I28F128_BLOCK_SIZE
if (memcmp(dst, src, I28F128_BLOCK_SIZE) == 0)
fence = p + (I28F128_BLOCK_SIZE >> 1);
while (len >= I28F128_BLOCK_SIZE) {
p += I28F128_BLOCK_SIZE >> 1;
q += I28F128_BLOCK_SIZE >> 1;
len -= I28F128_BLOCK_SIZE;
I28F128_BLOCK_SIZE);