https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81633
--- Comment #5 from Jakub Jelinek <jakub at gcc dot gnu.org> --- To answer myself, child_index doesn't need to be equal to i, e.g. if some operand is constant in all the statements, then there is no SLP child for it. If there are no NULL oprnd, then we can as well just start from one above the previous child_index, what we before this change. The question for NULL oprnd is whether the omitted operand will always be a SSA_NAME which always has (or always does not have) a corresponding SLP_TREE_CHILDREN child node. If it is not unconditional, then perhaps we need to say add an index integer into struct _slp_tree and use those numbers to find the slp child or lack thereof based on the position of the argument, not its value.
