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 form 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 context::SharedCrateContext;
207 use common::{def_ty, instance_ty};
208 use glue::{self, DropGlueKind};
209 use monomorphize::{self, Instance};
210 use util::nodemap::{FxHashSet, FxHashMap, DefIdMap};
212 use trans_item::{TransItem, DefPathBasedNames, InstantiationMode};
216 #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
217 pub enum TransItemCollectionMode {
222 /// Maps every translation item to all translation items it references in its
224 pub struct InliningMap<'tcx> {
225 // Maps a source translation item to a range of target translation items
226 // that are potentially inlined by LLVM into the source.
227 // The two numbers in the tuple are the start (inclusive) and
228 // end index (exclusive) within the `targets` vecs.
229 index: FxHashMap<TransItem<'tcx>, (usize, usize)>,
230 targets: Vec<TransItem<'tcx>>,
233 impl<'tcx> InliningMap<'tcx> {
235 fn new() -> InliningMap<'tcx> {
242 fn record_inlining_canditates<I>(&mut self,
243 source: TransItem<'tcx>,
245 where I: Iterator<Item=TransItem<'tcx>>
247 assert!(!self.index.contains_key(&source));
249 let start_index = self.targets.len();
250 self.targets.extend(targets);
251 let end_index = self.targets.len();
252 self.index.insert(source, (start_index, end_index));
255 // Internally iterate over all items referenced by `source` which will be
256 // made available for inlining.
257 pub fn with_inlining_candidates<F>(&self, source: TransItem<'tcx>, mut f: F)
258 where F: FnMut(TransItem<'tcx>) {
259 if let Some(&(start_index, end_index)) = self.index.get(&source)
261 for candidate in &self.targets[start_index .. end_index] {
268 pub fn collect_crate_translation_items<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
269 mode: TransItemCollectionMode)
270 -> (FxHashSet<TransItem<'tcx>>,
272 // We are not tracking dependencies of this pass as it has to be re-executed
273 // every time no matter what.
274 scx.tcx().dep_graph.with_ignore(|| {
275 let roots = collect_roots(scx, mode);
277 debug!("Building translation item graph, beginning at roots");
278 let mut visited = FxHashSet();
279 let mut recursion_depths = DefIdMap();
280 let mut inlining_map = InliningMap::new();
283 collect_items_rec(scx,
286 &mut recursion_depths,
290 (visited, inlining_map)
294 // Find all non-generic items by walking the HIR. These items serve as roots to
295 // start monomorphizing from.
296 fn collect_roots<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
297 mode: TransItemCollectionMode)
298 -> Vec<TransItem<'tcx>> {
299 debug!("Collecting roots");
300 let mut roots = Vec::new();
303 let mut visitor = RootCollector {
309 scx.tcx().hir.krate().visit_all_item_likes(&mut visitor);
315 // Collect all monomorphized translation items reachable from `starting_point`
316 fn collect_items_rec<'a, 'tcx: 'a>(scx: &SharedCrateContext<'a, 'tcx>,
317 starting_point: TransItem<'tcx>,
318 visited: &mut FxHashSet<TransItem<'tcx>>,
319 recursion_depths: &mut DefIdMap<usize>,
320 inlining_map: &mut InliningMap<'tcx>) {
321 if !visited.insert(starting_point.clone()) {
322 // We've been here already, no need to search again.
