[perf] Re-monomorphize FnMutDelegate

[compiler-errors]

I'm curious if perf has changed since #101857, since I see FnMutDelegate a lot in perf traces in the new solver.

As noted in #99730 (comment), I'll pay attention to the bootstrap times too.

[compiler-errors]

@bors2 try @rust-timer queue

[rust-bors]

⌛ Trying commit d2a2554 with merge 313e691…

To cancel the try build, run the command @bors2 try cancel.

[rust-bors]

☀️ Try build successful (CI)
Build commit: 313e691 (313e691ca9e15438ebed8df6087f7fcb630b3967, parent: d1d8e386c5e84c4ba857f56c3291f73c27e2d62a)

[rust-timer]

Finished benchmarking commit (313e691): comparison URL.

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

Benchmarking this pull request means it may be perf-sensitive – we'll automatically label it not fit for rolling up. You can override this, but we strongly advise not to, due to possible changes in compiler perf.

Next Steps: If you can justify the regressions found in this try perf run, please do so in sufficient writing along with @rustbot label: +perf-regression-triaged. If not, please fix the regressions and do another perf run. If its results are neutral or positive, the label will be automatically removed.

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

Instruction count

Our most reliable metric. Used to determine the overall result above. However, even this metric can be noisy.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.2%, 0.2%]	1
Regressions ❌ (secondary)	0.2%	[0.2%, 0.2%]	1
Improvements ✅ (primary)	-0.2%	[-0.2%, -0.2%]	4
Improvements ✅ (secondary)	-0.5%	[-1.1%, -0.2%]	8
All ❌✅ (primary)	-0.1%	[-0.2%, 0.2%]	5

Max RSS (memory usage)

Results (primary 0.2%, secondary 2.8%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	3.2%	[3.2%, 3.2%]	1
Regressions ❌ (secondary)	5.2%	[2.3%, 9.0%]	5
Improvements ✅ (primary)	-2.8%	[-2.8%, -2.8%]	1
Improvements ✅ (secondary)	-1.3%	[-2.0%, -0.9%]	3
All ❌✅ (primary)	0.2%	[-2.8%, 3.2%]	2

Cycles

Results (secondary -0.7%)

A less reliable metric. May be of interest, but not used to determine the overall result above.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.3%	[3.3%, 3.3%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.7%	[-2.8%, -2.5%]	2
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 692.944s -> 704.561s (1.68%)
Artifact size: 372.01 MiB -> 375.89 MiB (1.04%)

[compiler-errors]

Interesting how this affects bootstrap (+1.676%).