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 //! Mono 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 "mono 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 "mono item" is something that results in a function or global in
47 //! the LLVM IR of a codegen unit. Mono items do not stand on their
48 //! own, they can reference other mono items. For example, if function
49 //! `foo()` calls function `bar()` then the mono item for `foo()`
50 //! references the mono item for function `bar()`. In general, the
51 //! definition for mono item A referencing a mono item B is that
52 //! the LLVM artifact produced for A references the LLVM artifact produced
55 //! - Mono items and the references between them form a directed graph,
56 //! where the mono items are the nodes and references form the edges.
57 //! Let's call this graph the "mono item graph".
59 //! - The mono item graph for a program contains all mono 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 //! mono 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 mono 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 mono 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 mono 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 mono item, we have found a neighbor. Since the
82 //! mono 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 mono 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 mono 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 mono 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 //! mono 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 mono items are introduced by MIR drop-statements. The
128 //! generated mono 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 mono. If it is
154 //! about to create a mono 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 //! Mono 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 mono 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 mono 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 mono item will be produced
189 //! regardless of whether it is actually needed or not.
191 use rustc::hir::{self, TransFnAttrFlags};
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::const_val::ConstVal;
197 use rustc::mir::interpret::{Value, PrimVal, AllocId, Pointer};
198 use rustc::middle::lang_items::{ExchangeMallocFnLangItem, StartFnLangItem};
199 use rustc::ty::subst::{Substs, Kind};
200 use rustc::ty::{self, TypeFoldable, Ty, TyCtxt};
201 use rustc::ty::adjustment::CustomCoerceUnsized;
202 use rustc::session::config;
203 use rustc::mir::{self, Location, Promoted};
204 use rustc::mir::visit::Visitor as MirVisitor;
205 use rustc::mir::mono::MonoItem;
206 use rustc::mir::interpret::GlobalId;
208 use monomorphize::{self, Instance};
209 use rustc::util::nodemap::{FxHashSet, FxHashMap, DefIdMap};
211 use monomorphize::item::{MonoItemExt, DefPathBasedNames, InstantiationMode};
213 use rustc_data_structures::bitvec::BitVector;
217 #[derive(PartialEq, Eq, Hash, Clone, Copy, Debug)]
218 pub enum MonoItemCollectionMode {
223 /// Maps every mono item to all mono items it references in its
225 pub struct InliningMap<'tcx> {
226 // Maps a source mono item to the range of mono items
228 // The two numbers in the tuple are the start (inclusive) and
229 // end index (exclusive) within the `targets` vecs.
230 index: FxHashMap<MonoItem<'tcx>, (usize, usize)>,
231 targets: Vec<MonoItem<'tcx>>,
233 // Contains one bit per mono item in the `targets` field. That bit
234 // is true if that mono item needs to be inlined into every CGU.
238 impl<'tcx> InliningMap<'tcx> {
240 fn new() -> InliningMap<'tcx> {
244 inlines: BitVector::new(1024),
248 fn record_accesses<I>(&mut self,
249 source: MonoItem<'tcx>,
251 where I: Iterator<Item=(MonoItem<'tcx>, bool)> + ExactSizeIterator
253 assert!(!self.index.contains_key(&source));
255 let start_index = self.targets.len();
256 let new_items_count = new_targets.len();
257 let new_items_count_total = new_items_count + self.targets.len();
259 self.targets.reserve(new_items_count);
260 self.inlines.grow(new_items_count_total);
262 for (i, (target, inline)) in new_targets.enumerate() {
263 self.targets.push(target);
265 self.inlines.insert(i + start_index);
269 let end_index = self.targets.len();
270 self.index.insert(source, (start_index, end_index));
273 // Internally iterate over all items referenced by `source` which will be
274 // made available for inlining.
275 pub fn with_inlining_candidates<F>(&self, source: MonoItem<'tcx>, mut f: F)
276 where F: FnMut(MonoItem<'tcx>)
278 if let Some(&(start_index, end_index)) = self.index.get(&source) {
279 for (i, candidate) in self.targets[start_index .. end_index]
282 if self.inlines.contains(start_index + i) {
289 // Internally iterate over all items and the things each accesses.
