Motorola DSP96002 User Manual page 677

add
jcc
inc
jmp
;
; *** Case: Addend 0 is Positive,
; Addend 1 is Negative ***
;
_neg2 bclr
sub
subc
jcc
bset
move
not
not
add
jcc
inc
_cclr3 move
move
;
; Check result equal zero (do not want to normalize)
;
_zchk move
and
tst
jne
tst
jne
move
;
; Check for Special Case (Round toward -infinity)
;
jclr
jset
bset
jmp
;
; Normalize for Opposite Sign Cases
;
_snrm jset
move
move
and
move
jclr
move
_st1 or
_st0 cmp
jle
dec
dec
lsl
B-158
d7,d1 ;
_zchk ;
d3 ;
_zchk ;
#31,d6.l ; set result as positive
d1,d0 ; subtract for case: a0+,a1-
d3,d2 ;
_cclr3 ; jump if result is positive
#31,d6.l ; set result as negative
#inum,d7.l ; get increment number
d0 ; get 2's comp of result
d2 ;
d7,d0 ;
_cclr3 ;
d2 ;
d0.l,d1.l ; get mantr.low and GRS bits
d2.l,d3.l ; get mantr.high
#smsk,d7.l ; get sticky mask
d7,d1 ; remove bits right of sticky
d3 ; check mantr.high = zero
_snrm ; normalize result
d1 ; check mantr.low = zero
_snrm ; normalize result
#0,d6.l ; set expr = zero
#22,sr,_rnd ; jump if round bit r1 = zero
#21,sr,_rnd ; jump if round bit r0 = one
#31,d6.l ; set result to negative zero
_rnd ; check rounding mode
#31,d3.l,_rnd ; jump if result normalized
#emsk,d7.l ; get exp mask
d6.l,d5.l ; get expr
d7,d5 ; delete tags
#eden,d4.l ; get denorm exponent
#8,d1.l,_st0 ; jump if sticky bit = 0
#onemsk,d7.l ; get one mask
d7,d1 ; set bits right of round bit
d4,d5 ; test expr = zero
_rnd
d6 ; decrement expr
d5 ; decrement expr copy
d1 ; shift mantr.l left
DSP96002 USER'S MANUAL
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; jump if denormalized number
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