1 use crate::dep_graph::{DepConstructor, DepNode, WorkProduct, WorkProductId};
2 use crate::ich::{NodeIdHashingMode, StableHashingContext};
3 use crate::ty::print::obsolete::DefPathBasedNames;
4 use crate::ty::{subst::InternalSubsts, Instance, InstanceDef, SymbolName, TyCtxt};
5 use rustc_attr::InlineAttr;
6 use rustc_data_structures::base_n;
7 use rustc_data_structures::fingerprint::Fingerprint;
8 use rustc_data_structures::fx::FxHashMap;
9 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
10 use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
12 use rustc_session::config::OptLevel;
13 use rustc_span::source_map::Span;
14 use rustc_span::symbol::Symbol;
18 /// Describes how a monomorphization will be instantiated in object files.
20 pub enum InstantiationMode {
21 /// There will be exactly one instance of the given MonoItem. It will have
22 /// external linkage so that it can be linked to from other codegen units.
24 /// In some compilation scenarios we may decide to take functions that
25 /// are typically `LocalCopy` and instead move them to `GloballyShared`
26 /// to avoid codegenning them a bunch of times. In this situation,
27 /// however, our local copy may conflict with other crates also
28 /// inlining the same function.
30 /// This flag indicates that this situation is occurring, and informs
31 /// symbol name calculation that some extra mangling is needed to
32 /// avoid conflicts. Note that this may eventually go away entirely if
33 /// ThinLTO enables us to *always* have a globally shared instance of a
34 /// function within one crate's compilation.
38 /// Each codegen unit containing a reference to the given MonoItem will
39 /// have its own private copy of the function (with internal linkage).
43 #[derive(PartialEq, Eq, Clone, Copy, Debug, Hash)]
44 pub enum MonoItem<'tcx> {
50 impl<'tcx> MonoItem<'tcx> {
51 pub fn size_estimate(&self, tcx: TyCtxt<'tcx>) -> usize {
53 MonoItem::Fn(instance) => {
54 // Estimate the size of a function based on how many statements
56 tcx.instance_def_size_estimate(instance.def)
58 // Conservatively estimate the size of a static declaration
59 // or assembly to be 1.
60 MonoItem::Static(_) | MonoItem::GlobalAsm(_) => 1,
64 pub fn is_generic_fn(&self) -> bool {
66 MonoItem::Fn(ref instance) => instance.substs.non_erasable_generics().next().is_some(),
67 MonoItem::Static(..) | MonoItem::GlobalAsm(..) => false,
71 pub fn symbol_name(&self, tcx: TyCtxt<'tcx>) -> SymbolName<'tcx> {
73 MonoItem::Fn(instance) => tcx.symbol_name(instance),
74 MonoItem::Static(def_id) => tcx.symbol_name(Instance::mono(tcx, def_id)),
75 MonoItem::GlobalAsm(hir_id) => {
76 let def_id = tcx.hir().local_def_id(hir_id);
77 SymbolName::new(tcx, &format!("global_asm_{:?}", def_id))
82 pub fn instantiation_mode(&self, tcx: TyCtxt<'tcx>) -> InstantiationMode {
83 let generate_cgu_internal_copies = tcx
88 .unwrap_or_else(|| tcx.sess.opts.optimize != OptLevel::No)
89 && tcx.sess.opts.cg.link_dead_code != Some(true);
92 MonoItem::Fn(ref instance) => {
93 let entry_def_id = tcx.entry_fn(LOCAL_CRATE).map(|(id, _)| id);
94 // If this function isn't inlined or otherwise has an extern
95 // indicator, then we'll be creating a globally shared version.
96 if tcx.codegen_fn_attrs(instance.def_id()).contains_extern_indicator()
97 || !instance.def.generates_cgu_internal_copy(tcx)
98 || Some(instance.def_id()) == entry_def_id.map(LocalDefId::to_def_id)
100 return InstantiationMode::GloballyShared { may_conflict: false };
103 // At this point we don't have explicit linkage and we're an
104 // inlined function. If we're inlining into all CGUs then we'll
105 // be creating a local copy per CGU.
