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From: | Sunil Amitkumar Janki |
Subject: | Re: [Qemu-devel] 0.9.0 and svn don't build with -march=pentium2 etc.; was: Latest SVN fails to build on Fedora Core 6 (same with 0.9.0) |
Date: | Fri, 23 Mar 2007 11:21:46 +0100 |
User-agent: | Thunderbird 1.5.0.10 (X11/20070221) |
Thomas Orgis wrote:
Am Thu, 22 Mar 2007 21:13:00 +0100schrieb Sunil Amitkumar Janki <address@hidden>:I have seen this error as well when building with i686/pentium3/athlon optimisations. As I am doing a course on x86 assembly programming at the moment I can tell you that it suffers from register starvation and the message tells you that there aren't enough registers left.Yeah, that's the message... what I wonder is this is to be expected. Does SSE steal or add registers? -march=pentium-mmx -m3dnow seems to work, though. Is it just a coincidence that gcc optimizattion uses some registers with high march (and SSE) that it didn't use with lower march? I'm wondering if it's the code that is just lucky to compile with some march settings and not so lucky with others or if it's a gcc bug or whatever... Thomas. _______________________________________________ Qemu-devel mailing list address@hidden http://lists.nongnu.org/mailman/listinfo/qemu-devel
The reason I build it with "-march=i486" is because Pentium optimisationsare really only meant for real Intel Pentium (MMX) and not for AMD K6 (I/II/II).
You would probably be better off using "-march=k6-* -m3dnow -mmx" for an Athlon. I have seen my Athlon slowing to a grind with a Pentium kernel instead of an i486 or Athlon kernel. I do not understand enough of QEMU yet, but I have checked out CVS and am reading through its source. When I understand more I hope we can fix this long-standing annoyance. Do you have a 64-bit X86 processor running 64-bit software? It doesn't seem to suffer from this same problem. I am testing on an AMD Athlon 64 X2 (AM2) now and QEMU works with "-march=opteron" and of course KVM. Sunil.
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