[PATCH v3 2/2] powerpc: add support for csum_add()
scottwood at freescale.com
Wed May 27 05:42:35 AEST 2015
On Tue, 2015-05-26 at 13:57 +0000, David Laight wrote:
> From: Scott Wood ...
> > > I'd also have thought that the 64bit C version above would be
> > > generally 'good'.
> > It doesn't generate the addc/addze sequence. At least with GCC
> > 4.8.2,
> > it does something like:
> > mr tmp0, csum
> > li tmp1, 0
> > li tmp2, 0
> > addc tmp3, addend, tmp0
> > adde csum, tmp2, tmp1
> > add csum, csum, tmp3
> I was thinking of all 64bit targets, not 32bit ones.
Oh, you mean move it out of arch/powerpc? Sounds reasonable, but
someone should probably check what the resulting code looks like on
other common arches. OTOH, if we're going to modify non-arch code,
that might be a good opportunity to implement Segher's suggestion and
move to a 64-bit accumulator.
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