[llvm-dev] Compiling compiler-rt for baremetal CortexM on Ubuntu Linux

[Xia Zhou via llvm-dev]

Thanks for the info.

On Fri, Aug 9, 2019 at 5:58 PM Peter Smith <peter.smith at linaro.org> wrote:

> On Fri, 9 Aug 2019 at 00:14, Xia Zhou via llvm-dev
> <llvm-dev at lists.llvm.org> wrote:
> >
> > Hello,
> > I want to build LLVM/Compiler-rt for baremetal targets like Cortex-M3.
> By adopting CMake options from
> http://llvm.1065342.n5.nabble.com/llvm-dev-Compiling-for-baremetal-ARMv4-on-Ubuntu-Linux-tp124226p124500.html,
> I can only build "libclang_rt.builtins-x86_64.a" in lib/linux, but what I
> want to build is "libclang_rt.builtins.arm.a".
> >
> > My CMake options are:
> > cmake -G Ninja  DBAREMETAL_ARMV6M_SYSROOT=${ARMEABI5GCC}
> -DBAREMETAL_ARMV7M_SYSROOT=${ARMEABI5GCC}
> -DBAREMETAL_ARMV7EM_SYSROOT=${ARMEABI5GCC} -DCMAKE_BUILD_TYPE=Release
> -C/home/llvm-project/clang/cmake/caches/BaremetalARM.cmake
> /home/llvm-project/llvm/runtimes/compiler-rt
> >
> > with
> > echo $ARMEABI5GCC
> > /home/gcc-arm-none-eabi-5_4-2016q3/arm-none-eabi
> >
> > Does anyone know how to fix this problem?
>
> I can get you a bit further but it looks like that particular CMake
> recipe has bitrotted as it doesn't work at all with the monorepo
> layout, and looks like it has some problems even with the old
> directory layout.
>
> Going from a monorepo I did the following:
> cd /path/to/llvm-project/llvm/runtimes
> ln -s  /path/to/llvm-project/compiler-rt compiler-rt
> cd /path/to/llvm-project/llvm/tools
> ln -s /path/to/llvm-project/clang clang
> ln -s /path/to/llvm-project/lld lld
> cmake -G Ninja  DBAREMETAL_ARMV6M_SYSROOT=${ARMEABI5GCC}
> -DBAREMETAL_ARMV7M_SYSROOT=${ARMEABI5GCC}
> -DBAREMETAL_ARMV7EM_SYSROOT=${ARMEABI5GCC} -DCMAKE_BUILD_TYPE=Release
> -C/path/to/llvm-project/clang/cmake/caches/BaremetalARM.cmake
> /path/to/llvm-project/llvm
>
> This will attempt to build the builtins for cortex-m, unfortunately it
> will fail due to a couple of reasons:
> - Several CMAKE variables passed in by the recipe are ignored by the
> builtins, which is likely the root cause of the failures.
> - The -DCMAKE_SYSROOT= $ARMEABI5GCC is passed through correctly,
> unfortunately this doesn't result in a --sysroot=$ARMEABI5GCC being
> passed to the compile commands so they fail with can't find stddef.h
>
> I strongly recommend not using the recipe and instead feeding the
> CMake for the builtins directly. There is some information in
> https://llvm.org/docs/HowToCrossCompileBuiltinsOnArm.html
>
> Peter
>
> > Thanks in advance!
> > Xia Zhou
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > https://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.llvm.org/pipermail/llvm-dev/attachments/20190817/08e1feb6/attachment-0001.html>