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perf: Drop irrelevant caller bounds from query type op keys [-0.16% primary; -21.5% async-trait-heavy] #79

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perf: Drop irrelevant caller bounds from query type op keys [-0.16% primary; -21.5% async-trait-heavy] #79

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30 changes: 28 additions & 2 deletions compiler/rustc_trait_selection/src/traits/query/type_op/mod.rs
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Original file line number Diff line number Diff line change
Expand Up @@ -4,7 +4,7 @@ use rustc_errors::ErrorGuaranteed;
use rustc_hir::def_id::LocalDefId;
use rustc_infer::traits::PredicateObligations;
use rustc_middle::traits::query::NoSolution;
use rustc_middle::ty::{ParamEnvAnd, TyCtxt, TypeFoldable};
use rustc_middle::ty::{self, ParamEnvAnd, TyCtxt, TypeFoldable, TypeVisitable, TypeVisitableExt};
use rustc_span::Span;

use crate::infer::canonical::{
Expand All @@ -25,6 +25,31 @@ pub use rustc_middle::traits::query::type_op::*;

use self::custom::scrape_region_constraints;

/// Replaces the param env of a type op goal with the empty one when it cannot affect the
/// outcome.
///
/// The canonicalized goal is a query cache key, so an irrelevant param env still keeps
/// bodies with unrelated where-clauses from sharing an entry. A caller bound mentioning a
/// generic parameter can never apply to a goal which mentions only global names, and
/// outlives clauses are not assembled as candidates for trait or projection goals.
fn erase_irrelevant_param_env<'tcx, Q: TypeVisitable<TyCtxt<'tcx>>>(
query_key: ParamEnvAnd<'tcx, Q>,
) -> ParamEnvAnd<'tcx, Q> {
if query_key.value.is_global()
&& query_key.param_env.caller_bounds().iter().all(|bound| {
bound.has_param()
|| matches!(
bound.kind().skip_binder(),
ty::ClauseKind::RegionOutlives(_) | ty::ClauseKind::TypeOutlives(_)
)
})
{
ParamEnvAnd { param_env: ty::ParamEnv::empty(), value: query_key.value }
} else {
query_key
}
}

/// "Type ops" are used in NLL to perform some particular action and
/// extract out the resulting region constraints (or an error if it
/// cannot be completed).
Expand Down Expand Up @@ -118,7 +143,8 @@ pub trait QueryTypeOp<'tcx>: fmt::Debug + Copy + TypeFoldable<TyCtxt<'tcx>> + 't

let mut canonical_var_values = OriginalQueryValues::default();
let old_param_env = query_key.param_env;
let canonical_self = infcx.canonicalize_query(query_key, &mut canonical_var_values);
let canonical_self = infcx
.canonicalize_query(erase_irrelevant_param_env(query_key), &mut canonical_var_values);
let canonical_result = Self::perform_query(infcx.tcx, canonical_self)?;

let InferOk { value, obligations } = infcx
Expand Down
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