-.end
-
- .title vax_bn_div64 division 64/32=>32
-;
-; r.l. 16-jan-1998
-;
-; unsigned int bn_div64(unsigned long h, unsigned long l, unsigned long d)
-; return <h,l>/d;
-;
-
- .psect code,nowrt
-
-h=4 ;(AP) by value (input)
-l=8 ;(AP) by value (input)
-d=12 ;(AP) by value (input)
-
-.entry bn_div64,^m<r2,r3,r4,r5,r6,r7,r8,r9>
-
- movl l(ap),r2 ; l
- movl h(ap),r3 ; h
- movl d(ap),r4 ; d
- clrl r5 ; q
- clrl r6 ; r
-
- ; Treat "negative" specially
- tstl r3
- blss 30$
-
- tstl r4
- beql 90$
-
- ediv r4,r2,r5,r6
- bvs 666$
-
- movl r5,r0
- ret
-
-30$:
- ; The theory here is to do some harmless shifting and a little
- ; bit of rounding (brackets are to designate when decimals are
- ; cut off):
- ;
- ; result = 2 * [ ([<h,0>/2] + [d/2]) / d ] + [ l / d ]
-
- movl #0,r7
- movl r3,r8 ; copy h
- ashq #-1,r7,r7 ; [<h,0>/2] => <r8,r7>
- bicl2 #^X80000000,r8 ; Remove "sign"
-
- movl r4,r9 ; copy d
- ashl #-1,r9,r9 ; [d/2] => r9
- bicl2 #^X80000000,r9 ; Remove "sign"
-
- addl2 r9,r7
- adwc #0,r8 ; [<h,0>/2] + [d/2] => <r8,r7>
-
- ediv r4,r7,r5,r6 ; [ ([<h,0>/2] + [d/2]) / d ] => <r5,r6>
- bvs 666$
-
- movl #0,r6
- ashq #1,r5,r5 ; 2 * [ ([<h,0>/2] + [d/2]) / d ] => r5
-
- movl #0,r3
- ediv r4,r2,r8,r9 ; [ l / d ] => <r8,r9>
-
- addl2 r8,r5 ;
- bcs 666$
-
- movl r5,r0
- ret
-
-90$:
- movl #-1,r0
- ret
-
-666$:
-
-