[Bug tree-optimization/115544] ICE: in lower_complexexpr_stmt, at gimple-lower-bitint.cc:4719 with -O -fno-tree-fre -fno-tree-ccp -fno-tree-forwprop and _BitInt() __builtin_mul_overflow()

[pinskia at gcc dot gnu.org via Gcc-bugs]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115544

--- Comment #3 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Note the gimple stmt/complex_expr in this case:
  _6 = COMPLEX_EXPR <a.0_1, 0>;


where _6 is fully unused.

Complex lowering changes:
  _6 = COMPLEX_EXPR <a.0_1, 0>;
  _2 = REALPART_EXPR <_6>;

into:
  _6 = COMPLEX_EXPR <a.0_1, 0>;
  _2 = a.0_1;

Which is totally correct though it does not do any DCE.
I am not sure if complex lowering should do some simple DCE or if it matters if
it does not do it.