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-save 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_iter, MTLock, MTRef, ParallelIterator}
;
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
::{self, GenericParamDefKind, Instance, Ty, TyCtxt, TypeFoldable, VtblEntry}
;
198 use rustc_middle
::{middle::codegen_fn_attrs::CodegenFnAttrFlags, mir::visit::TyContext}
;
199 use rustc_session
::config
::EntryFnType
;
200 use rustc_session
::lint
::builtin
::LARGE_ASSIGNMENTS
;
201 use rustc_session
::Limit
;
202 use rustc_span
::source_map
::{dummy_spanned, respan, Span, Spanned, DUMMY_SP}
;
203 use rustc_target
::abi
::Size
;
206 use std
::path
::PathBuf
;
209 pub enum MonoItemCollectionMode
{
214 /// Maps every mono item to all mono items it references in its
216 pub struct InliningMap
<'tcx
> {
217 // Maps a source mono item to the range of mono items
219 // The range selects elements within the `targets` vecs.
220 index
: FxHashMap
<MonoItem
<'tcx
>, Range
<usize>>,
221 targets
: Vec
<MonoItem
<'tcx
>>,
223 // Contains one bit per mono item in the `targets` field. That bit
224 // is true if that mono item needs to be inlined into every CGU.
225 inlines
: GrowableBitSet
<usize>,
228 /// Struct to store mono items in each collecting and if they should
229 /// be inlined. We call `instantiation_mode` to get their inlining
230 /// status when inserting new elements, which avoids calling it in
231 /// `inlining_map.lock_mut()`. See the `collect_items_rec` implementation
233 struct MonoItems
<'tcx
> {
234 // If this is false, we do not need to compute whether items
235 // will need to be inlined.
236 compute_inlining
: bool
,
238 // The TyCtxt used to determine whether the a item should
242 // The collected mono items. The bool field in each element
243 // indicates whether this element should be inlined.
244 items
: Vec
<(Spanned
<MonoItem
<'tcx
>>, bool
/*inlined*/)>,
247 impl<'tcx
> MonoItems
<'tcx
> {
249 fn push(&mut self, item
: Spanned
<MonoItem
<'tcx
>>) {
254 fn extend
<T
: IntoIterator
<Item
= Spanned
<MonoItem
<'tcx
>>>>(&mut self, iter
: T
) {
255 self.items
.extend(iter
.into_iter().map(|mono_item
| {
256 let inlined
= if !self.compute_inlining
{
259 mono_item
.node
.instantiation_mode(self.tcx
) == InstantiationMode
::LocalCopy
266 impl<'tcx
> InliningMap
<'tcx
> {
267 fn new() -> InliningMap
<'tcx
> {
269 index
: FxHashMap
::default(),
271 inlines
: GrowableBitSet
::with_capacity(1024),
275 fn record_accesses
<'a
>(
277 source
: MonoItem
<'tcx
>,
278 new_targets
: &'a
[(Spanned
<MonoItem
<'tcx
>>, bool
)],
282 let start_index
= self.targets
.len();
283 let new_items_count
= new_targets
.len();
284 let new_items_count_total
= new_items_count
+ self.targets
.len();
286 self.targets
.reserve(new_items_count
);
287 self.inlines
.ensure(new_items_count_total
);
289 for (i
, (Spanned { node: mono_item, .. }
, inlined
)) in new_targets
.into_iter().enumerate() {
290 self.targets
.push(*mono_item
);
292 self.inlines
.insert(i
+ start_index
);
296 let end_index
= self.targets
.len();
297 assert
!(self.index
.insert(source
, start_index
..end_index
).is_none());
300 // Internally iterate over all items referenced by `source` which will be
301 // made available for inlining.
302 pub fn with_inlining_candidates
<F
>(&self, source
: MonoItem
<'tcx
>, mut f
: F
)
304 F
: FnMut(MonoItem
<'tcx
>),
306 if let Some(range
) = self.index
.get(&source
) {
307 for (i
, candidate
) in self.targets
[range
.clone()].iter().enumerate() {
308 if self.inlines
.contains(range
.start
+ i
) {
315 // Internally iterate over all items and the things each accesses.
316 pub fn iter_accesses
<F
>(&self, mut f
: F
)
318 F
: FnMut(MonoItem
<'tcx
>, &[MonoItem
<'tcx
>]),
320 for (&accessor
, range
) in &self.index
{
321 f(accessor
, &self.targets
[range
.clone()])
326 #[instrument(skip(tcx, mode), level = "debug")]
327 pub fn collect_crate_mono_items(
329 mode
: MonoItemCollectionMode
,
330 ) -> (FxHashSet
<MonoItem
<'_
>>, InliningMap
<'_
>) {
331 let _prof_timer
= tcx
.prof
.generic_activity("monomorphization_collector");
334 tcx
.sess
.time("monomorphization_collector_root_collections", || collect_roots(tcx
, mode
));
336 debug
!("building mono item graph, beginning at roots");
338 let mut visited
= MTLock
::new(FxHashSet
::default());
339 let mut inlining_map
= MTLock
::new(InliningMap
::new());
340 let recursion_limit
= tcx
.recursion_limit();
343 let visited
: MTRef
<'_
, _
> = &mut visited
;
344 let inlining_map
: MTRef
<'_
, _
> = &mut inlining_map
;
346 tcx
.sess
.time("monomorphization_collector_graph_walk", || {
347 par_iter(roots
).for_each(|root
| {
348 let mut recursion_depths
= DefIdMap
::default();
353 &mut recursion_depths
,
361 (visited
.into_inner(), inlining_map
.into_inner())
364 // Find all non-generic items by walking the HIR. These items serve as roots to
365 // start monomorphizing from.