325 debug!("BEGIN collect_items_rec({})", starting_point.to_string(scx.tcx()));
327 let mut neighbors = Vec::new();
328 let recursion_depth_reset;
330 match starting_point {
331 TransItem::DropGlue(t) => {
332 find_drop_glue_neighbors(scx, t, &mut neighbors);
333 recursion_depth_reset = None;
335 TransItem::Static(node_id) => {
336 let def_id = scx.tcx().hir.local_def_id(node_id);
337 let instance = Instance::mono(scx.tcx(), def_id);
339 // Sanity check whether this ended up being collected accidentally
340 debug_assert!(should_trans_locally(scx.tcx(), &instance));
342 let ty = instance_ty(scx, &instance);
343 let ty = glue::get_drop_glue_type(scx, ty);
344 neighbors.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
346 recursion_depth_reset = None;
348 collect_neighbours(scx, instance, &mut neighbors);
350 TransItem::Fn(instance) => {
351 // Sanity check whether this ended up being collected accidentally
352 debug_assert!(should_trans_locally(scx.tcx(), &instance));
354 // Keep track of the monomorphization recursion depth
355 recursion_depth_reset = Some(check_recursion_limit(scx.tcx(),
358 check_type_length_limit(scx.tcx(), instance);
360 collect_neighbours(scx, instance, &mut neighbors);
364 record_inlining_canditates(scx.tcx(), starting_point, &neighbors[..], inlining_map);
366 for neighbour in neighbors {
367 collect_items_rec(scx, neighbour, visited, recursion_depths, inlining_map);
370 if let Some((def_id, depth)) = recursion_depth_reset {
371 recursion_depths.insert(def_id, depth);
374 debug!("END collect_items_rec({})", starting_point.to_string(scx.tcx()));
377 fn record_inlining_canditates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
378 caller: TransItem<'tcx>,
379 callees: &[TransItem<'tcx>],
380 inlining_map: &mut InliningMap<'tcx>) {
381 let is_inlining_candidate = |trans_item: &TransItem<'tcx>| {
382 trans_item.instantiation_mode(tcx) == InstantiationMode::LocalCopy
385 let inlining_candidates = callees.into_iter()
387 .filter(is_inlining_candidate);
389 inlining_map.record_inlining_canditates(caller, inlining_candidates);
392 fn check_recursion_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
393 instance: Instance<'tcx>,
394 recursion_depths: &mut DefIdMap<usize>)
396 let def_id = instance.def_id();
397 let recursion_depth = recursion_depths.get(&def_id).cloned().unwrap_or(0);
398 debug!(" => recursion depth={}", recursion_depth);
400 // Code that needs to instantiate the same function recursively
401 // more than the recursion limit is assumed to be causing an
402 // infinite expansion.
403 if recursion_depth > tcx.sess.recursion_limit.get() {
404 let error = format!("reached the recursion limit while instantiating `{}`",
406 if let Some(node_id) = tcx.hir.as_local_node_id(def_id) {
407 tcx.sess.span_fatal(tcx.hir.span(node_id), &error);
409 tcx.sess.fatal(&error);
413 recursion_depths.insert(def_id, recursion_depth + 1);
415 (def_id, recursion_depth)
418 fn check_type_length_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
419 instance: Instance<'tcx>)
421 let type_length = instance.substs.types().flat_map(|ty| ty.walk()).count();
422 debug!(" => type length={}", type_length);
424 // Rust code can easily create exponentially-long types using only a
425 // polynomial recursion depth. Even with the default recursion
426 // depth, you can easily get cases that take >2^60 steps to run,
427 // which means that rustc basically hangs.
429 // Bail out in these cases to avoid that bad user experience.
430 let type_length_limit = tcx.sess.type_length_limit.get();
431 if type_length > type_length_limit {
432 // The instance name is already known to be too long for rustc. Use
433 // `{:.64}` to avoid blasting the user's terminal with thousands of
434 // lines of type-name.
435 let instance_name = instance.to_string();
436 let msg = format!("reached the type-length limit while instantiating `{:.64}...`",
438 let mut diag = if let Some(node_id) = tcx.hir.as_local_node_id(instance.def_id()) {
439 tcx.sess.struct_span_fatal(tcx.hir.span(node_id), &msg)
441 tcx.sess.struct_fatal(&msg)
445 "consider adding a `#![type_length_limit=\"{}\"]` attribute to your crate",
446 type_length_limit*2));
448 tcx.sess.abort_if_errors();
452 struct MirNeighborCollector<'a, 'tcx: 'a> {
453 scx: &'a SharedCrateContext<'a, 'tcx>,
454 mir: &'a mir::Mir<'tcx>,
455 output: &'a mut Vec<TransItem<'tcx>>,
456 param_substs: &'tcx Substs<'tcx>
459 impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
461 fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: Location) {
462 debug!("visiting rvalue {:?}", *rvalue);
465 // When doing an cast from a regular pointer to a fat pointer, we
466 // have to instantiate all methods of the trait being cast to, so we
467 // can build the appropriate vtable.
