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_index::vec::Idx;
11 use rustc_query_system::ich::StableHashingContext;
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, HashStable)]
44 pub enum MonoItem<'tcx> {
50 impl<'tcx> MonoItem<'tcx> {
51 /// Returns `true` if the mono item is user-defined (i.e. not compiler-generated, like shims).
52 pub fn is_user_defined(&self) -> bool {
54 MonoItem::Fn(instance) => matches!(instance.def, InstanceDef::Item(..)),
55 MonoItem::Static(..) | MonoItem::GlobalAsm(..) => true,
59 pub fn size_estimate(&self, tcx: TyCtxt<'tcx>) -> usize {
61 MonoItem::Fn(instance) => {
62 // Estimate the size of a function based on how many statements
64 tcx.instance_def_size_estimate(instance.def)
66 // Conservatively estimate the size of a static declaration
67 // or assembly to be 1.
68 MonoItem::Static(_) | MonoItem::GlobalAsm(_) => 1,
72 pub fn is_generic_fn(&self) -> bool {
74 MonoItem::Fn(ref instance) => instance.substs.non_erasable_generics().next().is_some(),
75 MonoItem::Static(..) | MonoItem::GlobalAsm(..) => false,
79 pub fn symbol_name(&self, tcx: TyCtxt<'tcx>) -> SymbolName<'tcx> {
81 MonoItem::Fn(instance) => tcx.symbol_name(instance),
82 MonoItem::Static(def_id) => tcx.symbol_name(Instance::mono(tcx, def_id)),
83 MonoItem::GlobalAsm(item_id) => {
84 SymbolName::new(tcx, &format!("global_asm_{:?}", item_id.owner_id))
89 pub fn instantiation_mode(&self, tcx: TyCtxt<'tcx>) -> InstantiationMode {
90 let generate_cgu_internal_copies = tcx
95 .unwrap_or_else(|| tcx.sess.opts.optimize != OptLevel::No)
96 && !tcx.sess.link_dead_code();
99 MonoItem::Fn(ref instance) => {
100 let entry_def_id = tcx.entry_fn(()).map(|(id, _)| id);
101 // If this function isn't inlined or otherwise has an extern
102 // indicator, then we'll be creating a globally shared version.
103 if tcx.codegen_fn_attrs(instance.def_id()).contains_extern_indicator()
104 || !instance.def.generates_cgu_internal_copy(tcx)
105 || Some(instance.def_id()) == entry_def_id
107 return InstantiationMode::GloballyShared { may_conflict: false };
110 // At this point we don't have explicit linkage and we're an
111 // inlined function. If we're inlining into all CGUs then we'll
112 // be creating a local copy per CGU.
113 if generate_cgu_internal_copies {
114 return InstantiationMode::LocalCopy;
117 // Finally, if this is `#[inline(always)]` we're sure to respect
118 // that with an inline copy per CGU, but otherwise we'll be
119 // creating one copy of this `#[inline]` function which may
120 // conflict with upstream crates as it could be an exported
122 match tcx.codegen_fn_attrs(instance.def_id()).inline {
123 InlineAttr::Always => InstantiationMode::LocalCopy,
124 _ => InstantiationMode::GloballyShared { may_conflict: true },
127 MonoItem::Static(..) | MonoItem::GlobalAsm(..) => {
128 InstantiationMode::GloballyShared { may_conflict: false }
133 pub fn explicit_linkage(&self, tcx: TyCtxt<'tcx>) -> Option<Linkage> {
134 let def_id = match *self {
135 MonoItem::Fn(ref instance) => instance.def_id(),
136 MonoItem::Static(def_id) => def_id,
137 MonoItem::GlobalAsm(..) => return None,
140 let codegen_fn_attrs = tcx.codegen_fn_attrs(def_id);
141 codegen_fn_attrs.linkage
144 /// Returns `true` if this instance is instantiable - whether it has no unsatisfied
147 /// In order to codegen an item, all of its predicates must hold, because
148 /// otherwise the item does not make sense. Type-checking ensures that
149 /// the predicates of every item that is *used by* a valid item *do*
150 /// hold, so we can rely on that.
