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Re: weird optimization in sin+cos, x86 backend
On 2012-02-03 10:13:58 -0500, Robert Dewar wrote:
> On 2/3/2012 10:01 AM, Michael Matz wrote:
> >No normal math library supports such an extreme range, even basic
> >identities (like cos^2+sin^2=1) aren't retained with such inputs.
>
> I agree: the program is complete nonsense.
I disagree: there may be cases where large inputs can be meaningful.
And it may be important that some identities (like cos^2+sin^2=1) be
preserved.
> It would be useful to know what the intent was.
If the user requested such a computation, there should at least be
some intent. Unless an option like -ffast-math is given, the result
should be accurate.
For the glibc, I've finally reported a bug here:
http://sourceware.org/bugzilla/show_bug.cgi?id=13658
Note that there have been other (somewhat different) complaints in
the past, e.g.
http://sourceware.org/bugzilla/show_bug.cgi?id=13381
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