It's an equivalent expression, but the '+' gives us some freedom in
instruction selection (for example, we can use 'lea' rather than 'add'),
and associates with the other additions around it to give some minor
scheduling freedom.
Suggested-by: linux@horizon.com
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Avoid repeating the shared parts of the different rounds by adding a
macro layer or two. It was already more cpp than C.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
The mozilla-SHA1 code did this 80-word array for the 80 iterations. But
the SHA1 state is really just 512 bits, and you can actually keep it in
a kind of "circular queue" of just 16 words instead.
This requires us to do the xor updates as we go along (rather than as a
pre-phase), but that's really what we want to do anyway.
This gets me really close to the OpenSSL performance on my Nehalem.
Look ma, all C code (ok, there's the rol/ror hack, but that one doesn't
strictly even matter on my Nehalem, it's just a local optimization).
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
This helps a teeny bit. But what I -really- want to do is to avoid the
whole 80-array loop, and do the xor updates as I go along..
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Bert Wesarg noticed non-x86 version of SHA_ROT() had a typo.
Also spell in-line assembly as __asm__(), otherwise I seem to get
error: implicit declaration of function 'asm' from my compiler.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Use the one with the smaller constant. It _can_ generate slightly
smaller code (a constant of 1 is special), but perhaps more importantly
it's possibly faster on any uarch that does a rotate with a loop.
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Undo the change I picked up from the mailing list discussion suggested
by Nico, not because it is wrong, but it will be done at the end of the
follow-up series.
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Based on the mozilla SHA1 routine, but doing the input data accesses a
word at a time and with 'htonl()' instead of loading bytes and shifting.
It requires an architecture that is ok with unaligned 32-bit loads and a
fast htonl().
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
