506 lines
19 KiB
Rust
506 lines
19 KiB
Rust
use crate::dep_graph::{DepConstructor, DepNode, WorkProduct, WorkProductId};
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use crate::ich::{NodeIdHashingMode, StableHashingContext};
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use crate::ty::print::obsolete::DefPathBasedNames;
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use crate::ty::{subst::InternalSubsts, Instance, InstanceDef, SymbolName, TyCtxt};
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use rustc_attr::InlineAttr;
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use rustc_data_structures::base_n;
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use rustc_data_structures::fingerprint::Fingerprint;
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use rustc_data_structures::fx::FxHashMap;
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use rustc_data_structures::stable_hasher::{HashStable, StableHasher};
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use rustc_hir::def_id::{CrateNum, DefId, LocalDefId, LOCAL_CRATE};
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use rustc_hir::HirId;
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use rustc_session::config::OptLevel;
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use rustc_span::source_map::Span;
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use rustc_span::symbol::Symbol;
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use std::fmt;
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use std::hash::Hash;
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/// Describes how a monomorphization will be instantiated in object files.
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#[derive(PartialEq)]
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pub enum InstantiationMode {
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/// There will be exactly one instance of the given MonoItem. It will have
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/// external linkage so that it can be linked to from other codegen units.
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GloballyShared {
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/// In some compilation scenarios we may decide to take functions that
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/// are typically `LocalCopy` and instead move them to `GloballyShared`
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/// to avoid codegenning them a bunch of times. In this situation,
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/// however, our local copy may conflict with other crates also
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/// inlining the same function.
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///
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/// This flag indicates that this situation is occurring, and informs
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/// symbol name calculation that some extra mangling is needed to
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/// avoid conflicts. Note that this may eventually go away entirely if
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/// ThinLTO enables us to *always* have a globally shared instance of a
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/// function within one crate's compilation.
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may_conflict: bool,
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},
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/// Each codegen unit containing a reference to the given MonoItem will
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/// have its own private copy of the function (with internal linkage).
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LocalCopy,
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}
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#[derive(PartialEq, Eq, Clone, Copy, Debug, Hash)]
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pub enum MonoItem<'tcx> {
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Fn(Instance<'tcx>),
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Static(DefId),
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GlobalAsm(HirId),
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}
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impl<'tcx> MonoItem<'tcx> {
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pub fn size_estimate(&self, tcx: TyCtxt<'tcx>) -> usize {
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match *self {
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MonoItem::Fn(instance) => {
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// Estimate the size of a function based on how many statements
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// it contains.
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tcx.instance_def_size_estimate(instance.def)
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}
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// Conservatively estimate the size of a static declaration
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// or assembly to be 1.
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MonoItem::Static(_) | MonoItem::GlobalAsm(_) => 1,
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}
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}
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pub fn is_generic_fn(&self) -> bool {
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match *self {
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MonoItem::Fn(ref instance) => instance.substs.non_erasable_generics().next().is_some(),
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MonoItem::Static(..) | MonoItem::GlobalAsm(..) => false,
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}
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}
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pub fn symbol_name(&self, tcx: TyCtxt<'tcx>) -> SymbolName<'tcx> {
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match *self {
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MonoItem::Fn(instance) => tcx.symbol_name(instance),
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MonoItem::Static(def_id) => tcx.symbol_name(Instance::mono(tcx, def_id)),
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MonoItem::GlobalAsm(hir_id) => {
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let def_id = tcx.hir().local_def_id(hir_id);
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SymbolName::new(tcx, &format!("global_asm_{:?}", def_id))
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}
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}
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}
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pub fn instantiation_mode(&self, tcx: TyCtxt<'tcx>) -> InstantiationMode {
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let generate_cgu_internal_copies = tcx
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.sess
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.opts
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.debugging_opts
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.inline_in_all_cgus
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.unwrap_or_else(|| tcx.sess.opts.optimize != OptLevel::No)
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&& tcx.sess.opts.cg.link_dead_code != Some(true);
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match *self {
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MonoItem::Fn(ref instance) => {
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let entry_def_id = tcx.entry_fn(LOCAL_CRATE).map(|(id, _)| id);
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// If this function isn't inlined or otherwise has an extern
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// indicator, then we'll be creating a globally shared version.
