Auto merge of #131422 - GnomedDev:smallvec-predicate-obligations, r=c…

…ompiler-errors 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 Gankra/thin-vec#66. This leads to a small (0.2-0.7%) performance gain in the latest perf run.
rust-lang · Oct 16, 2024 · 9618da7 · 9618da7
2 parents 9ce3675 + 8de8f46
commit 9618da7
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diff --git a/Cargo.lock b/Cargo.lock
@@ -1,6 +1,6 @@
 # This file is automatically @generated by Cargo.
 # It is not intended for manual editing.
-version = 3
+version = 4
 
 [[package]]
 name = "addr2line"
@@ -3857,6 +3857,7 @@ dependencies = [
  "rustc_target",
  "rustc_type_ir",
  "smallvec",
+ "thin-vec",
  "tracing",
 ]
 
@@ -4496,6 +4497,7 @@ dependencies = [
  "rustc_transmute",
  "rustc_type_ir",
  "smallvec",
+ "thin-vec",
  "tracing",
 ]
 
@@ -4567,6 +4569,7 @@ dependencies = [
  "rustc_span",
  "rustc_type_ir_macros",
  "smallvec",
+ "thin-vec",
  "tracing",
 ]
 

diff --git a/compiler/rustc_borrowck/src/type_check/mod.rs b/compiler/rustc_borrowck/src/type_check/mod.rs
@@ -18,6 +18,7 @@ use rustc_infer::infer::region_constraints::RegionConstraintData;
 use rustc_infer::infer::{
  BoundRegion, BoundRegionConversionTime, InferCtxt, NllRegionVariableOrigin,
 };
+use rustc_infer::traits::PredicateObligations;
 use rustc_middle::mir::tcx::PlaceTy;
 use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor};
 use rustc_middle::mir::*;
@@ -40,7 +41,6 @@ use rustc_span::source_map::Spanned;
 use rustc_span::symbol::sym;
 use rustc_span::{DUMMY_SP, Span};
 use rustc_target::abi::{FIRST_VARIANT, FieldIdx};
-use rustc_trait_selection::traits::PredicateObligation;
 use rustc_trait_selection::traits::query::type_op::custom::{
  CustomTypeOp, scrape_region_constraints,
 };
@@ -2940,7 +2940,7 @@ impl NormalizeLocation for Location {
 pub(super) struct InstantiateOpaqueType<'tcx> {
  pub base_universe: Option<ty::UniverseIndex>,
  pub region_constraints: Option<RegionConstraintData<'tcx>>,
- pub obligations: Vec<PredicateObligation<'tcx>>,
+ pub obligations: PredicateObligations<'tcx>,
 }
 
 impl<'tcx> TypeOp<'tcx> for InstantiateOpaqueType<'tcx> {

diff --git a/compiler/rustc_data_structures/src/lib.rs b/compiler/rustc_data_structures/src/lib.rs
@@ -76,6 +76,7 @@ pub mod svh;
 pub mod sync;
 pub mod tagged_ptr;
 pub mod temp_dir;
+pub mod thinvec;
 pub mod transitive_relation;
 pub mod unhash;
 pub mod unord;

diff --git a/compiler/rustc_data_structures/src/obligation_forest/mod.rs b/compiler/rustc_data_structures/src/obligation_forest/mod.rs
@@ -75,6 +75,7 @@ use std::fmt::Debug;
 use std::hash;
 use std::marker::PhantomData;
 
+use thin_vec::ThinVec;
 use tracing::debug;
 
 use crate::fx::{FxHashMap, FxHashSet};
@@ -141,7 +142,7 @@ pub trait ObligationProcessor {
 #[derive(Debug)]
 pub enum ProcessResult<O, E> {
  Unchanged,
- Changed(Vec<O>),
+ Changed(ThinVec<O>),
  Error(E),
 }
 
@@ -402,9 +403,10 @@ impl<O: ForestObligation> ObligationForest<O> {
  }
 
  /// Returns the set of obligations that are in a pending state.
- pub fn map_pending_obligations<P, F>(&self, f: F) -> Vec<P>
+ pub fn map_pending_obligations<P, F, R>(&self, f: F) -> R
  where
  F: Fn(&O) -> P,
+ R: FromIterator<P>,
  {
  self.nodes
  .iter()

diff --git a/compiler/rustc_data_structures/src/obligation_forest/tests.rs b/compiler/rustc_data_structures/src/obligation_forest/tests.rs
@@ -1,5 +1,7 @@
 use std::fmt;
 
