That "not everyone has a retpoline compiler yet" was in the context of the Linux kernel, which so far compiles with GCC only (IIRC it also compiled with ICC in

That "not everyone has a retpoline compiler yet" was in the context of the Linux kernel, which so far compiles with GCC only (IIRC it also compiled with ICC in a distant past; and there's an effort to make it possible for LLVM/clang to compile the kernel, which is nearing completion). So in the context of this discussion, he's talking (and thinking) about GCC.