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use crate::dep_graph::{DepNode, WorkProduct, WorkProductId};
use crate::ty::{GenericArgs, 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::{Hash128, HashStable, StableHasher};
use rustc_hir::def_id::{CrateNum, DefId, LOCAL_CRATE};
use rustc_hir::ItemId;
use rustc_index::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,
}
}
// Note: if you change how item size estimates work, you might need to
// change NON_INCR_MIN_CGU_SIZE as well.
pub fn size_estimate(&self, tcx: TyCtxt<'tcx>) -> usize {
match *self {
MonoItem::Fn(instance) => {
match instance.def {
// "Normal" functions size estimate: the number of
// statements, plus one for the terminator.
InstanceDef::Item(..) | InstanceDef::DropGlue(..) => {
let mir = tcx.instance_mir(instance.def);
mir.basic_blocks.iter().map(|bb| bb.statements.len() + 1).sum()
}
// Other compiler-generated shims size estimate: 1
_ => 1,
}
}
// Conservatively estimate the size of a static declaration or
// assembly item to be 1.
MonoItem::Static(_) | MonoItem::GlobalAsm(_) => 1,
}
}
pub fn is_generic_fn(&self, tcx: TyCtxt<'tcx>) -> bool {
match self {
MonoItem::Fn(instance) => {
instance.args.non_erasable_generics(tcx, instance.def_id()).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<Linkage> {
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, args) = match *self {
MonoItem::Fn(ref instance) => (instance.def_id(), instance.args),
MonoItem::Static(def_id) => (def_id, GenericArgs::empty()),
// global asm never has predicates
MonoItem::GlobalAsm(..) => return true,
};
!tcx.subst_and_check_impossible_predicates((def_id, &args))
}
pub fn local_span(&self, tcx: TyCtxt<'tcx>) -> Option<Span> {
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, GenericArgs::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<MonoItem<'tcx>, MonoItemData>,
size_estimate: usize,
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,
}
/// Auxiliary info about a `MonoItem`.
#[derive(Copy, Clone, PartialEq, Debug, HashStable)]
pub struct MonoItemData {
/// A cached copy of the result of `MonoItem::instantiation_mode`, where
/// `GloballyShared` maps to `false` and `LocalCopy` maps to `true`.
pub inlined: bool,
pub linkage: Linkage,
pub visibility: Visibility,
/// A cached copy of the result of `MonoItem::size_estimate`.
pub size_estimate: usize,
}
/// Specifies the linkage type for a `MonoItem`.
///
/// See <https://llvm.org/docs/LangRef.html#linkage-types> 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: 0,
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;
}
/// The order of these items is non-determinstic.
pub fn items(&self) -> &FxHashMap<MonoItem<'tcx>, MonoItemData> {
&self.items
}
/// The order of these items is non-determinstic.
pub fn items_mut(&mut self) -> &mut FxHashMap<MonoItem<'tcx>, MonoItemData> {
&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: Hash128 = hasher.finish();
let hash = hash.as_u128() & ((1u128 << 80) - 1);
base_n::encode(hash, base_n::CASE_INSENSITIVE)
}
pub fn compute_size_estimate(&mut self) {
// The size of a codegen unit as the sum of the sizes of the items
// within it.
self.size_estimate = self.items.values().map(|data| data.size_estimate).sum();
}
/// Should only be called if [`compute_size_estimate`] has previously been called.
///
/// [`compute_size_estimate`]: Self::compute_size_estimate
#[inline]
pub fn size_estimate(&self) -> usize {
// Items are never zero-sized, so if we have items the estimate must be
// non-zero, unless we forgot to call `compute_size_estimate` first.
assert!(self.items.is_empty() || self.size_estimate != 0);
self.size_estimate
}
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>, MonoItemData)> {
// 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<usize>, 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.as_local().map(Idx::index),
InstanceDef::VTableShim(..)
| InstanceDef::ReifyShim(..)
| InstanceDef::Intrinsic(..)
| InstanceDef::FnPtrShim(..)
| InstanceDef::Virtual(..)
| InstanceDef::ClosureOnceShim { .. }
| InstanceDef::DropGlue(..)
| InstanceDef::CloneShim(..)
| InstanceDef::ThreadLocalShim(..)
| InstanceDef::FnPtrAddrShim(..) => 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, &data)| (i, data)).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<StableHashingContext<'a>> 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<CrateNum, String>,
}
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
/// <crate-name>.<crate-disambiguator>[-in-<local-crate-id>](-<component>)*[.<special-suffix>]
/// <local-crate-id> = <local-crate-name>.<local-crate-disambiguator>
/// ```
///
/// The '.' before `<special-suffix>` 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<I, C, S>(
&mut self,
cnum: CrateNum,
components: I,
special_suffix: Option<S>,
) -> Symbol
where
I: IntoIterator<Item = C>,
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<I, C, S>(
&mut self,
cnum: CrateNum,
components: I,
special_suffix: Option<S>,
) -> Symbol
where
I: IntoIterator<Item = C>,
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.stable_crate_id(LOCAL_CRATE);
format!("-in-{}.{:08x}", tcx.crate_name(LOCAL_CRATE), local_stable_crate_id)
} else {
String::new()
};
let stable_crate_id = tcx.stable_crate_id(LOCAL_CRATE);
format!("{}.{:08x}{}", tcx.crate_name(cnum), stable_crate_id, 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)
}
}