Switch from "xorq %rax, %rax" to "xorl %eax, %eax". In 64-bit mode
zeroing EAX implicitly clears RAX and the 32-bit form encodes are one
byte smaller while keeping identical semantics.
Signed-off-by: George Hu <integral@archlinux.org>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>