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Auto merge of #131422 - GnomedDev:smallvec-predicate-obligations, r=compiler-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 mozilla/thin-vec#66. This leads to a small (0.2-0.7%) performance gain in the latest perf run.
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‎Cargo.lock‎

Lines changed: 4 additions & 1 deletion
Original file line numberDiff line numberDiff line change
@@ -1,6 +1,6 @@
11
# This file is automatically @generated by Cargo.
22
# It is not intended for manual editing.
3-
version = 3
3+
version = 4
44

55
[[package]]
66
name = "addr2line"
@@ -3857,6 +3857,7 @@ dependencies = [
38573857
"rustc_target",
38583858
"rustc_type_ir",
38593859
"smallvec",
3860+
"thin-vec",
38603861
"tracing",
38613862
]
38623863

@@ -4496,6 +4497,7 @@ dependencies = [
44964497
"rustc_transmute",
44974498
"rustc_type_ir",
44984499
"smallvec",
4500+
"thin-vec",
44994501
"tracing",
45004502
]
45014503

@@ -4567,6 +4569,7 @@ dependencies = [
45674569
"rustc_span",
45684570
"rustc_type_ir_macros",
45694571
"smallvec",
4572+
"thin-vec",
45704573
"tracing",
45714574
]
45724575

‎compiler/rustc_borrowck/src/type_check/mod.rs‎

Lines changed: 2 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -18,6 +18,7 @@ use rustc_infer::infer::region_constraints::RegionConstraintData;
1818
use rustc_infer::infer::{
1919
BoundRegion, BoundRegionConversionTime, InferCtxt, NllRegionVariableOrigin,
2020
};
21+
use rustc_infer::traits::PredicateObligations;
2122
use rustc_middle::mir::tcx::PlaceTy;
2223
use rustc_middle::mir::visit::{NonMutatingUseContext, PlaceContext, Visitor};
2324
use rustc_middle::mir::*;
@@ -40,7 +41,6 @@ use rustc_span::source_map::Spanned;
4041
use rustc_span::symbol::sym;
4142
use rustc_span::{DUMMY_SP, Span};
4243
use rustc_target::abi::{FIRST_VARIANT, FieldIdx};
43-
use rustc_trait_selection::traits::PredicateObligation;
4444
use rustc_trait_selection::traits::query::type_op::custom::{
4545
CustomTypeOp, scrape_region_constraints,
4646
};
@@ -2940,7 +2940,7 @@ impl NormalizeLocation for Location {
29402940
pub(super) struct InstantiateOpaqueType<'tcx> {
29412941
pub base_universe: Option<ty::UniverseIndex>,
29422942
pub region_constraints: Option<RegionConstraintData<'tcx>>,
2943-
pub obligations: Vec<PredicateObligation<'tcx>>,
2943+
pub obligations: PredicateObligations<'tcx>,
29442944
}
29452945

29462946
impl<'tcx> TypeOp<'tcx> for InstantiateOpaqueType<'tcx> {

‎compiler/rustc_data_structures/src/lib.rs‎

Lines changed: 1 addition & 0 deletions
Original file line numberDiff line numberDiff line change
@@ -76,6 +76,7 @@ pub mod svh;
7676
pub mod sync;
7777
pub mod tagged_ptr;
7878
pub mod temp_dir;
79+
pub mod thinvec;
7980
pub mod transitive_relation;
8081
pub mod unhash;
8182
pub mod unord;

‎compiler/rustc_data_structures/src/obligation_forest/mod.rs‎

Lines changed: 4 additions & 2 deletions
Original file line numberDiff line numberDiff line change
@@ -75,6 +75,7 @@ use std::fmt::Debug;
7575
use std::hash;
7676
use std::marker::PhantomData;
7777

78+
use thin_vec::ThinVec;
7879
use tracing::debug;
7980

8081
use crate::fx::{FxHashMap, FxHashSet};
@@ -141,7 +142,7 @@ pub trait ObligationProcessor {
141142
#[derive(Debug)]
142143
pub enum ProcessResult<O, E> {
143144
Unchanged,
144-
Changed(Vec<O>),
145+
Changed(ThinVec<O>),
145146
Error(E),
146147
}
147148