106 if generate_cgu_internal_copies {
107 return InstantiationMode::LocalCopy;
110 // Finally, if this is `#[inline(always)]` we're sure to respect
111 // that with an inline copy per CGU, but otherwise we'll be
112 // creating one copy of this `#[inline]` function which may
113 // conflict with upstream crates as it could be an exported
115 match tcx.codegen_fn_attrs(instance.def_id()).inline {
116 InlineAttr::Always => InstantiationMode::LocalCopy,
117 _ => InstantiationMode::GloballyShared { may_conflict: true },
120 MonoItem::Static(..) | MonoItem::GlobalAsm(..) => {
121 InstantiationMode::GloballyShared { may_conflict: false }
126 pub fn explicit_linkage(&self, tcx: TyCtxt<'tcx>) -> Option<Linkage> {
127 let def_id = match *self {
128 MonoItem::Fn(ref instance) => instance.def_id(),
129 MonoItem::Static(def_id) => def_id,
130 MonoItem::GlobalAsm(..) => return None,
133 let codegen_fn_attrs = tcx.codegen_fn_attrs(def_id);
134 codegen_fn_attrs.linkage
137 /// Returns `true` if this instance is instantiable - whether it has no unsatisfied
140 /// In order to codegen an item, all of its predicates must hold, because
141 /// otherwise the item does not make sense. Type-checking ensures that
142 /// the predicates of every item that is *used by* a valid item *do*
143 /// hold, so we can rely on that.
145 /// However, we codegen collector roots (reachable items) and functions
146 /// in vtables when they are seen, even if they are not used, and so they
147 /// might not be instantiable. For example, a programmer can define this
150 /// pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone {
151 /// <&mut () as Clone>::clone(&s);
154 /// That function can't be codegened, because the method `<&mut () as Clone>::clone`
155 /// does not exist. Luckily for us, that function can't ever be used,
156 /// because that would require for `&'a mut (): Clone` to hold, so we
157 /// can just not emit any code, or even a linker reference for it.
159 /// Similarly, if a vtable method has such a signature, and therefore can't
160 /// be used, we can just not emit it and have a placeholder (a null pointer,
161 /// which will never be accessed) in its place.
162 pub fn is_instantiable(&self, tcx: TyCtxt<'tcx>) -> bool {
163 debug!("is_instantiable({:?})", self);
164 let (def_id, substs) = match *self {
165 MonoItem::Fn(ref instance) => (instance.def_id(), instance.substs),
166 MonoItem::Static(def_id) => (def_id, InternalSubsts::empty()),
167 // global asm never has predicates
168 MonoItem::GlobalAsm(..) => return true,
171 !tcx.subst_and_check_impossible_predicates((def_id, &substs))
174 pub fn to_string(&self, tcx: TyCtxt<'tcx>, debug: bool) -> String {
176 MonoItem::Fn(instance) => to_string_internal(tcx, "fn ", instance, debug),
177 MonoItem::Static(def_id) => {
178 let instance = Instance::new(def_id, tcx.intern_substs(&[]));
179 to_string_internal(tcx, "static ", instance, debug)
181 MonoItem::GlobalAsm(..) => "global_asm".to_string(),
184 fn to_string_internal<'tcx>(
187 instance: Instance<'tcx>,
190 let mut result = String::with_capacity(32);
191 result.push_str(prefix);
192 let printer = DefPathBasedNames::new(tcx, false, false);
193 printer.push_instance_as_string(instance, &mut result, debug);
198 pub fn local_span(&self, tcx: TyCtxt<'tcx>) -> Option<Span> {
200 MonoItem::Fn(Instance { def, .. }) => {
201 def.def_id().as_local().map(|def_id| tcx.hir().as_local_hir_id(def_id))
203 MonoItem::Static(def_id) => {
204 def_id.as_local().map(|def_id| tcx.hir().as_local_hir_id(def_id))
206 MonoItem::GlobalAsm(hir_id) => Some(hir_id),
208 .map(|hir_id| tcx.hir().span(hir_id))
212 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for MonoItem<'tcx> {
213 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
214 ::std::mem::discriminant(self).hash_stable(hcx, hasher);
217 MonoItem::Fn(ref instance) => {
218 instance.hash_stable(hcx, hasher);
220 MonoItem::Static(def_id) => {
221 def_id.hash_stable(hcx, hasher);
223 MonoItem::GlobalAsm(node_id) => {
224 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
225 node_id.hash_stable(hcx, hasher);
232 pub struct CodegenUnit<'tcx> {
233 /// A name for this CGU. Incremental compilation requires that
234 /// name be unique amongst **all** crates. Therefore, it should
235 /// contain something unique to this crate (e.g., a module path)
236 /// as well as the crate name and disambiguator.
