bjoernager/rust
bjoernager/rust
1
Fork 0
Code Issues Pull requests Activity

Improve caching during trait evaluation

Browse source 
Previously, we would 'forget' that we had `'static` regions in some
place during trait evaluation. This lead to us producing
`EvaluatedToOkModuloRegions` when we could have produced
`EvaluatedToOk`, causing us to perform unnecessary work.

This PR preserves `'static` regions when we canonicalize a predicate for
`evaluate_obligation`, and when we 'freshen' a predicate during trait
evaluation. Thie ensures that evaluating a predicate containing
`'static` regions can produce `EvaluatedToOk` (assuming that we
don't end up introducing any region dependencies during evaluation).

Building off of this improved caching, we use
`predicate_must_hold_considering_regions` during fulfillment of
projection predicates to see if we can skip performing additional work.
We already do this for trait predicates, but doing this for projection
predicates lead to mixed performance results without the above caching
improvements.
This commit is contained in:
Aaron Hill 2021-07-07 10:56:26 -05:00
parent 32c9b7b091
commit 3291218f47
No known key found for this signature in database
GPG key ID: B4087E510E98B164
8 changed files with 49 additions and 28 deletions
Download patch file Download diff file Expand all files Collapse all files

8
compiler/rustc_trait_selection/src/traits/select/mod.rs
View file

@ -216,7 +216,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
pub fn new(infcx: &'cx InferCtxt<'cx, 'tcx>) -> SelectionContext<'cx, 'tcx> {
SelectionContext {
infcx,
freshener: infcx.freshener(),
freshener: infcx.freshener_keep_static(),
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
@ -227,7 +227,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
pub fn intercrate(infcx: &'cx InferCtxt<'cx, 'tcx>) -> SelectionContext<'cx, 'tcx> {
SelectionContext {
infcx,
freshener: infcx.freshener(),
freshener: infcx.freshener_keep_static(),
intercrate: true,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,
@ -242,7 +242,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
debug!(?allow_negative_impls, "with_negative");
SelectionContext {
infcx,
freshener: infcx.freshener(),
freshener: infcx.freshener_keep_static(),
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls,
@ -257,7 +257,7 @@ impl<'cx, 'tcx> SelectionContext<'cx, 'tcx> {
debug!(?query_mode, "with_query_mode");
SelectionContext {
infcx,
freshener: infcx.freshener(),
freshener: infcx.freshener_keep_static(),
intercrate: false,
intercrate_ambiguity_causes: None,
allow_negative_impls: false,