Add a precondition check for Layout::from_size_align_unchecked #126556

saethlin · 2024-06-16T17:15:53Z

Ran into this while looking into rust-lang/miri#3679. This is of course not the cause of the ICE, but the reproducer doesn't encounter a precondition check and it ought to.

rustbot · 2024-06-16T17:16:01Z

r? @joboet

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joboet · 2024-06-16T17:23:00Z

Good idea! This code is highly perf-sensitive though, so let's see what the impact of the extra MIR is.
@bors try @rust-timer

Add a precondition check for Layout::from_size_align_unchecked Ran into this while looking into rust-lang/miri#3679. This is of course not the cause of the ICE, but the reproducer doesn't encounter a precondition check and it ought to.

bors · 2024-06-16T17:24:12Z

⌛ Trying commit 289a208 with merge 5489321...

bors · 2024-06-16T19:06:49Z

☀️ Try build successful - checks-actions
Build commit: 5489321 (5489321f47676a047199924cde6fecca98ff983f)

saethlin · 2024-06-17T16:01:57Z

@rust-timer build 5489321

rust-timer · 2024-06-17T17:58:54Z

Finished benchmarking commit (5489321): comparison URL.

Overall result: ❌ regressions - 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)	0.8%	[0.2%, 3.3%]	15
Regressions ❌ (secondary)	3.1%	[0.6%, 8.0%]	15
Improvements ✅ (primary)	-0.9%	[-0.9%, -0.9%]	1
Improvements ✅ (secondary)	-1.1%	[-1.1%, -1.1%]	2
All ❌✅ (primary)	0.7%	[-0.9%, 3.3%]	16

Max RSS (memory usage)

Results (primary 0.1%, secondary 3.6%)

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)	5.8%	[1.7%, 11.6%]	3
Regressions ❌ (secondary)	3.6%	[3.2%, 4.1%]	2
Improvements ✅ (primary)	-5.6%	[-9.8%, -2.4%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[-9.8%, 11.6%]	6

Cycles

Results (primary 1.3%, secondary 4.1%)

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%	[0.7%, 2.9%]	6
Regressions ❌ (secondary)	4.1%	[1.7%, 5.5%]	8
Improvements ✅ (primary)	-1.1%	[-1.1%, -1.1%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.3%	[-1.1%, 2.9%]	7

Binary size

Results (primary 0.4%, secondary 1.0%)

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%	[0.0%, 2.1%]	100
Regressions ❌ (secondary)	1.8%	[0.0%, 3.5%]	23
Improvements ✅ (primary)	-0.1%	[-0.3%, -0.0%]	5
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	19
All ❌✅ (primary)	0.4%	[-0.3%, 2.1%]	105

Bootstrap: 671.558s -> 674.994s (0.51%)
Artifact size: 319.87 MiB -> 320.49 MiB (0.19%)

saethlin · 2024-06-18T18:29:16Z

I see. We're playing this game again.

saethlin · 2024-06-18T18:30:09Z

I'm going to do some experiments, some of these commits might be janky.

saethlin · 2024-06-18T18:30:42Z

@bors try @rust-timer queue

Add a precondition check for Layout::from_size_align_unchecked Ran into this while looking into rust-lang/miri#3679. This is of course not the cause of the ICE, but the reproducer doesn't encounter a precondition check and it ought to.

bors · 2024-06-18T18:31:54Z

⌛ Trying commit 31f0305 with merge 214e98d...

bors · 2024-06-18T20:09:59Z

☀️ Try build successful - checks-actions
Build commit: 214e98d (214e98d564decf0f0a17b0b2f6c0255e6218037c)

rust-timer · 2024-06-18T22:46:35Z

Finished benchmarking commit (214e98d): 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)	0.8%	[0.2%, 4.1%]	43
Regressions ❌ (secondary)	1.8%	[0.4%, 5.8%]	30
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.2%]	8
All ❌✅ (primary)	0.8%	[0.2%, 4.1%]	43

Max RSS (memory usage)

Results (primary -0.3%)

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)	5.4%	[1.5%, 10.6%]	4
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-4.2%	[-9.2%, -1.5%]	6
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.3%	[-9.2%, 10.6%]	10

