In my experience, most Linux compilation still uses gcc. For instance, Fedora often recompiles all of its packages with a newer gcc for new Fedora releases; see

In my experience, most Linux compilation still uses gcc. For instance, Fedora often recompiles all of its packages with a newer gcc for new Fedora releases; see https://fedoraproject.org/wiki/Changes/GCC7 https://fedoraproject.org/wiki/Changes/GCC7 and https://fedoraproject.org/wiki/Changes/GCC6 https://fedoraproject.org/wiki/Changes/GCC6 and so on. And the Linux kernel, due to its heavy use of gcc-specific extensions, also has some problems compiling with LLVM; see https://bugs.llvm.org/show_bug.cgi?id=4068 https://bugs.llvm.org/show_bug.cgi?id=4068 for a list.