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perf: only check for rustc_trivial_field_reads attribute on traits

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The checks removed here caused a small perf regression:
https://github.com/rust-lang/rust/pull/88824#issuecomment-932664761

Since the attribute is currently only applied to traits, I don't think
it's worth keeping the additional checks for now.
If/when we decide to apply the attribute somewhere else, we can
(partially) revert this and evaluate if the perf impact is acceptable.
This commit is contained in:
Erik Desjardins 2021-10-01 22:07:22 -04:00
parent c02371c442
commit eb4ba58572
1 changed files with 1 additions and 23 deletions
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24
compiler/rustc_passes/src/dead.rs
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@ -254,31 +254,11 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
let has_attr = |def_id| self.tcx.has_attr(def_id, sym::rustc_trivial_field_reads);
if has_attr(def_id) {
return true;
}
if let Some(impl_of) = self.tcx.impl_of_method(def_id) {
if has_attr(impl_of) {
return true;
}
if let Some(trait_of) = self.tcx.trait_id_of_impl(impl_of) {
if has_attr(trait_of) {
return true;
}
if let Some(method_ident) = self.tcx.opt_item_name(def_id) {
if let Some(trait_method) = self
.tcx
.associated_items(trait_of)
.find_by_name_and_kind(self.tcx, method_ident, ty::AssocKind::Fn, trait_of)
{
if has_attr(trait_method.def_id) {
return true;
}
}
}
}
} else if let Some(trait_of) = self.tcx.trait_of_item(def_id) {
if has_attr(trait_of) {
@ -291,9 +271,7 @@ impl<'tcx> MarkSymbolVisitor<'tcx> {
fn visit_node(&mut self, node: Node<'tcx>) {
if let Some(item_def_id) = match node {
Node::Item(hir::Item { def_id, .. })
| Node::ForeignItem(hir::ForeignItem { def_id, .. })
| Node::TraitItem(hir::TraitItem { def_id, .. })
Node::TraitItem(hir::TraitItem { def_id, .. })
| Node::ImplItem(hir::ImplItem { def_id, .. }) => Some(def_id.to_def_id()),
_ => None,
} {