# basic data representation is each bigit is a positive number
# less than 2^30, except for the leading bigit, which is in
# the range -2^30 < x < 2^30.
_adbig: .word 0x0fc0 #save registers 6-11
movl 4(ap),r1 #arg1 = addr of 1st bignum
movl 8(ap),r2 #arg2 = addr of 2nd bignum
movl $0xC0000000,r4 #r4 = clear constant.
movl sp,r10 #save start address of bignum on stack.
#note well that this is 4 above the actual
# first loop is to waltz through both bignums adding
# bigits, pushing them onto stack.
loop1: addl3 (r1),(r2),r0 #add bigits
bicl3 r4,r0,-(sp) #save sum, no overflow possible
extv $30,$2,r0,r5 #sign extend two high order bits
bleq out1 #negative indicates end of list.
movl 4(r2),r2 #get cdr of second bignum
bgtr loop1 #if neither list at end, do it again
# second loop propagates carries through higher order words.
# It assumes remaining list in r1.
loop2: addl3 (r1),r5,r0 #add bigits and carry
bicl3 r4,r0,-(sp) #save sum, no overflow possible
extv $30,$2,r0,r5 #sign extend two high order bits
out2: bgtr loop2 #negative indicates end of list.
# suppress unnecessary leading zeroes and -1's
iexport:movl sp,r11 #more set up for output routine
Bexport:tstl (r11) #look at leading bigit
bgtr copyit #if positive, can allocate storage etc.
blss negchk #if neg, still a chance we can get by
cmpl r11,r10 #check to see that
bgeq copyit #we don't pop everything off of stack
mcoml (r11),r3 #r3 is junk register
bneq copyit #short test for -1
tstl 4(r11) #examine next bigit
beql copyit #if zero must must leave as is.
cmpl r11,r10 #check to see that
bgeq copyit #we don't pop everything off of stack
bisl2 r4,(r11) #set high order two bits
brb negchk #try to supress more leading -1's
# The following code is an error exit from the first loop
# and is out of place to avoid a jump around a jump.
out1: movl 4(r2),r1 #get next addr of list to continue.
brb out2 #if second list simult. exhausted, do
# loop3 is a faster version of loop2 when carries are no
loop3a: pushl (r1) #get datum
loop3: movl 4(r1),r1 #get cdr
bgtr loop3a #if not at end get next cell
# create linked list representation of bignum
copyit: subl3 r11,r10,r2 #see if we can get away with allocating an int
bneq on1 #test for having popped everything
subl3 $4,r10,r11 #if so, fix up pointer to bottom
brb intout #and allocate int.
on1: cmpl r2,$4 #if = 4, then can do
calls $0,_newsdot #get new cell for new bignum
backfr: movl r0,(r6)+ #push address of cell on
#arg stack to save from garbage collection.
#There is guaranteed to be slop for a least one
movl r0,r8 #r8 = result of adbig
loop4: movl -(r10),(r0) #save bigit
movl r0,r9 #r9 = old cell, to link
cmpl r10,r11 #have we copy'ed all the bigits?
calls $0,_newsdot #get new cell for new bignum
movl r0,4(r9) #link new cell to old
clrl 4(r9) #indicate end of list with 0
movl -(r6),r0 #give resultant address.
# bignum multiplication routine
_mulbig:.word 0x0fc0 #save regs 6-11
movl 4(ap),r1 #get address of first bignum
movl sp,r11 #save top of 1st bignum
mloop1: pushl (r1) #get bigit
bgtr mloop1 #repeat if not done
movl sp,r10 #save bottom of 1st bignum, top of 2nd bignum
movl 8(ap),r1 #get address of 2nd bignum
mloop2: pushl (r1) #get bigit
bgtr mloop2 #repeat if not done
movl sp,r9 #save bottom of 2nd bignum
subl3 r9,r11,r6 #r6 contains sum of lengths of bignums
movl sp,r8 #save bottom of product bignum
m1: movc5 $0,(r8),$0,r6,(r8)#zap out stack space
movl r9,r7 #r7 = &w[j +n] (+4 for a.d.) through calculation
subl3 $4,r10,r4 #r4 = &v[j]
m3: movl r7,r5 #r7 = &w[j+n]
subl3 $4,r11,r3 #r3 = &u[i]
m4: addl2 -(r5),r2 #add w[i + j] to carry (no ofl poss)
emul (r3),(r4),r2,r0 #r0 = u[i] * v[j] + sext(carry)
extzv $0,$30,r0,(r5) #get new bigit
extv $30,$32,r0,r2 #get new carry
m5: acbl r10,$-4,r3,m4 #r3 =- 4; if(r3 >= r10) goto m4; r10 = &[u1];
movl r2,-(r5) #save w[j] = carry
m6: subl2 $4,r7 #add just &w[j+n] (+4 for autodec)
acbl r9,$-4,r4,m3 #r4 =- 4; if(r4>=r9) goto m5; r9 = &v[1]
movl r9,r10 #set up for output routine
movl $0xC0000000,r4 #r4 = clear constant.
movq 20(fp),r6 #restor _np and _lbot !
projects / unix-history / blob