238 items: FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)>,
239 size_estimate: Option<usize>,
242 /// Specifies the linkage type for a `MonoItem`.
244 /// See https://llvm.org/docs/LangRef.html#linkage-types for more details about these variants.
245 #[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable, HashStable)]
260 #[derive(Copy, Clone, PartialEq, Debug, HashStable)]
261 pub enum Visibility {
267 impl<'tcx> CodegenUnit<'tcx> {
268 pub fn new(name: Symbol) -> CodegenUnit<'tcx> {
269 CodegenUnit { name, items: Default::default(), size_estimate: None }
272 pub fn name(&self) -> Symbol {
276 pub fn set_name(&mut self, name: Symbol) {
280 pub fn items(&self) -> &FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
284 pub fn items_mut(&mut self) -> &mut FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
288 pub fn mangle_name(human_readable_name: &str) -> String {
289 // We generate a 80 bit hash from the name. This should be enough to
290 // avoid collisions and is still reasonably short for filenames.
291 let mut hasher = StableHasher::new();
292 human_readable_name.hash(&mut hasher);
293 let hash: u128 = hasher.finish();
294 let hash = hash & ((1u128 << 80) - 1);
295 base_n::encode(hash, base_n::CASE_INSENSITIVE)
298 pub fn estimate_size(&mut self, tcx: TyCtxt<'tcx>) {
299 // Estimate the size of a codegen unit as (approximately) the number of MIR
300 // statements it corresponds to.
301 self.size_estimate = Some(self.items.keys().map(|mi| mi.size_estimate(tcx)).sum());
304 pub fn size_estimate(&self) -> usize {
305 // Should only be called if `estimate_size` has previously been called.
306 self.size_estimate.expect("estimate_size must be called before getting a size_estimate")
309 pub fn modify_size_estimate(&mut self, delta: usize) {
310 assert!(self.size_estimate.is_some());
311 if let Some(size_estimate) = self.size_estimate {
312 self.size_estimate = Some(size_estimate + delta);
316 pub fn contains_item(&self, item: &MonoItem<'tcx>) -> bool {
317 self.items().contains_key(item)
320 pub fn work_product_id(&self) -> WorkProductId {
321 WorkProductId::from_cgu_name(&self.name().as_str())
324 pub fn work_product(&self, tcx: TyCtxt<'_>) -> WorkProduct {
325 let work_product_id = self.work_product_id();
327 .previous_work_product(&work_product_id)
328 .unwrap_or_else(|| panic!("Could not find work-product for CGU `{}`", self.name()))
331 pub fn items_in_deterministic_order(
334 ) -> Vec<(MonoItem<'tcx>, (Linkage, Visibility))> {
335 // The codegen tests rely on items being process in the same order as
336 // they appear in the file, so for local items, we sort by node_id first
337 #[derive(PartialEq, Eq, PartialOrd, Ord)]
338 pub struct ItemSortKey<'tcx>(Option<HirId>, SymbolName<'tcx>);
340 fn item_sort_key<'tcx>(tcx: TyCtxt<'tcx>, item: MonoItem<'tcx>) -> ItemSortKey<'tcx> {
343 MonoItem::Fn(ref instance) => {
345 // We only want to take HirIds of user-defined
346 // instances into account. The others don't matter for
347 // the codegen tests and can even make item order
349 InstanceDef::Item(def) => {
350 def.did.as_local().map(|def_id| tcx.hir().as_local_hir_id(def_id))
352 InstanceDef::VtableShim(..)
353 | InstanceDef::ReifyShim(..)
354 | InstanceDef::Intrinsic(..)
355 | InstanceDef::FnPtrShim(..)
356 | InstanceDef::Virtual(..)
357 | InstanceDef::ClosureOnceShim { .. }
358 | InstanceDef::DropGlue(..)
