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
