[Buildroot] [PATCH 1/2] powerpc/spe: tweak glibc/eglibc/uclibc combinations

Thomas Petazzoni thomas.petazzoni at free-electrons.com
Thu Sep 11 20:57:15 UTC 2014


Dear Gustavo Zacarias,

On Thu, 11 Sep 2014 08:56:31 -0300, Gustavo Zacarias wrote:
> Since (e)glibc 2.19+ PowerPC SPE changed ABI conventions for sanity.
> In the good old days hard-float was used, it sounds good on paper until
> you account for the e500v1/v2 differences, with v1 being a fpu that does
> only single-precision math.
> 
> So the ABI changed to make it soft-float and the libc (or libm) handle
> that deficiency in software if required, making old precompiled binaries
> incompatible (of no concern for buildroot since we've got no precompiled
> binary blobs for SPE in packages).

I'm not sure to fully understand: is PowerPC really using *soft-float*
as in all floating point operations are emulated in software? Or is it
a difference similar to the difference between hardfp and softfp on ARM
(both use the FPU and floating point instructions, it's only a
different ABI, where hardfp passes floating point arguments in floating
point registers, while softfp passes floating point arguments in
integer registers).

Thanks,

Thomas
-- 
Thomas Petazzoni, CTO, Free Electrons
Embedded Linux, Kernel and Android engineering
http://free-electrons.com


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