468 mir::Rvalue::Cast(mir::CastKind::Unsize, ref operand, target_ty) => {
469 let target_ty = monomorphize::apply_param_substs(self.scx,
472 let source_ty = operand.ty(self.mir, self.scx.tcx());
473 let source_ty = monomorphize::apply_param_substs(self.scx,
476 let (source_ty, target_ty) = find_vtable_types_for_unsizing(self.scx,
479 // This could also be a different Unsize instruction, like
480 // from a fixed sized array to a slice. But we are only
481 // interested in things that produce a vtable.
482 if target_ty.is_trait() && !source_ty.is_trait() {
483 create_trans_items_for_vtable_methods(self.scx,
489 mir::Rvalue::Cast(mir::CastKind::ClosureFnPointer, ref operand, _) => {
490 let source_ty = operand.ty(self.mir, self.scx.tcx());
491 match source_ty.sty {
492 ty::TyClosure(def_id, substs) => {
493 let substs = monomorphize::apply_param_substs(
494 self.scx, self.param_substs, &substs.substs);
495 self.output.push(create_fn_trans_item(
496 Instance::new(def_id, substs)
502 mir::Rvalue::Box(..) => {
503 let tcx = self.scx.tcx();
504 let exchange_malloc_fn_def_id = tcx
506 .require(ExchangeMallocFnLangItem)
507 .unwrap_or_else(|e| self.scx.sess().fatal(&e));
508 let instance = Instance::mono(tcx, exchange_malloc_fn_def_id);
509 if should_trans_locally(tcx, &instance) {
510 self.output.push(create_fn_trans_item(instance));
513 _ => { /* not interesting */ }
516 self.super_rvalue(rvalue, location);
519 fn visit_lvalue(&mut self,
520 lvalue: &mir::Lvalue<'tcx>,
521 context: mir_visit::LvalueContext<'tcx>,
522 location: Location) {
523 debug!("visiting lvalue {:?}", *lvalue);
525 if let mir_visit::LvalueContext::Drop = context {
526 let ty = lvalue.ty(self.mir, self.scx.tcx())
527 .to_ty(self.scx.tcx());
529 let ty = monomorphize::apply_param_substs(self.scx,
532 assert!(ty.is_normalized_for_trans());
533 let ty = glue::get_drop_glue_type(self.scx, ty);
534 self.output.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
537 self.super_lvalue(lvalue, context, location);
540 fn visit_operand(&mut self, operand: &mir::Operand<'tcx>, location: Location) {
541 debug!("visiting operand {:?}", *operand);
543 let callee = match *operand {
544 mir::Operand::Constant(ref constant) => {
545 if let ty::TyFnDef(def_id, substs, _) = constant.ty.sty {
546 // This is something that can act as a callee, proceed
547 Some((def_id, substs))
549 // This is not a callee, but we still have to look for
550 // references to `const` items
551 if let mir::Literal::Item { def_id, substs } = constant.literal {
552 let substs = monomorphize::apply_param_substs(self.scx,
555 let instance = monomorphize::resolve(self.scx, def_id, substs);
556 collect_neighbours(self.scx, instance, self.output);
565 if let Some((callee_def_id, callee_substs)) = callee {
566 debug!(" => operand is callable");
568 // `callee_def_id` might refer to a trait method instead of a
569 // concrete implementation, so we have to find the actual
570 // implementation. For example, the call might look like
572 // std::cmp::partial_cmp(0i32, 1i32)
574 // Calling do_static_dispatch() here will map the def_id of
575 // `std::cmp::partial_cmp` to the def_id of `i32::partial_cmp<i32>`
577 let callee_substs = monomorphize::apply_param_substs(self.scx,
581 monomorphize::resolve(self.scx, callee_def_id, callee_substs);
582 if should_trans_locally(self.scx.tcx(), &instance) {
583 if let ty::InstanceDef::ClosureOnceShim { .. } = instance.def {
584 // This call will instantiate an FnOnce adapter, which
585 // drops the closure environment. Therefore we need to
586 // make sure that we collect the drop-glue for the
589 let env_ty = instance.substs.type_at(0);
590 let env_ty = glue::get_drop_glue_type(self.scx, env_ty);
591 if self.scx.type_needs_drop(env_ty) {
592 let dg = DropGlueKind::Ty(env_ty);
593 self.output.push(TransItem::DropGlue(dg));
596 self.output.push(create_fn_trans_item(instance));
600 self.super_operand(operand, location);
603 // This takes care of the "drop_in_place" intrinsic for which we otherwise
604 // we would not register drop-glues.
