[ofiwg] allowing aliasing in fetch atomics?

Jeff Hammond jeff.science at gmail.com
Wed Nov 11 11:01:24 PST 2015

Why do memcpy and memmove both exist?  Why did C99 introduce restrict?  Why
does Fortran prohibit aliasing?

I have measured the benefits of restrict semantics w.r.t. vectorization
many times in the past, enough that I did not bother to benchmark this
specific case.


On Wed, Nov 11, 2015 at 8:02 AM, Dave Goodell (dgoodell) <dgoodell at cisco.com
> wrote:

> On Nov 11, 2015, at 9:47 AM, Jeff Hammond <jeff.science at gmail.com> wrote:
> > Is there a reason why buf and result can't be restrict pointers?  I see
> zero value in enabling the case of aliased local buffers when the side
> effects are (1) a const buffer is modified and (2) the potential code
> optimization demonstrated in my pull request is disallowed (without
> specializing the macro for the aliased and non-aliased cases, of course).
> Let's flip that around: do you have any empirical evidence that this API
> design decision is actually affecting performance in a noticeable way?  "I
> would like it to look differently, and I *think* there's optimization
> potential" is a weak argument.
> -Dave

Jeff Hammond
jeff.science at gmail.com
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