[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20150216151249.GX23507@brightrain.aerifal.cx>
Date: Mon, 16 Feb 2015 10:12:49 -0500
From: Rich Felker <dalias@...c.org>
To: Denys Vlasenko <vda.linux@...glemail.com>
Cc: musl <musl@...ts.openwall.com>
Subject: Re: [PATCH] x86_64/memset: use "small block" code for blocks
up to 30 bytes long
On Mon, Feb 16, 2015 at 11:09:25AM +0100, Denys Vlasenko wrote:
> On Sun, Feb 15, 2015 at 11:55 PM, Rich Felker <dalias@...c.org> wrote:
> >> "sub $8,%rcx" can be folded into lea.
> >
> > No, it can't, for the above reason.
>
> Why can't?
>
> lea -9(%rdx), %rcx
>
> will also underflow for %rdx == 0, just like "lea -1".
Then n==1..8 would also fall into the rep stosq path and either fail
horribly or need to use slow fixup code there.
Rich
Powered by blists - more mailing lists
Confused about mailing lists and their use?
Read about mailing lists on Wikipedia
and check out these
guidelines on proper formatting of your messages.