366 #[instrument(skip(tcx, mode), level = "debug")]
367 fn collect_roots(tcx
: TyCtxt
<'_
>, mode
: MonoItemCollectionMode
) -> Vec
<MonoItem
<'_
>> {
368 debug
!("collecting roots");
369 let mut roots
= MonoItems { compute_inlining: false, tcx, items: Vec::new() }
;
372 let entry_fn
= tcx
.entry_fn(());
374 debug
!("collect_roots: entry_fn = {:?}", entry_fn
);
376 let mut collector
= RootCollector { tcx, mode, entry_fn, output: &mut roots }
;
378 let crate_items
= tcx
.hir_crate_items(());
380 for id
in crate_items
.items() {
381 collector
.process_item(id
);
384 for id
in crate_items
.impl_items() {
385 collector
.process_impl_item(id
);
388 collector
.push_extra_entry_roots();
391 // We can only codegen items that are instantiable - items all of
392 // whose predicates hold. Luckily, items that aren't instantiable
393 // can't actually be used, so we can just skip codegenning them.
397 .filter_map(|(Spanned { node: mono_item, .. }
, _
)| {
398 mono_item
.is_instantiable(tcx
).then_some(mono_item
)
403 /// Collect all monomorphized items reachable from `starting_point`, and emit a note diagnostic if a
404 /// post-monorphization error is encountered during a collection step.
405 #[instrument(skip(tcx, visited, recursion_depths, recursion_limit, inlining_map), level = "debug")]
406 fn collect_items_rec
<'tcx
>(
408 starting_point
: Spanned
<MonoItem
<'tcx
>>,
409 visited
: MTRef
<'_
, MTLock
<FxHashSet
<MonoItem
<'tcx
>>>>,
410 recursion_depths
: &mut DefIdMap
<usize>,
411 recursion_limit
: Limit
,
412 inlining_map
: MTRef
<'_
, MTLock
<InliningMap
<'tcx
>>>,
414 if !visited
.lock_mut().insert(starting_point
.node
) {
415 // We've been here already, no need to search again.
418 debug
!("BEGIN collect_items_rec({})", starting_point
.node
);
420 let mut neighbors
= MonoItems { compute_inlining: true, tcx, items: Vec::new() }
;
421 let recursion_depth_reset
;
424 // Post-monomorphization errors MVP
426 // We can encounter errors while monomorphizing an item, but we don't have a good way of
427 // showing a complete stack of spans ultimately leading to collecting the erroneous one yet.
428 // (It's also currently unclear exactly which diagnostics and information would be interesting
429 // to report in such cases)
431 // This leads to suboptimal error reporting: a post-monomorphization error (PME) will be
432 // shown with just a spanned piece of code causing the error, without information on where
433 // it was called from. This is especially obscure if the erroneous mono item is in a
434 // dependency. See for example issue #85155, where, before minimization, a PME happened two
435 // crates downstream from libcore's stdarch, without a way to know which dependency was the
438 // If such an error occurs in the current crate, its span will be enough to locate the
439 // source. If the cause is in another crate, the goal here is to quickly locate which mono
440 // item in the current crate is ultimately responsible for causing the error.
442 // To give at least _some_ context to the user: while collecting mono items, we check the
443 // error count. If it has changed, a PME occurred, and we trigger some diagnostics about the
444 // current step of mono items collection.
446 // FIXME: don't rely on global state, instead bubble up errors. Note: this is very hard to do.
447 let error_count
= tcx
.sess
.diagnostic().err_count();
449 match starting_point
.node
{
450 MonoItem
::Static(def_id
) => {
451 let instance
= Instance
::mono(tcx
, def_id
);
453 // Sanity check whether this ended up being collected accidentally
454 debug_assert
!(should_codegen_locally(tcx
, &instance
));
456 let ty
= instance
.ty(tcx
, ty
::ParamEnv
::reveal_all());
457 visit_drop_use(tcx
, ty
, true, starting_point
.span
, &mut neighbors
);
459 recursion_depth_reset
= None
;
461 if let Ok(alloc
) = tcx
.eval_static_initializer(def_id
) {
462 for &id
in alloc
.inner().relocations().values() {
463 collect_miri(tcx
, id
, &mut neighbors
);
467 MonoItem
::Fn(instance
) => {
468 // Sanity check whether this ended up being collected accidentally
469 debug_assert
!(should_codegen_locally(tcx
, &instance
));
471 // Keep track of the monomorphization recursion depth
472 recursion_depth_reset
= Some(check_recursion_limit(
479 check_type_length_limit(tcx
, instance
);
481 rustc_data_structures
::stack
::ensure_sufficient_stack(|| {
482 collect_neighbours(tcx
, instance
, &mut neighbors
);
485 MonoItem
::GlobalAsm(item_id
) => {
486 recursion_depth_reset
= None
;
488 let item
= tcx
.hir().item(item_id
);
489 if let hir
::ItemKind
::GlobalAsm(asm
) = item
.kind
{
490 for (op
, op_sp
) in asm
.operands
{
492 hir
::InlineAsmOperand
::Const { .. }
=> {
493 // Only constants which resolve to a plain integer
494 // are supported. Therefore the value should not
495 // depend on any other items.
497 hir
::InlineAsmOperand
::SymFn { anon_const }
=> {
499 tcx
.typeck_body(anon_const
.body
).node_type(anon_const
.hir_id
);
500 visit_fn_use(tcx
, fn_ty
, false, *op_sp
, &mut neighbors
);
502 hir
::InlineAsmOperand
::SymStatic { path: _, def_id }
=> {
503 let instance
= Instance
::mono(tcx
, *def_id
);
504 if should_codegen_locally(tcx
, &instance
) {
505 trace
!("collecting static {:?}", def_id
);
506 neighbors
.push(dummy_spanned(MonoItem
::Static(*def_id
)));
509 hir
::InlineAsmOperand
::In { .. }
510 | hir
::InlineAsmOperand
::Out { .. }
511 | hir
::InlineAsmOperand
::InOut { .. }
512 | hir
::InlineAsmOperand
::SplitInOut { .. }
=> {
513 span_bug
!(*op_sp
, "invalid operand type for global_asm!")