290 pub fn iter_accesses<F>(&self, mut f: F)
291 where F: FnMut(MonoItem<'tcx>, &[MonoItem<'tcx>])
293 for (&accessor, &(start_index, end_index)) in &self.index {
294 f(accessor, &self.targets[start_index .. end_index])
299 pub fn collect_crate_mono_items<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
300 mode: MonoItemCollectionMode)
301 -> (FxHashSet<MonoItem<'tcx>>,
303 let roots = collect_roots(tcx, mode);
305 debug!("Building mono item graph, beginning at roots");
306 let mut visited = FxHashSet();
307 let mut recursion_depths = DefIdMap();
308 let mut inlining_map = InliningMap::new();
311 collect_items_rec(tcx,
314 &mut recursion_depths,
318 (visited, inlining_map)
321 // Find all non-generic items by walking the HIR. These items serve as roots to
322 // start monomorphizing from.
323 fn collect_roots<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
324 mode: MonoItemCollectionMode)
325 -> Vec<MonoItem<'tcx>> {
326 debug!("Collecting roots");
327 let mut roots = Vec::new();
330 let entry_fn = tcx.sess.entry_fn.borrow().map(|(node_id, _)| {
331 tcx.hir.local_def_id(node_id)
334 debug!("collect_roots: entry_fn = {:?}", entry_fn);
336 let mut visitor = RootCollector {
343 tcx.hir.krate().visit_all_item_likes(&mut visitor);
346 // We can only translate items that are instantiable - items all of
347 // whose predicates hold. Luckily, items that aren't instantiable
348 // can't actually be used, so we can just skip translating them.
349 roots.retain(|root| root.is_instantiable(tcx));
354 // Collect all monomorphized items reachable from `starting_point`
355 fn collect_items_rec<'a, 'tcx: 'a>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
356 starting_point: MonoItem<'tcx>,
357 visited: &mut FxHashSet<MonoItem<'tcx>>,
358 recursion_depths: &mut DefIdMap<usize>,
359 inlining_map: &mut InliningMap<'tcx>) {
360 if !visited.insert(starting_point.clone()) {
361 // We've been here already, no need to search again.
364 debug!("BEGIN collect_items_rec({})", starting_point.to_string(tcx));
366 let mut neighbors = Vec::new();
367 let recursion_depth_reset;
369 match starting_point {
370 MonoItem::Static(def_id) => {
371 let instance = Instance::mono(tcx, def_id);
373 // Sanity check whether this ended up being collected accidentally
374 debug_assert!(should_monomorphize_locally(tcx, &instance));
376 let ty = instance.ty(tcx);
377 visit_drop_use(tcx, ty, true, &mut neighbors);
379 recursion_depth_reset = None;
385 let param_env = ty::ParamEnv::reveal_all();
387 match tcx.const_eval(param_env.and(cid)) {
388 Ok(val) => collect_const(tcx, val, instance.substs, &mut neighbors),
390 let span = tcx.def_span(def_id);
391 err.report(tcx, span, "static");
395 MonoItem::Fn(instance) => {
396 // Sanity check whether this ended up being collected accidentally
397 debug_assert!(should_monomorphize_locally(tcx, &instance));
399 // Keep track of the monomorphization recursion depth
400 recursion_depth_reset = Some(check_recursion_limit(tcx,
403 check_type_length_limit(tcx, instance);
405 collect_neighbours(tcx, instance, &mut neighbors);
407 MonoItem::GlobalAsm(..) => {
408 recursion_depth_reset = None;
412 record_accesses(tcx, starting_point, &neighbors[..], inlining_map);
414 for neighbour in neighbors {
415 collect_items_rec(tcx, neighbour, visited, recursion_depths, inlining_map);
418 if let Some((def_id, depth)) = recursion_depth_reset {
419 recursion_depths.insert(def_id, depth);
422 debug!("END collect_items_rec({})", starting_point.to_string(tcx));
425 fn record_accesses<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
426 caller: MonoItem<'tcx>,
427 callees: &[MonoItem<'tcx>],
428 inlining_map: &mut InliningMap<'tcx>) {
429 let is_inlining_candidate = |mono_item: &MonoItem<'tcx>| {
430 mono_item.instantiation_mode(tcx) == InstantiationMode::LocalCopy
433 let accesses = callees.into_iter()
435 (*mono_item, is_inlining_candidate(mono_item))
438 inlining_map.record_accesses(caller, accesses);
441 fn check_recursion_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
442 instance: Instance<'tcx>,
443 recursion_depths: &mut DefIdMap<usize>)
445 let def_id = instance.def_id();
446 let recursion_depth = recursion_depths.get(&def_id).cloned().unwrap_or(0);
447 debug!(" => recursion depth={}", recursion_depth);
449 let recursion_depth = if Some(def_id) == tcx.lang_items().drop_in_place_fn() {
450 // HACK: drop_in_place creates tight monomorphization loops. Give
457 // Code that needs to instantiate the same function recursively
458 // more than the recursion limit is assumed to be causing an
459 // infinite expansion.
