1 use crate::dep_graph::{DepNode, WorkProduct, WorkProductId};
2 use crate::ty::{subst::InternalSubsts, Instance, InstanceDef, SymbolName, TyCtxt};
3 use rustc_attr::InlineAttr;
4 use rustc_data_structures::base_n;
5 use rustc_data_structures::fingerprint::Fingerprint;
6 use rustc_data_structures::fx::FxHashMap;
7 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
8 use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
10 use rustc_query_system::ich::{NodeIdHashingMode, StableHashingContext};
11 use rustc_session::config::OptLevel;
12 use rustc_span::source_map::Span;
13 use rustc_span::symbol::Symbol;
17 /// Describes how a monomorphization will be instantiated in object files.
19 pub enum InstantiationMode {
20 /// There will be exactly one instance of the given MonoItem. It will have
21 /// external linkage so that it can be linked to from other codegen units.
23 /// In some compilation scenarios we may decide to take functions that
24 /// are typically `LocalCopy` and instead move them to `GloballyShared`
25 /// to avoid codegenning them a bunch of times. In this situation,
26 /// however, our local copy may conflict with other crates also
27 /// inlining the same function.
29 /// This flag indicates that this situation is occurring, and informs
30 /// symbol name calculation that some extra mangling is needed to
31 /// avoid conflicts. Note that this may eventually go away entirely if
32 /// ThinLTO enables us to *always* have a globally shared instance of a
33 /// function within one crate's compilation.
37 /// Each codegen unit containing a reference to the given MonoItem will
38 /// have its own private copy of the function (with internal linkage).
42 #[derive(PartialEq, Eq, Clone, Copy, Debug, Hash)]
43 pub enum MonoItem<'tcx> {
49 impl<'tcx> MonoItem<'tcx> {
50 /// Returns `true` if the mono item is user-defined (i.e. not compiler-generated, like shims).
51 pub fn is_user_defined(&self) -> bool {
53 MonoItem::Fn(instance) => matches!(instance.def, InstanceDef::Item(..)),
54 MonoItem::Static(..) | MonoItem::GlobalAsm(..) => true,
58 pub fn size_estimate(&self, tcx: TyCtxt<'tcx>) -> usize {
60 MonoItem::Fn(instance) => {
61 // Estimate the size of a function based on how many statements
63 tcx.instance_def_size_estimate(instance.def)
65 // Conservatively estimate the size of a static declaration
66 // or assembly to be 1.
67 MonoItem::Static(_) | MonoItem::GlobalAsm(_) => 1,
71 pub fn is_generic_fn(&self) -> bool {
73 MonoItem::Fn(ref instance) => instance.substs.non_erasable_generics().next().is_some(),
74 MonoItem::Static(..) | MonoItem::GlobalAsm(..) => false,
78 pub fn symbol_name(&self, tcx: TyCtxt<'tcx>) -> SymbolName<'tcx> {
80 MonoItem::Fn(instance) => tcx.symbol_name(instance),
81 MonoItem::Static(def_id) => tcx.symbol_name(Instance::mono(tcx, def_id)),
82 MonoItem::GlobalAsm(item_id) => {
83 SymbolName::new(tcx, &format!("global_asm_{:?}", item_id.def_id))
88 pub fn instantiation_mode(&self, tcx: TyCtxt<'tcx>) -> InstantiationMode {
89 let generate_cgu_internal_copies = tcx
94 .unwrap_or_else(|| tcx.sess.opts.optimize != OptLevel::No)
95 && !tcx.sess.link_dead_code();
98 MonoItem::Fn(ref instance) => {
99 let entry_def_id = tcx.entry_fn(()).map(|(id, _)| id);
100 // If this function isn't inlined or otherwise has an extern
101 // indicator, then we'll be creating a globally shared version.
102 if tcx.codegen_fn_attrs(instance.def_id()).contains_extern_indicator()
103 || !instance.def.generates_cgu_internal_copy(tcx)
104 || Some(instance.def_id()) == entry_def_id
106 return InstantiationMode::GloballyShared { may_conflict: false };
109 // At this point we don't have explicit linkage and we're an
110 // inlined function. If we're inlining into all CGUs then we'll
111 // be creating a local copy per CGU.
