[LLVMdev] Using thin archives when building llvm (original) (raw)

Rafael Espíndola rafael.espindola at gmail.com
Fri Jul 17 10:11:48 PDT 2015

FWIW, i’d more than welcome a patch to get this in to cmake.

Chris added a flag (LLVMOPTIMIZEDTBLGEN) to build an optimized tblgen and use that in the regular build. I’d be happy to see a similar flag used to have that step build an llvm-ar used by the rest of compilation to use thin archives. At least until we start shipping this. I’m happy to propose a patch or help test one if you have one in future.

I normally locally install a recent trunk, so for me CMAKE_CXX_CREATE_STATIC_LIBRARY does the job. Given that, I am probably not the best one to write patch for building llvm-ar and then use it.

Also, llvm-ar depends on target (to parse inline asm), so quite a few .a files will still be built with the old ar.

I think the only linkers that support thin archives are

So far I have really only tested with gold (still doing windowns setup to test the new lld).

Last but not least, the thin archive is in gnu format. If adding support to OS X (lld or ld64), it might be interesting to experiment with a thin BFD format (the symbol table there has offsets into the symbol name table, making it a bit faster to use with unix .a semantics).

Cheers, Rafael

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