[PATCH 7/9] powerpc32: optimise csum_partial() loop
From: Christophe Leroy <hidden>
Date: 2015-09-22 14:35:50
Also in:
lkml, netdev
Subsystem:
linux for powerpc (32-bit and 64-bit), the rest · Maintainers:
Madhavan Srinivasan, Michael Ellerman, Linus Torvalds
On the 8xx, load latency is 2 cycles and taking branches also takes 2 cycles. So let's unroll the loop. This patch improves csum_partial() speed by around 10% on both: * 8xx (single issue processor with parallele execution) * 83xx (superscalar 6xx processor with dual instruction fetch and parallele execution) Signed-off-by: Christophe Leroy <redacted> --- 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 9c12602..0d34f47 100644
--- a/arch/powerpc/lib/checksum_32.S
+++ b/arch/powerpc/lib/checksum_32.S@@ -38,10 +38,24 @@ _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: lwz r0,4(r3) + lwz r6,8(r3) + lwz r7,12(r3) + lwzu r8,16(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