112 if generate_cgu_internal_copies {
113 return InstantiationMode::LocalCopy;
116 // Finally, if this is `#[inline(always)]` we're sure to respect
117 // that with an inline copy per CGU, but otherwise we'll be
118 // creating one copy of this `#[inline]` function which may
119 // conflict with upstream crates as it could be an exported
121 match tcx.codegen_fn_attrs(instance.def_id()).inline {
122 InlineAttr::Always => InstantiationMode::LocalCopy,
123 _ => InstantiationMode::GloballyShared { may_conflict: true },
126 MonoItem::Static(..) | MonoItem::GlobalAsm(..) => {
127 InstantiationMode::GloballyShared { may_conflict: false }
132 pub fn explicit_linkage(&self, tcx: TyCtxt<'tcx>) -> Option<Linkage> {
133 let def_id = match *self {
134 MonoItem::Fn(ref instance) => instance.def_id(),
135 MonoItem::Static(def_id) => def_id,
136 MonoItem::GlobalAsm(..) => return None,
139 let codegen_fn_attrs = tcx.codegen_fn_attrs(def_id);
140 codegen_fn_attrs.linkage
143 /// Returns `true` if this instance is instantiable - whether it has no unsatisfied
146 /// In order to codegen an item, all of its predicates must hold, because
147 /// otherwise the item does not make sense. Type-checking ensures that
148 /// the predicates of every item that is *used by* a valid item *do*
149 /// hold, so we can rely on that.
151 /// However, we codegen collector roots (reachable items) and functions
152 /// in vtables when they are seen, even if they are not used, and so they
153 /// might not be instantiable. For example, a programmer can define this
156 /// pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone {
157 /// <&mut () as Clone>::clone(&s);
160 /// That function can't be codegened, because the method `<&mut () as Clone>::clone`
161 /// does not exist. Luckily for us, that function can't ever be used,
162 /// because that would require for `&'a mut (): Clone` to hold, so we
163 /// can just not emit any code, or even a linker reference for it.
165 /// Similarly, if a vtable method has such a signature, and therefore can't
166 /// be used, we can just not emit it and have a placeholder (a null pointer,
167 /// which will never be accessed) in its place.
168 pub fn is_instantiable(&self, tcx: TyCtxt<'tcx>) -> bool {
169 debug!("is_instantiable({:?})", self);
170 let (def_id, substs) = match *self {
171 MonoItem::Fn(ref instance) => (instance.def_id(), instance.substs),
172 MonoItem::Static(def_id) => (def_id, InternalSubsts::empty()),
173 // global asm never has predicates
174 MonoItem::GlobalAsm(..) => return true,
177 !tcx.subst_and_check_impossible_predicates((def_id, &substs))
180 pub fn local_span(&self, tcx: TyCtxt<'tcx>) -> Option<Span> {
182 MonoItem::Fn(Instance { def, .. }) => {
183 def.def_id().as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
185 MonoItem::Static(def_id) => {
186 def_id.as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
188 MonoItem::GlobalAsm(item_id) => Some(item_id.hir_id()),
190 .map(|hir_id| tcx.hir().span(hir_id))
193 // Only used by rustc_codegen_cranelift
194 pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode {
195 crate::dep_graph::make_compile_mono_item(tcx, self)
198 /// Returns the item's `CrateNum`
199 pub fn krate(&self) -> CrateNum {
201 MonoItem::Fn(ref instance) => instance.def_id().krate,
202 MonoItem::Static(def_id) => def_id.krate,
203 MonoItem::GlobalAsm(..) => LOCAL_CRATE,
208 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for MonoItem<'tcx> {
209 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
210 ::std::mem::discriminant(self).hash_stable(hcx, hasher);
213 MonoItem::Fn(ref instance) => {
214 instance.hash_stable(hcx, hasher);
216 MonoItem::Static(def_id) => {
217 def_id.hash_stable(hcx, hasher);
219 MonoItem::GlobalAsm(item_id) => {
220 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
221 item_id.hash_stable(hcx, hasher);
228 impl<'tcx> fmt::Display for MonoItem<'tcx> {
229 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
231 MonoItem::Fn(instance) => write!(f, "fn {}", instance),
232 MonoItem::Static(def_id) => {
233 write!(f, "static {}", Instance::new(def_id, InternalSubsts::empty()))
235 MonoItem::GlobalAsm(..) => write!(f, "global_asm"),
241 pub struct CodegenUnit<'tcx> {
242 /// A name for this CGU. Incremental compilation requires that
243 /// name be unique amongst **all** crates. Therefore, it should
244 /// contain something unique to this crate (e.g., a module path)
245 /// as well as the crate name and disambiguator.
