Shorten the lookup_line code slightly

[scottmcm]

The match looks like it's exactly the same as checked_sub(1), so we might as well see if perf says we can just do that to save a couple lines.

[rust-highfive]

r? @jackh726

(rust-highfive has picked a reviewer for you, use r? to override)

[scottmcm]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

@rustbot label: +S-waiting-on-perf

[bors]

⌛ Trying commit 0fd3bbe with merge feae6b8d13b53cf7444ecb1e85b69b6d53b55e79...

[bors]

☀️ Try build successful - checks-actions
Build commit: feae6b8d13b53cf7444ecb1e85b69b6d53b55e79 (feae6b8d13b53cf7444ecb1e85b69b6d53b55e79)

[rust-timer]

Queued feae6b8d13b53cf7444ecb1e85b69b6d53b55e79 with parent de341fe, future comparison URL.

[rust-timer]

Finished benchmarking commit (feae6b8d13b53cf7444ecb1e85b69b6d53b55e79): 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-review -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.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.4%	[0.4%, 0.4%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
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.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	3.2%	[2.8%, 3.5%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

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.

	mean1	range	count2
Regressions ❌ (primary)	3.2%	[3.2%, 3.2%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	3.2%	[3.2%, 3.2%]	1

Footnotes

1. the arithmetic mean of the percent change ↩ ↩² ↩³

2. number of relevant changes ↩ ↩² ↩³

[jackh726]

@bors r+

[bors]

📌 Commit 0fd3bbe has been approved by jackh726

It is now in the queue for this repository.

[bors]

⌛ Testing commit 0fd3bbe with merge 4b5fcae...

[bors]

☀️ Test successful - checks-actions
Approved by: jackh726
Pushing 4b5fcae to master...

[rust-timer]

Finished benchmarking commit (4b5fcae): comparison URL.

Overall result: ❌ regressions - no action needed

@rustbot label: -perf-regression

Instruction count

This is a highly reliable metric that was used to determine the overall result at the top of this comment.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	0.1%	[0.1%, 0.1%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
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.

	mean1	range	count2
Regressions ❌ (primary)	1.1%	[1.1%, 1.1%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-2.8%	[-3.6%, -2.5%]	3
All ❌✅ (primary)	1.1%	[1.1%, 1.1%]	1

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.

	mean1	range	count2
Regressions ❌ (primary)	-	-	0
Regressions ❌ (secondary)	2.7%	[2.7%, 2.7%]	1
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Footnotes

1. the arithmetic mean of the percent change ↩ ↩² ↩³

2. number of relevant changes ↩ ↩² ↩³