1 //! Mono Item Collection
2 //! ====================
4 //! This module is responsible for discovering all items that will contribute
5 //! to code generation of the crate. The important part here is that it not only
6 //! needs to find syntax-level items (functions, structs, etc) but also all
7 //! their monomorphized instantiations. Every non-generic, non-const function
8 //! maps to one LLVM artifact. Every generic function can produce
9 //! from zero to N artifacts, depending on the sets of type arguments it
10 //! is instantiated with.
11 //! This also applies to generic items from other crates: A generic definition
12 //! in crate X might produce monomorphizations that are compiled into crate Y.
13 //! We also have to collect these here.
15 //! The following kinds of "mono items" are handled here:
23 //! The following things also result in LLVM artifacts, but are not collected
24 //! here, since we instantiate them locally on demand when needed in a given
34 //! Let's define some terms first:
36 //! - A "mono item" is something that results in a function or global in
37 //! the LLVM IR of a codegen unit. Mono items do not stand on their
38 //! own, they can reference other mono items. For example, if function
39 //! `foo()` calls function `bar()` then the mono item for `foo()`
40 //! references the mono item for function `bar()`. In general, the
41 //! definition for mono item A referencing a mono item B is that
42 //! the LLVM artifact produced for A references the LLVM artifact produced
45 //! - Mono items and the references between them form a directed graph,
46 //! where the mono items are the nodes and references form the edges.
47 //! Let's call this graph the "mono item graph".
49 //! - The mono item graph for a program contains all mono items
50 //! that are needed in order to produce the complete LLVM IR of the program.
52 //! The purpose of the algorithm implemented in this module is to build the
53 //! mono item graph for the current crate. It runs in two phases:
55 //! 1. Discover the roots of the graph by traversing the HIR of the crate.
56 //! 2. Starting from the roots, find neighboring nodes by inspecting the MIR
57 //! representation of the item corresponding to a given node, until no more
58 //! new nodes are found.
60 //! ### Discovering roots
62 //! The roots of the mono item graph correspond to the public non-generic
63 //! syntactic items in the source code. We find them by walking the HIR of the
64 //! crate, and whenever we hit upon a public function, method, or static item,
65 //! we create a mono item consisting of the items DefId and, since we only
66 //! consider non-generic items, an empty type-substitution set. (In eager
67 //! collection mode, during incremental compilation, all non-generic functions
68 //! are considered as roots, as well as when the `-Clink-dead-code` option is
69 //! specified. Functions marked `#[no_mangle]` and functions called by inlinable
70 //! functions also always act as roots.)
72 //! ### Finding neighbor nodes
73 //! Given a mono item node, we can discover neighbors by inspecting its
74 //! MIR. We walk the MIR and any time we hit upon something that signifies a
75 //! reference to another mono item, we have found a neighbor. Since the
76 //! mono item we are currently at is always monomorphic, we also know the
77 //! concrete type arguments of its neighbors, and so all neighbors again will be
78 //! monomorphic. The specific forms a reference to a neighboring node can take
79 //! in MIR are quite diverse. Here is an overview:
81 //! #### Calling Functions/Methods
82 //! The most obvious form of one mono item referencing another is a
83 //! function or method call (represented by a CALL terminator in MIR). But
84 //! calls are not the only thing that might introduce a reference between two
85 //! function mono items, and as we will see below, they are just a
86 //! specialization of the form described next, and consequently will not get any
87 //! special treatment in the algorithm.
89 //! #### Taking a reference to a function or method
90 //! A function does not need to actually be called in order to be a neighbor of
91 //! another function. It suffices to just take a reference in order to introduce
92 //! an edge. Consider the following example:
95 //! # use core::fmt::Display;
96 //! fn print_val<T: Display>(x: T) {
97 //! println!("{}", x);
100 //! fn call_fn(f: &dyn Fn(i32), x: i32) {
105 //! let print_i32 = print_val::<i32>;
106 //! call_fn(&print_i32, 0);
109 //! The MIR of none of these functions will contain an explicit call to
110 //! `print_val::<i32>`. Nonetheless, in order to mono this program, we need
111 //! an instance of this function. Thus, whenever we encounter a function or
112 //! method in operand position, we treat it as a neighbor of the current
113 //! mono item. Calls are just a special case of that.
116 //! In a way, closures are a simple case. Since every closure object needs to be
117 //! constructed somewhere, we can reliably discover them by observing
118 //! `RValue::Aggregate` expressions with `AggregateKind::Closure`. This is also
119 //! true for closures inlined from other crates.
122 //! Drop glue mono items are introduced by MIR drop-statements. The
123 //! generated mono item will again have drop-glue item neighbors if the
124 //! type to be dropped contains nested values that also need to be dropped. It
125 //! might also have a function item neighbor for the explicit `Drop::drop`
126 //! implementation of its type.
128 //! #### Unsizing Casts
129 //! A subtle way of introducing neighbor edges is by casting to a trait object.
130 //! Since the resulting fat-pointer contains a reference to a vtable, we need to
131 //! instantiate all object-safe methods of the trait, as we need to store
132 //! pointers to these functions even if they never get called anywhere. This can
133 //! be seen as a special case of taking a function reference.
136 //! Since `Box` expression have special compiler support, no explicit calls to
137 //! `exchange_malloc()` and `box_free()` may show up in MIR, even if the
138 //! compiler will generate them. We have to observe `Rvalue::Box` expressions
139 //! and Box-typed drop-statements for that purpose.
142 //! Interaction with Cross-Crate Inlining
143 //! -------------------------------------
144 //! The binary of a crate will not only contain machine code for the items
145 //! defined in the source code of that crate. It will also contain monomorphic
146 //! instantiations of any extern generic functions and of functions marked with
148 //! The collection algorithm handles this more or less mono. If it is
149 //! about to create a mono item for something with an external `DefId`,
150 //! it will take a look if the MIR for that item is available, and if so just
151 //! proceed normally. If the MIR is not available, it assumes that the item is
152 //! just linked to and no node is created; which is exactly what we want, since
153 //! no machine code should be generated in the current crate for such an item.
155 //! Eager and Lazy Collection Mode
156 //! ------------------------------
157 //! Mono item collection can be performed in one of two modes:
159 //! - Lazy mode means that items will only be instantiated when actually
160 //! referenced. The goal is to produce the least amount of machine code
163 //! - Eager mode is meant to be used in conjunction with incremental compilation
164 //! where a stable set of mono items is more important than a minimal
165 //! one. Thus, eager mode will instantiate drop-glue for every drop-able type
166 //! in the crate, even if no drop call for that type exists (yet). It will
167 //! also instantiate default implementations of trait methods, something that
168 //! otherwise is only done on demand.
