use crate::dep_graph::{DepNode, WorkProduct, WorkProductId}; use crate::ty::{subst::InternalSubsts, Instance, InstanceDef, SymbolName, TyCtxt}; use rustc_attr::InlineAttr; use rustc_data_structures::base_n; use rustc_data_structures::fingerprint::Fingerprint; use rustc_data_structures::fx::FxHashMap; use rustc_data_structures::stable_hasher::{HashStable, StableHasher}; use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE}; use rustc_hir::ItemId; use rustc_index::vec::Idx; use rustc_query_system::ich::StableHashingContext; use rustc_session::config::OptLevel; use rustc_span::source_map::Span; use rustc_span::symbol::Symbol; use std::fmt; use std::hash::Hash; /// Describes how a monomorphization will be instantiated in object files. #[derive(PartialEq)] pub enum InstantiationMode { /// There will be exactly one instance of the given MonoItem. It will have /// external linkage so that it can be linked to from other codegen units. GloballyShared { /// In some compilation scenarios we may decide to take functions that /// are typically `LocalCopy` and instead move them to `GloballyShared` /// to avoid codegenning them a bunch of times. In this situation, /// however, our local copy may conflict with other crates also /// inlining the same function. /// /// This flag indicates that this situation is occurring, and informs /// symbol name calculation that some extra mangling is needed to /// avoid conflicts. Note that this may eventually go away entirely if /// ThinLTO enables us to *always* have a globally shared instance of a /// function within one crate's compilation. may_conflict: bool, }, /// Each codegen unit containing a reference to the given MonoItem will /// have its own private copy of the function (with internal linkage). LocalCopy, } #[derive(PartialEq, Eq, Clone, Copy, Debug, Hash, HashStable)] pub enum MonoItem<'tcx> { Fn(Instance<'tcx>), Static(DefId), GlobalAsm(ItemId), } impl<'tcx> MonoItem<'tcx> { /// Returns `true` if the mono item is user-defined (i.e. not compiler-generated, like shims). pub fn is_user_defined(&self) -> bool { match *self { MonoItem::Fn(instance) => matches!(instance.def, InstanceDef::Item(..)), MonoItem::Static(..) | MonoItem::GlobalAsm(..) => true, } } pub fn size_estimate(&self, tcx: TyCtxt<'tcx>) -> usize { match *self { MonoItem::Fn(instance) => { // Estimate the size of a function based on how many statements // it contains. tcx.instance_def_size_estimate(instance.def) } // Conservatively estimate the size of a static declaration // or assembly to be 1. MonoItem::Static(_) | MonoItem::GlobalAsm(_) => 1, } } pub fn is_generic_fn(&self) -> bool { match *self { MonoItem::Fn(ref instance) => instance.substs.non_erasable_generics().next().is_some(), MonoItem::Static(..) | MonoItem::GlobalAsm(..) => false, } } pub fn symbol_name(&self, tcx: TyCtxt<'tcx>) -> SymbolName<'tcx> { match *self { MonoItem::Fn(instance) => tcx.symbol_name(instance), MonoItem::Static(def_id) => tcx.symbol_name(Instance::mono(tcx, def_id)), MonoItem::GlobalAsm(item_id) => { SymbolName::new(tcx, &format!("global_asm_{:?}", item_id.owner_id)) } } } pub fn instantiation_mode(&self, tcx: TyCtxt<'tcx>) -> InstantiationMode { let generate_cgu_internal_copies = tcx .sess .opts .unstable_opts .inline_in_all_cgus .unwrap_or_else(|| tcx.sess.opts.optimize != OptLevel::No) && !tcx.sess.link_dead_code(); match *self { MonoItem::Fn(ref instance) => { let entry_def_id = tcx.entry_fn(()).map(|(id, _)| id); // If this function isn't inlined or otherwise has an extern // indicator, then we'll be creating a globally shared version. if tcx.codegen_fn_attrs(instance.def_id()).contains_extern_indicator() || !instance.def.generates_cgu_internal_copy(tcx) || Some(instance.def_id()) == entry_def_id { return InstantiationMode::GloballyShared { may_conflict: false }; } // At this point we don't have explicit linkage and we're an // inlined function. If we're inlining into all CGUs then we'll // be creating a local copy per