518 span_bug
!(item
.span
, "Mismatch between hir::Item type and MonoItem type")
523 // Check for PMEs and emit a diagnostic if one happened. To try to show relevant edges of the
525 if tcx
.sess
.diagnostic().err_count() > error_count
526 && starting_point
.node
.is_generic_fn()
527 && starting_point
.node
.is_user_defined()
529 let formatted_item
= with_no_trimmed_paths
!(starting_point
.node
.to_string());
530 tcx
.sess
.span_note_without_error(
532 &format
!("the above error was encountered while instantiating `{}`", formatted_item
),
535 inlining_map
.lock_mut().record_accesses(starting_point
.node
, &neighbors
.items
);
537 for (neighbour
, _
) in neighbors
.items
{
538 collect_items_rec(tcx
, neighbour
, visited
, recursion_depths
, recursion_limit
, inlining_map
);
541 if let Some((def_id
, depth
)) = recursion_depth_reset
{
542 recursion_depths
.insert(def_id
, depth
);
545 debug
!("END collect_items_rec({})", starting_point
.node
);
548 /// Format instance name that is already known to be too long for rustc.
549 /// Show only the first and last 32 characters to avoid blasting
550 /// the user's terminal with thousands of lines of type-name.
552 /// If the type name is longer than before+after, it will be written to a file.
553 fn shrunk_instance_name
<'tcx
>(
555 instance
: &Instance
<'tcx
>,
558 ) -> (String
, Option
<PathBuf
>) {
559 let s
= instance
.to_string();
561 // Only use the shrunk version if it's really shorter.
562 // This also avoids the case where before and after slices overlap.
563 if s
.chars().nth(before
+ after
+ 1).is_some() {
564 // An iterator of all byte positions including the end of the string.
565 let positions
= || s
.char_indices().map(|(i
, _
)| i
).chain(iter
::once(s
.len()));
567 let shrunk
= format
!(
568 "{before}...{after}",
569 before
= &s
[..positions().nth(before
).unwrap_or(s
.len())],
570 after
= &s
[positions().rev().nth(after
).unwrap_or(0)..],
573 let path
= tcx
.output_filenames(()).temp_path_ext("long-type.txt", None
);
574 let written_to_path
= std
::fs
::write(&path
, s
).ok().map(|_
| path
);
576 (shrunk
, written_to_path
)
582 fn check_recursion_limit
<'tcx
>(
584 instance
: Instance
<'tcx
>,
586 recursion_depths
: &mut DefIdMap
<usize>,
587 recursion_limit
: Limit
,
588 ) -> (DefId
, usize) {
589 let def_id
= instance
.def_id();
590 let recursion_depth
= recursion_depths
.get(&def_id
).cloned().unwrap_or(0);
591 debug
!(" => recursion depth={}", recursion_depth
);
593 let adjusted_recursion_depth
= if Some(def_id
) == tcx
.lang_items().drop_in_place_fn() {
594 // HACK: drop_in_place creates tight monomorphization loops. Give
601 // Code that needs to instantiate the same function recursively
602 // more than the recursion limit is assumed to be causing an
603 // infinite expansion.
604 if !recursion_limit
.value_within_limit(adjusted_recursion_depth
) {
605 let (shrunk
, written_to_path
) = shrunk_instance_name(tcx
, &instance
, 32, 32);
606 let error
= format
!("reached the recursion limit while instantiating `{}`", shrunk
);
607 let mut err
= tcx
.sess
.struct_span_fatal(span
, &error
);
609 tcx
.def_span(def_id
),
610 &format
!("`{}` defined here", tcx
.def_path_str(def_id
)),
612 if let Some(path
) = written_to_path
{
613 err
.note(&format
!("the full type name has been written to '{}'", path
.display()));
618 recursion_depths
.insert(def_id
, recursion_depth
+ 1);
620 (def_id
, recursion_depth
)
623 fn check_type_length_limit
<'tcx
>(tcx
: TyCtxt
<'tcx
>, instance
: Instance
<'tcx
>) {
624 let type_length
= instance
627 .flat_map(|arg
| arg
.walk())
628 .filter(|arg
| match arg
.unpack() {
629 GenericArgKind
::Type(_
) | GenericArgKind
::Const(_
) => true,
630 GenericArgKind
::Lifetime(_
) => false,
633 debug
!(" => type length={}", type_length
);
635 // Rust code can easily create exponentially-long types using only a
636 // polynomial recursion depth. Even with the default recursion
637 // depth, you can easily get cases that take >2^60 steps to run,
638 // which means that rustc basically hangs.
640 // Bail out in these cases to avoid that bad user experience.
641 if !tcx
.type_length_limit().value_within_limit(type_length
) {
642 let (shrunk
, written_to_path
) = shrunk_instance_name(tcx
, &instance
, 32, 32);
643 let msg
= format
!("reached the type-length limit while instantiating `{}`", shrunk
);
644 let mut diag
= tcx
.sess
.struct_span_fatal(tcx
.def_span(instance
.def_id()), &msg
);
645 if let Some(path
) = written_to_path
{
646 diag
.note(&format
!("the full type name has been written to '{}'", path
.display()));
649 "consider adding a `#![type_length_limit=\"{}\"]` attribute to your crate",
656 struct MirNeighborCollector
<'a
, 'tcx
> {
658 body
: &'a mir
::Body
<'tcx
>,
659 output
: &'a
mut MonoItems
<'tcx
>,
660 instance
: Instance
<'tcx
>,
663 impl<'a
, 'tcx
> MirNeighborCollector
<'a
, 'tcx
> {
664 pub fn monomorphize
<T
>(&self, value
: T
) -> T
666 T
: TypeFoldable
<'tcx
>,
668 debug
!("monomorphize: self.instance={:?}", self.instance
);
669 self.instance
.subst_mir_and_normalize_erasing_regions(
671 ty
::ParamEnv
::reveal_all(),
677 impl<'a
, 'tcx
> MirVisitor
<'tcx
> for MirNeighborCollector
<'a
, 'tcx
> {
678 fn visit_rvalue(&mut self, rvalue
: &mir
::Rvalue
<'tcx
>, location
: Location
) {
679 debug
!("visiting rvalue {:?}", *rvalue
);
681 let span
= self.body
.source_info(location
).span
;
684 // When doing an cast from a regular pointer to a fat pointer, we
685 // have to instantiate all methods of the trait being cast to, so we
686 // can build the appropriate vtable.
