Let codegen decide when to `mem::swap` with immediates #122582

scottmcm · 2024-03-16T05:14:09Z

Making libcore decide this is silly; the backend has so much better information about when it's a good idea.

Thus this PR introduces a new typed_swap intrinsic with a fallback body, and replaces that fallback implementation when swapping immediates or scalar pairs.

r? oli-obk

Replaces #111744, and means we'll never need more libs PRs like #111803 or #107140

src/tools/miri/tests/fail/intrinsics/typed-swap-invalid-array.rs

rustbot · 2024-03-16T09:23:10Z

Some changes occurred to the CTFE / Miri engine

cc @rust-lang/miri

The Miri subtree was changed

cc @rust-lang/miri

library/core/src/mem/mod.rs

scottmcm · 2024-03-16T19:07:29Z

@bors try @rust-timer queue

Let codegen decide when to `mem::swap` with immediates Making `libcore` decide this is silly; the backend has so much better information about when it's a good idea. Thus this PR introduces a new `typed_swap` intrinsic with a fallback body, and replaces that fallback implementation when swapping immediates or scalar pairs. r? oli-obk Replaces rust-lang#111744, and means we'll never need more libs PRs like rust-lang#111803 or rust-lang#107140

bors · 2024-03-16T19:08:39Z

⌛ Trying commit e583c57 with merge 3f68c63...

bors · 2024-03-16T20:40:43Z

☀️ Try build successful - checks-actions
Build commit: 3f68c63 (3f68c63f114f4d57b01ae74bc549e4b68f955eee)

library/core/src/ptr/mod.rs

RalfJung · 2024-03-17T08:41:22Z

library/core/src/ptr/mod.rs

@@ -954,6 +954,23 @@ pub const unsafe fn swap<T>(x: *mut T, y: *mut T) {
    }
 }

+/// Non-overlapping *typed* swap of a single value.


Should it be called typed_swap_nonoverlapping?

I went back and forth multiple times on this. typed_swap_nonoverlapping sounds to me like ptr::swap_nonoverlapping, just typed. So that would make this typed_swap_nonoverlapping_one or something, and now that's just seeming really long.

So since it's internal, I think I'm inclined to leave it as-is for now unless someone feels particularly strongly about it.

I feel like the "nonoverlapping" distinction is way more fundamental than the "one" distinction. And since it is internal, consistency with ptr::swap_nonoverlapping isn't very important IMO.

library/core/src/mem/mod.rs

compiler/rustc_const_eval/src/interpret/intrinsics.rs

src/tools/miri/tests/fail/intrinsics/typed-swap-invalid-array.rs

bors · 2024-03-23T05:34:58Z

💔 Test failed - checks-actions

scottmcm · 2024-03-23T07:23:48Z

@bors r=oli-obk

bors · 2024-03-23T07:23:50Z

📌 Commit 75d2e5b has been approved by oli-obk

It is now in the queue for this repository.

bors · 2024-03-23T09:15:13Z

⌛ Testing commit 75d2e5b with merge ea4d0e9...

Let codegen decide when to `mem::swap` with immediates Making `libcore` decide this is silly; the backend has so much better information about when it's a good idea. Thus this PR introduces a new `typed_swap` intrinsic with a fallback body, and replaces that fallback implementation when swapping immediates or scalar pairs. r? oli-obk Replaces rust-lang#111744, and means we'll never need more libs PRs like rust-lang#111803 or rust-lang#107140

bors · 2024-03-23T13:30:13Z

💥 Test timed out

rust-log-analyzer · 2024-03-23T13:34:40Z

A job failed! Check out the build log: (web) (plain)

Click to see the possible cause of the failure (guessed by this bot)

RalfJung · 2024-03-23T13:42:46Z

@bors retry

bors · 2024-03-23T13:57:58Z

⌛ Testing commit 75d2e5b with merge d6eb0f5...

bors · 2024-03-23T15:57:11Z

☀️ Test successful - checks-actions
Approved by: oli-obk
Pushing d6eb0f5 to master...

rust-timer · 2024-03-23T17:14:38Z

Finished benchmarking commit (d6eb0f5): 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%	[-0.4%, -0.4%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.4%	[-0.4%, -0.4%]	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)	4.3%	[0.1%, 6.8%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-5.3%	[-5.3%, -5.3%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.9%	[-5.3%, 6.8%]	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)	2.5%	[2.5%, 2.5%]	1
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%, 0.4%]	27
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.2%	[-1.0%, -0.0%]	10
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.0%	[-1.0%, 0.4%]	37

Bootstrap: 669.588s -> 671.198s (0.24%)
Artifact size: 315.05 MiB -> 314.95 MiB (-0.03%)

Let codegen decide when to `mem::swap` with immediates Making `libcore` decide this is silly; the backend has so much better information about when it's a good idea. Thus this PR introduces a new `typed_swap` intrinsic with a fallback body, and replaces that fallback implementation when swapping immediates or scalar pairs. r? oli-obk Replaces rust-lang#111744, and means we'll never need more libs PRs like rust-lang#111803 or rust-lang#107140

rustbot assigned oli-obk Mar 16, 2024

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. T-libs Relevant to the library team, which will review and decide on the PR/issue. labels Mar 16, 2024

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scottmcm marked this pull request as draft March 16, 2024 05:45

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scottmcm force-pushed the swap-intrinsic-v2 branch from 725417f to 9f992da Compare March 16, 2024 07:53

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Avoid non-windows non-linux in assembly x64 test

75d2e5b

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bors added the merged-by-bors This PR was explicitly merged by bors. label Mar 23, 2024

bors merged commit d6eb0f5 into rust-lang:master Mar 23, 2024

rustbot added this to the 1.79.0 milestone Mar 23, 2024

This was referenced Mar 23, 2024

refactor check_{lang,library}_ub: use a single intrinsic #122629

Merged

CFI: Strip auto traits off Virtual calls #122879

Merged

scottmcm deleted the swap-intrinsic-v2 branch March 23, 2024 16:47

bors mentioned this pull request Mar 23, 2024

Rollup of 10 pull requests #122929

Closed

clubby789 mentioned this pull request Mar 24, 2024

Don't emit load metadata in debug mode #122849

Merged

scottmcm mentioned this pull request Dec 30, 2024

stabilize const_swap #134757

Merged

Let codegen decide when to mem::swap with immediates #122582

Let codegen decide when to mem::swap with immediates #122582

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rust-timer commented Mar 23, 2024

Overall result: ✅ improvements - no action needed

Instruction count

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Let codegen decide when to `mem::swap` with immediates #122582

Let codegen decide when to `mem::swap` with immediates #122582

scottmcm commented Mar 16, 2024 •

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