Re: [PATCH] block-sha1: remove use of assembly

[Taylor Blau <me@ttaylorr.com>]

On Mon, Mar 07, 2022 at 11:25:52PM +0000, brian m. carlson wrote:
> In the block SHA-1 code, we have special assembly code for i386 and
> amd64 to perform rotations with assembly.  This is supposed to help pick
> the correct rotation operation depending on which rotation is smaller,
> which can help some systems perform slightly better, since any circular
> rotation can be specified as either a rotate left or a rotate right.
> However, this isn't needed, so we should remove it.

At -O1 or higher (at least on GCC) this optimization is indeed
performed. Here's a Godbolt example that shows this:

    https://godbolt.org/z/9zMP93hr1

so I agree that this code isn't helping us at all. And in the
meantime...

> The downside of using this code, however, is that it uses a GCC
> extension, which makes the compiler complain when using -pedantic unless
> it's prefixed with __extension__.  We could fix that, but since it's
> not needed, let's just remove it.  We haven't noticed this because
> almost everyone uses the SHA1DC code instead, but it still shows up for
> some people.

...it makes it impossible to compile git if you have
`BLK_SHA1=YesPlease` and `DEVELOPER=1` in your environment. So I am
happy to see this go.

On another note: missing Signed-off-by?

Thanks,
Taylor