lkml.org 
[lkml]   [2018]   [May]   [24]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [PATCH v3] powerpc: Implement csum_ipv6_magic in assembly
From
Date


Le 23/05/2018 à 20:34, Segher Boessenkool a écrit :
> 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.

Oh, really ? __csum_partial is written that way too.

Right, now I tried interleaving the lwz and adde. I get no improvment at
all on a 885, but I get a 15% improvment on a 8321.

Christophe

>
>
> Segher
>

\
 
 \ /
  Last update: 2018-05-24 08:20    [W:0.076 / U:0.536 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site