Create an `AllocId` for `ConstValue::Slice`. #116707

cjgillot · 2023-10-13T20:39:21Z

This PR modifies ConstValue::Slice to use an AllocId instead of directly manipulating the allocation. This was originally proposed by #115764 but was a perf regression.

Almost 2 years later, enough code has changed to make this a perf improvement: #116707 (comment)

cjgillot · 2023-10-13T20:39:40Z

@bors try @rust-timer queue

bors · 2023-10-13T20:40:49Z

⌛ Trying commit 334753f with merge 9ef21e1...

Create an `AllocId` for `ConstValue::Slice`. r? `@ghost`

bors · 2023-10-13T21:53:15Z

☀️ Try build successful - checks-actions
Build commit: 9ef21e1 (9ef21e1d83c6c9220b072fd1a4f225949514cc28)

RalfJung · 2023-10-13T22:02:01Z

How does this differ from the almost identical perf experiment I did a few weeks ago? Here are the perf results.

rust-timer · 2023-10-14T00:18:48Z

Finished benchmarking commit (9ef21e1): comparison URL.

Overall result: ❌✅ regressions and improvements - 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.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@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)	1.7%	[1.7%, 1.7%]	1
Regressions ❌ (secondary)	2.5%	[0.4%, 7.7%]	7
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.2%	[-1.3%, -1.0%]	3
All ❌✅ (primary)	1.7%	[1.7%, 1.7%]	1

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)	1.5%	[0.9%, 2.2%]	3
Regressions ❌ (secondary)	3.8%	[0.8%, 14.5%]	17
Improvements ✅ (primary)	-1.6%	[-1.6%, -1.6%]	1
Improvements ✅ (secondary)	-5.3%	[-10.2%, -0.9%]	16
All ❌✅ (primary)	0.7%	[-1.6%, 2.2%]	4

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)	7.0%	[2.1%, 21.5%]	14
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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)	0.1%	[0.0%, 0.3%]	30
Regressions ❌ (secondary)	0.0%	[0.0%, 0.1%]	9
Improvements ✅ (primary)	-0.0%	[-0.1%, -0.0%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[-0.1%, 0.3%]	33

Bootstrap: 628.692s -> 625.904s (-0.44%)
Artifact size: 271.29 MiB -> 271.29 MiB (0.00%)

cjgillot · 2023-10-14T10:26:37Z

No real difference. I just couldn't find your version.
Now there is one.

@bors try @rust-timer queue

bors · 2023-10-14T10:27:48Z

⌛ Trying commit e195fe8 with merge eafbd55...

Create an `AllocId` for `ConstValue::Slice`. r? `@ghost`

bors · 2023-10-14T11:40:41Z

☀️ Try build successful - checks-actions
Build commit: eafbd55 (eafbd55f7123e31b30c2f3224a91d6db75e48c3f)

rust-timer · 2023-10-14T21:03:51Z

Finished benchmarking commit (eafbd55): comparison URL.

Overall result: ❌✅ regressions and improvements - 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.

Next Steps: If you can justify the regressions found in this try perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please fix the regressions and do another perf run. If the next run shows neutral or positive results, the label will be automatically removed.

@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)	0.6%	[0.1%, 1.8%]	4
Regressions ❌ (secondary)	1.7%	[0.2%, 7.8%]	12
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.1%	[-1.2%, -1.0%]	3
All ❌✅ (primary)	0.6%	[0.1%, 1.8%]	4

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)	1.6%	[1.2%, 2.1%]	3
Regressions ❌ (secondary)	2.9%	[1.1%, 8.7%]	15
Improvements ✅ (primary)	-1.9%	[-3.3%, -0.5%]	2
Improvements ✅ (secondary)	-6.0%	[-9.9%, -1.0%]	19
All ❌✅ (primary)	0.2%	[-3.3%, 2.1%]	5

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)	8.0%	[2.6%, 13.7%]	4
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.5%	[-2.5%, -2.5%]	1
All ❌✅ (primary)	-	-	0

Binary size

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)	0.1%	[0.0%, 0.3%]	30
Regressions ❌ (secondary)	0.0%	[0.0%, 0.1%]	9
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.0%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[-0.1%, 0.3%]	33

Bootstrap: 627.527s -> 627.366s (-0.03%)
Artifact size: 271.26 MiB -> 271.31 MiB (0.02%)

cjgillot · 2025-07-13T13:17:13Z

@bors try @rust-timer queue

cjgillot · 2025-07-20T13:13:27Z

I did not manage to reproduce the test failure.

