[llvm-dev] llvm cross compilation issue

[Денис Онищенко via llvm-dev]

But besides the fact that building llvm is very time-consuming, there
is another serious problem with this method: llvm-config built in this
way will return incorrect results that are related to the host, not
the target.



2020-09-17 16:47 GMT+03:00, Tobias Hieta <tobias at plexapp.com>:
> Hello,
>
> There might be a smarter way - but I just build the tree twice:
>
> mkdir native ; cd native ; cmake -GNinja .. ; ninja
> mkdir target ; cd target ; cmake -GNinja
> -DCMAKE_TOOLCHAIN_FILE=cross.cmake
> -DLLVM_TABLEGEN_PATH=../native/bin/llvm-tblgen ..
>
> I know there are runtime builds as well - but I am not familiar with it.
>
> -- Tobias
>
> On Thu, Sep 17, 2020 at 3:28 PM Денис Онищенко via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
>>
>> I am trying to compile llvm using a toolchain file where I have
>> specified the target system and compilers as suggested at
>> https://cmake.org/cmake/help/latest/manual/cmake-toolchains.7.html#cross-compilation-tool
>> chain:
>>
>> set(CMAKE_SYSTEM_NAME Linux)
>> set(CMAKE_SYSTEM_PROCESSOR arm)
>>
>> set(CMAKE_C_COMPILER arm-unknown-linux-gnueabi-gcc)
>> set(CMAKE_CXX_COMPILER arm-unknown-linux-gnueabi-g++)
>>
>> But the problem is that native tools like llvm-config, llvm-tblgen and
>> clang-tblgen, which must be built by the native compiler, are also
>> created by the target compiler.
>>
>> What cmake / "toolchain file" options should I use to use the native
>> (host) compiler for these native tools (which are placed in the NATIVE
>> subdirectory), and target compilers for other binaries and libraries?
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>