Emit #[inline] on derive(Debug) #117727

saethlin · 2023-11-08T22:37:27Z

While working on #116583 I noticed that the cross_crate_inlinable query identifies a lot of derived Debug impls as a MIR body that's little more than a call, which suggests they may be a good candidate for #[inline]. So here I've implemented that change specifically.

It seems to provide a nice improvement to build times.

Emit #[inline] on derive(Debug) Breaking out part of rust-lang#116583 (comment) r? `@ghost`

saethlin · 2023-11-08T23:15:59Z

@bors try @rust-timer queue

bors · 2023-11-08T23:17:09Z

⌛ Trying commit a317db1 with merge bd37a3c...

Emit #[inline] on derive(Debug) Breaking out part of rust-lang#116583 (comment) r? `@ghost`

bors · 2023-11-09T00:43:16Z

☀️ Try build successful - checks-actions
Build commit: bd37a3c (bd37a3c11ef1592e6e8a9dfe6290477f7ffa2dc8)

rust-timer · 2023-11-09T09:26:23Z

Finished benchmarking commit (bd37a3c): 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)	0.5%	[0.3%, 0.8%]	4
Regressions ❌ (secondary)	2.7%	[1.1%, 3.5%]	4
Improvements ✅ (primary)	-2.4%	[-10.5%, -0.2%]	107
Improvements ✅ (secondary)	-3.4%	[-25.1%, -0.2%]	163
All ❌✅ (primary)	-2.3%	[-10.5%, 0.8%]	111

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)	2.2%	[0.4%, 4.7%]	9
Regressions ❌ (secondary)	4.1%	[2.4%, 5.8%]	2
Improvements ✅ (primary)	-2.3%	[-5.3%, -0.6%]	17
Improvements ✅ (secondary)	-2.9%	[-5.0%, -1.1%]	11
All ❌✅ (primary)	-0.8%	[-5.3%, 4.7%]	26

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)	0.9%	[0.4%, 1.4%]	2
Regressions ❌ (secondary)	3.0%	[2.8%, 3.4%]	3
Improvements ✅ (primary)	-4.4%	[-11.4%, -0.7%]	53
Improvements ✅ (secondary)	-5.5%	[-24.5%, -1.6%]	89
All ❌✅ (primary)	-4.2%	[-11.4%, 1.4%]	55

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)	0.9%	[0.1%, 3.1%]	26
Regressions ❌ (secondary)	4.4%	[0.2%, 7.1%]	6
Improvements ✅ (primary)	-2.7%	[-6.9%, -0.1%]	113
Improvements ✅ (secondary)	-3.7%	[-11.9%, -0.6%]	93
All ❌✅ (primary)	-2.0%	[-6.9%, 3.1%]	139

Bootstrap: 663.159s -> 673.479s (1.56%)
Artifact size: 308.75 MiB -> 308.99 MiB (0.08%)

Noratrieb · 2023-11-09T21:57:09Z

I suspect that the speedup is for a very simple reason: #[inline] causes functions to be codegened downstream, or in the case of dead code: never. Debug impls are frequently dead code.
Evidence for this lies in the hello world benchmark. Linking got significantly faster, so the linker has less to process. This makes sense, the standard library contains lots of Debug impls that hello world doesn't use. The same reasoning can extend to other benchmarks.

nbdd0121 · 2023-11-09T22:31:25Z

In that case I think what we want is to only mono the function downstream, but not have it marked as inline by LLVM. Instead of inlining should we experiment something like #[rustc_late_mono]?

saethlin · 2023-11-09T22:46:06Z

Inlining is still at LLVM's discretion, all this attribute does is apply the inlinehint attribute. It also makes functions eligible for MIR inlining and causes them to not only be lazily lowered, but also to perhaps be lowered multiple times. (it also possibly has neighbor effects on symbol visibility, including that of statics)

It does a lot. I am not sure to what degree all these effects are separable, but we're having this conversation because I am studying separating the codegen style and MIR inlining from the LLVM attribute and inferring the non-inlinehint effects. If you want to have a broader conversation about this we should do that outside this PR, maybe on Zulip, but in my opinion we are primarily short on information to feed a useful discussion.

