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Only disable cache if predicate has opaques within it

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This commit is contained in:
Michael Goulet 2024-11-05 02:02:56 +00:00
parent 82c24eccad
commit 49153739fd
1 changed files with 18 additions and 6 deletions
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24
compiler/rustc_trait_selection/src/traits/select/mod.rs
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@ -1310,7 +1310,7 @@ fn check_evaluation_cache(
trait_pred: ty::PolyTraitPredicate<'tcx>,
) -> Option<EvaluationResult> {
let tcx = self.tcx();
if self.can_use_global_caches(param_env) {
if self.can_use_global_caches(param_env, trait_pred) {
if let Some(res) = tcx.evaluation_cache.get(&(param_env, trait_pred), tcx) {
return Some(res);
}
@ -1331,7 +1331,7 @@ fn insert_evaluation_cache(
return;
}
if self.can_use_global_caches(param_env) && !trait_pred.has_infer() {
if self.can_use_global_caches(param_env, trait_pred) && !trait_pred.has_infer() {
debug!(?trait_pred, ?result, "insert_evaluation_cache global");
// This may overwrite the cache with the same value
// FIXME: Due to #50507 this overwrites the different values
@ -1476,7 +1476,11 @@ fn is_knowable<'o>(&mut self, stack: &TraitObligationStack<'o, 'tcx>) -> Result<
}
/// Returns `true` if the global caches can be used.
fn can_use_global_caches(&self, param_env: ty::ParamEnv<'tcx>) -> bool {
fn can_use_global_caches(
&self,
param_env: ty::ParamEnv<'tcx>,
pred: ty::PolyTraitPredicate<'tcx>,
) -> bool {
// If there are any inference variables in the `ParamEnv`, then we
// always use a cache local to this particular scope. Otherwise, we
// switch to a global cache.
@ -1494,7 +1498,15 @@ fn can_use_global_caches(&self, param_env: ty::ParamEnv<'tcx>) -> bool {
TypingMode::Coherence => false,
// Avoid using the global cache when we're defining opaque types
// as their hidden type may impact the result of candidate selection.
TypingMode::Analysis { defining_opaque_types } => defining_opaque_types.is_empty(),
//
// HACK: This is still theoretically unsound. Goals can indirectly rely
// on opaques in the defining scope, and it's easier to do so with TAIT.
// However, if we disqualify *all* goals from being cached, perf suffers.
// This is likely fixed by better caching in general in the new solver.
// See: <https://github.com/rust-lang/rust/issues/132064>.
TypingMode::Analysis { defining_opaque_types } => {
defining_opaque_types.is_empty() || !pred.has_opaque_types()
}
// The global cache is only used if there are no opaque types in
// the defining scope or we're outside of analysis.
//
@ -1512,7 +1524,7 @@ fn check_candidate_cache(
let tcx = self.tcx();
let pred = cache_fresh_trait_pred.skip_binder();
if self.can_use_global_caches(param_env) {
if self.can_use_global_caches(param_env, cache_fresh_trait_pred) {
if let Some(res) = tcx.selection_cache.get(&(param_env, pred), tcx) {
return Some(res);
}
@ -1562,7 +1574,7 @@ fn insert_candidate_cache(
return;
}
if self.can_use_global_caches(param_env) {
if self.can_use_global_caches(param_env, cache_fresh_trait_pred) {
if let Err(Overflow(OverflowError::Canonical)) = candidate {
// Don't cache overflow globally; we only produce this in certain modes.
} else if !pred.has_infer() && !candidate.has_infer() {