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if tcx.codegen_fn_attrs(instance.def_id()).contains_extern_indicator()
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|| !instance.def.generates_cgu_internal_copy(tcx)
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|| Some(instance.def_id()) == entry_def_id.map(LocalDefId::to_def_id)
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{
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return InstantiationMode::GloballyShared { may_conflict: false };
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}
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// At this point we don't have explicit linkage and we're an
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// inlined function. If we're inlining into all CGUs then we'll
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// be creating a local copy per CGU.
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if generate_cgu_internal_copies {
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return InstantiationMode::LocalCopy;
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}
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// Finally, if this is `#[inline(always)]` we're sure to respect
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// that with an inline copy per CGU, but otherwise we'll be
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// creating one copy of this `#[inline]` function which may
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// conflict with upstream crates as it could be an exported
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// symbol.
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match tcx.codegen_fn_attrs(instance.def_id()).inline {
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InlineAttr::Always => InstantiationMode::LocalCopy,
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_ => InstantiationMode::GloballyShared { may_conflict: true },
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}
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}
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MonoItem::Static(..) | MonoItem::GlobalAsm(..) => {
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InstantiationMode::GloballyShared { may_conflict: false }
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}
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}
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}
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pub fn explicit_linkage(&self, tcx: TyCtxt<'tcx>) -> Option<Linkage> {
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let def_id = match *self {
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MonoItem::Fn(ref instance) => instance.def_id(),
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MonoItem::Static(def_id) => def_id,
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MonoItem::GlobalAsm(..) => return None,
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};
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let codegen_fn_attrs = tcx.codegen_fn_attrs(def_id);
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codegen_fn_attrs.linkage
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}
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/// Returns `true` if this instance is instantiable - whether it has no unsatisfied
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/// predicates.
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///
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/// In order to codegen an item, all of its predicates must hold, because
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/// otherwise the item does not make sense. Type-checking ensures that
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/// the predicates of every item that is *used by* a valid item *do*
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/// hold, so we can rely on that.
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///
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/// However, we codegen collector roots (reachable items) and functions
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/// in vtables when they are seen, even if they are not used, and so they
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/// might not be instantiable. For example, a programmer can define this
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/// public function:
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///
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/// pub fn foo<'a>(s: &'a mut ()) where &'a mut (): Clone {
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/// <&mut () as Clone>::clone(&s);
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/// }
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///
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/// That function can't be codegened, because the method `<&mut () as Clone>::clone`
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/// does not exist. Luckily for us, that function can't ever be used,
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/// because that would require for `&'a mut (): Clone` to hold, so we
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/// can just not emit any code, or even a linker reference for it.
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///
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/// Similarly, if a vtable method has such a signature, and therefore can't
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/// be used, we can just not emit it and have a placeholder (a null pointer,
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/// which will never be accessed) in its place.
