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.
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.
11 //! Translation Item Collection
12 //! ===========================
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.
25 //! The following kinds of "translation items" are handled here:
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
44 //! Let's define some terms first:
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
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".
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.
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:
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.
70 //! ### Discovering roots
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.
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:
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.
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:
101 //! fn print_val<T: Display>(x: T) {
102 //! println!("{}", x);
105 //! fn call_fn(f: &Fn(i32), x: i32) {
110 //! let print_i32 = print_val::<i32>;
111 //! call_fn(&print_i32, 0);
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.
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.
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.
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.
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.
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
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 the 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.
160 //! Eager and Lazy Collection Mode
161 //! ------------------------------
162 //! Translation item collection can be performed in one of two modes:
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
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.
178 //! Some things are not yet fully implemented in the current version of this
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.
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.
192 use rustc::hir::itemlikevisit::ItemLikeVisitor;
194 use rustc::hir::map as hir_map;
195 use rustc::hir::def_id::DefId;
196 use rustc::middle::lang_items::{BoxFreeFnLangItem, ExchangeMallocFnLangItem};
198 use rustc::ty::subst::{Kind, Substs, Subst};
199 use rustc::ty::{self, TypeFoldable, TyCtxt};
200 use rustc::ty::adjustment::CustomCoerceUnsized;
201 use rustc::mir::{self, Location};
202 use rustc::mir::visit as mir_visit;
203 use rustc::mir::visit::Visitor as MirVisitor;
205 use syntax::abi::Abi;
206 use syntax_pos::DUMMY_SP;
207 use base::custom_coerce_unsize_info;
208 use callee::needs_fn_once_adapter_shim;
209 use context::SharedCrateContext;
210 use common::fulfill_obligation;
211 use glue::{self, DropGlueKind};
212 use monomorphize::{self, Instance};
213 use util::nodemap::{FxHashSet, FxHashMap, DefIdMap};
215 use trans_item::{TransItem, DefPathBasedNames};
219 #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
220 pub enum TransItemCollectionMode {
225 /// Maps every translation item to all translation items it references in its
227 pub struct InliningMap<'tcx> {
228 // Maps a source translation item to a range of target translation items
229 // that are potentially inlined by LLVM into the source.
230 // The two numbers in the tuple are the start (inclusive) and
231 // end index (exclusive) within the `targets` vecs.
232 index: FxHashMap<TransItem<'tcx>, (usize, usize)>,
233 targets: Vec<TransItem<'tcx>>,
236 impl<'tcx> InliningMap<'tcx> {
238 fn new() -> InliningMap<'tcx> {
245 fn record_inlining_canditates<I>(&mut self,
246 source: TransItem<'tcx>,
248 where I: Iterator<Item=TransItem<'tcx>>
250 assert!(!self.index.contains_key(&source));
252 let start_index = self.targets.len();
253 self.targets.extend(targets);
254 let end_index = self.targets.len();
255 self.index.insert(source, (start_index, end_index));
258 // Internally iterate over all items referenced by `source` which will be
259 // made available for inlining.
260 pub fn with_inlining_candidates<F>(&self, source: TransItem<'tcx>, mut f: F)
261 where F: FnMut(TransItem<'tcx>) {
262 if let Some(&(start_index, end_index)) = self.index.get(&source)
264 for candidate in &self.targets[start_index .. end_index] {
271 pub fn collect_crate_translation_items<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
272 mode: TransItemCollectionMode)
273 -> (FxHashSet<TransItem<'tcx>>,
275 // We are not tracking dependencies of this pass as it has to be re-executed
276 // every time no matter what.
277 scx.tcx().dep_graph.with_ignore(|| {
278 let roots = collect_roots(scx, mode);
280 debug!("Building translation item graph, beginning at roots");
281 let mut visited = FxHashSet();
282 let mut recursion_depths = DefIdMap();
283 let mut inlining_map = InliningMap::new();
286 collect_items_rec(scx,
289 &mut recursion_depths,
293 (visited, inlining_map)
297 // Find all non-generic items by walking the HIR. These items serve as roots to
298 // start monomorphizing from.
