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 context::SharedCrateContext;
206 use common::{def_ty, instance_ty};
207 use glue::{self, DropGlueKind};
208 use monomorphize::{self, Instance};
209 use util::nodemap::{FxHashSet, FxHashMap, DefIdMap};
211 use trans_item::{TransItem, DefPathBasedNames, InstantiationMode};
215 #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
216 pub enum TransItemCollectionMode {
221 /// Maps every translation item to all translation items it references in its
223 pub struct InliningMap<'tcx> {
224 // Maps a source translation item to a range of target translation items
225 // that are potentially inlined by LLVM into the source.
226 // The two numbers in the tuple are the start (inclusive) and
227 // end index (exclusive) within the `targets` vecs.
228 index: FxHashMap<TransItem<'tcx>, (usize, usize)>,
229 targets: Vec<TransItem<'tcx>>,
232 impl<'tcx> InliningMap<'tcx> {
234 fn new() -> InliningMap<'tcx> {
241 fn record_inlining_canditates<I>(&mut self,
242 source: TransItem<'tcx>,
244 where I: Iterator<Item=TransItem<'tcx>>
246 assert!(!self.index.contains_key(&source));
248 let start_index = self.targets.len();
249 self.targets.extend(targets);
250 let end_index = self.targets.len();
251 self.index.insert(source, (start_index, end_index));
254 // Internally iterate over all items referenced by `source` which will be
255 // made available for inlining.
256 pub fn with_inlining_candidates<F>(&self, source: TransItem<'tcx>, mut f: F)
257 where F: FnMut(TransItem<'tcx>) {
258 if let Some(&(start_index, end_index)) = self.index.get(&source)
260 for candidate in &self.targets[start_index .. end_index] {
267 pub fn collect_crate_translation_items<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
268 mode: TransItemCollectionMode)
269 -> (FxHashSet<TransItem<'tcx>>,
271 // We are not tracking dependencies of this pass as it has to be re-executed
272 // every time no matter what.
273 scx.tcx().dep_graph.with_ignore(|| {
274 let roots = collect_roots(scx, mode);
276 debug!("Building translation item graph, beginning at roots");
277 let mut visited = FxHashSet();
278 let mut recursion_depths = DefIdMap();
279 let mut inlining_map = InliningMap::new();
282 collect_items_rec(scx,
285 &mut recursion_depths,
289 (visited, inlining_map)
293 // Find all non-generic items by walking the HIR. These items serve as roots to
294 // start monomorphizing from.
295 fn collect_roots<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
296 mode: TransItemCollectionMode)
297 -> Vec<TransItem<'tcx>> {
298 debug!("Collecting roots");
299 let mut roots = Vec::new();
302 let mut visitor = RootCollector {
308 scx.tcx().hir.krate().visit_all_item_likes(&mut visitor);
314 // Collect all monomorphized translation items reachable from `starting_point`
315 fn collect_items_rec<'a, 'tcx: 'a>(scx: &SharedCrateContext<'a, 'tcx>,
316 starting_point: TransItem<'tcx>,
317 visited: &mut FxHashSet<TransItem<'tcx>>,
318 recursion_depths: &mut DefIdMap<usize>,
319 inlining_map: &mut InliningMap<'tcx>) {
320 if !visited.insert(starting_point.clone()) {
321 // We've been here already, no need to search again.