scottmcm · 2023-11-09T23:05:40Z

@nnethercote My hypothesis here is that it's a happy consequence of the move to debug_tuple_field4_finish and friends -- those functions are not #[inline], so the fmt methods that're being inlined in this PR aren't the ones with lots of calls to DebugStruct::field and such, just doing the pointer projection and vtable pointer copying before making the single call to the appropriate fmt_helpers_for_derive.

scottmcm · 2023-11-09T23:14:26Z

Actually, one thing that puzzles me: how does this make a bunch of check builds so much faster? What are those check builds doing that cares enough about inlining of these things to show up? Naïvely I'd have though it would be impossible for inlining to matter for things like check that don't do codegen (or even optimized MIR, right?).

The usual possibility of "oh well it make rustc faster" feels like it can't possibly be the answer since I can't imagine that Debug-printing stuff is in the rustc critical path for check builds either...

bors · 2023-11-09T23:29:42Z

☀️ Test successful - checks-actions
Approved by: nnethercote
Pushing 0f44eb3 to master...

rust-timer · 2023-11-10T05:05:25Z

Finished benchmarking commit (0f44eb3): 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

Warning ⚠: The following benchmark(s) failed to build:

cargo-0.60.0

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)	3.1%	[0.3%, 13.7%]	5
Regressions ❌ (secondary)	1.8%	[0.2%, 3.4%]	6
Improvements ✅ (primary)	-2.3%	[-10.6%, -0.1%]	110
Improvements ✅ (secondary)	-3.2%	[-25.2%, -0.1%]	177
All ❌✅ (primary)	-2.1%	[-10.6%, 13.7%]	115

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)	1.7%	[0.5%, 3.9%]	6
Regressions ❌ (secondary)	2.1%	[0.9%, 4.6%]	7
Improvements ✅ (primary)	-2.1%	[-6.4%, -0.4%]	27
Improvements ✅ (secondary)	-3.7%	[-4.8%, -2.1%]	9
All ❌✅ (primary)	-1.4%	[-6.4%, 3.9%]	33

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)	3.2%	[0.6%, 9.9%]	4
Regressions ❌ (secondary)	3.3%	[3.0%, 3.5%]	3
Improvements ✅ (primary)	-3.9%	[-11.4%, -0.6%]	62
Improvements ✅ (secondary)	-5.5%	[-24.2%, -1.4%]	89
All ❌✅ (primary)	-3.4%	[-11.4%, 9.9%]	66

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)	0.9%	[0.1%, 3.1%]	26
Regressions ❌ (secondary)	4.4%	[0.2%, 7.1%]	6
Improvements ✅ (primary)	-2.8%	[-6.9%, -0.1%]	108
Improvements ✅ (secondary)	-3.7%	[-11.9%, -0.6%]	93
All ❌✅ (primary)	-2.1%	[-6.9%, 3.1%]	134

Bootstrap: 662.531s -> 673.197s (1.61%)
Artifact size: 308.76 MiB -> 311.10 MiB (0.76%)

saethlin · 2023-11-10T05:19:39Z

Improvements outweigh regressions. And the big regression looks spurious, probably related to the collector slowness that started a few days ago.
@rustbot label: +perf-regression-triaged

RalfJung · 2023-11-16T21:07:48Z

Would it be worth trying to only apply this attribute to structs with at most 5 fields, but not enums or larger structs? Those are exactly the ones where the body will be just a single function call.

…-debug, r=<try> Try not applying #[inline] to big structs Per rust-lang#117727 (comment) r? `@ghost`

saethlin · 2023-11-18T08:04:27Z

I tried: #118031 (comment) and it's a huge regression.

So I suspect the dead code effect and the MIR optimization effects are both important here.

RalfJung · 2023-11-18T08:37:49Z

Interesting... Thanks for trying!