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pub fn is_instantiable(&self, tcx: TyCtxt<'tcx>) -> bool {
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debug!("is_instantiable({:?})", self);
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let (def_id, substs) = match *self {
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MonoItem::Fn(ref instance) => (instance.def_id(), instance.substs),
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MonoItem::Static(def_id) => (def_id, InternalSubsts::empty()),
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// global asm never has predicates
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MonoItem::GlobalAsm(..) => return true,
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};
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!tcx.subst_and_check_impossible_predicates((def_id, &substs))
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}
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pub fn to_string(&self, tcx: TyCtxt<'tcx>, debug: bool) -> String {
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return match *self {
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MonoItem::Fn(instance) => to_string_internal(tcx, "fn ", instance, debug),
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MonoItem::Static(def_id) => {
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let instance = Instance::new(def_id, tcx.intern_substs(&[]));
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to_string_internal(tcx, "static ", instance, debug)
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}
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MonoItem::GlobalAsm(..) => "global_asm".to_string(),
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};
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fn to_string_internal<'tcx>(
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tcx: TyCtxt<'tcx>,
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prefix: &str,
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instance: Instance<'tcx>,
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debug: bool,
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) -> String {
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let mut result = String::with_capacity(32);
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result.push_str(prefix);
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let printer = DefPathBasedNames::new(tcx, false, false);
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printer.push_instance_as_string(instance, &mut result, debug);
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result
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}
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}
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pub fn local_span(&self, tcx: TyCtxt<'tcx>) -> Option<Span> {
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match *self {
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MonoItem::Fn(Instance { def, .. }) => {
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def.def_id().as_local().map(|def_id| tcx.hir().as_local_hir_id(def_id))
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}
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MonoItem::Static(def_id) => {
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def_id.as_local().map(|def_id| tcx.hir().as_local_hir_id(def_id))
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}
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MonoItem::GlobalAsm(hir_id) => Some(hir_id),
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}
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.map(|hir_id| tcx.hir().span(hir_id))
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}
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}
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impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for MonoItem<'tcx> {
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fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
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::std::mem::discriminant(self).hash_stable(hcx, hasher);
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match *self {
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MonoItem::Fn(ref instance) => {
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instance.hash_stable(hcx, hasher);
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}
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MonoItem::Static(def_id) => {
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def_id.hash_stable(hcx, hasher);
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}
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MonoItem::GlobalAsm(node_id) => {
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hcx.with_node_id_hashing_mode(NodeIdHashingMode::HashDefPath, |hcx| {
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node_id.hash_stable(hcx, hasher);
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})
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}
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}
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}
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}
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pub struct CodegenUnit<'tcx> {
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/// A name for this CGU. Incremental compilation requires that
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/// name be unique amongst **all** crates. Therefore, it should
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/// contain something unique to this crate (e.g., a module path)
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/// as well as the crate name and disambiguator.
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name: Symbol,
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items: FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)>,
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size_estimate: Option<usize>,
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}
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/// Specifies the linkage type for a `MonoItem`.
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///
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/// See https://llvm.org/docs/LangRef.html#linkage-types for more details about these variants.
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#[derive(Copy, Clone, PartialEq, Debug, Encodable, Decodable, HashStable)]
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pub enum Linkage {
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External,
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AvailableExternally,
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LinkOnceAny,
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LinkOnceODR,
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WeakAny,
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WeakODR,
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Appending,
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Internal,
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Private,
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ExternalWeak,
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Common,
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}
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#[derive(Copy, Clone, PartialEq, Debug, HashStable)]
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pub enum Visibility {
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Default,
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Hidden,
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Protected,
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}
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impl<'tcx> CodegenUnit<'tcx> {
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pub fn new(name: Symbol) -> CodegenUnit<'tcx> {
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CodegenUnit { name, items: Default::default(), size_estimate: None }
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}
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pub fn name(&self) -> Symbol {
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self.name
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}
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pub fn set_name(&mut self, name: Symbol) {
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self.name = name;
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}
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pub fn items(&self) -> &FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
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&self.items
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}
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pub fn items_mut(&mut self) -> &mut FxHashMap<MonoItem<'tcx>, (Linkage, Visibility)> {
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&mut self.items
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}
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pub fn mangle_name(human_readable_name: &str) -> String {
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// We generate a 80 bit hash from the name. This should be enough to
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// avoid collisions and is still reasonably short for filenames.
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let mut hasher = StableHasher::new();
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human_readable_name.hash(&mut hasher);
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let hash: u128 = hasher.finish();
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let hash = hash & ((1u128 << 80) - 1);
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base_n::encode(hash, base_n::CASE_INSENSITIVE)
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}
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pub fn estimate_size(&mut self, tcx: TyCtxt<'tcx>) {
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// Estimate the size of a codegen unit as (approximately) the number of MIR
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// statements it corresponds to.
