simplify.rs smallvecs

[miguelraz]

As suggested by @Nilstrieb here #110477 (comment), I tried swapping out a few vecs for SmallVecs.

Let's run some bots to see if it can help.

r? @ghost

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[workingjubilee]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 3a37978 with merge 4a7b92c1c3a0bc0dd104b348ba280413e6c6c4f6...

[bors]

☀️ Try build successful - checks-actions
Build commit: 4a7b92c1c3a0bc0dd104b348ba280413e6c6c4f6 (4a7b92c1c3a0bc0dd104b348ba280413e6c6c4f6)

[rust-timer]

Finished benchmarking commit (4a7b92c1c3a0bc0dd104b348ba280413e6c6c4f6): comparison URL.

Overall result: ❌ regressions - 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.

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-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)	0.6%	[0.4%, 0.7%]	3
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.6%	[0.4%, 0.7%]	3

Max RSS (memory usage)

Results

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)	1.9%	[1.3%, 2.5%]	4
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.9%	[1.3%, 2.5%]	4

Cycles

Results

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)	5.3%	[4.9%, 5.5%]	3
Improvements ✅ (primary)	-2.8%	[-4.4%, -1.4%]	8
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-2.8%	[-4.4%, -1.4%]	8

[workingjubilee]

This doesn't seem to be as profitable, so while we could continue down this line by e.g. tweaking the numbers on N in [BasicBlock; N], we should probably just close this.

[miguelraz]

Fair. Science was made!

[Noratrieb]

I think you should make a PR to link this PR in a comment in the source. If you don't do that, people are doomed to repeat this without knowing it was already done.