[WIP] Build the compiler with a single CGU

[Aaron1011]

No description provided.

[rust-highfive]

r? @Mark-Simulacrum

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[Aaron1011]

r? @ghost

[Aaron1011]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[bors]

⌛ Trying commit 97f92af with merge b5c1bf9c686c9b4714ff5fbc277f176c2129a1eb...

[bors]

☀️ Try build successful - checks-actions
Build commit: b5c1bf9c686c9b4714ff5fbc277f176c2129a1eb (b5c1bf9c686c9b4714ff5fbc277f176c2129a1eb)

[rust-timer]

Queued b5c1bf9c686c9b4714ff5fbc277f176c2129a1eb with parent 199d1ae, future comparison URL.

[rust-timer]

Finished benchmarking try commit (b5c1bf9c686c9b4714ff5fbc277f176c2129a1eb): comparison url.

Summary: This change led to significant mixed results 🤷 in compiler performance.

• Very large regression in instruction counts (up to 14.3% on full builds of inflate-check)
• Very large improvement in instruction counts (up to -11.3% on incr-unchanged builds of deeply-nested-async-check)

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 led to changes in compiler perf.

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 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

[the8472]

This time instructions might not be painting the whole picture? 🤔

Except for ctfe-stress-4 and rustc max-rss, wall-time, cycles are mostly trending down as opposed their usual mixed results.

[Mark-Simulacrum]

r? @Aaron1011 until this is ready for review (perfbot will auto remark to -review I think otherwise), happy to review once that happens though!

[Mark-Simulacrum]

I'm going to go ahead and close this. I think the perf results don't speak to this being a clear win, and certainly it would be a big hit to our CI times.