1 use crate::dep_graph::{DepNode, WorkProduct, WorkProductId};
2 use crate::ich::{NodeIdHashingMode, StableHashingContext};
3 use crate::ty::{subst::InternalSubsts, Instance, InstanceDef, SymbolName, TyCtxt};
4 use rustc_attr::InlineAttr;
5 use rustc_data_structures::base_n;
6 use rustc_data_structures::fingerprint::Fingerprint;
7 use rustc_data_structures::fx::FxHashMap;
8 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
9 use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
10 use rustc_hir::{HirId, ItemId};
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 pub fn size_estimate(&self, tcx: TyCtxt<'tcx>) -> usize {
52 MonoItem::Fn(instance) => {
53 // Estimate the size of a function based on how many statements
55 tcx.instance_def_size_estimate(instance.def)
57 // Conservatively estimate the size of a static declaration
58 // or assembly to be 1.
59 MonoItem::Static(_) | MonoItem::GlobalAsm(_) => 1,
63 pub fn is_generic_fn(&self) -> bool {
65 MonoItem::Fn(ref instance) => instance.substs.non_erasable_generics().next().is_some(),
66 MonoItem::Static(..) | MonoItem::GlobalAsm(..) => false,
70 pub fn symbol_name(&self, tcx: TyCtxt<'tcx>) -> SymbolName<'tcx> {
72 MonoItem::Fn(instance) => tcx.symbol_name(instance),
73 MonoItem::Static(def_id) => tcx.symbol_name(Instance::mono(tcx, def_id)),
74 MonoItem::GlobalAsm(item_id) => {
75 SymbolName::new(tcx, &format!("global_asm_{:?}", item_id.def_id))
80 pub fn instantiation_mode(&self, tcx: TyCtxt<'tcx>) -> InstantiationMode {
81 let generate_cgu_internal_copies = tcx
86 .unwrap_or_else(|| tcx.sess.opts.optimize != OptLevel::No)
87 && !tcx.sess.link_dead_code();
90 MonoItem::Fn(ref instance) => {
91 let entry_def_id = tcx.entry_fn(()).map(|(id, _)| id);
92 // If this function isn't inlined or otherwise has an extern
93 // indicator, then we'll be creating a globally shared version.
94 if tcx.codegen_fn_attrs(instance.def_id()).contains_extern_indicator()
95 || !instance.def.generates_cgu_internal_copy(tcx)
96 || Some(instance.def_id()) == entry_def_id
98 return InstantiationMode::GloballyShared { may_conflict: false };
101 // At this point we don't have explicit linkage and we're an
102 // inlined function. If we're inlining into all CGUs then we'll
103 // be creating a local copy per CGU.
104 if generate_cgu_internal_copies {
105 return InstantiationMode::LocalCopy;
108 // Finally, if this is `#[inline(always)]` we're sure to respect
109 // that with an inline copy per CGU, but otherwise we'll be
110 // creating one copy of this `#[inline]` function which may
111 // conflict with upstream crates as it could be an exported
113 match tcx.codegen_fn_attrs(instance.def_id()).inline {
114 InlineAttr::Always => InstantiationMode::LocalCopy,
115 _ => InstantiationMode::GloballyShared { may_conflict: true },
118 MonoItem::Static(..) | MonoItem::GlobalAsm(..) => {
119 InstantiationMode::GloballyShared { may_conflict: false }
124 pub fn explicit_linkage(&self, tcx: TyCtxt<'tcx>) -> Option<Linkage> {
125 let def_id = match *self {
126 MonoItem::Fn(ref instance) => instance.def_id(),
127 MonoItem::Static(def_id) => def_id,
128 MonoItem::GlobalAsm(..) => return None,
131 let codegen_fn_attrs = tcx.codegen_fn_attrs(def_id);
132 codegen_fn_attrs.linkage
135 /// Returns `true` if this instance is instantiable - whether it has no unsatisfied
138 /// In order to codegen an item, all of its predicates must hold, because
139 /// otherwise the item does not make sense. Type-checking ensures that
140 /// the predicates of every item that is *used by* a valid item *do*
141 /// hold, so we can rely on that.
