On Wed, Aug 22, 2018 at 12:49:34PM -0400, Derrick Stolee wrote:
> > Yes, that was what I meant. We actually did switch to that hand-rolled
> > loop, but later we went back to memcmp in 0b006014c8 (hashcmp: use
> > memcmp instead of open-coded loop, 2017-08-09).
>
> Looking at that commit, I'm surprised the old logic was just a for
> loop, instead of a word-based approach, such as the following:
> [...]
> +struct object_id_20 {
> + uint64_t data0;
> + uint64_t data1;
> + uint32_t data2;
> +};
> +
> static inline int hashcmp(const unsigned char *sha1, const unsigned char
> *sha2)
> {
> - return memcmp(sha1, sha2, the_hash_algo->rawsz);
> + if (the_hash_algo->rawsz == 20) {
> + struct object_id_20 *obj1 = (struct object_id_20 *)sha1;
> + struct object_id_20 *obj2 = (struct object_id_20 *)sha2;
I wonder if you're potentially running afoul of alignment requirements
here.
-Peff
