The VPCMP instructions are controlled by an immediate byte, but there
is also a set of SSE-derived legacy opcodes for VPCMPEQ and
VPCMPGT. For the specific cases of VPCMPEQ and VPCMPGT, prefer those
opcodes since they are one byte shorter.
Reported-by: ig <glucksmann@avast.com>
Signed-off-by: H. Peter Anvin (Intel) <hpa@zytor.com>