[Bug target/123894] bpf: incorrectly eliding bitfiled extraction

[vineetg at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123894

--- Comment #2 from Vineet Gupta <vineetg at gcc dot gnu.org> ---
(In reply to Andrew Pinski from comment #1)
> Confirmed. This is a specific issue with preserve_access_index. It could be
> the way preserve_access_index causes:
> MEM <<unnamed-signed:5>> [(void *)_6];

Sweet, for this test I didn't try this variation (I was mucking with bigger
tests and toggling the attr etc). Anyhow this gives me a direction to work.

> Which might be either a middle-end issue or maybe the backend should expand
> preserve_access_index accesses differently.

RISC-V codegen for same test (modulo attr) seems to be generating extraction so
likely backend related.