Always inline traversal skeletons

[eggyal]

These methods all just delegate to another part of the traversal machinery, but the compiler does not always select them for inlining which can give rise to missed optimisations.

Local perf on aarch64 shows mild/positive results, but obviously we should check on CI too.

r? wg-compiler-performance

[compiler-errors]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 1218ac2 with merge c2dfb80...

[bors]

☀️ Try build successful - checks-actions
Build commit: c2dfb80 (c2dfb80d186780e87f513b88747b9dce16c216e6)

[rust-timer]

Finished benchmarking commit (c2dfb80): comparison URL.

Overall result: ❌ regressions - 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)	0.5%	[0.4%, 0.9%]	7
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Max RSS (memory usage)

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

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)	-	-	0
Improvements ✅ (primary)	-0.9%	[-0.9%, -0.9%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.9%	[-0.9%, -0.9%]	1

Binary size

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

Bootstrap: 671.419s -> 670.006s (-0.21%)
Artifact size: 315.41 MiB -> 315.43 MiB (0.01%)

[compiler-errors]

Hm, perf doesn't seem helped much. I'm not surprised -- these methods are small enough that I'd expect the compiler to know to inline them already?

@rustbot author