Re: [PATCH] block-sha1: more good unaligned memory access candidates

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On Thu, 13 Aug 2009, Junio C Hamano wrote:

> Nicolas Pitre <nico@xxxxxxx> writes:
> 
> > As it is now, I was about to suggest:
> >
> > 	git mv block-sha1/sha1.[ch] .
> > 	rmdir block-sha1
> > 	rm -r mozilla-sha1
> > 	rm -r arm
> > 	rm -r ppc 
> >
> > and remove support for openssl's SHA1 usage, making this implementation 
> > unconditional.  After all it is faster, or so close to be faster than 
> > the alternatives, that we should probably cut on the extra dependency 
> > and simplify portability issues at the same time.
> 
> Wow.  Is it now faster than the arm/ and ppc/ hand-tweaked assembly?

It is indeed faster than the ARM assembly version by far, and faster 
than all the alternative implementations too, but with a 7x increase in 
compiled code size.  In the context of Git I think this is a good 
compromize.  Making the assembly version faster than the C version could 
be possible, but that would require quite some work and I don't expect 
the gain to be significant, certainly not worth the trouble.

Furthermore the C version can be used to generate ARM Thumb code while 
the asm version cannot without yet more work.


Nicolas
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