299 fn collect_roots<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
300 mode: TransItemCollectionMode)
301 -> Vec<TransItem<'tcx>> {
302 debug!("Collecting roots");
303 let mut roots = Vec::new();
306 let mut visitor = RootCollector {
312 scx.tcx().map.krate().visit_all_item_likes(&mut visitor);
318 // Collect all monomorphized translation items reachable from `starting_point`
319 fn collect_items_rec<'a, 'tcx: 'a>(scx: &SharedCrateContext<'a, 'tcx>,
320 starting_point: TransItem<'tcx>,
321 visited: &mut FxHashSet<TransItem<'tcx>>,
322 recursion_depths: &mut DefIdMap<usize>,
323 inlining_map: &mut InliningMap<'tcx>) {
324 if !visited.insert(starting_point.clone()) {
325 // We've been here already, no need to search again.
328 debug!("BEGIN collect_items_rec({})", starting_point.to_string(scx.tcx()));
330 let mut neighbors = Vec::new();
331 let recursion_depth_reset;
333 match starting_point {
334 TransItem::DropGlue(t) => {
335 find_drop_glue_neighbors(scx, t, &mut neighbors);
336 recursion_depth_reset = None;
338 TransItem::Static(node_id) => {
339 let def_id = scx.tcx().map.local_def_id(node_id);
340 let ty = scx.tcx().item_type(def_id);
341 let ty = glue::get_drop_glue_type(scx, ty);
342 neighbors.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
344 recursion_depth_reset = None;
346 collect_neighbours(scx, Instance::mono(scx, def_id), &mut neighbors);
348 TransItem::Fn(instance) => {
349 // Keep track of the monomorphization recursion depth
350 recursion_depth_reset = Some(check_recursion_limit(scx.tcx(),
353 check_type_length_limit(scx.tcx(), instance);
355 collect_neighbours(scx, instance, &mut neighbors);
359 record_inlining_canditates(scx.tcx(), starting_point, &neighbors[..], inlining_map);
361 for neighbour in neighbors {
362 collect_items_rec(scx, neighbour, visited, recursion_depths, inlining_map);
365 if let Some((def_id, depth)) = recursion_depth_reset {
366 recursion_depths.insert(def_id, depth);
369 debug!("END collect_items_rec({})", starting_point.to_string(scx.tcx()));
372 fn record_inlining_canditates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
373 caller: TransItem<'tcx>,
374 callees: &[TransItem<'tcx>],
375 inlining_map: &mut InliningMap<'tcx>) {
376 let is_inlining_candidate = |trans_item: &TransItem<'tcx>| {
377 trans_item.needs_local_copy(tcx)
380 let inlining_candidates = callees.into_iter()
382 .filter(is_inlining_candidate);
384 inlining_map.record_inlining_canditates(caller, inlining_candidates);
387 fn check_recursion_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
388 instance: Instance<'tcx>,
389 recursion_depths: &mut DefIdMap<usize>)
391 let recursion_depth = recursion_depths.get(&instance.def)
394 debug!(" => recursion depth={}", recursion_depth);
396 // Code that needs to instantiate the same function recursively
397 // more than the recursion limit is assumed to be causing an
398 // infinite expansion.
399 if recursion_depth > tcx.sess.recursion_limit.get() {
400 let error = format!("reached the recursion limit while instantiating `{}`",
402 if let Some(node_id) = tcx.map.as_local_node_id(instance.def) {
403 tcx.sess.span_fatal(tcx.map.span(node_id), &error);
405 tcx.sess.fatal(&error);
409 recursion_depths.insert(instance.def, recursion_depth + 1);
411 (instance.def, recursion_depth)
414 fn check_type_length_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
415 instance: Instance<'tcx>)
417 let type_length = instance.substs.types().flat_map(|ty| ty.walk()).count();
418 debug!(" => type length={}", type_length);
420 // Rust code can easily create exponentially-long types using only a
421 // polynomial recursion depth. Even with the default recursion
422 // depth, you can easily get cases that take >2^60 steps to run,
423 // which means that rustc basically hangs.
425 // Bail out in these cases to avoid that bad user experience.
426 let type_length_limit = tcx.sess.type_length_limit.get();
427 if type_length > type_length_limit {
428 // The instance name is already known to be too long for rustc. Use
429 // `{:.64}` to avoid blasting the user's terminal with thousands of
430 // lines of type-name.
