On Wed, 2018-11-07 at 18:51 +0000, Emil Velikov wrote: > On Wed, 7 Nov 2018 at 18:39, Jan Vesely <jan.ves...@rutgers.edu> wrote: > > On Tue, 2018-11-06 at 12:09 +0000, Emil Velikov wrote: > > > On Thu, 1 Nov 2018 at 16:13, Michel Dänzer <mic...@daenzer.net> wrote: > > > > On 2018-11-01 5:03 p.m., Jan Vesely wrote: > > > > > On Wed, 2018-10-31 at 18:40 +0000, Emil Velikov wrote: > > > > > > On Wed, 31 Oct 2018 at 17:41, Jan Vesely <jan.ves...@rutgers.edu> > > > > > > wrote: > > > > > > > On Wed, 2018-10-31 at 17:22 +0000, Emil Velikov wrote: > > > > > > > > On Wed, 31 Oct 2018 at 16:24, Michel Dänzer > > > > > > > > <mic...@daenzer.net> wrote: > > > > > > > > > On 2018-10-31 5:19 p.m., Jan Vesely wrote: > > > > > > > > > > This might be a stupid question; is the LLVM_CONFIG env var > > > > > > > > > > remembered > > > > > > > > > > between reconfigure (touch configure.ac; make) or do I need > > > > > > > > > > to provide > > > > > > > > > > it explicitly every time configure is run? > > > > > > > > > > > > > > > > > > I don't know the answer, but agree that would be a minimum > > > > > > > > > requirement > > > > > > > > > for this change. > > > > > > > > > > > > > > > > > Nope, yet it's not really a minimum. LLVM_CONFIG has been > > > > > > > > around for > > > > > > > > years, it will work for any Mesa checkout since its inception. > > > > > > > > You can safely bisect Mesa and things will just work. > > > > > > > > > > > > > > The question is; Do I have to do "LLVM_CONFIG=..." make every time > > > > > > > bisect changes configure.ac? > > > > > > > > > > > > > You can do (although there's other options if this one seems weird) > > > > > > > > > > > > $ LLVM_CONFIG=... ../autogen.sh > > > > > > > > > > That does not answer my question. > > > > > > > > > > suppose the following sequence: > > > > > $ LLVM_CONFIG=/usr/local/llvm-4/bin/llvm-config ../mesa-src/autogen.sh > > > > > ... > > > > > llvm: yes > > > > > llvm-config: /usr/local/llvm-4/bin/llvm-config > > > > > llvm-version: 4.0.1 > > > > > ... > > > > > $ make -j128 > > > > > $ touch ../mesa-src/configure.ac > > > > > $ make -j128 > > > > > ... > > > > > llvm: yes > > > > > llvm-config: /usr/bin/llvm-config > > > > > llvm-version: 7.0.0 > > > > > ... > > > > > > > > > > the second reconfigure silently reverted back to system default llvm. > > > > > That's a loss of capabilty for me. > > > > > > > > Thanks for checking, Jan. That's a NAK from me for this patch in the > > > > current form. > > > > > > > > FWIW, LLVM_CONFIG is available in the generated Makefiles, so it might > > > > not be too hard to make this work with the environment variable. I don't > > > > know the preferred way to do that however. > > > > > > > Right, I misread the usecase :-( Sorry about that. > > > The following works like a charm: > > > > > > .../autogen.sh ac_cv_path_LLVM_CONFIG=/... > > > make > > > touch .../configure.ac > > > make > > > > ouch, that's rather ugly. What is the reason to prefer env var vs. > > proper option (like --with-llvm-config)? > > meson also seems to prefer env var for some reason. > > I don't mind spending the time to send out the patches, but I'd like to > > make sure it's not a wasted effort. > > > From a general distribution POV, adding llvm-config to every project > 'feels' wasteful IMHO. Even if we ignore the "feels" part, there's the > aspect of duplicating the same code in XX projects. > Which with due time will result in a behavioural shift as copies diverge. > > In Mesa the toggle conflicts, in some weird ways, with the existing > --with-clang-libdir
The idea would be to have one --with-llvm-config switch that subsumes all llvm related options (except maybe static vs. dynamic linking). I don't get the argument about other projects. Not all projects need to support multiple llvm versions. For those that do provide that option, having a configure, ehm, option sounds like the most straightforward way. If divergence from other projects is a worry, then the solution can be upstreamed to the autoconf archive to replace the current ax_llvm [0]. libclc (another piece of the mesa based OpenCL stack) has provided ' --with-llvm-config' option since Jan 2012, so it'd be nice to follow suite. I don't understand how using env var addresses any of that. > Now stepping back to look at the big picture: > Ideally LLVM/Clang would provide .pc files like nearly every project > in wild. LLVM 7.0 doesn't seem to be shipping any, so we need [ideally > very small] solution in the meanwhile. The reality is that LLVM doesn't, and probably won't ever provide .pc file. The bug for this was open in 2011 against LLVM 2.8 [1]. I don't know if there's a policy or just lack of volunteers, but hoping that mesa only needs a stop gap solution until it happens is unrealistic. regards, Jan [0] https://www.gnu.org/software/autoconf-archive/ax_llvm.html#ax_llvm [1] https://bugs.llvm.org/show_bug.cgi?id=9405 > > HTH > Emil
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