llvm dev - Aug 2017 - Cross compiling C++ program

On Fri, Aug 04, 2017 at 04:03:35PM -0600, Jonathan Roelofs
wrote:
> > > 1) Pick a directory as your sysroot
> > ~/arm-sysroot
> >
> > > 2) Install the libc headers there (without having built it)
> > What I did was mv musl-*/include ~/arm-sysroot/usr/include.
>
> I think you need to copy them, not move them.
On a new directories and fresh untar of musl, I don't think there's a
difference

> > > 3) Build clang w/ baremetal cache, pointing it at the partially
built
> > > sysroot.
> >   cmake -G 'Unix Makefiles'
-DBAREMETAL_ARMV7EM_SYSROOT=~/arm-sysroot -C
../../code/clang/cmake/caches/BaremetalARM.cmake ../../code/clang
>
> Sorry, I wasn't explicit enough. You need to define all of the
variables
> that the cache is looking for.
>
> > loading initial cache file
../../code/clang/cmake/caches/BaremetalARM.cmake
> > -- Found LLVM_CONFIG as /usr/local/bin/llvm-config
> > -- Building with -fPIC
> > -- Could NOT find Z3 (missing:  Z3_LIBRARIES Z3_INCLUDE_DIR) (Required
is at least version "4.5")
> > -- Clang version: 4.0.1
> > CMake Error at /usr/local/llvm40/lib/cmake/llvm/LLVM-Config.cmake:203
(message):
> >    Library `BinaryFormat' not found in list of llvm libraries.
> > Call Stack (most recent call first):
> >    /usr/local/llvm40/lib/cmake/llvm/AddLLVM.cmake:508
(llvm_map_components_to_libnames)
> >    cmake/modules/AddClang.cmake:86 (llvm_add_library)
> >    lib/AST/CMakeLists.txt:6 (add_clang_library)
> >
> > -- Configuring incomplete, errors occurred!
> > See also
"/usr/home/meka/repos/clang/build/clang/CMakeFiles/CMakeOutput.log".
>
> I think it found an installed llvm, and is trying to use that to build
clang
> against. First, the clang and llvm's versions have to match. Second,
when I
> mentioned building clang, I really meant building llvm+clang... sorry.
>
> $ cmake -G 'Unix Makefiles'
-DBAREMETAL_ARMV7EM_SYSROOT=~/arm-sysroot -C
> path/to/copy/of/edited/BaremetalARM.cmake path/to/llvm
>
> Where your path/to/llvm has the symlinks:
>
>   *  path/to/llvm/tools/clang -> path/to/clang
ln -s `which clang40` path/to/llvm/tools/clang
>   *  path/to/llvm/runtimes/compiler_rt path/to/compiler_rt
ln -s path/to/llvm/projects/compiler-rt path/to/llvm/runtimes/compiler_rt

Is that right?

>
> And by "edited BaremetalARM.cmake" I mean you can strip out the
other
> targets in there that you don't need.
So I have copied BaremetalARM.cmake into llvm/cmake/caches/BaremetalARM.cmake to
be able to alter it, I've put all other repos in llvm/projects and the
command is:

# cmake -G 'Unix Makefiles' -DBAREMETAL_ARMV7EM_SYSROOT=~/arm-sysroot
-DBAREMETAL_ARMV6M_SYSROOT=~/arm-sysroot
-DBAREMETAL_ARMV7M_SYSROOT=~/arm-sysroot -C
../../code/llvm/cmake/caches/BaremetalARM.cmake ../../code/llvm

Before adding all repos into llvm/projects, it complained about 'Specified
distribution component 'clang' doesn't have a target' (just an
example). Now I have 'Specified distribution component
'builtins-armv6m-none-eabi' doesn't have a target' as error.
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On 8/4/17 4:29 PM, Goran Mekić wrote:
> On Fri, Aug 04, 2017 at 04:03:35PM -0600, Jonathan Roelofs wrote:
>>>> 1) Pick a directory as your sysroot
>>> ~/arm-sysroot
>>>
>>>> 2) Install the libc headers there (without having built it)
>>> What I did was mv musl-*/include ~/arm-sysroot/usr/include.
>> I think you need to copy them, not move them.
> On a new directories and fresh untar of musl, I don't think there's
a difference
I was assuming you'd want to build it from the same sources later...
>
>
>>>> 3) Build clang w/ baremetal cache, pointing it at the partially
built
>>>> sysroot.
>>>    cmake -G 'Unix Makefiles'
-DBAREMETAL_ARMV7EM_SYSROOT=~/arm-sysroot -C
../../code/clang/cmake/caches/BaremetalARM.cmake ../../code/clang
>> Sorry, I wasn't explicit enough. You need to define all of the
variables
>> that the cache is looking for.
>>
>>> loading initial cache file
../../code/clang/cmake/caches/BaremetalARM.cmake
>>> -- Found LLVM_CONFIG as /usr/local/bin/llvm-config
>>> -- Building with -fPIC
>>> -- Could NOT find Z3 (missing:  Z3_LIBRARIES Z3_INCLUDE_DIR)
(Required is at least version "4.5")
>>> -- Clang version: 4.0.1
>>> CMake Error at
/usr/local/llvm40/lib/cmake/llvm/LLVM-Config.cmake:203 (message):
>>>     Library `BinaryFormat' not found in list of llvm libraries.
>>> Call Stack (most recent call first):
>>>     /usr/local/llvm40/lib/cmake/llvm/AddLLVM.cmake:508
(llvm_map_components_to_libnames)
>>>     cmake/modules/AddClang.cmake:86 (llvm_add_library)
>>>     lib/AST/CMakeLists.txt:6 (add_clang_library)
>>>
>>> -- Configuring incomplete, errors occurred!
>>> See also
"/usr/home/meka/repos/clang/build/clang/CMakeFiles/CMakeOutput.log".
>> I think it found an installed llvm, and is trying to use that to build
clang
>> against. First, the clang and llvm's versions have to match.
Second, when I
>> mentioned building clang, I really meant building llvm+clang... sorry.
>>
>> $ cmake -G 'Unix Makefiles'
-DBAREMETAL_ARMV7EM_SYSROOT=~/arm-sysroot -C
>> path/to/copy/of/edited/BaremetalARM.cmake path/to/llvm
>>
>> Where your path/to/llvm has the symlinks:
>>
>>    *  path/to/llvm/tools/clang -> path/to/clang
> ln -s `which clang40` path/to/llvm/tools/clang
No, not the binary, the source.