Cycles

Results (primary 1.5%, secondary 4.4%)

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%	[0.8%, 3.8%]	17
Regressions ❌ (secondary)	4.4%	[1.9%, 6.4%]	9
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[0.8%, 3.8%]	17

Binary size

Results (primary 0.5%, secondary 1.8%)

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%	[0.1%, 2.1%]	101
Regressions ❌ (secondary)	1.9%	[0.1%, 3.5%]	23
Improvements ✅ (primary)	-0.2%	[-0.2%, -0.2%]	1
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	1
All ❌✅ (primary)	0.5%	[-0.2%, 2.1%]	102

Bootstrap: 671.639s -> 678.312s (0.99%)
Artifact size: 320.44 MiB -> 320.48 MiB (0.01%)

saethlin · 2024-06-20T19:25:03Z

@bors try @rust-timer queue

Add a precondition check for Layout::from_size_align_unchecked Ran into this while looking into rust-lang/miri#3679. This is of course not the cause of the ICE, but the reproducer doesn't encounter a precondition check and it ought to.

bors · 2024-06-20T19:26:15Z

⌛ Trying commit 44b1911 with merge 41d5c9c...

saethlin · 2024-08-20T22:31:02Z

Alignment::new_unchecked which calls is_power_of_two again

That is not true. The precondition check in Alignment::new_unchecked is cfg'd out. The function is just a transmute wrapper in the distributed standard library.

saethlin · 2024-08-20T22:40:17Z

To be quite clear: The only instantiation that this PR adds is a tiny wrapper function. That's why it looks bad in instruction-counting micro-benchmarks. I do not think it is worth my or your time to pursue improvement on the above perf report. Adding debug checks regresses build times of tiny programs and I don't think that should be surprising to anyone.

I will continue to poke at this to mollify my reviewer, but that is all.

saethlin · 2024-08-20T23:36:02Z

@bors try @rust-timer queue

Add a precondition check for Layout::from_size_align_unchecked Ran into this while looking into rust-lang/miri#3679. This is of course not the cause of the ICE, but the reproducer doesn't encounter a precondition check and it ought to.

bors · 2024-08-20T23:37:14Z

⌛ Trying commit e6b0f27 with merge 3d3f494...

bors · 2024-08-21T01:31:41Z

☀️ Try build successful - checks-actions
Build commit: 3d3f494 (3d3f49427c053690236c373fbb409ebe69fd19c9)

rust-timer · 2024-08-21T03:08:34Z

Finished benchmarking commit (3d3f494): 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
Regressions ❌ (secondary)	1.4%	[1.2%, 1.7%]	3
Improvements ✅ (primary)	-0.3%	[-0.3%, -0.2%]	6
Improvements ✅ (secondary)	-0.2%	[-0.2%, -0.2%]	3
All ❌✅ (primary)	-0.3%	[-0.3%, -0.2%]	6

Max RSS (memory usage)

Results (primary -1.5%, secondary 2.4%)

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)	3.3%	[1.9%, 4.7%]	2
Regressions ❌ (secondary)	2.4%	[1.5%, 3.6%]	3
Improvements ✅ (primary)	-4.7%	[-6.5%, -1.4%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-1.5%	[-6.5%, 4.7%]	5

Cycles

Results (primary -0.9%, secondary 1.8%)

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)	1.8%	[1.8%, 1.8%]	1
Improvements ✅ (primary)	-0.9%	[-1.0%, -0.8%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.9%	[-1.0%, -0.8%]	2

Binary size

Results (primary 0.1%, secondary 0.6%)

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%, 0.5%]	50
Regressions ❌ (secondary)	0.6%	[0.2%, 1.0%]	18
Improvements ✅ (primary)	-0.1%	[-0.2%, -0.0%]	7
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.1%	[-0.2%, 0.5%]	57

Bootstrap: 748.876s -> 748.849s (-0.00%)
Artifact size: 338.91 MiB -> 338.86 MiB (-0.02%)

joboet · 2024-08-21T11:00:39Z

Sorry, I got too carried away microoptimizing this... Anyway, this looks great! Thank you for your patience.
@bors r+

bors · 2024-08-21T11:00:42Z

📌 Commit e6b0f27 has been approved by joboet

It is now in the queue for this repository.

joboet · 2024-08-21T11:03:23Z

As for performance:

All the Layout code is highly performance-sensitive. The UB check is worth its cost, and we even golfed that down to a minimum.

