[Bug c++/69892] Missing -Wuninitialized warning

[glisse at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69892

--- Comment #4 from Marc Glisse <glisse at gcc dot gnu.org> ---
The example in comment #3 shows a missed optimization:

  if (valid_3(D) != 0)

could be optimized to if(true) or if(false), whichever is most convenient
(__builtin_unreachable() might also be a possibility).

(the early warning works here because the uninitialized variable is used in a
GIMPLE_COND, not a PHI)