llvm@gentoo.org Install llvm-runtimes/compiler-rt for -rtlib=compiler-rt Install llvm-runtimes/libcxx for -stdlib=libc++ Install llvm-runtimes/offload for -fopenmp GPU offloading Install llvm-runtimes/openmp for -fopenmp support Enable compiler-rt sanitizer (-fsanitize*) support Use compiler-rt + libunwind instead of libgcc as the default rtlib for clang Use libc++ instead of libstdc++ as the default stdlib for clang Use lld as the default linker for clang Load Polly plugin (you still need -mllvm -polly to use it) llvm/llvm-project