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::{ExchangeMallocFnLangItem};
198 use rustc::ty::subst::Substs;
199 use rustc::ty::{self, TypeFoldable, TyCtxt};
200 use rustc::ty::adjustment::CustomCoerceUnsized;
201 use rustc::mir::{self, Location};
202 use rustc::mir::visit::Visitor as MirVisitor;
204 use context::SharedCrateContext;
205 use common::{def_ty, instance_ty};
206 use monomorphize::{self, Instance};
207 use rustc::util::nodemap::{FxHashSet, FxHashMap, DefIdMap};
209 use trans_item::{TransItem, DefPathBasedNames, InstantiationMode};
211 #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
212 pub enum TransItemCollectionMode {
217 /// Maps every translation item to all translation items it references in its
219 pub struct InliningMap<'tcx> {
220 // Maps a source translation item to a range of target translation items
221 // that are potentially inlined by LLVM into the source.
222 // The two numbers in the tuple are the start (inclusive) and
223 // end index (exclusive) within the `targets` vecs.
224 index: FxHashMap<TransItem<'tcx>, (usize, usize)>,
225 targets: Vec<TransItem<'tcx>>,
228 impl<'tcx> InliningMap<'tcx> {
230 fn new() -> InliningMap<'tcx> {
237 fn record_inlining_canditates<I>(&mut self,
238 source: TransItem<'tcx>,
240 where I: Iterator<Item=TransItem<'tcx>>
242 assert!(!self.index.contains_key(&source));
244 let start_index = self.targets.len();
245 self.targets.extend(targets);
246 let end_index = self.targets.len();
247 self.index.insert(source, (start_index, end_index));
250 // Internally iterate over all items referenced by `source` which will be
251 // made available for inlining.
252 pub fn with_inlining_candidates<F>(&self, source: TransItem<'tcx>, mut f: F)
253 where F: FnMut(TransItem<'tcx>) {
254 if let Some(&(start_index, end_index)) = self.index.get(&source)
256 for candidate in &self.targets[start_index .. end_index] {
263 pub fn collect_crate_translation_items<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
264 mode: TransItemCollectionMode)
265 -> (FxHashSet<TransItem<'tcx>>,
267 // We are not tracking dependencies of this pass as it has to be re-executed
268 // every time no matter what.
269 scx.tcx().dep_graph.with_ignore(|| {
270 let roots = collect_roots(scx, mode);
272 debug!("Building translation item graph, beginning at roots");
273 let mut visited = FxHashSet();
274 let mut recursion_depths = DefIdMap();
275 let mut inlining_map = InliningMap::new();
278 collect_items_rec(scx,
281 &mut recursion_depths,
285 (visited, inlining_map)
289 // Find all non-generic items by walking the HIR. These items serve as roots to
290 // start monomorphizing from.
291 fn collect_roots<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
292 mode: TransItemCollectionMode)
293 -> Vec<TransItem<'tcx>> {
294 debug!("Collecting roots");
295 let mut roots = Vec::new();
298 let mut visitor = RootCollector {
304 scx.tcx().hir.krate().visit_all_item_likes(&mut visitor);
307 // We can only translate items that are instantiable - items all of
308 // whose predicates hold. Luckily, items that aren't instantiable
309 // can't actually be used, so we can just skip translating them.