173 //! Some things are not yet fully implemented in the current version of this
177 //! Ideally, no mono item should be generated for const fns unless there
178 //! is a call to them that cannot be evaluated at compile time. At the moment
179 //! this is not implemented however: a mono item will be produced
180 //! regardless of whether it is actually needed or not.
182 use rustc_data_structures::fx::{FxHashMap, FxHashSet};
183 use rustc_data_structures::sync::{par_for_each_in, MTLock, MTRef};
184 use rustc_hir as hir;
185 use rustc_hir::def::DefKind;
186 use rustc_hir::def_id::{DefId, DefIdMap, LocalDefId};
187 use rustc_hir::lang_items::LangItem;
188 use rustc_index::bit_set::GrowableBitSet;
189 use rustc_middle::mir::interpret::{AllocId, ConstValue};
190 use rustc_middle::mir::interpret::{ErrorHandled, GlobalAlloc, Scalar};
191 use rustc_middle::mir::mono::{InstantiationMode, MonoItem};
192 use rustc_middle::mir::visit::Visitor as MirVisitor;
193 use rustc_middle::mir::{self, Local, Location};
194 use rustc_middle::ty::adjustment::{CustomCoerceUnsized, PointerCast};
195 use rustc_middle::ty::print::with_no_trimmed_paths;
196 use rustc_middle::ty::subst::{GenericArgKind, InternalSubsts};
197 use rustc_middle::ty::{
198 self, GenericParamDefKind, Instance, Ty, TyCtxt, TypeFoldable, TypeVisitable, VtblEntry,
200 use rustc_middle::{middle::codegen_fn_attrs::CodegenFnAttrFlags, mir::visit::TyContext};
201 use rustc_session::config::EntryFnType;
202 use rustc_session::lint::builtin::LARGE_ASSIGNMENTS;
203 use rustc_session::Limit;
204 use rustc_span::source_map::{dummy_spanned, respan, Span, Spanned, DUMMY_SP};
205 use rustc_target::abi::Size;
208 use std::path::PathBuf;
210 use crate::errors::{LargeAssignmentsLint, RecursionLimit, RequiresLangItem, TypeLengthLimit};
213 pub enum MonoItemCollectionMode {
218 /// Maps every mono item to all mono items it references in its
220 pub struct InliningMap<'tcx> {
221 // Maps a source mono item to the range of mono items
223 // The range selects elements within the `targets` vecs.
224 index: FxHashMap<MonoItem<'tcx>, Range<usize>>,
225 targets: Vec<MonoItem<'tcx>>,
227 // Contains one bit per mono item in the `targets` field. That bit
228 // is true if that mono item needs to be inlined into every CGU.
229 inlines: GrowableBitSet<usize>,
232 /// Struct to store mono items in each collecting and if they should
233 /// be inlined. We call `instantiation_mode` to get their inlining
234 /// status when inserting new elements, which avoids calling it in
235 /// `inlining_map.lock_mut()`. See the `collect_items_rec` implementation
237 struct MonoItems<'tcx> {
238 // If this is false, we do not need to compute whether items
239 // will need to be inlined.
240 compute_inlining: bool,
242 // The TyCtxt used to determine whether the a item should
246 // The collected mono items. The bool field in each element
247 // indicates whether this element should be inlined.
248 items: Vec<(Spanned<MonoItem<'tcx>>, bool /*inlined*/)>,
251 impl<'tcx> MonoItems<'tcx> {
253 fn push(&mut self, item: Spanned<MonoItem<'tcx>>) {
258 fn extend<T: IntoIterator<Item = Spanned<MonoItem<'tcx>>>>(&mut self, iter: T) {
259 self.items.extend(iter.into_iter().map(|mono_item| {
260 let inlined = if !self.compute_inlining {
263 mono_item.node.instantiation_mode(self.tcx) == InstantiationMode::LocalCopy
270 impl<'tcx> InliningMap<'tcx> {
271 fn new() -> InliningMap<'tcx> {
273 index: FxHashMap::default(),
275 inlines: GrowableBitSet::with_capacity(1024),
279 fn record_accesses<'a>(
281 source: MonoItem<'tcx>,
282 new_targets: &'a [(Spanned<MonoItem<'tcx>>, bool)],
286 let start_index = self.targets.len();
287 let new_items_count = new_targets.len();
288 let new_items_count_total = new_items_count + self.targets.len();
290 self.targets.reserve(new_items_count);
291 self.inlines.ensure(new_items_count_total);
293 for (i, (Spanned { node: mono_item, .. }, inlined)) in new_targets.into_iter().enumerate() {
294 self.targets.push(*mono_item);
296 self.inlines.insert(i + start_index);
300 let end_index = self.targets.len();
301 assert!(self.index.insert(source, start_index..end_index).is_none());
304 // Internally iterate over all items referenced by `source` which will be
305 // made available for inlining.
306 pub fn with_inlining_candidates<F>(&self, source: MonoItem<'tcx>, mut f: F)
308 F: FnMut(MonoItem<'tcx>),
310 if let Some(range) = self.index.get(&source) {
311 for (i, candidate) in self.targets[range.clone()].iter().enumerate() {
312 if self.inlines.contains(range.start + i) {
319 // Internally iterate over all items and the things each accesses.
320 pub fn iter_accesses<F>(&self, mut f: F)
322 F: FnMut(MonoItem<'tcx>, &[MonoItem<'tcx>]),
324 for (&accessor, range) in &self.index {
325 f(accessor, &self.targets[range.clone()])
330 #[instrument(skip(tcx, mode), level = "debug")]
331 pub fn collect_crate_mono_items(
333 mode: MonoItemCollectionMode,
334 ) -> (FxHashSet<MonoItem<'_>>, InliningMap<'_>) {
335 let _prof_timer = tcx.prof.generic_activity("monomorphization_collector");
338 tcx.sess.time("monomorphization_collector_root_collections", || collect_roots(tcx, mode));
340 debug!("building mono item graph, beginning at roots");
342 let mut visited = MTLock::new(FxHashSet::default());
343 let mut inlining_map = MTLock::new(InliningMap::new());
344 let recursion_limit = tcx.recursion_limit();
347 let visited: MTRef<'_, _> = &mut visited;
348 let inlining_map: MTRef<'_, _> = &mut inlining_map;
350 tcx.sess.time("monomorphization_collector_graph_walk", || {
351 par_for_each_in(roots, |root| {
352 let mut recursion_depths = DefIdMap::default();
357 &mut recursion_depths,
365 (visited.into_inner(), inlining_map.into_inner())
368 // Find all non-generic items by walking the HIR. These items serve as roots to
369 // start monomorphizing from.
