Commit 5f2a80ad authored by Richard Henderson's avatar Richard Henderson
Browse files

target-alpha: Rewrite helper_cmpbge using bit tests 



Not quite as good as using a proper host vector compare,
but certainly better than a loop.

Signed-off-by: default avatarRichard Henderson <rth@twiddle.net>
parent 074a9925

target-alpha/int_helper.c

+26 −13
Original line number Diff line number Diff line
@@ -58,20 +58,33 @@ uint64_t helper_zap(uint64_t val, uint64_t mask) 
    return helper_zapnot(val, ~mask);

}



uint64_t helper_cmpbge(uint64_t op1, uint64_t op2)

uint64_t helper_cmpbge(uint64_t a, uint64_t b)

{

    uint8_t opa, opb, res;

    int i;



    res = 0;

    for (i = 0; i < 8; i++) {

        opa = op1 >> (i * 8);

        opb = op2 >> (i * 8);

        if (opa >= opb) {

            res |= 1 << i;

        }

    }

    return res;

    uint64_t mask = 0x00ff00ff00ff00ffULL;

    uint64_t test = 0x0100010001000100ULL;

    uint64_t al, ah, bl, bh, cl, ch;



    /* Separate the bytes to avoid false positives.  */

    al = a & mask;

    bl = b & mask;

    ah = (a >> 8) & mask;

    bh = (b >> 8) & mask;



    /* "Compare".  If a byte in B is greater than a byte in A,

       it will clear the test bit.  */

    cl = ((al | test) - bl) & test;

    ch = ((ah | test) - bh) & test;



    /* Fold all of the test bits into a contiguous set.  */

    /* ch=.......a...............c...............e...............g........ */

    /* cl=.......b...............d...............f...............h........ */

    cl += ch << 1;

    /* cl=......ab..............cd..............ef..............gh........ */

    cl |= cl << 14;

    /* cl=......abcd............cdef............efgh............gh........ */

    cl |= cl << 28;

    /* cl=......abcdefgh........cdefgh..........efgh............gh........ */

    return cl >> 50;

}



uint64_t helper_minub8(uint64_t op1, uint64_t op2)