Subversion Repositories planix.SVN

/*
 *      mpvecdigmuladd(mpdigit *b, int n, mpdigit m, mpdigit *p)
 *
 *      p += b*m
 *
 *      each step looks like:
 *              hi,lo = m*b[i]
 *              lo += oldhi + carry
 *              hi += carry
 *              p[i] += lo
 *              oldhi = hi
 *
 *      the registers are:
 *              b = R1
 *              n = R4
 *              m = R5
 *              p = R6
 *              i = R7
 *              hi = R8         - constrained by hardware
 *              lo = R9         - constrained by hardware
 *              oldhi = R10
 *              tmp = R11
 *              
 */
TEXT    mpvecdigmuladd(SB),$0

        MOVW    n+4(FP),R4
        MOVW    m+8(FP),R5
        MOVW    p+12(FP),R6


        MOVW    R0, R10         /* oldhi = 0 */
        BEQ     R6, _muladd1
_muladdloop:
        MOVW    0(R1), R9       /* lo = b[i] */
        ADDU    $4, R1
        MOVW    0(R6), R11      /* tmp = p[i] */
        MULU    R9, R5
        MOVW    HI, R8          /* hi = (b[i] * m)>>32 */
        MOVW    LO, R9          /* lo = b[i] * m */
        ADDU    R10, R9         /* lo += oldhi */
        SGTU    R10, R9, R2
        ADDU    R2, R8          /* hi += carry */
        ADDU    R9, R11         /* tmp += lo */
        SGTU    R9, R11, R2
        ADDU    R2, R8          /* hi += carry */
        MOVW    R11, 0(R6)      /* p[i] = tmp */
        ADDU    $4, R6
        MOVW    R8, R10         /* oldhi = hi */
        SUBU    $1, R4
        BNE     R4, _muladdloop

_muladd1:
        MOVW    0(R6), R11      /* tmp = p[i] */
        ADDU    R10, R11        /* tmp += oldhi */
        MOVW    R11, 0(R6)      /* p[i] = tmp */

        RET