a, 'tcx>>) {
 343     if !visited.insert(starting_point.clone()) {
 344         // We've been here already, no need to search again.
 345         return;
 346     }
 347     debug!("BEGIN collect_items_rec({})", starting_point.to_string(ccx));
 348
 349     let mut neighbors = Vec::new();
 350     let recursion_depth_reset;
 351
 352     match starting_point {
 353         TransItem::DropGlue(_) |
 354         TransItem::Static(_) => {
 355             recursion_depth_reset = None;
 356         }
 357         TransItem::Fn {
 358             def_id,
 359             substs: ref param_substs
 360         } => {
 361             // Keep track of the monomorphization recursion depth
 362             recursion_depth_reset = Some(check_recursion_limit(ccx,
 363                                                                def_id,
 364                                                                recursion_depths));
 365
 366             // Scan the MIR in order to find function calls, closures, and
 367             // drop-glue
 368             let mir = load_mir(ccx, def_id, mir_cache);
 369
 370             let mut visitor = MirNeighborCollector {
 371                 ccx: ccx,
 372                 mir: mir.get_ref(),
 373                 output: &mut neighbors,
 374                 param_substs: param_substs
 375             };
 376
 377             visitor.visit_mir(mir.get_ref());
 378         }
 379     }
 380
 381     for neighbour in neighbors {
 382         collect_items_rec(ccx, neighbour, visited, recursion_depths, mir_cache);
 383     }
 384
 385     if let Some((def_id, depth)) = recursion_depth_reset {
 386         recursion_depths.insert(def_id, depth);
 387     }
 388
 389     debug!("END collect_items_rec({})", starting_point.to_string(ccx));
 390 }
 391
 392 fn load_mir<'a, 'tcx: 'a>(ccx: &CrateContext<'a, 'tcx>,
 393                           def_id: DefId,
 394                           mir_cache: &mut DefIdMap<CachedMir<'a, 'tcx>>)
 395                           -> CachedMir<'a, 'tcx> {
 396     let mir_not_found_error_message = || {
 397         format!("Could not find MIR for function: {}",
 398                 ccx.tcx().item_path_str(def_id))
 399     };
 400
 401     if def_id.is_local() {
 402         let node_id = ccx.tcx().map.as_local_node_id(def_id).unwrap();
 403         let mir_opt = ccx.mir_map().get(&node_id);
 404         let mir = errors::expect(ccx.sess().diagnostic(),
 405                              mir_opt,
 406                              mir_not_found_error_message);
 407         CachedMir::Ref(mir)
 408     } else {
 409         if let Some(mir) = mir_cache.get(&def_id) {
 410             return mir.clone();
 411         }
 412
 413         let mir_opt = ccx.sess().cstore.maybe_get_item_mir(ccx.tcx(), def_id);
 414         let mir = errors::expect(ccx.sess().diagnostic(),
 415                                  mir_opt,
 416                                  mir_not_found_error_message);
 417         let cached = CachedMir::Owned(Rc::new(mir));
 418         mir_cache.insert(def_id, cached.clone());
 419         cached
 420     }
 421 }
 422
 423 fn check_recursion_limit<'a, 'tcx: 'a>(ccx: &CrateContext<'a, 'tcx>,
 424                                        def_id: DefId,
 425                                        recursion_depths: &mut DefIdMap<usize>)
 426                                        -> (DefId, usize) {
 427     let recursion_depth = recursion_depths.get(&def_id)
 428                                           .map(|x| *x)
 429                                           .unwrap_or(0);
 430     debug!(" => recursion depth={}", recursion_depth);
 431
 432     // Code that needs to instantiate the same function recursively
 433     // more than the recursion limit is assumed to be causing an
 434     // infinite expansion.
 435     if recursion_depth > ccx.sess().recursion_limit.get() {
 436         if let Some(node_id) = ccx.tcx().map.as_local_node_id(def_id) {
 437             ccx.sess().span_fatal(ccx.tcx().map.span(node_id),
 438                 "reached the recursion limit during monomorphization");
 439         } else {
 440             let error = format!("reached the recursion limit during \
 441                                 monomorphization of '{}'",
 442                                 ccx.tcx().item_path_str(def_id));
 443             ccx.sess().fatal(&error[..]);
 444         }
 445     }
 446
 447     recursion_depths.insert(def_id, recursion_depth + 1);
 448
 449     (def_id, recursion_depth)
 450 }
 451
 452 struct MirNeighborCollector<'a, 'tcx: 'a> {
 453     ccx: &'a CrateContext<'a, 'tcx>,
 454     mir: &'a mir::Mir<'tcx>,
 455     output: &'a mut Vec<TransItem<'tcx>>,
 456     param_substs: &'tcx Substs<'tcx>
 457 }
 458
 459 impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
 460
 461     fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>) {
 462         debug!("visiting rvalue {:?}", *rvalue);
 463
 464         match *rvalue {
 465             mir::Rvalue::Aggregate(mir::AggregateKind::Closure(def_id,
 466                                                                ref substs), _) => {
 467                 assert!(can_have_local_instance(self.ccx, def_id));
 468                 let trans_item = create_fn_trans_item(self.ccx,
 469                                                       def_id,
 470                                                       substs.func_substs,
 471                                                       self.param_substs);
 472                 self.output.push(trans_item);
 473             }
 474             // When doing an cast from a regular pointer to a fat pointer, we
 475             // have to instantiate all methods of the trait being cast to, so we
 476             // can build the appropriate vtable.
 477             mir::Rvalue::Cast(mir::CastKind::Unsize, ref operand, target_ty) => {
 478                 let target_ty = monomorphize::apply_param_substs(self.ccx.tcx(),
 479                                                                  self.param_substs,
 480                                                                  &target_ty);
 481                 let source_ty = self.mir.operand_ty(self.ccx.tcx(), operand);
 482                 let source_ty = monomorphize::apply_param_substs(self.ccx.tcx(),
 483                                                                  self.param_substs,
 484                                                                  &source_ty);
 485                 let (source_ty, target_ty) = find_vtable_types_for_unsizing(self.ccx,
 486                                                                             source_ty,
 487                                                                             target_ty);
 488                 // This could also be a different Unsize instruction, like
 489                 // from a fixed sized array to a slice. But we are only
 490                 // interested in things that produce a vtable.
