[llvm] r274270 - [CMake] Module builds depend on target intrinsics_gen to be built first.

[Vassil Vassilev via llvm-commits]

On 18/07/17 15:07, NAKAMURA Takumi wrote:
> I suppose there'd be no issue in trunk's modulemap as far as I 
> investigated. Could we revert it?
We maybe stopped seeing it because of the current order of includes 
which trigger the implicit module builds. This mostly used to happen if 
we have a header dependency on content of module LLVM_intrinsic_gen. If 
we want to revert this we probably need to impose more restrictions on 
the way we trigger implicit module builds.

OTOH this adds an extra dependency which might be a build bottleneck. If 
you opt to revert it please keep in mind the issue could reappear.
>
> On Fri, Jul 1, 2016 at 5:42 AM Vassil Vassilev via llvm-commits 
> <llvm-commits at lists.llvm.org <mailto:llvm-commits at lists.llvm.org>> wrote:
>
>     Author: vvassilev
>     Date: Thu Jun 30 15:35:56 2016
>     New Revision: 274270
>
>     URL: http://llvm.org/viewvc/llvm-project?rev=274270&view=rev
>     Log:
>     [CMake] Module builds depend on target intrinsics_gen to be built
>     first.
>
>     When compiling with modules, header A and B can be in the same
>     module M.
>     B depends on intrinsics_gen and A doesn't. Compiling a source file
>     #include-ing
>     header A, we implicitly request module M to be built. It puts
>     header A and B in
>     the same TU and tries to build them. Since B depends on
>     intrinsics_gen (which
>     might not be built yet) we run into build failures.
>
>     This should fix our modules buildbot.
>
>     Patch reviewed by Chris Bieneman.
>
>     Modified:
>         llvm/trunk/CMakeLists.txt
>
>     Modified: llvm/trunk/CMakeLists.txt
>     URL:
>     http://llvm.org/viewvc/llvm-project/llvm/trunk/CMakeLists.txt?rev=274270&r1=274269&r2=274270&view=diff
>     ==============================================================================
>     --- llvm/trunk/CMakeLists.txt (original)
>     +++ llvm/trunk/CMakeLists.txt Thu Jun 30 15:35:56 2016
>     @@ -700,6 +700,15 @@ add_subdirectory(lib/TableGen)
>
>      add_subdirectory(utils/TableGen)
>
>     +# Force target to be built as soon as possible. Clang modules
>     builds depend
>     +# header-wise on it as they ship all headers from the umbrella
>     folders. Building
>     +# an entire module might include header, which depends on
>     intrinsics_gen. This
>     +# should be right after LLVMSupport and LLVMTableGen otherwise we
>     introduce a
>     +# circular dependence.
>     +if (LLVM_ENABLE_MODULES)
>     +  list(APPEND LLVM_COMMON_DEPENDS intrinsics_gen)
>     +endif(LLVM_ENABLE_MODULES)
>     +
>      add_subdirectory(include/llvm)
>
>      add_subdirectory(lib)
>
>
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