Cache non-exhaustive separately from attributes

[Mark-Simulacrum]

This prevents cross-crate attribute loading from metadata just for non_exhaustive checking; cross-crate attribute loading implies disk reading and is relatively slow.

[rust-highfive]

r? @lcnr

(rust_highfive has picked a reviewer for you, use r? to override)

[Mark-Simulacrum]

r? @petrochenkov perhaps

@bors try @rust-timer queue

Locally this is a 2-3% performance win on the smaller crates.

[rust-timer]

Awaiting bors try build completion

[bors]

⌛ Trying commit e0fb1d8781bffcf6e4b691f16a781e31b24a1318 with merge 554bc32d7285b816c134bbb13ccde3771cb3987a...

[petrochenkov]

Implementation LGTM, waiting on perf.

[bors]

☀️ Try build successful - checks-actions, checks-azure
Build commit: 554bc32d7285b816c134bbb13ccde3771cb3987a (554bc32d7285b816c134bbb13ccde3771cb3987a)

[rust-timer]

Queued 554bc32d7285b816c134bbb13ccde3771cb3987a with parent 7b3a781, future comparison URL.

[rust-timer]

Finished benchmarking try commit (554bc32d7285b816c134bbb13ccde3771cb3987a): comparison url.

Benchmarking this pull request likely means that it is perf-sensitive, so we're automatically marking it as not fit for rolling up. Please note that if the perf results are neutral, you should likely undo the rollup=never given below by specifying rollup- to bors.

Importantly, though, if the results of this run are non-neutral do not roll this PR up -- it will mask other regressions or improvements in the roll up.

@bors rollup=never

[Mark-Simulacrum]

Seems like a clear, if small, win.

@bors r=petrochenkov rollup=never

I suspect it would be good to do this for all other attribute loading, but that can be done in follow-up PRs. I think ideally we want to convert all meaningful attributes into bit flags or so rather than iterating arrays to check for presence.

[bors]

📌 Commit 13ad232 has been approved by petrochenkov

[bors]

⌛ Testing commit 13ad232 with merge 10c3757...

[bors]

☀️ Test successful - checks-actions, checks-azure
Approved by: petrochenkov
Pushing 10c3757 to master...

[Mark-Simulacrum]

This was a small perf improvement, as expected.