On 2020-08-27 11:09, Uros Bizjak wrote: > xorl %0,%0 is equivalent to xorq %0,%0 as both will zero the > entire register. Use xorl %0,%0 for all operand sizes to avoid > REX prefix byte when legacy registers are used and to avoid size > prefix byte when 16bit registers are used. > > Zeroing the full register is OK in this use case. xorl %0,%0 also > breaks register dependency chains, avoiding potential partial > register stalls with 8 and 16bit operands. > > The patch lowers the size of .fixup section by 20 bytes. > > Changes since v1: > - Rewrite commit message. > > Signed-off-by: Uros Bizjak <ubiz...@gmail.com> > Cc: Thomas Gleixner <t...@linutronix.de> > Cc: Ingo Molnar <mi...@redhat.com> > Cc: Borislav Petkov <b...@alien8.de> > Cc: "H. Peter Anvin" <h...@zytor.com>
Reviewed-by: H. Peter Anvin (Intel) <h...@zytor.com>
