ref: ee695eff4329234e20abb68ff3100d3b15929418
dir: /libmp/Plan9-amd64/mpvecadd.s/
/* * mpvecadd(mpdigit *a, int alen, mpdigit *b, int blen, mpdigit *sum) * * sum[0:alen] = a[0:alen-1] + b[0:blen-1] * * prereq: alen >= blen, sum has room for alen+1 digits */ TEXT mpvecadd(SB),$0 MOVL alen+8(FP),DX MOVL blen+24(FP),CX /* MOVL a+0(FP),SI */ MOVQ RARG, SI MOVQ b+16(FP),BX SUBL CX,DX MOVQ sum+32(FP),DI XORL BP,BP /* this also sets carry to 0 */ /* skip addition if b is zero */ TESTL CX,CX JZ _add1 /* sum[0:blen-1],carry = a[0:blen-1] + b[0:blen-1] */ _addloop1: MOVL (SI)(BP*4), AX ADCL (BX)(BP*4), AX MOVL AX,(DI)(BP*4) INCL BP LOOP _addloop1 _add1: /* jump if alen > blen */ INCL DX MOVL DX,CX LOOP _addloop2 /* sum[alen] = carry */ _addend: JC _addcarry MOVL $0,(DI)(BP*4) RET _addcarry: MOVL $1,(DI)(BP*4) RET /* sum[blen:alen-1],carry = a[blen:alen-1] + 0 */ _addloop2: MOVL (SI)(BP*4),AX ADCL $0,AX MOVL AX,(DI)(BP*4) INCL BP LOOP _addloop2 JMP _addend