Avoid using report_fatal_error, because it will ask the user to file a
bug. If the user attempts to disable SSE on x86_64 and them use floating
point, that's a bug in their code, not a bug in the compiler.
This is just a start. There are other ways to crash the backend in this
configuration, but they should be updated to follow this pattern.
Differential Revision: https://reviews.llvm.org/D27522
llvm-svn: 302835
Reid Kleckner