[perf] rustdoc: Perform less work when cleaning middle::ty parenthesized generic args

[fmease]

CC #132697. I presume the perf regression it caused (if real) boils down to query invocation overhead, namely of def_kind & trait_def as we don't seem to be decoding more often from the crate metadata.

I won't try the obvious and reduce the amount of query calls by threading information via params as that would render the code awkward.

So instead I'm simply trying to attack some low-hanging fruits in the vicinity.

---

Previously, we would clean_middle_generic_args unconditionally inside clean_middle_generic_args_with_constraints even though we didn't actually use its result for parenthesized generic args (Trait(...) -> ...).

Now, we only call clean_middle_generic_args when necessary. Lastly, I've simplified clean_middle_generic_args_with_constraints.

---

r? ghost

[fmease]

@bors try @rust-timer queue

[bors]

⌛ Trying commit e51bfa6 with merge 66ae3a1...

[bors]

☀️ Try build successful - checks-actions
Build commit: 66ae3a1 (66ae3a104b1b7795cf32e60edc012d2bccd27e26)

[rust-timer]

Finished benchmarking commit (66ae3a1): 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 the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.3%	[-0.4%, -0.1%]	5
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

Results (primary -0.1%, secondary 0.7%)

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)	2.8%	[2.8%, 2.8%]	1
Regressions ❌ (secondary)	0.7%	[0.7%, 0.7%]	1
Improvements ✅ (primary)	-1.6%	[-2.2%, -0.9%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.1%	[-2.2%, 2.8%]	3

Cycles

Results (secondary -2.4%)

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
Improvements ✅ (secondary)	-2.4%	[-3.2%, -2.0%]	9
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 786.53s -> 785.607s (-0.12%)
Artifact size: 335.31 MiB -> 335.28 MiB (-0.01%)

[fmease]

Outdated since #131985

[fmease]

2/5 benchmarks spurious (not a doc profile). corrected perf summary:

Range	Mean	Count
[ -0.23%, -0.14%]	-0.19%	3 (3)

r? rustdoc

[GuillaumeGomez]

When the PR is ready for you, please run the perf check:

@bors try @rust-timer queue

[fmease]

Oh, nothing really changed with my two force-pushes, I only renamed a variable 😅

[GuillaumeGomez]

Oh I don't judge, you can do as many renamings as you want. 🤣

[fmease]

When the PR is ready for you

Right, it's ready, that's what I meant to say above. I might come back to #132697's regression but for now, I won't due to time constraints.

[fmease]

@bors r=GuillaumeGomez

[bors]

📌 Commit 4660316 has been approved by GuillaumeGomez

It is now in the queue for this repository.

[bors]

⌛ Testing commit 4660316 with merge ec239b8...

[bors]

☀️ Test successful - checks-actions
Approved by: GuillaumeGomez
Pushing ec239b8 to master...

[rust-timer]

Finished benchmarking commit (ec239b8): comparison URL.

Overall result: ❌✅ regressions and improvements - please read the text below

Our benchmarks found a performance regression caused by this PR.
This might be an actual regression, but it can also be just noise.

Next Steps:

• If the regression was expected or you think it can be justified,
  please write a comment with sufficient written justification, and add
  @rustbot label: +perf-regression-triaged to it, to mark the regression as triaged.
• If you think that you know of a way to resolve the regression, try to create
  a new PR with a fix for the regression.
• If you do not understand the regression or you think that it is just noise,
  you can ask the @rust-lang/wg-compiler-performance working group for help (members of this group
  were already notified of this PR).

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

Instruction count

This is the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	1.0%	[1.0%, 1.0%]	2
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-0.2%	[-0.3%, -0.1%]	5
All ❌✅ (primary)	1.0%	[1.0%, 1.0%]	2

Max RSS (memory usage)

Results (primary -0.8%, secondary 3.0%)

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)	3.0%	[3.0%, 3.0%]	1
Improvements ✅ (primary)	-0.8%	[-1.1%, -0.5%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.8%	[-1.1%, -0.5%]	2

Cycles

Results (secondary -2.2%)

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
Improvements ✅ (secondary)	-2.2%	[-2.8%, -1.8%]	4
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 784.378s -> 786.527s (0.27%)
Artifact size: 335.40 MiB -> 335.37 MiB (-0.01%)

[lqd]

Compile time regressions on a rustdoc change? I don't think so, perf bot.

@rustbot label: +perf-regression-triaged

(these should stabilize in the next merge, hopefully, so let's re-check later)