[RFC] Design for flag bit outputs from asms

Linus Torvalds torvalds@linux-foundation.org
Mon May 4 20:45:00 GMT 2015


On Mon, May 4, 2015 at 1:33 PM, Richard Henderson <rth@redhat.com> wrote:
>
> A fair point.  Though honestly, I was hoping that this feature would mostly be
> used for conditions that are "weird" -- that is, not normally describable by
> arithmetic at all.  Otherwise, why are you using inline asm for it?

I could easily imagine using some of the combinations for atomic operations.

For example, doing a "lock decl", and wanting to see if the result is
negative or zero. Sure, it would be possible to set *two* booleans (ZF
and SF), but there's a contiional for "BE"..

                    Linus



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