[Bug target/86314] [7/8/9 Regression] GCC 7.x and 8.x zero out "eax" before using "rax" in "lock bts"

[jakub at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=86314

--- Comment #4 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
Created attachment 44322
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=44322&action=edit
gcc9-pr86314.patch

Untested fix.  The peephole2s didn't expect that an insn with a set of flags
and some other set could use the reg it wants to clear inside of the lhs of the
second set.