[llvm-dev] FYI: Ninja-build user may use CMake-3.9

[Martell Malone via llvm-dev]

Hey Reid,

I tracked down the relevant gitlab issue, merge request and commits on
kitware.
https://gitlab.kitware.com/cmake/cmake/issues/15555
https://gitlab.kitware.com/cmake/cmake/merge_requests/430
Ben from kitware seems to have done the heavy lifting here

Best,
Martell


On Thu, Jul 20, 2017 at 5:16 PM, Reid Kleckner via llvm-dev <
llvm-dev at lists.llvm.org> wrote:

> This is great news! Do we know who contributed the changes to cut the
> extra library dependencies?
>
> Do you think we should remove ENABLE_OBJLIB to simplify our CMake files in
> the near future? It seems to me that anyone who cares about highly parallel
> build throughput can upgrade CMake to get the good behavior. It's probably
> easier and less error-prone than maintaining a special build configuration.
>
> On Thu, Jul 20, 2017 at 8:31 AM, NAKAMURA Takumi via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> This is useful for developer who uses multicore builder.
>> https://cmake.org/cmake/help/v3.9/release/3.9.html#other-changes
>>
>>
>>    - The Ninja
>>    <https://cmake.org/cmake/help/v3.9/generator/Ninja.html#generator:Ninja> generator
>>    has loosened the dependencies of object compilation. Object compilation now
>>    depends only on custom targets and custom commands associated with
>>    libraries on which the object’s target depends and no longer depends on the
>>    libraries themselves. Source files in dependent targets may now compile
>>    without waiting for their targets’ dependencies to link.
>>
>> With BUILD_SHARED_LIBS, compiling units don't wait for preceding shared
>> libs.
>> See also; http://bb.pgr.jp/builders/i686-mingw32-RA-on-linux
>> Regardless of BUILD_SHARED_LIBS, compile units in add_executable() don't
>> wait for preceding libraries,
>> but targets by add_dependencies().
>>
>> It doesn't break anything in llvm tree. Assume;
>>   add_executable(foo foo.cpp)
>>   target_link_libraries(foo LLVMCore) # depends on intrinsics_gen
>> Compiling foo.cpp doesn't wait for LLVMCore, but intrinsics_gen.
>> Linking foo waits for LLVMCore.
>>
>> I have been working for cutting dependencies to increase parallelism.
>> For example, I introduced ENABLE_OBJLIB.
>> See also, https://reviews.llvm.org/rL305635
>> Ninja with CMake-3.9 doesn't require parallelize with objlib.
>>
>> I love ninja-build.
>>
>> Thanks,
>> Takumi
>>
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>> llvm-dev at lists.llvm.org
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>>
>>
>
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