[Bug middle-end/20434] pessimization of complex expression

["Thomas dot Koenig at online dot de" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From Thomas dot Koenig at online dot de  2005-03-12 09:45 -------
(In reply to comment #4)
> (In reply to comment #3)
> > > > - Why the casts to double?
> > > Because that is required by the C standard.
> > 
> > Isn't that covered by the as-if rule?  I'm fairly
> > sure the cast to double won't change the result of
> > the "<" operator :-)

> No but the addition is done in double.

Again, the as-if rule:  If a and b are floats, the expression
a+b < 0 should be the same for any a and b regardless wether they
are done in float or double.

The same is true, for float a,b and c, of

c = a+b;

It is _not_ true for exmperssions like c = a+b-a, of course.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20434