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[Bug fortran/25620] Missed optimization with power
- From: "jv244 at cam dot ac dot uk" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 13 Jan 2006 17:33:39 -0000
- Subject: [Bug fortran/25620] Missed optimization with power
- References: <bug-25620-6642@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #4 from jv244 at cam dot ac dot uk 2006-01-13 17:33 -------
(In reply to comment #3)
> This needs to be done by the frontend, as the folded 2/3 or 4/3 is not exactly
> representable in the target FP format (and such cannot be checked for). Making
> this a frontend bug, rather than just closing as WONTFIX ;)
Without fully understanding the above in all details.
some target FP format might still have that 2./3. == 2 * 1./3. ?
Furthermore, I would think that under -ffast-math these kind of transformations
should be allowed if these equalities hold 'at machine precision'. E.g.
x**p is replaced by cuberoot(p) if p is the FP number that is closest to 1./3.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=25620