247 items: FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)>,
248 size_estimate: Option<usize>,
252 /// Specifies the linkage type for a `MonoItem`.
254 /// See <https://llvm.org/docs/LangRef.html#linkage-types> for more details about these variants.
255 #[derive(Copy, Clone, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)]
270 #[derive(Copy, Clone, PartialEq, Debug, HashStable)]
271 pub enum Visibility {
277 impl<'tcx> CodegenUnit<'tcx> {
279 pub fn new(name: Symbol) -> CodegenUnit<'tcx> {
280 CodegenUnit { name, items: Default::default(), size_estimate: None, primary: false }
283 pub fn name(&self) -> Symbol {
287 pub fn set_name(&mut self, name: Symbol) {
291 pub fn is_primary(&self) -> bool {
295 pub fn make_primary(&mut self) {
299 pub fn items(&self) -> &FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
303 pub fn items_mut(&mut self) -> &mut FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
307 pub fn mangle_name(human_readable_name: &str) -> String {
308 // We generate a 80 bit hash from the name. This should be enough to
309 // avoid collisions and is still reasonably short for filenames.
310 let mut hasher = StableHasher::new();
311 human_readable_name.hash(&mut hasher);
312 let hash: u128 = hasher.finish();
313 let hash = hash & ((1u128 << 80) - 1);
314 base_n::encode(hash, base_n::CASE_INSENSITIVE)
317 pub fn estimate_size(&mut self, tcx: TyCtxt<'tcx>) {
318 // Estimate the size of a codegen unit as (approximately) the number of MIR
319 // statements it corresponds to.
320 self.size_estimate = Some(self.items.keys().map(|mi| mi.size_estimate(tcx)).sum());
324 pub fn size_estimate(&self) -> usize {
325 // Should only be called if `estimate_size` has previously been called.
326 self.size_estimate.expect("estimate_size must be called before getting a size_estimate")
329 pub fn modify_size_estimate(&mut self, delta: usize) {
330 assert!(self.size_estimate.is_some());
331 if let Some(size_estimate) = self.size_estimate {
332 self.size_estimate = Some(size_estimate + delta);
336 pub fn contains_item(&self, item: &MonoItem<'tcx>) -> bool {
337 self.items().contains_key(item)
340 pub fn work_product_id(&self) -> WorkProductId {
341 WorkProductId::from_cgu_name(self.name().as_str())
344 pub fn work_product(&self, tcx: TyCtxt<'_>) -> WorkProduct {
345 let work_product_id = self.work_product_id();
347 .previous_work_product(&work_product_id)
348 .unwrap_or_else(|| panic!("Could not find work-product for CGU `{}`", self.name()))
351 pub fn items_in_deterministic_order(
354 ) -> Vec<(MonoItem<'tcx>, (Linkage, Visibility))> {
355 // The codegen tests rely on items being process in the same order as
356 // they appear in the file, so for local items, we sort by node_id first
357 #[derive(PartialEq, Eq, PartialOrd, Ord)]
358 pub struct ItemSortKey<'tcx>(Option<usize>, SymbolName<'tcx>);
360 fn item_sort_key<'tcx>(tcx: TyCtxt<'tcx>, item: MonoItem<'tcx>) -> ItemSortKey<'tcx> {
363 MonoItem::Fn(ref instance) => {
365 // We only want to take HirIds of user-defined
366 // instances into account. The others don't matter for
367 // the codegen tests and can even make item order
369 InstanceDef::Item(def) => Some(def.did.index.as_usize()),
370 InstanceDef::VtableShim(..)
371 | InstanceDef::ReifyShim(..)
372 | InstanceDef::Intrinsic(..)
373 | InstanceDef::FnPtrShim(..)
374 | InstanceDef::Virtual(..)
