1 use crate::dep_graph::{DepConstructor, DepNode, WorkProduct, WorkProductId};
2 use crate::hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
4 use crate::ich::{Fingerprint, NodeIdHashingMode, StableHashingContext};
5 use crate::session::config::OptLevel;
6 use crate::ty::print::obsolete::DefPathBasedNames;
7 use crate::ty::{subst::InternalSubsts, Instance, InstanceDef, SymbolName, TyCtxt};
8 use crate::util::nodemap::FxHashMap;
9 use rustc_data_structures::base_n;
10 use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
13 use syntax::attr::InlineAttr;
14 use syntax::source_map::Span;
15 use syntax::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 {
72 MonoItem::Fn(instance) => tcx.symbol_name(instance),
73 MonoItem::Static(def_id) => tcx.symbol_name(Instance::mono(tcx, def_id)),
74 MonoItem::GlobalAsm(hir_id) => {
75 let def_id = tcx.hir().local_def_id(hir_id);
76 SymbolName { name: Symbol::intern(&format!("global_asm_{:?}", def_id)) }
81 pub fn instantiation_mode(&self, tcx: TyCtxt<'tcx>) -> InstantiationMode {
82 let inline_in_all_cgus = tcx
87 .unwrap_or_else(|| tcx.sess.opts.optimize != OptLevel::No)
88 && !tcx.sess.opts.cg.link_dead_code;
91 MonoItem::Fn(ref instance) => {
92 let entry_def_id = tcx.entry_fn(LOCAL_CRATE).map(|(id, _)| id);
93 // If this function isn't inlined or otherwise has explicit
94 // linkage, then we'll be creating a globally shared version.
95 if self.explicit_linkage(tcx).is_some()
96 || !instance.def.requires_local(tcx)
97 || Some(instance.def_id()) == entry_def_id
99 return InstantiationMode::GloballyShared { may_conflict: false };
102 // At this point we don't have explicit linkage and we're an
103 // inlined function. If we're inlining into all CGUs then we'll
104 // be creating a local copy per CGU
105 if inline_in_all_cgus {
106 return InstantiationMode::LocalCopy;
109 // Finally, if this is `#[inline(always)]` we're sure to respect
110 // that with an inline copy per CGU, but otherwise we'll be
111 // creating one copy of this `#[inline]` function which may
112 // conflict with upstream crates as it could be an exported
114 match tcx.codegen_fn_attrs(instance.def_id()).inline {
115 InlineAttr::Always => InstantiationMode::LocalCopy,
116 _ => InstantiationMode::GloballyShared { may_conflict: true },
119 MonoItem::Static(..) | MonoItem::GlobalAsm(..) => {
120 InstantiationMode::GloballyShared { may_conflict: false }
125 pub fn explicit_linkage(&self, tcx: TyCtxt<'tcx>) -> Option<Linkage> {
126 let def_id = match *self {
127 MonoItem::Fn(ref instance) => instance.def_id(),
128 MonoItem::Static(def_id) => def_id,
129 MonoItem::GlobalAsm(..) => return None,
132 let codegen_fn_attrs = tcx.codegen_fn_attrs(def_id);
133 codegen_fn_attrs.linkage
136 /// Returns `true` if this instance is instantiable - whether it has no unsatisfied
139 /// In order to codegen an item, all of its predicates must hold, because
140 /// otherwise the item does not make sense. Type-checking ensures that
141 /// the predicates of every item that is *used by* a valid item *do*
142 /// hold, so we can rely on that.
144 /// However, we codegen collector roots (reachable items) and functions
145 /// in vtables when they are seen, even if they are not used, and so they
146 /// might not be instantiable. For example, a programmer can define this
149 /// pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone {
150 /// <&mut () as Clone>::clone(&s);
153 /// That function can't be codegened, because the method `<&mut () as Clone>::clone`
154 /// does not exist. Luckily for us, that function can't ever be used,
155 /// because that would require for `&'a mut (): Clone` to hold, so we
156 /// can just not emit any code, or even a linker reference for it.
158 /// Similarly, if a vtable method has such a signature, and therefore can't
159 /// be used, we can just not emit it and have a placeholder (a null pointer,
160 /// which will never be accessed) in its place.