688 mir
::CastKind
::Pointer(PointerCast
::Unsize
),
692 let target_ty
= self.monomorphize(target_ty
);
693 let source_ty
= operand
.ty(self.body
, self.tcx
);
694 let source_ty
= self.monomorphize(source_ty
);
695 let (source_ty
, target_ty
) =
696 find_vtable_types_for_unsizing(self.tcx
, source_ty
, target_ty
);
697 // This could also be a different Unsize instruction, like
698 // from a fixed sized array to a slice. But we are only
699 // interested in things that produce a vtable.
700 if target_ty
.is_trait() && !source_ty
.is_trait() {
701 create_mono_items_for_vtable_methods(
711 mir
::CastKind
::Pointer(PointerCast
::ReifyFnPointer
),
715 let fn_ty
= operand
.ty(self.body
, self.tcx
);
716 let fn_ty
= self.monomorphize(fn_ty
);
717 visit_fn_use(self.tcx
, fn_ty
, false, span
, &mut self.output
);
720 mir
::CastKind
::Pointer(PointerCast
::ClosureFnPointer(_
)),
724 let source_ty
= operand
.ty(self.body
, self.tcx
);
725 let source_ty
= self.monomorphize(source_ty
);
726 match *source_ty
.kind() {
727 ty
::Closure(def_id
, substs
) => {
728 let instance
= Instance
::resolve_closure(
732 ty
::ClosureKind
::FnOnce
,
734 if should_codegen_locally(self.tcx
, &instance
) {
735 self.output
.push(create_fn_mono_item(self.tcx
, instance
, span
));
741 mir
::Rvalue
::ThreadLocalRef(def_id
) => {
742 assert
!(self.tcx
.is_thread_local_static(def_id
));
743 let instance
= Instance
::mono(self.tcx
, def_id
);
744 if should_codegen_locally(self.tcx
, &instance
) {
745 trace
!("collecting thread-local static {:?}", def_id
);
746 self.output
.push(respan(span
, MonoItem
::Static(def_id
)));
749 _
=> { /* not interesting */ }
752 self.super_rvalue(rvalue
, location
);
755 /// This does not walk the constant, as it has been handled entirely here and trying
756 /// to walk it would attempt to evaluate the `ty::Const` inside, which doesn't necessarily
757 /// work, as some constants cannot be represented in the type system.
758 #[instrument(skip(self), level = "debug")]
759 fn visit_constant(&mut self, constant
: &mir
::Constant
<'tcx
>, location
: Location
) {
760 let literal
= self.monomorphize(constant
.literal
);
761 let val
= match literal
{
762 mir
::ConstantKind
::Val(val
, _
) => val
,
763 mir
::ConstantKind
::Ty(ct
) => match ct
.kind() {
764 ty
::ConstKind
::Value(val
) => self.tcx
.valtree_to_const_val((ct
.ty(), val
)),
765 ty
::ConstKind
::Unevaluated(ct
) => {
767 let param_env
= ty
::ParamEnv
::reveal_all();
768 match self.tcx
.const_eval_resolve(param_env
, ct
, None
) {
769 // The `monomorphize` call should have evaluated that constant already.
771 Err(ErrorHandled
::Reported(_
) | ErrorHandled
::Linted
) => return,
772 Err(ErrorHandled
::TooGeneric
) => span_bug
!(
773 self.body
.source_info(location
).span
,
774 "collection encountered polymorphic constant: {:?}",
782 collect_const_value(self.tcx
, val
, self.output
);
783 self.visit_ty(literal
.ty(), TyContext
::Location(location
));
786 #[instrument(skip(self), level = "debug")]
787 fn visit_const(&mut self, constant
: ty
::Const
<'tcx
>, location
: Location
) {
788 debug
!("visiting const {:?} @ {:?}", constant
, location
);
790 let substituted_constant
= self.monomorphize(constant
);
791 let param_env
= ty
::ParamEnv
::reveal_all();
793 match substituted_constant
.kind() {
794 ty
::ConstKind
::Value(val
) => {
795 let const_val
= self.tcx
.valtree_to_const_val((constant
.ty(), val
));
796 collect_const_value(self.tcx
, const_val
, self.output
)
798 ty
::ConstKind
::Unevaluated(unevaluated
) => {
799 match self.tcx
.const_eval_resolve(param_env
, unevaluated
, None
) {
800 // The `monomorphize` call should have evaluated that constant already.