324 debug!("BEGIN collect_items_rec({})", starting_point.to_string(scx.tcx()));
326 let mut neighbors = Vec::new();
327 let recursion_depth_reset;
329 match starting_point {
330 TransItem::DropGlue(t) => {
331 find_drop_glue_neighbors(scx, t, &mut neighbors);
332 recursion_depth_reset = None;
334 TransItem::Static(node_id) => {
335 let def_id = scx.tcx().hir.local_def_id(node_id);
336 let instance = Instance::mono(scx.tcx(), def_id);
338 // Sanity check whether this ended up being collected accidentally
339 debug_assert!(should_trans_locally(scx.tcx(), &instance));
341 let ty = instance_ty(scx, &instance);
342 let ty = glue::get_drop_glue_type(scx, ty);
343 neighbors.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
345 recursion_depth_reset = None;
347 collect_neighbours(scx, instance, &mut neighbors);
349 TransItem::Fn(instance) => {
350 // Sanity check whether this ended up being collected accidentally
351 debug_assert!(should_trans_locally(scx.tcx(), &instance));
353 // Keep track of the monomorphization recursion depth
354 recursion_depth_reset = Some(check_recursion_limit(scx.tcx(),
357 check_type_length_limit(scx.tcx(), instance);
359 collect_neighbours(scx, instance, &mut neighbors);
363 record_inlining_canditates(scx.tcx(), starting_point, &neighbors[..], inlining_map);
365 for neighbour in neighbors {
366 collect_items_rec(scx, neighbour, visited, recursion_depths, inlining_map);
369 if let Some((def_id, depth)) = recursion_depth_reset {
370 recursion_depths.insert(def_id, depth);
373 debug!("END collect_items_rec({})", starting_point.to_string(scx.tcx()));
376 fn record_inlining_canditates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
377 caller: TransItem<'tcx>,
378 callees: &[TransItem<'tcx>],
379 inlining_map: &mut InliningMap<'tcx>) {
380 let is_inlining_candidate = |trans_item: &TransItem<'tcx>| {
381 trans_item.instantiation_mode(tcx) == InstantiationMode::LocalCopy
384 let inlining_candidates = callees.into_iter()
386 .filter(is_inlining_candidate);
388 inlining_map.record_inlining_canditates(caller, inlining_candidates);
391 fn check_recursion_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
392 instance: Instance<'tcx>,
393 recursion_depths: &mut DefIdMap<usize>)
395 let def_id = instance.def_id();
396 let recursion_depth = recursion_depths.get(&def_id).cloned().unwrap_or(0);
397 debug!(" => recursion depth={}", recursion_depth);
399 // Code that needs to instantiate the same function recursively
400 // more than the recursion limit is assumed to be causing an
401 // infinite expansion.
402 if recursion_depth > tcx.sess.recursion_limit.get() {
403 let error = format!("reached the recursion limit while instantiating `{}`",
405 if let Some(node_id) = tcx.hir.as_local_node_id(def_id) {
406 tcx.sess.span_fatal(tcx.hir.span(node_id), &error);
408 tcx.sess.fatal(&error);
412 recursion_depths.insert(def_id, recursion_depth + 1);
414 (def_id, recursion_depth)
417 fn check_type_length_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
418 instance: Instance<'tcx>)
420 let type_length = instance.substs.types().flat_map(|ty| ty.walk()).count();
421 debug!(" => type length={}", type_length);
423 // Rust code can easily create exponentially-long types using only a
424 // polynomial recursion depth. Even with the default recursion
425 // depth, you can easily get cases that take >2^60 steps to run,
426 // which means that rustc basically hangs.
428 // Bail out in these cases to avoid that bad user experience.
429 let type_length_limit = tcx.sess.type_length_limit.get();
430 if type_length > type_length_limit {
431 // The instance name is already known to be too long for rustc. Use
432 // `{:.64}` to avoid blasting the user's terminal with thousands of
433 // lines of type-name.
434 let instance_name = instance.to_string();
435 let msg = format!("reached the type-length limit while instantiating `{:.64}...`",
437 let mut diag = if let Some(node_id) = tcx.hir.as_local_node_id(instance.def_id()) {
438 tcx.sess.struct_span_fatal(tcx.hir.span(node_id), &msg)
440 tcx.sess.struct_fatal(&msg)
444 "consider adding a `#![type_length_limit=\"{}\"]` attribute to your crate",
445 type_length_limit*2));
447 tcx.sess.abort_if_errors();
451 struct MirNeighborCollector<'a, 'tcx: 'a> {
452 scx: &'a SharedCrateContext<'a, 'tcx>,
453 mir: &'a mir::Mir<'tcx>,
454 output: &'a mut Vec<TransItem<'tcx>>,
455 param_substs: &'tcx Substs<'tcx>
458 impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
460 fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: Location) {
461 debug!("visiting rvalue {:?}", *rvalue);
464 // When doing an cast from a regular pointer to a fat pointer, we
465 // have to instantiate all methods of the trait being cast to, so we
466 // can build the appropriate vtable.
