bjoernager/rust
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Auto merge of #131422 - GnomedDev:smallvec-predicate-obligations, r=compiler-errors

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Use `ThinVec` for PredicateObligation storage

~~I noticed while profiling clippy on a project that a large amount of time is being spent allocating `Vec`s for `PredicateObligation`, and the `Vec`s are often quite small. This is an attempt to optimise this by using SmallVec to avoid heap allocations for these common small Vecs.~~

This PR turns all the `Vec<PredicateObligation>` into a single type alias while avoiding referring to `Vec` around it, then swaps the type over to `ThinVec<PredicateObligation>` and fixes the fallout. This also contains an implementation of `ThinVec::extract_if`, copied from `Vec::extract_if` and currently being upstreamed to https://github.com/Gankra/thin-vec/pull/66.

This leads to a small (0.2-0.7%) performance gain in the latest perf run.
This commit is contained in:
bors 2024-10-16 04:06:14 +00:00
commit 9618da7c99
43 changed files with 414 additions and 255 deletions
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11
compiler/rustc_hir_analysis/src/autoderef.rs
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@ -1,4 +1,5 @@
use rustc_infer::infer::InferCtxt;
use rustc_infer::traits::PredicateObligations;
use rustc_middle::ty::{self, Ty, TyCtxt, TypeVisitableExt};
use rustc_session::Limit;
use rustc_span::Span;
@ -23,7 +24,7 @@ struct AutoderefSnapshot<'tcx> {
reached_recursion_limit: bool,
steps: Vec<(Ty<'tcx>, AutoderefKind)>,
cur_ty: Ty<'tcx>,
obligations: Vec<traits::PredicateObligation<'tcx>>,
obligations: PredicateObligations<'tcx>,
}
pub struct Autoderef<'a, 'tcx> {
@ -119,7 +120,7 @@ impl<'a, 'tcx> Autoderef<'a, 'tcx> {
state: AutoderefSnapshot {
steps: vec![],
cur_ty: infcx.resolve_vars_if_possible(base_ty),
obligations: vec![],
obligations: PredicateObligations::new(),
at_start: true,
reached_recursion_limit: false,
},
@ -165,7 +166,7 @@ impl<'a, 'tcx> Autoderef<'a, 'tcx> {
pub fn structurally_normalize(
&self,
ty: Ty<'tcx>,
) -> Option<(Ty<'tcx>, Vec<traits::PredicateObligation<'tcx>>)> {
) -> Option<(Ty<'tcx>, PredicateObligations<'tcx>)> {
let ocx = ObligationCtxt::new(self.infcx);
let Ok(normalized_ty) = ocx.structurally_normalize(
&traits::ObligationCause::misc(self.span, self.body_id),
@ -204,11 +205,11 @@ impl<'a, 'tcx> Autoderef<'a, 'tcx> {
self.state.steps.len()
}
pub fn into_obligations(self) -> Vec<traits::PredicateObligation<'tcx>> {
pub fn into_obligations(self) -> PredicateObligations<'tcx> {
self.state.obligations
}
pub fn current_obligations(&self) -> Vec<traits::PredicateObligation<'tcx>> {
pub fn current_obligations(&self) -> PredicateObligations<'tcx> {
self.state.obligations.clone()
}