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Auto merge of #81215 - cjgillot:defkey-mir, r=oli-obk

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Encode MIR metadata by iterating on DefId instead of traversing the HIR tree

Split out of https://github.com/rust-lang/rust/pull/80347.

This part only traverses `mir_keys` and encodes MIR according to the def kind.

r? `@oli-obk`
This commit is contained in:
bors 2021-02-05 18:21:47 +00:00
commit 23adf9fd84
1 changed files with 106 additions and 218 deletions
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324
compiler/rustc_metadata/src/rmeta/encoder.rs
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@ -2,15 +2,15 @@
use crate::rmeta::*;
use rustc_data_structures::fingerprint::{Fingerprint, FingerprintEncoder};
use rustc_data_structures::fx::{FxHashMap, FxHashSet, FxIndexSet};
use rustc_data_structures::fx::{FxHashMap, FxIndexSet};
use rustc_data_structures::stable_hasher::StableHasher;
use rustc_data_structures::sync::{join, Lrc};
use rustc_data_structures::sync::{join, par_iter, Lrc, ParallelIterator};
use rustc_hir as hir;
use rustc_hir::def::{CtorOf, DefKind};
use rustc_hir::def_id::{CrateNum, DefId, DefIndex, LocalDefId, CRATE_DEF_INDEX, LOCAL_CRATE};
use rustc_hir::definitions::DefPathData;
use rustc_hir::intravisit::{self, NestedVisitorMap, Visitor};
use rustc_hir::itemlikevisit::{ItemLikeVisitor, ParItemLikeVisitor};
use rustc_hir::itemlikevisit::ItemLikeVisitor;
use rustc_hir::lang_items;
use rustc_hir::{AnonConst, GenericParamKind};
use rustc_index::bit_set::GrowableBitSet;
@ -65,11 +65,6 @@ pub(super) struct EncodeContext<'a, 'tcx> {
required_source_files: Option<GrowableBitSet<usize>>,
is_proc_macro: bool,
hygiene_ctxt: &'a HygieneEncodeContext,
// Determines if MIR used for code generation will be included in the crate
// metadata. When emitting only metadata (e.g., cargo check), we can avoid
// generating optimized MIR altogether.
emit_codegen_mir: bool,
}
/// If the current crate is a proc-macro, returns early with `Lazy:empty()`.
@ -580,6 +575,7 @@ fn encode_crate_root(&mut self) -> Lazy<CrateRoot<'tcx>> {
// Encode the items.
i = self.position();
self.encode_def_ids();
self.encode_mir();
self.encode_info_for_items();
let item_bytes = self.position() - i;
@ -785,6 +781,53 @@ fn should_encode_stability(def_kind: DefKind) -> bool {
}
}
/// Whether we should encode MIR.
///
/// Computing, optimizing and encoding the MIR is a relatively expensive operation.
/// We want to avoid this work when not required. Therefore:
/// - we only compute `mir_for_ctfe` on items with const-eval semantics;
/// - we skip `optimized_mir` for check runs.
///
/// Return a pair, resp. for CTFE and for LLVM.
fn should_encode_mir(tcx: TyCtxt<'_>, def_id: LocalDefId) -> (bool, bool) {
match tcx.def_kind(def_id) {
// Constructors
DefKind::Ctor(_, _) => {
let mir_opt_base = tcx.sess.opts.output_types.should_codegen()
|| tcx.sess.opts.debugging_opts.always_encode_mir;
(true, mir_opt_base)
}
// Constants
DefKind::AnonConst | DefKind::AssocConst | DefKind::Static | DefKind::Const => {
(true, false)
}
// Full-fledged functions
DefKind::AssocFn | DefKind::Fn => {
let generics = tcx.generics_of(def_id);
let needs_inline = (generics.requires_monomorphization(tcx)
|| tcx.codegen_fn_attrs(def_id).requests_inline())
&& tcx.sess.opts.output_types.should_codegen();
// Only check the presence of the `const` modifier.
let is_const_fn = tcx.is_const_fn_raw(def_id.to_def_id());
let always_encode_mir = tcx.sess.opts.debugging_opts.always_encode_mir;
(is_const_fn, needs_inline || always_encode_mir)
}
// Closures can't be const fn.
