DO NOT MERGE: Try using stacker fast path optimization

[hkratz]

Some stacker optimizations in a private branch (see rust-lang/stacker@master...hkratz:optimize-fast-path) that I want to try with a perf run to see if that is worth pursuing. Assembly and local perf run look promising.

Also includes accepted, but not yet merged #93934.

r? @ghost
@rustbot label S-waiting-on-author

[pierwill]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[bors]

⌛ Trying commit 5aea577 with merge 814484750e7788a3b3706831bc6d4f96286f7c3b...

[bors]

☀️ Try build successful - checks-actions
Build commit: 814484750e7788a3b3706831bc6d4f96286f7c3b (814484750e7788a3b3706831bc6d4f96286f7c3b)

[rust-timer]

Queued 814484750e7788a3b3706831bc6d4f96286f7c3b with parent 30b3f35, future comparison URL.

[rust-timer]

Finished benchmarking commit (814484750e7788a3b3706831bc6d4f96286f7c3b): comparison url.

Summary: This benchmark run shows 102 relevant improvements 🎉 but 3 relevant regressions 😿 to instruction counts.

• Average relevant regression: 1.0%
• Average relevant improvement: -0.4%
• Largest improvement in instruction counts: -2.9% on incr-patched: add static arr item builds of coercions debug
• Largest regression in instruction counts: 1.1% on incr-unchanged builds of ctfe-stress-4 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 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

[Dylan-DPC]

Closing this as it was an experiment.