I am trying to compile llvm using a toolchain file where I have
specified the target system and compilers as suggested at
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?
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
I know there are runtime builds as well - but I am not familiar with it.
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
You only need to build the tools you need from native - so run
“ninja llvm-tblgen clang-tblgen llvm-config”
No idea about how to get a native llvm-config return targets config - never used that tool, hopefully someone else knows.
You need to pass -DCROSS_TOOLCHAIN_FLAGS_NATIVE="" during the cross build, to fix your build of the llvm-config/llvm-tblgen/clang-tblgen native tools.
The reason for this is that if CROSS_TOOLCHAIN_FLAGS_NATIVE isn't set, it's default initialized to pass on your CMAKE_CXX_COMPILER to the native build process as well, which won't do the right thing in this kind of cross setup.