375 | InstanceDef::ClosureOnceShim { .. }
376 | InstanceDef::DropGlue(..)
377 | InstanceDef::CloneShim(..) => None,
380 MonoItem::Static(def_id) => Some(def_id.index.as_usize()),
381 MonoItem::GlobalAsm(item_id) => {
382 Some(item_id.def_id.to_def_id().index.as_usize())
385 item.symbol_name(tcx),
389 let mut items: Vec<_> = self.items().iter().map(|(&i, &l)| (i, l)).collect();
390 items.sort_by_cached_key(|&(i, _)| item_sort_key(tcx, i));
394 pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode {
395 crate::dep_graph::make_compile_codegen_unit(tcx, self.name())
399 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for CodegenUnit<'tcx> {
400 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
404 // The size estimate is not relevant to the hash
409 name.hash_stable(hcx, hasher);
411 let mut items: Vec<(Fingerprint, _)> = items
413 .map(|(mono_item, &attrs)| {
414 let mut hasher = StableHasher::new();
415 mono_item.hash_stable(hcx, &mut hasher);
416 let mono_item_fingerprint = hasher.finish();
417 (mono_item_fingerprint, attrs)
421 items.sort_unstable_by_key(|i| i.0);
422 items.hash_stable(hcx, hasher);
426 pub struct CodegenUnitNameBuilder<'tcx> {
428 cache: FxHashMap<CrateNum, String>,
431 impl<'tcx> CodegenUnitNameBuilder<'tcx> {
432 pub fn new(tcx: TyCtxt<'tcx>) -> Self {
433 CodegenUnitNameBuilder { tcx, cache: Default::default() }
436 /// CGU names should fulfill the following requirements:
437 /// - They should be able to act as a file name on any kind of file system
438 /// - They should not collide with other CGU names, even for different versions
439 /// of the same crate.
441 /// Consequently, we don't use special characters except for '.' and '-' and we
442 /// prefix each name with the crate-name and crate-disambiguator.
444 /// This function will build CGU names of the form:
447 /// <crate-name>.<crate-disambiguator>[-in-<local-crate-id>](-<component>)*[.<special-suffix>]
448 /// <local-crate-id> = <local-crate-name>.<local-crate-disambiguator>
451 /// The '.' before `<special-suffix>` makes sure that names with a special
452 /// suffix can never collide with a name built out of regular Rust
453 /// identifiers (e.g., module paths).
454 pub fn build_cgu_name<I, C, S>(
458 special_suffix: Option<S>,
461 I: IntoIterator<Item = C>,
465 let cgu_name = self.build_cgu_name_no_mangle(cnum, components, special_suffix);
467 if self.tcx.sess.opts.debugging_opts.human_readable_cgu_names {
470 Symbol::intern(&CodegenUnit::mangle_name(cgu_name.as_str()))
474 /// Same as `CodegenUnit::build_cgu_name()` but will never mangle the
476 pub fn build_cgu_name_no_mangle<I, C, S>(
480 special_suffix: Option<S>,
483 I: IntoIterator<Item = C>,
489 let mut cgu_name = String::with_capacity(64);
491 // Start out with the crate name and disambiguator
493 let crate_prefix = self.cache.entry(cnum).or_insert_with(|| {
494 // Whenever the cnum is not LOCAL_CRATE we also mix in the
495 // local crate's ID. Otherwise there can be collisions between CGUs
496 // instantiating stuff for upstream crates.
497 let local_crate_id = if cnum != LOCAL_CRATE {
498 let local_stable_crate_id = tcx.sess.local_stable_crate_id();
501 tcx.crate_name(LOCAL_CRATE),
502 local_stable_crate_id.to_u64() as u32,
508 let stable_crate_id = tcx.sess.local_stable_crate_id();
511 tcx.crate_name(cnum),
512 stable_crate_id.to_u64() as u32,
517 write!(cgu_name, "{}", crate_prefix).unwrap();
519 // Add the components
520 for component in components {
521 write!(cgu_name, "-{}", component).unwrap();
524 if let Some(special_suffix) = special_suffix {
525 // We add a dot in here so it cannot clash with anything in a regular
527 write!(cgu_name, ".{}", special_suffix).unwrap();
530 Symbol::intern(&cgu_name)