Re: libffi: Simplify PowerPC assembly and avoid CPU-specific string instructions

[Anthony Green <green at moxielogic dot com>]

On 11/1/2011 4:55 PM, Moffett, Kyle D wrote:
> On Nov 01, 2011, at 11:53, Kyle Moffett wrote:
> > After upgrading to a new version of GNU ld for PowerPC e500, I started
> > seeing build errors on e500 systems again.  It turns out that the
> > PowerPC "string instructions" are unimplemented on PPC440 and most other
> > embedded cores, and also cause unexpectedly high instruction latencies
> > and pipeline stalls even on POWER processors.
> >
> > This historically worked in the past because the unknown string opcodes
> > are trapped on PPC440 and similar systems and emulated in the kernel,
> > though that is obviously very inefficient and undesirable.
> >
> > Since the struct-copy code doesn't really need to be implemented in
> > assembly, this patch ensures that there is always enough space to store
> > both r3 and r4 and then uses C to extract the 1-8 byte "small struct"
> > into the user-provided memory.
> >
> > Even with all the big new comments, it's still removes 11 lines of code,
> > and the ASM is much simpler and easier to understand now.
> >
> > Please consider applying.


I like this patch, and have applied it after a minor tweak (cache 
cif->rtype->size in a local var to avoid multiple accesses).

Thanks!

AG