Re: Bug#559516: FTBFS on various archs

[Jaromír Mikeš]

> Od: Free Ekanayaka <free at 64studio.com>

JM> These cflags improving performance on intel processors These are
JM> instructions sets like sse sse2 sse3 ... of intel i386 and x86-64
JM> processors
 
FE> Yes, that's correct.

JM> It looks like it should be ok allow these at least for amd64 and  IA-64
JM> arch.
JM> Not sure about i386, hurd-i386
 
JM> As regards performance benefits I can ask Fons (upstream).
 
FE> Sounds a good idea!
 
JM> How to allow these switches for specific architecture?
 
FE> You'll need to add some logic to debian/rules, checking the architecture
FE> the package is being built on and enabling the flags accordingly.

Hi Free,

I just got answer from Fons.
Copy/Paste
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JM> > I packaged zita-convolver 2.0.0 , but I got error report from user because
JM> these flags.

JM> > CPPFLAGS += -mmmx -msse -mfpmath=sse

JM> > Package is not build on some architectures.
JM> > I would like to use these optimization flags at least for amd64 and IA64.
JM> > I would like to know what is performance benefit from these flags?
JM> > Did you test it ever? Make it sense to save them for amd64 arch?

FA> I should have cleaned up these options, they are the results
FA> of lots of experiments. They had surprisingly little impact
FA> on performance. This could be different if the VECTORIZE
FA> option is enabled, but I would not recommend that ATM.

FA> For a source distribution I'd suggest:

FA> CPPFLAGS += -ffast-math -funroll-loops
FA> CPPFLAGS += -march=native

FA> And to compile a 'portable' binary:

FA> CPPFLAGS += -ffast-math -funroll-loops
FA> CPPFLAGS += -mtune=generic

FA> I can't comment on 64-bit machines - I don't have one !
FA> Anyway -march=native should do the right thing.
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I suggesting upload zita-convolver 2.0.0-2 (with Fons's suggestions) than I finish Jconvolver 0.8.4 and make some tests with these flags. In the case there will be some performance improvements we can release zita-convolver 2.0.0-3 than with cflags for sse instructions.

What you think? 
I already changed patch (and push commit) following Fons's instructions and made test build here.

regards

mira