Streamline the format macro.

[nnethercote]

Removing the unnecessary local variable speeds up compilation a little.

r? @cuviper

[klensy]

Scope was added in #64856 without comment, so there no issues with somehow reverting it back?

[nnethercote]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 219714d with merge 77bade5...

[nnethercote]

Scope was added in #64856 without comment, so there no issues with somehow reverting it back?

I'm not sure. All the tests pass. Unlike back then, the block is now within the must_use call, giving an extra scope. The block itself is load-bearing; if I remove the { and } it slightly changes some error messages.

[bors]

☀️ Try build successful - checks-actions
Build commit: 77bade5 (77bade583880b062742296c0e9a2dc4cd1a389b3)

[rust-timer]

Finished benchmarking commit (77bade5): comparison URL.

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

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 the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	0.2%	[0.2%, 0.2%]	1
Regressions ❌ (secondary)	1.8%	[1.7%, 1.9%]	6
Improvements ✅ (primary)	-0.3%	[-0.4%, -0.1%]	13
Improvements ✅ (secondary)	-0.1%	[-0.1%, -0.1%]	1
All ❌✅ (primary)	-0.2%	[-0.4%, 0.2%]	14

Max RSS (memory usage)

Results (primary 2.1%)

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)	3.5%	[0.7%, 12.2%]	10
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-2.3%	[-3.4%, -1.5%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.1%	[-3.4%, 12.2%]	13

Cycles

Results (primary -0.0%, secondary -2.4%)

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)	0.4%	[0.4%, 0.4%]	2
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.5%	[-0.5%, -0.4%]	2
Improvements ✅ (secondary)	-2.4%	[-2.4%, -2.4%]	1
All ❌✅ (primary)	-0.0%	[-0.5%, 0.4%]	4

Binary size

Results (primary -0.0%)

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)	-0.0%	[-0.2%, -0.0%]	15
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.0%	[-0.2%, -0.0%]	15

Bootstrap: 776.892s -> 774.802s (-0.27%)
Artifact size: 365.04 MiB -> 365.02 MiB (-0.01%)

[cuviper]

Scope was added in #64856 without comment, so there no issues with somehow reverting it back?

It is probably now benefiting from the 2024 scope change:
https://doc.rust-lang.org/nightly/edition-guide/rust-2024/temporary-tail-expr-scope.html

[nnethercote]

The cargo-0.60.0 perf improvement is real. That was the motivating example -- I did some ad hoc profiling of where expressions are created and found that format! calls accounted for ~1% of all expressions created when compiling that benchmark.

The match-stress regression is puzzling. I can't reproduce when I profile local builds. When I run the Cachegrind repro command to profile the CI builds it says the difference is entirely in rustc_pattern_analysis::usefulness::compute_exhaustiveness_and_usefulness::<rustc_pattern_analysis::rustc::RustcPatCtxt>::{closure#0}. There is no line-level info, I think closure#0 is just |r| !r.pats.relevant so no idea what's happening there.

[nnethercote]

@bors try @rust-timer queue

[bors]

⌛ Trying commit bc8df50 with merge 42bd627...

[bors]

☀️ Try build successful - checks-actions
Build commit: 42bd627 (42bd6276c0918c5943c8e76015a4bf68af24177f)

[rust-timer]

Finished benchmarking commit (42bd627): comparison URL.

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

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 the most reliable metric that we have; it was used to determine the overall result at the top of this comment. However, even this metric can sometimes exhibit noise.

	mean	range	count
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	1.8%	[1.7%, 1.9%]	6
Improvements ✅ (primary)	-0.3%	[-0.3%, -0.3%]	3
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.3%	[-0.3%, -0.3%]	3

Max RSS (memory usage)

Results (primary 1.5%, secondary 2.0%)

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)	2.8%	[0.6%, 8.4%]	5
Regressions ❌ (secondary)	2.0%	[2.0%, 2.0%]	1
Improvements ✅ (primary)	-1.9%	[-2.9%, -0.9%]	2
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	1.5%	[-2.9%, 8.4%]	7

Cycles

Results (primary 0.4%)

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)	0.4%	[0.4%, 0.4%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.4%	[0.4%, 0.4%]	1

Binary size

Results (primary -0.1%)

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)	0.1%	[0.1%, 0.1%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-0.1%	[-0.2%, -0.0%]	18
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-0.1%	[-0.2%, 0.1%]	19

Bootstrap: 761.979s -> 763.313s (0.18%)
Artifact size: 365.07 MiB -> 365.10 MiB (0.01%)

[nnethercote]

I think it's worth doing this for the small improvements on real-world code, which outweigh the weird regression on one artificial stress test.