605 fn visit_terminator_kind(&mut self,
606 block: mir::BasicBlock,
607 kind: &mir::TerminatorKind<'tcx>,
608 location: Location) {
609 let tcx = self.scx.tcx();
611 mir::TerminatorKind::Call {
612 func: mir::Operand::Constant(ref constant),
616 match constant.ty.sty {
617 ty::TyFnDef(def_id, _, bare_fn_ty)
618 if is_drop_in_place_intrinsic(tcx, def_id, bare_fn_ty) => {
619 let operand_ty = args[0].ty(self.mir, tcx);
620 if let ty::TyRawPtr(mt) = operand_ty.sty {
621 let operand_ty = monomorphize::apply_param_substs(self.scx,
624 let ty = glue::get_drop_glue_type(self.scx, operand_ty);
625 self.output.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
627 bug!("Has the drop_in_place() intrinsic's signature changed?")
630 _ => { /* Nothing to do. */ }
633 _ => { /* Nothing to do. */ }
636 self.super_terminator_kind(block, kind, location);
638 fn is_drop_in_place_intrinsic<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
640 bare_fn_ty: ty::PolyFnSig<'tcx>)
642 (bare_fn_ty.abi() == Abi::RustIntrinsic ||
643 bare_fn_ty.abi() == Abi::PlatformIntrinsic) &&
644 tcx.item_name(def_id) == "drop_in_place"
649 // Returns true if we should translate an instance in the local crate.
650 // Returns false if we can just link to the upstream crate and therefore don't
651 // need a translation item.
652 fn should_trans_locally<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, instance: &Instance<'tcx>)
654 let def_id = match instance.def {
655 ty::InstanceDef::Item(def_id) |
656 ty::InstanceDef::ClosureOnceShim {
657 call_once: _, closure_did: def_id
659 ty::InstanceDef::FnPtrShim(..) => return true,
660 ty::InstanceDef::Virtual(..) |
661 ty::InstanceDef::Intrinsic(_) => return false
663 match tcx.hir.get_if_local(def_id) {
664 Some(hir_map::NodeForeignItem(..)) => {
665 false // foreign items are linked against, not translated.
669 if tcx.sess.cstore.is_exported_symbol(def_id) ||
670 tcx.sess.cstore.is_foreign_item(def_id)
672 // We can link to the item in question, no instance needed
676 if !tcx.sess.cstore.is_item_mir_available(def_id) {
677 bug!("Cannot create local trans-item for {:?}", def_id)
685 fn find_drop_glue_neighbors<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
686 dg: DropGlueKind<'tcx>,
687 output: &mut Vec<TransItem<'tcx>>) {
689 DropGlueKind::Ty(ty) => ty,
690 DropGlueKind::TyContents(_) => {
691 // We already collected the neighbors of this item via the
692 // DropGlueKind::Ty variant.
697 debug!("find_drop_glue_neighbors: {}", type_to_string(scx.tcx(), ty));
699 // Make sure the BoxFreeFn lang-item gets translated if there is a boxed value.
702 let def_id = tcx.require_lang_item(BoxFreeFnLangItem);
703 let box_free_instance = Instance::new(
705 tcx.mk_substs(iter::once(Kind::from(ty.boxed_ty())))
707 if should_trans_locally(tcx, &box_free_instance) {
708 output.push(create_fn_trans_item(box_free_instance));
712 // If the type implements Drop, also add a translation item for the
713 // monomorphized Drop::drop() implementation.
714 let has_dtor = match ty.sty {
715 ty::TyAdt(def, _) => def.has_dtor(scx.tcx()),
719 if has_dtor && !ty.is_box() {
720 let drop_trait_def_id = scx.tcx()
724 let drop_method = scx.tcx().associated_items(drop_trait_def_id)
725 .find(|it| it.kind == ty::AssociatedKind::Method)
727 let substs = scx.tcx().mk_substs_trait(ty, &[]);
728 let instance = monomorphize::resolve(scx, drop_method, substs);
729 if should_trans_locally(scx.tcx(), &instance) {
730 output.push(create_fn_trans_item(instance));
733 // This type has a Drop implementation, we'll need the contents-only
734 // version of the glue too.