801 Ok(val
) => span_bug
!(
802 self.body
.source_info(location
).span
,
803 "collection encountered the unevaluated constant {} which evaluated to {:?}",
804 substituted_constant
,
807 Err(ErrorHandled
::Reported(_
) | ErrorHandled
::Linted
) => {}
808 Err(ErrorHandled
::TooGeneric
) => span_bug
!(
809 self.body
.source_info(location
).span
,
810 "collection encountered polymorphic constant: {}",
818 self.super_const(constant
);
821 fn visit_terminator(&mut self, terminator
: &mir
::Terminator
<'tcx
>, location
: Location
) {
822 debug
!("visiting terminator {:?} @ {:?}", terminator
, location
);
823 let source
= self.body
.source_info(location
).span
;
826 match terminator
.kind
{
827 mir
::TerminatorKind
::Call { ref func, .. }
=> {
828 let callee_ty
= func
.ty(self.body
, tcx
);
829 let callee_ty
= self.monomorphize(callee_ty
);
830 visit_fn_use(self.tcx
, callee_ty
, true, source
, &mut self.output
);
832 mir
::TerminatorKind
::Drop { ref place, .. }
833 | mir
::TerminatorKind
::DropAndReplace { ref place, .. }
=> {
834 let ty
= place
.ty(self.body
, self.tcx
).ty
;
835 let ty
= self.monomorphize(ty
);
836 visit_drop_use(self.tcx
, ty
, true, source
, self.output
);
838 mir
::TerminatorKind
::InlineAsm { ref operands, .. }
=> {
841 mir
::InlineAsmOperand
::SymFn { ref value }
=> {
842 let fn_ty
= self.monomorphize(value
.literal
.ty());
843 visit_fn_use(self.tcx
, fn_ty
, false, source
, &mut self.output
);
845 mir
::InlineAsmOperand
::SymStatic { def_id }
=> {
846 let instance
= Instance
::mono(self.tcx
, def_id
);
847 if should_codegen_locally(self.tcx
, &instance
) {
848 trace
!("collecting asm sym static {:?}", def_id
);
849 self.output
.push(respan(source
, MonoItem
::Static(def_id
)));
856 mir
::TerminatorKind
::Assert { ref msg, .. }
=> {
857 let lang_item
= match msg
{
858 mir
::AssertKind
::BoundsCheck { .. }
=> LangItem
::PanicBoundsCheck
,
859 _
=> LangItem
::Panic
,
861 let instance
= Instance
::mono(tcx
, tcx
.require_lang_item(lang_item
, Some(source
)));
862 if should_codegen_locally(tcx
, &instance
) {
863 self.output
.push(create_fn_mono_item(tcx
, instance
, source
));
866 mir
::TerminatorKind
::Abort { .. }
=> {
867 let instance
= Instance
::mono(
869 tcx
.require_lang_item(LangItem
::PanicNoUnwind
, Some(source
)),
871 if should_codegen_locally(tcx
, &instance
) {
872 self.output
.push(create_fn_mono_item(tcx
, instance
, source
));
875 mir
::TerminatorKind
::Goto { .. }
876 | mir
::TerminatorKind
::SwitchInt { .. }
877 | mir
::TerminatorKind
::Resume
878 | mir
::TerminatorKind
::Return
879 | mir
::TerminatorKind
::Unreachable
=> {}
880 mir
::TerminatorKind
::GeneratorDrop
881 | mir
::TerminatorKind
::Yield { .. }
882 | mir
::TerminatorKind
::FalseEdge { .. }
883 | mir
::TerminatorKind
::FalseUnwind { .. }
=> bug
!(),
886 self.super_terminator(terminator
, location
);
889 fn visit_operand(&mut self, operand
: &mir
::Operand
<'tcx
>, location
: Location
) {
890 self.super_operand(operand
, location
);
891 let limit
= self.tcx
.move_size_limit().0;
895 let limit
= Size
::from_bytes(limit
);
896 let ty
= operand
.ty(self.body
, self.tcx
);
897 let ty
= self.monomorphize(ty
);
898 let layout
= self.tcx
.layout_of(ty
::ParamEnv
::reveal_all().and(ty
));
899 if let Ok(layout
) = layout
{
900 if layout
.size
> limit
{
902 let source_info
= self.body
.source_info(location
);
903 debug
!(?source_info
);
904 let lint_root
= source_info
.scope
.lint_root(&self.body
.source_scopes
);
906 let Some(lint_root
) = lint_root
else {
907 // This happens when the issue is in a function from a foreign crate that
908 // we monomorphized in the current crate. We can't get a `HirId` for things
910 // FIXME: Find out where to report the lint on. Maybe simply crate-level lint root
911 // but correct span? This would make the lint at least accept crate-level lint attributes.
914 self.tcx
.struct_span_lint_hir(
919 let mut err
= lint
.build(&format
!("moving {} bytes", layout
.size
.bytes()));
920 err
.span_label(source_info
.span
, "value moved from here");
921 err
.note(&format
!(r
#"The current maximum size is {}, but it can be customized with the move_size_limit attribute: `#![move_size_limit = "..."]`"#, limit.bytes()));
931 _place_local
: &Local
,
932 _context
: mir
::visit
::PlaceContext
,
938 fn visit_drop_use
<'tcx
>(
941 is_direct_call
: bool
,
943 output
: &mut MonoItems
<'tcx
>,
945 let instance
= Instance
::resolve_drop_in_place(tcx
, ty
);
946 visit_instance_use(tcx
, instance
, is_direct_call
, source
, output
);
949 fn visit_fn_use
<'tcx
>(
952 is_direct_call
: bool
,
954 output
: &mut MonoItems
<'tcx
>,
956 if let ty
::FnDef(def_id
, substs
) = *ty
.kind() {
957 let instance
= if is_direct_call
{
958 ty
::Instance
::resolve(tcx
, ty
::ParamEnv
::reveal_all(), def_id
, substs
).unwrap().unwrap()
960 ty
::Instance
::resolve_for_fn_ptr(tcx
, ty
::ParamEnv
::reveal_all(), def_id
, substs
)
963 visit_instance_use(tcx
, instance
, is_direct_call
, source
, output
);
967 fn visit_instance_use
<'tcx
>(
969 instance
: ty
::Instance
<'tcx
>,
970 is_direct_call
: bool
,
972 output
: &mut MonoItems
<'tcx
>,
974 debug
!("visit_item_use({:?}, is_direct_call={:?})", instance
, is_direct_call
);
975 if !should_codegen_locally(tcx
, &instance
) {
980 ty
::InstanceDef
::Virtual(..) | ty
::InstanceDef
::Intrinsic(_
) => {
982 bug
!("{:?} being reified", instance
);
985 ty
::InstanceDef
::DropGlue(_
, None
) => {
986 // Don't need to emit noop drop glue if we are calling directly.
988 output
.push(create_fn_mono_item(tcx
, instance
, source
));
991 ty
::InstanceDef
::DropGlue(_
, Some(_
))
992 | ty
::InstanceDef
::VtableShim(..)
993 | ty
::InstanceDef
::ReifyShim(..)
994 | ty
::InstanceDef
::ClosureOnceShim { .. }
995 | ty
::InstanceDef
::Item(..)