152 /// However, we codegen collector roots (reachable items) and functions
153 /// in vtables when they are seen, even if they are not used, and so they
154 /// might not be instantiable. For example, a programmer can define this
157 /// pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone {
158 /// <&mut () as Clone>::clone(&s);
161 /// That function can't be codegened, because the method `<&mut () as Clone>::clone`
162 /// does not exist. Luckily for us, that function can't ever be used,
163 /// because that would require for `&'a mut (): Clone` to hold, so we
164 /// can just not emit any code, or even a linker reference for it.
166 /// Similarly, if a vtable method has such a signature, and therefore can't
167 /// be used, we can just not emit it and have a placeholder (a null pointer,
168 /// which will never be accessed) in its place.
169 pub fn is_instantiable(&self, tcx: TyCtxt<'tcx>) -> bool {
170 debug!("is_instantiable({:?})", self);
171 let (def_id, substs) = match *self {
172 MonoItem::Fn(ref instance) => (instance.def_id(), instance.substs),
173 MonoItem::Static(def_id) => (def_id, InternalSubsts::empty()),
174 // global asm never has predicates
175 MonoItem::GlobalAsm(..) => return true,
178 !tcx.subst_and_check_impossible_predicates((def_id, &substs))
181 pub fn local_span(&self, tcx: TyCtxt<'tcx>) -> Option<Span> {
183 MonoItem::Fn(Instance { def, .. }) => def.def_id().as_local(),
184 MonoItem::Static(def_id) => def_id.as_local(),
185 MonoItem::GlobalAsm(item_id) => Some(item_id.owner_id.def_id),
187 .map(|def_id| tcx.def_span(def_id))
190 // Only used by rustc_codegen_cranelift
191 pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode {
192 crate::dep_graph::make_compile_mono_item(tcx, self)
195 /// Returns the item's `CrateNum`
196 pub fn krate(&self) -> CrateNum {
198 MonoItem::Fn(ref instance) => instance.def_id().krate,
199 MonoItem::Static(def_id) => def_id.krate,
200 MonoItem::GlobalAsm(..) => LOCAL_CRATE,
205 impl<'tcx> fmt::Display for MonoItem<'tcx> {
206 fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result {
208 MonoItem::Fn(instance) => write!(f, "fn {}", instance),
209 MonoItem::Static(def_id) => {
210 write!(f, "static {}", Instance::new(def_id, InternalSubsts::empty()))
212 MonoItem::GlobalAsm(..) => write!(f, "global_asm"),
218 pub struct CodegenUnit<'tcx> {
219 /// A name for this CGU. Incremental compilation requires that
220 /// name be unique amongst **all** crates. Therefore, it should
221 /// contain something unique to this crate (e.g., a module path)
222 /// as well as the crate name and disambiguator.
224 items: FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)>,
225 size_estimate: Option<usize>,
227 /// True if this is CGU is used to hold code coverage information for dead code,
229 is_code_coverage_dead_code_cgu: bool,
232 /// Specifies the linkage type for a `MonoItem`.
234 /// See <https://llvm.org/docs/LangRef.html#linkage-types> for more details about these variants.
235 #[derive(Copy, Clone, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)]
250 #[derive(Copy, Clone, PartialEq, Debug, HashStable)]
251 pub enum Visibility {
257 impl<'tcx> CodegenUnit<'tcx> {
259 pub fn new(name: Symbol) -> CodegenUnit<'tcx> {
262 items: Default::default(),
265 is_code_coverage_dead_code_cgu: false,
269 pub fn name(&self) -> Symbol {
273 pub fn set_name(&mut self, name: Symbol) {
277 pub fn is_primary(&self) -> bool {
281 pub fn make_primary(&mut self) {
285 pub fn items(&self) -> &FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
289 pub fn items_mut(&mut self) -> &mut FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
293 pub fn is_code_coverage_dead_code_cgu(&self) -> bool {
294 self.is_code_coverage_dead_code_cgu
297 /// Marks this CGU as the one used to contain code coverage information for dead code.