460 if recursion_depth > tcx.sess.recursion_limit.get() {
461 let error = format!("reached the recursion limit while instantiating `{}`",
463 if let Some(node_id) = tcx.hir.as_local_node_id(def_id) {
464 tcx.sess.span_fatal(tcx.hir.span(node_id), &error);
466 tcx.sess.fatal(&error);
470 recursion_depths.insert(def_id, recursion_depth + 1);
472 (def_id, recursion_depth)
475 fn check_type_length_limit<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
476 instance: Instance<'tcx>)
478 let type_length = instance.substs.types().flat_map(|ty| ty.walk()).count();
479 debug!(" => type length={}", type_length);
481 // Rust code can easily create exponentially-long types using only a
482 // polynomial recursion depth. Even with the default recursion
483 // depth, you can easily get cases that take >2^60 steps to run,
484 // which means that rustc basically hangs.
486 // Bail out in these cases to avoid that bad user experience.
487 let type_length_limit = tcx.sess.type_length_limit.get();
488 if type_length > type_length_limit {
489 // The instance name is already known to be too long for rustc. Use
490 // `{:.64}` to avoid blasting the user's terminal with thousands of
491 // lines of type-name.
492 let instance_name = instance.to_string();
493 let msg = format!("reached the type-length limit while instantiating `{:.64}...`",
495 let mut diag = if let Some(node_id) = tcx.hir.as_local_node_id(instance.def_id()) {
496 tcx.sess.struct_span_fatal(tcx.hir.span(node_id), &msg)
498 tcx.sess.struct_fatal(&msg)
502 "consider adding a `#![type_length_limit=\"{}\"]` attribute to your crate",
503 type_length_limit*2));
505 tcx.sess.abort_if_errors();
509 struct MirNeighborCollector<'a, 'tcx: 'a> {
510 tcx: TyCtxt<'a, 'tcx, 'tcx>,
511 mir: &'a mir::Mir<'tcx>,
512 output: &'a mut Vec<MonoItem<'tcx>>,
513 param_substs: &'tcx Substs<'tcx>,
516 impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
518 fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: Location) {
519 debug!("visiting rvalue {:?}", *rvalue);
522 // When doing an cast from a regular pointer to a fat pointer, we
523 // have to instantiate all methods of the trait being cast to, so we
524 // can build the appropriate vtable.
525 mir::Rvalue::Cast(mir::CastKind::Unsize, ref operand, target_ty) => {
526 let target_ty = self.tcx.trans_apply_param_substs(self.param_substs,
528 let source_ty = operand.ty(self.mir, self.tcx);
529 let source_ty = self.tcx.trans_apply_param_substs(self.param_substs,
531 let (source_ty, target_ty) = find_vtable_types_for_unsizing(self.tcx,
534 // This could also be a different Unsize instruction, like
535 // from a fixed sized array to a slice. But we are only
536 // interested in things that produce a vtable.
