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FishMarket 1.0
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disk_362
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memroutines
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memcmp.asm
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Assembly Source File
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1992-05-06
|
2KB
|
100 lines
;--------------------------------------------------------------------
; memcmp() -- a faster version
;--------------------------------------------------------------------
; x = memcmp( s1,s2,count)
; This routine compares the data pointed to by "s1" and "s2" for "count"
; bytes, and returns 0 if they are identical, a negative number if s1 < s2,
; or a positive number if s1 > s2.
; Robert Broughton
; 328-1027 Davie St.
; Vancouver, BC V6E 4L2
; Canada
; USENet: a1040@mindlink.UUCP
MANX SET 1
IFND MANX
IDNT _memcmp
CSECT _memcmp
ENDC
XDEF _memcmp
_memcmp:
link a5,#.127
move.l 12(a5),a1 ;* s2
move.l 8(a5),a0 ;* s1
move.l 16(a5),d0 ;* count
cmp.l #7,d0
ble finish ;* too small, don't bother with optimization
move.l a0,d1
btst #0,d1 ;* even or odd
beq ineven ;* it's even already
subq.l #1,d0
move.b (a0)+,d1
cmp.b (a1)+,d1 ;* now it's even
bne lowout
ineven:
move.l a1,d1
btst #0,d1 ;* how about output
beq outeven
outodd:
; unfortunately, the output address is not word-aligned, so we will
; load a long word from s1 into d1, load four bytes from s2 into d2,
; and compare the two registers
cmp.l #3,d0
ble finish
move.l (a0)+,d1
move.b (a1)+,d2
ext.w d2
swap d2
move.w (a1)+,d2
lsl.l #8,d2
move.b (a1)+,d2
subq.l #4,d0
cmp.l d1,d2
beq outodd
sub.l d2,d1
move.l d1,d0
bra really
outeven:
; ideal situation; we can load and compare longwords
cmp.l #3,d0
ble finish
subq.l #4,d0
cmp.l (a0)+,(a1)+
beq outeven
move.l -(a0),d0
sub.l -(a1),d0
bra really
finish:
cmp.b #0,d0
ble really
subq.l #1,d0
finishloop:
move.b (a0)+,d1
cmp.b (a1)+,d1
dbne d0,finishloop
bra lowout
really:
unlk a5
rts
lowout:
sub.b -(a1),d1
ext.w d1
ext.l d1
move.l d1,d0
bra really
.127 equ 0