To be clear the `#[inline]` does not hint that inlining is beneficial, but it does give the compiler the option to inline if the compiler things it would be beneficial. This starts adding the `#[inline]` attribute to: 1. `IsVariant`: it's expected that this is often beneficial since its body is tiny. 2. `Debug`: This is to stay in line with the `std` implementation of the `Debug` derive. rust-lang/rust#117727 It also explicitely doesn't add the attribute to the methods of `Error`, since those are almost never called in hot code paths. Fixes #317

To be clear, the `#[inline]` does not hint that inlining is beneficial, but it does give the compiler the option to inline if the compiler things it would be beneficial. This starts adding the `#[inline]` attribute to: 1. `IsVariant`: it's expected that this is often beneficial, since its body is tiny. 2. `Debug`: This is to stay in line with the `std` implementation of the `Debug` derive. rust-lang/rust#117727 It also explicitly doesn't add the attribute to the methods of `Error`, since those are almost never called in hot code paths.

rust-lang/rust#117727

Update Rust toolchain from nightly-2023-11-09 to nightly-2023-11-10 without any other source changes. This is an automatically generated pull request. If any of the CI checks fail, manual intervention is required. In such a case, review the changes at https://github.com/rust-lang/rust from rust-lang@fdaaaf9 up to rust-lang@0f44eb3. The log for this commit range is: rust-lang@0f44eb32f1 Auto merge of rust-lang#117727 - saethlin:inline-derived-fmt, r=nnethercote rust-lang@eae4135939 Auto merge of rust-lang#117708 - onur-ozkan:x-setup, r=clubby789 rust-lang@4c8862b263 Auto merge of rust-lang#117122 - ferrocene:pa-configure-git-diff, r=albertlarsan68 rust-lang@d32d9238cf Emit #[inline] on derive(Debug) rust-lang@b7583d38b7 Auto merge of rust-lang#117712 - lcnr:expand-coroutine, r=jackh726 rust-lang@488dd9bc73 fmt rust-lang@e7998aa21f Auto merge of rust-lang#117734 - nnethercote:rm-Zstrip, r=davidtwco rust-lang@287ae4db75 Auto merge of rust-lang#117632 - Nilstrieb:icup, r=davidtwco rust-lang@492e57c6ad Auto merge of rust-lang#117736 - TaKO8Ki:rollup-fjrtmlb, r=TaKO8Ki rust-lang@d1e26401bc chore(bootstrap): capitalize {error, warning, info, note} tags rust-lang@42fbf3ebf5 allow users to override the existing configuration during x setup rust-lang@3d6417fc7a check config file before prompts on x setup rust-lang@f5195c52bb Rollup merge of rust-lang#117724 - Kobzol:shim-error-message, r=onur-ozkan rust-lang@e603f4491c Rollup merge of rust-lang#117723 - onur-ozkan:keep-bootstrap-on-x-clean, r=albertlarsan68 rust-lang@6533c62ce7 Rollup merge of rust-lang#117705 - tshepang:patch-2, r=Nilstrieb rust-lang@b4fa5b7004 Rollup merge of rust-lang#117694 - jmillikin:core-io-borrowed-buf, r=m-ou-se rust-lang@4cc549811f Rollup merge of rust-lang#117645 - compiler-errors:auto-trait-subst, r=petrochenkov rust-lang@a1a8d6fe9c Rollup merge of rust-lang#116762 - WaffleLapkin:fixup_fromptr_docs, r=RalfJung rust-lang@d8dbf7ca0e Auto merge of rust-lang#117557 - Zoxc:panic-prio, r=petrochenkov rust-lang@ecc936b155 Remove `-Z strip`. rust-lang@57fb1e643a Auto merge of rust-lang#117454 - shepmaster:github-actions-m1-tests, r=GuillaumeGomez,onur-ozkan rust-lang@341c85648c Move `BorrowedBuf` and `BorrowedCursor` from `std:io` to `core::io` rust-lang@92267c9794 update mir-opt tests rust-lang@992d93f687 rename `BorrowKind::Shallow` to `Fake` rust-lang@a42eca42df generator layout: ignore fake borrows rust-lang@622be2d138 Restore rustc shim error message rust-lang@de0458af97 speed up `x clean` rust-lang@6909992501 Run tests in CI for aarch64-apple-darwin rust-lang@64090536d4 Install tidy for aarch64-apple-darwin rust-lang@469d34b39b Mark Rustdoc test as Linux-only rust-lang@bf360d407e instrument constituent types computation rust-lang@03435e6fdd accept review suggestion rust-lang@769ad29c3e triagebot.toml: use inclusive language rust-lang@102384523a Document how rust atomics work wrt mixed-sized and non-atomic accesses rust-lang@c17d33f1df Extend builtin/auto trait args with error when they have >1 argument rust-lang@580fa0c1a9 rename github_repository to git_repository rust-lang@ffffc2038f Update ICU4X rust-lang@ff1858e2aa Make `FatalErrorMarker` lower priority than other panics rust-lang@4a0873533f update suggest-tests rust-lang@5a562d962e pass the correct args to compiletest rust-lang@545cc830e1 allow configuring the parent GitHub repository Co-authored-by: celinval <[email protected]>

