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Auto merge of #94799 - lcnr:list-ty-perf, r=petrochenkov

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update `hash_stable` for `List<Ty<'tcx>>`

cc https://github.com/rust-lang/rust/pull/93505#issuecomment-1047538798

this is the hottest part changed since the pre-merge perf run
This commit is contained in:
bors 2022-05-10 10:53:47 +00:00
commit c51871c469
1 changed files with 5 additions and 7 deletions
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12
compiler/rustc_middle/src/ty/impls_ty.rs
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@ -86,18 +86,16 @@ impl<'a, 'tcx> HashStable<StableHashingContext<'a>> for ty::subst::GenericArgKin
//
// In order to make it very unlikely for the sequence of bytes being hashed for
// a `GenericArgKind::Type` to be the same as the sequence of bytes being
// hashed for one of the other variants, we hash a `0xFF` byte before hashing
// their discriminant (since the discriminant of `TyKind` is unlikely to ever start
// with 0xFF).
// hashed for one of the other variants, we hash some very high number instead
// of their actual discriminant since `TyKind` should never start with anything
// that high.
ty::subst::GenericArgKind::Type(ty) => ty.hash_stable(hcx, hasher),
ty::subst::GenericArgKind::Const(ct) => {
0xFFu8.hash_stable(hcx, hasher);
mem::discriminant(self).hash_stable(hcx, hasher);
0xF3u8.hash_stable(hcx, hasher);
ct.hash_stable(hcx, hasher);
}
ty::subst::GenericArgKind::Lifetime(lt) => {
0xFFu8.hash_stable(hcx, hasher);
mem::discriminant(self).hash_stable(hcx, hasher);
0xF5u8.hash_stable(hcx, hasher);
lt.hash_stable(hcx, hasher);
}
}