310 roots.retain(|root| root.is_instantiable(scx.tcx()));
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::Static(node_id) => {
332 let def_id = scx.tcx().hir.local_def_id(node_id);
333 let instance = Instance::mono(scx.tcx(), def_id);
335 // Sanity check whether this ended up being collected accidentally
336 debug_assert!(should_trans_locally(scx.tcx(), &instance));
338 let ty = instance_ty(scx, &instance);
339 visit_drop_use(scx, ty, true, &mut neighbors);
341 recursion_depth_reset = None;
343 collect_neighbours(scx, instance, &mut neighbors);
345 TransItem::Fn(instance) => {
346 // Sanity check whether this ended up being collected accidentally
347 debug_assert!(should_trans_locally(scx.tcx(), &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);
357 TransItem::GlobalAsm(..) => {
358 recursion_depth_reset = None;
362 record_inlining_canditates(scx.tcx(), starting_point, &neighbors[..], inlining_map);
364 for neighbour in neighbors {
365 collect_items_rec(scx, neighbour, visited, recursion_depths, inlining_map);
368 if let Some((def_id, depth)) = recursion_depth_reset {
369 recursion_depths.insert(def_id, depth);
372 debug!("END collect_items_rec({})", starting_point.to_string(scx.tcx()));
375 fn record_inlining_canditates<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
376 caller: TransItem<'tcx>,
377 callees: &[TransItem<'tcx>],
378 inlining_map: &mut InliningMap<'tcx>) {
379 let is_inlining_candidate = |trans_item: &TransItem<'tcx>| {
380 trans_item.instantiation_mode(tcx) == InstantiationMode::LocalCopy
383 let inlining_candidates = callees.into_iter()
385 .filter(is_inlining_candidate);
387 inlining_map.record_inlining_canditates(caller, inlining_candidates);
390 fn check_recursion_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
391 instance: Instance<'tcx>,
392 recursion_depths: &mut DefIdMap<usize>)
394 let def_id = instance.def_id();
395 let recursion_depth = recursion_depths.get(&def_id).cloned().unwrap_or(0);
396 debug!(" => recursion depth={}", recursion_depth);
398 let recursion_depth = if Some(def_id) == tcx.lang_items.drop_in_place_fn() {
399 // HACK: drop_in_place creates tight monomorphization loops. Give
406 // Code that needs to instantiate the same function recursively
407 // more than the recursion limit is assumed to be causing an
408 // infinite expansion.
409 if recursion_depth > tcx.sess.recursion_limit.get() {
410 let error = format!("reached the recursion limit while instantiating `{}`",
412 if let Some(node_id) = tcx.hir.as_local_node_id(def_id) {
413 tcx.sess.span_fatal(tcx.hir.span(node_id), &error);
415 tcx.sess.fatal(&error);
419 recursion_depths.insert(def_id, recursion_depth + 1);
421 (def_id, recursion_depth)
424 fn check_type_length_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
425 instance: Instance<'tcx>)
427 let type_length = instance.substs.types().flat_map(|ty| ty.walk()).count();
428 debug!(" => type length={}", type_length);
430 // Rust code can easily create exponentially-long types using only a
431 // polynomial recursion depth. Even with the default recursion
432 // depth, you can easily get cases that take >2^60 steps to run,
433 // which means that rustc basically hangs.
435 // Bail out in these cases to avoid that bad user experience.
436 let type_length_limit = tcx.sess.type_length_limit.get();
437 if type_length > type_length_limit {
438 // The instance name is already known to be too long for rustc. Use
439 // `{:.64}` to avoid blasting the user's terminal with thousands of
440 // lines of type-name.
441 let instance_name = instance.to_string();
442 let msg = format!("reached the type-length limit while instantiating `{:.64}...`",
444 let mut diag = if let Some(node_id) = tcx.hir.as_local_node_id(instance.def_id()) {
445 tcx.sess.struct_span_fatal(tcx.hir.span(node_id), &msg)
447 tcx.sess.struct_fatal(&msg)
451 "consider adding a `#![type_length_limit=\"{}\"]` attribute to your crate",
452 type_length_limit*2));
454 tcx.sess.abort_if_errors();
458 struct MirNeighborCollector<'a, 'tcx: 'a> {
459 scx: &'a SharedCrateContext<'a, 'tcx>,
460 mir: &'a mir::Mir<'tcx>,
461 output: &'a mut Vec<TransItem<'tcx>>,
462 param_substs: &'tcx Substs<'tcx>
465 impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
467 fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: Location) {
468 debug!("visiting rvalue {:?}", *rvalue);
471 // When doing an cast from a regular pointer to a fat pointer, we
472 // have to instantiate all methods of the trait being cast to, so we
473 // can build the appropriate vtable.
474 mir::Rvalue::Cast(mir::CastKind::Unsize, ref operand, target_ty) => {
475 let target_ty = self.scx.tcx().trans_apply_param_substs(self.param_substs,
477 let source_ty = operand.ty(&self.mir.local_decls, self.scx.tcx());
478 let source_ty = self.scx.tcx().trans_apply_param_substs(self.param_substs,
480 let (source_ty, target_ty) = find_vtable_types_for_unsizing(self.scx,
483 // This could also be a different Unsize instruction, like
484 // from a fixed sized array to a slice. But we are only
485 // interested in things that produce a vtable.
