[Bug tree-optimization/15785] fold misses unary transformation

[pinskia at gcc dot gnu dot org]

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           What    |Removed                     |Added
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OtherBugsDependingO|15458                       |
              nThis|                            |
  BugsThisDependsOn|                            |15458


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=15785