 491                 if target_ty.is_trait() && !source_ty.is_trait() {
 492                     create_trans_items_for_vtable_methods(self.ccx,
 493                                                           target_ty,
 494                                                           source_ty,
 495                                                           self.output);
 496                 }
 497             }
 498             mir::Rvalue::Box(_) => {
 499                 let exchange_malloc_fn_def_id =
 500                     self.ccx
 501                         .tcx()
 502                         .lang_items
 503                         .require(ExchangeMallocFnLangItem)
 504                         .expect("Could not find ExchangeMallocFnLangItem");
 505
 506                 assert!(can_have_local_instance(self.ccx, exchange_malloc_fn_def_id));
 507                 let exchange_malloc_fn_trans_item =
 508                     create_fn_trans_item(self.ccx,
 509                                          exchange_malloc_fn_def_id,
 510                                          &Substs::trans_empty(),
 511                                          self.param_substs);
 512
 513                 self.output.push(exchange_malloc_fn_trans_item);
 514             }
 515             _ => { /* not interesting */ }
 516         }
 517
 518         self.super_rvalue(rvalue);
 519     }
 520
 521     fn visit_lvalue(&mut self,
 522                     lvalue: &mir::Lvalue<'tcx>,
 523                     context: mir_visit::LvalueContext) {
 524         debug!("visiting lvalue {:?}", *lvalue);
 525
 526         if let mir_visit::LvalueContext::Drop = context {
 527             let ty = self.mir.lvalue_ty(self.ccx.tcx(), lvalue)
 528                              .to_ty(self.ccx.tcx());
 529
 530             let ty = monomorphize::apply_param_substs(self.ccx.tcx(),
 531                                                       self.param_substs,
 532                                                       &ty);
 533             let ty = self.ccx.tcx().erase_regions(&ty);
 534
 535             create_drop_glue_trans_items(self.ccx,
 536                                          ty,
 537                                          self.param_substs,
 538                                          &mut self.output);
 539         }
 540
 541         self.super_lvalue(lvalue, context);
 542     }
 543
 544     fn visit_operand(&mut self, operand: &mir::Operand<'tcx>) {
 545         debug!("visiting operand {:?}", *operand);
 546
 547         let callee = match *operand {
 548             mir::Operand::Constant(mir::Constant {
 549                 literal: mir::Literal::Item {
 550                     def_id,
 551                     kind,
 552                     substs
 553                 },
 554                 ..
 555             }) if is_function_or_method(kind) => Some((def_id, substs)),
 556             _ => None
 557         };
 558
 559         if let Some((callee_def_id, callee_substs)) = callee {
 560             debug!(" => operand is callable");
 561
 562             // `callee_def_id` might refer to a trait method instead of a
 563             // concrete implementation, so we have to find the actual
 564             // implementation. For example, the call might look like
 565             //
 566             // std::cmp::partial_cmp(0i32, 1i32)
 567             //
 568             // Calling do_static_dispatch() here will map the def_id of
 569             // `std::cmp::partial_cmp` to the def_id of `i32::partial_cmp<i32>`
 570             let dispatched = do_static_dispatch(self.ccx,
 571                                                 callee_def_id,
 572                                                 callee_substs,
 573                                                 self.param_substs);
 574
 575             if let Some((callee_def_id, callee_substs)) = dispatched {
 576                 // if we have a concrete impl (which we might not have
 577                 // in the case of something compiler generated like an
 578                 // object shim or a closure that is handled differently),
 579                 // we check if the callee is something that will actually
 580                 // result in a translation item ...
 581                 if can_result_in_trans_item(self.ccx, callee_def_id) {
 582                     // ... and create one if it does.
 583                     let trans_item = create_fn_trans_item(self.ccx,
 584                                                           callee_def_id,
 585                                                           callee_substs,
 586                                                           self.param_substs);
 587                     self.output.push(trans_item);
 588                 }
 589             }
 590         }
 591
 592         self.super_operand(operand);
 593
 594         fn is_function_or_method(item_kind: mir::ItemKind) -> bool {
 595             match item_kind {
 596                 mir::ItemKind::Constant => false,
 597                 mir::ItemKind::Function |
 598                 mir::ItemKind::Method   => true
 599             }
 600         }
 601
 602         fn can_result_in_trans_item<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 603                                               def_id: DefId)
 604                                               -> bool {
 605             if !match ccx.tcx().lookup_item_type(def_id).ty.sty {
 606                 ty::TyBareFn(Some(def_id), _) => {
 607                     // Some constructors also have type TyBareFn but they are
 608                     // always instantiated inline and don't result in
 609                     // translation item.
 610                     match ccx.tcx().map.get_if_local(def_id) {
 611                         Some(hir_map::NodeVariant(_))    |
 612                         Some(hir_map::NodeStructCtor(_)) => false,
 613                         Some(_) => true,
 614                         None => {
 615                             ccx.sess().cstore.variant_kind(def_id).is_none()
 616                         }
 617                     }
 618                 }
 619                 ty::TyClosure(..) => true,
 620                 _ => false
 621             } {
 622                 return false;
 623             }
 624
 625             can_have_local_instance(ccx, def_id)
 626         }
 627     }
 628 }
 629
 630 fn can_have_local_instance<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 631                                      def_id: DefId)
 632                                      -> bool {
 633     // Take a look if we have the definition available. If not, we
 634     // will not emit code for this item in the local crate, and thus
 635     // don't create a translation item for it.
 636     def_id.is_local() || ccx.sess().cstore.is_item_mir_available(def_id)
 637 }
 638
 639 fn create_drop_glue_trans_items<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 640                                           mono_ty: ty::Ty<'tcx>,
 641                                           param_substs: &'tcx Substs<'tcx>,
 642                                           output: &mut Vec<TransItem<'tcx>>)
 643 {
 644     visit_types_of_owned_components(ccx,
 645                                     mono_ty,
 646                                     &mut FnvHashSet(),
 647                                     &mut |ty| {
 648         debug!("create_drop_glue_trans_items: {}", type_to_string(ccx, ty));
 649         // Add a translation item for the drop glue, if even this type does not
 650         // need to be dropped (in which case it has been mapped to i8)
 651         output.push(TransItem::DropGlue(ty));
 652
 653         if glue::type_needs_drop(ccx.tcx(), ty) {
 654
 655             // Make sure the exchange_free_fn() lang-item gets translated if
 656             // there is a boxed value.