CGU. if generate_cgu_internal_copies { return InstantiationMode::LocalCopy; } // Finally, if this is `#[inline(always)]` we're sure to respect // that with an inline copy per CGU, but otherwise we'll be // creating one copy of this `#[inline]` function which may // conflict with upstream crates as it could be an exported // symbol. match tcx.codegen_fn_attrs(instance.def_id()).inline { InlineAttr::Always => InstantiationMode::LocalCopy, _ => InstantiationMode::GloballyShared { may_conflict: true }, } } MonoItem::Static(..) | MonoItem::GlobalAsm(..) => { InstantiationMode::GloballyShared { may_conflict: false } } } } pub fn explicit_linkage(&self, tcx: TyCtxt<'tcx>) -> Option { let def_id = match *self { MonoItem::Fn(ref instance) => instance.def_id(), MonoItem::Static(def_id) => def_id, MonoItem::GlobalAsm(..) => return None, }; let codegen_fn_attrs = tcx.codegen_fn_attrs(def_id); codegen_fn_attrs.linkage } /// Returns `true` if this instance is instantiable - whether it has no unsatisfied /// predicates. /// /// In order to codegen an item, all of its predicates must hold, because /// otherwise the item does not make sense. Type-checking ensures that /// the predicates of every item that is *used by* a valid item *do* /// hold, so we can rely on that. /// /// However, we codegen collector roots (reachable items) and functions /// in vtables when they are seen, even if they are not used, and so they /// might not be instantiable. For example, a programmer can define this /// public function: /// /// pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone { /// <&mut () as Clone>::clone(&s); /// } /// /// That function can't be codegened, because the method `<&mut () as Clone>::clone` /// does not exist. Luckily for us, that function can't ever be used, /// because that would require for `&'a mut (): Clone` to hold, so we /// can just not emit any code, or even a linker reference for it. /// /// Similarly, if a vtable method has such a signature, and therefore can't /// be used, we can just not emit it and have a placeholder (a null pointer, /// which will never be accessed) in its place. pub fn is_instantiable(&self, tcx: TyCtxt<'tcx>) -> bool { debug!("is_instantiable({:?})", self); let (def_id, substs) = match *self { MonoItem::Fn(ref instance) => (instance.def_id(), instance.substs), MonoItem::Static(def_id) => (def_id, InternalSubsts::empty()), // global asm never has predicates MonoItem::GlobalAsm(..) => return true, }; !tcx.subst_and_check_impossible_predicates((def_id, &substs)) } pub fn local_span(&self, tcx: TyCtxt<'tcx>) -> Option { match *self { MonoItem::Fn(Instance { def, .. }) => def.def_id().as_local(), MonoItem::Static(def_id) => def_id.as_local(), MonoItem::GlobalAsm(item_id) => Some(item_id.owner_id.def_id), } .map(|def_id| tcx.def_span(def_id)) } // Only used by rustc_codegen_cranelift pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode { crate::dep_graph::make_compile_mono_item(tcx, self) } /// Returns the item's `CrateNum` pub fn krate(&self) -> CrateNum { match self { MonoItem::Fn(ref instance) => instance.def_id().krate, MonoItem::Static(def_id) => def_id.krate, MonoItem::GlobalAsm(..) => LOCAL_CRATE, } } /// Returns the item's `DefId` pub fn def_id(&self) -> DefId { match *self { MonoItem::Fn(Instance { def, .. }) => def.def_id(), MonoItem::Static(def_id) => def_id, MonoItem::GlobalAsm(item_id) => item_id.owner_id.to_def_id(), } } } impl<'tcx> fmt::Display for MonoItem<'tcx> { fn fmt(&self, f: &mut fmt::Formatter<'_>) -> fmt::Result { match *self { MonoItem::Fn(instance) => write!(f, "fn {}", instance), MonoItem::Static(def_id) => { write!(f, "static {}", Instance::new(def_id, InternalSubsts::empty())) } MonoItem::GlobalAsm(..) => write!