I think that the following may explain why your gcc is producing code that
doesn't work.  The code in ieee_init may be violating strict aliasing rules
and unless code is compiled with -fno-strict-aliasing the results may be
undefined.  See

   http://cellperformance.beyond3d.com/articles/2006/06/understanding-strict-aliasing.html

Apologies in advance if you already know about this and it is not relevant.
They suggest using a union, which although is not technically allowed
seems to work with all major compilers.