llvm dev - Feb 2018 - Cross-compiling for ARM Cortex-A9 on x86

Hello list,

I have some problems using LLVM version 3.8.0 to cross-compile code for ARM
Cortex-A9 on x86.

I am trying to generate LLVM IR using Clang: clang -S --emit-llvm
--target=armv7a-linux-gnueabihf --sysroot=$(ARM_SYSROOT)
--gcc-toolchain=$(ARM_GCC_TOOLCHAIN) -c -o translated.ll

But somehow clang it is trying to use soft-float and I get the following error:
'gnu/stubs-soft.h' file not found

Is there any way I can specify  to use hard floating point? I have tried
-mfloat-abi=hard but Clang does not recognize it.

Please, let me know if there is any other information you need.

Thanks in advance,

Irune
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Hello Irune,

I tried to reproduce your command line options on a simple c file
containing some floating point instructions using the clang-3.8 binary
I have on my Ubuntu 16.04 machine with ARM_SYSROOT and
ARM_GCC_TOOLCHAIN configured to point at a Linaro Hard float toolchain
and clang used the hard float abi as expected. My clang-3.8 also
accepted -mfloat-abi=hard.

With my gcc toolchain the gnu/stubs-soft.h file is included from
gnu/stubs.h when __ARM_PCS_VFP is not defined.

With this in mind the only things I can think of are:
- There is something in your source code that is undefining __ARM_PCS_VFP.
- Your gcc toolchain has a different stubs.h that is always soft float.

As a first step; are you able to compile a hard float test program
that doesn't include anything from the C-library and does it use the
hard-float abi? If you can then I think there is likely to be
something in the source code or in the gcc toolchain you are
configuring against.

Regards

Peter




On 23 February 2018 at 16:40, Yarza Irune via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Hello list,
>
>
>
> I have some problems using LLVM version 3.8.0 to cross-compile code for ARM
> Cortex-A9 on x86.
>
>
>
> I am trying to generate LLVM IR using Clang: clang -S --emit-llvm
> --target=armv7a-linux-gnueabihf --sysroot=$(ARM_SYSROOT)
> --gcc-toolchain=$(ARM_GCC_TOOLCHAIN) -c -o translated.ll
>
>
>
> But somehow clang it is trying to use soft-float and I get the following
> error: ‘gnu/stubs-soft.h’ file not found
>
>
>
> Is there any way I can specify  to use hard floating point? I have tried
> -mfloat-abi=hard but Clang does not recognize it.
>
>
>
> Please, let me know if there is any other information you need.
>
>
>
> Thanks in advance,
>
>
>
> Irune
>
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>

Hello Peter,

Thanks for your help!

I was able to compile a hard float test program that didn't include anything
from the C-library. So I changed the gcc toolchain and it is working now.

Thanks again for your support.

Kind regards,

Irune
> -----Mensaje original-----
> De: Peter Smith [mailto:peter.smith at linaro.org]
> Enviado el: lunes, 26 de febrero de 2018 16:57
> Para: Yarza Irune <iyarza at ikerlan.es>
> CC: llvm-dev at lists.llvm.org
> Asunto: Re: [llvm-dev] Cross-compiling for ARM Cortex-A9 on x86
> 
> Hello Irune,
> 
> I tried to reproduce your command line options on a simple c file
containing
> some floating point instructions using the clang-3.8 binary I have on my
Ubuntu
> 16.04 machine with ARM_SYSROOT and ARM_GCC_TOOLCHAIN configured to
> point at a Linaro Hard float toolchain and clang used the hard float abi as
> expected. My clang-3.8 also accepted -mfloat-abi=hard.
> 
> With my gcc toolchain the gnu/stubs-soft.h file is included from
gnu/stubs.h
> when __ARM_PCS_VFP is not defined.
> 
> With this in mind the only things I can think of are:
> - There is something in your source code that is undefining __ARM_PCS_VFP.
> - Your gcc toolchain has a different stubs.h that is always soft float.
> 
> As a first step; are you able to compile a hard float test program that
doesn't
> include anything from the C-library and does it use the hard-float abi? If
you can
> then I think there is likely to be something in the source code or in the
gcc
> toolchain you are configuring against.
> 
> Regards
> 
> Peter
> 
> 
> 
> 
> On 23 February 2018 at 16:40, Yarza Irune via llvm-dev <llvm-
> dev at lists.llvm.org> wrote:
> > Hello list,
> >
> >
> >
> > I have some problems using LLVM version 3.8.0 to cross-compile code
> > for ARM
> > Cortex-A9 on x86.
> >
> >
> >
> > I am trying to generate LLVM IR using Clang: clang -S --emit-llvm
> > --target=armv7a-linux-gnueabihf --sysroot=$(ARM_SYSROOT)
> > --gcc-toolchain=$(ARM_GCC_TOOLCHAIN) -c -o translated.ll
> >
> >
> >
> > But somehow clang it is trying to use soft-float and I get the
> > following
> > error: ‘gnu/stubs-soft.h’ file not found
> >
> >
> >
> > Is there any way I can specify  to use hard floating point? I have
> > tried -mfloat-abi=hard but Clang does not recognize it.
> >
> >
> >
> > Please, let me know if there is any other information you need.
> >
> >
> >
> > Thanks in advance,
> >
> >
> >
> > Irune
> >
> >
> > _______________________________________________
> > LLVM Developers mailing list
> > llvm-dev at lists.llvm.org
> > http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
> >