Re: [PATCH v2] Add PowerPC soft-float support

[Rich Felker <dalias@libc.org>]

On Fri, Aug 07, 2015 at 12:47:50AM +0200, Szabolcs Nagy wrote:
> * Felix Fietkau <nbd@openwrt.org> [2015-07-10 13:02:51 +0200]:
> > Some PowerPC CPUs (e.g. Freescale MPC85xx) have a completely different
> > instruction set for floating point operations (SPE).
> > Executing regular PowerPC floating point instructions results in
> > "Illegal instruction" errors.
> > 
> > Make it possible to run these devices in soft-float mode.

I'd like to follow up on this now that the 1.1.11 release is out.
Let's try to go ahead and get it in on the musl side while we try to
get the gcc patches tweaked and upstream...

> thanks, this looks good
> 
> i used
> 
> #define MUSL_DYNAMIC_LINKER \
>   "/lib/ld-musl-powerpc" MUSL_DYNAMIC_LINKER_E "%{msoft-float:-sf}.so.1"
> 
> in gcc to get a soft float toolchain.
> (MUSL_DYNAMIC_LINKER_E is "le" on little endian).
> but i'm not yet sure if -msoft-float is always passed
> down by gcc for soft float targets.
> 
> (the gcc config files are rather messy, there might be more
> ppc abi variants lurking there)
> 
> > Signed-off-by: Felix Fietkau <nbd@openwrt.org>
> > ---
> >  arch/powerpc/reloc.h              |  8 ++++++-
> >  configure                         |  4 ++++
> >  src/fenv/powerpc-sf/fenv.sub      |  1 +
> 
> this is not enough for fenv.
> 
> unsupported FE_* macros must be hidden in arch/powerpc/bits/fenv.h
> (see e.g. how arm does it), exceptions and non-nearest rounding
> are not supported for soft float.
> 
> the rest looks ok to me.

Felix, do you have patches for fenv.h?

Rich