431 let instance_name = instance.to_string();
432 let msg = format!("reached the type-length limit while instantiating `{:.64}...`",
434 let mut diag = if let Some(node_id) = tcx.map.as_local_node_id(instance.def) {
435 tcx.sess.struct_span_fatal(tcx.map.span(node_id), &msg)
437 tcx.sess.struct_fatal(&msg)
441 "consider adding a `#![type_length_limit=\"{}\"]` attribute to your crate",
442 type_length_limit*2));
444 tcx.sess.abort_if_errors();
448 struct MirNeighborCollector<'a, 'tcx: 'a> {
449 scx: &'a SharedCrateContext<'a, 'tcx>,
450 mir: &'a mir::Mir<'tcx>,
451 output: &'a mut Vec<TransItem<'tcx>>,
452 param_substs: &'tcx Substs<'tcx>
455 impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
457 fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: Location) {
458 debug!("visiting rvalue {:?}", *rvalue);
461 // When doing an cast from a regular pointer to a fat pointer, we
462 // have to instantiate all methods of the trait being cast to, so we
463 // can build the appropriate vtable.
464 mir::Rvalue::Cast(mir::CastKind::Unsize, ref operand, target_ty) => {
465 let target_ty = monomorphize::apply_param_substs(self.scx,
468 let source_ty = operand.ty(self.mir, self.scx.tcx());
469 let source_ty = monomorphize::apply_param_substs(self.scx,
472 let (source_ty, target_ty) = find_vtable_types_for_unsizing(self.scx,
475 // This could also be a different Unsize instruction, like
476 // from a fixed sized array to a slice. But we are only
477 // interested in things that produce a vtable.
478 if target_ty.is_trait() && !source_ty.is_trait() {
479 create_trans_items_for_vtable_methods(self.scx,
485 mir::Rvalue::Box(..) => {
486 let exchange_malloc_fn_def_id =
490 .require(ExchangeMallocFnLangItem)
491 .unwrap_or_else(|e| self.scx.sess().fatal(&e));
493 assert!(can_have_local_instance(self.scx.tcx(), exchange_malloc_fn_def_id));
494 let empty_substs = self.scx.empty_substs_for_def_id(exchange_malloc_fn_def_id);
495 let exchange_malloc_fn_trans_item =
496 create_fn_trans_item(self.scx,
497 exchange_malloc_fn_def_id,
501 self.output.push(exchange_malloc_fn_trans_item);
503 _ => { /* not interesting */ }
506 self.super_rvalue(rvalue, location);
509 fn visit_lvalue(&mut self,
510 lvalue: &mir::Lvalue<'tcx>,
511 context: mir_visit::LvalueContext<'tcx>,
512 location: Location) {
513 debug!("visiting lvalue {:?}", *lvalue);
515 if let mir_visit::LvalueContext::Drop = context {
516 let ty = lvalue.ty(self.mir, self.scx.tcx())
517 .to_ty(self.scx.tcx());
519 let ty = monomorphize::apply_param_substs(self.scx,
522 assert!(ty.is_normalized_for_trans());
523 let ty = glue::get_drop_glue_type(self.scx, ty);
524 self.output.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
527 self.super_lvalue(lvalue, context, location);
530 fn visit_operand(&mut self, operand: &mir::Operand<'tcx>, location: Location) {
531 debug!("visiting operand {:?}", *operand);
533 let callee = match *operand {
534 mir::Operand::Constant(ref constant) => {
535 if let ty::TyFnDef(def_id, substs, _) = constant.ty.sty {
536 // This is something that can act as a callee, proceed
537 Some((def_id, substs))
539 // This is not a callee, but we still have to look for
540 // references to `const` items
541 if let mir::Literal::Item { def_id, substs } = constant.literal {
542 let substs = monomorphize::apply_param_substs(self.scx,
546 let instance = Instance::new(def_id, substs).resolve_const(self.scx);
547 collect_neighbours(self.scx, instance, self.output);
556 if let Some((callee_def_id, callee_substs)) = callee {
557 debug!(" => operand is callable");
559 // `callee_def_id` might refer to a trait method instead of a
560 // concrete implementation, so we have to find the actual
561 // implementation. For example, the call might look like
563 // std::cmp::partial_cmp(0i32, 1i32)
565 // Calling do_static_dispatch() here will map the def_id of
566 // `std::cmp::partial_cmp` to the def_id of `i32::partial_cmp<i32>`
567 let dispatched = do_static_dispatch(self.scx,
572 if let StaticDispatchResult::Dispatched {
573 def_id: callee_def_id,
574 substs: callee_substs,
577 // if we have a concrete impl (which we might not have
578 // in the case of something compiler generated like an
579 // object shim or a closure that is handled differently),
580 // we check if the callee is something that will actually
581 // result in a translation item ...
