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/*
* 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+4(FP),DX
MOVL blen+12(FP),CX
MOVL a+0(FP),SI
MOVL b+8(FP),BX
SUBL CX,DX
MOVL sum+16(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
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