Re: cmpxchg and x86 flags output

[H. Peter Anvin]

On 06/21/16 02:06, David Howells wrote:
> 
> However, there's probably not a great deal of difference to be had if the
> inline asm codes the appropriate instruction in each case for something like
> x86*.  The emitted code ought to look the same.  The second biggest win for
> the intriniscs, I think, is the ability to ask the CMPXCHG instruction whether
> it actually did anything rather than comparing the result.  I added two
> variants, one that only returned the yes/no and one that passed back the value
> as well as the yes/no.
> 

Right, and we want that either way.  The API change that you are
proposing is definitely what we want; the specifics of the x86
implementation is sort of orthogonal.

	-hpa