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Auto merge of #83932 - lcnr:probe-perf, r=estebank

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use a `SmallVec` in `impl_or_trait_item`

#83293 showed that this is fairly hot, slightly improves max-rss and cpu cycles, does not noticeably improve instruction counts
This commit is contained in:
bors 2021-04-07 12:52:33 +00:00
commit b01026de46
1 changed files with 4 additions and 2 deletions
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6
compiler/rustc_typeck/src/check/method/probe.rs
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@ -1768,7 +1768,9 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
/// Finds the method with the appropriate name (or return type, as the case may be). If
/// `allow_similar_names` is set, find methods with close-matching names.
fn impl_or_trait_item(&self, def_id: DefId) -> Vec<ty::AssocItem> {
// The length of the returned iterator is nearly always 0 or 1 and this
// method is fairly hot.
fn impl_or_trait_item(&self, def_id: DefId) -> SmallVec<[ty::AssocItem; 1]> {
if let Some(name) = self.method_name {
if self.allow_similar_names {
let max_dist = max(name.as_str().len(), 3) / 3;
@ -1784,7 +1786,7 @@ impl<'a, 'tcx> ProbeContext<'a, 'tcx> {
} else {
self.fcx
.associated_item(def_id, name, Namespace::ValueNS)
.map_or_else(Vec::new, |x| vec![x])
.map_or_else(SmallVec::new, |x| SmallVec::from_buf([x]))
}
} else {
self.tcx.associated_items(def_id).in_definition_order().copied().collect()