Date: Mon, 16 Feb 2015 11:09:25 +0100 From: Denys Vlasenko <vda.linux@...glemail.com> To: Rich Felker <dalias@...c.org> Cc: musl <musl@...ts.openwall.com> Subject: Re: [PATCH] x86_64/memset: use "small block" code for blocks up to 30 bytes long 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".
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