[WIP] discard impl candidates before evaluating

[BoxyUwU]

was part of #96912 which required this to fix a typenum regression but split out since im curious about perf and this change is spooky .-.

r? @ghost

[BoxyUwU]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[bors]

⌛ Trying commit eb49408 with merge 234c67ccb46ec1a4e9d7381fd3c13bc52d7ea1f3...

[bors]

☀️ Try build successful - checks-actions
Build commit: 234c67ccb46ec1a4e9d7381fd3c13bc52d7ea1f3 (234c67ccb46ec1a4e9d7381fd3c13bc52d7ea1f3)

[rust-timer]

Queued 234c67ccb46ec1a4e9d7381fd3c13bc52d7ea1f3 with parent 6ac8ada, future comparison URL.

[rust-timer]

Finished benchmarking commit (234c67ccb46ec1a4e9d7381fd3c13bc52d7ea1f3): comparison url.

Instruction count

• Primary benchmarks: 🎉 relevant improvements found
• Secondary benchmarks: 🎉 relevant improvements found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	-1.0%	-2.1%	19
Improvements 🎉 (secondary)	-0.2%	-0.2%	2
All 😿🎉 (primary)	-1.0%	-2.1%	19

Max RSS (memory usage)

Results

• Primary benchmarks: 🎉 relevant improvements found
• Secondary benchmarks: mixed results

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	2.3%	2.9%	2
Improvements 🎉 (primary)	-1.7%	-2.2%	4
Improvements 🎉 (secondary)	-1.0%	-1.0%	1
All 😿🎉 (primary)	-1.7%	-2.2%	4

Cycles

Results

• Primary benchmarks: 🎉 relevant improvements found
• Secondary benchmarks: mixed results

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	3.2%	3.2%	1
Improvements 🎉 (primary)	-2.4%	-3.2%	7
Improvements 🎉 (secondary)	-2.5%	-3.2%	4
All 😿🎉 (primary)	-2.4%	-3.2%	7

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.

@bors rollup=never
@rustbot label: +S-waiting-on-review -S-waiting-on-perf -perf-regression

Footnotes

1. the arithmetic mean of the percent change ↩ ↩² ↩³

2. number of relevant changes ↩ ↩² ↩³