[LLVMdev] compiler-rt CMake build

[Alexey Samsonov]

On Thu, Mar 20, 2014 at 10:12 PM, Greg Fitzgerald <garious at gmail.com> wrote:

> > ExternalProject_Add(compiler-rt ...)
>
> So that was quite the experiment.  Looking at
> clang/runtime/CMakeLists.txt, I'm not seeing a lot of bang for buck
> here, and it looks like this file is prone to bit rot.


Could you please elaborate on this? In fact, I don't plan to give up on
this experiment.
On the contrary, I wanted to move LLVM_BUILD_EXTERNAL_COMPILER_RT to the
bots, migrate the workflow of our team to use this mode, and eventually
make it the default.

The problem is that we want top-level targets from compiler-rt build tree
be visible in the llvm/clang
top-level build tree. I thought this could be achieved by ugly propagation
of top-level compiler-rt
targets with add_custom_target() command. (like I did this for
check-compiler-rt command).



>  I think we
> should consider punting on this one and looking for a more incremental
> strategy.  For instance, how about starting by moving the call
> 'add_llvm_external_project(compiler-rt)' from
> llvm/projects/CMakesLists.txt to clang/runtime?  We can tweak this
> macro (or a clang variant) to optionally do something like:
>
>     include(AddCompilerRt)
>
> That way if CMAKE_PREFIX_PATH includes a path to the compiler-rt
> install directory, it can import all the same build targets that would
> be created by add_subdirectory(compiler-rt).
>

Probably I don't understand how CMAKE_PREFIX_PATH works. How can top-level
targets from one build tree be visible in another build tree?


>
> If I were to use CMake's ExternalProject feature, it would be from a
> top-level superproject.  I would use it to manage dependencies and to
> populate CMAKE_PREFIX_PATH for each dependency.  CMake, Make or a
> package manager, it wouldn't matter which you used for this part (I've
> used Make for this).  Ultimately, you want to end up with a top-level
> build that performs the following:
>
>     mkdir -p llvm/out && cd llvm/out
>     cmake .. -DCMAKE_INSTALL_PREFIX=ship
>     ninja check-all install
>     cd -
>
>     mkdir -p compiler-rt/out && cd compiler-rt/out
>     cmake .. -DCMAKE_PREFIX_PATH=`pwd`/../../llvm/out/ship
> -DCMAKE_INSTALL_PREFIX=ship
>     ninja check-all install
>     cd -
>
>     mkdir -p clang/out && cd clang/out
>     cmake ..
>  -DCMAKE_PREFIX_PATH=`pwd`/../../llvm/out/ship:`pwd`/../../compiler-rt/out/ship
> -DCMAKE_INSTALL_PREFIX=ship
>     ninja check-all install
>     cd -
>
> In this scenario, the compiler-rt build creates a cmake module that
> clang includes.  It uses that cmake module to find the compiler-rt
> install targets and copy them into "lib/clang/<version>".  The clang
> build then calls 'add_subdirectory' on the compiler-rt 'test'
> directory, pointing it to the just-built-clang.  So the dependency
> tree for clang is:
>
>     sanitizer-tests -> clang -> compiler-rt -> c-compiler
>


... But we want to build compiler-rt libraries with just-built Clang as
well. This is what
Makefile-based build does, and what we can benefit from.


>
> Thoughts?
>
> Thanks,
> Greg
>
>
> On Thu, Feb 27, 2014 at 1:19 AM, Alexey Samsonov <samsonov at google.com>
> wrote:
> >
> > On Wed, Feb 26, 2014 at 9:58 PM, Brad King <brad.king at kitware.com>
> wrote:
> >>
> >> On 02/26/2014 12:43 PM, Alexey Samsonov wrote:
> >> > Do you think it makes sense to land my ExternalProject_Add patch
> >> > so that others can experiment with it? I can add quit with a
> >> > fatal_error/warning if the build tree rules are generated with Ninja.
> >>
> >> Since it is conditional on LLVM_BUILD_EXTERNAL_COMPILER_RT, yes.
> >
> >
> > Submitted as r202367.
> >
> >>
> >>
> >> > parallelism doesn't work when I run "make check-compiler-rt -j8"
> >> > in the original build tree, presumably because we call
> >> > "cd /path/to/compiler-rt/build/tree && make check-all" there.
> >>
> >> Right.  The ExternalProject module has a special case for the
> >> Makefile generators to make with $(MAKE) instead of "make":
> >>
> >>
> >>
> http://cmake.org/gitweb?p=cmake.git;a=blob;f=Modules/ExternalProject.cmake;hb=v2.8.12.2#l846
> >>
> >> so that flags like -j propagate automatically.  You could do
> >> that too:
> >>
> >>   if(CMAKE_GENERATOR MATCHES "Make")
> >>     set(check_compiler_rt "$(MAKE)" "check-all")
> >>   else()
> >>     set(check_compiler_rt ${CMAKE_COMMAND} --build .
> >>       --target check-all --config $<CONFIGURATION>)
> >>   endif()
> >>
> >>   ExternalProject_Get_Property(compiler-rt BINARY_DIR)
> >>   add_custom_target(check-compiler-rt
> >>     COMMAND ${check_compiler_rt}
> >>     DEPENDS compiler-rt
> >>     WORKING_DIRECTORY ${BINARY_DIR}
> >>     VERBATIM
> >>     )
> >>
> >
> > This worked, thanks! Currently I also print fatal_error message if I
> detect
> > Ninja as a CMAKE_GENERATOR.
> >
> >
> > --
> > Alexey Samsonov, MSK
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> >
>



-- 
Alexey Samsonov, MSK
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