Split `SelectionContext::select` into fns that take a binder and don't #113308

compiler-errors · 2023-07-04T01:56:26Z

most usages of SelectionContext::select don't need to use a binder, but wrap them in a dummy because of the signature. Let's split this out into SelectionContext::{select,poly_select} and limit the usages of the latter.

Right now, we only have 3 places where we're calling poly_select -- fulfillment, internally within the old solver, and the auto-trait finder.

r? @lcnr

rustbot · 2023-07-04T01:56:34Z

Some changes occurred to the core trait solver

cc @rust-lang/initiative-trait-system-refactor

compiler-errors · 2023-07-04T01:58:03Z

compiler/rustc_hir_typeck/src/coercion.rs

-            let bound_predicate = obligation.predicate.kind();
-            let trait_pred = match bound_predicate.skip_binder() {
-                ty::PredicateKind::Clause(ty::ClauseKind::Trait(trait_pred))
+            let trait_pred = match obligation.predicate.kind().no_bound_vars() {


This could technically affect inference, but CoerceUnsized is an unstable trait and I don't know of a stdlib impl that emits bound predicates :^)

bors · 2023-07-05T19:37:21Z

☔ The latest upstream changes (presumably #113370) made this pull request unmergeable. Please resolve the merge conflicts.

lcnr

some nits, then r=me

lcnr · 2023-07-06T11:16:01Z

compiler/rustc_trait_selection/src/traits/auto_trait.rs

@@ -292,7 +292,7 @@ impl<'tcx> AutoTraitFinder<'tcx> {
                new_env,
                pred,
            ));
-            let result = select.select(&obligation);
+            let result = select.poly_select(&obligation);


feels like we may end up with with placeholders in the environment/output here, so it might be safer to check for no_bound_vars. Doesn't matter much, this keeps the current behavior and we're going to rewrite this code anyways

lcnr · 2023-07-06T11:18:11Z

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -123,8 +124,8 @@ pub struct SelectionContext<'cx, 'tcx> {
 }

 // A stack that walks back up the stack frame.
-struct TraitObligationStack<'prev, 'tcx> {
-    obligation: &'prev TraitObligation<'tcx>,
+struct PolyTraitObligationStack<'prev, 'tcx> {


i think we should keep this as TraitObligationStack, the Poly doesn't add any meaningful info imo and makes the code harder to read imo

No this is just because I was stupid and used ctrl+f to replace names, and I didn't see this was edited too 🤦

lcnr · 2023-07-06T11:18:53Z

compiler/rustc_trait_selection/src/traits/select/mod.rs

@@ -2946,21 +2962,23 @@ impl<'tcx> ProvisionalEvaluationCache<'tcx> {
 }

 #[derive(Copy, Clone)]
-struct TraitObligationStackList<'o, 'tcx> {
+struct PolyTraitObligationStackList<'o, 'tcx> {


Suggested change

struct PolyTraitObligationStackList<'o, 'tcx> {

struct TraitObligationStackList<'o, 'tcx> {

lcnr · 2023-07-06T11:19:39Z

also, please run perf after rebasing, I think that not having a Binder in codegen_select_obligation might impact perf

compiler-errors · 2023-07-06T16:50:36Z

@bors try @rust-timer queue

bors · 2023-07-06T16:50:44Z

⌛ Trying commit 3f8919c with merge 5d2ae64c182026baa066c3144d019b08883a6cbf...

bors · 2023-07-06T18:08:08Z

☀️ Try build successful - checks-actions
Build commit: 5d2ae64c182026baa066c3144d019b08883a6cbf (5d2ae64c182026baa066c3144d019b08883a6cbf)

rust-timer · 2023-07-06T21:48:29Z

Finished benchmarking commit (5d2ae64c182026baa066c3144d019b08883a6cbf): comparison URL.

Overall result: ❌ regressions - no action needed

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. While you can manually mark this PR as fit for rollup, we strongly recommend not doing so since this PR may lead to changes in compiler perf.

@bors rollup=never
@rustbot label: -S-waiting-on-perf -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.8%	[0.7%, 1.0%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	0.5%	[0.5%, 0.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.2%	[-2.2%, -2.2%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.9%	[-2.2%, 0.5%]	2

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 657.995s -> 658.303s (0.05%)

compiler-errors · 2023-07-06T22:14:25Z

I'm pretty certain that's noise, given it affects doc and check on two random crates.

compiler-errors · 2023-07-07T05:33:22Z

@bors r=lcnr

bors · 2023-07-07T05:33:23Z

📌 Commit 3f8919c has been approved by lcnr

It is now in the queue for this repository.

bors · 2023-07-07T10:32:46Z

⌛ Testing commit 3f8919c with merge 1a449dc...

bors · 2023-07-07T13:15:05Z

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing 1a449dc to master...

rust-timer · 2023-07-07T14:33:07Z

Finished benchmarking commit (1a449dc): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.7%	[0.7%, 0.8%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-1.8%	[-1.8%, -1.8%]	1
Improvements ✅ (secondary)	-3.6%	[-3.6%, -3.6%]	1
All ❌✅ (primary)	-1.8%	[-1.8%, -1.8%]	1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 658.878s -> 657.277s (-0.24%)

rustbot assigned lcnr Jul 4, 2023

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. WG-trait-system-refactor The Rustc Trait System Refactor Initiative (-Znext-solver) labels Jul 4, 2023

compiler-errors commented Jul 4, 2023

View reviewed changes

lcnr reviewed Jul 6, 2023

View reviewed changes

compiler-errors added 4 commits July 6, 2023 16:30

TraitObligation -> PolyTraitObligation

3645345

Separate select calls that don't need a binder

52f7384

Coercion doesn't need binders either

018c3e2

get rid of a bit more calls to poly_select

3f8919c

rust-cloud-vms bot force-pushed the poly-select branch from d9d1cf2 to 3f8919c Compare July 6, 2023 16:50

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 6, 2023

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jul 6, 2023

bors added S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Jul 7, 2023

bors added the merged-by-bors This PR was explicitly merged by bors. label Jul 7, 2023

bors merged commit 1a449dc into rust-lang:master Jul 7, 2023

rustbot added this to the 1.72.0 milestone Jul 7, 2023

compiler-errors deleted the poly-select branch August 11, 2023 20:13

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Split `SelectionContext::select` into fns that take a binder and don't #113308

Split `SelectionContext::select` into fns that take a binder and don't #113308

compiler-errors commented Jul 4, 2023

rustbot commented Jul 4, 2023

compiler-errors Jul 4, 2023

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lcnr Jul 6, 2023

lcnr Jul 6, 2023

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lcnr Jul 6, 2023

lcnr commented Jul 6, 2023 •

edited

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bors commented Jul 7, 2023

rust-timer commented Jul 7, 2023

	struct PolyTraitObligationStackList<'o, 'tcx> {
	struct TraitObligationStackList<'o, 'tcx> {

Split SelectionContext::select into fns that take a binder and don't #113308

Split SelectionContext::select into fns that take a binder and don't #113308

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lcnr commented Jul 6, 2023 • edited Loading

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rust-timer commented Jul 6, 2023

Overall result: ❌ regressions - no action needed

compiler-errors commented Jul 6, 2023

compiler-errors commented Jul 7, 2023

bors commented Jul 7, 2023

bors commented Jul 7, 2023

bors commented Jul 7, 2023

rust-timer commented Jul 7, 2023

Overall result: ❌ regressions - no action needed

Split `SelectionContext::select` into fns that take a binder and don't #113308

Split `SelectionContext::select` into fns that take a binder and don't #113308

lcnr commented Jul 6, 2023 •

edited

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