shuf: use memchr in split_seps

[xtqqczze]

No description provided.

[github-actions]

GNU testsuite comparison:

Skipping an intermittent issue tests/date/date-locale-hour (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/seq/seq-epipe is now being skipped but was previously passing.
Congrats! The gnu test tests/expand/bounded-memory is now passing!

[codspeed-hq]

Merging this PR will degrade performance by 13.4%

⚠️ Different runtime environments detected

Some benchmarks with significant performance changes were compared across different runtime environments,
which may affect the accuracy of the results.

Open the report in CodSpeed to investigate

⚡ 2 improved benchmarks
❌ 1 regressed benchmark
✅ 306 untouched benchmarks
⏩ 46 skipped benchmarks¹

⚠️ Please fix the performance issues or acknowledge them on CodSpeed.

Performance Changes

	Mode	Benchmark	BASE	HEAD	Efficiency
❌	Simulation	shuf_lines[100000]	27.4 ms	31.7 ms	-13.4%
⚡	Memory	shuf_lines[100000]	10.3 MB	9.8 MB	+5.31%
⚡	Memory	shuf_repeat_sampling[50000]	1.2 MB	1.1 MB	+4.72%

---

_{Comparing xtqqczze:memchr/split_seps (651812e) with main (2d5e77d)²}

Footnotes

1. 46 benchmarks were skipped, so the baseline results were used instead. If they were deleted from the codebase, click here and archive them to remove them from the performance reports. ↩

2. No successful run was found on main (02104f3) during the generation of this report, so 2d5e77d was used instead as the comparison base. There might be some changes unrelated to this pull request in this report. ↩

[oech3]

It touches data twice. I think it is why perf -13.49% .

[oech3]

You might try to scan first few byte and predict capacity.

[xtqqczze]

first we should improve benchmarks to include short average line length: #11364

[oech3]

You might try to scan first few byte and predict capacity.

Can we get length of one SIMD scan? Averadge is enough (no need to get from system)?

[github-actions]

GNU testsuite comparison:

GNU test failed: tests/tail/retry. tests/tail/retry is passing on 'main'. Maybe you have to rebase?
Skip an intermittent issue tests/pr/bounded-memory (fails in this run but passes in the 'main' branch)
Skipping an intermittent issue tests/cut/bounded-memory (passes in this run but fails in the 'main' branch)
Skipping an intermittent issue tests/date/date-locale-hour (passes in this run but fails in the 'main' branch)
Note: The gnu test tests/tail/tail-n0f is now being skipped but was previously passing.
Congrats! The gnu test tests/unexpand/bounded-memory is now passing!