https://gcc.gnu.org/bugzilla/show_bug.cgi?id=43892
--- Comment #23 from Segher Boessenkool <segher at gcc dot gnu.org> --- Do you know what addcc does? PowerPC does not have any instruction that behaves like it at all. So it would have to expand to a big fat sequence of instructions, that then hopefully are optimised to something sane later. Instead, the current code expands to something sane immediately. The problem for this testcase (as for all other similar "manual carry" cases) is that we need to replace the carry in our original patterns with (1 - carry). There is no good way to do that in combine, we would need to combine three insns, the first two of which are a parallel.