537 if target_ty.is_trait() && !source_ty.is_trait() {
538 create_mono_items_for_vtable_methods(self.tcx,
544 mir::Rvalue::Cast(mir::CastKind::ReifyFnPointer, ref operand, _) => {
545 let fn_ty = operand.ty(self.mir, self.tcx);
546 let fn_ty = self.tcx.trans_apply_param_substs(self.param_substs,
548 visit_fn_use(self.tcx, fn_ty, false, &mut self.output);
550 mir::Rvalue::Cast(mir::CastKind::ClosureFnPointer, ref operand, _) => {
551 let source_ty = operand.ty(self.mir, self.tcx);
552 let source_ty = self.tcx.trans_apply_param_substs(self.param_substs,
554 match source_ty.sty {
555 ty::TyClosure(def_id, substs) => {
556 let instance = monomorphize::resolve_closure(
557 self.tcx, def_id, substs, ty::ClosureKind::FnOnce);
558 self.output.push(create_fn_mono_item(instance));
563 mir::Rvalue::NullaryOp(mir::NullOp::Box, _) => {
565 let exchange_malloc_fn_def_id = tcx
567 .require(ExchangeMallocFnLangItem)
568 .unwrap_or_else(|e| tcx.sess.fatal(&e));
569 let instance = Instance::mono(tcx, exchange_malloc_fn_def_id);
570 if should_monomorphize_locally(tcx, &instance) {
571 self.output.push(create_fn_mono_item(instance));
574 _ => { /* not interesting */ }
577 self.super_rvalue(rvalue, location);
580 fn visit_const(&mut self, constant: &&'tcx ty::Const<'tcx>, location: Location) {
581 debug!("visiting const {:?} @ {:?}", *constant, location);
583 collect_const(self.tcx, constant, self.param_substs, self.output);
585 self.super_const(constant);
588 fn visit_terminator_kind(&mut self,
589 block: mir::BasicBlock,
590 kind: &mir::TerminatorKind<'tcx>,
591 location: Location) {
592 debug!("visiting terminator {:?} @ {:?}", kind, location);
596 mir::TerminatorKind::Call { ref func, .. } => {
597 let callee_ty = func.ty(self.mir, tcx);
598 let callee_ty = tcx.trans_apply_param_substs(self.param_substs, &callee_ty);
599 visit_fn_use(self.tcx, callee_ty, true, &mut self.output);
601 mir::TerminatorKind::Drop { ref location, .. } |
602 mir::TerminatorKind::DropAndReplace { ref location, .. } => {
603 let ty = location.ty(self.mir, self.tcx)
605 let ty = tcx.trans_apply_param_substs(self.param_substs, &ty);
606 visit_drop_use(self.tcx, ty, true, self.output);
608 mir::TerminatorKind::Goto { .. } |
609 mir::TerminatorKind::SwitchInt { .. } |
610 mir::TerminatorKind::Resume |
611 mir::TerminatorKind::Abort |
612 mir::TerminatorKind::Return |
613 mir::TerminatorKind::Unreachable |
614 mir::TerminatorKind::Assert { .. } => {}
615 mir::TerminatorKind::GeneratorDrop |
616 mir::TerminatorKind::Yield { .. } |
617 mir::TerminatorKind::FalseEdges { .. } |
618 mir::TerminatorKind::FalseUnwind { .. } => bug!(),
621 self.super_terminator_kind(block, kind, location);
624 fn visit_static(&mut self,
625 static_: &mir::Static<'tcx>,
626 context: mir::visit::PlaceContext<'tcx>,
627 location: Location) {
628 debug!("visiting static {:?} @ {:?}", static_.def_id, location);
631 let instance = Instance::mono(tcx, static_.def_id);
632 if should_monomorphize_locally(tcx, &instance) {
633 self.output.push(MonoItem::Static(static_.def_id));
636 self.super_static(static_, context, location);
640 fn visit_drop_use<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
642 is_direct_call: bool,
643 output: &mut Vec<MonoItem<'tcx>>)
645 let instance = monomorphize::resolve_drop_in_place(tcx, ty);
646 visit_instance_use(tcx, instance, is_direct_call, output);
649 fn visit_fn_use<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
651 is_direct_call: bool,
652 output: &mut Vec<MonoItem<'tcx>>)
654 if let ty::TyFnDef(def_id, substs) = ty.sty {
655 let instance = ty::Instance::resolve(tcx,
656 ty::ParamEnv::reveal_all(),
659 visit_instance_use(tcx, instance, is_direct_call, output);
663 fn visit_instance_use<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
664 instance: ty::Instance<'tcx>,
665 is_direct_call: bool,
666 output: &mut Vec<MonoItem<'tcx>>)
668 debug!("visit_item_use({:?}, is_direct_call={:?})", instance, is_direct_call);
669 if !should_monomorphize_locally(tcx, &instance) {
674 ty::InstanceDef::Intrinsic(def_id) => {
676 bug!("intrinsic {:?} being reified", def_id);
679 ty::InstanceDef::Virtual(..) |
680 ty::InstanceDef::DropGlue(_, None) => {
681 // don't need to emit shim if we are calling directly.
683 output.push(create_fn_mono_item(instance));
686 ty::InstanceDef::DropGlue(_, Some(_)) => {
687 output.push(create_fn_mono_item(instance));
689 ty::InstanceDef::ClosureOnceShim { .. } |
690 ty::InstanceDef::Item(..) |
691 ty::InstanceDef::FnPtrShim(..) |
692 ty::InstanceDef::CloneShim(..) => {
693 output.push(create_fn_mono_item(instance));
698 // Returns true if we should translate an instance in the local crate.
