Only walk ribs to collect possibly shadowed params if we are adding params in our new rib

[compiler-errors]

No need to collect params from parent ribs if we literally have no params to declare in this new rib.

Attempt to win back some of the perf in #128357 (comment).

Please review with whitespace off, the diff should be like 2 lines.

r? petrochenkov

[compiler-errors]

@bors try @rust-timer queue

[bors]

⌛ Trying commit abada5f with merge 77379b8...

[bors]

☀️ Try build successful - checks-actions
Build commit: 77379b8 (77379b82e92f815f6ccee6e7d91d7a2d1079911f)

[rust-timer]

Finished benchmarking commit (77379b8): comparison URL.

Overall result: ✅ improvements - no action needed

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-perf -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.6%	[-2.0%, -0.2%]	32
Improvements ✅ (secondary)	-0.3%	[-0.4%, -0.2%]	7
All ❌✅ (primary)	-0.6%	[-2.0%, -0.2%]	32

Max RSS (memory usage)

Results (primary -0.6%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.6%	[-0.6%, -0.6%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.6%	[-0.6%, -0.6%]	1

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 759.288s -> 756.148s (-0.41%)
Artifact size: 336.86 MiB -> 336.72 MiB (-0.04%)

[compiler-errors]

Seems to totally undo the perf regression. This is ready for review now.

[petrochenkov]

Thanks!
@bors r+

[bors]

📌 Commit abada5f has been approved by petrochenkov

It is now in the queue for this repository.

[bors]

⌛ Testing commit abada5f with merge f1fce09...

[bors]

⌛ Testing commit abada5f with merge 724d496...

[compiler-errors]

@bors retry

good morning bors

[bors]

⌛ Testing commit abada5f with merge 0d65e5a...

[bors]

☀️ Test successful - checks-actions
Approved by: petrochenkov
Pushing 0d65e5a to master...

[rust-timer]

Finished benchmarking commit (0d65e5a): comparison URL.

Overall result: ❌✅ regressions and improvements - ACTION NEEDED

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 open an issue or create a new PR that fixes the regressions, add a comment linking to the newly created issue or PR, and then add the perf-regression-triaged label to this PR.

@rustbot label: +perf-regression
cc @rust-lang/wg-compiler-performance

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.2%	[2.2%, 2.2%]	1
Improvements ✅ (primary)	-0.6%	[-2.0%, -0.2%]	31
Improvements ✅ (secondary)	-0.3%	[-0.3%, -0.2%]	6
All ❌✅ (primary)	-0.6%	[-2.0%, -0.2%]	31

Max RSS (memory usage)

Results (primary -1.1%, secondary 0.3%)

This is a less reliable metric that may be of interest but was not used to determine the overall result at the top of this comment.

	mean	range	count
Regressions ❌ (primary)	1.4%	[1.4%, 1.4%]	1
Regressions ❌ (secondary)	0.7%	[0.7%, 0.7%]	3
Improvements ✅ (primary)	-2.4%	[-3.4%, -1.4%]	2
Improvements ✅ (secondary)	-1.0%	[-1.0%, -1.0%]	1
All ❌✅ (primary)	-1.1%	[-3.4%, 1.4%]	3

Cycles

This benchmark run did not return any relevant results for this metric.

Binary size

This benchmark run did not return any relevant results for this metric.

Bootstrap: 761.988s -> 761.974s (-0.00%)
Artifact size: 337.01 MiB -> 336.94 MiB (-0.02%)

[lqd]

The lone regression looks like noise, as a bounce-back from the previous merge, and wasn't present in the most recent perf run. This coercions benchmark looks a bit noisy in the last 3 PRs, the previous merge shouldn't be an improvement either, for example.

I'll mark this as triaged pre-emptively, but we can also check the next merge during weekly triage to see what happens. It's possible some swings will happen until things settle down.

@rustbot label: +perf-regression-triaged