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Re: ABI voilation
- From: Dorit Nuzman <DORIT at il dot ibm dot com>
- To: Andrew Haley <aph-gcc at littlepinkcloud dot COM>
- Cc: gcc-help at gcc dot gnu dot org, kanishk rastogi <kanishk dot 85 at gmail dot com>, Tim Prince <tprince at computer dot org>
- Date: Tue, 9 Oct 2007 00:31:18 -0800
- Subject: Re: ABI voilation
> Tim Prince writes:
> > kanishk rastogi wrote:
> > > hi all,
> > > I wanted to know if when i specify -O[0-3] flag to gcc does gcc
> > > optimize the code even violating ABI for that specific arch.
> > > If yes can i specify gcc not to violate the ABI ....
> > > I am mostly concerned witht he ABI specification which tells how to
> > > call another function..
> > >
> >
> > Only the -Os changes the value of -mpreferred-stack-boundary, breaking
> > the ability to support vectorization or other alignment dependent code
> > in the callee.
>
> -Os breaks vectorization? That would be A Bug, for sure. Do you have
> references, Bugzilla entries, for this?
>
I don't think -mpreferred-stack-boundary breaks vectorization, but it can
affect vectorization because vectorization is sensitive to alignment, and
the ability to force the alignment of arrays on the stack currently depends
on the preferred stack boundary. You can see
http://gcc.gnu.org/ml/gcc-patches/2007-10/msg00202.html for more details.
dorit
> Andrew.