Re: [PATCH 13/15] x86: add cmpxchg_flag() variant

[Linus Torvalds]

On Wed, Aug 24, 2011 at 4:04 PM, H. Peter Anvin <hpa@xxxxxxxxx> wrote:
>
>> I was also thinking that using it reduces register pressure, since you
>> don't need to keep the "old" value around, so it dies sooner.
>
> ... but you burn a register for the intermediate flag value, so you're
> just as bad off.

But that register has much shorter liveness - so I do agree that it *can* help.

Whether it actually *does* help is unclear. I do agree that we might
be better off without introducing yet another (questionable)
interface.

                     Linus
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