699 // Returns false if we can just link to the upstream crate and therefore don't
701 fn should_monomorphize_locally<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, instance: &Instance<'tcx>)
703 let def_id = match instance.def {
704 ty::InstanceDef::Item(def_id) => def_id,
705 ty::InstanceDef::ClosureOnceShim { .. } |
706 ty::InstanceDef::Virtual(..) |
707 ty::InstanceDef::FnPtrShim(..) |
708 ty::InstanceDef::DropGlue(..) |
709 ty::InstanceDef::Intrinsic(_) |
710 ty::InstanceDef::CloneShim(..) => return true
712 match tcx.hir.get_if_local(def_id) {
713 Some(hir_map::NodeForeignItem(..)) => {
714 false // foreign items are linked against, not translated.
718 if tcx.is_reachable_non_generic(def_id) ||
719 tcx.is_foreign_item(def_id)
721 // We can link to the item in question, no instance needed
725 if !tcx.is_mir_available(def_id) {
726 bug!("Cannot create local mono-item for {:?}", def_id)
734 /// For given pair of source and target type that occur in an unsizing coercion,
735 /// this function finds the pair of types that determines the vtable linking
738 /// For example, the source type might be `&SomeStruct` and the target type\
739 /// might be `&SomeTrait` in a cast like:
741 /// let src: &SomeStruct = ...;
742 /// let target = src as &SomeTrait;
744 /// Then the output of this function would be (SomeStruct, SomeTrait) since for
745 /// constructing the `target` fat-pointer we need the vtable for that pair.
747 /// Things can get more complicated though because there's also the case where
748 /// the unsized type occurs as a field:
751 /// struct ComplexStruct<T: ?Sized> {
758 /// In this case, if `T` is sized, `&ComplexStruct<T>` is a thin pointer. If `T`
759 /// is unsized, `&SomeStruct` is a fat pointer, and the vtable it points to is
760 /// for the pair of `T` (which is a trait) and the concrete type that `T` was
761 /// originally coerced from:
763 /// let src: &ComplexStruct<SomeStruct> = ...;
764 /// let target = src as &ComplexStruct<SomeTrait>;
766 /// Again, we want this `find_vtable_types_for_unsizing()` to provide the pair
767 /// `(SomeStruct, SomeTrait)`.
769 /// Finally, there is also the case of custom unsizing coercions, e.g. for
770 /// smart pointers such as `Rc` and `Arc`.
771 fn find_vtable_types_for_unsizing<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
774 -> (Ty<'tcx>, Ty<'tcx>) {
775 let ptr_vtable = |inner_source: Ty<'tcx>, inner_target: Ty<'tcx>| {
776 let type_has_metadata = |ty: Ty<'tcx>| -> bool {
777 use syntax_pos::DUMMY_SP;
778 if ty.is_sized(tcx.at(DUMMY_SP), ty::ParamEnv::reveal_all()) {
781 let tail = tcx.struct_tail(ty);
783 ty::TyForeign(..) => false,
784 ty::TyStr | ty::TySlice(..) | ty::TyDynamic(..) => true,
785 _ => bug!("unexpected unsized tail: {:?}", tail.sty),
788 if type_has_metadata(inner_source) {
789 (inner_source, inner_target)
791 tcx.struct_lockstep_tails(inner_source, inner_target)
795 match (&source_ty.sty, &target_ty.sty) {
796 (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
797 &ty::TyRef(_, ty::TypeAndMut { ty: b, .. })) |
798 (&ty::TyRef(_, ty::TypeAndMut { ty: a, .. }),
799 &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) |
800 (&ty::TyRawPtr(ty::TypeAndMut { ty: a, .. }),
801 &ty::TyRawPtr(ty::TypeAndMut { ty: b, .. })) => {
804 (&ty::TyAdt(def_a, _), &ty::TyAdt(def_b, _)) if def_a.is_box() && def_b.is_box() => {
805 ptr_vtable(source_ty.boxed_ty(), target_ty.boxed_ty())
808 (&ty::TyAdt(source_adt_def, source_substs),
809 &ty::TyAdt(target_adt_def, target_substs)) => {
810 assert_eq!(source_adt_def, target_adt_def);
813 monomorphize::custom_coerce_unsize_info(tcx, source_ty, target_ty);
815 let coerce_index = match kind {
816 CustomCoerceUnsized::Struct(i) => i
819 let source_fields = &source_adt_def.non_enum_variant().fields;
820 let target_fields = &target_adt_def.non_enum_variant().fields;
822 assert!(coerce_index < source_fields.len() &&
823 source_fields.len() == target_fields.len());
825 find_vtable_types_for_unsizing(tcx,
826 source_fields[coerce_index].ty(tcx,
828 target_fields[coerce_index].ty(tcx,
831 _ => bug!("find_vtable_types_for_unsizing: invalid coercion {:?} -> {:?}",
837 fn create_fn_mono_item<'a, 'tcx>(instance: Instance<'tcx>) -> MonoItem<'tcx> {
838 debug!("create_fn_mono_item(instance={})", instance);
839 MonoItem::Fn(instance)
842 /// Creates a `MonoItem` for each method that is referenced by the vtable for
843 /// the given trait/impl pair.