 657             if let ty::TyBox(_) = ty.sty {
 658
 659                 let exchange_free_fn_def_id = ccx.tcx()
 660                                                  .lang_items
 661                                                  .require(ExchangeFreeFnLangItem)
 662                                                  .expect("Could not find ExchangeFreeFnLangItem");
 663
 664                 assert!(can_have_local_instance(ccx, exchange_free_fn_def_id));
 665                 let exchange_free_fn_trans_item =
 666                     create_fn_trans_item(ccx,
 667                                          exchange_free_fn_def_id,
 668                                          &Substs::trans_empty(),
 669                                          param_substs);
 670
 671                 output.push(exchange_free_fn_trans_item);
 672             }
 673
 674             // If the type implements Drop, also add a translation item for the
 675             // monomorphized Drop::drop() implementation.
 676             let destructor_did = match ty.sty {
 677                 ty::TyStruct(def, _) |
 678                 ty::TyEnum(def, _)   => def.destructor(),
 679                 _ => None
 680             };
 681
 682             if let Some(destructor_did) = destructor_did {
 683                 use rustc::middle::ty::ToPolyTraitRef;
 684
 685                 let drop_trait_def_id = ccx.tcx()
 686                                            .lang_items
 687                                            .drop_trait()
 688                                            .unwrap();
 689
 690                 let self_type_substs = ccx.tcx().mk_substs(
 691                     Substs::trans_empty().with_self_ty(ty));
 692
 693                 let trait_ref = ty::TraitRef {
 694                     def_id: drop_trait_def_id,
 695                     substs: self_type_substs,
 696                 }.to_poly_trait_ref();
 697
 698                 let substs = match fulfill_obligation(ccx, DUMMY_SP, trait_ref) {
 699                     traits::VtableImpl(data) => data.substs,
 700                     _ => unreachable!()
 701                 };
 702
 703                 if can_have_local_instance(ccx, destructor_did) {
 704                     let trans_item = create_fn_trans_item(ccx,
 705                                                           destructor_did,
 706                                                           ccx.tcx().mk_substs(substs),
 707                                                           param_substs);
 708                     output.push(trans_item);
 709                 }
 710             }
 711
 712             true
 713         } else {
 714             false
 715         }
 716     });
 717
 718     fn visit_types_of_owned_components<'a, 'tcx, F>(ccx: &CrateContext<'a, 'tcx>,
 719                                                     ty: ty::Ty<'tcx>,
 720                                                     visited: &mut FnvHashSet<ty::Ty<'tcx>>,
 721                                                     mut f: &mut F)
 722         where F: FnMut(ty::Ty<'tcx>) -> bool
 723     {
 724         let ty = glue::get_drop_glue_type(ccx, ty);
 725
 726         if !visited.insert(ty) {
 727             return;
 728         }
 729
 730         if !f(ty) {
 731             // Don't recurse further
 732             return;
 733         }
 734
 735         match ty.sty {
 736             ty::TyBool       |
 737             ty::TyChar       |
 738             ty::TyInt(_)     |
 739             ty::TyUint(_)    |
 740             ty::TyStr        |
 741             ty::TyFloat(_)   |
 742             ty::TyRawPtr(_)  |
 743             ty::TyRef(..)    |
 744             ty::TyBareFn(..) |
 745             ty::TySlice(_)   |
 746             ty::TyTrait(_)   => {
 747                 /* nothing to do */
 748             }
 749             ty::TyStruct(ref adt_def, substs) |
 750             ty::TyEnum(ref adt_def, substs) => {
 751                 for field in adt_def.all_fields() {
 752                     let field_type = monomorphize::apply_param_substs(ccx.tcx(),
 753                                                                       substs,
 754                                                                       &field.unsubst_ty());
 755                     visit_types_of_owned_components(ccx, field_type, visited, f);
 756                 }
 757             }
 758             ty::TyClosure(_, ref substs) => {
 759                 for upvar_ty in &substs.upvar_tys {
 760                     visit_types_of_owned_components(ccx, upvar_ty, visited, f);
 761                 }
 762             }
 763             ty::TyBox(inner_type)      |
 764             ty::TyArray(inner_type, _) => {
 765                 visit_types_of_owned_components(ccx, inner_type, visited, f);
 766             }
 767             ty::TyTuple(ref args) => {
 768                 for arg in args {
 769                     visit_types_of_owned_components(ccx, arg, visited, f);
 770                 }
 771             }
 772             ty::TyProjection(_) |
 773             ty::TyParam(_)      |
 774             ty::TyInfer(_)      |
 775             ty::TyError         => {
 776                 ccx.sess().bug("encountered unexpected type");
 777             }
 778         }
 779     }
 780 }
 781
 782 fn do_static_dispatch<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 783                                 fn_def_id: DefId,
 784                                 fn_substs: &'tcx Substs<'tcx>,
 785                                 param_substs: &'tcx Substs<'tcx>)
 786                                 -> Option<(DefId, &'tcx Substs<'tcx>)> {
 787     debug!("do_static_dispatch(fn_def_id={}, fn_substs={:?}, param_substs={:?})",
 788            def_id_to_string(ccx, fn_def_id, None),
 789            fn_substs,
 790            param_substs);
 791
 792     let is_trait_method = ccx.tcx().trait_of_item(fn_def_id).is_some();
 793
 794     if is_trait_method {
 795         match ccx.tcx().impl_or_trait_item(fn_def_id) {
 796             ty::MethodTraitItem(ref method) => {
 797                 match method.container {
 798                     ty::TraitContainer(trait_def_id) => {
 799                         debug!(" => trait method, attempting to find impl");
 800                         do_static_trait_method_dispatch(ccx,
 801                                                         method,
 802                                                         trait_def_id,
 803                                                         fn_substs,
 804                                                         param_substs)
 805                     }
 806                     ty::ImplContainer(_) => {
 807                         // This is already a concrete implementation
 808                         debug!(" => impl method");
 809                         Some((fn_def_id, fn_substs))
 810                     }
 811                 }
 812             }
 813             _ => unreachable!()
 814         }
 815     } else {
 816         debug!(" => regular function");
 817         // The function is not part of an impl or trait, no dispatching
 818         // to be done
 819         Some((fn_def_id, fn_substs))
 820     }
 821 }
 822
 823 // Given a trait-method and substitution information, find out the actual
 824 // implementation of the trait method.