@rustbot label +perf-regression-triaged

bors · 2024-08-21T12:50:08Z

⌛ Testing commit e6b0f27 with merge 982c6f8...

bors · 2024-08-21T15:29:26Z

☀️ Test successful - checks-actions
Approved by: joboet
Pushing 982c6f8 to master...

rust-timer · 2024-08-21T17:50:20Z

Finished benchmarking commit (982c6f8): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

Next Steps: If you can justify the regressions found in this perf run, please indicate this with @rustbot label: +perf-regression-triaged along with sufficient written justification. If you cannot justify the regressions please open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

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

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)	1.3%	[1.1%, 1.5%]	3
Improvements ✅ (primary)	-0.3%	[-0.5%, -0.2%]	9
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.3%	[-0.5%, -0.2%]	9

Max RSS (memory usage)

Results (primary 0.7%, secondary 2.3%)

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)	4.5%	[3.4%, 5.4%]	3
Regressions ❌ (secondary)	2.3%	[1.6%, 3.0%]	3
Improvements ✅ (primary)	-3.2%	[-4.1%, -2.7%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.7%	[-4.1%, 5.4%]	6

Cycles

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

Binary size

Results (primary 0.1%, secondary 0.6%)

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%, 0.4%]	44
Regressions ❌ (secondary)	0.6%	[0.2%, 1.0%]	18
Improvements ✅ (primary)	-0.2%	[-1.1%, -0.0%]	15
Improvements ✅ (secondary)	-0.0%	[-0.0%, -0.0%]	1
All ❌✅ (primary)	0.1%	[-1.1%, 0.4%]	59

Bootstrap: 750.629s -> 750.879s (0.03%)
Artifact size: 338.97 MiB -> 338.98 MiB (0.00%)

…try> Enable Alignment::new_unchecked precondition check Similar to what happened with rust-lang#126556, I think this has become palatable since rust-lang#126793. r? `@ghost`

…orkingjubilee Enable Alignment::new_unchecked precondition check Similar to what happened with rust-lang#126556, I think this has become palatable since rust-lang#126793.

…ilee Enable Alignment::new_unchecked precondition check Similar to what happened with rust-lang/rust#126556, I think this has become palatable since rust-lang/rust#126793.

rustbot assigned joboet Jun 16, 2024

rustbot added S-waiting-on-review Status: Awaiting review from the assignee but also interested parties. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Jun 16, 2024

rustbot added the perf-regression Performance regression. label Jun 17, 2024

saethlin marked this pull request as draft June 18, 2024 18:29

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saethlin force-pushed the layout-precondition branch from 31f0305 to 96bf871 Compare June 19, 2024 20:31

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rustbot added the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Jun 20, 2024

Try to golf down the amount of code in Layout

e6b0f27

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rustbot removed the S-waiting-on-perf Status: Waiting on a perf run to be completed. label Aug 21, 2024

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 Aug 21, 2024

rustbot added the perf-regression-triaged The performance regression has been triaged. label Aug 21, 2024

bors added the merged-by-bors This PR was explicitly merged by bors. label Aug 21, 2024

bors merged commit 982c6f8 into rust-lang:master Aug 21, 2024
7 checks passed

rustbot added this to the 1.82.0 milestone Aug 21, 2024

saethlin deleted the layout-precondition branch August 21, 2024 16:04

saethlin mentioned this pull request Aug 23, 2024

Enable Alignment::new_unchecked precondition check #129488

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Add a precondition check for Layout::from_size_align_unchecked #126556

Add a precondition check for Layout::from_size_align_unchecked #126556

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Add a precondition check for Layout::from_size_align_unchecked #126556

Add a precondition check for Layout::from_size_align_unchecked #126556

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Overall result: ❌ regressions - ACTION NEEDED

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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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Overall result: ❌✅ regressions and improvements - ACTION NEEDED