See exchange of messages on the gcc mailing list (archives at
http://gcc.gnu.org/ml/gcc/ .
Paul says "You lose". However, that is based on limited information.
Here are the answers I got, combined :
By Dave Korn :
> You should mention that long double alignment macro that the guy on
> the
> cegcc list thought it was connected with. ARM_DOUBLEWORD_ALIGN. If I
> was
> following that discussion correctly, the ABI requires it, and you have
> it
> #defined to zero to fix the problem you were getting with float double
> function argument passing, but maybe what this means is that it
> there's some
> more fundamental problem in the ABI-related MD macros, that fixing it
> this way
> ended up just papering over.
By Paul Brook, answer #1 :
> Both. By my reading the ABI you're trying to implement does not
> provide the
> guarantees required to use iwmmxt instructions. There are ways around
> this,
> but none of them are simple or pretty. The simplest answer is "don't
> do that".
By Paul Brook, answer #2 :
> iwmmxt instructions require doubleword data alignment . Your target
> [apparently] can't provide that. You loose.
Does anyone feel like looking up what we can do to provide the right
environment ?
Is it possible to implement this in the current compiler, or would this
require a completely new target (e.g. an iwmmx-mingw32ce-gcc) ?
Thanks,
Danny
--
Danny Backx ; danny.backx - at - scarlet.be ; http://danny.backx.info
--- Begin Message ---
> > Both. By my reading the ABI you're trying to implement does not provide
> > the guarantees required to use iwmmxt instructions. There are ways around
> > this, but none of them are simple or pretty. The simplest answer is
> > "don't do that".
>
> Hi Paul,
>
> Thanks for the answer, but I'm not sure what you've told me and why.
> Could you expand a little ?
>
> Don't do what ? Use WMMX instructions in GCC ?
> or
> Don't try to use the current implementation with WMMX ?
iwmmxt instructions require doubleword data alignment . Your target
[apparently] can't provide that. You loose.
Paul
--- End Message ---
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