Messages in this thread | | | Subject | Re: [PATCH v5 3/3] powerpc/lib: optimise PPC32 memcmp | From | Christophe LEROY <> | Date | Wed, 30 May 2018 10:47:48 +0200 |
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Le 29/05/2018 à 22:03, Mathieu Malaterre a écrit : > On Mon, May 28, 2018 at 12:49 PM, Christophe Leroy > <christophe.leroy@c-s.fr> wrote: >> 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 <christophe.leroy@c-s.fr> >> --- >> 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
> >> 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 >>
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