Complex Division Patch (reprise)

[Stephen L Moshier]

> With that change I believe this patch is probably OK
> for inclusion in egcs-1.2.

Please do not use the -ffast-math switch in this change.  Following is
the relevant excerpt from C9X.  The name of the switch in C9X is
"CX_LIMITED_RANGE on-off-switch."  It should not be mixed up with what
fast-math does.  In addition to violating IEEE, the fast-math switch
enables inaccurate trigonometry functions and it performs
transformations that can change the value of an expression.

The source code for some diagnostic tests that show the errors caused
by fast-math can be obtained from this location:
http://www.netlib.org/cephes/c9x-complex.shar



       7.3.4  The CX_LIMITED_RANGE pragma

       Synopsis

       [#1]

               #include <complex.h>
               #pragma STDC CX_LIMITED_RANGE on-off-switch

       Description

       [#2]  The  usual  mathematical formula for complex multiply, |
       divide, and absolute value are problematic because of  their |
       treatment  of  infinities  and because of undue overflow and
       underflow.  The  CX_LIMITED_RANGE  pragma  can  be  used  to
       inform  the  implementation that (where the state is on) the |
       usual  mathematical formulas are acceptable.151)  The pragma
       can occur either outside external declarations or  preceding
       all  explicit  declarations and statements inside a compound
       statement.  When outside external declarations,  the  pragma
       takes    effect    from   its   occurrence   until   another
       CX_LIMITED_RANGE pragma is encountered, or until the end  of
       the translation unit.  When inside a compound statement, the
       pragma  takes  effect  from  its  occurrence  until  another
       CX_LIMITED_RANGE  pragma  is  encountered  (within  a nested
       compound statement),  or  until  the  end  of  the  compound
       statement;  at the end of a compound statement the state for
       the pragma is restored to  its  condition  just  before  the
       compound  statement.   If  this  pragma is used in any other
       context, the behavior is undefined.  The default  state  for
       the pragma is off.