On Wednesday 20 July 2005 12:25, Ivan Yosifov wrote: > > > > Also, I believe that the -march=pentium4 option /was/ actually used up > > > > until kernel 2.6.10 where it was dropped because of a risk that some > > > > versions of gcc would cause the kernel to use SSE registers for data > > > > movement (which is a no-no). > > > > > > > > > > You seem right. I fetched a 2.6.9 tarball and it is really built with > > > -march=pentium4. Do you know which are versions of gcc in question ? > > > > > > > No, I'm afraid not. I only know that the advice came from Richard > > Henderson who (I think) is one of the core glibc hackers. You can see > > the point at which it was introduced by Linus in the ChangeLog (2nd > > message from last): > > > > http://www.kernel.org/pub/linux/kernel/v2.6/ChangeLog-2.6.10 > > Seems to be this one: > > <[EMAIL PROTECTED]> > Don't use "-march=pentium3" for gcc tuning. > > rth tells me that some versions of gcc may end up using the > SSE registers for data movement when you do that. > > Use "-march=i686 -mtune=xxxx" instead. > > (We do the same thing for march=pentium2/4 too, just for > consistency). > > > The way it is worded it seems that it is a problem with *some* versions > of gcc only on p3, not p4.
Why do you care? I bet that differences between i686 code and pentium4 code are well below noise level. -- vda - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
