[llvm-dev] Building LLVM through Bazel

Thu Aug 16 13:28:39 PDT 2018

I tried running all the commands in the compile_commands.json (thanks for
pointing that out), but it runs into the same "No such file or directory:
*.inc". I don't see those files built anywhere in that list. Does it take
tblgen into account?

Doug

On Thu, Aug 16, 2018, 1:02 PM Sanjoy Das <sanjoy at playingwithpointers.com>
wrote:

> TensorFlow uses bazel to build LLVM:
> https://github.com/tensorflow/tensorflow/tree/master/third_party/llvm
> The script that generates llvm.autogenerated.BUILD is not open sourced
> yet unfortunately but looking skimming through the generated file
> should give you a rough idea of what's involved.
>
> -- Sanjoy
> On Thu, Aug 16, 2018 at 11:16 AM Isaiah Norton via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> >>
> >> You could look at the cmake+ninja (or other build system) build and
> dump the commands it executes (I think ninja produces a log, or can do so)
> which should show you all the commands needed to build any part of LLVM.
> >
> >
> > There's a switch to dump all compiler commands as a JSON file:
> >
> >
> https://cmake.org/cmake/help/v3.12/variable/CMAKE_EXPORT_COMPILE_COMMANDS.html
> >
> > On Wed, Aug 15, 2018 at 8:30 PM David Blaikie via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> >>
> >>
> >>
> >> On Wed, Aug 15, 2018 at 2:05 PM Douglas Parker <dgp1130422 at gmail.com>
> wrote:
> >>>
> >>> I believe it would be possible to run a cmake command to generate a
> BUILD file, though I don't know if that would be easier to maintain on the
> LLVM side. Would definitely be happy to see direct support, though I was
> just trying to figure out what's needed to hack this together on my end.
> >>>
> >>> I guess my real question is what underlying commands are necessary to
> build all the source files (without actually compiling the C/C++)? If I can
> understand how to do this manually with terminal/cmake/tblgen, then I could
> probably get it to work with Bazel.
> >>>
> >>> Looking at TensorFlow's setup, it looks like tblgen has dependencies
> on support which goes down to zlib and gets a lot of complexity there. I
> get the impression that tblgen isn't so complicated as to require all that.
> What would be the minimum steps to build tblgen from source?
> >>
> >>
> >> You could look at the cmake+ninja (or other build system) build and
> dump the commands it executes (I think ninja produces a log, or can do so)
> which should show you all the commands needed to build any part of LLVM.
> >>
> >> But yeah, I think you do have to build support to build tblgen, to run
> tblgen to generate the rest of the files to continue the build.
> >>
> >> - Dave
> >>
> >>>
> >>>
> >>> Doug
> >>>
> >>> On Wed, Aug 15, 2018 at 1:28 PM Chris Bieneman <chris.bieneman at me.com>
> wrote:
> >>>>
> >>>> There have been discussions about adding a Bazel generator before:
> >>>> https://cmake.org/pipermail/cmake-developers/2017-July/030144.html
> >>>>
> >>>> There does seem to be interest in having that support in CMake, and I
> can't imagine any insurmountable reason why it couldn't be done. The real
> issue is that nobody has put in the time to do it.
> >>>>
> >>>> -Chris
> >>>>
> >>>> On Aug 15, 2018, at 11:21 AM, David Blaikie via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> >>>>
> >>>>
> >>>>
> >>>> On Wed, Aug 15, 2018 at 10:04 AM Chris Lattner <clattner at nondot.org>
> wrote:
> >>>>>
> >>>>>
> >>>>>
> >>>>> > On Aug 14, 2018, at 2:43 PM, David Blaikie via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
> >>>>> >
> >>>>> > Yeah - not sure we're quite at the point where LLVM wants to start
> supporting two build systems again (used to be Configure+Make and the CMake
> system, now it's just the Cmake system), but if you want to make it work
> out-of-tree it shouldn't be too difficult (Google does this internally with
> the internal version of Bazel). Writing a short BUILD extension for running
> tblgen should be possible without too much complexity - not sure what
> Tensorflow is doing that makes its solution so complicated, it doesn't seem
> like it should be terribly hard, just a genrule to run tblgen and generate
> the appropriate files from the td files.
> >>>>>
> >>>>> Would it be technically possible for cmake to generate bazel files?
> If so, it seems that that could be a great bridge, and useful to other
> projects as well.
> >>>>
> >>>>
> >>>> /maybe/? It's an interesting thought - not sure I know enough about
> either build system to have a very informed opinion here, though.
> >>>>
> >>>> - Dave
> >>>>
> >>>>>
> >>>>>
> >>>>> -Chris
> >>>>>
> >>>> _______________________________________________
> >>>> LLVM Developers mailing list
> >>>> llvm-dev at lists.llvm.org
> >>>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> >>>>
> >>>>
> >> _______________________________________________
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> >> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> >
> > _______________________________________________
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>
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