844 fn create_mono_items_for_vtable_methods<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
847 output: &mut Vec<MonoItem<'tcx>>) {
848 assert!(!trait_ty.needs_subst() && !trait_ty.has_escaping_regions() &&
849 !impl_ty.needs_subst() && !impl_ty.has_escaping_regions());
851 if let ty::TyDynamic(ref trait_ty, ..) = trait_ty.sty {
852 if let Some(principal) = trait_ty.principal() {
853 let poly_trait_ref = principal.with_self_ty(tcx, impl_ty);
854 assert!(!poly_trait_ref.has_escaping_regions());
856 // Walk all methods of the trait, including those of its supertraits
857 let methods = tcx.vtable_methods(poly_trait_ref);
858 let methods = methods.iter().cloned().filter_map(|method| method)
859 .map(|(def_id, substs)| ty::Instance::resolve(
861 ty::ParamEnv::reveal_all(),
864 .filter(|&instance| should_monomorphize_locally(tcx, &instance))
865 .map(|instance| create_fn_mono_item(instance));
866 output.extend(methods);
868 // Also add the destructor
869 visit_drop_use(tcx, impl_ty, false, output);
873 //=-----------------------------------------------------------------------------
875 //=-----------------------------------------------------------------------------
877 struct RootCollector<'b, 'a: 'b, 'tcx: 'a + 'b> {
878 tcx: TyCtxt<'a, 'tcx, 'tcx>,
879 mode: MonoItemCollectionMode,
880 output: &'b mut Vec<MonoItem<'tcx>>,
881 entry_fn: Option<DefId>,
884 impl<'b, 'a, 'v> ItemLikeVisitor<'v> for RootCollector<'b, 'a, 'v> {
885 fn visit_item(&mut self, item: &'v hir::Item) {
887 hir::ItemExternCrate(..) |
889 hir::ItemForeignMod(..) |
892 hir::ItemTraitAlias(..) |
893 hir::ItemMod(..) => {
894 // Nothing to do, just keep recursing...
897 hir::ItemImpl(..) => {
898 if self.mode == MonoItemCollectionMode::Eager {
899 create_mono_items_for_default_impls(self.tcx,
905 hir::ItemEnum(_, ref generics) |
906 hir::ItemStruct(_, ref generics) |
907 hir::ItemUnion(_, ref generics) => {
908 if generics.params.is_empty() {
909 if self.mode == MonoItemCollectionMode::Eager {
910 let def_id = self.tcx.hir.local_def_id(item.id);
911 debug!("RootCollector: ADT drop-glue for {}",
912 def_id_to_string(self.tcx, def_id));
914 let ty = Instance::new(def_id, Substs::empty()).ty(self.tcx);
915 visit_drop_use(self.tcx, ty, true, self.output);
919 hir::ItemGlobalAsm(..) => {
920 debug!("RootCollector: ItemGlobalAsm({})",
921 def_id_to_string(self.tcx,
922 self.tcx.hir.local_def_id(item.id)));
923 self.output.push(MonoItem::GlobalAsm(item.id));
925 hir::ItemStatic(..) => {
926 let def_id = self.tcx.hir.local_def_id(item.id);
927 debug!("RootCollector: ItemStatic({})",
928 def_id_to_string(self.tcx, def_id));
929 self.output.push(MonoItem::Static(def_id));
931 hir::ItemConst(..) => {
932 // const items only generate mono items if they are
933 // actually used somewhere. Just declaring them is insufficient.
