Re: [PATCH v3] powerpc: Implement csum_ipv6_magic in assembly
From: Segher Boessenkool <hidden>
Date: 2018-05-24 19:43:02
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On Thu, May 24, 2018 at 08:20:16AM +0200, Christophe LEROY wrote:
Le 23/05/2018 à 20:34, Segher Boessenkool a écrit :quoted
On Tue, May 22, 2018 at 08:57:01AM +0200, Christophe Leroy wrote:quoted
+_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.
I thought I told you about this before? Maybe not.
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.
It won't likely help on single-issue cores (like the one 885 has), yes. Segher