DefKind::Closure => {
let generics = tcx.generics_of(def_id);
let needs_inline = (generics.requires_monomorphization(tcx)
|| tcx.codegen_fn_attrs(def_id).requests_inline())
&& tcx.sess.opts.output_types.should_codegen();
let always_encode_mir = tcx.sess.opts.debugging_opts.always_encode_mir;
(false, needs_inline || always_encode_mir)
}
// Generators require optimized MIR to compute layout.
DefKind::Generator => (false, true),
// The others don't have MIR.
_ => (false, false),
}
}
impl EncodeContext<'a, 'tcx> {
fn encode_def_ids(&mut self) {
if self.is_proc_macro {
@ -882,11 +925,6 @@ fn encode_enum_variant_ctor(&mut self, def: &ty::AdtDef, index: VariantIdx) {
self.encode_generics(def_id);
self.encode_explicit_predicates(def_id);
self.encode_inferred_outlives(def_id);
let opt_mir = tcx.sess.opts.debugging_opts.always_encode_mir || self.emit_codegen_mir;
if opt_mir {
self.encode_optimized_mir(def_id.expect_local());
}
self.encode_mir_for_ctfe(def_id.expect_local());
}
fn encode_info_for_mod(&mut self, id: hir::HirId, md: &hir::Mod<'_>) {
@ -972,11 +1010,6 @@ fn encode_struct_ctor(&mut self, adt_def: &ty::AdtDef, def_id: DefId) {
self.encode_generics(def_id);
self.encode_explicit_predicates(def_id);
self.encode_inferred_outlives(def_id);
let opt_mir = tcx.sess.opts.debugging_opts.always_encode_mir || self.emit_codegen_mir;
if opt_mir {
self.encode_optimized_mir(def_id.expect_local());
}
self.encode_mir_for_ctfe(def_id.expect_local());
}
fn encode_generics(&mut self, def_id: DefId) {
@ -1082,34 +1115,6 @@ fn encode_info_for_trait_item(&mut self, def_id: DefId) {
self.encode_generics(def_id);
self.encode_explicit_predicates(def_id);
self.encode_inferred_outlives(def_id);
// This should be kept in sync with `PrefetchVisitor.visit_trait_item`.
match trait_item.kind {
ty::AssocKind::Type => {}
ty::AssocKind::Const => {
if self.tcx.mir_keys(LOCAL_CRATE).contains(&def_id.expect_local()) {
self.encode_mir_for_ctfe(def_id.expect_local());
self.encode_promoted_mir(def_id.expect_local());
}
}
ty::AssocKind::Fn => {
let opt_mir =
tcx.sess.opts.debugging_opts.always_encode_mir || self.emit_codegen_mir;
if opt_mir {
if self.tcx.mir_keys(LOCAL_CRATE).contains(&def_id.expect_local()) {
self.encode_optimized_mir(def_id.expect_local());
self.encode_promoted_mir(def_id.expect_local());
}
}
}
}
}
fn should_encode_fn_opt_mir(&self, def_id: DefId) -> bool {
self.tcx.sess.opts.debugging_opts.always_encode_mir
|| (self.emit_codegen_mir
&& (self.tcx.generics_of(def_id).requires_monomorphization(self.tcx)
|| self.tcx.codegen_fn_attrs(def_id).requests_inline()))
}
fn encode_info_for_impl_item(&mut self, def_id: DefId) {
@ -1171,27 +1176,6 @@ fn encode_info_for_impl_item(&mut self, def_id: DefId) {
self.encode_generics(def_id);
self.encode_explicit_predicates(def_id);
self.encode_inferred_outlives(def_id);
// The following part should be kept in sync with `PrefetchVisitor.visit_impl_item`.
