Error building with LLVM 20

[jakurzak]

I'm trying to switch to LLVM 20 for building QDP-JIT.
I'm getting this error:

/apps/Chroma_/qdp-jit/lib/qdp_llvm.cc:2539:2: error: no type named 'LLVMTargetMachine' in namespace 'llvm'; did you mean 'LLVMTargetMachineRef'?
 2539 |         llvm::LLVMTargetMachine &LLVMTM = static_cast<llvm::LLVMTargetMachine &>(*TargetMachine);
      |         ^~~~~~~~~~~~~~~~~~~~~~~
      |         LLVMTargetMachineRef
/apps/Chroma_/install/llvm-20/include/llvm-c/TargetMachine.h:35:41: note: 'LLVMTargetMachineRef' declared here
   35 | typedef struct LLVMOpaqueTargetMachine *LLVMTargetMachineRef;
      |                                         ^
/apps/Chroma_/qdp-jit/lib/qdp_llvm.cc:2539:48: error: no type named 'LLVMTargetMachine' in namespace 'llvm'; did you mean 'LLVMTargetMachineRef'?
 2539 |         llvm::LLVMTargetMachine &LLVMTM = static_cast<llvm::LLVMTargetMachine &>(*TargetMachine);
      |                                                       ^~~~~~~~~~~~~~~~~~~~~~~
      |                                                       LLVMTargetMachineRef
/apps/Chroma_/install/llvm-20/include/llvm-c/TargetMachine.h:35:41: note: 'LLVMTargetMachineRef' declared here
   35 | typedef struct LLVMOpaqueTargetMachine *LLVMTargetMachineRef;
      |                                         ^

My build script is:

git clone --recursive --branch devel https://github.com/JeffersonLab/qdp-jit.git
cd qdp-jit
mkdir build
cd build
cmake \
    -DCMAKE_BUILD_TYPE=RELEASE \
    -DCMAKE_C_COMPILER=${LLVM_INSTALL_ROOT}/bin/clang \
    -DCMAKE_CXX_COMPILER=${LLVM_INSTALL_ROOT}/bin/clang++ \
    -DLLVM_DIR=${LLVM_INSTALL_ROOT}/lib/cmake/llvm \
    -DLLD_DIR=${LLVM_INSTALL_ROOT}/lib/cmake/lld \
    -DGPU_TARGETS=${GPU_ARCH} \
    -DQDP_ENABLE_LLVM20=ON \
    -DBUILD_SHARED_LIBS=ON \
    -DQDP_ENABLE_BACKEND=ROCM \
    -DQDP_ENABLE_ROCM_STATS=ON \
    -DQDP_AC_ALIGNMENT_SIZE=128 \
    -DCMAKE_INSTALL_PREFIX=${QCD_INSTALL_ROOT}/qdpxx \
    -DQMP_DIR=${QCD_INSTALL_ROOT}/qmp/lib/cmake/QMP \
    -DCMAKE_PREFIX_PATH=${QCD_INSTALL_ROOT}/zstd/lib \
    -DCMAKE_C_FLAGS="-I${ROCM_PATH}/include/amd_comgr" \
    -DCMAKE_CXX_FLAGS="-I${ROCM_PATH}/include/amd_comgr" \
    ..
make -j 16
make install

It's not immediately obvious to me how to deal with this.

[fwinter]

I did a quick test with LLVM 20 and it builds fine. I used version 20.1.0 (as 20.0.x is not in their list of releases https://releases.llvm.org/) and had to change the requested version in CMake files accordingly. I'll push that change.
I guess that LLVM version is 20.0.x ?

[jakurzak]

With ROCm 6.4 I was again able to compile QDP-JIT with amdclang instead of the upstream LLVM.
apt install rocm-llvm-dev installed all the required LLVM files.
But I'm still hitting the error when trying the LLVM 20 in ROCm 7 (AMD internal builds).
The /llvm/ folders seem complete - all the header files and libraries.
Could you please share your CMake line for building QDP-JIT @fwinter?

Also, amdclang reports the LLVM version as X.0.0.
Can we possibly change the CMake check to just:

if( QDP_ENABLE_LLVM20 )
  find_package(LLVM "20" REQUIRED CONFIG)
elseif( QDP_ENABLE_LLVM19 )
  find_package(LLVM "19" REQUIRED CONFIG)
...