486 if target_ty.is_trait() && !source_ty.is_trait() {
487 create_trans_items_for_vtable_methods(self.scx,
493 mir::Rvalue::Cast(mir::CastKind::ReifyFnPointer, ref operand, _) => {
494 let fn_ty = operand.ty(&self.mir.local_decls, self.scx.tcx());
495 let fn_ty = self.scx.tcx().trans_apply_param_substs(self.param_substs,
497 visit_fn_use(self.scx, fn_ty, false, &mut self.output);
499 mir::Rvalue::Cast(mir::CastKind::ClosureFnPointer, ref operand, _) => {
500 let source_ty = operand.ty(&self.mir.local_decls, self.scx.tcx());
501 let source_ty = self.scx.tcx().trans_apply_param_substs(self.param_substs,
503 match source_ty.sty {
504 ty::TyClosure(def_id, substs) => {
505 let instance = monomorphize::resolve_closure(
506 self.scx, def_id, substs, ty::ClosureKind::FnOnce);
507 self.output.push(create_fn_trans_item(instance));
512 mir::Rvalue::NullaryOp(mir::NullOp::Box, _) => {
513 let tcx = self.scx.tcx();
514 let exchange_malloc_fn_def_id = tcx
516 .require(ExchangeMallocFnLangItem)
517 .unwrap_or_else(|e| self.scx.sess().fatal(&e));
518 let instance = Instance::mono(tcx, exchange_malloc_fn_def_id);
519 if should_trans_locally(tcx, &instance) {
520 self.output.push(create_fn_trans_item(instance));
523 _ => { /* not interesting */ }
526 self.super_rvalue(rvalue, location);
529 fn visit_constant(&mut self, constant: &mir::Constant<'tcx>, location: Location) {
530 debug!("visiting constant {:?} @ {:?}", *constant, location);
532 if let ty::TyFnDef(..) = constant.ty.sty {
533 // function definitions are zero-sized, and only generate
534 // IR when they are called/reified.
535 self.super_constant(constant, location);
539 if let mir::Literal::Item { def_id, substs } = constant.literal {
540 let substs = self.scx.tcx().trans_apply_param_substs(self.param_substs,
542 let instance = monomorphize::resolve(self.scx, def_id, substs);
543 collect_neighbours(self.scx, instance, self.output);
546 self.super_constant(constant, location);
549 fn visit_terminator_kind(&mut self,
550 block: mir::BasicBlock,
551 kind: &mir::TerminatorKind<'tcx>,
552 location: Location) {
553 debug!("visiting terminator {:?} @ {:?}", kind, location);
555 let tcx = self.scx.tcx();
557 mir::TerminatorKind::Call { ref func, .. } => {
558 let callee_ty = func.ty(&self.mir.local_decls, tcx);
559 let callee_ty = tcx.trans_apply_param_substs(self.param_substs, &callee_ty);
560 visit_fn_use(self.scx, callee_ty, true, &mut self.output);
562 mir::TerminatorKind::Drop { ref location, .. } |
563 mir::TerminatorKind::DropAndReplace { ref location, .. } => {
564 let ty = location.ty(&self.mir.local_decls, self.scx.tcx())
565 .to_ty(self.scx.tcx());
566 let ty = tcx.trans_apply_param_substs(self.param_substs, &ty);
567 visit_drop_use(self.scx, ty, true, self.output);
569 mir::TerminatorKind::Goto { .. } |
570 mir::TerminatorKind::SwitchInt { .. } |
571 mir::TerminatorKind::Resume |
572 mir::TerminatorKind::Return |
573 mir::TerminatorKind::Unreachable |
574 mir::TerminatorKind::Assert { .. } => {}
577 self.super_terminator_kind(block, kind, location);
581 fn visit_drop_use<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
583 is_direct_call: bool,
584 output: &mut Vec<TransItem<'tcx>>)
586 let instance = monomorphize::resolve_drop_in_place(scx, ty);
587 visit_instance_use(scx, instance, is_direct_call, output);
590 fn visit_fn_use<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
592 is_direct_call: bool,
593 output: &mut Vec<TransItem<'tcx>>)
595 if let ty::TyFnDef(def_id, substs) = ty.sty {
596 let instance = monomorphize::resolve(scx, def_id, substs);
597 visit_instance_use(scx, instance, is_direct_call, output);
601 fn visit_instance_use<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
602 instance: ty::Instance<'tcx>,
603 is_direct_call: bool,
604 output: &mut Vec<TransItem<'tcx>>)
606 debug!("visit_item_use({:?}, is_direct_call={:?})", instance, is_direct_call);
607 if !should_trans_locally(scx.tcx(), &instance) {
612 ty::InstanceDef::Intrinsic(def_id) => {
614 bug!("intrinsic {:?} being reified", def_id);
617 ty::InstanceDef::Virtual(..) |
618 ty::InstanceDef::DropGlue(_, None) => {
619 // don't need to emit shim if we are calling directly.