370 #[instrument(skip(tcx, mode), level = "debug")]
371 fn collect_roots(tcx: TyCtxt<'_>, mode: MonoItemCollectionMode) -> Vec<MonoItem<'_>> {
372 debug!("collecting roots");
373 let mut roots = MonoItems { compute_inlining: false, tcx, items: Vec::new() };
376 let entry_fn = tcx.entry_fn(());
378 debug!("collect_roots: entry_fn = {:?}", entry_fn);
380 let mut collector = RootCollector { tcx, mode, entry_fn, output: &mut roots };
382 let crate_items = tcx.hir_crate_items(());
384 for id in crate_items.items() {
385 collector.process_item(id);
388 for id in crate_items.impl_items() {
389 collector.process_impl_item(id);
392 collector.push_extra_entry_roots();
395 // We can only codegen items that are instantiable - items all of
396 // whose predicates hold. Luckily, items that aren't instantiable
397 // can't actually be used, so we can just skip codegenning them.
401 .filter_map(|(Spanned { node: mono_item, .. }, _)| {
402 mono_item.is_instantiable(tcx).then_some(mono_item)
407 /// Collect all monomorphized items reachable from `starting_point`, and emit a note diagnostic if a
408 /// post-monorphization error is encountered during a collection step.
409 #[instrument(skip(tcx, visited, recursion_depths, recursion_limit, inlining_map), level = "debug")]
410 fn collect_items_rec<'tcx>(
412 starting_point: Spanned<MonoItem<'tcx>>,
413 visited: MTRef<'_, MTLock<FxHashSet<MonoItem<'tcx>>>>,
414 recursion_depths: &mut DefIdMap<usize>,
415 recursion_limit: Limit,
416 inlining_map: MTRef<'_, MTLock<InliningMap<'tcx>>>,
418 if !visited.lock_mut().insert(starting_point.node) {
419 // We've been here already, no need to search again.
423 let mut neighbors = MonoItems { compute_inlining: true, tcx, items: Vec::new() };
424 let recursion_depth_reset;
427 // Post-monomorphization errors MVP
429 // We can encounter errors while monomorphizing an item, but we don't have a good way of
430 // showing a complete stack of spans ultimately leading to collecting the erroneous one yet.
431 // (It's also currently unclear exactly which diagnostics and information would be interesting
432 // to report in such cases)
434 // This leads to suboptimal error reporting: a post-monomorphization error (PME) will be
435 // shown with just a spanned piece of code causing the error, without information on where
436 // it was called from. This is especially obscure if the erroneous mono item is in a
437 // dependency. See for example issue #85155, where, before minimization, a PME happened two
438 // crates downstream from libcore's stdarch, without a way to know which dependency was the
441 // If such an error occurs in the current crate, its span will be enough to locate the
442 // source. If the cause is in another crate, the goal here is to quickly locate which mono
443 // item in the current crate is ultimately responsible for causing the error.
445 // To give at least _some_ context to the user: while collecting mono items, we check the
446 // error count. If it has changed, a PME occurred, and we trigger some diagnostics about the
447 // current step of mono items collection.
449 // FIXME: don't rely on global state, instead bubble up errors. Note: this is very hard to do.
450 let error_count = tcx.sess.diagnostic().err_count();
452 match starting_point.node {
453 MonoItem::Static(def_id) => {
454 let instance = Instance::mono(tcx, def_id);
456 // Sanity check whether this ended up being collected accidentally
457 debug_assert!(should_codegen_locally(tcx, &instance));
459 let ty = instance.ty(tcx, ty::ParamEnv::reveal_all());
460 visit_drop_use(tcx, ty, true, starting_point.span, &mut neighbors);
462 recursion_depth_reset = None;
464 if let Ok(alloc) = tcx.eval_static_initializer(def_id) {
465 for &id in alloc.inner().provenance().values() {
466 collect_miri(tcx, id, &mut neighbors);
470 MonoItem::Fn(instance) => {
471 // Sanity check whether this ended up being collected accidentally
472 debug_assert!(should_codegen_locally(tcx, &instance));
474 // Keep track of the monomorphization recursion depth
475 recursion_depth_reset = Some(check_recursion_limit(
482 check_type_length_limit(tcx, instance);
484 rustc_data_structures::stack::ensure_sufficient_stack(|| {
485 collect_neighbours(tcx, instance, &mut neighbors);
488 MonoItem::GlobalAsm(item_id) => {
489 recursion_depth_reset = None;
491 let item = tcx.hir().item(item_id);
492 if let hir::ItemKind::GlobalAsm(asm) = item.kind {
493 for (op, op_sp) in asm.operands {
495 hir::InlineAsmOperand::Const { .. } => {
496 // Only constants which resolve to a plain integer
497 // are supported. Therefore the value should not
498 // depend on any other items.
500 hir::InlineAsmOperand::SymFn { anon_const } => {
502 tcx.typeck_body(anon_const.body).node_type(anon_const.hir_id);
503 visit_fn_use(tcx, fn_ty, false, *op_sp, &mut neighbors);
505 hir::InlineAsmOperand::SymStatic { path: _, def_id } => {
506 let instance = Instance::mono(tcx, *def_id);
507 if should_codegen_locally(tcx, &instance) {
508 trace!("collecting static {:?}", def_id);
509 neighbors.push(dummy_spanned(MonoItem::Static(*def_id)));
512 hir::InlineAsmOperand::In { .. }
513 | hir::InlineAsmOperand::Out { .. }
514 | hir::InlineAsmOperand::InOut { .. }
515 | hir::InlineAsmOperand::SplitInOut { .. } => {
516 span_bug!(*op_sp, "invalid operand type for global_asm!")
