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Reorder MIR encoding checks

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Start from least expensive checks when deciding whether to encode MIR or not.

No functional changes intended.
This commit is contained in:
Tomasz Miąsko 2021-01-05 00:00:00 +00:00
parent 704e47f78b
commit 1bf3949398
1 changed files with 20 additions and 25 deletions
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45
compiler/rustc_metadata/src/rmeta/encoder.rs
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@ -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()`.
@ -1032,11 +1037,6 @@ impl EncodeContext<'a, 'tcx> {
}
}
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 encode_info_for_impl_item(&mut self, def_id: DefId) {
debug!("EncodeContext::encode_info_for_impl_item({:?})", def_id);
let tcx = self.tcx;
@ -1105,13 +1105,12 @@ 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 = tcx.sess.opts.debugging_opts.always_encode_mir
|| (self.emit_codegen_mir
&& (tcx.generics_of(def_id).requires_monomorphization(tcx)
|| tcx.codegen_fn_attrs(def_id).requests_inline()));
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),
};
@ -1433,16 +1432,13 @@ 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.tcx.sess.opts.debugging_opts.always_encode_mir
|| (self.emit_codegen_mir
&& (tcx.generics_of(def_id).requires_monomorphization(tcx)
|| tcx.codegen_fn_attrs(def_id).requests_inline()));
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),
};
@ -2008,10 +2004,9 @@ 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 {
@ -2045,11 +2040,10 @@ 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 {
@ -2148,6 +2142,7 @@ 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.