735 output.push(TransItem::DropGlue(DropGlueKind::TyContents(ty)));
738 // Finally add the types of nested values
751 ty::TyDynamic(..) => {
754 ty::TyAdt(def, _) if def.is_box() => {
755 let inner_type = glue::get_drop_glue_type(scx, ty.boxed_ty());
756 if scx.type_needs_drop(inner_type) {
757 output.push(TransItem::DropGlue(DropGlueKind::Ty(inner_type)));
760 ty::TyAdt(def, substs) => {
761 for field in def.all_fields() {
762 let field_type = def_ty(scx, field.did, substs);
763 let field_type = glue::get_drop_glue_type(scx, field_type);
765 if scx.type_needs_drop(field_type) {
766 output.push(TransItem::DropGlue(DropGlueKind::Ty(field_type)));
770 ty::TyClosure(def_id, substs) => {
771 for upvar_ty in substs.upvar_tys(def_id, scx.tcx()) {
772 let upvar_ty = glue::get_drop_glue_type(scx, upvar_ty);
773 if scx.type_needs_drop(upvar_ty) {
774 output.push(TransItem::DropGlue(DropGlueKind::Ty(upvar_ty)));
778 ty::TySlice(inner_type) |
779 ty::TyArray(inner_type, _) => {
780 let inner_type = glue::get_drop_glue_type(scx, inner_type);
781 if scx.type_needs_drop(inner_type) {
782 output.push(TransItem::DropGlue(DropGlueKind::Ty(inner_type)));
785 ty::TyTuple(args, _) => {
787 let arg = glue::get_drop_glue_type(scx, arg);
788 if scx.type_needs_drop(arg) {
789 output.push(TransItem::DropGlue(DropGlueKind::Ty(arg)));
793 ty::TyProjection(_) |
798 bug!("encountered unexpected type");
803 /// For given pair of source and target type that occur in an unsizing coercion,
804 /// this function finds the pair of types that determines the vtable linking
807 /// For example, the source type might be `&SomeStruct` and the target type\
808 /// might be `&SomeTrait` in a cast like:
810 /// let src: &SomeStruct = ...;
811 /// let target = src as &SomeTrait;
813 /// Then the output of this function would be (SomeStruct, SomeTrait) since for
814 /// constructing the `target` fat-pointer we need the vtable for that pair.
816 /// Things can get more complicated though because there's also the case where
817 /// the unsized type occurs as a field:
820 /// struct ComplexStruct<T: ?Sized> {
827 /// In this case, if `T` is sized, `&ComplexStruct<T>` is a thin pointer. If `T`
828 /// is unsized, `&SomeStruct` is a fat pointer, and the vtable it points to is
829 /// for the pair of `T` (which is a trait) and the concrete type that `T` was
830 /// originally coerced from:
832 /// let src: &ComplexStruct<SomeStruct> = ...;
833 /// let target = src as &ComplexStruct<SomeTrait>;
835 /// Again, we want this `find_vtable_types_for_unsizing()` to provide the pair
836 /// `(SomeStruct, SomeTrait)`.
838 /// Finally, there is also the case of custom unsizing coercions, e.g. for
839 /// smart pointers such as `Rc` and `Arc`.