@@ -402,9 +403,10 @@ impl<O: ForestObligation> ObligationForest<O> {
402403
}
403404

404405
/// Returns the set of obligations that are in a pending state.
405-
pub fn map_pending_obligations<P, F>(&self, f: F) -> Vec<P>
406+
pub fn map_pending_obligations<P, F, R>(&self, f: F) -> R
406407
where
407408
F: Fn(&O) -> P,
409+
R: FromIterator<P>,
408410
{
409411
self.nodes
410412
.iter()

‎compiler/rustc_data_structures/src/obligation_forest/tests.rs‎

Lines changed: 36 additions & 32 deletions
Original file line numberDiff line numberDiff line change
@@ -1,5 +1,7 @@
11
use std::fmt;
22

3+
use thin_vec::thin_vec;
4+
35
use super::*;
46

57
impl<'a> super::ForestObligation for &'a str {
@@ -101,9 +103,9 @@ fn push_pop() {
101103
// |-> A.3
102104
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
103105
|obligation| match *obligation {
104-
"A" => ProcessResult::Changed(vec!["A.1", "A.2", "A.3"]),
106+
"A" => ProcessResult::Changed(thin_vec!["A.1", "A.2", "A.3"]),
105107
"B" => ProcessResult::Error("B is for broken"),
106-
"C" => ProcessResult::Changed(vec![]),
108+
"C" => ProcessResult::Changed(thin_vec![]),
107109
"A.1" | "A.2" | "A.3" => ProcessResult::Unchanged,
108110
_ => unreachable!(),
109111
},
@@ -123,8 +125,8 @@ fn push_pop() {
123125
|obligation| match *obligation {
124126
"A.1" => ProcessResult::Unchanged,
125127
"A.2" => ProcessResult::Unchanged,
126-
"A.3" => ProcessResult::Changed(vec!["A.3.i"]),
127-
"D" => ProcessResult::Changed(vec!["D.1", "D.2"]),
128+
"A.3" => ProcessResult::Changed(thin_vec!["A.3.i"]),
129+
"D" => ProcessResult::Changed(thin_vec!["D.1", "D.2"]),
128130
"A.3.i" | "D.1" | "D.2" => ProcessResult::Unchanged,
129131
_ => unreachable!(),
130132
},
@@ -139,11 +141,11 @@ fn push_pop() {
139141
// |-> D.2 |-> D.2.i
140142
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
141143
|obligation| match *obligation {
142-
"A.1" => ProcessResult::Changed(vec![]),
144+
"A.1" => ProcessResult::Changed(thin_vec![]),
143145
"A.2" => ProcessResult::Error("A is for apple"),
144-
"A.3.i" => ProcessResult::Changed(vec![]),
145-
"D.1" => ProcessResult::Changed(vec!["D.1.i"]),
146-
"D.2" => ProcessResult::Changed(vec!["D.2.i"]),
146+
"A.3.i" => ProcessResult::Changed(thin_vec![]),
147+
"D.1" => ProcessResult::Changed(thin_vec!["D.1.i"]),
148+
"D.2" => ProcessResult::Changed(thin_vec!["D.2.i"]),
147149
"D.1.i" | "D.2.i" => ProcessResult::Unchanged,
148150
_ => unreachable!(),
149151
},
@@ -158,7 +160,7 @@ fn push_pop() {
158160
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
159161
|obligation| match *obligation {
160162
"D.1.i" => ProcessResult::Error("D is for dumb"),
161-
"D.2.i" => ProcessResult::Changed(vec![]),
163+
"D.2.i" => ProcessResult::Changed(thin_vec![]),
162164
_ => panic!("unexpected obligation {:?}", obligation),
163165
},
164166
|_| {},
@@ -184,10 +186,10 @@ fn success_in_grandchildren() {
184186

