[LLVMdev] compiler-rt CMake build

[Alexey Samsonov]

On Thu, Feb 6, 2014 at 7:57 PM, Jean-Daniel Dupas <devlists at shadowlab.org>wrote:

>
> Le 6 févr. 2014 à 16:20, Brad King <brad.king at kitware.com> a écrit :
>
> > On 02/06/2014 08:12 AM, Alexey Samsonov wrote:
> >> Please note that it makes a lot of sense to built compiler-rt (and
> sanitizers) with just-built
> >> Clang. In fact, even though we should support building it with another
> compilers (gcc, MSVC),
> >> using just-built-Clang should be a default scenario, like it is in
> configure+make build.
> >
> > This is possible with CMake using the ExternalProject module:
> >
> >
> http://www.cmake.org/cmake/help/v2.8.12/cmake.html#module:ExternalProject
> >
> > The add_llvm_external_project macro already in LLVM could be taught
> > to call ExternalProject_Add instead of add_subdirectory.  This could
> > create a custom target with dependencies appropriately configured to
> > build after Clang.  The custom target would run CMake to configure the
> > project like an outside build and then launch the build.
> >
> > IIUC there is a desire for Clang to be able to be built externally to
> > LLVM rather than subsumed into its build process.  The top-level
> > CMakeLists.txt file of Clang already has code to do that, though it
> > can be much cleaner after my patches to LLVM to provide LLVMConfig.cmake
> > are integrated.  Then it will even be possible to build Clang using
> > CMake against a LLVM that was built and installed using configure+make.
> >
> > If one would like to drive compiler-rt as part of testing a Clang built
> > outside of LLVM then the appropriate place for the ExternalProject_Add
> > call would be inside the build of Clang.
>
> Look like what we need to build compiler-rt. Actually the makefile
> responsible to launch the compiler-rt build is in clang/runtime/compiler-rt.
> Using ExternalProject_Add, we can probably add the CMake part beside that
> existing file, so everything will be at the same place.
>

OK, I feel like I need to learn more about ExternalProject_Add magic. I
have a few
quick questions for people with knowledge - currently:
1) "compiler-rt"'s CMake needs to know about targets in the Clang build
tree ("clang") and
in LLVM build tree ("FileCheck", llvm-* command-line tools, googletest
etc.), and uses common
macro from LLVM's CMake modules like "configute_lit_site_cfg",
"parse_arguments".
2) top-level targets from compiler-rt's CMake files are visible at the root
of LLVM's build tree,
so that I can run "make check-asan" or even "make clang_rt.asan-x86_64"
from the root of
the build tree.

Will we easily retain all these capabilities if we turn compiler-rt into an
external project?


>
> > Either way, from a quick glance at the top-level CMakeLists.txt file
> > in compiler-rt it appears to want to know a bunch of information about
> > Clang rather than LLVM.  In this case having Clang export enough info
> > for applications to write find_package(Clang) would make sense.  This
> > is possible to do an can be implemented using techniques similar to
> > that in my proposed LLVMConfig.cmake patch series.
> >
> > -Brad
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
>
> -- Jean-Daniel
>
>
>
>
>
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-- 
Alexey Samsonov, MSK
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