# urem.s 5.1 82/07/15 # # urem - unsigned remainder for vax-11 # # arguments: dividend, divisor # result: remainder # uses r0-r2 # # if 1 < divisor <= 2147483647, zero-extend the dividend # to 64 bits and let ediv do the work. If the divisor is 1, # ediv will overflow if bit 31 of the dividend is on, so # just return 0. If the divisor is 0, do the ediv also, # so it will generate the proper exception. All other values # of the divisor have bit 31 on: in this case the remainder # must be the dividend if divisor > dividend, and the dividend # minus the divisor otherwise. The comparison must be unsigned. # .text .align 1 .globl urem urem: .word 0x0000 movl 4(ap),r0 # Dividend movl 8(ap),r2 # Divisor jeql div # If divisor=0, force exception cmpl r2,$1 # If divisor <= 1 (signed), jleq nodiv # no division is necessary div: clrl r1 # Zero-extend the dividend ediv r2,r0,r2,r0 # Divide. q->r2 (discarded), r->r0 ret nodiv: jneq nzero # If divisor=1, return 0 clrl r0 # (because doing the divide will overflow ret # if the dividend has its high bit on) nzero: cmpl r0,r2 # If dividend < divisor (unsigned) jlssu retn # remainder is dividend subl2 r2,r0 # else remainder is dividend - divisor retn: ret