936 let def_id = self.tcx.hir.local_def_id(item.id);
937 self.push_if_root(def_id);
942 fn visit_trait_item(&mut self, _: &'v hir::TraitItem) {
943 // Even if there's a default body with no explicit generics,
944 // it's still generic over some `Self: Trait`, so not a root.
947 fn visit_impl_item(&mut self, ii: &'v hir::ImplItem) {
949 hir::ImplItemKind::Method(hir::MethodSig { .. }, _) => {
950 let def_id = self.tcx.hir.local_def_id(ii.id);
951 self.push_if_root(def_id);
953 _ => { /* Nothing to do here */ }
958 impl<'b, 'a, 'v> RootCollector<'b, 'a, 'v> {
959 fn is_root(&self, def_id: DefId) -> bool {
960 !item_has_type_parameters(self.tcx, def_id) && match self.mode {
961 MonoItemCollectionMode::Eager => {
964 MonoItemCollectionMode::Lazy => {
965 self.entry_fn == Some(def_id) ||
966 self.tcx.is_reachable_non_generic(def_id) ||
967 self.tcx.trans_fn_attrs(def_id).flags.contains(
968 TransFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL)
973 /// If `def_id` represents a root, then push it onto the list of
974 /// outputs. (Note that all roots must be monomorphic.)
975 fn push_if_root(&mut self, def_id: DefId) {
976 if self.is_root(def_id) {
977 debug!("RootCollector::push_if_root: found root def_id={:?}", def_id);
979 let instance = Instance::mono(self.tcx, def_id);
980 self.output.push(create_fn_mono_item(instance));
982 self.push_extra_entry_roots(def_id);
986 /// As a special case, when/if we encounter the
987 /// `main()` function, we also have to generate a
988 /// monomorphized copy of the start lang item based on
989 /// the return type of `main`. This is not needed when
990 /// the user writes their own `start` manually.
991 fn push_extra_entry_roots(&mut self, def_id: DefId) {
992 if self.entry_fn != Some(def_id) {
996 if self.tcx.sess.entry_type.get() != Some(config::EntryMain) {
1000 let start_def_id = match self.tcx.lang_items().require(StartFnLangItem) {
1002 Err(err) => self.tcx.sess.fatal(&err),
1004 let main_ret_ty = self.tcx.fn_sig(def_id).output();
1006 // Given that `main()` has no arguments,
1007 // then its return type cannot have
1008 // late-bound regions, since late-bound
1009 // regions must appear in the argument
1011 let main_ret_ty = main_ret_ty.no_late_bound_regions().unwrap();
1013 let start_instance = Instance::resolve(
1015 ty::ParamEnv::reveal_all(),
1017 self.tcx.mk_substs(iter::once(Kind::from(main_ret_ty)))
1020 self.output.push(create_fn_mono_item(start_instance));
1024 fn item_has_type_parameters<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>, def_id: DefId) -> bool {
1025 let generics = tcx.generics_of(def_id);
1026 generics.parent_types as usize + generics.types.len() > 0
1029 fn create_mono_items_for_default_impls<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1030 item: &'tcx hir::Item,
1031 output: &mut Vec<MonoItem<'tcx>>) {
1038 ref impl_item_refs) => {
1039 if generics.is_type_parameterized() {
1043 let impl_def_id = tcx.hir.local_def_id(item.id);
1045 debug!("create_mono_items_for_default_impls(item={})",
1046 def_id_to_string(tcx, impl_def_id));
1048 if let Some(trait_ref) = tcx.impl_trait_ref(impl_def_id) {
1049 let callee_substs = tcx.erase_regions(&trait_ref.substs);
1050 let overridden_methods: FxHashSet<_> =
1051 impl_item_refs.iter()
1052 .map(|iiref| iiref.name)
1054 for method in tcx.provided_trait_methods(trait_ref.def_id) {
1055 if overridden_methods.contains(&method.name) {
1059 if !tcx.generics_of(method.def_id).types.is_empty() {
1063 let instance = ty::Instance::resolve(tcx,
1064 ty::ParamEnv::reveal_all(),