RalfJung · 2025-07-20T20:15:54Z

@bors2 try jobs=aarch64-apple

rust-bors · 2025-07-20T20:15:59Z

⌛ Trying commit b320a80 with merge d743e78…

To cancel the try build, run the command @bors2 try cancel.

Create an `AllocId` for `ConstValue::Slice`. This PR modifies `ConstValue::Slice` to use an `AllocId` instead of directly manipulating the allocation. This was originally proposed by #115764 but was a perf regression. Almost 2 years later, enough code has changed to make this a perf improvement: #116707 (comment) try-job: aarch64-apple

rust-bors · 2025-07-20T21:02:23Z

💔 Test failed

CI ❌

RalfJung · 2025-07-20T21:06:17Z

Seems like it reproduces on CI though, so something will have to be done.

These are crash tests. And apparently your PR fixes the crash?

RalfJung · 2025-07-20T21:40:52Z

This trivially reproduces for me with ./x test crashes.

cjgillot · 2025-07-24T02:38:29Z

Both failing ICEs have been fixed by #144233, so the CI failure should be gone.

@bors r=oli-obk,RalfJung

bors · 2025-07-24T02:38:31Z

📌 Commit 967ba2f has been approved by oli-obk,RalfJung

It is now in the queue for this repository.

bors · 2025-07-24T03:35:51Z

⌛ Testing commit 967ba2f with merge 3c30dbb...

bors · 2025-07-24T06:57:01Z

☀️ Test successful - checks-actions
Approved by: oli-obk,RalfJung
Pushing 3c30dbb to master...

github-actions · 2025-07-24T07:00:46Z

What is this?

This is an experimental post-merge analysis report that shows differences in test outcomes between the merged PR and its parent PR.

Comparing efd420c (parent) -> 3c30dbb (this PR)

Test differences

Show 10 test diffs

10 doctest diffs were found. These are ignored, as they are noisy.

Test dashboard

Run

cargo run --manifest-path src/ci/citool/Cargo.toml -- \
    test-dashboard 3c30dbbe31bfbf6029f4534170165ba573ff0fd1 --output-dir test-dashboard

And then open test-dashboard/index.html in your browser to see an overview of all executed tests.

Job duration changes

x86_64-apple-2: 4145.6s -> 5546.3s (33.8%)
dist-aarch64-linux: 8295.5s -> 5899.8s (-28.9%)
pr-check-2: 2097.6s -> 2671.2s (27.3%)
dist-x86_64-apple: 8978.6s -> 11237.3s (25.2%)
dist-apple-various: 6670.3s -> 5640.3s (-15.4%)
i686-gnu-1: 7268.7s -> 8189.3s (12.7%)
x86_64-rust-for-linux: 2588.1s -> 2915.1s (12.6%)
i686-gnu-nopt-1: 7174.2s -> 8073.0s (12.5%)
aarch64-gnu-llvm-19-1: 3977.3s -> 3498.8s (-12.0%)
x86_64-gnu-llvm-20-1: 3239.3s -> 3620.8s (11.8%)

How to interpret the job duration changes?

Job durations can vary a lot, based on the actual runner instance
that executed the job, system noise, invalidated caches, etc. The table above is provided
mostly for t-infra members, for simpler debugging of potential CI slow-downs.

rust-timer · 2025-07-24T08:07:07Z

Finished benchmarking commit (3c30dbb): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

If the regression was expected or you think it can be justified,
please write a comment with sufficient written justification, and add
@rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
If you think that you know of a way to resolve the regression, try to create
a new PR with a fix for the regression.
If you do not understand the regression or you think that it is just noise,
you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
were already notified of this PR).