467 mir::Rvalue::Cast(mir::CastKind::Unsize, ref operand, target_ty) => {
468 let target_ty = monomorphize::apply_param_substs(self.scx,
471 let source_ty = operand.ty(self.mir, self.scx.tcx());
472 let source_ty = monomorphize::apply_param_substs(self.scx,
475 let (source_ty, target_ty) = find_vtable_types_for_unsizing(self.scx,
478 // This could also be a different Unsize instruction, like
479 // from a fixed sized array to a slice. But we are only
480 // interested in things that produce a vtable.
481 if target_ty.is_trait() && !source_ty.is_trait() {
482 create_trans_items_for_vtable_methods(self.scx,
488 mir::Rvalue::Cast(mir::CastKind::ReifyFnPointer, ref operand, _) => {
489 let fn_ty = operand.ty(self.mir, self.scx.tcx());
490 let fn_ty = monomorphize::apply_param_substs(
494 visit_fn_use(self.scx, fn_ty, false, &mut self.output);
496 mir::Rvalue::Cast(mir::CastKind::ClosureFnPointer, ref operand, _) => {
497 let source_ty = operand.ty(self.mir, self.scx.tcx());
498 match source_ty.sty {
499 ty::TyClosure(def_id, substs) => {
500 let instance = monomorphize::resolve_closure(
501 self.scx, def_id, substs, ty::ClosureKind::FnOnce);
502 self.output.push(create_fn_trans_item(instance));
507 mir::Rvalue::Box(..) => {
508 let tcx = self.scx.tcx();
509 let exchange_malloc_fn_def_id = tcx
511 .require(ExchangeMallocFnLangItem)
512 .unwrap_or_else(|e| self.scx.sess().fatal(&e));
513 let instance = Instance::mono(tcx, exchange_malloc_fn_def_id);
514 if should_trans_locally(tcx, &instance) {
515 self.output.push(create_fn_trans_item(instance));
518 _ => { /* not interesting */ }
521 self.super_rvalue(rvalue, location);
524 fn visit_lvalue(&mut self,
525 lvalue: &mir::Lvalue<'tcx>,
526 context: mir_visit::LvalueContext<'tcx>,
527 location: Location) {
528 debug!("visiting lvalue {:?}", *lvalue);
530 if let mir_visit::LvalueContext::Drop = context {
531 let ty = lvalue.ty(self.mir, self.scx.tcx())
532 .to_ty(self.scx.tcx());
534 let ty = monomorphize::apply_param_substs(self.scx,
537 assert!(ty.is_normalized_for_trans());
538 let ty = glue::get_drop_glue_type(self.scx, ty);
539 self.output.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
542 self.super_lvalue(lvalue, context, location);
545 fn visit_constant(&mut self, constant: &mir::Constant<'tcx>, location: Location) {
546 debug!("visiting constant {:?} @ {:?}", *constant, location);
548 if let ty::TyFnDef(..) = constant.ty.sty {
549 // function definitions are zero-sized, and only generate
550 // IR when they are called/reified.
