I can disable the optimization by adding a volatile at the right place in ieee_init. I'll adopt this for a solution since it does not cost in performance.

However, if I compile the following program:

class A
create
  make
feature
  make
    do
       io.put_double (d)
       io.put_new_line
       io.put_double ({REAL_64}.negative_infinity)
       io.put_new_line
    end

   t: REAL_64 = 0.0
end

and then compile it (first it compiles just fine for me), second when executed it prints 0 and -Infinity as expected.

I'm going to send you a runtime with the volatile fix in it and see if it solves the issue or not.