[Docs] What versions of LLVM exactly to use?

jchia commented 8 months ago

Install from Source

The page at https://tvm.apache.org/docs/install/from_source.html says this about LLVM:

We highly recommend to build with LLVM to enable all the features.

Additions/Changes Requested

But I cannot figure out which versions of LLVM are acceptable. On Ubuntu 20.04, I have clang-12 and llvm-12-dev installed from the official Ubuntu focal-updates repo, as well as clang-19 and libpolly-19-dev installed from http://apt.llvm.org/focal/ llvm-toolchain-focal main.

In my config.cmake, I tried setting USE_LLVM to /usr/lib/llvm-12/bin/llvm-config and /usr/lib/llvm-19/bin/llvm-config for ninja builds. Neither worked.

With 12:

/home/jchia/gh/tvm/src/target/llvm/llvm_module.cc:502:38: error: ‘x86’ is not a namespace-name
  502 |   using namespace llvm::sys::detail::x86;

With 19:

FAILED: CMakeFiles/tvm_objs.dir/src/target/llvm/llvm_instance.cc.o 
ccache /usr/bin/c++ -DDMLC_USE_FOPEN64=0 -DDMLC_USE_LOGGING_LIBRARY="<tvm/runtime/logging.h>" -DNDEBUG -DNDEBUG=1 -DTVM_GRAPH_EXECUTOR_TENSORRT -DTVM_INDEX_DEFAULT_I64=1 -DTVM_KALLOC_ALIGNMENT=64 -DTVM_LLVM_VERSION=190 -DTVM_THREADPOOL_USE_OPENMP=0 -DTVM_USE_LIBBACKTRACE=1 -DUSE_FALLBACK_STL_MAP=0 -DUSE_MICRO_STANDALONE_RUNTIME=1 -D_GNU_SOURCE -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -DDMLC_ENABLE_RTTI=0 -I/home/jchia/gh/tvm/include -I/home/jchia/gh/tvm/build/libbacktrace/include -I/home/jchia/gh/tvm/3rdparty/libcrc/include -isystem /home/jchia/gh/tvm/3rdparty/dlpack/include -isystem /home/jchia/gh/tvm/3rdparty/dmlc-core/include -isystem /home/jchia/gh/tvm/3rdparty/rang/include -isystem /home/jchia/gh/tvm/3rdparty/compiler-rt -isystem /home/jchia/gh/tvm/3rdparty/picojson -isystem /home/jchia/gh/tvm/build/crt_config -isystem /usr/local/cuda/include -isystem /usr/lib/llvm-19/include -std=c++17 -faligned-new -O2 -Wall -fPIC  -fno-rtti -MD -MT CMakeFiles/tvm_objs.dir/src/target/llvm/llvm_instance.cc.o -MF CMakeFiles/tvm_objs.dir/src/target/llvm/llvm_instance.cc.o.d -o CMakeFiles/tvm_objs.dir/src/target/llvm/llvm_instance.cc.o -c /home/jchia/gh/tvm/src/target/llvm/llvm_instance.cc
/home/jchia/gh/tvm/src/target/llvm/llvm_instance.cc:45:10: fatal error: llvm/Support/Host.h: No such file or directory
   45 | #include <llvm/Support/Host.h>

Could you clarify:

Which versions of LLVM can be used.
Why exactly LLVM is good/necessary, namely which features are affected and how if LLVM is not used. It's worrying to not know what downsides one is getting for not using LLVM.
Whether this part is referring to the USE_LLVM in the config.cmake or something else. E.g. do we need to do something about and CMAKE_C_COMPILER or CMAKE_CXX_COMPILER to point them to clang?

Triage

needs-triage
docs

jchia commented 8 months ago

From the llvm github repo, it appears that llvm-17 has llvm/Support/Host.h but llvm-18 and llvm-19 do not.

chensterliu commented 3 weeks ago

I met the same error for combination of (TVM v0.15.0, llvm-18). Upgrade tvm and compile TVM v0.18.0 with llvm-18 works fine for me.

apache / tvm