Add misa checks for M, A, F and D extensions and if they are
not present generate illegal instructions. This improves
emulation accurary for harts with a limited set of extensions.
Signed-off-by: Michael Clark <mjc@sifive.com>
Signed-off-by: Alistair Francis <alistair.francis@wdc.com>
Reviewed-by: Richard Henderson <richard.henderson@linaro.org>
Signed-off-by: Palmer Dabbelt <palmer@sifive.com>