To be clear, the `#[inline]` does not hint that inlining is beneficial, but it does give the compiler the option to inline if the compiler things it would be beneficial. This starts adding the `#[inline]` attribute to: 1. `IsVariant`: it's expected that this is often beneficial, since its body is tiny. 2. `Debug`: This is to stay in line with the `std` implementation of the `Debug` derive. rust-lang/rust#117727 It also explicitly doesn't add the attribute to the methods of `Error`, since those are almost never called in hot code paths.

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 Nov 8, 2023

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bors added a commit to rust-lang-ci/rust that referenced this pull request Nov 8, 2023

Auto merge of rust-lang#117727 - saethlin:inline-derived-fmt, r=<try>

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Emit #[inline] on derive(Debug) Breaking out part of rust-lang#116583 (comment) r? `@ghost`

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saethlin force-pushed the inline-derived-fmt branch from 857e13c to a317db1 Compare November 8, 2023 23:01

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bors added a commit to rust-lang-ci/rust that referenced this pull request Nov 8, 2023

Auto merge of rust-lang#117727 - saethlin:inline-derived-fmt, r=<try>

bd37a3c

Emit #[inline] on derive(Debug) Breaking out part of rust-lang#116583 (comment) 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 Nov 9, 2023

saethlin marked this pull request as ready for review November 9, 2023 15:26

bors added the merged-by-bors This PR was explicitly merged by bors. label Nov 9, 2023

bors merged commit 0f44eb3 into rust-lang:master Nov 9, 2023
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rustbot added this to the 1.75.0 milestone Nov 9, 2023

saethlin deleted the inline-derived-fmt branch November 9, 2023 23:39

rustbot added the perf-regression-triaged The performance regression has been triaged. label Nov 10, 2023

JelteF mentioned this pull request Nov 17, 2023

Use #[inline] attribute on Debug JelteF/derive_more#317

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saethlin mentioned this pull request Nov 18, 2023

Try not applying #[inline] to big structs #118031

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bors added a commit to rust-lang-ci/rust that referenced this pull request Nov 18, 2023

Auto merge of rust-lang#118031 - saethlin:drop-inline-for-complicated…

6973d65

…-debug, r=<try> Try not applying #[inline] to big structs Per rust-lang#117727 (comment) r? `@ghost`

JelteF mentioned this pull request Jan 22, 2024

Add #[inline] attribute to a few more methods JelteF/derive_more#334

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matthiaskrgr mentioned this pull request Feb 21, 2024

ICE: Got a scalar pair where a scalar was expected #121363

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nazar-pc mentioned this pull request Mar 11, 2024

Use #[inline] for fmt::Debug impls autonomys/subspace#2600

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taiki-e added a commit to taiki-e/portable-atomic that referenced this pull request Mar 17, 2024

Add #[inline] to fmt impls

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rust-lang/rust#117727

taiki-e added a commit to taiki-e/atomic-maybe-uninit that referenced this pull request Mar 19, 2024

Add #[inline] to Debug impl

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rust-lang/rust#117727

saethlin mentioned this pull request Aug 25, 2024

Tweak some attributes to improve panic_immediate_abort #129589

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Emit #[inline] on derive(Debug) #117727

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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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