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A trait's local impls are trivially coherent if there are no impls. #120834

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merged 1 commit into from
Feb 12, 2024
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A trait's local impls are trivially coherent if there are no impls. #120834

merged 1 commit into from
Feb 12, 2024

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oli-obk
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@oli-obk oli-obk commented Feb 9, 2024

This avoids creating a dependency edge on the hir or the specialization graph

This may resolve part of the performance issue of #120558

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r? @lcnr

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@rustbot rustbot added the S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. label Feb 9, 2024
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oli-obk commented Feb 9, 2024

@bors try @rust-timer queue

@rustbot rustbot added the T-compiler Relevant to the compiler team, which will review and decide on the PR/issue. label Feb 9, 2024
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@rustbot rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Feb 9, 2024
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bors commented Feb 9, 2024

⌛ Trying commit 0727f9a with merge 7c63899...

bors added a commit to rust-lang-ci/rust that referenced this pull request Feb 9, 2024
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Auto merge of rust-lang#120834 - oli-obk:only_local_coherence, r=<try>
7c63899 
A trait's local impls are trivially coherent if there are no impls.

This avoids creating a dependency edge on the hir or the specialization graph

This may resolve part of the performance issue of rust-lang#120558
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unfortunate if this is necessary for perf

r=me after perf + comment

compiler/rustc_hir_analysis/src/coherence/mod.rs
@@ -120,11 +120,11 @@ pub fn provide(providers: &mut Providers) {
}

fn coherent_trait(tcx: TyCtxt<'_>, def_id: DefId) -> Result<(), ErrorGuaranteed> {
let Some(impls) = tcx.all_local_trait_impls(()).get(&def_id) else { return Ok(()) };
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please explain why we early return here and why this is sound

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A trait's local impls are trivially coherent if there are no impls.
e2349ea 
This avoids creating a dependency edge on the hir or the specialization graph
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oli-obk commented Feb 9, 2024

unfortunate if this is necessary for perf

I think the change is good by itself. Avoiding directly accessing the HIR except in the error paths is always an improvement for incremental.

@oli-obk oli-obk mentioned this pull request Feb 9, 2024
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lcnr commented Feb 9, 2024

I think the change is good by itself. Avoiding directly accessing the HIR except in the error paths is always an improvement for incremental.

for perf/incremental yes, but it does add complexity :< i would not add this special-case to a formalization of rust :p

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oli-obk commented Feb 9, 2024

it does add complexity

the order of operations should not matter in a formalization.

We could probably just move the specialization graph query call out of the coherent_trait query and invoke it in parallel instead.

bors added a commit to rust-lang-ci/rust that referenced this pull request Feb 9, 2024
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Auto merge of rust-lang#120835 - oli-obk:no_hir_coherence, r=<try>
83055d7 
Avoid accessing the HIR in the happy path of `coherent_trait`

based on rust-lang#120834

This may resolve part of the performance issue of rust-lang#120558
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bors commented Feb 9, 2024

☀️ Try build successful - checks-actions
Build commit: 7c63899 (7c638996380cc1b1285e6d37b124cce4e771e721)

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Finished benchmarking commit (7c63899): comparison URL.

Overall result: ✅ improvements - 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
Improvements ✅
(primary)		 -0.5% [-1.0%, -0.2%] 12
Improvements ✅
(secondary)		 -1.4% [-3.9%, -0.3%] 46
All ❌✅ (primary) -0.5% [-1.0%, -0.2%] 12

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)		 -6.0% [-14.5%, -0.9%] 3
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) -6.0% [-14.5%, -0.9%] 3

Cycles

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)		 - - 0
Improvements ✅
(secondary)		 -2.7% [-4.7%, -2.1%] 8
All ❌✅ (primary) - - 0

Binary size

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

Bootstrap: 661.327s -> 662.269s (0.14%)
Artifact size: 308.28 MiB -> 308.25 MiB (-0.01%)

@rustbot rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Feb 9, 2024
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oli-obk commented Feb 9, 2024

@bors r=lcnr

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bors commented Feb 9, 2024

📌 Commit 0727f9a has been approved by lcnr

It is now in the queue for this repository.

@bors 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 Feb 9, 2024
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oli-obk commented Feb 9, 2024

@bors r- I only pushed the new comment on the other PR and forgot it here

@bors bors added S-waiting-on-author Status: This is awaiting some action (such as code changes or more information) from the author. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Feb 9, 2024
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oli-obk commented Feb 9, 2024

@bors r=lcnr

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bors commented Feb 9, 2024

📌 Commit e2349ea has been approved by lcnr

It is now in the queue for this repository.

@bors 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-author Status: This is awaiting some action (such as code changes or more information) from the author. labels Feb 9, 2024
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bors commented Feb 12, 2024

⌛ Testing commit e2349ea with merge de4d615...

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bors commented Feb 12, 2024

☀️ Test successful - checks-actions
Approved by: lcnr
Pushing de4d615 to master...

@bors bors added the merged-by-bors This PR was explicitly merged by bors. label Feb 12, 2024
@bors bors merged commit de4d615 into rust-lang:master Feb 12, 2024
12 checks passed
@rustbot rustbot added this to the 1.78.0 milestone Feb 12, 2024
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Finished benchmarking commit (de4d615): comparison URL.

Overall result: ✅ improvements - 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
Improvements ✅
(primary)		 -0.4% [-1.0%, -0.2%] 10
Improvements ✅
(secondary)		 -1.4% [-3.5%, -0.3%] 24
All ❌✅ (primary) -0.4% [-1.0%, -0.2%] 10

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)		 -3.2% [-3.3%, -3.1%] 2
Improvements ✅
(secondary)		 - - 0
All ❌✅ (primary) -3.2% [-3.3%, -3.1%] 2

Cycles

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)		 5.1% [5.1%, 5.2%] 3
Improvements ✅
(primary)		 - - 0
Improvements ✅
(secondary)		 -2.9% [-4.7%, -2.1%] 8
All ❌✅ (primary) - - 0

Binary size

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

Bootstrap: 664.268s -> 663.665s (-0.09%)
Artifact size: 308.43 MiB -> 308.44 MiB (0.00%)

@oli-obk oli-obk deleted the only_local_coherence branch February 12, 2024 10:31
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