On Wed, Sep 26, 2012 at 10:34 AM, Ondřej Bílka <neleai@seznam.cz> wrote: > is there a reason why for example > x=x|(1<<11); > is not expanded into > bts rax,11 > ? The bts instruction is never faster than the corresponding or instruction. There's no reason to use it when setting a bit in the low 32 bits. Ian