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Re: Smoking gun: NetBSD 6.0.1 userland instability



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Hello,

On Mar 7, 2013, at 11:28 AM, David Riley wrote:

On Mar 7, 2013, at 11:25 AM, Donald Lee wrote:

In the old days, I would just use "-g", and presume that the optimization
was disabled, but modern compilers don't do that any more.  They
reportedly try to optimize more often, even when not necessarily
desired.

The only thing -g should do is enable debugging symbols; it doesn't
generally have an effect on optimization.  Perhaps you mean -O0?
I believe there's also a -mno-altivec switch, but I think that
might only disable use of AltiVec intrinsics (i.e. I have no idea
if it affects automatic vectorization).

Not quite. If you build for an altivec-capable CPU ( -mcpu=74xx or something ) gcc will output altivec instructions for things like inlined memcpy(). -mno-altivec prevents that.

have fun
Michael

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