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hash/crc32: improve performance of ppc64SlicingUpdateBy8 on ppc64le

Browse source 
Reduce the number of instructions in the short loop of
ppc64SlicingUpdateBy8 function by combining MOVWZ and SRD into a SRD
with appropriate parameters performing the same operation and remove
MOVWZ R7,R7 from the loop
This change produces the following improvements on POWER9. None of the
other tests regress. Improvments on other POWERPC platforms similar.

name                                     old time/op    new time/op
delta

CRC32/poly=IEEE/size=15/align=0            80.5ns ± 0%    70.6ns ± 0%
-12%
CRC32/poly=IEEE/size=15/align=1            80.5ns ± 0%    70.6ns ± 0%
-12%
CRC32/poly=IEEE/size=512/align=1            151ns ± 0%     139ns ± 0%
-7%
CRC32/poly=IEEE/size=1kB/align=1            167ns ± 0%     155ns ± 0%
-7%
CRC32/poly=Castagnoli/size=15/align=0      80.2ns ± 0%    70.5ns ± 0%
-12%
CRC32/poly=Castagnoli/size=15/align=1      80.2ns ± 0%    70.5ns ± 0%
-12%
CRC32/poly=Castagnoli/size=512/align=1      150ns ± 0%     139ns ± 0%
-7%
CRC32/poly=Castagnoli/size=1kB/align=1      166ns ± 0%     155ns ± 0%
-6%

Change-Id: I424709041c30d1c637b595d0845e3ae78dc3e0a0
Reviewed-on: https://go-review.googlesource.com/c/go/+/350989
Reviewed-by: Lynn Boger <laboger@linux.vnet.ibm.com>
Reviewed-by: Cherry Mui <cherryyz@google.com>
Run-TryBot: Lynn Boger <laboger@linux.vnet.ibm.com>
TryBot-Result: Go Bot <gobot@golang.org>
This commit is contained in:
Archana R 2021-09-19 23:50:02 -05:00 committed by Lynn Boger
parent 74ba70be68
commit e128749be8
1 changed files with 2 additions and 4 deletions
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6
src/hash/crc32/crc32_ppc64le.s
View file

@ -112,19 +112,17 @@ loop:
ANDCC $7,R6,R8 // any leftover bytes
BEQ done // none --> done
MOVD R8,CTR // byte count
PCALIGN $16 // align short loop
short:
MOVBZ 0(R5),R8 // get v
MOVBZ R7,R9 // byte(crc) -> R8 BE vs LE?
MOVWZ R7,R14
SRD $8,R14,R14 // crc>>8
SRD $8,R7,R14 // crc>>8
XOR R8,R9,R8 // byte(crc)^v -> R8
ADD $1,R5 // ptr to next v
SLD $2,R8 // convert index-> bytes
ADD R8,R4,R9 // &tab[byte(crc)^v]
MOVWZ 0(R9),R10 // tab[byte(crc)^v]
XOR R10,R14,R7 // loop crc in R7
MOVWZ R7,R7 // 32 bits
BC 16,0,short
done:
NOR R7,R7,R7 // ^crc