+use thin_vec::thin_vec;
+
 use super::*;
 
 impl<'a> super::ForestObligation for &'a str {
@@ -101,9 +103,9 @@ fn push_pop() {
  // |-> A.3
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A" => ProcessResult::Changed(vec!["A.1", "A.2", "A.3"]),
+ "A" => ProcessResult::Changed(thin_vec!["A.1", "A.2", "A.3"]),
  "B" => ProcessResult::Error("B is for broken"),
- "C" => ProcessResult::Changed(vec![]),
+ "C" => ProcessResult::Changed(thin_vec![]),
  "A.1" | "A.2" | "A.3" => ProcessResult::Unchanged,
  _ => unreachable!(),
  },
@@ -123,8 +125,8 @@ fn push_pop() {
  |obligation| match *obligation {
  "A.1" => ProcessResult::Unchanged,
  "A.2" => ProcessResult::Unchanged,
- "A.3" => ProcessResult::Changed(vec!["A.3.i"]),
- "D" => ProcessResult::Changed(vec!["D.1", "D.2"]),
+ "A.3" => ProcessResult::Changed(thin_vec!["A.3.i"]),
+ "D" => ProcessResult::Changed(thin_vec!["D.1", "D.2"]),
  "A.3.i" | "D.1" | "D.2" => ProcessResult::Unchanged,
  _ => unreachable!(),
  },
@@ -139,11 +141,11 @@ fn push_pop() {
  // |-> D.2 |-> D.2.i
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A.1" => ProcessResult::Changed(vec![]),
+ "A.1" => ProcessResult::Changed(thin_vec![]),
  "A.2" => ProcessResult::Error("A is for apple"),
- "A.3.i" => ProcessResult::Changed(vec![]),
- "D.1" => ProcessResult::Changed(vec!["D.1.i"]),
- "D.2" => ProcessResult::Changed(vec!["D.2.i"]),
+ "A.3.i" => ProcessResult::Changed(thin_vec![]),
+ "D.1" => ProcessResult::Changed(thin_vec!["D.1.i"]),
+ "D.2" => ProcessResult::Changed(thin_vec!["D.2.i"]),
  "D.1.i" | "D.2.i" => ProcessResult::Unchanged,
  _ => unreachable!(),
  },
@@ -158,7 +160,7 @@ fn push_pop() {
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
  "D.1.i" => ProcessResult::Error("D is for dumb"),
- "D.2.i" => ProcessResult::Changed(vec![]),
+ "D.2.i" => ProcessResult::Changed(thin_vec![]),
  _ => panic!("unexpected obligation {:?}", obligation),
  },
  |_| {},
@@ -184,10 +186,10 @@ fn success_in_grandchildren() {
 
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A" => ProcessResult::Changed(vec!["A.1", "A.2", "A.3"]),
- "A.1" => ProcessResult::Changed(vec![]),
- "A.2" => ProcessResult::Changed(vec!["A.2.i", "A.2.ii"]),
- "A.3" => ProcessResult::Changed(vec![]),
+ "A" => ProcessResult::Changed(thin_vec!["A.1", "A.2", "A.3"]),
+ "A.1" => ProcessResult::Changed(thin_vec![]),
+ "A.2" => ProcessResult::Changed(thin_vec!["A.2.i", "A.2.ii"]),
+ "A.3" => ProcessResult::Changed(thin_vec![]),
  "A.2.i" | "A.2.ii" => ProcessResult::Unchanged,
  _ => unreachable!(),
  },
@@ -201,7 +203,7 @@ fn success_in_grandchildren() {
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
  "A.2.i" => ProcessResult::Unchanged,
- "A.2.ii" => ProcessResult::Changed(vec![]),
+ "A.2.ii" => ProcessResult::Changed(thin_vec![]),
  _ => unreachable!(),
  },
  |_| {},
@@ -211,7 +213,7 @@ fn success_in_grandchildren() {
 
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A.2.i" => ProcessResult::Changed(vec!["A.2.i.a"]),
+ "A.2.i" => ProcessResult::Changed(thin_vec!["A.2.i.a"]),
  "A.2.i.a" => ProcessResult::Unchanged,
  _ => unreachable!(),
  },
@@ -222,7 +224,7 @@ fn success_in_grandchildren() {
 
