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powerpc/32: Optimise __csum_partial()

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Improve __csum_partial by interleaving loads and adds.

On a 8xx, it brings neither improvement nor degradation.
On a 83xx, it brings a 25% improvement.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
Reviewed-by: Segher Boessenkool <segher@kernel.crashing.org>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Christophe Leroy 2018-05-24 11:22:27 +00:00 committed by Michael Ellerman
parent 1128bb7813
commit 373e098e1e
1 changed files with 12 additions and 3 deletions
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15
arch/powerpc/lib/checksum_32.S
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@ -47,16 +47,25 @@ _GLOBAL(__csum_partial)
bdnz 2b
21: srwi. r6,r4,4 /* # blocks of 4 words to do */
beq 3f
lwz r0,4(r3)
mtctr r6
22: lwz r0,4(r3)
lwz r6,8(r3)
lwz r7,12(r3)
lwzu r8,16(r3)
adde r5,r5,r0
lwz r7,12(r3)
adde r5,r5,r6
lwzu r8,16(r3)
adde r5,r5,r7
bdz 23f
22: lwz r0,4(r3)
adde r5,r5,r8
lwz r6,8(r3)
adde r5,r5,r0
lwz r7,12(r3)
adde r5,r5,r6
lwzu r8,16(r3)
adde r5,r5,r7
bdnz 22b
23: adde r5,r5,r8
3: andi. r0,r4,2
beq+ 4f
lhz r0,4(r3)