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Date: Tue, 10 Feb 2015 15:50:47 -0500
From: Rich Felker <>
Subject: Re: [PATCH 1/2] x86_64/memset: simple optimizations

On Tue, Feb 10, 2015 at 06:30:56PM +0100, Denys Vlasenko wrote:
> "and $0xff,%esi" is a six-byte insn (81 e6 ff 00 00 00), can use
> 4-byte "movzbl %sil,%esi" (40 0f b6 f6) instead.
> [...]

Do you want to go ahead with these patches as-is, or consider some of
the other ideas we discussed off-list like avoiding the 64-bit imul
entirely in the small-n case? If you think that's easy as another
incremental change I'll go ahead with these, but if it's basically
going to be backing out these first changes and replacing them with
something different, I'm not sure if it makes sense to commit one then
the other.


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