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List:       gcc
Subject:    Re: Problems with pragma and attribute optimize.
From:       Allan Sandfeld Jensen <carewolf () gmail ! com>
Date:       2012-07-30 14:35:03
Message-ID: 201207301635.03820.linux () carewolf ! com
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On Wednesday 25 July 2012, Richard Guenther wrote:
> On Wed, Jul 25, 2012 at 4:25 PM, Allan Sandfeld Jensen
> 
> <carewolf@gmail.com> wrote:
> > On Wednesday 25 July 2012, Richard Guenther wrote:
> >> On Wed, Jul 25, 2012 at 2:23 PM, Allan Sandfeld Jensen
> >> 
> >> <carewolf@gmail.com> wrote:
> >> > Hi,
> >> > 
> >> > I have been experimenting with marking specific functions to be auto-
> >> > vectorized in GCC, but have had problems getting it to work.
> >> > 
> >> > It seems the optimize attribute works sometimes, but only if the
> >> > function it is used on is not static, but pragma optimize never seems
> >> > to work.
> >> > 
> >> > See the attached test-case. If you compile it with
> >> > -ftree-vectorizer-verbose, you will see that only the first function
> >> > is vectorized, but the two last are not.
> >> > 
> >> > Anyone know what is wrong here?
> >> 
> >> The attribute doesn't work in the face of inlining and generally was
> >> designed for debugging, not for controlling things like you do.
> > 
> > In that case the GCC manual should probably be updated to reflect that.
> > If what you say it true, it seems it has been developed for one purpose
> > but then documented for another. (The documentation needs updating
> > anyway, since the attribute is no longer allowed after the function
> > declaration like all the examples does, but only before).
> > 
> > I found the problem with pragma though, it is apparently a long standing
> > bug in PR 48026 and a related version in PR 41201. The last bug actually
> > has a patch for the problem, it is apparently caused by an incorrect
> > short-cut.
> 
> CCing the original author.
> 
Cool.

Anyway, for my usecase of these flags, you can see: 
https://bugs.webkit.org/show_bug.cgi?id=92249

It uses the optimize attribute currently,  because pragma didn't work, and 
forces noinline so that the attribute is not lost on inline.

`Allan
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