Nightly regressed igvm crate and now emits SIGILL at opt-level higher than 1

[durin42]

Code

I tried this code:

durin42/igvm@1880200
cargo +nightly test --release

I expected to see this happen: Tests all pass.

Instead, this happened: Tests die with a SIGILL.

Version it worked on

This works on stable, and also up until b6b8361 (merge of #133324)

Version with regression

b6b8361 breaks, aka the merge of #133324. All nightlies since then show the same behavior.

Backtrace

I don't get one, I assume because it's a crash.

bisect-rustc output:

searched nightlies: from nightly-2025-01-07 to nightly-2025-01-13
regressed nightly: nightly-2025-01-10
searched commit range: a580b5c...8247594
regressed commit: b6b8361

bisected with cargo-bisect-rustc v0.6.8

Host triple: x86_64-unknown-linux-gnu
Reproduce with:

cargo bisect-rustc --start 2025-01-07 --end 2025-01-13 -- test --release

It's plausible to me that one of the crates in here is guilty of some unsafe crimes, but I'm not sure how to prove who's at fault at this point.

@rustbot modify labels: +regression-from-stable-to-nightly -regression-untriaged

[durin42]

Update: a colleague has further reduced this to just zerocopy as a dep, and will share the sample here shortly

[AdamCDunlap]

This is a much simpler reproduction on rust playground. Note nightly and release mode must be selected for the SIGILL to occur.

https://play.rust-lang.org/?version=nightly&mode=release&edition=2021&gist=e522e9c608dea108a0a278b333523660

[lqd]

cc @scottmcm on that bisection