Make clang accept -msahf (and -mno-sahf) flags to activate the
+sahf feature for the backend, for bug 36028 (Incorrect use of
pushf/popf enables/disables interrupts on amd64 kernels). This was
originally submitted in bug 36037 by Jonathan Looney
As described there, GCC also uses -msahf for this feature, and the
backend already recognizes the +sahf feature. All that is needed is to
teach clang to pass this on to the backend.
The mapping of feature support onto CPUs may not be complete; rather, it
was chosen to match LLVM's idea of which CPUs support this feature (see
I also updated the affected test case (CodeGen/attr-target-x86.c) to
match the emitted output.