 825 fn do_static_trait_method_dispatch<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 826                                              trait_method: &ty::Method,
 827                                              trait_id: DefId,
 828                                              callee_substs: &'tcx Substs<'tcx>,
 829                                              param_substs: &'tcx Substs<'tcx>)
 830                                              -> Option<(DefId, &'tcx Substs<'tcx>)> {
 831     let tcx = ccx.tcx();
 832     debug!("do_static_trait_method_dispatch(trait_method={}, \
 833                                             trait_id={}, \
 834                                             callee_substs={:?}, \
 835                                             param_substs={:?}",
 836            def_id_to_string(ccx, trait_method.def_id, None),
 837            def_id_to_string(ccx, trait_id, None),
 838            callee_substs,
 839            param_substs);
 840
 841     let rcvr_substs = monomorphize::apply_param_substs(tcx,
 842                                                        param_substs,
 843                                                        callee_substs);
 844
 845     let trait_ref = ty::Binder(rcvr_substs.to_trait_ref(tcx, trait_id));
 846     let vtbl = fulfill_obligation(ccx, DUMMY_SP, trait_ref);
 847
 848     // Now that we know which impl is being used, we can dispatch to
 849     // the actual function:
 850     match vtbl {
 851         traits::VtableImpl(traits::VtableImplData {
 852             impl_def_id: impl_did,
 853             substs: impl_substs,
 854             nested: _ }) =>
 855         {
 856             let callee_substs = impl_substs.with_method_from(&rcvr_substs);
 857             let impl_method = tcx.get_impl_method(impl_did,
 858                                                   callee_substs,
 859                                                   trait_method.name);
 860             Some((impl_method.method.def_id, tcx.mk_substs(impl_method.substs)))
 861         }
 862         // If we have a closure or a function pointer, we will also encounter
 863         // the concrete closure/function somewhere else (during closure or fn
 864         // pointer construction). That's where we track those things.
 865         traits::VtableClosure(..) |
 866         traits::VtableFnPointer(..) |
 867         traits::VtableObject(..) => {
 868             None
 869         }
 870         _ => {
 871             tcx.sess.bug(&format!("static call to invalid vtable: {:?}", vtbl))
 872         }
 873     }
 874 }
 875
 876 /// For given pair of source and target type that occur in an unsizing coercion,
 877 /// this function finds the pair of types that determines the vtable linking
 878 /// them.
 879 ///
 880 /// For example, the source type might be `&SomeStruct` and the target type\
 881 /// might be `&SomeTrait` in a cast like:
 882 ///
 883 /// let src: &SomeStruct = ...;
 884 /// let target = src as &SomeTrait;
 885 ///
 886 /// Then the output of this function would be (SomeStruct, SomeTrait) since for
 887 /// constructing the `target` fat-pointer we need the vtable for that pair.
 888 ///
 889 /// Things can get more complicated though because there's also the case where
 890 /// the unsized type occurs as a field:
 891 ///
 892 /// ```rust
 893 /// struct ComplexStruct<T: ?Sized> {
 894 ///    a: u32,
 895 ///    b: f64,
 896 ///    c: T
 897 /// }
 898 /// ```
 899 ///
 900 /// In this case, if `T` is sized, `&ComplexStruct<T>` is a thin pointer. If `T`
 901 /// is unsized, `&SomeStruct` is a fat pointer, and the vtable it points to is
 902 /// for the pair of `T` (which is a trait) and the concrete type that `T` was
 903 /// originally coerced from:
 904 ///
 905 /// let src: &ComplexStruct<SomeStruct> = ...;
 906 /// let target = src as &ComplexStruct<SomeTrait>;
 907 ///
 908 /// Again, we want this `find_vtable_types_for_unsizing()` to provide the pair
 909 /// `(SomeStruct, SomeTrait)`.
 910 ///
 911 /// Finally, there is also the case of custom unsizing coercions, e.g. for
 912 /// smart pointers such as `Rc` and `Arc`.
 913 fn find_vtable_types_for_unsizing<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 914                                             source_ty: ty::Ty<'tcx>,
 915                                             target_ty: ty::Ty<'tcx>)
 916                                             -> (ty::Ty<'tcx>, ty::Ty<'tcx>) {
 917     match (&source_ty.sty, &target_ty.sty) {
 918         (&ty::TyBox(a), &ty::TyBox(b)) |
 919         (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
 920          &ty::TyRef(_, ty::TypeAndMut { ty: b, .. })) |
 921         (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
 922          &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) |
 923         (&ty::TyRawPtr(ty::TypeAndMut { ty: a, .. }),
 924          &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) => {
 925             let (inner_source, inner_target) = (a, b);
 926
 927             if !type_is_sized(ccx.tcx(), inner_source) {
 928                 (inner_source, inner_target)
 929             } else {
 930                 ccx.tcx().struct_lockstep_tails(inner_source, inner_target)
 931             }
 932         }
 933
 934         (&ty::TyStruct(source_adt_def, source_substs),
 935          &ty::TyStruct(target_adt_def, target_substs)) => {
 936             assert_eq!(source_adt_def, target_adt_def);
 937
 938             let kind = custom_coerce_unsize_info(ccx, source_ty, target_ty);
 939
 940             let coerce_index = match kind {
 941                 CustomCoerceUnsized::Struct(i) => i
 942             };
 943
 944             let source_fields = &source_adt_def.struct_variant().fields;
 945             let target_fields = &target_adt_def.struct_variant().fields;
 946
 947             assert!(coerce_index < source_fields.len() &&
 948                     source_fields.len() == target_fields.len());
 949
 950             find_vtable_types_for_unsizing(ccx,
 951                                            source_fields[coerce_index].ty(ccx.tcx(),
 952                                                                           source_substs),
 953                                            target_fields[coerce_index].ty(ccx.tcx(),
 954                                                                           target_substs))
 955         }
 956         _ => ccx.sess()
 957                 .bug(&format!("find_vtable_types_for_unsizing: invalid coercion {:?} -> {:?}",
 958                                source_ty,
 959                                target_ty))
 960     }
 961 }
 962
 963 fn create_fn_trans_item<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 964                                   def_id: DefId,
 965                                   fn_substs: &Substs<'tcx>,
 966                                   param_substs: &Substs<'tcx>)
 967                                   -> TransItem<'tcx>
 968 {
 969     debug!("create_fn_trans_item(def_id={}, fn_substs={:?}, param_substs={:?})",
 970             def_id_to_string(ccx, def_id, None),
 971             fn_substs,
 972             param_substs);
 973
 974     // We only get here, if fn_def_id either designates a local item or
 975     // an inlineable external item. Non-inlineable external items are
 976     // ignored because we don't want to generate any code for them.
