c++ provides a standard way to retrieve the value of nan. Use that instead of a function to compute it, or macros defined for c. Change-Id: I483e8642d28cc3187682ce6bb7457b5e796cf61c Reviewed-on: https://gem5-review.googlesource.com/c/public/gem5/+/45366 Reviewed-by: Daniel Carvalho <odanrc@yahoo.com.br> Maintainer: Gabe Black <gabe.black@gmail.com> Tested-by: kokoro <noreply+kokoro@google.com>