[Bug target/79709] Subobtimal code with -mavx and explicit vector

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79709

--- Comment #5 from Richard Biener <rguenth at gcc dot gnu.org> ---
Best split this bug into BIT_INSERT_EXPR foldings (yeah, those mentioned are
missing) and the ira/reload issue.