298 pub fn make_code_coverage_dead_code_cgu(&mut self) {
299 self.is_code_coverage_dead_code_cgu = true;
302 pub fn mangle_name(human_readable_name: &str) -> String {
303 // We generate a 80 bit hash from the name. This should be enough to
304 // avoid collisions and is still reasonably short for filenames.
305 let mut hasher = StableHasher::new();
306 human_readable_name.hash(&mut hasher);
307 let hash: u128 = hasher.finish();
308 let hash = hash & ((1u128 << 80) - 1);
309 base_n::encode(hash, base_n::CASE_INSENSITIVE)
312 pub fn estimate_size(&mut self, tcx: TyCtxt<'tcx>) {
313 // Estimate the size of a codegen unit as (approximately) the number of MIR
314 // statements it corresponds to.
315 self.size_estimate = Some(self.items.keys().map(|mi| mi.size_estimate(tcx)).sum());
319 pub fn size_estimate(&self) -> usize {
320 // Should only be called if `estimate_size` has previously been called.
321 self.size_estimate.expect("estimate_size must be called before getting a size_estimate")
324 pub fn modify_size_estimate(&mut self, delta: usize) {
325 assert!(self.size_estimate.is_some());
326 if let Some(size_estimate) = self.size_estimate {
327 self.size_estimate = Some(size_estimate + delta);
331 pub fn contains_item(&self, item: &MonoItem<'tcx>) -> bool {
332 self.items().contains_key(item)
335 pub fn work_product_id(&self) -> WorkProductId {
336 WorkProductId::from_cgu_name(self.name().as_str())
339 pub fn previous_work_product(&self, tcx: TyCtxt<'_>) -> WorkProduct {
340 let work_product_id = self.work_product_id();
342 .previous_work_product(&work_product_id)
343 .unwrap_or_else(|| panic!("Could not find work-product for CGU `{}`", self.name()))
346 pub fn items_in_deterministic_order(
349 ) -> Vec<(MonoItem<'tcx>, (Linkage, Visibility))> {
350 // The codegen tests rely on items being process in the same order as
351 // they appear in the file, so for local items, we sort by node_id first
352 #[derive(PartialEq, Eq, PartialOrd, Ord)]
353 pub struct ItemSortKey<'tcx>(Option<usize>, SymbolName<'tcx>);
355 fn item_sort_key<'tcx>(tcx: TyCtxt<'tcx>, item: MonoItem<'tcx>) -> ItemSortKey<'tcx> {
358 MonoItem::Fn(ref instance) => {
360 // We only want to take HirIds of user-defined
361 // instances into account. The others don't matter for
362 // the codegen tests and can even make item order
364 InstanceDef::Item(def) => def.did.as_local().map(Idx::index),
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) => def_id.as_local().map(Idx::index),
376 MonoItem::GlobalAsm(item_id) => Some(item_id.owner_id.def_id.index()),
378 item.symbol_name(tcx),
382 let mut items: Vec<_> = self.items().iter().map(|(&i, &l)| (i, l)).collect();
383 items.sort_by_cached_key(|&(i, _)| item_sort_key(tcx, i));
387 pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode {
388 crate::dep_graph::make_compile_codegen_unit(tcx, self.name())
392 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for CodegenUnit<'tcx> {
393 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
397 // The size estimate is not relevant to the hash
400 is_code_coverage_dead_code_cgu,
403 name.hash_stable(hcx, hasher);
404 is_code_coverage_dead_code_cgu.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<'tcx> 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.unstable_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_stable_crate_id = tcx.sess.local_stable_crate_id();
496 tcx.crate_name(LOCAL_CRATE),
497 local_stable_crate_id.to_u64() as u32,
503 let stable_crate_id = tcx.sess.local_stable_crate_id();
506 tcx.crate_name(cnum),
507 stable_crate_id.to_u64() as u32,
512 write!(cgu_name, "{}", crate_prefix).unwrap();
514 // Add the components
515 for component in components {
516 write!(cgu_name, "-{}", component).unwrap();
519 if let Some(special_suffix) = special_suffix {
520 // We add a dot in here so it cannot clash with anything in a regular
522 write!(cgu_name, ".{}", special_suffix).unwrap();
525 Symbol::intern(&cgu_name)