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self.size_estimate = Some(self.items.keys().map(|mi| mi.size_estimate(tcx)).sum());
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}
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pub fn size_estimate(&self) -> usize {
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// Should only be called if `estimate_size` has previously been called.
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self.size_estimate.expect("estimate_size must be called before getting a size_estimate")
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}
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pub fn modify_size_estimate(&mut self, delta: usize) {
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assert!(self.size_estimate.is_some());
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if let Some(size_estimate) = self.size_estimate {
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self.size_estimate = Some(size_estimate + delta);
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}
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}
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pub fn contains_item(&self, item: &MonoItem<'tcx>) -> bool {
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self.items().contains_key(item)
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}
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pub fn work_product_id(&self) -> WorkProductId {
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WorkProductId::from_cgu_name(&self.name().as_str())
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}
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pub fn work_product(&self, tcx: TyCtxt<'_>) -> WorkProduct {
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let work_product_id = self.work_product_id();
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tcx.dep_graph
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.previous_work_product(&work_product_id)
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.unwrap_or_else(|| panic!("Could not find work-product for CGU `{}`", self.name()))
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}
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pub fn items_in_deterministic_order(
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&self,
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tcx: TyCtxt<'tcx>,
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) -> Vec<(MonoItem<'tcx>, (Linkage, Visibility))> {
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// The codegen tests rely on items being process in the same order as
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// they appear in the file, so for local items, we sort by node_id first
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#[derive(PartialEq, Eq, PartialOrd, Ord)]
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pub struct ItemSortKey<'tcx>(Option<HirId>, SymbolName<'tcx>);
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fn item_sort_key<'tcx>(tcx: TyCtxt<'tcx>, item: MonoItem<'tcx>) -> ItemSortKey<'tcx> {
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ItemSortKey(
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match item {
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MonoItem::Fn(ref instance) => {
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match instance.def {
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// We only want to take HirIds of user-defined
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// instances into account. The others don't matter for
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// the codegen tests and can even make item order
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// unstable.
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InstanceDef::Item(def) => {
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def.did.as_local().map(|def_id| tcx.hir().as_local_hir_id(def_id))
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}
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InstanceDef::VtableShim(..)
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| InstanceDef::ReifyShim(..)
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| InstanceDef::Intrinsic(..)
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| InstanceDef::FnPtrShim(..)
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| InstanceDef::Virtual(..)
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| InstanceDef::ClosureOnceShim { .. }
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| InstanceDef::DropGlue(..)
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| InstanceDef::CloneShim(..) => None,
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}
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}
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MonoItem::Static(def_id) => {
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def_id.as_local().map(|def_id| tcx.hir().as_local_hir_id(def_id))
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}
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MonoItem::GlobalAsm(hir_id) => Some(hir_id),
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},
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item.symbol_name(tcx),
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)
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}
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let mut items: Vec<_> = self.items().iter().map(|(&i, &l)| (i, l)).collect();
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items.sort_by_cached_key(|&(i, _)| item_sort_key(tcx, i));
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items
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}
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pub fn codegen_dep_node(&self, tcx: TyCtxt<'tcx>) -> DepNode {
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DepConstructor::CompileCodegenUnit(tcx, self.name())
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}
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}
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impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for CodegenUnit<'tcx> {
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fn hash_stable(&self, hcx: &mut StableHashingContext<'a>, hasher: &mut StableHasher) {
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let CodegenUnit {
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ref items,
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name,
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// The size estimate is not relevant to the hash
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size_estimate: _,
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} = *self;
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name.hash_stable(hcx, hasher);
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let mut items: Vec<(Fingerprint, _)> = items
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.iter()
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.map(|(mono_item, &attrs)| {
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let mut hasher = StableHasher::new();
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mono_item.hash_stable(hcx, &mut hasher);
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let mono_item_fingerprint = hasher.finish();
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(mono_item_fingerprint, attrs)
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})
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.collect();
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items.sort_unstable_by_key(|i| i.0);
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items.hash_stable(hcx, hasher);
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}
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}
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pub struct CodegenUnitNameBuilder<'tcx> {
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tcx: TyCtxt<'tcx>,
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cache: FxHashMap<CrateNum, String>,
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}
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impl CodegenUnitNameBuilder<'tcx> {
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pub fn new(tcx: TyCtxt<'tcx>) -> Self {
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CodegenUnitNameBuilder { tcx, cache: Default::default() }
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}
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/// CGU names should fulfill the following requirements:
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/// - They should be able to act as a file name on any kind of file system
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/// - They should not collide with other CGU names, even for different versions
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/// of the same crate.