 977     let concrete_substs = monomorphize::apply_param_substs(ccx.tcx(),
 978                                                            param_substs,
 979                                                            fn_substs);
 980     let concrete_substs = ccx.tcx().erase_regions(&concrete_substs);
 981
 982     let trans_item = TransItem::Fn {
 983         def_id: def_id,
 984         substs: ccx.tcx().mk_substs(concrete_substs),
 985     };
 986
 987     return trans_item;
 988 }
 989
 990 /// Creates a `TransItem` for each method that is referenced by the vtable for
 991 /// the given trait/impl pair.
 992 fn create_trans_items_for_vtable_methods<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
 993                                                    trait_ty: ty::Ty<'tcx>,
 994                                                    impl_ty: ty::Ty<'tcx>,
 995                                                    output: &mut Vec<TransItem<'tcx>>) {
 996     assert!(!trait_ty.needs_subst() && !impl_ty.needs_subst());
 997
 998     if let ty::TyTrait(ref trait_ty) = trait_ty.sty {
 999         let poly_trait_ref = trait_ty.principal_trait_ref_with_self_ty(ccx.tcx(),
1000                                                                        impl_ty);
1001
1002         // Walk all methods of the trait, including those of its supertraits
1003         for trait_ref in traits::supertraits(ccx.tcx(), poly_trait_ref) {
1004             let vtable = fulfill_obligation(ccx, DUMMY_SP, trait_ref);
1005             match vtable {
1006                 traits::VtableImpl(
1007                     traits::VtableImplData {
1008                         impl_def_id,
1009                         substs,
1010                         nested: _ }) => {
1011                     let items = meth::get_vtable_methods(ccx, impl_def_id, substs)
1012                         .into_iter()
1013                         // filter out None values
1014                         .filter_map(|opt_impl_method| opt_impl_method)
1015                         // create translation items
1016                         .filter_map(|impl_method| {
1017                             if can_have_local_instance(ccx, impl_method.method.def_id) {
1018                                 let substs = ccx.tcx().mk_substs(impl_method.substs);
1019                                 Some(create_fn_trans_item(ccx,
1020                                                           impl_method.method.def_id,
1021                                                           substs,
1022                                                           &Substs::trans_empty()))
1023                             } else {
1024                                 None
1025                             }
1026                         })
1027                         .collect::<Vec<_>>();
1028
1029                     output.extend(items.into_iter());
1030                 }
1031                 _ => { /* */ }
1032             }
1033         }
1034     }
1035 }
1036
1037 //=-----------------------------------------------------------------------------
1038 // Root Collection
1039 //=-----------------------------------------------------------------------------
1040
1041 struct RootCollector<'b, 'a: 'b, 'tcx: 'a + 'b> {
1042     ccx: &'b CrateContext<'a, 'tcx>,
1043     mode: TransItemCollectionMode,
1044     output: &'b mut Vec<TransItem<'tcx>>,
1045     enclosing_item: Option<&'tcx hir::Item>,
1046     trans_empty_substs: &'tcx Substs<'tcx>
1047 }
1048
1049 impl<'b, 'a, 'v> hir_visit::Visitor<'v> for RootCollector<'b, 'a, 'v> {
1050     fn visit_item(&mut self, item: &'v hir::Item) {
1051         let old_enclosing_item = self.enclosing_item;
1052         self.enclosing_item = Some(item);
1053
1054         match item.node {
1055             hir::ItemExternCrate(..) |
1056             hir::ItemUse(..)         |
1057             hir::ItemForeignMod(..)  |
1058             hir::ItemTy(..)          |
1059             hir::ItemDefaultImpl(..) |
1060             hir::ItemTrait(..)       |
1061             hir::ItemConst(..)       |
1062             hir::ItemMod(..)         => {
1063                 // Nothing to do, just keep recursing...
1064             }
1065
1066             hir::ItemImpl(..) => {
1067                 if self.mode == TransItemCollectionMode::Eager {
1068                     create_trans_items_for_default_impls(self.ccx,
1069                                                          item,
1070                                                          self.trans_empty_substs,
1071                                                          self.output);
1072                 }
1073             }
1074
1075             hir::ItemEnum(_, ref generics)        |
1076             hir::ItemStruct(_, ref generics)      => {
1077                 if !generics.is_parameterized() {
1078                     let ty = {
1079                         let tables = self.ccx.tcx().tables.borrow();
1080                         tables.node_types[&item.id]
1081                     };
1082
1083                     if self.mode == TransItemCollectionMode::Eager {
1084                         debug!("RootCollector: ADT drop-glue for {}",
1085                                def_id_to_string(self.ccx,
1086                                                 self.ccx.tcx().map.local_def_id(item.id),
1087                                                 None));
1088
1089                         create_drop_glue_trans_items(self.ccx,
1090                                                      ty,
1091                                                      self.trans_empty_substs,
1092                                                      self.output);
1093                     }
1094                 }
1095             }
1096             hir::ItemStatic(..) => {
1097                 debug!("RootCollector: ItemStatic({})",
1098                        def_id_to_string(self.ccx,
1099                                         self.ccx.tcx().map.local_def_id(item.id),
1100                                         None));
1101                 self.output.push(TransItem::Static(item.id));
1102             }
1103             hir::ItemFn(_, _, constness, _, ref generics, _) => {
1104                 if !generics.is_type_parameterized() &&
1105                    constness == hir::Constness::NotConst {
1106                     let def_id = self.ccx.tcx().map.local_def_id(item.id);
1107
1108                     debug!("RootCollector: ItemFn({})",
1109                            def_id_to_string(self.ccx, def_id, None));
1110
1111                     self.output.push(TransItem::Fn {
1112                         def_id: def_id,
1113                         substs: self.trans_empty_substs
1114                     });
1115                 }
1116             }
1117         }
1118
1119         hir_visit::walk_item(self, item);
1120         self.enclosing_item = old_enclosing_item;
1121     }
1122
1123     fn visit_impl_item(&mut self, ii: &'v hir::ImplItem) {
1124         match ii.node {
1125             hir::ImplItemKind::Method(hir::MethodSig {
1126                 ref generics,
1127                 constness,
1128                 ..