185187
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
186188
|obligation| match *obligation {
187-
"A" => ProcessResult::Changed(vec!["A.1", "A.2", "A.3"]),
188-
"A.1" => ProcessResult::Changed(vec![]),
189-
"A.2" => ProcessResult::Changed(vec!["A.2.i", "A.2.ii"]),
190-
"A.3" => ProcessResult::Changed(vec![]),
189+
"A" => ProcessResult::Changed(thin_vec!["A.1", "A.2", "A.3"]),
190+
"A.1" => ProcessResult::Changed(thin_vec![]),
191+
"A.2" => ProcessResult::Changed(thin_vec!["A.2.i", "A.2.ii"]),
192+
"A.3" => ProcessResult::Changed(thin_vec![]),
191193
"A.2.i" | "A.2.ii" => ProcessResult::Unchanged,
192194
_ => unreachable!(),
193195
},
@@ -201,7 +203,7 @@ fn success_in_grandchildren() {
201203
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
202204
|obligation| match *obligation {
203205
"A.2.i" => ProcessResult::Unchanged,
204-
"A.2.ii" => ProcessResult::Changed(vec![]),
206+
"A.2.ii" => ProcessResult::Changed(thin_vec![]),
205207
_ => unreachable!(),
206208
},
207209
|_| {},
@@ -211,7 +213,7 @@ fn success_in_grandchildren() {
211213

212214
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
213215
|obligation| match *obligation {
214-
"A.2.i" => ProcessResult::Changed(vec!["A.2.i.a"]),
216+
"A.2.i" => ProcessResult::Changed(thin_vec!["A.2.i.a"]),
215217
"A.2.i.a" => ProcessResult::Unchanged,
216218
_ => unreachable!(),
217219
},
@@ -222,7 +224,7 @@ fn success_in_grandchildren() {
222224

223225
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
224226
|obligation| match *obligation {
225-
"A.2.i.a" => ProcessResult::Changed(vec![]),
227+
"A.2.i.a" => ProcessResult::Changed(thin_vec![]),
226228
_ => unreachable!(),
227229
},
228230
|_| {},
@@ -247,7 +249,7 @@ fn to_errors_no_throw() {
247249
forest.register_obligation("A");
248250
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
249251
|obligation| match *obligation {
250-
"A" => ProcessResult::Changed(vec!["A.1", "A.2", "A.3"]),
252+
"A" => ProcessResult::Changed(thin_vec!["A.1", "A.2", "A.3"]),
251253
"A.1" | "A.2" | "A.3" => ProcessResult::Unchanged,
252254
_ => unreachable!(),
253255
},
@@ -269,7 +271,7 @@ fn diamond() {
269271
forest.register_obligation("A");
270272
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
271273
|obligation| match *obligation {
272-
"A" => ProcessResult::Changed(vec!["A.1", "A.2"]),
274+
"A" => ProcessResult::Changed(thin_vec!["A.1", "A.2"]),
273275
"A.1" | "A.2" => ProcessResult::Unchanged,
274276
_ => unreachable!(),
275277
},
@@ -280,8 +282,8 @@ fn diamond() {
280282

281283
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
282284
|obligation| match *obligation {
283-
"A.1" => ProcessResult::Changed(vec!["D"]),
284-
"A.2" => ProcessResult::Changed(vec!["D"]),
285+
"A.1" => ProcessResult::Changed(thin_vec!["D"]),
286+
"A.2" => ProcessResult::Changed(thin_vec!["D"]),
285287
"D" => ProcessResult::Unchanged,
286288
_ => unreachable!(),
287289
},
@@ -295,7 +297,7 @@ fn diamond() {
295297
|obligation| match *obligation {
296298
"D" => {
297299
d_count += 1;
298-
ProcessResult::Changed(vec![])
300+
ProcessResult::Changed(thin_vec![])
299301
}
300302
_ => unreachable!(),
301303
},
@@ -313,7 +315,7 @@ fn diamond() {
313315
forest.register_obligation("A'");
314316
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
315317
|obligation| match *obligation {
316-
"A'" => ProcessResult::Changed(vec!["A'.1", "A'.2"]),
318+
"A'" => ProcessResult::Changed(thin_vec!["A'.1", "A'.2"]),
317319
"A'.1" | "A'.2" => ProcessResult::Unchanged,
318320
_ => unreachable!(),
319321
},
@@ -324,8 +326,8 @@ fn diamond() {
324326

