[Fedora-packaging] Re: sse3 optimized and unoptimized library
Hello, Matt.
On Tuesday, 19 July 2016 at 00:06, Matthew Chan wrote:
I'm currently packaging a libraries that are nearly identical,
except one
version is sse3 optimized, and the other is not. (license also changes to
GPL from BSD). The performance difference is significant.
What is the correct way to handle this? They both provide the same libraries
and headers. Should I use an ExclusiveArch: x86_64 on the sse3 version, and
an ExcludeArch: x86_64 on the unoptimized version? Or perhaps even use a
conflicts? (Assuming there are x86_64 processors that don't support SSE3?
SSE3 seems to have been introduced with Pentium 4 Prescott)
In theory, the code shipped in Fedora should work on any i686-class CPU
for x86 32bit builds and any x86_64 CPU. So if you want to enable any
kind of SIMD unconditionally, you can only rely on SSE2 presence in
x86_64 ABI. Anything else should be detected and used at runtime only.
Having said that, it's unlikely that someone is using your particular
package on such old hardware. What package are you talking about,
specifically?
There was a similar question in the devel list a couple of months back,
but with no replies:
https://lists.fedoraproject.org/archives/list/devel@lists.fedoraproject.o...
Regards,
Dominik
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