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.7%	[0.2%, 1.0%]	6
Regressions ❌ (secondary)	0.3%	[0.0%, 0.9%]	38
Improvements ✅ (primary)	-0.3%	[-0.6%, -0.1%]	17
Improvements ✅ (secondary)	-1.9%	[-10.2%, -0.0%]	56
All ❌✅ (primary)	-0.1%	[-0.6%, 1.0%]	23

Max RSS (memory usage)

Results (primary 1.9%, secondary -4.0%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	1.9%	[0.8%, 4.5%]	4
Regressions ❌ (secondary)	4.0%	[1.1%, 8.2%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-5.6%	[-11.3%, -1.0%]	30
All ❌✅ (primary)	1.9%	[0.8%, 4.5%]	4

Cycles

Results (secondary -7.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	4.7%	[2.9%, 7.8%]	6
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-12.1%	[-16.8%, -3.8%]	17
All ❌✅ (primary)	-	-	0

Binary size

Results (primary -0.1%, secondary 0.0%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	0.0%	[0.0%, 0.0%]	4
Regressions ❌ (secondary)	0.1%	[0.0%, 0.2%]	15
Improvements ✅ (primary)	-0.1%	[-0.1%, -0.0%]	52
Improvements ✅ (secondary)	-0.0%	[-0.1%, -0.0%]	17
All ❌✅ (primary)	-0.1%	[-0.1%, 0.0%]	56

Bootstrap: 468.582s -> 468.586s (0.00%)
Artifact size: 374.67 MiB -> 374.68 MiB (0.00%)

Create an `AllocId` for `ConstValue::Slice`. This PR modifies `ConstValue::Slice` to use an `AllocId` instead of directly manipulating the allocation. This was originally proposed by rust-lang/rust#115764 but was a perf regression. Almost 2 years later, enough code has changed to make this a perf improvement: rust-lang/rust#116707 (comment)

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. labels Oct 13, 2023

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bors added a commit to rust-lang-ci/rust that referenced this pull request Oct 13, 2023

Auto merge of rust-lang#116707 - cjgillot:slice-id, r=<try>

9ef21e1

Create an `AllocId` for `ConstValue::Slice`. r? `@ghost`

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rustbot added perf-regression Performance regression. and removed S-waiting-on-perf Status: Waiting on a perf run to be completed. labels Oct 14, 2023

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bors added a commit to rust-lang-ci/rust that referenced this pull request Oct 14, 2023

Auto merge of rust-lang#116707 - cjgillot:slice-id, r=<try>

eafbd55

Create an `AllocId` for `ConstValue::Slice`. r? `@ghost`

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Dylan-DPC added S-experimental Status: Ongoing experiment that does not require reviewing and won't be merged in its current state. and removed S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. labels Feb 16, 2024

cjgillot force-pushed the slice-id branch from e195fe8 to 766af91 Compare April 7, 2024 15:01

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cjgillot force-pushed the slice-id branch from 766af91 to 47bdbd3 Compare July 13, 2025 13:06

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bors added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. and removed S-waiting-on-bors Status: Waiting on bors to run and complete tests. Bors will change the label on completion. labels Jul 18, 2025

cjgillot force-pushed the slice-id branch from 2bab5bf to b320a80 Compare July 20, 2025 13:13

cjgillot added 3 commits July 23, 2025 23:54

Give an AllocId to ConstValue::Slice.

9ff0712

Remove useless lifetime parameter.

0460c92

Remove const deduplication from the interpreter.

967ba2f

cjgillot force-pushed the slice-id branch from b320a80 to 967ba2f Compare July 23, 2025 23:55

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 24, 2025

bors added the merged-by-bors This PR was explicitly merged by bors. label Jul 24, 2025

bors merged commit 3c30dbb into rust-lang:master Jul 24, 2025
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bors mentioned this pull request Jul 24, 2025

Remove fewer Storage calls in CopyProp and GVN #142531

Open

rustbot added the perf-regression Performance regression. label Jul 24, 2025

bors mentioned this pull request Jul 24, 2025

[WIP] Add downcast_trait and downcast_trait_mut #144363

Draft

cjgillot deleted the slice-id branch July 24, 2025 10:24

Create an AllocId for ConstValue::Slice. #116707

Create an AllocId for ConstValue::Slice. #116707

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Overall result: ❌✅ regressions and improvements - ACTION NEEDED

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Overall result: ❌✅ regressions and improvements - ACTION NEEDED

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Test differences

Job duration changes

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Overall result: ❌✅ regressions and improvements - please read the text below

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Create an `AllocId` for `ConstValue::Slice`. #116707

Create an `AllocId` for `ConstValue::Slice`. #116707

cjgillot commented Oct 13, 2023 •

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