From ad887322541b1c255b210cf87fae675072d1027f Mon Sep 17 00:00:00 2001
From: Guillaume Gomez <guillaume.gomez@huawei.com>
Date: Sat, 26 Mar 2022 14:58:19 +0100
Subject: [PATCH] Fix perf issue for auto trait selection
---
compiler/rustc_middle/src/ty/sty.rs | 9 +++++++++
.../src/traits/auto_trait.rs | 18 ++++++++++++++++++
.../src/traits/select/mod.rs | 4 ++--
3 files changed, 29 insertions(+), 2 deletions(-)
diff --git a/compiler/rustc_middle/src/ty/sty.rs b/compiler/rustc_middle/src/ty/sty.rs
index 93ece753728..dc16460ca43 100644
--- a/compiler/rustc_middle/src/ty/sty.rs
+++ b/compiler/rustc_middle/src/ty/sty.rs
@@ -999,6 +999,15 @@ impl<'tcx> PolyTraitRef<'tcx> {
polarity: ty::ImplPolarity::Positive,
})
}
+
+ /// Same as [`PolyTraitRef::to_poly_trait_predicate`] but sets a negative polarity instead.
+ pub fn to_poly_trait_predicate_negative_polarity(&self) -> ty::PolyTraitPredicate<'tcx> {
+ self.map_bound(|trait_ref| ty::TraitPredicate {
+ trait_ref,
+ constness: ty::BoundConstness::NotConst,
+ polarity: ty::ImplPolarity::Negative,
+ })
+ }
}
/// An existential reference to a trait, where `Self` is erased.
diff --git a/compiler/rustc_trait_selection/src/traits/auto_trait.rs b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
index c9398d746d7..6f6f21aa788 100644
--- a/compiler/rustc_trait_selection/src/traits/auto_trait.rs
+++ b/compiler/rustc_trait_selection/src/traits/auto_trait.rs
@@ -94,6 +94,24 @@ impl<'tcx> AutoTraitFinder<'tcx> {
trait_pred.to_poly_trait_predicate(),
));
+ match result {
+ Ok(Some(ImplSource::UserDefined(_))) => {
+ debug!(
+ "find_auto_trait_generics({:?}): \
+ manual impl found, bailing out",
+ trait_ref
+ );
+ return true;
+ }
+ _ => {}
+ }
+
+ let result = selcx.select(&Obligation::new(
+ ObligationCause::dummy(),
+ orig_env,
+ trait_pred.to_poly_trait_predicate_negative_polarity(),
+ ));
+
match result {
Ok(Some(ImplSource::UserDefined(_))) => {
debug!(
diff --git a/compiler/rustc_trait_selection/src/traits/select/mod.rs b/compiler/rustc_trait_selection/src/traits/select/mod.rs
index 6d232d86d8a..4704d841012 100644
--- a/compiler/rustc_trait_selection/src/traits/select/mod.rs
+++ b/compiler/rustc_trait_selection/src/traits/select/mod.rs
@@ -1272,7 +1272,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// the master cache. Since coherence executes pretty quickly,
// it's not worth going to more trouble to increase the
// hit-rate, I don't think.
- if self.intercrate || self.allow_negative_impls {
+ if self.intercrate {
return false;
}
@@ -1289,7 +1289,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
// mode, so don't do any caching. In particular, we might
// re-use the same `InferCtxt` with both an intercrate
// and non-intercrate `SelectionContext`
- if self.intercrate || self.allow_negative_impls {
+ if self.intercrate {
return None;
}
let tcx = self.tcx();