840 fn find_vtable_types_for_unsizing<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
841 source_ty: ty::Ty<'tcx>,
842 target_ty: ty::Ty<'tcx>)
843 -> (ty::Ty<'tcx>, ty::Ty<'tcx>) {
844 let ptr_vtable = |inner_source: ty::Ty<'tcx>, inner_target: ty::Ty<'tcx>| {
845 if !scx.type_is_sized(inner_source) {
846 (inner_source, inner_target)
848 scx.tcx().struct_lockstep_tails(inner_source, inner_target)
851 match (&source_ty.sty, &target_ty.sty) {
852 (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
853 &ty::TyRef(_, ty::TypeAndMut { ty: b, .. })) |
854 (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
855 &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) |
856 (&ty::TyRawPtr(ty::TypeAndMut { ty: a, .. }),
857 &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) => {
860 (&ty::TyAdt(def_a, _), &ty::TyAdt(def_b, _)) if def_a.is_box() && def_b.is_box() => {
861 ptr_vtable(source_ty.boxed_ty(), target_ty.boxed_ty())
864 (&ty::TyAdt(source_adt_def, source_substs),
865 &ty::TyAdt(target_adt_def, target_substs)) => {
866 assert_eq!(source_adt_def, target_adt_def);
869 monomorphize::custom_coerce_unsize_info(scx, source_ty, target_ty);
871 let coerce_index = match kind {
872 CustomCoerceUnsized::Struct(i) => i
875 let source_fields = &source_adt_def.struct_variant().fields;
876 let target_fields = &target_adt_def.struct_variant().fields;
878 assert!(coerce_index < source_fields.len() &&
879 source_fields.len() == target_fields.len());
881 find_vtable_types_for_unsizing(scx,
882 source_fields[coerce_index].ty(scx.tcx(),
884 target_fields[coerce_index].ty(scx.tcx(),
887 _ => bug!("find_vtable_types_for_unsizing: invalid coercion {:?} -> {:?}",
893 fn create_fn_trans_item<'a, 'tcx>(instance: Instance<'tcx>) -> TransItem<'tcx> {
894 debug!("create_fn_trans_item(instance={})", instance);
895 let instance = match instance.def {
896 ty::InstanceDef::ClosureOnceShim { .. } => {
897 // HACK: don't create ClosureOnce trans items for now
898 // have someone else generate the drop glue
899 let closure_ty = instance.substs.type_at(0);
900 match closure_ty.sty {
901 ty::TyClosure(def_id, substs) => {
902 Instance::new(def_id, substs.substs)
904 _ => bug!("bad closure instance {:?}", instance)
909 TransItem::Fn(instance)
912 /// Creates a `TransItem` for each method that is referenced by the vtable for
913 /// the given trait/impl pair.
914 fn create_trans_items_for_vtable_methods<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
915 trait_ty: ty::Ty<'tcx>,
916 impl_ty: ty::Ty<'tcx>,
917 output: &mut Vec<TransItem<'tcx>>) {
918 assert!(!trait_ty.needs_subst() && !trait_ty.has_escaping_regions() &&
919 !impl_ty.needs_subst() && !impl_ty.has_escaping_regions());
921 if let ty::TyDynamic(ref trait_ty, ..) = trait_ty.sty {
922 if let Some(principal) = trait_ty.principal() {
923 let poly_trait_ref = principal.with_self_ty(scx.tcx(), impl_ty);
924 assert!(!poly_trait_ref.has_escaping_regions());
926 // Walk all methods of the trait, including those of its supertraits
927 let methods = traits::get_vtable_methods(scx.tcx(), poly_trait_ref);
928 let methods = methods.filter_map(|method| method)
929 .map(|(def_id, substs)| monomorphize::resolve(scx, def_id, substs))
930 .filter(|&instance| should_trans_locally(scx.tcx(), &instance))
931 .map(|instance| create_fn_trans_item(instance));
932 output.extend(methods);
934 // Also add the destructor
935 let dg_type = glue::get_drop_glue_type(scx, impl_ty);
936 output.push(TransItem::DropGlue(DropGlueKind::Ty(dg_type)));
940 //=-----------------------------------------------------------------------------
942 //=-----------------------------------------------------------------------------
944 struct RootCollector<'b, 'a: 'b, 'tcx: 'a + 'b> {
945 scx: &'b SharedCrateContext<'a, 'tcx>,
946 mode: TransItemCollectionMode,
947 output: &'b mut Vec<TransItem<'tcx>>,
950 impl<'b, 'a, 'v> ItemLikeVisitor<'v> for RootCollector<'b, 'a, 'v> {
951 fn visit_item(&mut self, item: &'v hir::Item) {
953 hir::ItemExternCrate(..) |
955 hir::ItemForeignMod(..) |
957 hir::ItemDefaultImpl(..) |
959 hir::ItemMod(..) => {
960 // Nothing to do, just keep recursing...
963 hir::ItemImpl(..) => {
964 if self.mode == TransItemCollectionMode::Eager {
965 create_trans_items_for_default_impls(self.scx,
971 hir::ItemEnum(_, ref generics) |
972 hir::ItemStruct(_, ref generics) |
973 hir::ItemUnion(_, ref generics) => {
974 if !generics.is_parameterized() {
975 if self.mode == TransItemCollectionMode::Eager {
976 let def_id = self.scx.tcx().hir.local_def_id(item.id);
977 debug!("RootCollector: ADT drop-glue for {}",
978 def_id_to_string(self.scx.tcx(), def_id));
980 let ty = def_ty(self.scx, def_id, Substs::empty());
981 let ty = glue::get_drop_glue_type(self.scx, ty);
982 self.output.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
986 hir::ItemStatic(..) => {
987 debug!("RootCollector: ItemStatic({})",
988 def_id_to_string(self.scx.tcx(),
989 self.scx.tcx().hir.local_def_id(item.id)));
990 self.output.push(TransItem::Static(item.id));
992 hir::ItemConst(..) => {
993 // const items only generate translation items if they are
994 // actually used somewhere. Just declaring them is insufficient.