551 self.super_constant(constant, location);
555 if let mir::Literal::Item { def_id, substs } = constant.literal {
556 let substs = monomorphize::apply_param_substs(self.scx,
559 let instance = monomorphize::resolve(self.scx, def_id, substs);
560 collect_neighbours(self.scx, instance, self.output);
563 self.super_constant(constant, location);
566 fn visit_terminator_kind(&mut self,
567 block: mir::BasicBlock,
568 kind: &mir::TerminatorKind<'tcx>,
569 location: Location) {
570 let tcx = self.scx.tcx();
571 if let mir::TerminatorKind::Call {
575 let callee_ty = func.ty(self.mir, tcx);
576 let callee_ty = monomorphize::apply_param_substs(
577 self.scx, self.param_substs, &callee_ty);
578 visit_fn_use(self.scx, callee_ty, true, &mut self.output);
581 self.super_terminator_kind(block, kind, location);
585 fn visit_fn_use<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
587 is_direct_call: bool,
588 output: &mut Vec<TransItem<'tcx>>)
590 debug!("visit_fn_use({:?}, is_direct_call={:?})", ty, is_direct_call);
591 let (def_id, substs) = match ty.sty {
592 ty::TyFnDef(def_id, substs, _) => (def_id, substs),
596 let instance = monomorphize::resolve(scx, def_id, substs);
597 if !should_trans_locally(scx.tcx(), &instance) {
602 ty::InstanceDef::Intrinsic(..) => {
604 bug!("intrinsic {:?} being reified", ty);
606 if scx.tcx().item_name(def_id) == "drop_in_place" {
607 // drop_in_place is a call to drop glue, need to instantiate
609 let ty = glue::get_drop_glue_type(scx, substs.type_at(0));
610 output.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
613 ty::InstanceDef::Virtual(..) => {
614 // don't need to emit shim if we are calling directly.
616 output.push(create_fn_trans_item(instance));
619 ty::InstanceDef::ClosureOnceShim { .. } |
620 ty::InstanceDef::Item(..) |
621 ty::InstanceDef::FnPtrShim(..) => {
622 output.push(create_fn_trans_item(instance));
627 // Returns true if we should translate an instance in the local crate.
628 // Returns false if we can just link to the upstream crate and therefore don't
629 // need a translation item.
630 fn should_trans_locally<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, instance: &Instance<'tcx>)
632 let def_id = match instance.def {
633 ty::InstanceDef::Item(def_id) => def_id,
634 ty::InstanceDef::ClosureOnceShim { .. } |
635 ty::InstanceDef::Virtual(..) |
636 ty::InstanceDef::FnPtrShim(..) |
637 ty::InstanceDef::Intrinsic(_) => return true
639 match tcx.hir.get_if_local(def_id) {
640 Some(hir_map::NodeForeignItem(..)) => {
641 false // foreign items are linked against, not translated.
645 if tcx.sess.cstore.is_exported_symbol(def_id) ||
646 tcx.sess.cstore.is_foreign_item(def_id)
648 // We can link to the item in question, no instance needed
652 if !tcx.sess.cstore.is_item_mir_available(def_id) {
653 bug!("Cannot create local trans-item for {:?}", def_id)
661 fn find_drop_glue_neighbors<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
662 dg: DropGlueKind<'tcx>,
663 output: &mut Vec<TransItem<'tcx>>) {
665 DropGlueKind::Ty(ty) => ty,
666 DropGlueKind::TyContents(_) => {
667 // We already collected the neighbors of this item via the
668 // DropGlueKind::Ty variant.
673 debug!("find_drop_glue_neighbors: {}", type_to_string(scx.tcx(), ty));
675 // Make sure the BoxFreeFn lang-item gets translated if there is a boxed value.
678 let def_id = tcx.require_lang_item(BoxFreeFnLangItem);
679 let box_free_instance = Instance::new(
681 tcx.mk_substs(iter::once(Kind::from(ty.boxed_ty())))
683 if should_trans_locally(tcx, &box_free_instance) {
684 output.push(create_fn_trans_item(box_free_instance));
688 // If the type implements Drop, also add a translation item for the
689 // monomorphized Drop::drop() implementation.
690 let has_dtor = match ty.sty {
691 ty::TyAdt(def, _) => def.has_dtor(scx.tcx()),
695 if has_dtor && !ty.is_box() {
696 let drop_trait_def_id = scx.tcx()
700 let drop_method = scx.tcx().associated_items(drop_trait_def_id)
701 .find(|it| it.kind == ty::AssociatedKind::Method)
703 let substs = scx.tcx().mk_substs_trait(ty, &[]);
704 let instance = monomorphize::resolve(scx, drop_method, substs);
705 if should_trans_locally(scx.tcx(), &instance) {
706 output.push(create_fn_trans_item(instance));
709 // This type has a Drop implementation, we'll need the contents-only
710 // version of the glue too.