359 | InstanceDef::CloneShim(..) => None,
362 MonoItem::Static(def_id) => {
363 def_id.as_local().map(|def_id| tcx.hir().as_local_hir_id(def_id))
365 MonoItem::GlobalAsm(hir_id) => Some(hir_id),
367 item.symbol_name(tcx),
371 let mut items: Vec<_> = self.items().iter().map(|(&i, &l)| (i, l)).collect();
372 items.sort_by_cached_key(|&(i, _)| item_sort_key(tcx, i));
376 pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode {
377 DepConstructor::CompileCodegenUnit(tcx, self.name())
381 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for CodegenUnit<'tcx> {
382 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
386 // The size estimate is not relevant to the hash
390 name.hash_stable(hcx, hasher);
392 let mut items: Vec<(Fingerprint, _)> = items
394 .map(|(mono_item, &attrs)| {
395 let mut hasher = StableHasher::new();
396 mono_item.hash_stable(hcx, &mut hasher);
397 let mono_item_fingerprint = hasher.finish();
398 (mono_item_fingerprint, attrs)
402 items.sort_unstable_by_key(|i| i.0);
403 items.hash_stable(hcx, hasher);
407 pub struct CodegenUnitNameBuilder<'tcx> {
409 cache: FxHashMap<CrateNum, String>,
412 impl CodegenUnitNameBuilder<'tcx> {
413 pub fn new(tcx: TyCtxt<'tcx>) -> Self {
414 CodegenUnitNameBuilder { tcx, cache: Default::default() }
417 /// CGU names should fulfill the following requirements:
418 /// - They should be able to act as a file name on any kind of file system
419 /// - They should not collide with other CGU names, even for different versions
420 /// of the same crate.
422 /// Consequently, we don't use special characters except for '.' and '-' and we
423 /// prefix each name with the crate-name and crate-disambiguator.
425 /// This function will build CGU names of the form:
428 /// <crate-name>.<crate-disambiguator>[-in-<local-crate-id>](-<component>)*[.<special-suffix>]
429 /// <local-crate-id> = <local-crate-name>.<local-crate-disambiguator>
432 /// The '.' before `<special-suffix>` makes sure that names with a special
433 /// suffix can never collide with a name built out of regular Rust
434 /// identifiers (e.g., module paths).
435 pub fn build_cgu_name<I, C, S>(
439 special_suffix: Option<S>,
442 I: IntoIterator<Item = C>,
446 let cgu_name = self.build_cgu_name_no_mangle(cnum, components, special_suffix);
448 if self.tcx.sess.opts.debugging_opts.human_readable_cgu_names {
451 Symbol::intern(&CodegenUnit::mangle_name(&cgu_name.as_str()))
455 /// Same as `CodegenUnit::build_cgu_name()` but will never mangle the
457 pub fn build_cgu_name_no_mangle<I, C, S>(
461 special_suffix: Option<S>,
464 I: IntoIterator<Item = C>,
470 let mut cgu_name = String::with_capacity(64);
472 // Start out with the crate name and disambiguator
474 let crate_prefix = self.cache.entry(cnum).or_insert_with(|| {
475 // Whenever the cnum is not LOCAL_CRATE we also mix in the
476 // local crate's ID. Otherwise there can be collisions between CGUs
477 // instantiating stuff for upstream crates.
478 let local_crate_id = if cnum != LOCAL_CRATE {
479 let local_crate_disambiguator = format!("{}", tcx.crate_disambiguator(LOCAL_CRATE));
480 format!("-in-{}.{}", tcx.crate_name(LOCAL_CRATE), &local_crate_disambiguator[0..8])
485 let crate_disambiguator = tcx.crate_disambiguator(cnum).to_string();
486 // Using a shortened disambiguator of about 40 bits
487 format!("{}.{}{}", tcx.crate_name(cnum), &crate_disambiguator[0..8], local_crate_id)
490 write!(cgu_name, "{}", crate_prefix).unwrap();
492 // Add the components
493 for component in components {
494 write!(cgu_name, "-{}", component).unwrap();
497 if let Some(special_suffix) = special_suffix {
498 // We add a dot in here so it cannot clash with anything in a regular
500 write!(cgu_name, ".{}", special_suffix).unwrap();
503 Symbol::intern(&cgu_name[..])