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Subject[PATCH 32/43] MN10300: Optimise do_csum()
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Date
From: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>

Optimise do_csum() to gang up the loads so they're less likely to get
interruptions between.

Signed-off-by: Akira Takeuchi <takeuchi.akr@jp.panasonic.com>
Signed-off-by: Kiyoshi Owada <owada.kiyoshi@jp.panasonic.com>
Signed-off-by: David Howells <dhowells@redhat.com>
---
arch/mn10300/lib/do_csum.S | 49 ++++++++++++++++++++------------------------
1 files changed, 22 insertions(+), 27 deletions(-)

diff --git a/arch/mn10300/lib/do_csum.S b/arch/mn10300/lib/do_csum.S
index e138994..1d27bba 100644
--- a/arch/mn10300/lib/do_csum.S
+++ b/arch/mn10300/lib/do_csum.S
@@ -10,26 +10,25 @@
*/
#include <asm/cache.h>

- .section .text
- .balign L1_CACHE_BYTES
+ .section .text
+ .balign L1_CACHE_BYTES

###############################################################################
#
-# unsigned int do_csum(const unsigned char *buff, size_t len)
+# unsigned int do_csum(const unsigned char *buff, int len)
#
###############################################################################
.globl do_csum
- .type do_csum,@function
+ .type do_csum,@function
do_csum:
movm [d2,d3],(sp)
- mov d0,(12,sp)
- mov d1,(16,sp)
mov d1,d2 # count
mov d0,a0 # buff
+ mov a0,a1
clr d1 # accumulator

cmp +0,d2
- beq do_csum_done # return if zero-length buffer
+ ble do_csum_done # check for zero length or negative

# 4-byte align the buffer pointer
btst +3,a0
@@ -41,17 +40,15 @@ do_csum:
inc a0
asl +8,d0
add d0,d1
- addc +0,d1
add -1,d2
-do_csum_addr_not_odd:

+do_csum_addr_not_odd:
cmp +2,d2
bcs do_csum_fewer_than_4
btst +2,a0
beq do_csum_now_4b_aligned
movhu (a0+),d0
add d0,d1
- addc +0,d1
add -2,d2
cmp +4,d2
bcs do_csum_fewer_than_4
@@ -66,20 +63,20 @@ do_csum_now_4b_aligned:

do_csum_loop:
mov (a0+),d0
- add d0,d1
mov (a0+),e0
- addc e0,d1
mov (a0+),e1
- addc e1,d1
mov (a0+),e3
+ add d0,d1
+ addc e0,d1
+ addc e1,d1
addc e3,d1
mov (a0+),d0
- addc d0,d1
mov (a0+),e0
- addc e0,d1
mov (a0+),e1
- addc e1,d1
mov (a0+),e3
+ addc d0,d1
+ addc e0,d1
+ addc e1,d1
addc e3,d1
addc +0,d1

@@ -94,12 +91,12 @@ do_csum_remainder:
cmp +16,d2
bcs do_csum_fewer_than_16
mov (a0+),d0
- add d0,d1
mov (a0+),e0
- addc e0,d1
mov (a0+),e1
- addc e1,d1
mov (a0+),e3
+ add d0,d1
+ addc e0,d1
+ addc e1,d1
addc e3,d1
addc +0,d1
add -16,d2
@@ -131,9 +128,9 @@ do_csum_fewer_than_4:
xor_cmp d0,d0,+2,d2
bcs do_csum_fewer_than_2
movhu (a0+),d0
-do_csum_fewer_than_2:
and +1,d2
beq do_csum_add_last_bit
+do_csum_fewer_than_2:
movbu (a0),d3
add d3,d0
do_csum_add_last_bit:
@@ -142,21 +139,19 @@ do_csum_add_last_bit:

do_csum_done:
# compress the checksum down to 16 bits
- mov +0xffff0000,d2
- and d1,d2
+ mov +0xffff0000,d0
+ and d1,d0
asl +16,d1
- add d2,d1,d0
+ add d1,d0
addc +0xffff,d0
lsr +16,d0

# flip the halves of the word result if the buffer was oddly aligned
- mov (12,sp),d1
- and +1,d1
+ and +1,a1
beq do_csum_not_oddly_aligned
swaph d0,d0 # exchange bits 15:8 with 7:0

do_csum_not_oddly_aligned:
ret [d2,d3],8

-do_csum_end:
- .size do_csum, do_csum_end-do_csum
+ .size do_csum, .-do_csum


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