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Re: How to handle "-march=native"?
On Sun, Dec 29, 2013 at 09:02:06PM +0900, Takahiro Kambe wrote:
> In message <rmippoj4onw.fsf%fnord.ir.bbn.com@localhost>
> on 2013年12月26日 10:28:35 -0500,
> Greg Troxel <gdt%ir.bbn.com@localhost> wrote:
> >> # GCC 4.3+ can also produce faster executables when its used.
> >
> > Sure, but then they aren't portable.
> Yes.
>
> > It seems there are multiple things going on:
> >
> > 1) there may be some bugs about cpu detection, particulaly in various
> > vm environments, or about the mapping of flags to instructions.
> It might be temporary problem since vcvtsi2sdq instruction works after
> reboot OS X (and suspend/resume guest OS, NetBSD 6.1_STABLE).
Hmmm... I can't actually find the vcvtsi2sdq instruction in the
x86 instruction set listing I have (which contains AVX, but not AVX2).
It might be that suspend/resume isn't correctly setting the registers
that disable AVX!
In particular any that use the 256bit ymm registers cannot be used in netbsd.
And I can't remember whether there is a separate enable/disable bit.
David
--
David Laight: david%l8s.co.uk@localhost
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