996 | ty
::InstanceDef
::FnPtrShim(..)
997 | ty
::InstanceDef
::CloneShim(..) => {
998 output
.push(create_fn_mono_item(tcx
, instance
, source
));
1003 /// Returns `true` if we should codegen an instance in the local crate, or returns `false` if we
1004 /// can just link to the upstream crate and therefore don't need a mono item.
1005 fn should_codegen_locally
<'tcx
>(tcx
: TyCtxt
<'tcx
>, instance
: &Instance
<'tcx
>) -> bool
{
1006 let Some(def_id
) = instance
.def
.def_id_if_not_guaranteed_local_codegen() else {
1010 if tcx
.is_foreign_item(def_id
) {
1011 // Foreign items are always linked against, there's no way of instantiating them.
1015 if def_id
.is_local() {
1016 // Local items cannot be referred to locally without monomorphizing them locally.
1020 if tcx
.is_reachable_non_generic(def_id
)
1021 || instance
.polymorphize(tcx
).upstream_monomorphization(tcx
).is_some()
1023 // We can link to the item in question, no instance needed in this crate.
1027 if !tcx
.is_mir_available(def_id
) {
1028 bug
!("no MIR available for {:?}", def_id
);
1034 /// For a given pair of source and target type that occur in an unsizing coercion,
1035 /// this function finds the pair of types that determines the vtable linking
1038 /// For example, the source type might be `&SomeStruct` and the target type
1039 /// might be `&SomeTrait` in a cast like:
1041 /// let src: &SomeStruct = ...;
1042 /// let target = src as &SomeTrait;
1044 /// Then the output of this function would be (SomeStruct, SomeTrait) since for
1045 /// constructing the `target` fat-pointer we need the vtable for that pair.
1047 /// Things can get more complicated though because there's also the case where
1048 /// the unsized type occurs as a field:
1051 /// struct ComplexStruct<T: ?Sized> {
1058 /// In this case, if `T` is sized, `&ComplexStruct<T>` is a thin pointer. If `T`
1059 /// is unsized, `&SomeStruct` is a fat pointer, and the vtable it points to is
1060 /// for the pair of `T` (which is a trait) and the concrete type that `T` was
1061 /// originally coerced from:
1063 /// let src: &ComplexStruct<SomeStruct> = ...;
1064 /// let target = src as &ComplexStruct<SomeTrait>;
1066 /// Again, we want this `find_vtable_types_for_unsizing()` to provide the pair
1067 /// `(SomeStruct, SomeTrait)`.
1069 /// Finally, there is also the case of custom unsizing coercions, e.g., for
1070 /// smart pointers such as `Rc` and `Arc`.
1071 fn find_vtable_types_for_unsizing
<'tcx
>(
1073 source_ty
: Ty
<'tcx
>,
1074 target_ty
: Ty
<'tcx
>,
1075 ) -> (Ty
<'tcx
>, Ty
<'tcx
>) {
1076 let ptr_vtable
= |inner_source
: Ty
<'tcx
>, inner_target
: Ty
<'tcx
>| {
1077 let param_env
= ty
::ParamEnv
::reveal_all();
1078 let type_has_metadata
= |ty
: Ty
<'tcx
>| -> bool
{
1079 if ty
.is_sized(tcx
.at(DUMMY_SP
), param_env
) {
1082 let tail
= tcx
.struct_tail_erasing_lifetimes(ty
, param_env
);
1084 ty
::Foreign(..) => false,
1085 ty
::Str
| ty
::Slice(..) | ty
::Dynamic(..) => true,
1086 _
=> bug
!("unexpected unsized tail: {:?}", tail
),
1089 if type_has_metadata(inner_source
) {
1090 (inner_source
, inner_target
)
1092 tcx
.struct_lockstep_tails_erasing_lifetimes(inner_source
, inner_target
, param_env
)
1096 match (&source_ty
.kind(), &target_ty
.kind()) {
1097 (&ty
::Ref(_
, a
, _
), &ty
::Ref(_
, b
, _
) | &ty
::RawPtr(ty
::TypeAndMut { ty: b, .. }
))
1098 | (&ty
::RawPtr(ty
::TypeAndMut { ty: a, .. }
), &ty
::RawPtr(ty
::TypeAndMut { ty: b, .. }
)) => {
1101 (&ty
::Adt(def_a
, _
), &ty
::Adt(def_b
, _
)) if def_a
.is_box() && def_b
.is_box() => {
1102 ptr_vtable(source_ty
.boxed_ty(), target_ty
.boxed_ty())
1105 (&ty
::Adt(source_adt_def
, source_substs
), &ty
::Adt(target_adt_def
, target_substs
)) => {
1106 assert_eq
!(source_adt_def
, target_adt_def
);
1108 let CustomCoerceUnsized
::Struct(coerce_index
) =
1109 crate::custom_coerce_unsize_info(tcx
, source_ty
, target_ty
);
1111 let source_fields
= &source_adt_def
.non_enum_variant().fields
;
1112 let target_fields
= &target_adt_def
.non_enum_variant().fields
;
1115 coerce_index
< source_fields
.len() && source_fields
.len() == target_fields
.len()
1118 find_vtable_types_for_unsizing(
1120 source_fields
[coerce_index
].ty(tcx
, source_substs
),
1121 target_fields
[coerce_index
].ty(tcx
, target_substs
),
1125 "find_vtable_types_for_unsizing: invalid coercion {:?} -> {:?}",
1132 #[instrument(skip(tcx), level = "debug")]
1133 fn create_fn_mono_item
<'tcx
>(
1135 instance
: Instance
<'tcx
>,
1137 ) -> Spanned
<MonoItem
<'tcx
>> {
1138 debug
!("create_fn_mono_item(instance={})", instance
);
1140 let def_id
= instance
.def_id();
1141 if tcx
.sess
.opts
.debugging_opts
.profile_closures
&& def_id
.is_local() && tcx
.is_closure(def_id
)
1143 crate::util
::dump_closure_profile(tcx
, instance
);
1146 let respanned
= respan(source
, MonoItem
::Fn(instance
.polymorphize(tcx
)));
1152 /// Creates a `MonoItem` for each method that is referenced by the vtable for
1153 /// the given trait/impl pair.
