[Bug middle-end/69845] [4.9/5/6 Regression] Expression getting incorrectly optimized after being rewritten by compiler

[rth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69845

--- Comment #7 from Richard Henderson <rth at gcc dot gnu.org> ---
Proposed patch
  https://gcc.gnu.org/ml/gcc-patches/2016-03/msg01255.html