On Wed, Apr 27, 2011 at 04:32:12PM -0700, Junio C Hamano wrote:
> > +static inline int is_null_sha1(const unsigned char *sha1)
> > {
> > - return memcmp(sha1, sha2, 20);
> > + const unsigned long long *sha1_64 = (void *)sha1;
> > + const unsigned int *sha1_32 = (void *)sha1;
>
> Can everybody do unaligned accesses just fine?
Misaligned accesses cause exceptions on some architectures which then
are fixed up in software making these accesses _very_ slow. You can
use __attribute__((packed)) to work around that but that will on the
affected architectures make gcc generate code pessimistically that is
slower than not using __attribute__((packed)) in case of proper
alignment. And __attribute__((packed)) only works with GCC.
Ralf
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