[Bug tree-optimization/81948] vectorize exp2 using exp

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81948

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2017-08-24
             Blocks|                            |53947
     Ever confirmed|0                           |1

--- Comment #1 from Richard Biener <rguenth at gcc dot gnu.org> ---
Confirmed.  glibc uses a different alg for exp2 than exp but for exp10 it
simply does exp(x * log(10)) it seems.

Probably requires some refactoring in vectorizable_simd_clone_call.

Or we decide that with -funsafe-math-optimizations canonicalizing expN/logN
to exp/log is worthwhile.

The best thing would be to enhance glibc of course.


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=53947
[Bug 53947] [meta-bug] vectorizer missed-optimizations