Re: [PING] for 4.3 patches

[Roger Sayle <roger at eyesopen dot com>]

Hi Uros,

On Tue, 14 Nov 2006, Uros Bizjak wrote:
> >>2) [PATCH, i386]: Implement x87 register passing convention:
> >>http://gcc.gnu.org/ml/gcc-patches/2006-10/msg00696.html
> >>
> >
> >If it's OK with you, I'd like to wait a little while for stage 1 to calm
> >down a bit before approving your x87 register passing convention patch?
> >With Honza and Richi's i386 backend patches currently going in, I hope
> >you don't mind waiting a week or so, for this larger change of yours to
> >be queued.  There may even be pending branch merges.

Sure.  Sorry for the delay.

This is mostly OK for mainline.

The one part I think I would like to see changed though, is the
influence of -ffast-math on the ABI.  I think that for externally
visible global scope functions we either select the x87 API or
the SSE API for parameter passsing, and stick to it.  Now that this
is an attribute, we can even set it on a function by function basis.
The optimization level and the affect flag_unsafe_math_optimizations
should be irrelevant.  Fortunately, for local static functions we
can choose arbitrarily, as we can do for integer register passing
conventions, and this internal change may be passed upon -ffast-math
or -ffancy-math-387 or eventually (in an ideal world) the preferences
selected by the register allocator.

I just think its a bit beyond my comfort zone to disallow -ffast-math
executables to be linked to non -ffast-math libraries and vice/versa.
Adding the attribute however is an excellent idea.

Any chance I could ask you to isolate this controversial aspect of
your patch and propose it separately?


Not sure if anyone has given it any thought, but in theory it may
eventually be possible to call and link to legacy 32-bit libraries
by suitably marking the API points with a suitable attribute?


Sorry to be a pain.  Was there a strong reason to control this via
-funsafe-math-optimizations?  If we really need to differentiate
an XFmode x87 vs a SF/DF/XFmode x87 then we probably need another
attribute, command line option or -mabi option.

Roger
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