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A.2.i.a" => ProcessResult::Changed(vec![]),
+ "A.2.i.a" => ProcessResult::Changed(thin_vec![]),
  _ => unreachable!(),
  },
  |_| {},
@@ -247,7 +249,7 @@ fn to_errors_no_throw() {
  forest.register_obligation("A");
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A" => ProcessResult::Changed(vec!["A.1", "A.2", "A.3"]),
+ "A" => ProcessResult::Changed(thin_vec!["A.1", "A.2", "A.3"]),
  "A.1" | "A.2" | "A.3" => ProcessResult::Unchanged,
  _ => unreachable!(),
  },
@@ -269,7 +271,7 @@ fn diamond() {
  forest.register_obligation("A");
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A" => ProcessResult::Changed(vec!["A.1", "A.2"]),
+ "A" => ProcessResult::Changed(thin_vec!["A.1", "A.2"]),
  "A.1" | "A.2" => ProcessResult::Unchanged,
  _ => unreachable!(),
  },
@@ -280,8 +282,8 @@ fn diamond() {
 
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A.1" => ProcessResult::Changed(vec!["D"]),
- "A.2" => ProcessResult::Changed(vec!["D"]),
+ "A.1" => ProcessResult::Changed(thin_vec!["D"]),
+ "A.2" => ProcessResult::Changed(thin_vec!["D"]),
  "D" => ProcessResult::Unchanged,
  _ => unreachable!(),
  },
@@ -295,7 +297,7 @@ fn diamond() {
  |obligation| match *obligation {
  "D" => {
  d_count += 1;
- ProcessResult::Changed(vec![])
+ ProcessResult::Changed(thin_vec![])
  }
  _ => unreachable!(),
  },
@@ -313,7 +315,7 @@ fn diamond() {
  forest.register_obligation("A'");
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A'" => ProcessResult::Changed(vec!["A'.1", "A'.2"]),
+ "A'" => ProcessResult::Changed(thin_vec!["A'.1", "A'.2"]),
  "A'.1" | "A'.2" => ProcessResult::Unchanged,
  _ => unreachable!(),
  },
@@ -324,8 +326,8 @@ fn diamond() {
 
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A'.1" => ProcessResult::Changed(vec!["D'", "A'"]),
- "A'.2" => ProcessResult::Changed(vec!["D'"]),
+ "A'.1" => ProcessResult::Changed(thin_vec!["D'", "A'"]),
+ "A'.2" => ProcessResult::Changed(thin_vec!["D'"]),
  "D'" | "A'" => ProcessResult::Unchanged,
  _ => unreachable!(),
  },
@@ -366,7 +368,7 @@ fn done_dependency() {
 
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A: Sized" | "B: Sized" | "C: Sized" => ProcessResult::Changed(vec![]),
+ "A: Sized" | "B: Sized" | "C: Sized" => ProcessResult::Changed(thin_vec![]),
  _ => unreachable!(),
  },
  |_| {},
@@ -379,7 +381,9 @@ fn done_dependency() {
  forest.register_obligation("(A,B,C): Sized");
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "(A,B,C): Sized" => ProcessResult::Changed(vec!["A: Sized", "B: Sized", "C: Sized"]),
+ "(A,B,C): Sized" => {
+ ProcessResult::Changed(thin_vec!["A: Sized", "B: Sized", "C: Sized"])
+ }
  _ => unreachable!(),
  },
  |_| {},
@@ -399,10 +403,10 @@ fn orphan() {
 
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
- "A" => ProcessResult::Changed(vec!["D", "E"]),
+ "A" => ProcessResult::Changed(thin_vec!["D", "E"]),
  "B" => ProcessResult::Unchanged,
- "C1" => ProcessResult::Changed(vec![]),
- "C2" => ProcessResult::Changed(vec![]),
+ "C1" => ProcessResult::Changed(thin_vec![]),
+ "C2" => ProcessResult::Changed(thin_vec![]),
  "D" | "E" => ProcessResult::Unchanged,
  _ => unreachable!(),
  },
@@ -416,7 +420,7 @@ fn orphan() {
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
  "D" | "E" => ProcessResult::Unchanged,
- "B" => ProcessResult::Changed(vec!["D"]),
+ "B" => ProcessResult::Changed(thin_vec!["D"]),
  _ => unreachable!(),
  },
  |_| {},
@@ -459,7 +463,7 @@ fn simultaneous_register_and_error() {
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
  "A" => ProcessResult::Error("An error"),
- "B" => ProcessResult::Changed(vec!["A"]),
+ "B" => ProcessResult::Changed(thin_vec!["A"]),
  _ => unreachable!(),
  },
  |_| {},
@@ -474,7 +478,7 @@ fn simultaneous_register_and_error() {
  let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
  |obligation| match *obligation {
  "A" => ProcessResult::Error("An error"),
- "B" => ProcessResult::Changed(vec!["A"]),
+ "B" => ProcessResult::Changed(thin_vec!["A"]),
  _ => unreachable!(),
  },
  |_| {},