996 hir::ItemFn(.., ref generics, _) => {
997 if !generics.is_type_parameterized() {
998 let def_id = self.scx.tcx().hir.local_def_id(item.id);
1000 debug!("RootCollector: ItemFn({})",
1001 def_id_to_string(self.scx.tcx(), def_id));
1003 let instance = Instance::mono(self.scx.tcx(), def_id);
1004 self.output.push(TransItem::Fn(instance));
1010 fn visit_trait_item(&mut self, _: &'v hir::TraitItem) {
1011 // Even if there's a default body with no explicit generics,
1012 // it's still generic over some `Self: Trait`, so not a root.
1015 fn visit_impl_item(&mut self, ii: &'v hir::ImplItem) {
1017 hir::ImplItemKind::Method(hir::MethodSig {
1021 let hir_map = &self.scx.tcx().hir;
1022 let parent_node_id = hir_map.get_parent_node(ii.id);
1023 let is_impl_generic = match hir_map.expect_item(parent_node_id) {
1025 node: hir::ItemImpl(_, _, ref generics, ..),
1028 generics.is_type_parameterized()
1035 if !generics.is_type_parameterized() && !is_impl_generic {
1036 let def_id = self.scx.tcx().hir.local_def_id(ii.id);
1038 debug!("RootCollector: MethodImplItem({})",
1039 def_id_to_string(self.scx.tcx(), def_id));
1041 let instance = Instance::mono(self.scx.tcx(), def_id);
1042 self.output.push(TransItem::Fn(instance));
1045 _ => { /* Nothing to do here */ }
1050 fn create_trans_items_for_default_impls<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
1051 item: &'tcx hir::Item,
1052 output: &mut Vec<TransItem<'tcx>>) {
1053 let tcx = scx.tcx();
1059 ref impl_item_refs) => {
1060 if generics.is_type_parameterized() {
1064 let impl_def_id = tcx.hir.local_def_id(item.id);
1066 debug!("create_trans_items_for_default_impls(item={})",
1067 def_id_to_string(tcx, impl_def_id));
1069 if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1070 let callee_substs = tcx.erase_regions(&trait_ref.substs);
1071 let overridden_methods: FxHashSet<_> =
1072 impl_item_refs.iter()
1073 .map(|iiref| iiref.name)
1075 for method in tcx.provided_trait_methods(trait_ref.def_id) {
1076 if overridden_methods.contains(&method.name) {
1080 if !tcx.item_generics(method.def_id).types.is_empty() {
1085 monomorphize::resolve(scx, method.def_id, callee_substs);
1087 let predicates = tcx.item_predicates(instance.def_id()).predicates
1088 .subst(tcx, instance.substs);
1089 if !traits::normalize_and_test_predicates(tcx, predicates) {
1093 if should_trans_locally(tcx, &instance) {
1094 output.push(create_fn_trans_item(instance));
1105 /// Scan the MIR in order to find function calls, closures, and drop-glue
1106 fn collect_neighbours<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
1107 instance: Instance<'tcx>,
1108 output: &mut Vec<TransItem<'tcx>>)
1110 let mir = scx.tcx().instance_mir(instance.def);
1112 let mut visitor = MirNeighborCollector {
1116 param_substs: instance.substs
1119 visitor.visit_mir(&mir);
1120 for promoted in &mir.promoted {
1121 visitor.mir = promoted;
1122 visitor.visit_mir(promoted);
1126 fn def_id_to_string<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1129 let mut output = String::new();
1130 let printer = DefPathBasedNames::new(tcx, false, false);
1131 printer.push_def_path(def_id, &mut output);
1135 fn type_to_string<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1138 let mut output = String::new();
1139 let printer = DefPathBasedNames::new(tcx, false, false);
1140 printer.push_type_name(ty, &mut output);