143 /// However, we codegen collector roots (reachable items) and functions
144 /// in vtables when they are seen, even if they are not used, and so they
145 /// might not be instantiable. For example, a programmer can define this
148 /// pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone {
149 /// <&mut () as Clone>::clone(&s);
152 /// That function can't be codegened, because the method `<&mut () as Clone>::clone`
153 /// does not exist. Luckily for us, that function can't ever be used,
154 /// because that would require for `&'a mut (): Clone` to hold, so we
155 /// can just not emit any code, or even a linker reference for it.
157 /// Similarly, if a vtable method has such a signature, and therefore can't
158 /// be used, we can just not emit it and have a placeholder (a null pointer,
159 /// which will never be accessed) in its place.
160 pub fn is_instantiable(&self, tcx: TyCtxt<'tcx>) -> bool {
161 debug!("is_instantiable({:?})", self);
162 let (def_id, substs) = match *self {
163 MonoItem::Fn(ref instance) => (instance.def_id(), instance.substs),
164 MonoItem::Static(def_id) => (def_id, InternalSubsts::empty()),
165 // global asm never has predicates
166 MonoItem::GlobalAsm(..) => return true,
169 !tcx.subst_and_check_impossible_predicates((def_id, &substs))
172 pub fn local_span(&self, tcx: TyCtxt<'tcx>) -> Option<Span> {
174 MonoItem::Fn(Instance { def, .. }) => {
175 def.def_id().as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
177 MonoItem::Static(def_id) => {
178 def_id.as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
180 MonoItem::GlobalAsm(item_id) => Some(item_id.hir_id()),
182 .map(|hir_id| tcx.hir().span(hir_id))
185 // Only used by rustc_codegen_cranelift
186 pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode {
187 crate::dep_graph::make_compile_mono_item(tcx, self)
190 /// Returns the item's `CrateNum`
191 pub fn krate(&self) -> CrateNum {
193 MonoItem::Fn(ref instance) => instance.def_id().krate,
194 MonoItem::Static(def_id) => def_id.krate,
195 MonoItem::GlobalAsm(..) => LOCAL_CRATE,
200 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for MonoItem<'tcx> {
201 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
202 ::std::mem::discriminant(self).hash_stable(hcx, hasher);
205 MonoItem::Fn(ref instance) => {
206 instance.hash_stable(hcx, hasher);
208 MonoItem::Static(def_id) => {
209 def_id.hash_stable(hcx, hasher);
211 MonoItem::GlobalAsm(item_id) => {
212 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
213 item_id.hash_stable(hcx, hasher);
220 impl<'tcx> fmt::Display for MonoItem<'tcx> {
221 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
223 MonoItem::Fn(instance) => write!(f, "fn {}", instance),
224 MonoItem::Static(def_id) => {
225 write!(f, "static {}", Instance::new(def_id, InternalSubsts::empty()))
227 MonoItem::GlobalAsm(..) => write!(f, "global_asm"),
233 pub struct CodegenUnit<'tcx> {
234 /// A name for this CGU. Incremental compilation requires that
235 /// name be unique amongst **all** crates. Therefore, it should
236 /// contain something unique to this crate (e.g., a module path)
237 /// as well as the crate name and disambiguator.
239 items: FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)>,
240 size_estimate: Option<usize>,
244 /// Specifies the linkage type for a `MonoItem`.
246 /// See <https://llvm.org/docs/LangRef.html#linkage-types> for more details about these variants.
