Le 29/05/2018 à 22:03, Mathieu Malaterre a écrit :

On Mon, May 28, 2018 at 12:49 PM, Christophe Leroy
[off-list ref] wrote:

quoted

At the time being, memcmp() compares two chunks of memory
byte per byte.

This patch optimises the comparison by comparing word by word.

A small benchmark performed on an 8xx comparing two chuncks
of 512 bytes performed 100000 times gives:

Before : 5852274 TB ticks
After:   1488638 TB ticks

This is almost 4 times faster

Signed-off-by: Christophe Leroy <redacted>
---
  arch/powerpc/lib/string_32.S | 37 +++++++++++++++++++++++++++----------
  1 file changed, 27 insertions(+), 10 deletions(-)

Would it possible for you to move the actual code instead to:

./arch/powerpc/lib/memcmp_32.S

This will seat right next to memcmp_64.S implementation.

Good idea, thanks.
Done in v6

Christophe

quoted

diff --git a/arch/powerpc/lib/string_32.S b/arch/powerpc/lib/string_32.S
index 40a576d56ac7..4fbaa046aa84 100644
--- a/arch/powerpc/lib/string_32.S
+++ b/arch/powerpc/lib/string_32.S

@@ -16,17 +16,34 @@
         .text

  _GLOBAL(memcmp)
-       cmpwi   cr0, r5, 0
-       beq-    2f
-       mtctr   r5
-       addi    r6,r3,-1
-       addi    r4,r4,-1
-1:     lbzu    r3,1(r6)
-       lbzu    r0,1(r4)
-       subf.   r3,r0,r3
-       bdnzt   2,1b
+       srawi.  r7, r5, 2               /* Divide len by 4 */
+       mr      r6, r3
+       beq-    3f
+       mtctr   r7
+       li      r7, 0
+1:     lwzx    r3, r6, r7
+       lwzx    r0, r4, r7
+       addi    r7, r7, 4
+       cmplw   cr0, r3, r0
+       bdnzt   eq, 1b
+       bne     5f
+3:     andi.   r3, r5, 3
+       beqlr
+       cmplwi  cr1, r3, 2
+       blt-    cr1, 4f
+       lhzx    r3, r6, r7
+       lhzx    r0, r4, r7
+       addi    r7, r7, 2
+       subf.   r3, r0, r3
+       beqlr   cr1
+       bnelr
+4:     lbzx    r3, r6, r7
+       lbzx    r0, r4, r7
+       subf.   r3, r0, r3
         blr
-2:     li      r3,0
+5:     li      r3, 1
+       bgtlr
+       li      r3, -1
         blr
  EXPORT_SYMBOL(memcmp)

--

2.13.3