1154 fn create_mono_items_for_vtable_methods
<'tcx
>(
1159 output
: &mut MonoItems
<'tcx
>,
1161 assert
!(!trait_ty
.has_escaping_bound_vars() && !impl_ty
.has_escaping_bound_vars());
1163 if let ty
::Dynamic(ref trait_ty
, ..) = trait_ty
.kind() {
1164 if let Some(principal
) = trait_ty
.principal() {
1165 let poly_trait_ref
= principal
.with_self_ty(tcx
, impl_ty
);
1166 assert
!(!poly_trait_ref
.has_escaping_bound_vars());
1168 // Walk all methods of the trait, including those of its supertraits
1169 let entries
= tcx
.vtable_entries(poly_trait_ref
);
1170 let methods
= entries
1172 .filter_map(|entry
| match entry
{
1173 VtblEntry
::MetadataDropInPlace
1174 | VtblEntry
::MetadataSize
1175 | VtblEntry
::MetadataAlign
1176 | VtblEntry
::Vacant
=> None
,
1177 VtblEntry
::TraitVPtr(_
) => {
1178 // all super trait items already covered, so skip them.
1181 VtblEntry
::Method(instance
) => {
1182 Some(*instance
).filter(|instance
| should_codegen_locally(tcx
, instance
))
1185 .map(|item
| create_fn_mono_item(tcx
, item
, source
));
1186 output
.extend(methods
);
1189 // Also add the destructor.
1190 visit_drop_use(tcx
, impl_ty
, false, source
, output
);
1194 //=-----------------------------------------------------------------------------
1196 //=-----------------------------------------------------------------------------
1198 struct RootCollector
<'a
, 'tcx
> {
1200 mode
: MonoItemCollectionMode
,
1201 output
: &'a
mut MonoItems
<'tcx
>,
1202 entry_fn
: Option
<(DefId
, EntryFnType
)>,
1205 impl<'v
> RootCollector
<'_
, 'v
> {
1206 fn process_item(&mut self, id
: hir
::ItemId
) {
1207 match self.tcx
.def_kind(id
.def_id
) {
1208 DefKind
::Enum
| DefKind
::Struct
| DefKind
::Union
=> {
1209 let item
= self.tcx
.hir().item(id
);
1211 hir
::ItemKind
::Enum(_
, ref generics
)
1212 | hir
::ItemKind
::Struct(_
, ref generics
)
1213 | hir
::ItemKind
::Union(_
, ref generics
) => {
1214 if generics
.params
.is_empty() {
1215 if self.mode
== MonoItemCollectionMode
::Eager
{
1217 "RootCollector: ADT drop-glue for {}",
1218 self.tcx
.def_path_str(item
.def_id
.to_def_id())
1222 Instance
::new(item
.def_id
.to_def_id(), InternalSubsts
::empty())
1223 .ty(self.tcx
, ty
::ParamEnv
::reveal_all());
1224 visit_drop_use(self.tcx
, ty
, true, DUMMY_SP
, self.output
);
1231 DefKind
::GlobalAsm
=> {
1233 "RootCollector: ItemKind::GlobalAsm({})",
1234 self.tcx
.def_path_str(id
.def_id
.to_def_id())
1236 self.output
.push(dummy_spanned(MonoItem
::GlobalAsm(id
)));
1238 DefKind
::Static(..) => {
1240 "RootCollector: ItemKind::Static({})",
1241 self.tcx
.def_path_str(id
.def_id
.to_def_id())
1243 self.output
.push(dummy_spanned(MonoItem
::Static(id
.def_id
.to_def_id())));
1246 // const items only generate mono items if they are
1247 // actually used somewhere. Just declaring them is insufficient.
1249 // but even just declaring them must collect the items they refer to
1250 if let Ok(val
) = self.tcx
.const_eval_poly(id
.def_id
.to_def_id()) {
1251 collect_const_value(self.tcx
, val
, &mut self.output
);
1255 if self.mode
== MonoItemCollectionMode
::Eager
{
1256 let item
= self.tcx
.hir().item(id
);
1257 create_mono_items_for_default_impls(self.tcx
, item
, self.output
);
1261 self.push_if_root(id
.def_id
);
1267 fn process_impl_item(&mut self, id
: hir
::ImplItemId
) {
1268 if matches
!(self.tcx
.def_kind(id
.def_id
), DefKind
::AssocFn
) {
1269 self.push_if_root(id
.def_id
);
1273 fn is_root(&self, def_id
: LocalDefId
) -> bool
{
1274 !item_requires_monomorphization(self.tcx
, def_id
)
1275 && match self.mode
{
1276 MonoItemCollectionMode
::Eager
=> true,
1277 MonoItemCollectionMode
::Lazy
=> {
1278 self.entry_fn
.and_then(|(id
, _
)| id
.as_local()) == Some(def_id
)
1279 || self.tcx
.is_reachable_non_generic(def_id
)
1282 .codegen_fn_attrs(def_id
)
1284 .contains(CodegenFnAttrFlags
::RUSTC_STD_INTERNAL_SYMBOL
)
1289 /// If `def_id` represents a root, pushes it onto the list of
1290 /// outputs. (Note that all roots must be monomorphic.)
1291 #[instrument(skip(self), level = "debug")]
1292 fn push_if_root(&mut self, def_id
: LocalDefId
) {
1293 if self.is_root(def_id
) {
1294 debug
!("RootCollector::push_if_root: found root def_id={:?}", def_id
);
1296 let instance
= Instance
::mono(self.tcx
, def_id
.to_def_id());
1297 self.output
.push(create_fn_mono_item(self.tcx
, instance
, DUMMY_SP
));
1301 /// As a special case, when/if we encounter the
1302 /// `main()` function, we also have to generate a
1303 /// monomorphized copy of the start lang item based on
1304 /// the return type of `main`. This is not needed when
1305 /// the user writes their own `start` manually.
