Removed dependency on the field-offset crate.

[davidv1992]

This touches the core of the query system, should be evaluated carefully for performance.

[rustbot]

r? @Mark-Simulacrum

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[rustbot]

These commits modify the Cargo.lock file. Unintentional changes to Cargo.lock can be introduced when switching branches and rebasing PRs.

If this was unintentional then you should revert the changes before this PR is merged.
Otherwise, you can ignore this comment.

[bjorn3]

This was spawned from #135870 (comment). The field-offset crate doesn't work with strict provenance, which miri forces when using tree borrows.

@bors try @rust-timer queue

[bors]

⌛ Trying commit 2681c12 with merge 84dc1fa...

[bors]

💔 Test failed - checks-actions

[bjorn3]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 5fd7599 with merge 4405608...

[rustbot]

The list of allowed third-party dependencies may have been modified! You must ensure that any new dependencies have compatible licenses before merging.

cc @davidtwco, @wesleywiser

[davidv1992]

@rustbot ready

[clubby789]

@bors try @rust-timer queue

[bors]

⌛ Trying commit 4efb1b1 with merge 09d1d97...

[bors]

☀️ Try build successful - checks-actions
Build commit: 09d1d97 (09d1d9737e9dbfb5a92ebd468721f4589b6e8454)

[rust-timer]

Finished benchmarking commit (09d1d97): comparison URL.

Overall result: ❌ regressions - 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%	[0.1%, 0.5%]	11
Regressions ❌ (secondary)	0.3%	[0.1%, 0.5%]	29
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	0.2%	[0.1%, 0.5%]	11

Max RSS (memory usage)

Results (primary 2.8%)

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%	[2.8%, 2.8%]	1
Regressions ❌ (secondary)	-	-	0
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	2.8%	[2.8%, 2.8%]	1

Cycles

Results (secondary 2.8%)

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)	2.8%	[2.6%, 2.9%]	2
Improvements ✅ (primary)	-	-	0
Improvements ✅ (secondary)	-	-	0
All ❌✅ (primary)	-	-	0

Binary size

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

Bootstrap: 771.063s -> 769.268s (-0.23%)
Artifact size: 325.77 MiB -> 325.97 MiB (0.06%)

[davidv1992]

Hmmm, not entirely sure what causes the RSS size increase, that one feels weird to me. However, the increase in instruction count is less than I would have expected, given that this replaces a most likely inlineable function with an indirect function call. I feel the advantages of completely avoiding unsafe code and reducing the dependency list by two dependencies here are worth it.

However if this is deemed too large a regression I can also build a second approach that directly uses offset calculations. That would involve unsafe code but would still eliminate the dependency and removes the need for the indirect function call.

@rustbot label: +perf-regression-triaged

[Mark-Simulacrum]

My guess is that the max-rss regression on a single test case is likely spurious.

IMO, either replacing this with storing the offsets and doing the indexing with unsafe code or upstreaming strict provenance to the field offset crate would make sense. (Or both). I don't think there's much value in regressing here -- especially given the ~150kb of code this seems to add (probably due to the tiny offset functions).

[davidv1992]

I would suggest we move away from the dependency, as it seems to be unmaintained, and even if it isn't it currently has a bus factor of 1. Given that it really is used in so few places, I think it's just not worth it to keep around. I will make a version doing the offset calculation directly later tonight (CET) so we can compare.

[Mark-Simulacrum]

Replaced by #136201.