Subversion Repositories planix.SVN

        TEXT    memcmp(SB), $0
MOVW R1, 0(FP)

/*
 * performance:
 *      alligned about 1.0us/call and 17.4mb/sec
 *      unalligned is about 3.1mb/sec
 */

        MOVW    n+8(FP), R3             /* R3 is count */
        MOVW    s1+0(FP), R4            /* R4 is pointer1 */
        MOVW    s2+4(FP), R5            /* R5 is pointer2 */
        ADDU    R3,R4, R6               /* R6 is end pointer1 */

/*
 * if not at least 4 chars,
 * dont even mess around.
 * 3 chars to guarantee any
 * rounding up to a word
 * boundary and 4 characters
 * to get at least maybe one
 * full word cmp.
 */
        SGT     $4,R3, R1
        BNE     R1, out

/*
 * test if both pointers
 * are similarly word alligned
 */
        XOR     R4,R5, R1
        AND     $3, R1
        BNE     R1, out

/*
 * byte at a time to word allign
 */
l1:
        AND     $3,R4, R1
        BEQ     R1, l2
        MOVBU   0(R4), R8
        MOVBU   0(R5), R9
        ADDU    $1, R4
        BNE     R8,R9, ne
        ADDU    $1, R5
        JMP     l1

/*
 * turn R3 into end pointer1-15
 * cmp 16 at a time while theres room
 */
l2:
        ADDU    $-15,R6, R3
l3:
        SGTU    R3,R4, R1
        BEQ     R1, l4
        MOVW    0(R4), R8
        MOVW    0(R5), R9
        MOVW    4(R4), R10
        BNE     R8,R9, ne
        MOVW    4(R5), R11
        MOVW    8(R4), R8
        BNE     R10,R11, ne1
        MOVW    8(R5), R9
        MOVW    12(R4), R10
        BNE     R8,R9, ne
        MOVW    12(R5), R11
        ADDU    $16, R4
        BNE     R10,R11, ne1
        BNE     R8,R9, ne
        ADDU    $16, R5
        JMP     l3

/*
 * turn R3 into end pointer1-3
 * cmp 4 at a time while theres room
 */
l4:
        ADDU    $-3,R6, R3
l5:
        SGTU    R3,R4, R1
        BEQ     R1, out
        MOVW    0(R4), R8
        MOVW    0(R5), R9
        ADDU    $4, R4
        BNE     R8,R9, ne       /* only works because big endian */
        ADDU    $4, R5
        JMP     l5

/*
 * last loop, cmp byte at a time
 */
out:
        SGTU    R6,R4, R1
        BEQ     R1, ret
        MOVBU   0(R4), R8
        MOVBU   0(R5), R9
        ADDU    $1, R4
        BNE     R8,R9, ne
        ADDU    $1, R5
        JMP     out

ne1:
        SGTU    R10,R11, R1
        BNE     R1, ret
        MOVW    $-1,R1
        RET
ne:
        SGTU    R8,R9, R1
        BNE     R1, ret
        MOVW    $-1,R1
ret:
        RET
        END