1129             }, _) if constness == hir::Constness::NotConst => {
1130                 let hir_map = &self.ccx.tcx().map;
1131                 let parent_node_id = hir_map.get_parent_node(ii.id);
1132                 let is_impl_generic = match hir_map.expect_item(parent_node_id) {
1133                     &hir::Item {
1134                         node: hir::ItemImpl(_, _, ref generics, _, _, _),
1135                         ..
1136                     } => {
1137                         generics.is_type_parameterized()
1138                     }
1139                     _ => {
1140                         unreachable!()
1141                     }
1142                 };
1143
1144                 if !generics.is_type_parameterized() && !is_impl_generic {
1145                     let def_id = self.ccx.tcx().map.local_def_id(ii.id);
1146
1147                     debug!("RootCollector: MethodImplItem({})",
1148                            def_id_to_string(self.ccx, def_id, None));
1149
1150                     self.output.push(TransItem::Fn {
1151                         def_id: def_id,
1152                         substs: self.trans_empty_substs
1153                     });
1154                 }
1155             }
1156             _ => { /* Nothing to do here */ }
1157         }
1158
1159         hir_visit::walk_impl_item(self, ii)
1160     }
1161 }
1162
1163 fn create_trans_items_for_default_impls<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
1164                                                   item: &'tcx hir::Item,
1165                                                   trans_empty_substs: &'tcx Substs<'tcx>,
1166                                                   output: &mut Vec<TransItem<'tcx>>) {
1167     match item.node {
1168         hir::ItemImpl(_,
1169                       _,
1170                       ref generics,
1171                       _,
1172                       _,
1173                       ref items) => {
1174             if generics.is_type_parameterized() {
1175                 return
1176             }
1177
1178             let tcx = ccx.tcx();
1179             let impl_def_id = tcx.map.local_def_id(item.id);
1180
1181             debug!("create_trans_items_for_default_impls(item={})",
1182                    def_id_to_string(ccx, impl_def_id, None));
1183
1184             if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1185                 let default_impls = tcx.provided_trait_methods(trait_ref.def_id);
1186                 let callee_substs = tcx.mk_substs(tcx.erase_regions(trait_ref.substs));
1187                 let overridden_methods: FnvHashSet<_> = items.iter()
1188                                                              .map(|item| item.name)
1189                                                              .collect();
1190                 for default_impl in default_impls {
1191                     if overridden_methods.contains(&default_impl.name) {
1192                         continue;
1193                     }
1194
1195                     if default_impl.generics.has_type_params(subst::FnSpace) {
1196                         continue;
1197                     }
1198
1199                     // The substitutions we have are on the impl, so we grab
1200                     // the method type from the impl to substitute into.
1201                     let mth = tcx.get_impl_method(impl_def_id,
1202                                                   callee_substs.clone(),
1203                                                   default_impl.name);
1204
1205                     assert!(mth.is_provided);
1206
1207                     let predicates = mth.method.predicates.predicates.subst(tcx, &mth.substs);
1208                     if !normalize_and_test_predicates(ccx, predicates.into_vec()) {
1209                         continue;
1210                     }
1211
1212                     if can_have_local_instance(ccx, default_impl.def_id) {
1213                         let item = create_fn_trans_item(ccx,
1214                                                         default_impl.def_id,
1215                                                         callee_substs,
1216                                                         trans_empty_substs);
1217                         output.push(item);
1218                     }
1219                 }
1220             }
1221         }
1222         _ => {
1223             unreachable!()
1224         }
1225     }
1226 }
1227
1228 //=-----------------------------------------------------------------------------
1229 // TransItem String Keys
1230 //=-----------------------------------------------------------------------------
1231
1232 // The code below allows for producing a unique string key for a trans item.
1233 // These keys are used by the handwritten auto-tests, so they need to be
1234 // predictable and human-readable.
1235 //
1236 // Note: A lot of this could looks very similar to what's already in the
1237 //       ppaux module. It would be good to refactor things so we only have one
1238 //       parameterizable implementation for printing types.
1239
1240 /// Same as `unique_type_name()` but with the result pushed onto the given
1241 /// `output` parameter.