521 span_bug!(item.span, "Mismatch between hir::Item type and MonoItem type")
526 // Check for PMEs and emit a diagnostic if one happened. To try to show relevant edges of the
528 if tcx.sess.diagnostic().err_count() > error_count
529 && starting_point.node.is_generic_fn()
530 && starting_point.node.is_user_defined()
532 let formatted_item = with_no_trimmed_paths!(starting_point.node.to_string());
533 tcx.sess.span_note_without_error(
535 &format!("the above error was encountered while instantiating `{}`", formatted_item),
538 inlining_map.lock_mut().record_accesses(starting_point.node, &neighbors.items);
540 for (neighbour, _) in neighbors.items {
541 collect_items_rec(tcx, neighbour, visited, recursion_depths, recursion_limit, inlining_map);
544 if let Some((def_id, depth)) = recursion_depth_reset {
545 recursion_depths.insert(def_id, depth);
549 /// Format instance name that is already known to be too long for rustc.
550 /// Show only the first and last 32 characters to avoid blasting
551 /// the user's terminal with thousands of lines of type-name.
553 /// If the type name is longer than before+after, it will be written to a file.
554 fn shrunk_instance_name<'tcx>(
556 instance: &Instance<'tcx>,
559 ) -> (String, Option<PathBuf>) {
560 let s = instance.to_string();
562 // Only use the shrunk version if it's really shorter.
563 // This also avoids the case where before and after slices overlap.
564 if s.chars().nth(before + after + 1).is_some() {
565 // An iterator of all byte positions including the end of the string.
566 let positions = || s.char_indices().map(|(i, _)| i).chain(iter::once(s.len()));
568 let shrunk = format!(
569 "{before}...{after}",
570 before = &s[..positions().nth(before).unwrap_or(s.len())],
571 after = &s[positions().rev().nth(after).unwrap_or(0)..],
574 let path = tcx.output_filenames(()).temp_path_ext("long-type.txt", None);
575 let written_to_path = std::fs::write(&path, s).ok().map(|_| path);
577 (shrunk, written_to_path)
583 fn check_recursion_limit<'tcx>(
585 instance: Instance<'tcx>,
587 recursion_depths: &mut DefIdMap<usize>,
588 recursion_limit: Limit,
589 ) -> (DefId, usize) {
590 let def_id = instance.def_id();
591 let recursion_depth = recursion_depths.get(&def_id).cloned().unwrap_or(0);
592 debug!(" => recursion depth={}", recursion_depth);
594 let adjusted_recursion_depth = if Some(def_id) == tcx.lang_items().drop_in_place_fn() {
595 // HACK: drop_in_place creates tight monomorphization loops. Give
602 // Code that needs to instantiate the same function recursively
603 // more than the recursion limit is assumed to be causing an
604 // infinite expansion.
605 if !recursion_limit.value_within_limit(adjusted_recursion_depth) {
606 let def_span = tcx.def_span(def_id);
607 let def_path_str = tcx.def_path_str(def_id);
608 let (shrunk, written_to_path) = shrunk_instance_name(tcx, &instance, 32, 32);
609 let mut path = PathBuf::new();
610 let was_written = if written_to_path.is_some() {
611 path = written_to_path.unwrap();
616 tcx.sess.emit_fatal(RecursionLimit {
626 recursion_depths.insert(def_id, recursion_depth + 1);
628 (def_id, recursion_depth)
631 fn check_type_length_limit<'tcx>(tcx: TyCtxt<'tcx>, instance: Instance<'tcx>) {
632 let type_length = instance
635 .flat_map(|arg| arg.walk())
636 .filter(|arg| match arg.unpack() {
637 GenericArgKind::Type(_) | GenericArgKind::Const(_) => true,
638 GenericArgKind::Lifetime(_) => false,
641 debug!(" => type length={}", type_length);
643 // Rust code can easily create exponentially-long types using only a
644 // polynomial recursion depth. Even with the default recursion
645 // depth, you can easily get cases that take >2^60 steps to run,
646 // which means that rustc basically hangs.
648 // Bail out in these cases to avoid that bad user experience.
649 if !tcx.type_length_limit().value_within_limit(type_length) {
650 let (shrunk, written_to_path) = shrunk_instance_name(tcx, &instance, 32, 32);
651 let span = tcx.def_span(instance.def_id());
652 let mut path = PathBuf::new();
653 let was_written = if written_to_path.is_some() {
654 path = written_to_path.unwrap();
659 tcx.sess.emit_fatal(TypeLengthLimit { span, shrunk, was_written, path, type_length });
663 struct MirNeighborCollector<'a, 'tcx> {
665 body: &'a mir::Body<'tcx>,
666 output: &'a mut MonoItems<'tcx>,
667 instance: Instance<'tcx>,
670 impl<'a, 'tcx> MirNeighborCollector<'a, 'tcx> {
671 pub fn monomorphize<T>(&self, value: T) -> T
673 T: TypeFoldable<'tcx>,
675 debug!("monomorphize: self.instance={:?}", self.instance);
676 self.instance.subst_mir_and_normalize_erasing_regions(
678 ty::ParamEnv::reveal_all(),
684 impl<'a, 'tcx> MirVisitor<'tcx> for MirNeighborCollector<'a, 'tcx> {
685 fn visit_rvalue(&mut self, rvalue: &mir::Rvalue<'tcx>, location: Location) {
686 debug!("visiting rvalue {:?}", *rvalue);
688 let span = self.body.source_info(location).span;
691 // When doing an cast from a regular pointer to a fat pointer, we
692 // have to instantiate all methods of the trait being cast to, so we
693 // can build the appropriate vtable.
695 mir::CastKind::Pointer(PointerCast::Unsize),
699 let target_ty = self.monomorphize(target_ty);
700 let source_ty = operand.ty(self.body, self.tcx);
701 let source_ty = self.monomorphize(source_ty);
702 let (source_ty, target_ty) =
703 find_vtable_types_for_unsizing(self.tcx, source_ty, target_ty);
704 // This could also be a different Unsize instruction, like
705 // from a fixed sized array to a slice. But we are only
706 // interested in things that produce a vtable.
