Optimize const_prop mir-opt by writing the layouts to ext

[SparrowLii]

From the FIXME in the const_prop mir-opt.
Write layouts of locals to ext in advance, which should reduce the invocation of layout_of query and thus reduce compilation time.

[rust-highfive]

r? @petrochenkov

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[petrochenkov]

r? @oli-obk (as suggested by github)

[wesleywiser]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[bors]

⌛ Trying commit 2fb2960 with merge 5577c9a78853cb76c76e642a7d972afa992a0b22...

[bors]

☀️ Try build successful - checks-actions
Build commit: 5577c9a78853cb76c76e642a7d972afa992a0b22 (5577c9a78853cb76c76e642a7d972afa992a0b22)

[rust-timer]

Queued 5577c9a78853cb76c76e642a7d972afa992a0b22 with parent c102c5c, future comparison URL.

[rust-timer]

Finished benchmarking commit (5577c9a78853cb76c76e642a7d972afa992a0b22): comparison url.

Summary:

• Primary benchmarks: 😿 relevant regression found
• Secondary benchmarks: 😿 relevant regressions found

	Regressions 😿 (primary)	Regressions 😿 (secondary)	Improvements 🎉 (primary)	Improvements 🎉 (secondary)	All 😿 🎉 (primary)
count1	1	8	0	0	1
mean2	2.1%	0.6%	N/A	N/A	2.1%
max	2.1%	1.2%	N/A	N/A	2.1%

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.

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. the arithmetic mean of the percent change ↩

[SparrowLii]

It seems that writing layouts of locals into ext hardly helps in reducing compilation time. I think this PR can be closed, and maybe this FIXME can also be removed?

[oli-obk]

Yea, that sounds reasonable