mir-inline: use the visitor to walk blocks

[scottmcm]

Today it's manually DFS-traversing them; let's see if that's actually fruitful.
Inspired by #123011 (comment) & https://discord.com/channels/273534239310479360/957720175619215380/1222325151731945503

r? ghost

[scottmcm]

@bors try @rust-timer queue

[bors]

⌛ Trying commit df06298 with merge b19b210...

[bors]

☀️ Try build successful - checks-actions
Build commit: b19b210 (b19b210be694989be9893109f6525c9d81567e5a)

[rust-timer]

Finished benchmarking commit (b19b210): comparison URL.

Overall result: ❌✅ regressions and 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)	0.2%	[0.2%, 0.2%]	1
Regressions ❌ (secondary)	1.8%	[0.6%, 3.1%]	2
Improvements ✅ (primary)	-0.7%	[-0.7%, -0.7%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.2%	[-0.7%, 0.2%]	2

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)	0.9%	[0.7%, 1.1%]	4
Regressions ❌ (secondary)	3.8%	[3.8%, 3.8%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.9%	[0.7%, 1.1%]	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)	0.6%	[0.4%, 0.8%]	2
Regressions ❌ (secondary)	3.5%	[2.3%, 4.6%]	5
Improvements ✅ (primary)	-0.7%	[-0.7%, -0.7%]	1
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[-0.7%, 0.8%]	3

Binary size

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)	0.2%	[0.1%, 0.4%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.2%	[-0.4%, -0.1%]	3
Improvements ✅ (secondary)	-1.7%	[-1.7%, -1.7%]	1
All ❌✅ (primary)	-0.0%	[-0.4%, 0.4%]	5

Bootstrap: 670.226s -> 670.541s (0.05%)
Artifact size: 315.70 MiB -> 315.64 MiB (-0.02%)

[scottmcm]

Looks like there's a bit of perf impact, though not enough that rustc-perf says it's a regression, so I'll just leave it as-is.

fyi @cjgillot