707 if target_ty.is_trait() && !source_ty.is_trait() {
708 create_mono_items_for_vtable_methods(
718 mir::CastKind::Pointer(PointerCast::ReifyFnPointer),
722 let fn_ty = operand.ty(self.body, self.tcx);
723 let fn_ty = self.monomorphize(fn_ty);
724 visit_fn_use(self.tcx, fn_ty, false, span, &mut self.output);
727 mir::CastKind::Pointer(PointerCast::ClosureFnPointer(_)),
731 let source_ty = operand.ty(self.body, self.tcx);
732 let source_ty = self.monomorphize(source_ty);
733 match *source_ty.kind() {
734 ty::Closure(def_id, substs) => {
735 let instance = Instance::resolve_closure(
739 ty::ClosureKind::FnOnce,
741 .expect("failed to normalize and resolve closure during codegen");
742 if should_codegen_locally(self.tcx, &instance) {
743 self.output.push(create_fn_mono_item(self.tcx, instance, span));
749 mir::Rvalue::ThreadLocalRef(def_id) => {
750 assert!(self.tcx.is_thread_local_static(def_id));
751 let instance = Instance::mono(self.tcx, def_id);
752 if should_codegen_locally(self.tcx, &instance) {
753 trace!("collecting thread-local static {:?}", def_id);
754 self.output.push(respan(span, MonoItem::Static(def_id)));
757 _ => { /* not interesting */ }
760 self.super_rvalue(rvalue, location);
763 /// This does not walk the constant, as it has been handled entirely here and trying
764 /// to walk it would attempt to evaluate the `ty::Const` inside, which doesn't necessarily
765 /// work, as some constants cannot be represented in the type system.
766 #[instrument(skip(self), level = "debug")]
767 fn visit_constant(&mut self, constant: &mir::Constant<'tcx>, location: Location) {
768 let literal = self.monomorphize(constant.literal);
769 let val = match literal {
770 mir::ConstantKind::Val(val, _) => val,
771 mir::ConstantKind::Ty(ct) => match ct.kind() {
772 ty::ConstKind::Value(val) => self.tcx.valtree_to_const_val((ct.ty(), val)),
773 ty::ConstKind::Unevaluated(ct) => {
775 let param_env = ty::ParamEnv::reveal_all();
776 match self.tcx.const_eval_resolve(param_env, ct, None) {
777 // The `monomorphize` call should have evaluated that constant already.
779 Err(ErrorHandled::Reported(_) | ErrorHandled::Linted) => return,
780 Err(ErrorHandled::TooGeneric) => span_bug!(
781 self.body.source_info(location).span,
782 "collection encountered polymorphic constant: {:?}",
790 collect_const_value(self.tcx, val, self.output);
791 self.visit_ty(literal.ty(), TyContext::Location(location));
794 #[instrument(skip(self), level = "debug")]
795 fn visit_const(&mut self, constant: ty::Const<'tcx>, location: Location) {
796 debug!("visiting const {:?} @ {:?}", constant, location);
798 let substituted_constant = self.monomorphize(constant);
799 let param_env = ty::ParamEnv::reveal_all();
801 match substituted_constant.kind() {
802 ty::ConstKind::Value(val) => {
803 let const_val = self.tcx.valtree_to_const_val((constant.ty(), val));
804 collect_const_value(self.tcx, const_val, self.output)
806 ty::ConstKind::Unevaluated(unevaluated) => {
807 match self.tcx.const_eval_resolve(param_env, unevaluated, None) {
808 // The `monomorphize` call should have evaluated that constant already.
809 Ok(val) => span_bug!(
810 self.body.source_info(location).span,
811 "collection encountered the unevaluated constant {} which evaluated to {:?}",
812 substituted_constant,
815 Err(ErrorHandled::Reported(_) | ErrorHandled::Linted) => {}
816 Err(ErrorHandled::TooGeneric) => span_bug!(
817 self.body.source_info(location).span,
818 "collection encountered polymorphic constant: {}",
826 self.super_const(constant);
829 fn visit_terminator(&mut self, terminator: &mir::Terminator<'tcx>, location: Location) {
830 debug!("visiting terminator {:?} @ {:?}", terminator, location);
831 let source = self.body.source_info(location).span;
834 match terminator.kind {
835 mir::TerminatorKind::Call { ref func, .. } => {
836 let callee_ty = func.ty(self.body, tcx);
837 let callee_ty = self.monomorphize(callee_ty);
838 visit_fn_use(self.tcx, callee_ty, true, source, &mut self.output);
840 mir::TerminatorKind::Drop { ref place, .. }
841 | mir::TerminatorKind::DropAndReplace { ref place, .. } => {
842 let ty = place.ty(self.body, self.tcx).ty;
843 let ty = self.monomorphize(ty);
844 visit_drop_use(self.tcx, ty, true, source, self.output);
846 mir::TerminatorKind::InlineAsm { ref operands, .. } => {
849 mir::InlineAsmOperand::SymFn { ref value } => {
850 let fn_ty = self.monomorphize(value.literal.ty());
851 visit_fn_use(self.tcx, fn_ty, false, source, &mut self.output);
853 mir::InlineAsmOperand::SymStatic { def_id } => {
854 let instance = Instance::mono(self.tcx, def_id);
855 if should_codegen_locally(self.tcx, &instance) {
856 trace!("collecting asm sym static {:?}", def_id);
857 self.output.push(respan(source, MonoItem::Static(def_id)));
864 mir::TerminatorKind::Assert { ref msg, .. } => {
865 let lang_item = match msg {
866 mir::AssertKind::BoundsCheck { .. } => LangItem::PanicBoundsCheck,
867 _ => LangItem::Panic,
869 let instance = Instance::mono(tcx, tcx.require_lang_item(lang_item, Some(source)));
870 if should_codegen_locally(tcx, &instance) {
871 self.output.push(create_fn_mono_item(tcx, instance, source));
874 mir::TerminatorKind::Abort { .. } => {
875 let instance = Instance::mono(
877 tcx.require_lang_item(LangItem::PanicNoUnwind, Some(source)),
879 if should_codegen_locally(tcx, &instance) {
880 self.output.push(create_fn_mono_item(tcx, instance, source));
883 mir::TerminatorKind::Goto { .. }
884 | mir::TerminatorKind::SwitchInt { .. }
885 | mir::TerminatorKind::Resume
886 | mir::TerminatorKind::Return
887 | mir::TerminatorKind::Unreachable => {}
888 mir::TerminatorKind::GeneratorDrop
889 | mir::TerminatorKind::Yield { .. }
890 | mir::TerminatorKind::FalseEdge { .. }
891 | mir::TerminatorKind::FalseUnwind { .. } => bug!(),
894 self.super_terminator(terminator, location);
897 fn visit_operand(&mut self, operand: &mir::Operand<'tcx>, location: Location) {
898 self.super_operand(operand, location);
899 let limit = self.tcx.move_size_limit().0;
903 let limit = Size::from_bytes(limit);
904 let ty = operand.ty(self.body, self.tcx);
905 let ty = self.monomorphize(ty);
906 let layout = self.tcx.layout_of(ty::ParamEnv::reveal_all().and(ty));
907 if let Ok(layout) = layout {
908 if layout.size > limit {
910 let source_info = self.body.source_info(location);
911 debug!(?source_info);
912 let lint_root = source_info.scope.lint_root(&self.body.source_scopes);
914 let Some(lint_root) = lint_root else {
915 // This happens when the issue is in a function from a foreign crate that
916 // we monomorphized in the current crate. We can't get a `HirId` for things
918 // FIXME: Find out where to report the lint on. Maybe simply crate-level lint root
919 // but correct span? This would make the lint at least accept crate-level lint attributes.