247 #[derive(Copy, Clone, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)]
262 #[derive(Copy, Clone, PartialEq, Debug, HashStable)]
263 pub enum Visibility {
269 impl<'tcx> CodegenUnit<'tcx> {
271 pub fn new(name: Symbol) -> CodegenUnit<'tcx> {
272 CodegenUnit { name, items: Default::default(), size_estimate: None, primary: false }
275 pub fn name(&self) -> Symbol {
279 pub fn set_name(&mut self, name: Symbol) {
283 pub fn is_primary(&self) -> bool {
287 pub fn make_primary(&mut self) {
291 pub fn items(&self) -> &FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
295 pub fn items_mut(&mut self) -> &mut FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
299 pub fn mangle_name(human_readable_name: &str) -> String {
300 // We generate a 80 bit hash from the name. This should be enough to
301 // avoid collisions and is still reasonably short for filenames.
302 let mut hasher = StableHasher::new();
303 human_readable_name.hash(&mut hasher);
304 let hash: u128 = hasher.finish();
305 let hash = hash & ((1u128 << 80) - 1);
306 base_n::encode(hash, base_n::CASE_INSENSITIVE)
309 pub fn estimate_size(&mut self, tcx: TyCtxt<'tcx>) {
310 // Estimate the size of a codegen unit as (approximately) the number of MIR
311 // statements it corresponds to.
312 self.size_estimate = Some(self.items.keys().map(|mi| mi.size_estimate(tcx)).sum());
316 pub fn size_estimate(&self) -> usize {
317 // Should only be called if `estimate_size` has previously been called.
318 self.size_estimate.expect("estimate_size must be called before getting a size_estimate")
321 pub fn modify_size_estimate(&mut self, delta: usize) {
322 assert!(self.size_estimate.is_some());
323 if let Some(size_estimate) = self.size_estimate {
324 self.size_estimate = Some(size_estimate + delta);
328 pub fn contains_item(&self, item: &MonoItem<'tcx>) -> bool {
329 self.items().contains_key(item)
332 pub fn work_product_id(&self) -> WorkProductId {
333 WorkProductId::from_cgu_name(&self.name().as_str())
336 pub fn work_product(&self, tcx: TyCtxt<'_>) -> WorkProduct {
337 let work_product_id = self.work_product_id();
339 .previous_work_product(&work_product_id)
340 .unwrap_or_else(|| panic!("Could not find work-product for CGU `{}`", self.name()))
343 pub fn items_in_deterministic_order(
346 ) -> Vec<(MonoItem<'tcx>, (Linkage, Visibility))> {
347 // The codegen tests rely on items being process in the same order as
348 // they appear in the file, so for local items, we sort by node_id first
349 #[derive(PartialEq, Eq, PartialOrd, Ord)]
350 pub struct ItemSortKey<'tcx>(Option<HirId>, SymbolName<'tcx>);
352 fn item_sort_key<'tcx>(tcx: TyCtxt<'tcx>, item: MonoItem<'tcx>) -> ItemSortKey<'tcx> {
355 MonoItem::Fn(ref instance) => {
357 // We only want to take HirIds of user-defined
358 // instances into account. The others don't matter for
359 // the codegen tests and can even make item order
361 InstanceDef::Item(def) => def
364 .map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id)),
365 InstanceDef::VtableShim(..)
366 | InstanceDef::ReifyShim(..)
367 | InstanceDef::Intrinsic(..)
368 | InstanceDef::FnPtrShim(..)
369 | InstanceDef::Virtual(..)
370 | InstanceDef::ClosureOnceShim { .. }
371 | InstanceDef::DropGlue(..)