621 output.push(create_fn_trans_item(instance));
624 ty::InstanceDef::DropGlue(_, Some(_)) => {
625 output.push(create_fn_trans_item(instance));
627 ty::InstanceDef::ClosureOnceShim { .. } |
628 ty::InstanceDef::Item(..) |
629 ty::InstanceDef::FnPtrShim(..) => {
630 output.push(create_fn_trans_item(instance));
635 // Returns true if we should translate an instance in the local crate.
636 // Returns false if we can just link to the upstream crate and therefore don't
637 // need a translation item.
638 fn should_trans_locally<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, instance: &Instance<'tcx>)
640 let def_id = match instance.def {
641 ty::InstanceDef::Item(def_id) => def_id,
642 ty::InstanceDef::ClosureOnceShim { .. } |
643 ty::InstanceDef::Virtual(..) |
644 ty::InstanceDef::FnPtrShim(..) |
645 ty::InstanceDef::DropGlue(..) |
646 ty::InstanceDef::Intrinsic(_) => return true
648 match tcx.hir.get_if_local(def_id) {
649 Some(hir_map::NodeForeignItem(..)) => {
650 false // foreign items are linked against, not translated.
654 if tcx.is_exported_symbol(def_id) ||
655 tcx.is_foreign_item(def_id)
657 // We can link to the item in question, no instance needed
661 if !tcx.is_mir_available(def_id) {
662 bug!("Cannot create local trans-item for {:?}", def_id)
670 /// For given pair of source and target type that occur in an unsizing coercion,
671 /// this function finds the pair of types that determines the vtable linking
674 /// For example, the source type might be `&SomeStruct` and the target type\
675 /// might be `&SomeTrait` in a cast like:
677 /// let src: &SomeStruct = ...;
678 /// let target = src as &SomeTrait;
680 /// Then the output of this function would be (SomeStruct, SomeTrait) since for
681 /// constructing the `target` fat-pointer we need the vtable for that pair.
683 /// Things can get more complicated though because there's also the case where
684 /// the unsized type occurs as a field:
687 /// struct ComplexStruct<T: ?Sized> {
694 /// In this case, if `T` is sized, `&ComplexStruct<T>` is a thin pointer. If `T`
695 /// is unsized, `&SomeStruct` is a fat pointer, and the vtable it points to is
696 /// for the pair of `T` (which is a trait) and the concrete type that `T` was
697 /// originally coerced from:
699 /// let src: &ComplexStruct<SomeStruct> = ...;
700 /// let target = src as &ComplexStruct<SomeTrait>;
702 /// Again, we want this `find_vtable_types_for_unsizing()` to provide the pair
703 /// `(SomeStruct, SomeTrait)`.
705 /// Finally, there is also the case of custom unsizing coercions, e.g. for
706 /// smart pointers such as `Rc` and `Arc`.