let (mir, mir_const) = match ast_item.kind {
hir::ImplItemKind::Const(..) => (false, true),
hir::ImplItemKind::Fn(ref sig, _) => {
let opt_mir = self.should_encode_fn_opt_mir(def_id);
let is_const_fn = sig.header.constness == hir::Constness::Const;
(opt_mir, is_const_fn)
}
hir::ImplItemKind::TyAlias(..) => (false, false),
};
if mir {
self.encode_optimized_mir(def_id.expect_local());
}
if mir || mir_const {
self.encode_promoted_mir(def_id.expect_local());
}
if mir_const {
self.encode_mir_for_ctfe(def_id.expect_local());
}
}
fn encode_fn_param_names_for_body(&mut self, body_id: hir::BodyId) -> Lazy<[Ident]> {
@ -1202,36 +1186,50 @@ fn encode_fn_param_names(&mut self, param_names: &[Ident]) -> Lazy<[Ident]> {
self.lazy(param_names.iter())
}
fn encode_mir_for_ctfe(&mut self, def_id: LocalDefId) {
debug!("EntryBuilder::encode_mir_for_ctfe({:?})", def_id);
record!(self.tables.mir_for_ctfe[def_id.to_def_id()] <- self.tcx.mir_for_ctfe(def_id));
let unused = self.tcx.unused_generic_params(def_id);
if !unused.is_empty() {
record!(self.tables.unused_generic_params[def_id.to_def_id()] <- unused);
fn encode_mir(&mut self) {
if self.is_proc_macro {
return;
}
let abstract_const = self.tcx.mir_abstract_const(def_id);
if let Ok(Some(abstract_const)) = abstract_const {
record!(self.tables.mir_abstract_consts[def_id.to_def_id()] <- abstract_const);
let mut keys_and_jobs = self
.tcx
.mir_keys(LOCAL_CRATE)
.iter()
.filter_map(|&def_id| {
let (encode_const, encode_opt) = should_encode_mir(self.tcx, def_id);
if encode_const || encode_opt {
Some((def_id, encode_const, encode_opt))
} else {
None
}
})
.collect::<Vec<_>>();
// Sort everything to ensure a stable order for diagnotics.
keys_and_jobs.sort_by_key(|&(def_id, _, _)| def_id);
for (def_id, encode_const, encode_opt) in keys_and_jobs.into_iter() {
debug_assert!(encode_const || encode_opt);
debug!("EntryBuilder::encode_mir({:?})", def_id);
if encode_opt {
record!(self.tables.mir[def_id.to_def_id()] <- self.tcx.optimized_mir(def_id));
}
if encode_const {
record!(self.tables.mir_for_ctfe[def_id.to_def_id()] <- self.tcx.mir_for_ctfe(def_id));
let abstract_const = self.tcx.mir_abstract_const(def_id);
if let Ok(Some(abstract_const)) = abstract_const {
record!(self.tables.mir_abstract_consts[def_id.to_def_id()] <- abstract_const);
}
}
record!(self.tables.promoted_mir[def_id.to_def_id()] <- self.tcx.promoted_mir(def_id));
let unused = self.tcx.unused_generic_params(def_id);
if !unused.is_empty() {
record!(self.tables.unused_generic_params[def_id.to_def_id()] <- unused);
}
}
}
fn encode_optimized_mir(&mut self, def_id: LocalDefId) {
debug!("EntryBuilder::encode_optimized_mir({:?})", def_id);
record!(self.tables.mir[def_id.to_def_id()] <- self.tcx.optimized_mir(def_id));
let unused = self.tcx.unused_generic_params(def_id);
if !unused.is_empty() {
record!(self.tables.unused_generic_params[def_id.to_def_id()] <- unused);
}
}
fn encode_promoted_mir(&mut self, def_id: LocalDefId) {
debug!("EncodeContext::encode_promoted_mir({:?})", def_id);
record!(self.tables.promoted_mir[def_id.to_def_id()] <- self.tcx.promoted_mir(def_id));
}
// Encodes the inherent implementations of a structure, enumeration, or trait.
