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

Gustavo Zacarias gustavo at zacarias.com.ar
Thu Sep 11 21:45:09 UTC 2014


On 09/11/2014 05:57 PM, Thomas Petazzoni wrote:

> 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).

It's similar to the ARM scenario, yes.
In the SPE ABI there are no FPU registers at all, it's just an extension
of GP-ones (say 32+32 bit for DP/E500v2).
In libc-land uclibc uses the 'old' ABI (direct hard float), and so did
eglibc <= 2.18 (glibc i think never got that part officially).
To avoid re-explaining: http://www.eglibc.org/archives/patches/msg01291.html
I hope it's clear enough :)
Regards.



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