922 self.tcx.emit_spanned_lint(
926 LargeAssignmentsLint {
927 span: source_info.span,
928 size: layout.size.bytes(),
929 limit: limit.bytes(),
939 _context: mir::visit::PlaceContext,
945 fn visit_drop_use<'tcx>(
948 is_direct_call: bool,
950 output: &mut MonoItems<'tcx>,
952 let instance = Instance::resolve_drop_in_place(tcx, ty);
953 visit_instance_use(tcx, instance, is_direct_call, source, output);
956 fn visit_fn_use<'tcx>(
959 is_direct_call: bool,
961 output: &mut MonoItems<'tcx>,
963 if let ty::FnDef(def_id, substs) = *ty.kind() {
964 let instance = if is_direct_call {
965 ty::Instance::resolve(tcx, ty::ParamEnv::reveal_all(), def_id, substs).unwrap().unwrap()
967 ty::Instance::resolve_for_fn_ptr(tcx, ty::ParamEnv::reveal_all(), def_id, substs)
970 visit_instance_use(tcx, instance, is_direct_call, source, output);
974 fn visit_instance_use<'tcx>(
976 instance: ty::Instance<'tcx>,
977 is_direct_call: bool,
979 output: &mut MonoItems<'tcx>,
981 debug!("visit_item_use({:?}, is_direct_call={:?})", instance, is_direct_call);
982 if !should_codegen_locally(tcx, &instance) {
987 ty::InstanceDef::Virtual(..) | ty::InstanceDef::Intrinsic(_) => {
989 bug!("{:?} being reified", instance);
992 ty::InstanceDef::DropGlue(_, None) => {
993 // Don't need to emit noop drop glue if we are calling directly.
995 output.push(create_fn_mono_item(tcx, instance, source));
998 ty::InstanceDef::DropGlue(_, Some(_))
999 | ty::InstanceDef::VTableShim(..)
1000 | ty::InstanceDef::ReifyShim(..)
1001 | ty::InstanceDef::ClosureOnceShim { .. }
1002 | ty::InstanceDef::Item(..)
1003 | ty::InstanceDef::FnPtrShim(..)
1004 | ty::InstanceDef::CloneShim(..) => {
1005 output.push(create_fn_mono_item(tcx, instance, source));
1010 /// Returns `true` if we should codegen an instance in the local crate, or returns `false` if we
1011 /// can just link to the upstream crate and therefore don't need a mono item.
1012 fn should_codegen_locally<'tcx>(tcx: TyCtxt<'tcx>, instance: &Instance<'tcx>) -> bool {
1013 let Some(def_id) = instance.def.def_id_if_not_guaranteed_local_codegen() else {
1017 if tcx.is_foreign_item(def_id) {
1018 // Foreign items are always linked against, there's no way of instantiating them.
1022 if def_id.is_local() {
1023 // Local items cannot be referred to locally without monomorphizing them locally.
1027 if tcx.is_reachable_non_generic(def_id)
1028 || instance.polymorphize(tcx).upstream_monomorphization(tcx).is_some()
1030 // We can link to the item in question, no instance needed in this crate.
1034 if let DefKind::Static(_) = tcx.def_kind(def_id) {
1035 // We cannot monomorphize statics from upstream crates.
1039 if !tcx.is_mir_available(def_id) {
1040 bug!("no MIR available for {:?}", def_id);
1046 /// For a given pair of source and target type that occur in an unsizing coercion,
1047 /// this function finds the pair of types that determines the vtable linking
1050 /// For example, the source type might be `&SomeStruct` and the target type
1051 /// might be `&dyn SomeTrait` in a cast like:
1053 /// ```rust,ignore (not real code)
1054 /// let src: &SomeStruct = ...;
1055 /// let target = src as &dyn SomeTrait;
1058 /// Then the output of this function would be (SomeStruct, SomeTrait) since for
1059 /// constructing the `target` fat-pointer we need the vtable for that pair.
1061 /// Things can get more complicated though because there's also the case where
1062 /// the unsized type occurs as a field:
1065 /// struct ComplexStruct<T: ?Sized> {
1072 /// In this case, if `T` is sized, `&ComplexStruct<T>` is a thin pointer. If `T`
1073 /// is unsized, `&SomeStruct` is a fat pointer, and the vtable it points to is
1074 /// for the pair of `T` (which is a trait) and the concrete type that `T` was
1075 /// originally coerced from:
1077 /// ```rust,ignore (not real code)
1078 /// let src: &ComplexStruct<SomeStruct> = ...;
1079 /// let target = src as &ComplexStruct<dyn SomeTrait>;
1082 /// Again, we want this `find_vtable_types_for_unsizing()` to provide the pair
1083 /// `(SomeStruct, SomeTrait)`.
1085 /// Finally, there is also the case of custom unsizing coercions, e.g., for
1086 /// smart pointers such as `Rc` and `Arc`.