The closer to top of trunk you pull the source, the easier it'll be to 
get it working. A lot of the upstreaming of baremetal support has been 
*very* recent.... "bleeding edge" recent.
>>    *  path/to/llvm/runtimes/compiler_rt path/to/compiler_rt
> ln -s path/to/llvm/projects/compiler-rt path/to/llvm/runtimes/compiler_rt
>
> Is that right?
Sorry, it should be spelled `compiler-rt`, not `compiler_rt`.
>> And by "edited BaremetalARM.cmake" I mean you can strip out
the other
>> targets in there that you don't need.
> So I have copied BaremetalARM.cmake into
llvm/cmake/caches/BaremetalARM.cmake to be able to alter it, I've put all
other repos in llvm/projects and the command is:
Leave all the others out for now. An in-tree build of them is just going 
to give you host binaries, which isn't helpful in your case. You'll have
to build them "out of tree".


Might be a helpful exercise for you to try building vanilla clang with 
runtimes for the host, before worrying about how to build everything for 
your baremetal case: 
http://llvm.org/docs/GettingStarted.html#getting-started-quickly-a-summary
>
> # cmake -G 'Unix Makefiles'
-DBAREMETAL_ARMV7EM_SYSROOT=~/arm-sysroot
-DBAREMETAL_ARMV6M_SYSROOT=~/arm-sysroot
-DBAREMETAL_ARMV7M_SYSROOT=~/arm-sysroot -C
../../code/llvm/cmake/caches/BaremetalARM.cmake ../../code/llvm
>
> Before adding all repos into llvm/projects, it complained about
'Specified distribution component 'clang' doesn't have a
target' (just an example). Now I have 'Specified distribution component
'builtins-armv6m-none-eabi' doesn't have a target' as error.
I think that error happened because you symlinked the clang binary in, 
not the source.

Jon

-- 
Jon Roelofs
jonathan at codesourcery.com
CodeSourcery / Mentor Embedded / Siemens

On Fri, Aug 04, 2017 at 04:40:44PM -0600, Jonathan Roelofs
wrote:
> Might be a helpful exercise for you to try building vanilla clang with
> runtimes for the host, before worrying about how to build everything for
> your baremetal case:
> http://llvm.org/docs/GettingStarted.html#getting-started-quickly-a-summary
I think I'll start with that, first :o)
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On Fri, Aug 04, 2017 at 04:40:44PM -0600, Jonathan Roelofs
wrote:
> Might be a helpful exercise for you to try building vanilla clang with
> runtimes for the host, before worrying about how to build everything for
> your baremetal case:
> http://llvm.org/docs/GettingStarted.html#getting-started-quickly-a-summary
So I did. :o) It was fun realizing how much Release type reduces LD memory usage
:o)

Anyway, just to be clear what "I did" means:
- llvm sources from trunk and projects/tools repos checkout under llvm
- clang-6.0 compiles "Hello World"
- make check-all fails (not sure I'm not causing it)
- make install creates everything under PREFIX

# cmake -G 'Unix Makefiles' -DCMAKE_BUILD_TYPE=Release
-DLLVM_TARGETS_TO_BUILD=X86 -DCMAKE_INSTALL_PREFIX=/tmp/x86-sysroot
../../source/llvm
# make -j4
# make install

It was fun learning how to manualy compile compiler for the first time. Now how
to cross compile for bare? Given that I have musl-1.1.16 directory and that
I'm preseeding sysroot with:

# rm -rf /tmp/barearm-sysroot
# mkdir -p /tmp/barearm-sysroot
# cp -r musl-1.1.16/include /tmp/barearm-sysroot/ # Thanx for the tip!

So I tried to use it, and clang/llvm build, but compiler-rt fails:

# cmake -G 'Unix Makefiles' -DCMAKE_BUILD_TYPE=Release
-DBAREMETAL_ARMV7EM_SYSROOT=/tmp/barearm-sysroot
-DCMAKE_INSTALL_PREFIX=/tmp/barearm-sysroot -C
../../source/llvm/cmake/caches/BaremetalARM.cmake ../../source/llvm
# make -j4
https://gist.github.com/anonymous/85cd5081a6d46a63731d970ee95b20b4

This is the BaremetalARM.cmake:
https://gist.github.com/anonymous/ff3248f08ddc99361dcc009e9f4c1020
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