On Tue, Jan 13, 2015 at 03:17:08PM -0700, Jeff Law wrote:
> >And finally there is the case of non-volatile asm with "memory" clobber
> >with
> >no memory stores in between the two - the posted (safer) patch will not
> >allow to CSE the two, while in theory we could CSE them into just one asm.
> I think we have to assume that CSEing them is wrong. The first may set
> something in memory that is read by the second.
>
> Thoughts?
I agree with pretty much everything you say in the thread, except for this
idea that a memory clobber reads memory. No clobber reads anything.
The commit that introduced the memory clobber concept, 426b38c9 (svn 1207),
by rms, has as only comment
/* `memory', don't cache memory across asm */
Segher
