lkml.org 
[lkml]   [2015]   [Jun]   [30]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
From
Subject[PATCH 2/2] powerpc32: optimise csum_partial() loop
Date
On the 8xx, load latency is 2 cycles and taking branches also takes
2 cycles. So let's unroll the loop.

Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
arch/powerpc/lib/checksum_32.S | 16 +++++++++++++++-
1 file changed, 15 insertions(+), 1 deletion(-)

diff --git a/arch/powerpc/lib/checksum_32.S b/arch/powerpc/lib/checksum_32.S
index 2e4879c..9c48ee0 100644
--- a/arch/powerpc/lib/checksum_32.S
+++ b/arch/powerpc/lib/checksum_32.S
@@ -75,10 +75,24 @@ _GLOBAL(csum_partial)
srwi. r6,r4,2 /* # words to do */
adde r5,r5,r0
beq 3f
-1: mtctr r6
+1: andi. r6,r6,3 /* Prepare to handle words 4 by 4 */
+ beq 21f
+ mtctr r6
2: lwzu r0,4(r3)
adde r5,r5,r0
bdnz 2b
+21: srwi. r6,r4,4 /* # blocks of 4 words to do */
+ beq 3f
+ mtctr r6
+22: lwzu r0,4(r3)
+ lwzu r6,4(r3)
+ lwzu r7,4(r3)
+ lwzu r8,4(r3)
+ adde r5,r5,r0
+ adde r5,r5,r6
+ adde r5,r5,r7
+ adde r5,r5,r8
+ bdnz 22b
3: andi. r0,r4,2
beq+ 4f
lhz r0,4(r3)
--
2.1.0


\
 
 \ /
  Last update: 2015-06-30 16:21    [W:0.032 / U:0.208 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site