711 output.push(TransItem::DropGlue(DropGlueKind::TyContents(ty)));
714 // Finally add the types of nested values
727 ty::TyDynamic(..) => {
730 ty::TyAdt(def, _) if def.is_box() => {
731 let inner_type = glue::get_drop_glue_type(scx, ty.boxed_ty());
732 if scx.type_needs_drop(inner_type) {
733 output.push(TransItem::DropGlue(DropGlueKind::Ty(inner_type)));
736 ty::TyAdt(def, substs) => {
737 for field in def.all_fields() {
738 let field_type = def_ty(scx, field.did, substs);
739 let field_type = glue::get_drop_glue_type(scx, field_type);
741 if scx.type_needs_drop(field_type) {
742 output.push(TransItem::DropGlue(DropGlueKind::Ty(field_type)));
746 ty::TyClosure(def_id, substs) => {
747 for upvar_ty in substs.upvar_tys(def_id, scx.tcx()) {
748 let upvar_ty = glue::get_drop_glue_type(scx, upvar_ty);
749 if scx.type_needs_drop(upvar_ty) {
750 output.push(TransItem::DropGlue(DropGlueKind::Ty(upvar_ty)));
754 ty::TySlice(inner_type) |
755 ty::TyArray(inner_type, _) => {
756 let inner_type = glue::get_drop_glue_type(scx, inner_type);
757 if scx.type_needs_drop(inner_type) {
758 output.push(TransItem::DropGlue(DropGlueKind::Ty(inner_type)));
761 ty::TyTuple(args, _) => {
763 let arg = glue::get_drop_glue_type(scx, arg);
764 if scx.type_needs_drop(arg) {
765 output.push(TransItem::DropGlue(DropGlueKind::Ty(arg)));
769 ty::TyProjection(_) |
774 bug!("encountered unexpected type");
779 /// For given pair of source and target type that occur in an unsizing coercion,
780 /// this function finds the pair of types that determines the vtable linking
783 /// For example, the source type might be `&SomeStruct` and the target type\
784 /// might be `&SomeTrait` in a cast like:
786 /// let src: &SomeStruct = ...;
787 /// let target = src as &SomeTrait;
789 /// Then the output of this function would be (SomeStruct, SomeTrait) since for
790 /// constructing the `target` fat-pointer we need the vtable for that pair.
792 /// Things can get more complicated though because there's also the case where
793 /// the unsized type occurs as a field:
796 /// struct ComplexStruct<T: ?Sized> {
803 /// In this case, if `T` is sized, `&ComplexStruct<T>` is a thin pointer. If `T`
804 /// is unsized, `&SomeStruct` is a fat pointer, and the vtable it points to is
805 /// for the pair of `T` (which is a trait) and the concrete type that `T` was
806 /// originally coerced from:
808 /// let src: &ComplexStruct<SomeStruct> = ...;
809 /// let target = src as &ComplexStruct<SomeTrait>;
811 /// Again, we want this `find_vtable_types_for_unsizing()` to provide the pair
812 /// `(SomeStruct, SomeTrait)`.
814 /// Finally, there is also the case of custom unsizing coercions, e.g. for
815 /// smart pointers such as `Rc` and `Arc`.