1087 fn find_vtable_types_for_unsizing<'tcx>(
1089 source_ty: Ty<'tcx>,
1090 target_ty: Ty<'tcx>,
1091 ) -> (Ty<'tcx>, Ty<'tcx>) {
1092 let ptr_vtable = |inner_source: Ty<'tcx>, inner_target: Ty<'tcx>| {
1093 let param_env = ty::ParamEnv::reveal_all();
1094 let type_has_metadata = |ty: Ty<'tcx>| -> bool {
1095 if ty.is_sized(tcx.at(DUMMY_SP), param_env) {
1098 let tail = tcx.struct_tail_erasing_lifetimes(ty, param_env);
1100 ty::Foreign(..) => false,
1101 ty::Str | ty::Slice(..) | ty::Dynamic(..) => true,
1102 _ => bug!("unexpected unsized tail: {:?}", tail),
1105 if type_has_metadata(inner_source) {
1106 (inner_source, inner_target)
1108 tcx.struct_lockstep_tails_erasing_lifetimes(inner_source, inner_target, param_env)
1112 match (&source_ty.kind(), &target_ty.kind()) {
1113 (&ty::Ref(_, a, _), &ty::Ref(_, b, _) | &ty::RawPtr(ty::TypeAndMut { ty: b, .. }))
1114 | (&ty::RawPtr(ty::TypeAndMut { ty: a, .. }), &ty::RawPtr(ty::TypeAndMut { ty: b, .. })) => {
1117 (&ty::Adt(def_a, _), &ty::Adt(def_b, _)) if def_a.is_box() && def_b.is_box() => {
1118 ptr_vtable(source_ty.boxed_ty(), target_ty.boxed_ty())
1121 (&ty::Adt(source_adt_def, source_substs), &ty::Adt(target_adt_def, target_substs)) => {
1122 assert_eq!(source_adt_def, target_adt_def);
1124 let CustomCoerceUnsized::Struct(coerce_index) =
1125 crate::custom_coerce_unsize_info(tcx, source_ty, target_ty);
1127 let source_fields = &source_adt_def.non_enum_variant().fields;
1128 let target_fields = &target_adt_def.non_enum_variant().fields;
1131 coerce_index < source_fields.len() && source_fields.len() == target_fields.len()
1134 find_vtable_types_for_unsizing(
1136 source_fields[coerce_index].ty(tcx, source_substs),
1137 target_fields[coerce_index].ty(tcx, target_substs),
1141 "find_vtable_types_for_unsizing: invalid coercion {:?} -> {:?}",
1148 #[instrument(skip(tcx), level = "debug", ret)]
1149 fn create_fn_mono_item<'tcx>(
1151 instance: Instance<'tcx>,
1153 ) -> Spanned<MonoItem<'tcx>> {
1154 let def_id = instance.def_id();
1155 if tcx.sess.opts.unstable_opts.profile_closures && def_id.is_local() && tcx.is_closure(def_id) {
1156 crate::util::dump_closure_profile(tcx, instance);
1159 respan(source, MonoItem::Fn(instance.polymorphize(tcx)))
1162 /// Creates a `MonoItem` for each method that is referenced by the vtable for
1163 /// the given trait/impl pair.
1164 fn create_mono_items_for_vtable_methods<'tcx>(
1169 output: &mut MonoItems<'tcx>,
1171 assert!(!trait_ty.has_escaping_bound_vars() && !impl_ty.has_escaping_bound_vars());
1173 if let ty::Dynamic(ref trait_ty, ..) = trait_ty.kind() {
1174 if let Some(principal) = trait_ty.principal() {
1175 let poly_trait_ref = principal.with_self_ty(tcx, impl_ty);
1176 assert!(!poly_trait_ref.has_escaping_bound_vars());
1178 // Walk all methods of the trait, including those of its supertraits
1179 let entries = tcx.vtable_entries(poly_trait_ref);
1180 let methods = entries
1182 .filter_map(|entry| match entry {
1183 VtblEntry::MetadataDropInPlace
1184 | VtblEntry::MetadataSize
1185 | VtblEntry::MetadataAlign
1186 | VtblEntry::Vacant => None,
1187 VtblEntry::TraitVPtr(_) => {
1188 // all super trait items already covered, so skip them.
1191 VtblEntry::Method(instance) => {
1192 Some(*instance).filter(|instance| should_codegen_locally(tcx, instance))
1195 .map(|item| create_fn_mono_item(tcx, item, source));
1196 output.extend(methods);
1199 // Also add the destructor.
1200 visit_drop_use(tcx, impl_ty, false, source, output);
1204 //=-----------------------------------------------------------------------------
1206 //=-----------------------------------------------------------------------------
1208 struct RootCollector<'a, 'tcx> {
1210 mode: MonoItemCollectionMode,
1211 output: &'a mut MonoItems<'tcx>,
1212 entry_fn: Option<(DefId, EntryFnType)>,
1215 impl<'v> RootCollector<'_, 'v> {
1216 fn process_item(&mut self, id: hir::ItemId) {
1217 match self.tcx.def_kind(id.def_id) {
1218 DefKind::Enum | DefKind::Struct | DefKind::Union => {
1219 let item = self.tcx.hir().item(id);
1221 hir::ItemKind::Enum(_, ref generics)
1222 | hir::ItemKind::Struct(_, ref generics)
1223 | hir::ItemKind::Union(_, ref generics) => {
1224 if generics.params.is_empty() {
1225 if self.mode == MonoItemCollectionMode::Eager {
1227 "RootCollector: ADT drop-glue for {}",
1228 self.tcx.def_path_str(item.def_id.to_def_id())
1232 Instance::new(item.def_id.to_def_id(), InternalSubsts::empty())
1233 .ty(self.tcx, ty::ParamEnv::reveal_all());
1234 visit_drop_use(self.tcx, ty, true, DUMMY_SP, self.output);
1241 DefKind::GlobalAsm => {
1243 "RootCollector: ItemKind::GlobalAsm({})",
1244 self.tcx.def_path_str(id.def_id.to_def_id())
1246 self.output.push(dummy_spanned(MonoItem::GlobalAsm(id)));
1248 DefKind::Static(..) => {
1250 "RootCollector: ItemKind::Static({})",
1251 self.tcx.def_path_str(id.def_id.to_def_id())
1253 self.output.push(dummy_spanned(MonoItem::Static(id.def_id.to_def_id())));
1256 // const items only generate mono items if they are
1257 // actually used somewhere. Just declaring them is insufficient.
1259 // but even just declaring them must collect the items they refer to
1260 if let Ok(val) = self.tcx.const_eval_poly(id.def_id.to_def_id()) {
1261 collect_const_value(self.tcx, val, &mut self.output);
1265 if self.mode == MonoItemCollectionMode::Eager {
1266 let item = self.tcx.hir().item(id);
1267 create_mono_items_for_default_impls(self.tcx, item, self.output);
1271 self.push_if_root(id.def_id);
1277 fn process_impl_item(&mut self, id: hir::ImplItemId) {
1278 if matches!(self.tcx.def_kind(id.def_id), DefKind::AssocFn) {
1279 self.push_if_root(id.def_id);
1283 fn is_root(&self, def_id: LocalDefId) -> bool {
1284 !item_requires_monomorphization(self.tcx, def_id)
1285 && match self.mode {
1286 MonoItemCollectionMode::Eager => true,
1287 MonoItemCollectionMode::Lazy => {
1288 self.entry_fn.and_then(|(id, _)| id.as_local()) == Some(def_id)
1289 || self.tcx.is_reachable_non_generic(def_id)
1292 .codegen_fn_attrs(def_id)
1294 .contains(CodegenFnAttrFlags::RUSTC_STD_INTERNAL_SYMBOL)
1299 /// If `def_id` represents a root, pushes it onto the list of
1300 /// outputs. (Note that all roots must be monomorphic.)