161 pub fn is_instantiable(&self, tcx: TyCtxt<'tcx>) -> bool {
162 debug!("is_instantiable({:?})", self);
163 let (def_id, substs) = match *self {
164 MonoItem::Fn(ref instance) => (instance.def_id(), instance.substs),
165 MonoItem::Static(def_id) => (def_id, InternalSubsts::empty()),
166 // global asm never has predicates
167 MonoItem::GlobalAsm(..) => return true,
170 tcx.substitute_normalize_and_test_predicates((def_id, &substs))
173 pub fn to_string(&self, tcx: TyCtxt<'tcx>, debug: bool) -> String {
175 MonoItem::Fn(instance) => to_string_internal(tcx, "fn ", instance, debug),
176 MonoItem::Static(def_id) => {
177 let instance = Instance::new(def_id, tcx.intern_substs(&[]));
178 to_string_internal(tcx, "static ", instance, debug)
180 MonoItem::GlobalAsm(..) => "global_asm".to_string(),
183 fn to_string_internal<'tcx>(
186 instance: Instance<'tcx>,
189 let mut result = String::with_capacity(32);
190 result.push_str(prefix);
191 let printer = DefPathBasedNames::new(tcx, false, false);
192 printer.push_instance_as_string(instance, &mut result, debug);
197 pub fn local_span(&self, tcx: TyCtxt<'tcx>) -> Option<Span> {
199 MonoItem::Fn(Instance { def, .. }) => tcx.hir().as_local_hir_id(def.def_id()),
200 MonoItem::Static(def_id) => tcx.hir().as_local_hir_id(def_id),
201 MonoItem::GlobalAsm(hir_id) => Some(hir_id),
203 .map(|hir_id| tcx.hir().span(hir_id))
207 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for MonoItem<'tcx> {
208 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
209 ::std::mem::discriminant(self).hash_stable(hcx, hasher);
212 MonoItem::Fn(ref instance) => {
213 instance.hash_stable(hcx, hasher);
215 MonoItem::Static(def_id) => {
216 def_id.hash_stable(hcx, hasher);
218 MonoItem::GlobalAsm(node_id) => {
219 hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
220 node_id.hash_stable(hcx, hasher);
227 pub struct CodegenUnit<'tcx> {
228 /// A name for this CGU. Incremental compilation requires that
229 /// name be unique amongst **all** crates. Therefore, it should
230 /// contain something unique to this crate (e.g., a module path)
231 /// as well as the crate name and disambiguator.
233 items: FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)>,
234 size_estimate: Option<usize>,
237 #[derive(Copy, Clone, PartialEq, Debug, RustcEncodable, RustcDecodable, HashStable)]
252 #[derive(Copy, Clone, PartialEq, Debug, HashStable)]
253 pub enum Visibility {
259 impl<'tcx> CodegenUnit<'tcx> {
260 pub fn new(name: Symbol) -> CodegenUnit<'tcx> {
261 CodegenUnit { name: name, items: Default::default(), size_estimate: None }
264 pub fn name(&self) -> Symbol {
268 pub fn set_name(&mut self, name: Symbol) {
272 pub fn items(&self) -> &FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
276 pub fn items_mut(&mut self) -> &mut FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
280 pub fn mangle_name(human_readable_name: &str) -> String {
281 // We generate a 80 bit hash from the name. This should be enough to
282 // avoid collisions and is still reasonably short for filenames.
283 let mut hasher = StableHasher::new();
284 human_readable_name.hash(&mut hasher);
285 let hash: u128 = hasher.finish();
286 let hash = hash & ((1u128 << 80) - 1);
287 base_n::encode(hash, base_n::CASE_INSENSITIVE)
290 pub fn estimate_size(&mut self, tcx: TyCtxt<'tcx>) {
291 // Estimate the size of a codegen unit as (approximately) the number of MIR
292 // statements it corresponds to.
293 self.size_estimate = Some(self.items.keys().map(|mi| mi.size_estimate(tcx)).sum());
296 pub fn size_estimate(&self) -> usize {
297 // Should only be called if `estimate_size` has previously been called.
298 self.size_estimate.expect("estimate_size must be called before getting a size_estimate")
301 pub fn modify_size_estimate(&mut self, delta: usize) {
302 assert!(self.size_estimate.is_some());
303 if let Some(size_estimate) = self.size_estimate {
304 self.size_estimate = Some(size_estimate + delta);
308 pub fn contains_item(&self, item: &MonoItem<'tcx>) -> bool {
309 self.items().contains_key(item)
312 pub fn work_product_id(&self) -> WorkProductId {
313 WorkProductId::from_cgu_name(&self.name().as_str())
316 pub fn work_product(&self, tcx: TyCtxt<'_>) -> WorkProduct {
317 let work_product_id = self.work_product_id();
319 .previous_work_product(&work_product_id)
320 .unwrap_or_else(|| panic!("Could not find work-product for CGU `{}`", self.name()))
323 pub fn items_in_deterministic_order(
326 ) -> Vec<(MonoItem<'tcx>, (Linkage, Visibility))> {
327 // The codegen tests rely on items being process in the same order as
328 // they appear in the file, so for local items, we sort by node_id first
329 #[derive(PartialEq, Eq, PartialOrd, Ord)]
330 pub struct ItemSortKey(Option<HirId>, SymbolName);
332 fn item_sort_key<'tcx>(tcx: TyCtxt<'tcx>, item: MonoItem<'tcx>) -> ItemSortKey {
335 MonoItem::Fn(ref instance) => {
337 // We only want to take HirIds of user-defined
338 // instances into account. The others don't matter for
339 // the codegen tests and can even make item order
341 InstanceDef::Item(def_id) => tcx.hir().as_local_hir_id(def_id),
342 InstanceDef::VtableShim(..)
343 | InstanceDef::ReifyShim(..)