1306 fn push_extra_entry_roots(&mut self) {
1307 let Some((main_def_id
, EntryFnType
::Main
)) = self.entry_fn
else {
1311 let start_def_id
= match self.tcx
.lang_items().require(LangItem
::Start
) {
1313 Err(err
) => self.tcx
.sess
.fatal(&err
),
1315 let main_ret_ty
= self.tcx
.fn_sig(main_def_id
).output();
1317 // Given that `main()` has no arguments,
1318 // then its return type cannot have
1319 // late-bound regions, since late-bound
1320 // regions must appear in the argument
1322 let main_ret_ty
= self.tcx
.normalize_erasing_regions(
1323 ty
::ParamEnv
::reveal_all(),
1324 main_ret_ty
.no_bound_vars().unwrap(),
1327 let start_instance
= Instance
::resolve(
1329 ty
::ParamEnv
::reveal_all(),
1331 self.tcx
.intern_substs(&[main_ret_ty
.into()]),
1336 self.output
.push(create_fn_mono_item(self.tcx
, start_instance
, DUMMY_SP
));
1340 fn item_requires_monomorphization(tcx
: TyCtxt
<'_
>, def_id
: LocalDefId
) -> bool
{
1341 let generics
= tcx
.generics_of(def_id
);
1342 generics
.requires_monomorphization(tcx
)
1345 fn create_mono_items_for_default_impls
<'tcx
>(
1347 item
: &'tcx hir
::Item
<'tcx
>,
1348 output
: &mut MonoItems
<'tcx
>,
1351 hir
::ItemKind
::Impl(ref impl_
) => {
1352 for param
in impl_
.generics
.params
{
1354 hir
::GenericParamKind
::Lifetime { .. }
=> {}
1355 hir
::GenericParamKind
::Type { .. }
| hir
::GenericParamKind
::Const { .. }
=> {
1362 "create_mono_items_for_default_impls(item={})",
1363 tcx
.def_path_str(item
.def_id
.to_def_id())
1366 if let Some(trait_ref
) = tcx
.impl_trait_ref(item
.def_id
) {
1367 let param_env
= ty
::ParamEnv
::reveal_all();
1368 let trait_ref
= tcx
.normalize_erasing_regions(param_env
, trait_ref
);
1369 let overridden_methods
= tcx
.impl_item_implementor_ids(item
.def_id
);
1370 for method
in tcx
.provided_trait_methods(trait_ref
.def_id
) {
1371 if overridden_methods
.contains_key(&method
.def_id
) {
1375 if tcx
.generics_of(method
.def_id
).own_requires_monomorphization() {
1380 InternalSubsts
::for_item(tcx
, method
.def_id
, |param
, _
| match param
.kind
{
1381 GenericParamDefKind
::Lifetime
=> tcx
.lifetimes
.re_erased
.into(),
1382 GenericParamDefKind
::Type { .. }
1383 | GenericParamDefKind
::Const { .. }
=> {
1384 trait_ref
.substs
[param
.index
as usize]
1387 let instance
= ty
::Instance
::resolve(tcx
, param_env
, method
.def_id
, substs
)
1391 let mono_item
= create_fn_mono_item(tcx
, instance
, DUMMY_SP
);
1392 if mono_item
.node
.is_instantiable(tcx
) && should_codegen_locally(tcx
, &instance
)
1394 output
.push(mono_item
);
1403 /// Scans the miri alloc in order to find function calls, closures, and drop-glue.
1404 fn collect_miri
<'tcx
>(tcx
: TyCtxt
<'tcx
>, alloc_id
: AllocId
, output
: &mut MonoItems
<'tcx
>) {
1405 match tcx
.global_alloc(alloc_id
) {
1406 GlobalAlloc
::Static(def_id
) => {
1407 assert
!(!tcx
.is_thread_local_static(def_id
));
1408 let instance
= Instance
::mono(tcx
, def_id
);
1409 if should_codegen_locally(tcx
, &instance
) {
1410 trace
!("collecting static {:?}", def_id
);
1411 output
.push(dummy_spanned(MonoItem
::Static(def_id
)));
1414 GlobalAlloc
::Memory(alloc
) => {
1415 trace
!("collecting {:?} with {:#?}", alloc_id
, alloc
);
1416 for &inner
in alloc
.inner().relocations().values() {
1417 rustc_data_structures
::stack
::ensure_sufficient_stack(|| {
1418 collect_miri(tcx
, inner
, output
);
1422 GlobalAlloc
::Function(fn_instance
) => {
1423 if should_codegen_locally(tcx
, &fn_instance
) {
1424 trace
!("collecting {:?} with {:#?}", alloc_id
, fn_instance
);
1425 output
.push(create_fn_mono_item(tcx
, fn_instance
, DUMMY_SP
));
1431 /// Scans the MIR in order to find function calls, closures, and drop-glue.
1432 #[instrument(skip(tcx, output), level = "debug")]
1433 fn collect_neighbours
<'tcx
>(
1435 instance
: Instance
<'tcx
>,
1436 output
: &mut MonoItems
<'tcx
>,
1438 let body
= tcx
.instance_mir(instance
.def
);
1439 MirNeighborCollector { tcx, body: &body, output, instance }
.visit_body(&body
);
1442 #[instrument(skip(tcx, output), level = "debug")]
1443 fn collect_const_value
<'tcx
>(
1445 value
: ConstValue
<'tcx
>,
1446 output
: &mut MonoItems
<'tcx
>,
1449 ConstValue
::Scalar(Scalar
::Ptr(ptr
, _size
)) => collect_miri(tcx
, ptr
.provenance
, output
),
1450 ConstValue
::Slice { data: alloc, start: _, end: _ }
| ConstValue
::ByRef { alloc, .. }
=> {
1451 for &id
in alloc
.inner().relocations().values() {
1452 collect_miri(tcx
, id
, output
);