1301 #[instrument(skip(self), level = "debug")]
1302 fn push_if_root(&mut self, def_id: LocalDefId) {
1303 if self.is_root(def_id) {
1304 debug!("found root");
1306 let instance = Instance::mono(self.tcx, def_id.to_def_id());
1307 self.output.push(create_fn_mono_item(self.tcx, instance, DUMMY_SP));
1311 /// As a special case, when/if we encounter the
1312 /// `main()` function, we also have to generate a
1313 /// monomorphized copy of the start lang item based on
1314 /// the return type of `main`. This is not needed when
1315 /// the user writes their own `start` manually.
1316 fn push_extra_entry_roots(&mut self) {
1317 let Some((main_def_id, EntryFnType::Main)) = self.entry_fn else {
1321 let start_def_id = match self.tcx.lang_items().require(LangItem::Start) {
1323 Err(lang_item_err) => {
1326 .emit_fatal(RequiresLangItem { lang_item: lang_item_err.0.name().to_string() });
1329 let main_ret_ty = self.tcx.fn_sig(main_def_id).output();
1331 // Given that `main()` has no arguments,
1332 // then its return type cannot have
1333 // late-bound regions, since late-bound
1334 // regions must appear in the argument
1336 let main_ret_ty = self.tcx.normalize_erasing_regions(
1337 ty::ParamEnv::reveal_all(),
1338 main_ret_ty.no_bound_vars().unwrap(),
1341 let start_instance = Instance::resolve(
1343 ty::ParamEnv::reveal_all(),
1345 self.tcx.intern_substs(&[main_ret_ty.into()]),
1350 self.output.push(create_fn_mono_item(self.tcx, start_instance, DUMMY_SP));
1354 fn item_requires_monomorphization(tcx: TyCtxt<'_>, def_id: LocalDefId) -> bool {
1355 let generics = tcx.generics_of(def_id);
1356 generics.requires_monomorphization(tcx)
1359 fn create_mono_items_for_default_impls<'tcx>(
1361 item: &'tcx hir::Item<'tcx>,
1362 output: &mut MonoItems<'tcx>,
1365 hir::ItemKind::Impl(ref impl_) => {
1366 for param in impl_.generics.params {
1368 hir::GenericParamKind::Lifetime { .. } => {}
1369 hir::GenericParamKind::Type { .. } | hir::GenericParamKind::Const { .. } => {
1376 "create_mono_items_for_default_impls(item={})",
1377 tcx.def_path_str(item.def_id.to_def_id())
1380 if let Some(trait_ref) = tcx.impl_trait_ref(item.def_id) {
1381 let param_env = ty::ParamEnv::reveal_all();
1382 let trait_ref = tcx.normalize_erasing_regions(param_env, trait_ref);
1383 let overridden_methods = tcx.impl_item_implementor_ids(item.def_id);
1384 for method in tcx.provided_trait_methods(trait_ref.def_id) {
1385 if overridden_methods.contains_key(&method.def_id) {
1389 if tcx.generics_of(method.def_id).own_requires_monomorphization() {
1394 InternalSubsts::for_item(tcx, method.def_id, |param, _| match param.kind {
1395 GenericParamDefKind::Lifetime => tcx.lifetimes.re_erased.into(),
1396 GenericParamDefKind::Type { .. }
1397 | GenericParamDefKind::Const { .. } => {
1398 trait_ref.substs[param.index as usize]
1401 let instance = ty::Instance::resolve(tcx, param_env, method.def_id, substs)
1405 let mono_item = create_fn_mono_item(tcx, instance, DUMMY_SP);
1406 if mono_item.node.is_instantiable(tcx) && should_codegen_locally(tcx, &instance)
1408 output.push(mono_item);
1417 /// Scans the miri alloc in order to find function calls, closures, and drop-glue.
1418 fn collect_miri<'tcx>(tcx: TyCtxt<'tcx>, alloc_id: AllocId, output: &mut MonoItems<'tcx>) {
1419 match tcx.global_alloc(alloc_id) {
1420 GlobalAlloc::Static(def_id) => {
1421 assert!(!tcx.is_thread_local_static(def_id));
1422 let instance = Instance::mono(tcx, def_id);
1423 if should_codegen_locally(tcx, &instance) {
1424 trace!("collecting static {:?}", def_id);
1425 output.push(dummy_spanned(MonoItem::Static(def_id)));
1428 GlobalAlloc::Memory(alloc) => {
1429 trace!("collecting {:?} with {:#?}", alloc_id, alloc);
1430 for &inner in alloc.inner().provenance().values() {
1431 rustc_data_structures::stack::ensure_sufficient_stack(|| {
1432 collect_miri(tcx, inner, output);
1436 GlobalAlloc::Function(fn_instance) => {
1437 if should_codegen_locally(tcx, &fn_instance) {
1438 trace!("collecting {:?} with {:#?}", alloc_id, fn_instance);
1439 output.push(create_fn_mono_item(tcx, fn_instance, DUMMY_SP));
1442 GlobalAlloc::VTable(ty, trait_ref) => {
1443 let alloc_id = tcx.vtable_allocation((ty, trait_ref));
1444 collect_miri(tcx, alloc_id, output)
1449 /// Scans the MIR in order to find function calls, closures, and drop-glue.
1450 #[instrument(skip(tcx, output), level = "debug")]
1451 fn collect_neighbours<'tcx>(
1453 instance: Instance<'tcx>,
1454 output: &mut MonoItems<'tcx>,
1456 let body = tcx.instance_mir(instance.def);
1457 MirNeighborCollector { tcx, body: &body, output, instance }.visit_body(&body);
1460 #[instrument(skip(tcx, output), level = "debug")]
1461 fn collect_const_value<'tcx>(
1463 value: ConstValue<'tcx>,
1464 output: &mut MonoItems<'tcx>,
1467 ConstValue::Scalar(Scalar::Ptr(ptr, _size)) => collect_miri(tcx, ptr.provenance, output),
1468 ConstValue::Slice { data: alloc, start: _, end: _ } | ConstValue::ByRef { alloc, .. } => {
1469 for &id in alloc.inner().provenance().values() {
1470 collect_miri(tcx, id, output);