707 fn find_vtable_types_for_unsizing<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
708 source_ty: ty::Ty<'tcx>,
709 target_ty: ty::Ty<'tcx>)
710 -> (ty::Ty<'tcx>, ty::Ty<'tcx>) {
711 let ptr_vtable = |inner_source: ty::Ty<'tcx>, inner_target: ty::Ty<'tcx>| {
712 if !scx.type_is_sized(inner_source) {
713 (inner_source, inner_target)
715 scx.tcx().struct_lockstep_tails(inner_source, inner_target)
718 match (&source_ty.sty, &target_ty.sty) {
719 (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
720 &ty::TyRef(_, ty::TypeAndMut { ty: b, .. })) |
721 (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
722 &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) |
723 (&ty::TyRawPtr(ty::TypeAndMut { ty: a, .. }),
724 &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) => {
727 (&ty::TyAdt(def_a, _), &ty::TyAdt(def_b, _)) if def_a.is_box() && def_b.is_box() => {
728 ptr_vtable(source_ty.boxed_ty(), target_ty.boxed_ty())
731 (&ty::TyAdt(source_adt_def, source_substs),
732 &ty::TyAdt(target_adt_def, target_substs)) => {
733 assert_eq!(source_adt_def, target_adt_def);
736 monomorphize::custom_coerce_unsize_info(scx, source_ty, target_ty);
738 let coerce_index = match kind {
739 CustomCoerceUnsized::Struct(i) => i
742 let source_fields = &source_adt_def.struct_variant().fields;
743 let target_fields = &target_adt_def.struct_variant().fields;
745 assert!(coerce_index < source_fields.len() &&
746 source_fields.len() == target_fields.len());
748 find_vtable_types_for_unsizing(scx,
749 source_fields[coerce_index].ty(scx.tcx(),
751 target_fields[coerce_index].ty(scx.tcx(),
754 _ => bug!("find_vtable_types_for_unsizing: invalid coercion {:?} -> {:?}",
760 fn create_fn_trans_item<'a, 'tcx>(instance: Instance<'tcx>) -> TransItem<'tcx> {
761 debug!("create_fn_trans_item(instance={})", instance);
762 TransItem::Fn(instance)
765 /// Creates a `TransItem` for each method that is referenced by the vtable for
766 /// the given trait/impl pair.
767 fn create_trans_items_for_vtable_methods<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
768 trait_ty: ty::Ty<'tcx>,
769 impl_ty: ty::Ty<'tcx>,
770 output: &mut Vec<TransItem<'tcx>>) {
771 assert!(!trait_ty.needs_subst() && !trait_ty.has_escaping_regions() &&
772 !impl_ty.needs_subst() && !impl_ty.has_escaping_regions());
774 if let ty::TyDynamic(ref trait_ty, ..) = trait_ty.sty {
775 if let Some(principal) = trait_ty.principal() {
776 let poly_trait_ref = principal.with_self_ty(scx.tcx(), impl_ty);
777 assert!(!poly_trait_ref.has_escaping_regions());
779 // Walk all methods of the trait, including those of its supertraits
780 let methods = traits::get_vtable_methods(scx.tcx(), poly_trait_ref);
781 let methods = methods.filter_map(|method| method)
782 .map(|(def_id, substs)| monomorphize::resolve(scx, def_id, substs))
783 .filter(|&instance| should_trans_locally(scx.tcx(), &instance))
784 .map(|instance| create_fn_trans_item(instance));
785 output.extend(methods);
787 // Also add the destructor
788 visit_drop_use(scx, impl_ty, false, output);
792 //=-----------------------------------------------------------------------------
794 //=-----------------------------------------------------------------------------
796 struct RootCollector<'b, 'a: 'b, 'tcx: 'a + 'b> {
797 scx: &'b SharedCrateContext<'a, 'tcx>,
798 mode: TransItemCollectionMode,
799 output: &'b mut Vec<TransItem<'tcx>>,
802 impl<'b, 'a, 'v> ItemLikeVisitor<'v> for RootCollector<'b, 'a, 'v> {
803 fn visit_item(&mut self, item: &'v hir::Item) {
805 hir::ItemExternCrate(..) |
807 hir::ItemForeignMod(..) |
809 hir::ItemDefaultImpl(..) |
811 hir::ItemMod(..) => {
812 // Nothing to do, just keep recursing...