fn encode_inherent_implementations(&mut self, def_id: DefId) {
debug!("EncodeContext::encode_inherent_implementations({:?})", def_id);
@ -1487,28 +1485,6 @@ fn encode_info_for_item(&mut self, def_id: DefId, item: &'tcx hir::Item<'tcx>) {
}
_ => {}
}
// The following part should be kept in sync with `PrefetchVisitor.visit_item`.
let (mir, const_mir) = match item.kind {
hir::ItemKind::Static(..) | hir::ItemKind::Const(..) => (false, true),
hir::ItemKind::Fn(ref sig, ..) => {
let opt_mir = self.should_encode_fn_opt_mir(def_id);
let is_const_fn = sig.header.constness == hir::Constness::Const;
// We don't need the optimized MIR for const fns.
(opt_mir, is_const_fn)
}
_ => (false, false),
};
if mir {
self.encode_optimized_mir(def_id.expect_local());
}
if mir || const_mir {
self.encode_promoted_mir(def_id.expect_local());
}
if const_mir {
self.encode_mir_for_ctfe(def_id.expect_local());
}
}
/// Serialize the text of exported macros
@ -1550,14 +1526,6 @@ fn encode_info_for_closure(&mut self, def_id: LocalDefId) {
record!(self.tables.fn_sig[def_id] <- substs.as_closure().sig());
}
self.encode_generics(def_id.to_def_id());
let opt_mir = // FIXME: Optimized MIR is necessary to determine the layout of generators.
matches!(ty.kind(), ty::Generator(..))
|| self.tcx.sess.opts.debugging_opts.always_encode_mir
|| self.emit_codegen_mir;
if opt_mir {
self.encode_optimized_mir(def_id);
self.encode_promoted_mir(def_id);
}
}
fn encode_info_for_anon_const(&mut self, def_id: LocalDefId) {
@ -1572,8 +1540,6 @@ fn encode_info_for_anon_const(&mut self, def_id: LocalDefId) {
self.encode_generics(def_id.to_def_id());
self.encode_explicit_predicates(def_id.to_def_id());
self.encode_inferred_outlives(def_id.to_def_id());
self.encode_mir_for_ctfe(def_id);
self.encode_promoted_mir(def_id);
}
fn encode_native_libraries(&mut self) -> Lazy<[NativeLib]> {
@ -2038,90 +2004,25 @@ fn visit_foreign_item(&mut self, _foreign_item: &'v hir::ForeignItem<'v>) {}
/// Used to prefetch queries which will be needed later by metadata encoding.
/// Only a subset of the queries are actually prefetched to keep this code smaller.
struct PrefetchVisitor<'tcx> {
tcx: TyCtxt<'tcx>,
mir_keys: &'tcx FxHashSet<LocalDefId>,
}
impl<'tcx> PrefetchVisitor<'tcx> {
fn prefetch_ctfe_mir(&self, def_id: LocalDefId) {
if self.mir_keys.contains(&def_id) {
self.tcx.ensure().mir_for_ctfe(def_id);
self.tcx.ensure().promoted_mir(def_id);
}
}
fn prefetch_mir(&self, def_id: LocalDefId) {
if self.mir_keys.contains(&def_id) {
self.tcx.ensure().optimized_mir(def_id);
self.tcx.ensure().promoted_mir(def_id);
}
}
}
impl<'tcx, 'v> ParItemLikeVisitor<'v> for PrefetchVisitor<'tcx> {
fn visit_item(&self, item: &hir::Item<'_>) {
// This should be kept in sync with `encode_info_for_item`.