(f, "global_asm"), } } } #[derive(Debug)] pub struct CodegenUnit<'tcx> { /// A name for this CGU. Incremental compilation requires that /// name be unique amongst **all** crates. Therefore, it should /// contain something unique to this crate (e.g., a module path) /// as well as the crate name and disambiguator. name: Symbol, items: FxHashMap, (Linkage, Visibility)>, size_estimate: Option, primary: bool, /// True if this is CGU is used to hold code coverage information for dead code, /// false otherwise. is_code_coverage_dead_code_cgu: bool, } /// Specifies the linkage type for a `MonoItem`. /// /// See for more details about these variants. #[derive(Copy, Clone, PartialEq, Debug, TyEncodable, TyDecodable, HashStable)] pub enum Linkage { External, AvailableExternally, LinkOnceAny, LinkOnceODR, WeakAny, WeakODR, Appending, Internal, Private, ExternalWeak, Common, } #[derive(Copy, Clone, PartialEq, Debug, HashStable)] pub enum Visibility { Default, Hidden, Protected, } impl<'tcx> CodegenUnit<'tcx> { #[inline] pub fn new(name: Symbol) -> CodegenUnit<'tcx> { CodegenUnit { name, items: Default::default(), size_estimate: None, primary: false, is_code_coverage_dead_code_cgu: false, } } pub fn name(&self) -> Symbol { self.name } pub fn set_name(&mut self, name: Symbol) { self.name = name; } pub fn is_primary(&self) -> bool { self.primary } pub fn make_primary(&mut self) { self.primary = true; } pub fn items(&self) -> &FxHashMap, (Linkage, Visibility)> { &self.items } pub fn items_mut(&mut self) -> &mut FxHashMap, (Linkage, Visibility)> { &mut self.items } pub fn is_code_coverage_dead_code_cgu(&self) -> bool { self.is_code_coverage_dead_code_cgu } /// Marks this CGU as the one used to contain code coverage information for dead code. pub fn make_code_coverage_dead_code_cgu(&mut self) { self.is_code_coverage_dead_code_cgu = true; } pub fn mangle_name(human_readable_name: &str) -> String { // We generate a 80 bit hash from the name. This should be enough to // avoid collisions and is still reasonably short for filenames. let mut hasher = StableHasher::new(); human_readable_name.hash(&mut hasher); let hash: u128 = hasher.finish(); let hash = hash & ((1u128 << 80) - 1); base_n::encode(hash, base_n::CASE_INSENSITIVE) } pub fn create_size_estimate(&mut self, tcx: TyCtxt<'tcx>) { // Estimate the size of a codegen unit as (approximately) the number of MIR // statements it corresponds to. self.size_estimate = Some(self.items.keys().map(|mi| mi.size_estimate(tcx)).sum()); } #[inline] /// Should only be called if [`create_size_estimate`] has previously been called. /// /// [`create_size_estimate`]: Self::create_size_estimate pub fn size_estimate(&self) -> usize { self.size_estimate .expect("create_size_estimate must be called before getting a size_estimate") } pub fn modify_size_estimate(&mut self, delta: usize) { assert!(self.size_estimate.is_some()); if let Some(size_estimate) = self.size_estimate { self.size_estimate = Some(size_estimate + delta); } } pub fn contains_item(&self, item: &MonoItem<'tcx>) -> bool { self.items().contains_key(item) } pub fn work_product_id(&self) -> WorkProductId { WorkProductId::from_cgu_name(self.name().as_str()) } pub fn previous_work_product(&self, tcx: TyCtxt<'_>) -> WorkProduct { let work_product_id = self.work_product_id(); tcx.dep_graph .previous_work_product(&work_product_id) .unwrap_or_else(|| panic!("Could not find work-product for CGU `{}`", self.name())) } pub fn items_in_deterministic_order( &self, tcx: TyCtxt<'tcx>, ) -> Vec<(MonoItem<'tcx>, (Linkage, Visibility))> { // The codegen tests rely on items being process in the same order as // they appear in the file, so for local items, we sort by node_id first #[derive(PartialEq, Eq, PartialOrd, Ord)] pub struct ItemSortKey<'tcx>(Option, SymbolName<'tcx>); fn item_sort_key<'tcx>(tcx: TyCtxt<'tcx>, item: MonoItem<'tcx>) -> ItemSortKey<'tcx> { ItemSortKey( match item { MonoItem::Fn(ref instance) => { match instance.def { // We only want to take HirIds of user-defined // instances into account. The others don't matter for // the codegen tests and can even make item order // unstable. InstanceDef::Item(def) => def.did.as_local().map(Idx::index), InstanceDef::VTableShim(..) | InstanceDef::ReifyShim(..) | InstanceDef::Intrinsic(..) | InstanceDef::FnPtrShim(..) | InstanceDef::Virtual(..) | InstanceDef::ClosureOnceShim { .. } | InstanceDef::DropGlue(..) | InstanceDef::CloneShim(..) => None, } } MonoItem::Static(def_id) => def_id.as_local().map(Idx::index), MonoItem::GlobalAsm(item_id) => Some(item_id.owner_id.def_id.index()), }, item.symbol_name(tcx), ) } let mut items: Vec<_> = self.items().iter().map(|(&i, &l)| (i, l)).collect(); items.sort_by_cached_key(|&(i, _)| item_sort_key(tcx, i)); items } pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode { crate::dep_graph::make_compile_codegen_unit(tcx, self.name()) } } impl<'a, 'tcx> HashStable> for CodegenUnit<'tcx> { fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) { let CodegenUnit { ref items, name, // The size estimate is not relevant to the hash size_estimate: _, primary: _, is_code_coverage_dead_code_cgu, } = *self; name.hash_stable(hcx, hasher); is_code_coverage_dead_code_cgu.hash_stable(hcx, hasher); let mut items: Vec<(Fingerprint, _)> = items .iter() .map(|(mono_item, &attrs)| { let mut hasher = StableHasher::new(); mono_item.hash_stable(hcx, &mut hasher); let mono_item_fingerprint = hasher.finish(); (mono_item_fingerprint, attrs) }) .collect(); items.sort_unstable_by_key(|i| i.0); items.hash_stable(hcx, hasher); } } pub struct CodegenUnitNameBuilder<'tcx> { tcx: TyCtxt<'tcx>, cache: FxHashMap, } impl<'tcx> CodegenUnitNameBuilder<'tcx> { pub fn new(tcx: TyCtxt<'tcx>) -> Self { CodegenUnitNameBuilder { tcx, cache: Default::default() } } /// CGU names should fulfill the following requirements: /// - They should be able to act as a file name on any kind of file system /// - They should not collide with other CGU names, even for different versions /// of the same crate. /// /// Consequently, we don't use special characters except for '.' and '-' and we /// prefix each name with the crate-name and crate-disambiguator. /// /// This function will build CGU names of the form: /// /// ```text /// .[-in-](-)*[.] /// = . /// ``` /// /// The '.' before `` makes sure that names with a special /// suffix can never collide with a name built out of regular Rust /// identifiers (e.g., module paths). pub fn build_cgu_name( &mut self, cnum: CrateNum, components: I, special_suffix: Option, ) -> Symbol where I: IntoIterator, C: fmt::Display, S: fmt::Display, { let cgu_name = self.build_cgu_name_no_mangle(cnum, components, special_suffix); if self.tcx.sess.opts.unstable_opts.human_readable_cgu_names { cgu_name } else { Symbol::intern(&CodegenUnit::mangle_name(cgu_name.as_str())) } } /// Same as `CodegenUnit::build_cgu_name()` but will never mangle the /// resulting name. pub fn build_cgu_name_no_mangle( &mut self, cnum: CrateNum, components: I, special_suffix: Option, ) -> Symbol where I: IntoIterator, C: fmt::Display, S: fmt::Display, { use std::fmt::Write; let mut cgu_name = String::with_capacity(64); // Start out with the crate name and disambiguator let tcx = self.tcx; let crate_prefix = self.cache.entry(cnum).or_insert_with(|| { // Whenever the cnum is not LOCAL_CRATE we also mix in the // local crate's ID. Otherwise there can be collisions between CGUs // instantiating stuff for upstream crates. let local_crate_id = if cnum != LOCAL_CRATE { let local_stable_crate_id = tcx.sess.local_stable_crate_id(); format!( "-in-{}.{:08x}", tcx.crate_name(LOCAL_CRATE), local_stable_crate_id.to_u64() as u32, ) } else { String::new() }; let stable_crate_id = tcx.sess.local_stable_crate_id(); format!( "{}.{:08x}{}", tcx.crate_name(cnum), stable_crate_id.to_u64() as u32, local_crate_id, ) }); write!(cgu_name, "{}", crate_prefix).unwrap(); // Add the components for component in components { write!(cgu_name, "-{}", component).unwrap(); } if let Some(special_suffix) = special_suffix { // We add a dot in here so it cannot clash with anything in a regular // Rust identifier write!(cgu_name, ".{}", special_suffix).unwrap(); } Symbol::intern(&cgu_name) } }