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///
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/// Consequently, we don't use special characters except for '.' and '-' and we
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/// prefix each name with the crate-name and crate-disambiguator.
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///
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/// This function will build CGU names of the form:
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///
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/// ```
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/// <crate-name>.<crate-disambiguator>[-in-<local-crate-id>](-<component>)*[.<special-suffix>]
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/// <local-crate-id> = <local-crate-name>.<local-crate-disambiguator>
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/// ```
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///
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/// The '.' before `<special-suffix>` makes sure that names with a special
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/// suffix can never collide with a name built out of regular Rust
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/// identifiers (e.g., module paths).
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pub fn build_cgu_name<I, C, S>(
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&mut self,
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cnum: CrateNum,
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components: I,
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special_suffix: Option<S>,
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) -> Symbol
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where
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I: IntoIterator<Item = C>,
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C: fmt::Display,
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S: fmt::Display,
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{
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let cgu_name = self.build_cgu_name_no_mangle(cnum, components, special_suffix);
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if self.tcx.sess.opts.debugging_opts.human_readable_cgu_names {
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cgu_name
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} else {
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Symbol::intern(&CodegenUnit::mangle_name(&cgu_name.as_str()))
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}
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}
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/// Same as `CodegenUnit::build_cgu_name()` but will never mangle the
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/// resulting name.
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pub fn build_cgu_name_no_mangle<I, C, S>(
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&mut self,
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cnum: CrateNum,
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components: I,
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special_suffix: Option<S>,
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) -> Symbol
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where
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I: IntoIterator<Item = C>,
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C: fmt::Display,
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|
S: fmt::Display,
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{
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use std::fmt::Write;
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|
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let mut cgu_name = String::with_capacity(64);
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|
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// Start out with the crate name and disambiguator
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let tcx = self.tcx;
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let crate_prefix = self.cache.entry(cnum).or_insert_with(|| {
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// Whenever the cnum is not LOCAL_CRATE we also mix in the
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|
// local crate's ID. Otherwise there can be collisions between CGUs
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// instantiating stuff for upstream crates.
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|
let local_crate_id = if cnum != LOCAL_CRATE {
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let local_crate_disambiguator = format!("{}", tcx.crate_disambiguator(LOCAL_CRATE));
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format!("-in-{}.{}", tcx.crate_name(LOCAL_CRATE), &local_crate_disambiguator[0..8])
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} else {
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|
String::new()
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|
};
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|
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|
let crate_disambiguator = tcx.crate_disambiguator(cnum).to_string();
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// Using a shortened disambiguator of about 40 bits
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|
format!("{}.{}{}", tcx.crate_name(cnum), &crate_disambiguator[0..8], local_crate_id)
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|
});
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|
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|
write!(cgu_name, "{}", crate_prefix).unwrap();
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|
|
|
// Add the components
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|
for component in components {
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|
write!(cgu_name, "-{}", component).unwrap();
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|
}
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|
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|
if let Some(special_suffix) = special_suffix {
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|
// We add a dot in here so it cannot clash with anything in a regular
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|
// Rust identifier
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|
write!(cgu_name, ".{}", special_suffix).unwrap();
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|
}
|
|
|
|
Symbol::intern(&cgu_name[..])
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|
}
|
|
}
|