LLVM Compiler Infrastructure


The package provided under the name “llvm” in the software repository of Discoverer HPC adopts the programming code of LLVM Compiler Infrastructure project without applying any modifications to that code. In case you need specific LLVM build provided and supported by other vendors of compiler packages, check Intel oneAPI, AMD Optimized Compiler Collection (AOCC), and NVIDIA HPC SDK.

Supported versions

To check which versions of LLVM Compiler Infrastructure are currently supported on Discoverer, execute on the login node:

module avail llvm

The LLVM build, available in the software repository, is supported by HPC Discoverer team. Below is the complete list of LLVM projects and runtimes included:

  • Projects
    • clang
    • clang-tools-extra
    • flang
    • libclc
    • lld
    • lldb
    • mlir
    • openmp
    • polly
    • pstl
  • Runtimes
    • libcxx
    • libcxxabi
    • libunwind
    • compiler-rt
    • libc

The LLVM compilers are equipped with internal code generators for producing code optimized for running on major NVIDIA, Intel, and AMD GPU accelerators with HPC compute capabilities. While such GPU accelerators are not yet available on Discoverer’s compute nodes, a new, brand-new GPU partition is on the way.


Our LLVM builds are compiling time self-sufficient. For each new version of the vanilla LLVM code, we use GCC to initially compile that code, and then we use the compilers and libraries from that compilation to compile the code again. It is important to declare here that the LLVM compilers, tools, and libraries we host depend only on the system libraries that come with the Linux distribution (which includes libstdc++). The only exception is to load an alternative version of binutils to support the LLVMgold plugin. But that binutils package also falls back to the system libraries.

The implemented compilation recipe is publicly available at https://gitlab.discoverer.bg/vkolev/recipes/-/tree/main/llvm


To access the latest LLVM compilers, load the environment module llvm/latest:

module load llvm/latest

or select a particular version.

LLVM compilers

The LLVM build includes the following C, C++, and Fortran compiler executables:



Here flang points to flang-new via symlink. Unlike the flang in AMD AOCC, we do not symlink flang to clang.

Compiler optimization flags for AMD Zen2 CPU


The compute nodes of Discoverer HPC are equipped with AMD EPYC 7H12 64-Core processors, which implies AMD Zen2 CPU architecture, whereupon AXV 256 is the highest SIMD instruction (no AVX 512 is available).

Sticking to the following compiler flags can be profitable during the compile-time optimization on AMD Zen2:

-march=znver2 -mtune=native

and it is up on you to add -mfma to that set.

For example:

clang -march=znver2 -mtune=native ...
clang++ -march=znver2 -mtune=native ...
flang -march=znver2 -mtune=native ...

More on the supported compiler flags and types of optimizations: LLVM User Guides / Optimizations

Interaction with CMake

It is recommended to specify explicitly the compiler executables:


The corresponding optimization compiler flags can be passed to cmake the usual way:

-DCMAKE_C_FLAGS="-march=znver2 -mtune=native"
-DCMAKE_CXX_FLAGS="-march=znver2 -mtune=native"
-DCMAKE_Fortran_FLAGS="-march=znver2 -mtune=native"

Getting help

See Getting help