Subversion Repositories planix.SVN

#define BDNZ    BC      16,0,
#define BDNE    BC      0,2,

/*
 *      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
 *
 *              R3 == a (first arg passed in R3)
 *              R4 == alen
 *              R5 == b
 *              R6 == blen
 *              R7 == sum
 *              R8 == temporary
 *              R9 == temporary
 */
TEXT    mpvecadd(SB),$-4

        MOVW    alen+4(FP), R4
        MOVW    b+8(FP), R5
        MOVW    blen+12(FP), R6
        MOVW    sum+16(FP), R7
        SUB     R6, R4          /* calculate counter for second loop (alen > blen) */
        SUB     $4, R3          /* pre decrement for MOVWU's */
        SUB     $4, R5          /* pre decrement for MOVWU's */
        SUB     $4, R7          /* pre decrement for MOVWU's */
        MOVW    R0, XER         /* zero carry going in */

        /* if blen == 0, don't need to add it in */
        CMP     R0, R6
        BEQ     _add1

        /* sum[0:blen-1],carry = a[0:blen-1] + b[0:blen-1] */
        MOVW    R6, CTR
_addloop1:
        MOVWU   4(R3), R8
        MOVWU   4(R5), R9
        ADDE    R8, R9
        MOVWU   R9, 4(R7)
        BDNZ    _addloop1

_add1:
        /* if alen == blen, we're done */
        CMP     R0, R4
        BEQ     _addend

        /* sum[blen:alen-1],carry = a[blen:alen-1] + 0 + carry */
        MOVW    R4, CTR
_addloop2:
        MOVWU   4(R3), R8
        ADDE    R0, R8
        MOVWU   R8, 4(R7)
        BDNZ    _addloop2

        /* sum[alen] = carry */
_addend:
        ADDE    R0, R0, R8
        MOVW    R8, 4(R7)
        RETURN