Re: [PATCH v2] target/ppc: add vmsumudm vmsumcud instructions

[Richard Henderson]

On 6/18/20 10:10 PM, Lijun Pan wrote:
>> Unfortunately, I can't find the v3.1 spec online yet, so I can't look at this
>> myself.  What is the instruction supposed to produce?
> 
> https://ibm.ent.box.com/s/hhjfw0x0lrbtyzmiaffnbxh2fuo0fog0

Thank you.  So it really is the sum of an input and two separate 64x64->128 bit
multiplies.

I suggest

void helper_vmsumudm(CPUPPCState *env, ppc_avr_t *r,
                     ppc_avr_t *a, ppc_avr_t *b, ppc_avr_t *c)
{
    Int128 sum;
    uint64_t lo, hi;

    sum = int128_make128(c->VsrD(1), c->VsrD(0));

    mulu64(&lo, &hi, a->VsrD(0), b->VsrD(0));
    sum = int128_add(sum, int128_make128(lo, hi));

    mulu64(&lo, &hi, a->VsrD(1), b->VsrD(1));
    sum = int128_add(sum, int128_make128(lo, hi));

    r->VsrD(0) = int128_gethi(sum);
    r->VsrD(1) = int128_getlo(sum);
}

void helper_vmsumcud(CPUPPCState *env, ppc_avr_t *r,
                     ppc_avr_t *a, ppc_avr_t *b, ppc_avr_t *c)
{
    Int128 sum;
    uint64_t p1lo, p1hi, p2lo, p2hi;

    mulu64(&p1lo, &p1hi, a->VsrD(0), b->VsrD(0));
    mulu64(&p2lo, &p2hi, a->VsrD(1), b->VsrD(1));

    /* Sum lowest 64-bit elements.  */
    sum = int128_make128(c->VsrD(1), 0);
    sum = int128_add(sum, int128_make128(p1lo, 0));
    sum = int128_add(sum, int128_make128(p2lo, 0));

    /*
     * Discard low 64-bits, leaving the carry into bit 64.
     * Then sum the higher 64-bit elements.
     */
    sum = int128_rshift(sum, 64);
    sum = int128_add(sum, int128_make128(c->VsrD(0), 0));
    sum = int128_add(sum, int128_make128(p1hi, 0));
    sum = int128_add(sum, int128_make128(p2hi, 0));

    /* The result is only the carry into bits 64 & 65. */
    r->VsrD(1) = int128_gethi(sum);
    r->VsrD(0) = 0;
}


r~