Remove new allocations from imported_source_files

[emilyalbini]

#97786 introduced a large performance regression. After some local investigation it turns out the allocations performed by my change were the cause of the perf regression. This PR refactors my change to remove those allocations.

[rust-highfive]

r? @wesleywiser

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

[emilyalbini]

@bors try @rust-timer queue

[rust-timer]

Awaiting bors try build completion.

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

[bors]

⌛ Trying commit f1063c0 with merge 5e5328706d3f8b491737daaf05f020e9fce2cc27...

[Mark-Simulacrum]

r=me on the changes presuming perf looks good

[bors]

☀️ Try build successful - checks-actions
Build commit: 5e5328706d3f8b491737daaf05f020e9fce2cc27 (5e5328706d3f8b491737daaf05f020e9fce2cc27)

[rust-timer]

Queued 5e5328706d3f8b491737daaf05f020e9fce2cc27 with parent b4151a4, future comparison URL.

[rust-timer]

Finished benchmarking commit (5e5328706d3f8b491737daaf05f020e9fce2cc27): comparison url.

Instruction count

• Primary benchmarks: 🎉 relevant improvements found
• Secondary benchmarks: 🎉 relevant improvements found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	-1.5%	-9.8%	125
Improvements 🎉 (secondary)	-3.8%	-9.9%	60
All 😿🎉 (primary)	-1.5%	-9.8%	125

Max RSS (memory usage)

Results

• Primary benchmarks: no relevant changes found
• Secondary benchmarks: mixed results

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	3.4%	4.9%	6
Improvements 🎉 (primary)	N/A	N/A	0
Improvements 🎉 (secondary)	-2.1%	-2.1%	2
All 😿🎉 (primary)	N/A	N/A	0

Cycles

Results

• Primary benchmarks: 🎉 relevant improvements found
• Secondary benchmarks: 🎉 relevant improvements found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	2.2%	2.2%	1
Improvements 🎉 (primary)	-3.3%	-7.4%	19
Improvements 🎉 (secondary)	-5.3%	-7.5%	27
All 😿🎉 (primary)	-3.3%	-7.4%	19

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

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

Footnotes

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

2. number of relevant changes ↩ ↩² ↩³

[emilyalbini]

Ok the change seems to have resolved the performance regression (how many times is that function called to cause 3 allocations to have such impact?).

@bors r=Mark-Simulacrum rollup=never

[bors]

📌 Commit f1063c0 has been approved by Mark-Simulacrum

It is now in the queue for this repository.

[Kobzol]

(how many times is that function called to cause 3 allocations to have such impact?).

Just did a quick experiment, while compiling the clap crate (from scratch, so with all its dependencies), it gets called about a million times.

[bors]

⌛ Testing commit f1063c0 with merge 96b9bb4...

[bors]

☀️ Test successful - checks-actions
Approved by: Mark-Simulacrum
Pushing 96b9bb4 to master...

[rust-timer]

Finished benchmarking commit (96b9bb4): comparison url.

Instruction count

• Primary benchmarks: 🎉 relevant improvements found
• Secondary benchmarks: 🎉 relevant improvements found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	-1.5%	-9.9%	132
Improvements 🎉 (secondary)	-3.2%	-9.8%	77
All 😿🎉 (primary)	-1.5%	-9.9%	132

Max RSS (memory usage)

Results

• Primary benchmarks: 🎉 relevant improvement found
• Secondary benchmarks: mixed results

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	3.6%	4.1%	3
Improvements 🎉 (primary)	-2.5%	-2.5%	1
Improvements 🎉 (secondary)	-2.2%	-2.5%	3
All 😿🎉 (primary)	-2.5%	-2.5%	1

Cycles

Results

• Primary benchmarks: 🎉 relevant improvements found
• Secondary benchmarks: 🎉 relevant improvements found

	mean1	max	count2
Regressions 😿 (primary)	N/A	N/A	0
Regressions 😿 (secondary)	N/A	N/A	0
Improvements 🎉 (primary)	-3.5%	-7.7%	16
Improvements 🎉 (secondary)	-5.1%	-7.4%	27
All 😿🎉 (primary)	-3.5%	-7.7%	16

If you disagree with this performance assessment, please file an issue in rust-lang/rustc-perf.

@rustbot label: -perf-regression

Footnotes

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

2. number of relevant changes ↩ ↩² ↩³