582 if can_result_in_trans_item(self.scx.tcx(), callee_def_id) {
583 // ... and create one if it does.
584 let trans_item = create_fn_trans_item(self.scx,
588 self.output.push(trans_item);
590 // This call will instantiate an FnOnce adapter, which drops
591 // the closure environment. Therefore we need to make sure
592 // that we collect the drop-glue for the environment type.
593 if let Some(env_ty) = fn_once_adjustment {
594 let env_ty = glue::get_drop_glue_type(self.scx, env_ty);
595 if self.scx.type_needs_drop(env_ty) {
596 let dg = DropGlueKind::Ty(env_ty);
597 self.output.push(TransItem::DropGlue(dg));
604 self.super_operand(operand, location);
606 fn can_result_in_trans_item<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
609 match tcx.item_type(def_id).sty {
610 ty::TyFnDef(def_id, _, f) => {
611 // Some constructors also have type TyFnDef but they are
612 // always instantiated inline and don't result in
613 // translation item. Same for FFI functions.
614 if let Some(hir_map::NodeForeignItem(_)) = tcx.map.get_if_local(def_id) {
618 if let Some(adt_def) = f.sig.output().skip_binder().ty_adt_def() {
619 if adt_def.variants.iter().any(|v| def_id == v.did) {
624 ty::TyClosure(..) => {}
628 can_have_local_instance(tcx, def_id)
632 // This takes care of the "drop_in_place" intrinsic for which we otherwise
633 // we would not register drop-glues.
634 fn visit_terminator_kind(&mut self,
635 block: mir::BasicBlock,
636 kind: &mir::TerminatorKind<'tcx>,
637 location: Location) {
638 let tcx = self.scx.tcx();
640 mir::TerminatorKind::Call {
641 func: mir::Operand::Constant(ref constant),
645 match constant.ty.sty {
646 ty::TyFnDef(def_id, _, bare_fn_ty)
647 if is_drop_in_place_intrinsic(tcx, def_id, bare_fn_ty) => {
648 let operand_ty = args[0].ty(self.mir, tcx);
649 if let ty::TyRawPtr(mt) = operand_ty.sty {
650 let operand_ty = monomorphize::apply_param_substs(self.scx,
653 let ty = glue::get_drop_glue_type(self.scx, operand_ty);
654 self.output.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
656 bug!("Has the drop_in_place() intrinsic's signature changed?")
659 _ => { /* Nothing to do. */ }
662 _ => { /* Nothing to do. */ }
665 self.super_terminator_kind(block, kind, location);
667 fn is_drop_in_place_intrinsic<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
669 bare_fn_ty: &ty::BareFnTy<'tcx>)
671 (bare_fn_ty.abi == Abi::RustIntrinsic ||
672 bare_fn_ty.abi == Abi::PlatformIntrinsic) &&
673 tcx.item_name(def_id) == "drop_in_place"
678 fn can_have_local_instance<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
681 tcx.sess.cstore.can_have_local_instance(tcx, def_id)
684 fn find_drop_glue_neighbors<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
685 dg: DropGlueKind<'tcx>,
686 output: &mut Vec<TransItem<'tcx>>) {
688 DropGlueKind::Ty(ty) => ty,
689 DropGlueKind::TyContents(_) => {
690 // We already collected the neighbors of this item via the
691 // DropGlueKind::Ty variant.
696 debug!("find_drop_glue_neighbors: {}", type_to_string(scx.tcx(), ty));
698 // Make sure the BoxFreeFn lang-item gets translated if there is a boxed value.
699 if let ty::TyBox(content_type) = ty.sty {
700 let def_id = scx.tcx().require_lang_item(BoxFreeFnLangItem);
701 assert!(can_have_local_instance(scx.tcx(), def_id));
702 let box_free_fn_trans_item =
703 create_fn_trans_item(scx,
705 scx.tcx().mk_substs(iter::once(Kind::from(content_type))),
706 scx.tcx().intern_substs(&[]));
708 output.push(box_free_fn_trans_item);
711 // If the type implements Drop, also add a translation item for the
712 // monomorphized Drop::drop() implementation.