815 hir::ItemImpl(..) => {
816 if self.mode == TransItemCollectionMode::Eager {
817 create_trans_items_for_default_impls(self.scx,
823 hir::ItemEnum(_, ref generics) |
824 hir::ItemStruct(_, ref generics) |
825 hir::ItemUnion(_, ref generics) => {
826 if !generics.is_parameterized() {
827 if self.mode == TransItemCollectionMode::Eager {
828 let def_id = self.scx.tcx().hir.local_def_id(item.id);
829 debug!("RootCollector: ADT drop-glue for {}",
830 def_id_to_string(self.scx.tcx(), def_id));
832 let ty = def_ty(self.scx, def_id, Substs::empty());
833 visit_drop_use(self.scx, ty, true, self.output);
837 hir::ItemGlobalAsm(..) => {
838 debug!("RootCollector: ItemGlobalAsm({})",
839 def_id_to_string(self.scx.tcx(),
840 self.scx.tcx().hir.local_def_id(item.id)));
841 self.output.push(TransItem::GlobalAsm(item.id));
843 hir::ItemStatic(..) => {
844 debug!("RootCollector: ItemStatic({})",
845 def_id_to_string(self.scx.tcx(),
846 self.scx.tcx().hir.local_def_id(item.id)));
847 self.output.push(TransItem::Static(item.id));
849 hir::ItemConst(..) => {
850 // const items only generate translation items if they are
851 // actually used somewhere. Just declaring them is insufficient.
853 hir::ItemFn(.., ref generics, _) => {
854 if !generics.is_type_parameterized() {
855 let def_id = self.scx.tcx().hir.local_def_id(item.id);
857 debug!("RootCollector: ItemFn({})",
858 def_id_to_string(self.scx.tcx(), def_id));
860 let instance = Instance::mono(self.scx.tcx(), def_id);
861 self.output.push(TransItem::Fn(instance));
867 fn visit_trait_item(&mut self, _: &'v hir::TraitItem) {
868 // Even if there's a default body with no explicit generics,
869 // it's still generic over some `Self: Trait`, so not a root.
872 fn visit_impl_item(&mut self, ii: &'v hir::ImplItem) {
874 hir::ImplItemKind::Method(hir::MethodSig {
878 let hir_map = &self.scx.tcx().hir;
879 let parent_node_id = hir_map.get_parent_node(ii.id);
880 let is_impl_generic = match hir_map.expect_item(parent_node_id) {
882 node: hir::ItemImpl(_, _, _, ref generics, ..),
885 generics.is_type_parameterized()
892 if !generics.is_type_parameterized() && !is_impl_generic {
893 let def_id = self.scx.tcx().hir.local_def_id(ii.id);
895 debug!("RootCollector: MethodImplItem({})",
896 def_id_to_string(self.scx.tcx(), def_id));
898 let instance = Instance::mono(self.scx.tcx(), def_id);
899 self.output.push(TransItem::Fn(instance));
902 _ => { /* Nothing to do here */ }
907 fn create_trans_items_for_default_impls<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
908 item: &'tcx hir::Item,
909 output: &mut Vec<TransItem<'tcx>>) {
917 ref impl_item_refs) => {
918 if generics.is_type_parameterized() {
922 let impl_def_id = tcx.hir.local_def_id(item.id);
924 debug!("create_trans_items_for_default_impls(item={})",
925 def_id_to_string(tcx, impl_def_id));
927 if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) {
928 let callee_substs = tcx.erase_regions(&trait_ref.substs);
929 let overridden_methods: FxHashSet<_> =
930 impl_item_refs.iter()
931 .map(|iiref| iiref.name)
933 for method in tcx.provided_trait_methods(trait_ref.def_id) {
934 if overridden_methods.contains(&method.name) {
938 if !tcx.generics_of(method.def_id).types.is_empty() {
943 monomorphize::resolve(scx, method.def_id, callee_substs);
945 let trans_item = create_fn_trans_item(instance);
946 if trans_item.is_instantiable(tcx) && should_trans_locally(tcx, &instance) {
947 output.push(trans_item);
958 /// Scan the MIR in order to find function calls, closures, and drop-glue
959 fn collect_neighbours<'a, 'tcx>(scx: &SharedCrateContext<'a, 'tcx>,
960 instance: Instance<'tcx>,
961 output: &mut Vec<TransItem<'tcx>>)
963 let mir = scx.tcx().instance_mir(instance.def);
965 let mut visitor = MirNeighborCollector {
969 param_substs: instance.substs
972 visitor.visit_mir(&mir);
973 for promoted in &mir.promoted {
974 visitor.mir = promoted;
975 visitor.visit_mir(promoted);
979 fn def_id_to_string<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
982 let mut output = String::new();
983 let printer = DefPathBasedNames::new(tcx, false, false);
984 printer.push_def_path(def_id, &mut output);