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Consistently avoid constructing optimized MIR when not doing codegen #80718

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merged 3 commits into from
Jan 13, 2021
Merged

Consistently avoid constructing optimized MIR when not doing codegen #80718

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1bf3949
Reorder MIR encoding checks
tmiasko Jan 5, 2021
a6dd7b5
Consistently avoid constructing optimized MIR when not doing codegen
tmiasko Jan 12, 2021
1685731
Skip promoted mir of struct constructors & enum constructors
tmiasko Jan 13, 2021
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71 changes: 39 additions & 32 deletions compiler/rustc_metadata/src/rmeta/encoder.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -66,6 +66,11 @@ 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()`.
Expand Down Expand Up @@ -787,9 +792,11 @@ impl EncodeContext<'a, 'tcx> {
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());
self.encode_optimized_mir(def_id.expect_local());
self.encode_promoted_mir(def_id.expect_local());
}

fn encode_info_for_mod(&mut self, id: hir::HirId, md: &hir::Mod<'_>, attrs: &[ast::Attribute]) {
Expand Down Expand Up @@ -895,9 +902,11 @@ impl EncodeContext<'a, 'tcx> {
self.encode_generics(def_id);
self.encode_explicit_predicates(def_id);
self.encode_inferred_outlives(def_id);
self.encode_optimized_mir(def_id.expect_local());
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());
self.encode_promoted_mir(def_id.expect_local());
}

fn encode_generics(&mut self, def_id: DefId) {
Expand Down Expand Up @@ -1024,17 +1033,23 @@ impl EncodeContext<'a, 'tcx> {
}
}
ty::AssocKind::Fn => {
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());
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 metadata_output_only(&self) -> bool {
// MIR optimisation can be skipped when we're just interested in the metadata.
!self.tcx.sess.opts.output_types.should_codegen()
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) {
Expand Down Expand Up @@ -1105,13 +1120,9 @@ impl EncodeContext<'a, 'tcx> {
let (mir, mir_const) = match ast_item.kind {
hir::ImplItemKind::Const(..) => (false, true),
hir::ImplItemKind::Fn(ref sig, _) => {
let generics = self.tcx.generics_of(def_id);
let needs_inline = (generics.requires_monomorphization(self.tcx)
|| tcx.codegen_fn_attrs(def_id).requests_inline())
&& !self.metadata_output_only();
let opt_mir = self.should_encode_fn_opt_mir(def_id);
let is_const_fn = sig.header.constness == hir::Constness::Const;
let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
(needs_inline || always_encode_mir, is_const_fn)
(opt_mir, is_const_fn)
}
hir::ImplItemKind::TyAlias(..) => (false, false),
};
Expand Down Expand Up @@ -1433,16 +1444,10 @@ impl EncodeContext<'a, 'tcx> {
let (mir, const_mir) = match item.kind {
hir::ItemKind::Static(..) | hir::ItemKind::Const(..) => (false, true),
hir::ItemKind::Fn(ref sig, ..) => {
let generics = tcx.generics_of(def_id);
let needs_inline = (generics.requires_monomorphization(tcx)
|| tcx.codegen_fn_attrs(def_id).requests_inline())
&& !self.metadata_output_only();

let opt_mir = self.should_encode_fn_opt_mir(def_id);
let is_const_fn = sig.header.constness == hir::Constness::Const;
let always_encode_mir = self.tcx.sess.opts.debugging_opts.always_encode_mir;
let mir = needs_inline || always_encode_mir;
// We don't need the optimized MIR for const fns.
(mir, is_const_fn)
(opt_mir, is_const_fn)
}
_ => (false, false),
};
Expand Down Expand Up @@ -1502,8 +1507,11 @@ impl EncodeContext<'a, 'tcx> {
record!(self.tables.fn_sig[def_id] <- substs.as_closure().sig());
}
self.encode_generics(def_id.to_def_id());
self.encode_optimized_mir(def_id);
self.encode_promoted_mir(def_id);
let opt_mir = 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) {
Expand Down Expand Up @@ -2008,10 +2016,9 @@ impl<'tcx, 'v> ParItemLikeVisitor<'v> for PrefetchVisitor<'tcx> {
}
hir::ItemKind::Fn(ref sig, ..) => {
let def_id = tcx.hir().local_def_id(item.hir_id);
let generics = tcx.generics_of(def_id.to_def_id());
let needs_inline = generics.requires_monomorphization(tcx)
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 needs_inline {
if opt_mir {
self.prefetch_mir(def_id)
}
if sig.header.constness == hir::Constness::Const {
Expand Down Expand Up @@ -2045,11 +2052,10 @@ impl<'tcx, 'v> ParItemLikeVisitor<'v> for PrefetchVisitor<'tcx> {
}
hir::ImplItemKind::Fn(ref sig, _) => {
let def_id = tcx.hir().local_def_id(impl_item.hir_id);
let generics = tcx.generics_of(def_id.to_def_id());
let needs_inline = generics.requires_monomorphization(tcx)
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 needs_inline {
if opt_mir {
self.prefetch_mir(def_id)
}
if is_const_fn {
Expand Down Expand Up @@ -2148,6 +2154,7 @@ 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.
Expand Down