1242 pub fn push_unique_type_name<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
1243                                        t: ty::Ty<'tcx>,
1244                                        output: &mut String) {
1245     match t.sty {
1246         ty::TyBool              => output.push_str("bool"),
1247         ty::TyChar              => output.push_str("char"),
1248         ty::TyStr               => output.push_str("str"),
1249         ty::TyInt(ast::TyIs)    => output.push_str("isize"),
1250         ty::TyInt(ast::TyI8)    => output.push_str("i8"),
1251         ty::TyInt(ast::TyI16)   => output.push_str("i16"),
1252         ty::TyInt(ast::TyI32)   => output.push_str("i32"),
1253         ty::TyInt(ast::TyI64)   => output.push_str("i64"),
1254         ty::TyUint(ast::TyUs)   => output.push_str("usize"),
1255         ty::TyUint(ast::TyU8)   => output.push_str("u8"),
1256         ty::TyUint(ast::TyU16)  => output.push_str("u16"),
1257         ty::TyUint(ast::TyU32)  => output.push_str("u32"),
1258         ty::TyUint(ast::TyU64)  => output.push_str("u64"),
1259         ty::TyFloat(ast::TyF32) => output.push_str("f32"),
1260         ty::TyFloat(ast::TyF64) => output.push_str("f64"),
1261         ty::TyStruct(adt_def, substs) |
1262         ty::TyEnum(adt_def, substs) => {
1263             push_item_name(cx, adt_def.did, output);
1264             push_type_params(cx, substs, &[], output);
1265         },
1266         ty::TyTuple(ref component_types) => {
1267             output.push('(');
1268             for &component_type in component_types {
1269                 push_unique_type_name(cx, component_type, output);
1270                 output.push_str(", ");
1271             }
1272             if !component_types.is_empty() {
1273                 output.pop();
1274                 output.pop();
1275             }
1276             output.push(')');
1277         },
1278         ty::TyBox(inner_type) => {
1279             output.push_str("Box<");
1280             push_unique_type_name(cx, inner_type, output);
1281             output.push('>');
1282         },
1283         ty::TyRawPtr(ty::TypeAndMut { ty: inner_type, mutbl } ) => {
1284             output.push('*');
1285             match mutbl {
1286                 hir::MutImmutable => output.push_str("const "),
1287                 hir::MutMutable => output.push_str("mut "),
1288             }
1289
1290             push_unique_type_name(cx, inner_type, output);
1291         },
1292         ty::TyRef(_, ty::TypeAndMut { ty: inner_type, mutbl }) => {
1293             output.push('&');
1294             if mutbl == hir::MutMutable {
1295                 output.push_str("mut ");
1296             }
1297
1298             push_unique_type_name(cx, inner_type, output);
1299         },
1300         ty::TyArray(inner_type, len) => {
1301             output.push('[');
1302             push_unique_type_name(cx, inner_type, output);
1303             output.push_str(&format!("; {}", len));
1304             output.push(']');
1305         },
1306         ty::TySlice(inner_type) => {
1307             output.push('[');
1308             push_unique_type_name(cx, inner_type, output);
1309             output.push(']');
1310         },
1311         ty::TyTrait(ref trait_data) => {
1312             push_item_name(cx, trait_data.principal.skip_binder().def_id, output);
1313             push_type_params(cx,
1314                              &trait_data.principal.skip_binder().substs,
1315                              &trait_data.bounds.projection_bounds,
1316                              output);
1317         },
1318         ty::TyBareFn(_, &ty::BareFnTy{ unsafety, abi, ref sig } ) => {
1319             if unsafety == hir::Unsafety::Unsafe {
1320                 output.push_str("unsafe ");
1321             }
1322
1323             if abi != ::syntax::abi::Rust {
1324                 output.push_str("extern \"");
1325                 output.push_str(abi.name());
1326                 output.push_str("\" ");
1327             }
1328
1329             output.push_str("fn(");
1330
1331             let sig = cx.tcx().erase_late_bound_regions(sig);
1332             if !sig.inputs.is_empty() {
1333                 for &parameter_type in &sig.inputs {
1334                     push_unique_type_name(cx, parameter_type, output);
1335                     output.push_str(", ");
1336                 }
1337                 output.pop();
1338                 output.pop();
1339             }
1340
1341             if sig.variadic {
1342                 if !sig.inputs.is_empty() {
1343                     output.push_str(", ...");
1344                 } else {
1345                     output.push_str("...");
1346                 }
1347             }
1348
1349             output.push(')');
1350
1351             match sig.output {
1352                 ty::FnConverging(result_type) if result_type.is_nil() => {}
1353                 ty::FnConverging(result_type) => {
1354                     output.push_str(" -> ");
1355                     push_unique_type_name(cx, result_type, output);
1356                 }
1357                 ty::FnDiverging => {
1358                     output.push_str(" -> !");
1359                 }
1360             }
1361         },
1362         ty::TyClosure(def_id, ref closure_substs) => {
1363             push_item_name(cx, def_id, output);
1364             output.push_str("{");
1365             output.push_str(&format!("{}:{}", def_id.krate, def_id.index.as_usize()));
1366             output.push_str("}");
1367             push_type_params(cx, closure_substs.func_substs, &[], output);
1368         }
1369         ty::TyError |
1370         ty::TyInfer(_) |
1371         ty::TyProjection(..) |
1372         ty::TyParam(_) => {
1373             cx.sess().bug(&format!("debuginfo: Trying to create type name for \
1374                 unexpected type: {:?}", t));
1375         }
1376     }
1377 }
1378
1379 fn push_item_name(ccx: &CrateContext,
1380                   def_id: DefId,
1381                   output: &mut String) {
1382     if def_id.is_local() {
1383         let node_id = ccx.tcx().map.as_local_node_id(def_id).unwrap();
1384         let inlined_from = ccx.external_srcs()
1385                               .borrow()
1386                               .get(&node_id)
1387                               .map(|def_id| *def_id);
1388
1389         if let Some(extern_def_id) = inlined_from {
1390             push_item_name(ccx, extern_def_id, output);
1391             return;
1392         }
1393
1394         output.push_str(&ccx.link_meta().crate_name);
1395         output.push_str("::");
1396     }
1397
1398     for part in ccx.tcx().def_path(def_id) {
1399         output.push_str(&format!("{}[{}]::",
1400                         part.data.as_interned_str(),
1401                         part.disambiguator));
1402     }
1403
1404     output.pop();
1405     output.pop();
1406 }
1407
1408 fn push_type_params<'a, 'tcx>(cx: &CrateContext<'a, 'tcx>,
1409                               substs: &Substs<'tcx>,
1410                               projections: &[ty::PolyProjectionPredicate<'tcx>],
1411                               output: &mut String) {
1412     if substs.types.is_empty() && projections.is_empty() {
1413         return;
1414     }
1415
1416     output.push('<');
1417
1418     for &type_parameter in &substs.types {
1419         push_unique_type_name(cx, type_parameter, output);
1420         output.push_str(", ");
1421     }
1422
1423     for projection in projections {
1424         let projection = projection.skip_binder();
