Am 17.08.2012 19:57, schrieb Jorge Almeida: > On Fri, Aug 17, 2012 at 2:53 PM, Florian Philipp <li...@binarywings.net> > wrote: >> Am 17.08.2012 10:58, schrieb Jorge Almeida: >>> >>> 1) Is this strategy right? If so, any other flags to add? (or any >>> flags to remove from the list?) >>> >>> 2) The --param flags are the ones of the computer that will do the >>> compiling. I'm guessing the produced binaries are compatible with cpu >>> with different --param flags. Is this right? >>> >>> TIA >>> >>> Jorge Almeida >>> >> >> 1) Yes. But as you can see, -march=prescott is basically a subset of >> atom. In fact, before there was a -march=atom option, prescott was the >> best flag for atoms. I think you can avoid some hassle by simply >> enabling "-march=prescott --param l1-cache-line-size=64 --param >> l2-cache-size=512". >> >> 2) Yes, the param flags do not affect compatibility. Using the lower >> value will probably be better but this is just an educated guess. >> > > What about: > > CFLAGS="-O2 -pipe -fomit-frame-pointer -march=prescott -mtune=atom --param > l1-cache-size=16 --param l1-cache-line-size=64 --param l2-cache-size=1024" > > If prescott were exactly a subset of atom, this would yield the best of both > worlds. Can it still be safe? > > I read in http://forums.gentoo.org/viewtopic-t-895104.html : > atom > Intel Atom CPU with 64-bit extensions, MMX, SSE, SSE2, SSE3 and SSSE3 > instruction set support. > > Does this mean that these flags are pulled by -mtune=atom, or do we need to > ask for them explicitly? The WiKi shows how to find which flags are pulled by > -march=native, but not the other cases. > > Thanks > > Jorge Almeida >
Oh, sorry, I didn't think of the second generation atoms. I guess your newer atom is a bit more different from prescott than the one I talked about. Anyway, using -march=prescott is still viable. It just means you lose a bit more in terms of usable SSE extensions on your atom. Your CFLAGS look good to me. They won't pull in anything that your prescott cannot handle. Regards, Florian Philipp
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