[Bug target/80813] [12/13/14/15 Regression] x86: std::vector::operator[] could be somewhat faster using BT instead of SHL

[hubicka at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=80813

--- Comment #6 from Jan Hubicka <hubicka at gcc dot gnu.org> ---
Patch to optimize operator[] to be again branchless posted
https://gcc.gnu.org/pipermail/gcc-patches/2024-December/672286.html

Main problem with auto-generating bt is that it needs change of conditional
from CCZ to CCC which needs some combine trickery