Inline <T as From<T>>::from

[scottmcm]

I noticed (in #100693 (comment)) that the MIR for https://play.rust-lang.org/?version=nightly&mode=release&edition=2021&gist=67097e0494363ee27421a4e3bdfaf513 has inlined most stuff

scope 5 (inlined <Result<i32, u32> as Try>::branch)

scope 8 (inlined <Result<i32, u32> as Try>::from_output)

But yet the do-nothing from call was still there:

_17 = <u32 as From<u32>>::from(move _18) -> bb9;

So let's give this a try and see what perf has to say.

[rust-highfive]

r? @m-ou-se

(rust-highfive has picked a reviewer for you, use r? to override)

[scottmcm]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit 8118a31 with merge a4685669c45ee36d41b7e6902366cbbee52120c4...

[bors]

☀️ Try build successful - checks-actions
Build commit: a4685669c45ee36d41b7e6902366cbbee52120c4 (a4685669c45ee36d41b7e6902366cbbee52120c4)

[rust-timer]

Queued a4685669c45ee36d41b7e6902366cbbee52120c4 with parent 8064a49, future comparison URL.

[rust-timer]

Finished benchmarking commit (a4685669c45ee36d41b7e6902366cbbee52120c4): comparison url.

Instruction count

• Primary benchmarks: ✅ relevant improvements found
• Secondary benchmarks: ✅ relevant improvements found

	mean1	max	count2
Regressions ❌ (primary)	0.7%	1.0%	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.7%	-2.4%	24
Improvements ✅ (secondary)	-1.2%	-2.3%	19
All ❌✅ (primary)	-0.6%	-2.4%	26

Max RSS (memory usage)

Results

• Primary benchmarks: ✅ relevant improvement found
• Secondary benchmarks: ❌ relevant regressions found

	mean1	max	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.1%	2.2%	2
Improvements ✅ (primary)	-8.4%	-8.4%	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-8.4%	-8.4%	1

Cycles

Results

• Primary benchmarks: ✅ relevant improvement found
• Secondary benchmarks: ✅ relevant improvements found

	mean1	max	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.9%	-2.9%	1
Improvements ✅ (secondary)	-2.9%	-3.5%	3
All ❌✅ (primary)	-2.9%	-2.9%	1

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

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-review -S-waiting-on-perf -perf-regression

Footnotes

1. the arithmetic mean of the percent change ↩ ↩² ↩³

2. number of relevant changes ↩ ↩² ↩³

[scottmcm]

Oh! Well that's more obviously-good than I was expecting.

[c410-f3r]

Looking forward to see the day where I won't have to worry about placing #[inline] annotations in trivial methods/functions.

[m-ou-se]

@bors r+

This change looks fine by itself, but I'm worried about #[inline] and #[inline(always)] in general. In general we try to avoid #[inline(always)], and #[inline] is "mostly" "meaningless" on generic functions. (For some unclear definition of "mostly" and "meaningless".)

Do we have some plan forward, other than just expecting people to apply these attributes manually and benchmarking at every step?

[bors]

📌 Commit 8118a31 has been approved by m-ou-se

It is now in the queue for this repository.

[bors]

⌛ Testing commit 8118a31 with merge 380addd...

[bors]

☀️ Test successful - checks-actions
Approved by: m-ou-se
Pushing 380addd to master...

[rust-timer]

Finished benchmarking commit (380addd): 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.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.8%	[-2.2%, -0.2%]	25
Improvements ✅ (secondary)	-1.4%	[-2.2%, -0.5%]	22
All ❌✅ (primary)	-0.8%	[-2.2%, -0.2%]	25

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.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	7.4%	[7.3%, 7.6%]	2
Improvements ✅ (primary)	-0.8%	[-0.8%, -0.8%]	1
Improvements ✅ (secondary)	-2.3%	[-2.7%, -1.9%]	3
All ❌✅ (primary)	-0.8%	[-0.8%, -0.8%]	1

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.

	mean1	range	count2
Regressions ❌ (primary)	2.9%	[2.9%, 2.9%]	1
Regressions ❌ (secondary)	2.4%	[2.4%, 2.4%]	1
Improvements ✅ (primary)	-1.8%	[-2.2%, -1.4%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.2%	[-2.2%, 2.9%]	3

Footnotes

1. the arithmetic mean of the percent change ↩ ↩² ↩³

2. number of relevant changes ↩ ↩² ↩³

[Kobzol]

@m-ou-se I think (hope) that using (inter-crate) LTO when compiling rustc could reduce the need to sprinkle these inline annotations manually. We're currently trying to push that forward with @bjorn3.