816 fn find_vtable_types_for_unsizing<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
817 source_ty: ty::Ty<'tcx>,
818 target_ty: ty::Ty<'tcx>)
819 -> (ty::Ty<'tcx>, ty::Ty<'tcx>) {
820 let ptr_vtable = |inner_source: ty::Ty<'tcx>, inner_target: ty::Ty<'tcx>| {
821 if !scx.type_is_sized(inner_source) {
822 (inner_source, inner_target)
824 scx.tcx().struct_lockstep_tails(inner_source, inner_target)
827 match (&source_ty.sty, &target_ty.sty) {
828 (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
829 &ty::TyRef(_, ty::TypeAndMut { ty: b, .. })) |
830 (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
831 &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) |
832 (&ty::TyRawPtr(ty::TypeAndMut { ty: a, .. }),
833 &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) => {
836 (&ty::TyAdt(def_a, _), &ty::TyAdt(def_b, _)) if def_a.is_box() && def_b.is_box() => {
837 ptr_vtable(source_ty.boxed_ty(), target_ty.boxed_ty())
840 (&ty::TyAdt(source_adt_def, source_substs),
841 &ty::TyAdt(target_adt_def, target_substs)) => {
842 assert_eq!(source_adt_def, target_adt_def);
845 monomorphize::custom_coerce_unsize_info(scx, source_ty, target_ty);
847 let coerce_index = match kind {
848 CustomCoerceUnsized::Struct(i) => i
851 let source_fields = &source_adt_def.struct_variant().fields;
852 let target_fields = &target_adt_def.struct_variant().fields;
854 assert!(coerce_index < source_fields.len() &&
855 source_fields.len() == target_fields.len());
857 find_vtable_types_for_unsizing(scx,
858 source_fields[coerce_index].ty(scx.tcx(),
860 target_fields[coerce_index].ty(scx.tcx(),
863 _ => bug!("find_vtable_types_for_unsizing: invalid coercion {:?} -> {:?}",
869 fn create_fn_trans_item<'a, 'tcx>(instance: Instance<'tcx>) -> TransItem<'tcx> {
870 debug!("create_fn_trans_item(instance={})", instance);
871 TransItem::Fn(instance)
874 /// Creates a `TransItem` for each method that is referenced by the vtable for
875 /// the given trait/impl pair.
876 fn create_trans_items_for_vtable_methods<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
877 trait_ty: ty::Ty<'tcx>,
878 impl_ty: ty::Ty<'tcx>,
879 output: &mut Vec<TransItem<'tcx>>) {
880 assert!(!trait_ty.needs_subst() && !trait_ty.has_escaping_regions() &&
881 !impl_ty.needs_subst() && !impl_ty.has_escaping_regions());
883 if let ty::TyDynamic(ref trait_ty, ..) = trait_ty.sty {
884 if let Some(principal) = trait_ty.principal() {
885 let poly_trait_ref = principal.with_self_ty(scx.tcx(), impl_ty);
886 assert!(!poly_trait_ref.has_escaping_regions());
888 // Walk all methods of the trait, including those of its supertraits
889 let methods = traits::get_vtable_methods(scx.tcx(), poly_trait_ref);
890 let methods = methods.filter_map(|method| method)
891 .map(|(def_id, substs)| monomorphize::resolve(scx, def_id, substs))
892 .filter(|&instance| should_trans_locally(scx.tcx(), &instance))
893 .map(|instance| create_fn_trans_item(instance));
894 output.extend(methods);
896 // Also add the destructor
897 let dg_type = glue::get_drop_glue_type(scx, impl_ty);
898 output.push(TransItem::DropGlue(DropGlueKind::Ty(dg_type)));
902 //=-----------------------------------------------------------------------------
904 //=-----------------------------------------------------------------------------
906 struct RootCollector<'b, 'a: 'b, 'tcx: 'a + 'b> {
907 scx: &'b SharedCrateContext<'a, 'tcx>,
908 mode: TransItemCollectionMode,
909 output: &'b mut Vec<TransItem<'tcx>>,
912 impl<'b, 'a, 'v> ItemLikeVisitor<'v> for RootCollector<'b, 'a, 'v> {
913 fn visit_item(&mut self, item: &'v hir::Item) {
915 hir::ItemExternCrate(..) |
917 hir::ItemForeignMod(..) |
919 hir::ItemDefaultImpl(..) |
921 hir::ItemMod(..) => {
922 // Nothing to do, just keep recursing...
925 hir::ItemImpl(..) => {
926 if self.mode == TransItemCollectionMode::Eager {
927 create_trans_items_for_default_impls(self.scx,
933 hir::ItemEnum(_, ref generics) |
934 hir::ItemStruct(_, ref generics) |
935 hir::ItemUnion(_, ref generics) => {
936 if !generics.is_parameterized() {
937 if self.mode == TransItemCollectionMode::Eager {
938 let def_id = self.scx.tcx().hir.local_def_id(item.id);
939 debug!("RootCollector: ADT drop-glue for {}",
940 def_id_to_string(self.scx.tcx(), def_id));
942 let ty = def_ty(self.scx, def_id, Substs::empty());
943 let ty = glue::get_drop_glue_type(self.scx, ty);
944 self.output.push(TransItem::DropGlue(DropGlueKind::Ty(ty)));
948 hir::ItemStatic(..) => {
949 debug!("RootCollector: ItemStatic({})",
950 def_id_to_string(self.scx.tcx(),
951 self.scx.tcx().hir.local_def_id(item.id)));
952 self.output.push(TransItem::Static(item.id));
954 hir::ItemConst(..) => {
955 // const items only generate translation items if they are
956 // actually used somewhere. Just declaring them is insufficient.
