On Tue, Mar 19, 2013 at 7:54 PM, Andrew Dalke <[email protected]> wrote: > Hi all, > > I have a Python extension which uses CPU-specific features, > if available. This is done through a run-time check. If the > hardware supports the POPCNT instruction then it selects one > implementation of my inner loop, if SSSE3 is available then > it selects another, otherwise it falls back to generic versions > of my performance critical kernel. (Some 95%+ of the time is > spent in this kernel.) > > Unfortunately, there's a failure mode I didn't expect. I > use -mssse3 and -O3 to compile all of the C code, even though > only one file needs that -mssse3 option. > > As a result, the other files are compiled with the expectation > that SSSE3 will exist. This causes a segfault for the line > > start_target_popcount = (int)(query_popcount * threshold); > > because the compiler used fisttpl, which is an SSSE-3 instruction. > After all, I told it to assume that ssse3 exists. > > The Debian packager for my package recently ran into this problem, > because the test machine has a gcc which understands -mssse3 but > the machine itself has an older CPU without those instructions. > > I'm trying to come up with a solution that can be automated for > the Debian distribution. I want a solution where the same binary > can work on older machines and on newer ones > > Ideally I would like to say that only one file is compiled > with the -mssse3 option. Since my selector code isn't part of this > file, SSSE-3 code will never be executed unless the CPU supports is. > > However, I can't figure out any way to tell distutils that > a set of compiler options are specific to a single file. > > Is that even possible?
One possible solution, albeit more complex code-wise than compiling that single file as a static lib, would be to subclass the compiler class you want to use and override its _compile() method, which is the one responsible for compiling a single file. You can then override the arguments in there. Look, for example, at distutils.unixcompiler.UnixCCompiler._compile. If you want to support different compiler implementations, you could even detect at runtime which compiler was selected with the --compiler option and subclass the appropriate implementation. Also getting distutils to accept a compiler subclass requires a little bit of hackery, but it's not undoable. If that optioni sounds viable to you I can delve into more details about how to actually do it, as I've had to do this sort of thing before myself. So yes, it can be done. Erik _______________________________________________ Distutils-SIG maillist - [email protected] http://mail.python.org/mailman/listinfo/distutils-sig
