[PATCH] powerpc/32: Optimise __csum_partial()

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 <redacted>
---
 arch/powerpc/lib/checksum_32.S | 13 +++++++++++--
 1 file changed, 11 insertions(+), 2 deletions(-)

diff --git a/arch/powerpc/lib/checksum_32.S b/arch/powerpc/lib/checksum_32.S
index d2238ea82209..aa224069f93a 100644
--- a/arch/powerpc/lib/checksum_32.S
+++ b/arch/powerpc/lib/checksum_32.S

@@ -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)
+	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
-	adde	r5,r5,r8
 	bdnz	22b
+23:	adde	r5,r5,r8
 3:	andi.	r0,r4,2
 	beq+	4f
 	lhz	r0,4(r3)

-- 
2.13.3

On Thu, May 24, 2018 at 11:22:27AM +0000, Christophe Leroy wrote:

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.

Thanks!  Looks fine to me.

Signed-off-by: Christophe Leroy <redacted>

Reviewed-by: Segher Boessenkool <redacted>

On Thu, 2018-05-24 at 11:22:27 UTC, Christophe Leroy wrote:

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 <redacted>
Reviewed-by: Segher Boessenkool <redacted>

Applied to powerpc next, thanks.

https://git.kernel.org/powerpc/c/373e098e1e788d7b89ec0f31765a6c

cheers