1# urem.s 5.1 82/07/15 2# 3# urem - unsigned remainder for vax-11 4# 5# arguments: dividend, divisor 6# result: remainder 7# uses r0-r2 8# 9# if 1 < divisor <= 2147483647, zero-extend the dividend 10# to 64 bits and let ediv do the work. If the divisor is 1, 11# ediv will overflow if bit 31 of the dividend is on, so 12# just return 0. If the divisor is 0, do the ediv also, 13# so it will generate the proper exception. All other values 14# of the divisor have bit 31 on: in this case the remainder 15# must be the dividend if divisor > dividend, and the dividend 16# minus the divisor otherwise. The comparison must be unsigned. 17# 18 .text 19 .align 1 20 .globl urem 21urem: .word 0x0000 22 movl 4(ap),r0 # Dividend 23 movl 8(ap),r2 # Divisor 24 jeql div # If divisor=0, force exception 25 cmpl r2,$1 # If divisor <= 1 (signed), 26 jleq nodiv # no division is necessary 27div: clrl r1 # Zero-extend the dividend 28 ediv r2,r0,r2,r0 # Divide. q->r2 (discarded), r->r0 29 ret 30nodiv: jneq nzero # If divisor=1, return 0 31 clrl r0 # (because doing the divide will overflow 32 ret # if the dividend has its high bit on) 33nzero: cmpl r0,r2 # If dividend < divisor (unsigned) 34 jlssu retn # remainder is dividend 35 subl2 r2,r0 # else remainder is dividend - divisor 36retn: ret 37 38 39