713 let destructor_did = match ty.sty {
714 ty::TyAdt(def, _) => def.destructor(),
718 if let Some(destructor_did) = destructor_did {
719 use rustc::ty::ToPolyTraitRef;
721 let drop_trait_def_id = scx.tcx()
726 let self_type_substs = scx.tcx().mk_substs_trait(ty, &[]);
728 let trait_ref = ty::TraitRef {
729 def_id: drop_trait_def_id,
730 substs: self_type_substs,
731 }.to_poly_trait_ref();
733 let substs = match fulfill_obligation(scx, DUMMY_SP, trait_ref) {
734 traits::VtableImpl(data) => data.substs,
738 if can_have_local_instance(scx.tcx(), destructor_did) {
739 let trans_item = create_fn_trans_item(scx,
742 scx.tcx().intern_substs(&[]));
743 output.push(trans_item);
746 // This type has a Drop implementation, we'll need the contents-only
747 // version of the glue too.
748 output.push(TransItem::DropGlue(DropGlueKind::TyContents(ty)));
751 // Finally add the types of nested values
764 ty::TyDynamic(..) => {
767 ty::TyAdt(adt_def, substs) => {
768 for field in adt_def.all_fields() {
769 let field_type = scx.tcx().item_type(field.did);
770 let field_type = monomorphize::apply_param_substs(scx,
773 let field_type = glue::get_drop_glue_type(scx, field_type);
775 if scx.type_needs_drop(field_type) {
776 output.push(TransItem::DropGlue(DropGlueKind::Ty(field_type)));
780 ty::TyClosure(def_id, substs) => {
781 for upvar_ty in substs.upvar_tys(def_id, scx.tcx()) {
782 let upvar_ty = glue::get_drop_glue_type(scx, upvar_ty);
783 if scx.type_needs_drop(upvar_ty) {
784 output.push(TransItem::DropGlue(DropGlueKind::Ty(upvar_ty)));
788 ty::TyBox(inner_type) |
789 ty::TySlice(inner_type) |
790 ty::TyArray(inner_type, _) => {
791 let inner_type = glue::get_drop_glue_type(scx, inner_type);
792 if scx.type_needs_drop(inner_type) {
793 output.push(TransItem::DropGlue(DropGlueKind::Ty(inner_type)));
796 ty::TyTuple(args) => {
798 let arg = glue::get_drop_glue_type(scx, arg);
799 if scx.type_needs_drop(arg) {
800 output.push(TransItem::DropGlue(DropGlueKind::Ty(arg)));
804 ty::TyProjection(_) |
809 bug!("encountered unexpected type");
814 fn do_static_dispatch<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
816 fn_substs: &'tcx Substs<'tcx>,
817 param_substs: &'tcx Substs<'tcx>)
818 -> StaticDispatchResult<'tcx> {
819 debug!("do_static_dispatch(fn_def_id={}, fn_substs={:?}, param_substs={:?})",
820 def_id_to_string(scx.tcx(), fn_def_id),
824 if let Some(trait_def_id) = scx.tcx().trait_of_item(fn_def_id) {
825 debug!(" => trait method, attempting to find impl");
826 do_static_trait_method_dispatch(scx,
827 &scx.tcx().associated_item(fn_def_id),
832 debug!(" => regular function");
833 // The function is not part of an impl or trait, no dispatching
835 StaticDispatchResult::Dispatched {
838 fn_once_adjustment: None,
843 enum StaticDispatchResult<'tcx> {
844 // The call could be resolved statically as going to the method with
845 // `def_id` and `substs`.
848 substs: &'tcx Substs<'tcx>,
850 // If this is a call to a closure that needs an FnOnce adjustment,
851 // this contains the new self type of the call (= type of the closure
853 fn_once_adjustment: Option<ty::Ty<'tcx>>,
855 // This goes to somewhere that we don't know at compile-time
859 // Given a trait-method and substitution information, find out the actual
860 // implementation of the trait method.