1066 callee_substs).unwrap();
1068 let mono_item = create_fn_mono_item(instance);
1069 if mono_item.is_instantiable(tcx)
1070 && should_monomorphize_locally(tcx, &instance) {
1071 output.push(mono_item);
1082 /// Scan the miri alloc in order to find function calls, closures, and drop-glue
1083 fn collect_miri<'a, 'tcx>(
1084 tcx: TyCtxt<'a, 'tcx, 'tcx>,
1086 output: &mut Vec<MonoItem<'tcx>>,
1088 if let Some(did) = tcx.interpret_interner.get_corresponding_static_def_id(alloc_id) {
1089 let instance = Instance::mono(tcx, did);
1090 if should_monomorphize_locally(tcx, &instance) {
1091 trace!("collecting static {:?}", did);
1092 output.push(MonoItem::Static(did));
1094 } else if let Some(alloc) = tcx.interpret_interner.get_alloc(alloc_id) {
1095 trace!("collecting {:?} with {:#?}", alloc_id, alloc);
1096 for &inner in alloc.relocations.values() {
1097 collect_miri(tcx, inner, output);
1099 } else if let Some(fn_instance) = tcx.interpret_interner.get_fn(alloc_id) {
1100 if should_monomorphize_locally(tcx, &fn_instance) {
1101 trace!("collecting {:?} with {:#?}", alloc_id, fn_instance);
1102 output.push(create_fn_mono_item(fn_instance));
1105 bug!("alloc id without corresponding allocation: {}", alloc_id);
1109 /// Scan the MIR in order to find function calls, closures, and drop-glue
1110 fn collect_neighbours<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1111 instance: Instance<'tcx>,
1112 output: &mut Vec<MonoItem<'tcx>>)
1114 let mir = tcx.instance_mir(instance.def);
1116 MirNeighborCollector {
1120 param_substs: instance.substs,
1122 let param_env = ty::ParamEnv::reveal_all();
1123 for (i, promoted) in mir.promoted.iter().enumerate() {
1124 use rustc_data_structures::indexed_vec::Idx;
1125 let cid = GlobalId {
1127 promoted: Some(Promoted::new(i)),
1129 match tcx.const_eval(param_env.and(cid)) {
1130 Ok(val) => collect_const(tcx, val, instance.substs, output),
1132 err.report(tcx, promoted.span, "promoted");
1138 fn def_id_to_string<'a, 'tcx>(tcx: TyCtxt<'a, 'tcx, 'tcx>,
1141 let mut output = String::new();
1142 let printer = DefPathBasedNames::new(tcx, false, false);
1143 printer.push_def_path(def_id, &mut output);
1147 fn collect_const<'a, 'tcx>(
1148 tcx: TyCtxt<'a, 'tcx, 'tcx>,
1149 constant: &ty::Const<'tcx>,
1150 param_substs: &'tcx Substs<'tcx>,
1151 output: &mut Vec<MonoItem<'tcx>>,
1153 debug!("visiting const {:?}", *constant);
1155 let val = match constant.val {
1156 ConstVal::Unevaluated(def_id, substs) => {
1157 let param_env = ty::ParamEnv::reveal_all();
1158 let substs = tcx.trans_apply_param_substs(param_substs,
1160 let instance = ty::Instance::resolve(tcx,
1165 let cid = GlobalId {
1169 match tcx.const_eval(param_env.and(cid)) {
1172 let span = tcx.def_span(def_id);
1173 err.report(tcx, span, "constant");
1181 ConstVal::Unevaluated(..) => bug!("const eval yielded unevaluated const"),
1182 ConstVal::Value(Value::ByValPair(PrimVal::Ptr(a), PrimVal::Ptr(b))) => {
1183 collect_miri(tcx, a.alloc_id, output);
1184 collect_miri(tcx, b.alloc_id, output);
1186 ConstVal::Value(Value::ByValPair(_, PrimVal::Ptr(ptr))) |
1187 ConstVal::Value(Value::ByValPair(PrimVal::Ptr(ptr), _)) |
1188 ConstVal::Value(Value::ByVal(PrimVal::Ptr(ptr))) =>
1189 collect_miri(tcx, ptr.alloc_id, output),
1190 ConstVal::Value(Value::ByRef(Pointer { primval: PrimVal::Ptr(ptr) }, _)) => {
1191 // by ref should only collect the inner allocation, not the value itself
1194 .get_alloc(ptr.alloc_id)
1195 .expect("ByRef to extern static is not allowed");
1196 for &inner in alloc.relocations.values() {
1197 collect_miri(tcx, inner, output);