1425         let name = token::get_ident_interner().get(projection.projection_ty.item_name);
1426         output.push_str(&name[..]);
1427         output.push_str("=");
1428         push_unique_type_name(cx, projection.ty, output);
1429         output.push_str(", ");
1430     }
1431
1432     output.pop();
1433     output.pop();
1434
1435     output.push('>');
1436 }
1437
1438 fn push_def_id_as_string<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
1439                               def_id: DefId,
1440                               substs: Option<&Substs<'tcx>>,
1441                               output: &mut String) {
1442     push_item_name(ccx, def_id, output);
1443
1444     if let Some(substs) = substs {
1445         push_type_params(ccx, substs, &[], output);
1446     }
1447 }
1448
1449 fn def_id_to_string<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
1450                               def_id: DefId,
1451                               substs: Option<&Substs<'tcx>>)
1452                               -> String {
1453     let mut output = String::new();
1454     push_def_id_as_string(ccx, def_id, substs, &mut output);
1455     output
1456 }
1457
1458 fn type_to_string<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
1459                             ty: ty::Ty<'tcx>)
1460                             -> String {
1461     let mut output = String::new();
1462     push_unique_type_name(ccx, ty, &mut output);
1463     output
1464 }
1465
1466 impl<'tcx> TransItem<'tcx> {
1467
1468     pub fn to_string<'a>(&self, ccx: &CrateContext<'a, 'tcx>) -> String {
1469         let hir_map = &ccx.tcx().map;
1470
1471         return match *self {
1472             TransItem::DropGlue(t) => {
1473                 let mut s = String::with_capacity(32);
1474                 s.push_str("drop-glue ");
1475                 push_unique_type_name(ccx, t, &mut s);
1476                 s
1477             }
1478             TransItem::Fn { def_id, ref substs } => {
1479                 to_string_internal(ccx, "fn ", def_id, Some(substs))
1480             },
1481             TransItem::Static(node_id) => {
1482                 let def_id = hir_map.local_def_id(node_id);
1483                 to_string_internal(ccx, "static ", def_id, None)
1484             },
1485         };
1486
1487         fn to_string_internal<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>,
1488                                         prefix: &str,
1489                                         def_id: DefId,
1490                                         substs: Option<&Substs<'tcx>>)
1491                                         -> String {
1492             let mut result = String::with_capacity(32);
1493             result.push_str(prefix);
1494             push_def_id_as_string(ccx, def_id, substs, &mut result);
1495             result
1496         }
1497     }
1498
1499     fn to_raw_string(&self) -> String {
1500         match *self {
1501             TransItem::DropGlue(t) => {
1502                 format!("DropGlue({})", t as *const _ as usize)
1503             }
1504             TransItem::Fn { def_id, substs } => {
1505                 format!("Fn({:?}, {})",
1506                          def_id,
1507                          substs as *const _ as usize)
1508             }
1509             TransItem::Static(id) => {
1510                 format!("Static({:?})", id)
1511             }
1512         }
1513     }
1514 }
1515
1516 #[derive(Debug, Clone, Copy, PartialEq, Eq, Hash)]
1517 pub enum TransItemState {
1518     PredictedAndGenerated,
1519     PredictedButNotGenerated,
1520     NotPredictedButGenerated,
1521 }
1522
1523 pub fn collecting_debug_information(ccx: &CrateContext) -> bool {
1524     return cfg!(debug_assertions) &&
1525            ccx.sess().opts.debugging_opts.print_trans_items.is_some();
1526 }
1527
1528 pub fn print_collection_results<'a, 'tcx>(ccx: &CrateContext<'a, 'tcx>) {
1529     use std::hash::{Hash, SipHasher, Hasher};
1530
1531     if !collecting_debug_information(ccx) {
1532         return;
1533     }
1534
1535     fn hash<T: Hash>(t: &T) -> u64 {
1536         let mut s = SipHasher::new();
1537         t.hash(&mut s);
1538         s.finish()
1539     }
1540
1541     let trans_items = ccx.translation_items().borrow();
1542
1543     {
1544         // Check for duplicate item keys
1545         let mut item_keys = FnvHashMap();
1546
1547         for (item, item_state) in trans_items.iter() {
1548             let k = item.to_string(&ccx);
1549
1550             if item_keys.contains_key(&k) {
1551                 let prev: (TransItem, TransItemState) = item_keys[&k];
1552                 debug!("DUPLICATE KEY: {}", k);
1553                 debug!(" (1) {:?}, {:?}, hash: {}, raw: {}",
1554                        prev.0,
1555                        prev.1,
1556                        hash(&prev.0),
1557                        prev.0.to_raw_string());
1558
1559                 debug!(" (2) {:?}, {:?}, hash: {}, raw: {}",
1560                        *item,
1561                        *item_state,
1562                        hash(item),
1563                        item.to_raw_string());
1564             } else {
1565                 item_keys.insert(k, (*item, *item_state));
1566             }
1567         }
1568     }
1569
1570     let mut predicted_but_not_generated = FnvHashSet();
1571     let mut not_predicted_but_generated = FnvHashSet();
1572     let mut predicted = FnvHashSet();
1573     let mut generated = FnvHashSet();
1574
1575     for (item, item_state) in trans_items.iter() {
1576         let item_key = item.to_string(&ccx);
1577
1578         match *item_state {
1579             TransItemState::PredictedAndGenerated => {
1580                 predicted.insert(item_key.clone());
1581                 generated.insert(item_key);
1582             }
1583             TransItemState::PredictedButNotGenerated => {
1584                 predicted_but_not_generated.insert(item_key.clone());
1585                 predicted.insert(item_key);
1586             }
1587             TransItemState::NotPredictedButGenerated => {
1588                 not_predicted_but_generated.insert(item_key.clone());
1589                 generated.insert(item_key);
1590             }
1591         }
1592     }
1593
1594     debug!("Total number of translation items predicted: {}", predicted.len());
1595     debug!("Total number of translation items generated: {}", generated.len());
1596     debug!("Total number of translation items predicted but not generated: {}",
1597            predicted_but_not_generated.len());
1598     debug!("Total number of translation items not predicted but generated: {}",
1599            not_predicted_but_generated.len());
1600
1601     if generated.len() > 0 {
1602         debug!("Failed to predict {}% of translation items",
1603                (100 * not_predicted_but_generated.len()) / generated.len());
1604     }
1605     if generated.len() > 0 {
1606         debug!("Predict {}% too many translation items",
1607                (100 * predicted_but_not_generated.len()) / generated.len());
1608     }
1609
1610     debug!("");
1611     debug!("Not predicted but generated:");
1612     debug!("============================");
1613     for item in not_predicted_but_generated {
1614         debug!(" - {}", item);
1615     }
1616
1617     debug!("");
1618     debug!("Predicted but not generated:");
1619     debug!("============================");
1620     for item in predicted_but_not_generated {
1621         debug!(" - {}", item);
1622     }
1623 }