861 fn do_static_trait_method_dispatch<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
862 trait_method: &ty::AssociatedItem,
864 callee_substs: &'tcx Substs<'tcx>,
865 param_substs: &'tcx Substs<'tcx>)
866 -> StaticDispatchResult<'tcx> {
868 debug!("do_static_trait_method_dispatch(trait_method={}, \
870 callee_substs={:?}, \
872 def_id_to_string(scx.tcx(), trait_method.def_id),
873 def_id_to_string(scx.tcx(), trait_id),
877 let rcvr_substs = monomorphize::apply_param_substs(scx,
880 let trait_ref = ty::TraitRef::from_method(tcx, trait_id, rcvr_substs);
881 let vtbl = fulfill_obligation(scx, DUMMY_SP, ty::Binder(trait_ref));
883 // Now that we know which impl is being used, we can dispatch to
884 // the actual function:
886 traits::VtableImpl(impl_data) => {
887 let (def_id, substs) = traits::find_method(tcx,
891 StaticDispatchResult::Dispatched {
894 fn_once_adjustment: None,
897 traits::VtableClosure(closure_data) => {
898 let closure_def_id = closure_data.closure_def_id;
899 let trait_closure_kind = tcx.lang_items.fn_trait_kind(trait_id).unwrap();
900 let actual_closure_kind = tcx.closure_kind(closure_def_id);
902 let needs_fn_once_adapter_shim =
903 match needs_fn_once_adapter_shim(actual_closure_kind,
904 trait_closure_kind) {
909 let fn_once_adjustment = if needs_fn_once_adapter_shim {
910 Some(tcx.mk_closure_from_closure_substs(closure_def_id,
911 closure_data.substs))
916 StaticDispatchResult::Dispatched {
917 def_id: closure_def_id,
918 substs: closure_data.substs.substs,
919 fn_once_adjustment: fn_once_adjustment,
922 // Trait object and function pointer shims are always
923 // instantiated in-place, and as they are just an ABI-adjusting
924 // indirect call they do not have any dependencies.
925 traits::VtableFnPointer(..) |
926 traits::VtableObject(..) => {
927 StaticDispatchResult::Unknown
930 bug!("static call to invalid vtable: {:?}", vtbl)
935 /// For given pair of source and target type that occur in an unsizing coercion,
936 /// this function finds the pair of types that determines the vtable linking
939 /// For example, the source type might be `&SomeStruct` and the target type\
940 /// might be `&SomeTrait` in a cast like:
942 /// let src: &SomeStruct = ...;
943 /// let target = src as &SomeTrait;
945 /// Then the output of this function would be (SomeStruct, SomeTrait) since for
946 /// constructing the `target` fat-pointer we need the vtable for that pair.
948 /// Things can get more complicated though because there's also the case where
949 /// the unsized type occurs as a field:
952 /// struct ComplexStruct<T: ?Sized> {
959 /// In this case, if `T` is sized, `&ComplexStruct<T>` is a thin pointer. If `T`
960 /// is unsized, `&SomeStruct` is a fat pointer, and the vtable it points to is
961 /// for the pair of `T` (which is a trait) and the concrete type that `T` was
962 /// originally coerced from:
964 /// let src: &ComplexStruct<SomeStruct> = ...;
965 /// let target = src as &ComplexStruct<SomeTrait>;
967 /// Again, we want this `find_vtable_types_for_unsizing()` to provide the pair
968 /// `(SomeStruct, SomeTrait)`.
970 /// Finally, there is also the case of custom unsizing coercions, e.g. for
971 /// smart pointers such as `Rc` and `Arc`.
972 fn find_vtable_types_for_unsizing<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
973 source_ty: ty::Ty<'tcx>,
974 target_ty: ty::Ty<'tcx>)
975 -> (ty::Ty<'tcx>, ty::Ty<'tcx>) {
976 match (&source_ty.sty, &target_ty.sty) {
977 (&ty::TyBox(a), &ty::TyBox(b)) |
978 (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
979 &ty::TyRef(_, ty::TypeAndMut { ty: b, .. })) |
980 (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
981 &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) |
982 (&ty::TyRawPtr(ty::TypeAndMut { ty: a, .. }),
983 &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) => {
984 let (inner_source, inner_target) = (a, b);
986 if !scx.type_is_sized(inner_source) {
987 (inner_source, inner_target)
989 scx.tcx().struct_lockstep_tails(inner_source, inner_target)
993 (&ty::TyAdt(source_adt_def, source_substs),
994 &ty::TyAdt(target_adt_def, target_substs)) => {
995 assert_eq!(source_adt_def, target_adt_def);
997 let kind = custom_coerce_unsize_info(scx, source_ty, target_ty);
999 let coerce_index = match kind {
1000 CustomCoerceUnsized::Struct(i) => i
1003 let source_fields = &source_adt_def.struct_variant().fields;
1004 let target_fields = &target_adt_def.struct_variant().fields;
1006 assert!(coerce_index < source_fields.len() &&
1007 source_fields.len() == target_fields.len());
1009 find_vtable_types_for_unsizing(scx,
1010 source_fields[coerce_index].ty(scx.tcx(),
1012 target_fields[coerce_index].ty(scx.tcx(),
1015 _ => bug!("find_vtable_types_for_unsizing: invalid coercion {:?} -> {:?}",
1021 fn create_fn_trans_item<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
1023 fn_substs: &'tcx Substs<'tcx>,
1024 param_substs: &'tcx Substs<'tcx>)
1025 -> TransItem<'tcx> {
1026 let tcx = scx.tcx();
1028 debug!("create_fn_trans_item(def_id={}, fn_substs={:?}, param_substs={:?})",
1029 def_id_to_string(tcx, def_id),
1033 // We only get here, if fn_def_id either designates a local item or
1034 // an inlineable external item. Non-inlineable external items are
1035 // ignored because we don't want to generate any code for them.
