On Fri, 29 Apr 2005 16:54:57 +0000 Calvin Spealman <[EMAIL PROTECTED]> wrote: | i dont understand whats going on here. I thought those flags enabled | the use of extended sets of the x86 instruction set, and amd64 chips | are in the x86 family, aren't they? and they support those | extensions, I'm sure, so what then do those flags do that the amd64 | can't make use of the flags?
Nooooo. See, there're two possibilities here. Possibility the first: the optimised code works on amd64. In this case, it's used on amd64 no matter what, since there aren't any amd64 chips that don't have the extra optimisations. So, no USE flag. Possibility the second. the optimised code is x86-specific and won't work on amd64. In this case, it's never used on amd64, and you don't want a USE flag to turn it on since it'll break. So, these USE flags aren't relevant. Unfortunately, amd64 wasn't around when they first came up, so we didn't give them a better name. Now, if at some point in the future, an amd64 chip comes along with some extra fancy optimisations (say sse4 or whatever), we'll have to have an sse4 USE flag added which *will* be enabled on amd64. I still think arch- prefixes to those flags is a good idea. -- Ciaran McCreesh : Gentoo Developer (Vim, Fluxbox, shell tools) Mail : ciaranm at gentoo.org Web : http://dev.gentoo.org/~ciaranm
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