We should use MPFR to evaluate the c99 bessel functions. However we have to wait until MPFR implements a suitable interface as described here:
http://gforge.inria.fr/plugins/scmsvn/viewcvs.php/trunk/TODO?root=mpfr&rev=3448&r1=3446&r2=3448 -- Summary: Evaluate bessel functions at compile-time Product: gcc Version: unknown Status: UNCONFIRMED Keywords: missed-optimization Severity: enhancement Priority: P3 Component: middle-end AssignedTo: unassigned at gcc dot gnu dot org ReportedBy: ghazi at gcc dot gnu dot org BugsThisDependsOn: 29335 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=30251