Target triple option

[dileks]

Since I use tc-build I see in my logs:

$ grep warning: build-log_5.7.0-rc6-2-amd64-clang.txt 
dpkg-architecture: warning: specified GNU system type x86_64-linux-gnu does not match CC system type x86_64-unknown-linux-gnu, try setting a correct CC environment variable

My generated clang-10 says Target: x86_64-unknown-linux-gnu:

$ clang-10 -v
ClangBuiltLinux clang version 10.0.1 (https://github.com/llvm/llvm-project f79cd71e145c6fd005ba4dd1238128dfa0dc2cb6)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/dileks/src/llvm-toolchain/install/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

Whereas Debian's gcc-10 says Target: x86_64-linux-gnu:

$ gcc-10 -v
Using built-in specs.
COLLECT_GCC=gcc-10
COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/10/lto-wrapper
OFFLOAD_TARGET_NAMES=nvptx-none:amdgcn-amdhsa:hsa
OFFLOAD_TARGET_DEFAULT=1
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 10.1.0-1' --with-bugurl=file:///usr/share/doc/gcc-10/README.Bugs --enable-languages=c,ada,c++,go,brig,d,fortran,objc,obj-c++,m2 --prefix=/usr --with-gcc-major-version-only --program-suffix=-10 --program-prefix=x86_64-linux-gnu- --enable-shared --enable-linker-build-id --libexecdir=/usr/lib --without-included-gettext --enable-threads=posix --libdir=/usr/lib --enable-nls --enable-clocale=gnu --enable-libstdcxx-debug --enable-libstdcxx-time=yes --with-default-libstdcxx-abi=new --enable-gnu-unique-object --disable-vtable-verify --enable-plugin --enable-default-pie --with-system-zlib --enable-libphobos-checking=release --with-target-system-zlib=auto --enable-objc-gc=auto --enable-multiarch --disable-werror --with-arch-32=i686 --with-abi=m64 --with-multilib-list=m32,m64,mx32 --enable-multilib --with-tune=generic --enable-offload-targets=nvptx-none,amdgcn-amdhsa,hsa --without-cuda-driver --enable-checking=release --build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu
Thread model: posix
Supported LTO compression algorithms: zlib zstd
gcc version 10.1.0 (Debian 10.1.0-1)

So an option is desired to pass "triple"for the target(s).
Unsure which target triple options are allowed in the LLVM world.

Thanks.

[nathanchance]

I don’t really know how building kernels with dpkg works but I am fairly certain that the “unknown” part of the tuple comes from the fact that we set CLANG_VENDOR to ClangBuiltLinux. You could try adding --clang-vendor “” to build-llvm.py and seeing if that fixes it but other than that, I do not really have any solution to offer to you. If there is a way to add --target=x86_64-linux-gnu to KCFLAGS, that might also work.

[dileks]

Thanks for the feedback.

I checked the target-triple of clang-10 from llvm-toolchain-buster-10 (here: Target: x86_64-pc-linux-gnu):

# /usr/bin/clang-10 -v
clang version 10.0.1-++20200519101155+f79cd71e145-1~exp1~20200519202550.165 
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/10
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

I tried --clang-vendor “”AFAICS it needed an argument - empty string seems not to be allowed.
That's why I passed --clang-vendor “dileks" (note: with some individual versioning hacks):

$ clang-10 -v
dileks clang version 10.0.1rc1 
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/dileks/src/llvm-toolchain/install/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

Is it possible to pass individual "extra" options to tc-build?
Of course, with a check beforehand if it is allowed :-).

[dileks]

I checked debian/rules file of llvm-toolchain-10 package from sources.debian.org.

Looks like the required cmake option is -DLLVM_HOST_TRIPLE=x86_64-pc-linux-gnu.

See reference [1] to set -DLLVM_HOST_TRIPLE=arm-linux-gnueabi.

[1] https://sources.debian.org/src/llvm-toolchain-10/1:10.0.1%7E+rc1-1%7Eexp1/debian/rules/#L99

[dileks]

I tried this:

[ build-llvm.py ]

def base_cmake_defines(dirs):
...
+        # Explicitly set LLVM_HOST_TRIPLE (see <https://github.com/ClangBuiltLinux/tc-build/issues/92>). -dileks
+        'LLVM_HOST_TRIPLE': 'x86_64-pc-linux-gnu',

My build-log now says:

-- LLVM host triple: x86_64-pc-linux-gnu
-- LLVM default target triple: x86_64-pc-linux-gnu

[dileks]

I was not able to pass an empty string thus the brutal way:

[ build-llvm.py ]

def parse_parameters(root_folder):
...
-                        default="ClangBuiltLinux")
+                        default="")

With the above change together clang-10 -v says:

$ ./build/stage1/bin/clang-10 -v
clang version 10.0.1rc1 
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /home/dileks/src/llvm-toolchain/./build/stage1/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

[nathanchance]

I don't want to hardcode the host triple because the script can actually run on arm64 (it does not work great but it runs) and at the same time, I do not want to add a heuristic to the script for figuring out what the host triple should be.

Looking into handling an empty --clang-vendor probably seems worthwhile.

[dileks]

Looking into handling an empty --clang-vendor probably seems worthwhile.

Agreed and thanks for taking care @nathanchance

[dileks]

Can I pass some cmake-options together with build-llvm.py on the command-line?

CMAKE_OPTIONS=... ./build-llvm.py ...

[CMake] Pass LLVM_HOST_TRIPLE to external projects see [1].

[1] https://reviews.llvm.org/D40515

[dileks]

No good triple x86_64-pc-linux-gnu:

$ grep warning: build-log_5.7.0-rc6-4-amd64-clang.txt 
dpkg-architecture: warning: specified GNU system type x86_64-linux-gnu does not match CC system type x86_64-pc-linux-gnu, try setting a correct CC environment variable

Next try:

[ build-llvm.py ]

def base_cmake_defines(dirs):

+        # Don't append version control revision info (Git revision id) to the compiler version
+        'LLVM_APPEND_VC_REV': 'OFF',
+        # Explicitly set LLVM_HOST_TRIPLE (see <https://github.com/ClangBuiltLinux/tc-build/issues/92>). -dileks
+        'LLVM_HOST_TRIPLE': 'x86_64-linux-gnu',

[dileks]

LOL:

$ ./build/stage1/bin/clang-10 -v
clang version 10.0.1rc1 
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /home/dileks/src/llvm-toolchain/./build/stage1/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64

[dileks]

My snippet:

[ build-llvm.py ]

def base_cmake_defines(dirs):
...
+        # Explicitly set LLVM_HOST_TRIPLE to workaround target triple "x86_64-unknown-linux-gnu" on Debian
+        # Debian/testing AMD64: default: "Target: x86_64-linux-gnu" (unsupported as LLVM_HOST_TRIPLE)
+        # For details see <https://github.com/ClangBuiltLinux/tc-build/issues/92>
+        'LLVM_HOST_TRIPLE': 'x86_64-pc-linux-gnu',

You can close this if you like.

[nathanchance]

Thanks. I’ll take a look at the other issue soon hopefully.