https://gcc.gnu.org/bugzilla/show_bug.cgi?id=87315
--- Comment #1 from Marc Glisse <glisse at gcc dot gnu.org> --- There could be 2 steps: - replace the read with an undefined value (SSA_NAME with GIMPLE_NOP defining statement). I vaguely remember someone was not enthusiastic about it, but I don't remember why. - fold a comparison (other operations as well?) with an undefined value. Arguably, gcc could pick any value for the result (whichever kills more code?). It does seem reasonable to pick false for == and true for !=, though for < or > it is less clear, and if someone does the equivalent of p==p where p is undefined, it can be surprising. This is likely to remove a number of uninitialized warnings.
