Perf experiment for "Get piece unchecked in write"

[camsteffen]

Measuring the true cost of #83302 by reverting it and #89139

r? @ghost

[camsteffen]

@rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[camsteffen]

@bors try

[bors]

⌛ Trying commit 669f6ec with merge f89bef1216fa28f8a8774452b0419ad8fbb0ed6f...

[bors]

☀️ Try build successful - checks-actions
Build commit: f89bef1216fa28f8a8774452b0419ad8fbb0ed6f (f89bef1216fa28f8a8774452b0419ad8fbb0ed6f)

[rust-timer]

Queued f89bef1216fa28f8a8774452b0419ad8fbb0ed6f with parent a479766, future comparison URL.

[rust-timer]

Finished benchmarking commit (f89bef1216fa28f8a8774452b0419ad8fbb0ed6f): comparison url.

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

• Moderate improvement in instruction counts (up to -0.7% on full builds of deeply-nested-closures)
• Moderate regression in instruction counts (up to 0.7% on incr-patched: b9b3e592dd cherry picked builds of style-servo)

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 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