1036 let concrete_substs = monomorphize::apply_param_substs(scx,
1039 assert!(concrete_substs.is_normalized_for_trans(),
1040 "concrete_substs not normalized for trans: {:?}",
1042 TransItem::Fn(Instance::new(def_id, concrete_substs))
1045 /// Creates a `TransItem` for each method that is referenced by the vtable for
1046 /// the given trait/impl pair.
1047 fn create_trans_items_for_vtable_methods<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
1048 trait_ty: ty::Ty<'tcx>,
1049 impl_ty: ty::Ty<'tcx>,
1050 output: &mut Vec<TransItem<'tcx>>) {
1051 assert!(!trait_ty.needs_subst() && !impl_ty.needs_subst());
1053 if let ty::TyDynamic(ref trait_ty, ..) = trait_ty.sty {
1054 if let Some(principal) = trait_ty.principal() {
1055 let poly_trait_ref = principal.with_self_ty(scx.tcx(), impl_ty);
1056 let param_substs = scx.tcx().intern_substs(&[]);
1058 // Walk all methods of the trait, including those of its supertraits
1059 let methods = traits::get_vtable_methods(scx.tcx(), poly_trait_ref);
1060 let methods = methods.filter_map(|method| method)
1061 .filter_map(|(def_id, substs)| {
1062 if let StaticDispatchResult::Dispatched {
1065 // We already add the drop-glue for the closure env
1066 // unconditionally below.
1067 fn_once_adjustment: _ ,
1068 } = do_static_dispatch(scx, def_id, substs, param_substs) {
1069 Some((def_id, substs))
1074 .filter(|&(def_id, _)| can_have_local_instance(scx.tcx(), def_id))
1075 .map(|(def_id, substs)| create_fn_trans_item(scx, def_id, substs, param_substs));
1076 output.extend(methods);
1078 // Also add the destructor
1079 let dg_type = glue::get_drop_glue_type(scx, impl_ty);
1080 output.push(TransItem::DropGlue(DropGlueKind::Ty(dg_type)));
1084 //=-----------------------------------------------------------------------------
1086 //=-----------------------------------------------------------------------------
1088 struct RootCollector<'b, 'a: 'b, 'tcx: 'a + 'b> {
1089 scx: &'b SharedCrateContext<'a, 'tcx>,
1090 mode: TransItemCollectionMode,
1091 output: &'b mut Vec<TransItem<'tcx>>,
1094 impl<'b, 'a, 'v> ItemLikeVisitor<'v> for RootCollector<'b, 'a, 'v> {
1095 fn visit_item(&mut self, item: &'v hir::Item) {
1097 hir::ItemExternCrate(..) |
1099 hir::ItemForeignMod(..) |
1101 hir::ItemDefaultImpl(..) |
1102 hir::ItemTrait(..) |
1103 hir::ItemMod(..) => {
1104 // Nothing to do, just keep recursing...
1107 hir::ItemImpl(..) => {
1108 if self.mode == TransItemCollectionMode::Eager {
1109 create_trans_items_for_default_impls(self.scx,
1115 hir::ItemEnum(_, ref generics) |
1116 hir::ItemStruct(_, ref generics) |
1117 hir::ItemUnion(_, ref generics) => {
1118 if !generics.is_parameterized() {
1119 if self.mode == TransItemCollectionMode::Eager {
1120 let def_id = self.scx.tcx().map.local_def_id(item.id);
1121 debug!("RootCollector: ADT drop-glue for {}",
1122 def_id_to_string(self.scx.tcx(), def_id));
1124 let ty = self.scx.tcx().item_type(def_id);
1125 let ty = glue::get_drop_glue_type(self.scx, ty);
1126 self.output.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
1130 hir::ItemStatic(..) => {
1131 debug!("RootCollector: ItemStatic({})",
1132 def_id_to_string(self.scx.tcx(),
1133 self.scx.tcx().map.local_def_id(item.id)));
1134 self.output.push(TransItem::Static(item.id));
1136 hir::ItemConst(..) => {
1137 // const items only generate translation items if they are
1138 // actually used somewhere. Just declaring them is insufficient.