325327
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
326328
|obligation| match *obligation {
327-
"A'.1" => ProcessResult::Changed(vec!["D'", "A'"]),
328-
"A'.2" => ProcessResult::Changed(vec!["D'"]),
329+
"A'.1" => ProcessResult::Changed(thin_vec!["D'", "A'"]),
330+
"A'.2" => ProcessResult::Changed(thin_vec!["D'"]),
329331
"D'" | "A'" => ProcessResult::Unchanged,
330332
_ => unreachable!(),
331333
},
@@ -366,7 +368,7 @@ fn done_dependency() {
366368

367369
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
368370
|obligation| match *obligation {
369-
"A: Sized" | "B: Sized" | "C: Sized" => ProcessResult::Changed(vec![]),
371+
"A: Sized" | "B: Sized" | "C: Sized" => ProcessResult::Changed(thin_vec![]),
370372
_ => unreachable!(),
371373
},
372374
|_| {},
@@ -379,7 +381,9 @@ fn done_dependency() {
379381
forest.register_obligation("(A,B,C): Sized");
380382
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
381383
|obligation| match *obligation {
382-
"(A,B,C): Sized" => ProcessResult::Changed(vec!["A: Sized", "B: Sized", "C: Sized"]),
384+
"(A,B,C): Sized" => {
385+
ProcessResult::Changed(thin_vec!["A: Sized", "B: Sized", "C: Sized"])
386+
}
383387
_ => unreachable!(),
384388
},
385389
|_| {},
@@ -399,10 +403,10 @@ fn orphan() {
399403

400404
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
401405
|obligation| match *obligation {
402-
"A" => ProcessResult::Changed(vec!["D", "E"]),
406+
"A" => ProcessResult::Changed(thin_vec!["D", "E"]),
403407
"B" => ProcessResult::Unchanged,
404-
"C1" => ProcessResult::Changed(vec![]),
405-
"C2" => ProcessResult::Changed(vec![]),
408+
"C1" => ProcessResult::Changed(thin_vec![]),
409+
"C2" => ProcessResult::Changed(thin_vec![]),
406410
"D" | "E" => ProcessResult::Unchanged,
407411
_ => unreachable!(),
408412
},
@@ -416,7 +420,7 @@ fn orphan() {
416420
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
417421
|obligation| match *obligation {
418422
"D" | "E" => ProcessResult::Unchanged,
419-
"B" => ProcessResult::Changed(vec!["D"]),
423+
"B" => ProcessResult::Changed(thin_vec!["D"]),
420424
_ => unreachable!(),
421425
},
422426
|_| {},
@@ -459,7 +463,7 @@ fn simultaneous_register_and_error() {
459463
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
460464
|obligation| match *obligation {
461465
"A" => ProcessResult::Error("An error"),
462-
"B" => ProcessResult::Changed(vec!["A"]),
466+
"B" => ProcessResult::Changed(thin_vec!["A"]),
463467
_ => unreachable!(),
464468
},
465469
|_| {},
@@ -474,7 +478,7 @@ fn simultaneous_register_and_error() {
474478
let TestOutcome { completed: ok, errors: err, .. } = forest.process_obligations(&mut C(
475479
|obligation| match *obligation {
476480
"A" => ProcessResult::Error("An error"),
477-
"B" => ProcessResult::Changed(vec!["A"]),
481+
"B" => ProcessResult::Changed(thin_vec!["A"]),
478482
_ => unreachable!(),
479483
},
480484
|_| {},

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