Allow Vec's deref to be inlined

[lqd]

This was hot in some local benchmarks, so let's see if this slight improvement will be interesting.

r? @ghost

[lqd]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[bors]

⌛ Trying commit 7d5b65e with merge 4bd1cca271443fd27fd0127d1671cbcfe9ba4757...

[thomcc]

Hm, when I filed #96624 this was being inlined pretty reliably, so I'm surprised. (That said, I'm in favor of this change)

[bors]

☀️ Try build successful - checks-actions
Build commit: 4bd1cca271443fd27fd0127d1671cbcfe9ba4757 (4bd1cca271443fd27fd0127d1671cbcfe9ba4757)

[rust-timer]

Queued 4bd1cca271443fd27fd0127d1671cbcfe9ba4757 with parent 7f997f5, future comparison URL.

[lqd]

I had the same feeling, but was surprised it wasn't marked inline already when seeing it (expectedly) didn't inline with debug assertions, so I tried it. It did seem to make a difference on the cranelift-codegen and keccak benchmarks (without debug-assertions) and I wondered if it'd reproduce. We'll see.

[rust-timer]

Finished benchmarking commit (4bd1cca271443fd27fd0127d1671cbcfe9ba4757): comparison url.

Instruction count

• Primary benchmarks: mixed results
• Secondary benchmarks: mixed results

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	23	19	14	12	37
mean2	0.8%	0.5%	-1.0%	-0.4%	0.1%
max	1.8%	0.7%	-1.8%	-0.4%	1.8%

Max RSS (memory usage)

Results

• Primary benchmarks: mixed results
• Secondary benchmarks: 😿 relevant regressions found

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	1	5	2	0	3
mean2	4.4%	2.0%	-1.6%	N/A	0.4%
max	4.4%	3.9%	-2.2%	N/A	4.4%

Cycles

Results

• Primary benchmarks: mixed results
• Secondary benchmarks: mixed results

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	1	2	9	3	10
mean2	1.5%	2.0%	-1.8%	-4.7%	-1.5%
max	1.5%	2.6%	-3.5%	-5.0%	-3.5%

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.

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

Footnotes

1. number of relevant changes ↩ ↩² ↩³

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

[lqd]

This was more of a win locally:

Here, looking at check builds only to approximate runtime benchmarks, it looks like more of a regression instead. What do you think @thomcc ? Let's probably close it.

[thomcc]

Yeah, this doesn't seem justified. Was worth a shot, though.