Make MIR pass name a compile-time constant.

[cjgillot]

Post-processing a compile-time string at runtime is a bit silly. This PR makes CTFE do it all.

[cjgillot]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 498ef48 with merge db13a70...

[bors]

☀️ Try build successful - checks-actions
Build commit: db13a70 (db13a70d2c956bc803a39df8c042d4c661fadbe0)

[rust-timer]

Finished benchmarking commit (db13a70): 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 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
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-1.6%	[-1.6%, -1.6%]	1
All ❌✅ (primary)	-	-	0

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
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-3.2%	[-3.2%, -3.2%]	1
Improvements ✅ (secondary)	-1.8%	[-2.6%, -1.3%]	4
All ❌✅ (primary)	-3.2%	[-3.2%, -3.2%]	1

Cycles

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

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)	0.5%	[0.5%, 0.5%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.5%	[0.5%, 0.5%]	1

Bootstrap: 665.464s -> 664.961s (-0.08%)
Artifact size: 308.33 MiB -> 308.34 MiB (0.00%)

[rustbot]

Some changes occurred to MIR optimizations

cc @rust-lang/wg-mir-opt

[cjgillot]

r? compiler

[Noratrieb]

Given that this is perf neutral, I don't think it makes sense to merge, as the runtime code is a lot nicer.

[cjgillot]

I agree the code is much uglier than the runtime implementation. I'd be glad to use the exact same code, but I had to wrestle the compiler into accepting this mess.

Perf-wise, the improvement is tiny (<1%) but measurable. See the unfiltered results.

[tmiasko]

I recall trying to change this as well to avoid all those calls to memrchr, but at the time API available from const context was even smaller. This implementation seems reasonable to me.

@bors r+

[bors]

📌 Commit ad25f0e has been approved by tmiasko

It is now in the queue for this repository.

[bors]

⌛ Testing commit ad25f0e with merge a58ec8f...

[bors]

☀️ Test successful - checks-actions
Approved by: tmiasko
Pushing a58ec8f to master...

[rust-timer]

Finished benchmarking commit (a58ec8f): comparison URL.

Overall result: no relevant changes - no action needed

@rustbot label: -perf-regression

Instruction count

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

Max RSS (memory usage)

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

Cycles

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

Binary size

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

Bootstrap: 663.041s -> 664.028s (0.15%)
Artifact size: 308.37 MiB -> 308.38 MiB (0.00%)