[Bug target/122018] x86 doesn't use BTS bitmanip instruction to both set and test bit

[uis9936 at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=122018

--- Comment #12 from uis <uis9936 at gmail dot com> ---
Created attachment 65215
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=65215&action=edit
Mark clobber of only flag that gets changed

The patch was sitting on my disk for a year now. It does not address the
problem, but it should a step in the right direction. When I tried replacing
clobber CCC with set CCC pattern from bt instruction it somehow got worse. By
replacing clobber CC with more precise clobber CCC it should allow for better
instruction scheduling and less potential spilling.