let tcx = self.tcx;
match item.kind {
hir::ItemKind::Static(..) | hir::ItemKind::Const(..) => {
self.prefetch_ctfe_mir(tcx.hir().local_def_id(item.hir_id))
}
hir::ItemKind::Fn(ref sig, ..) => {
let def_id = tcx.hir().local_def_id(item.hir_id);
let opt_mir = tcx.generics_of(def_id.to_def_id()).requires_monomorphization(tcx)
|| tcx.codegen_fn_attrs(def_id.to_def_id()).requests_inline();
if opt_mir {
self.prefetch_mir(def_id)
}
if sig.header.constness == hir::Constness::Const {
self.prefetch_ctfe_mir(def_id);
}
}
_ => (),
}
fn prefetch_mir(tcx: TyCtxt<'_>) {
if !tcx.sess.opts.output_types.should_codegen() {
// We won't emit MIR, so don't prefetch it.
return;
}
fn visit_trait_item(&self, trait_item: &'v hir::TraitItem<'v>) {
// This should be kept in sync with `encode_info_for_trait_item`.
let def_id = self.tcx.hir().local_def_id(trait_item.hir_id);
match trait_item.kind {
hir::TraitItemKind::Type(..) => {}
hir::TraitItemKind::Const(..) => {
self.prefetch_ctfe_mir(def_id);
}
hir::TraitItemKind::Fn(..) => {
self.prefetch_mir(def_id);
}
}
}
par_iter(tcx.mir_keys(LOCAL_CRATE)).for_each(|&def_id| {
let (encode_const, encode_opt) = should_encode_mir(tcx, def_id);
fn visit_impl_item(&self, impl_item: &'v hir::ImplItem<'v>) {
// This should be kept in sync with `encode_info_for_impl_item`.
let tcx = self.tcx;
match impl_item.kind {
hir::ImplItemKind::Const(..) => {
self.prefetch_ctfe_mir(tcx.hir().local_def_id(impl_item.hir_id))
}
hir::ImplItemKind::Fn(ref sig, _) => {
let def_id = tcx.hir().local_def_id(impl_item.hir_id);
let opt_mir = tcx.generics_of(def_id.to_def_id()).requires_monomorphization(tcx)
|| tcx.codegen_fn_attrs(def_id.to_def_id()).requests_inline();
let is_const_fn = sig.header.constness == hir::Constness::Const;
if opt_mir {
self.prefetch_mir(def_id)
}
if is_const_fn {
self.prefetch_ctfe_mir(def_id);
}
}
hir::ImplItemKind::TyAlias(..) => (),
if encode_const {
tcx.ensure().mir_for_ctfe(def_id);
}
}
fn visit_foreign_item(&self, _foreign_item: &'v hir::ForeignItem<'v>) {
// This should be kept in sync with `encode_info_for_foreign_item`.
// Foreign items contain no MIR.
}
if encode_opt {
tcx.ensure().optimized_mir(def_id);
}
if encode_opt || encode_const {
tcx.ensure().promoted_mir(def_id);
}
})
}
// NOTE(eddyb) The following comment was preserved for posterity, even
@ -2161,19 +2062,7 @@ pub(super) fn encode_metadata(tcx: TyCtxt<'_>) -> EncodedMetadata {
// Prefetch some queries used by metadata encoding.
// This is not necessary for correctness, but is only done for performance reasons.
// It can be removed if it turns out to cause trouble or be detrimental to performance.
join(
|| {
if !tcx.sess.opts.output_types.should_codegen() {
// We won't emit MIR, so don't prefetch it.
return;
}
tcx.hir().krate().par_visit_all_item_likes(&PrefetchVisitor {
tcx,
mir_keys: tcx.mir_keys(LOCAL_CRATE),
});
},
|| tcx.exported_symbols(LOCAL_CRATE),
);
join(|| prefetch_mir(tcx), || tcx.exported_symbols(LOCAL_CRATE));
},
)
.0
@ -2206,7 +2095,6 @@ fn encode_metadata_impl(tcx: TyCtxt<'_>) -> EncodedMetadata {
required_source_files,
is_proc_macro: tcx.sess.crate_types().contains(&CrateType::ProcMacro),
hygiene_ctxt: &hygiene_ctxt,
emit_codegen_mir: tcx.sess.opts.output_types.should_codegen(),
};
// Encode the rustc version string in a predictable location.