344 | InstanceDef::Intrinsic(..)
345 | InstanceDef::FnPtrShim(..)
346 | InstanceDef::Virtual(..)
347 | InstanceDef::ClosureOnceShim { .. }
348 | InstanceDef::DropGlue(..)
349 | InstanceDef::CloneShim(..) => None,
352 MonoItem::Static(def_id) => tcx.hir().as_local_hir_id(def_id),
353 MonoItem::GlobalAsm(hir_id) => Some(hir_id),
355 item.symbol_name(tcx),
359 let mut items: Vec<_> = self.items().iter().map(|(&i, &l)| (i, l)).collect();
360 items.sort_by_cached_key(|&(i, _)| item_sort_key(tcx, i));
364 pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode {
365 DepNode::new(tcx, DepConstructor::CompileCodegenUnit(self.name().clone()))
369 impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for CodegenUnit<'tcx> {
370 fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
374 // The size estimate is not relevant to the hash
378 name.hash_stable(hcx, hasher);
380 let mut items: Vec<(Fingerprint, _)> = items
382 .map(|(mono_item, &attrs)| {
383 let mut hasher = StableHasher::new();
384 mono_item.hash_stable(hcx, &mut hasher);
385 let mono_item_fingerprint = hasher.finish();
386 (mono_item_fingerprint, attrs)
390 items.sort_unstable_by_key(|i| i.0);
391 items.hash_stable(hcx, hasher);
395 pub struct CodegenUnitNameBuilder<'tcx> {
397 cache: FxHashMap<CrateNum, String>,
400 impl CodegenUnitNameBuilder<'tcx> {
401 pub fn new(tcx: TyCtxt<'tcx>) -> Self {
402 CodegenUnitNameBuilder { tcx, cache: Default::default() }
405 /// CGU names should fulfill the following requirements:
406 /// - They should be able to act as a file name on any kind of file system
407 /// - They should not collide with other CGU names, even for different versions
408 /// of the same crate.
410 /// Consequently, we don't use special characters except for '.' and '-' and we
411 /// prefix each name with the crate-name and crate-disambiguator.
413 /// This function will build CGU names of the form:
416 /// <crate-name>.<crate-disambiguator>[-in-<local-crate-id>](-<component>)*[.<special-suffix>]
417 /// <local-crate-id> = <local-crate-name>.<local-crate-disambiguator>
420 /// The '.' before `<special-suffix>` makes sure that names with a special
421 /// suffix can never collide with a name built out of regular Rust
422 /// identifiers (e.g., module paths).
423 pub fn build_cgu_name<I, C, S>(
427 special_suffix: Option<S>,
430 I: IntoIterator<Item = C>,
434 let cgu_name = self.build_cgu_name_no_mangle(cnum, components, special_suffix);
436 if self.tcx.sess.opts.debugging_opts.human_readable_cgu_names {
439 let cgu_name = &cgu_name.as_str();
440 Symbol::intern(&CodegenUnit::mangle_name(cgu_name))
444 /// Same as `CodegenUnit::build_cgu_name()` but will never mangle the
446 pub fn build_cgu_name_no_mangle<I, C, S>(
450 special_suffix: Option<S>,
453 I: IntoIterator<Item = C>,
459 let mut cgu_name = String::with_capacity(64);
461 // Start out with the crate name and disambiguator
463 let crate_prefix = self.cache.entry(cnum).or_insert_with(|| {
464 // Whenever the cnum is not LOCAL_CRATE we also mix in the
465 // local crate's ID. Otherwise there can be collisions between CGUs
466 // instantiating stuff for upstream crates.
467 let local_crate_id = if cnum != LOCAL_CRATE {
468 let local_crate_disambiguator = format!("{}", tcx.crate_disambiguator(LOCAL_CRATE));
469 format!("-in-{}.{}", tcx.crate_name(LOCAL_CRATE), &local_crate_disambiguator[0..8])
474 let crate_disambiguator = tcx.crate_disambiguator(cnum).to_string();
475 // Using a shortened disambiguator of about 40 bits
476 format!("{}.{}{}", tcx.crate_name(cnum), &crate_disambiguator[0..8], local_crate_id)
479 write!(cgu_name, "{}", crate_prefix).unwrap();
481 // Add the components
482 for component in components {
483 write!(cgu_name, "-{}", component).unwrap();
486 if let Some(special_suffix) = special_suffix {
487 // We add a dot in here so it cannot clash with anything in a regular
489 write!(cgu_name, ".{}", special_suffix).unwrap();
492 Symbol::intern(&cgu_name[..])