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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9
compiler/rustc_middle/src/traits/mod.rs
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@ -25,6 +25,7 @@ use rustc_span::{DUMMY_SP, Span};
// FIXME: Remove this import and import via `solve::`
pub use rustc_type_ir::solve::{BuiltinImplSource, Reveal};
use smallvec::{SmallVec, smallvec};
use thin_vec::ThinVec;
pub use self::select::{EvaluationCache, EvaluationResult, OverflowError, SelectionCache};
use crate::mir::ConstraintCategory;
@ -625,14 +626,14 @@ pub enum ImplSource<'tcx, N> {
/// for some type parameter. The `Vec<N>` represents the
/// obligations incurred from normalizing the where-clause (if
/// any).
Param(Vec<N>),
Param(ThinVec<N>),
/// Successful resolution for a builtin impl.
Builtin(BuiltinImplSource, Vec<N>),
Builtin(BuiltinImplSource, ThinVec<N>),
}
impl<'tcx, N> ImplSource<'tcx, N> {
pub fn nested_obligations(self) -> Vec<N> {
pub fn nested_obligations(self) -> ThinVec<N> {
match self {
ImplSource::UserDefined(i) => i.nested,
ImplSource::Param(n) | ImplSource::Builtin(_, n) => n,
@ -686,7 +687,7 @@ impl<'tcx, N> ImplSource<'tcx, N> {
pub struct ImplSourceUserDefinedData<'tcx, N> {
pub impl_def_id: DefId,
pub args: GenericArgsRef<'tcx>,
pub nested: Vec<N>,
pub nested: ThinVec<N>,
}
#[derive(Clone, Debug, PartialEq, Eq, Hash, HashStable, PartialOrd, Ord)]