GCC is not for "legacy projects", it still generally generates slightly better code for general purpose programs on x86/AMD64. As Clang has been catching up to

GCC is not for "legacy projects", it still generally generates slightly better code for general purpose programs on x86/AMD64. As Clang has been catching up to GCC in codegen quality, it has also been getting just as slow, so the old argument that Clang is faster is no longer valid. Both GCC and Clang approach their most intensive tasks in roughly the same way, and get similar performance. Clang tends to have more instrumentation tooling. GCC tends to have more interesting codegen tooling. GCC's profile-guided optimization and link-time optimization is more mature, and so is their OpenMP implementation. OpenMP code compiles better with GCC to this day. LLVM itself, on the other hand, has many benefits. It has been around longer than GCC's standalone codegen library, and the API is quite good. There are more mature GPU ISA backends in LLVM as well, though GCC supports more exotic general purpose chips and microcontrollers. This works out better right now because companies have an easier time statically linking the (more permissively licensed) LLVM libs than the GCC ones, and so investing in these backends makes more sense for GPU vendors.