1140 hir::ItemFn(.., ref generics, _) => {
1141 if !generics.is_type_parameterized() {
1142 let def_id = self.scx.tcx().map.local_def_id(item.id);
1144 debug!("RootCollector: ItemFn({})",
1145 def_id_to_string(self.scx.tcx(), def_id));
1147 let instance = Instance::mono(self.scx, def_id);
1148 self.output.push(TransItem::Fn(instance));
1154 fn visit_trait_item(&mut self, _: &'v hir::TraitItem) {
1155 // Even if there's a default body with no explicit generics,
1156 // it's still generic over some `Self: Trait`, so not a root.
1159 fn visit_impl_item(&mut self, ii: &'v hir::ImplItem) {
1161 hir::ImplItemKind::Method(hir::MethodSig {
1165 let hir_map = &self.scx.tcx().map;
1166 let parent_node_id = hir_map.get_parent_node(ii.id);
1167 let is_impl_generic = match hir_map.expect_item(parent_node_id) {
1169 node: hir::ItemImpl(_, _, ref generics, ..),
1172 generics.is_type_parameterized()
1179 if !generics.is_type_parameterized() && !is_impl_generic {
1180 let def_id = self.scx.tcx().map.local_def_id(ii.id);
1182 debug!("RootCollector: MethodImplItem({})",
1183 def_id_to_string(self.scx.tcx(), def_id));
1185 let instance = Instance::mono(self.scx, def_id);
1186 self.output.push(TransItem::Fn(instance));
1189 _ => { /* Nothing to do here */ }
1194 fn create_trans_items_for_default_impls<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
1195 item: &'tcx hir::Item,
1196 output: &mut Vec<TransItem<'tcx>>) {
1197 let tcx = scx.tcx();
1203 ref impl_item_refs) => {
1204 if generics.is_type_parameterized() {
1208 let impl_def_id = tcx.map.local_def_id(item.id);
1210 debug!("create_trans_items_for_default_impls(item={})",
1211 def_id_to_string(tcx, impl_def_id));
1213 if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1214 let callee_substs = tcx.erase_regions(&trait_ref.substs);
1215 let overridden_methods: FxHashSet<_> =
1216 impl_item_refs.iter()
1217 .map(|iiref| iiref.name)
1219 for method in tcx.provided_trait_methods(trait_ref.def_id) {
1220 if overridden_methods.contains(&method.name) {
1224 if !tcx.item_generics(method.def_id).types.is_empty() {
1228 // The substitutions we have are on the impl, so we grab
1229 // the method type from the impl to substitute into.
1230 let impl_substs = Substs::for_item(tcx, impl_def_id,
1231 |_, _| tcx.mk_region(ty::ReErased),
1232 |_, _| tcx.types.err);
1233 let impl_data = traits::VtableImplData {
1234 impl_def_id: impl_def_id,
1235 substs: impl_substs,
1238 let (def_id, substs) = traits::find_method(tcx,
1243 let predicates = tcx.item_predicates(def_id).predicates
1244 .subst(tcx, substs);
1245 if !traits::normalize_and_test_predicates(tcx, predicates) {
1249 if can_have_local_instance(tcx, method.def_id) {
1250 let item = create_fn_trans_item(scx,
1253 tcx.erase_regions(&substs));
1265 /// Scan the MIR in order to find function calls, closures, and drop-glue
1266 fn collect_neighbours<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
1267 instance: Instance<'tcx>,
1268 output: &mut Vec<TransItem<'tcx>>)
1270 let mir = scx.tcx().item_mir(instance.def);
1272 let mut visitor = MirNeighborCollector {
1276 param_substs: instance.substs
1279 visitor.visit_mir(&mir);
1280 for promoted in &mir.promoted {
1281 visitor.visit_mir(promoted);
1285 fn def_id_to_string<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1288 let mut output = String::new();
1289 let printer = DefPathBasedNames::new(tcx, false, false);
1290 printer.push_def_path(def_id, &mut output);
1294 fn type_to_string<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1297 let mut output = String::new();
1298 let printer = DefPathBasedNames::new(tcx, false, false);
1299 printer.push_type_name(ty, &mut output);