[Bug tree-optimization/66946] Spurious uninitialized warning

[wdijkstr at arm dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=66946

--- Comment #4 from Wilco <wdijkstr at arm dot com> ---
(In reply to Andrew Pinski from comment #2)
> Comment on attachment 36021 [details]
> minimal example
> 
> written == ((wchar_t) 0xfffd)
> 
> Will ever be true or is there some sign extending going on which causes this
> to be false for the default case?

The issue seems related to signextension indeed. My GCC builds include this
patch: https://gcc.gnu.org/ml/gcc-patches/2015-05/msg00005.html

When I disable this new phase the warning disappears, so it might be due to a
transformation it makes. The generated code is virtually identical, just
different register allocation.