958 hir::ItemFn(.., ref generics, _) => {
959 if !generics.is_type_parameterized() {
960 let def_id = self.scx.tcx().hir.local_def_id(item.id);
962 debug!("RootCollector: ItemFn({})",
963 def_id_to_string(self.scx.tcx(), def_id));
965 let instance = Instance::mono(self.scx.tcx(), def_id);
966 self.output.push(TransItem::Fn(instance));
972 fn visit_trait_item(&mut self, _: &'v hir::TraitItem) {
973 // Even if there's a default body with no explicit generics,
974 // it's still generic over some `Self: Trait`, so not a root.
977 fn visit_impl_item(&mut self, ii: &'v hir::ImplItem) {
979 hir::ImplItemKind::Method(hir::MethodSig {
983 let hir_map = &self.scx.tcx().hir;
984 let parent_node_id = hir_map.get_parent_node(ii.id);
985 let is_impl_generic = match hir_map.expect_item(parent_node_id) {
987 node: hir::ItemImpl(_, _, ref generics, ..),
990 generics.is_type_parameterized()
997 if !generics.is_type_parameterized() && !is_impl_generic {
998 let def_id = self.scx.tcx().hir.local_def_id(ii.id);
1000 debug!("RootCollector: MethodImplItem({})",
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));
1007 _ => { /* Nothing to do here */ }
1012 fn create_trans_items_for_default_impls<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
1013 item: &'tcx hir::Item,
1014 output: &mut Vec<TransItem<'tcx>>) {
1015 let tcx = scx.tcx();
1021 ref impl_item_refs) => {
1022 if generics.is_type_parameterized() {
1026 let impl_def_id = tcx.hir.local_def_id(item.id);
1028 debug!("create_trans_items_for_default_impls(item={})",
1029 def_id_to_string(tcx, impl_def_id));
1031 if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1032 let callee_substs = tcx.erase_regions(&trait_ref.substs);
1033 let overridden_methods: FxHashSet<_> =
1034 impl_item_refs.iter()
1035 .map(|iiref| iiref.name)
1037 for method in tcx.provided_trait_methods(trait_ref.def_id) {
1038 if overridden_methods.contains(&method.name) {
1042 if !tcx.item_generics(method.def_id).types.is_empty() {
1047 monomorphize::resolve(scx, method.def_id, callee_substs);
1049 let predicates = tcx.item_predicates(instance.def_id()).predicates
1050 .subst(tcx, instance.substs);
1051 if !traits::normalize_and_test_predicates(tcx, predicates) {
1055 if should_trans_locally(tcx, &instance) {
1056 output.push(create_fn_trans_item(instance));
1067 /// Scan the MIR in order to find function calls, closures, and drop-glue
1068 fn collect_neighbours<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
1069 instance: Instance<'tcx>,
1070 output: &mut Vec<TransItem<'tcx>>)
1072 let mir = scx.tcx().instance_mir(instance.def);
1074 let mut visitor = MirNeighborCollector {
1078 param_substs: instance.substs
1081 visitor.visit_mir(&mir);
1082 for promoted in &mir.promoted {
1083 visitor.mir = promoted;
1084 visitor.visit_mir(promoted);
1088 fn def_id_to_string<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1091 let mut output = String::new();
1092 let printer = DefPathBasedNames::new(tcx, false, false);
1093 printer.push_def_path(def_id, &mut output);
1097 fn type_to_string<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1100 let mut output = String::new();
1101 let printer = DefPathBasedNames::new(tcx, false, false);
1102 printer.push_type_name(ty, &mut output);