372 | InstanceDef::CloneShim(..) => None,
375 MonoItem::Static(def_id) => {
376 def_id.as_local().map(|def_id| tcx.hir().local_def_id_to_hir_id(def_id))
378 MonoItem::GlobalAsm(item_id) => Some(item_id.hir_id()),
380 item.symbol_name(tcx),
384 let mut items: Vec<_> = self.items().iter().map(|(&i, &l)| (i, l)).collect();
385 items.sort_by_cached_key(|&(i, _)| item_sort_key(tcx, i));
389 pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode {
390 crate::dep_graph::make_compile_codegen_unit(tcx, self.name())
394 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for CodegenUnit<'tcx> {
395 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
399 // The size estimate is not relevant to the hash
404 name.hash_stable(hcx, hasher);
406 let mut items: Vec<(Fingerprint, _)> = items
408 .map(|(mono_item, &attrs)| {
409 let mut hasher = StableHasher::new();
410 mono_item.hash_stable(hcx, &mut hasher);
411 let mono_item_fingerprint = hasher.finish();
412 (mono_item_fingerprint, attrs)
416 items.sort_unstable_by_key(|i| i.0);
417 items.hash_stable(hcx, hasher);
421 pub struct CodegenUnitNameBuilder<'tcx> {
423 cache: FxHashMap<CrateNum, String>,
426 impl CodegenUnitNameBuilder<'tcx> {
427 pub fn new(tcx: TyCtxt<'tcx>) -> Self {
428 CodegenUnitNameBuilder { tcx, cache: Default::default() }
431 /// CGU names should fulfill the following requirements:
432 /// - They should be able to act as a file name on any kind of file system
433 /// - They should not collide with other CGU names, even for different versions
434 /// of the same crate.
436 /// Consequently, we don't use special characters except for '.' and '-' and we
437 /// prefix each name with the crate-name and crate-disambiguator.
439 /// This function will build CGU names of the form:
442 /// <crate-name>.<crate-disambiguator>[-in-<local-crate-id>](-<component>)*[.<special-suffix>]
443 /// <local-crate-id> = <local-crate-name>.<local-crate-disambiguator>
446 /// The '.' before `<special-suffix>` makes sure that names with a special
447 /// suffix can never collide with a name built out of regular Rust
448 /// identifiers (e.g., module paths).
449 pub fn build_cgu_name<I, C, S>(
453 special_suffix: Option<S>,
456 I: IntoIterator<Item = C>,
460 let cgu_name = self.build_cgu_name_no_mangle(cnum, components, special_suffix);
462 if self.tcx.sess.opts.debugging_opts.human_readable_cgu_names {
465 Symbol::intern(&CodegenUnit::mangle_name(&cgu_name.as_str()))
469 /// Same as `CodegenUnit::build_cgu_name()` but will never mangle the
471 pub fn build_cgu_name_no_mangle<I, C, S>(
475 special_suffix: Option<S>,
478 I: IntoIterator<Item = C>,
484 let mut cgu_name = String::with_capacity(64);
486 // Start out with the crate name and disambiguator
488 let crate_prefix = self.cache.entry(cnum).or_insert_with(|| {
489 // Whenever the cnum is not LOCAL_CRATE we also mix in the
490 // local crate's ID. Otherwise there can be collisions between CGUs
491 // instantiating stuff for upstream crates.
492 let local_crate_id = if cnum != LOCAL_CRATE {
493 let local_crate_disambiguator = format!("{}", tcx.crate_disambiguator(LOCAL_CRATE));
494 format!("-in-{}.{}", tcx.crate_name(LOCAL_CRATE), &local_crate_disambiguator[0..8])
499 let crate_disambiguator = tcx.crate_disambiguator(cnum).to_string();
500 // Using a shortened disambiguator of about 40 bits
501 format!("{}.{}{}", tcx.crate_name(cnum), &crate_disambiguator[0..8], local_crate_id)
504 write!(cgu_name, "{}", crate_prefix).unwrap();
506 // Add the components
507 for component in components {
508 write!(cgu_name, "-{}", component).unwrap();
511 if let Some(special_suffix) = special_suffix {
512 // We add a dot in here so it cannot clash with anything in a regular
514 write!(cgu_name, ".{}", special_suffix).unwrap();
517 Symbol::intern(&cgu_name[..])