On Tue, May 22, 2018 at 08:57:01AM +0200, Christophe Leroy wrote: > The generic csum_ipv6_magic() generates a pretty bad result
<snip> Please try with a more recent compiler, what you used is pretty ancient. It's not like recent compilers do great on this either, but it's not *that* bad anymore ;-) > --- a/arch/powerpc/lib/checksum_32.S > +++ b/arch/powerpc/lib/checksum_32.S > @@ -293,3 +293,36 @@ dst_error: > EX_TABLE(51b, dst_error); > > EXPORT_SYMBOL(csum_partial_copy_generic) > + > +/* > + * static inline __sum16 csum_ipv6_magic(const struct in6_addr *saddr, > + * const struct in6_addr *daddr, > + * __u32 len, __u8 proto, __wsum sum) > + */ > + > +_GLOBAL(csum_ipv6_magic) > + lwz r8, 0(r3) > + lwz r9, 4(r3) > + lwz r10, 8(r3) > + lwz r11, 12(r3) > + addc r0, r5, r6 > + adde r0, r0, r7 > + adde r0, r0, r8 > + adde r0, r0, r9 > + adde r0, r0, r10 > + adde r0, r0, r11 > + lwz r8, 0(r4) > + lwz r9, 4(r4) > + lwz r10, 8(r4) > + lwz r11, 12(r4) > + adde r0, r0, r8 > + adde r0, r0, r9 > + adde r0, r0, r10 > + adde r0, r0, r11 > + addze r0, r0 > + rotlwi r3, r0, 16 > + add r3, r0, r3 > + not r3, r3 > + rlwinm r3, r3, 16, 16, 31 > + blr > +EXPORT_SYMBOL(csum_ipv6_magic) Clustering the loads and carry insns together is pretty much the worst you can do on most 32-bit CPUs. Segher
