https://gcc.gnu.org/bugzilla/show_bug.cgi?id=103464
--- Comment #4 from Richard Biener <rguenth at gcc dot gnu.org> --- What we should avoid is recursion depths worse than that, but it's quite hard to assess this. I've added some prints to fold_using_range::range_of_phi with >>> entering and <<< exiting the function, printing the PHI address and the >>> basic-block the PHI is in. That results in PHI 0x7ffff6681400 >>> 3 PHI 0x7ffff6681600 >>> 7 PHI 0x7ffff6681800 >>> 10 PHI 0x7ffff6681700 >>> 9 PHI 0x7ffff6681500 >>> 6 PHI 0x7ffff6681d00 >>> 10 PHI 0x7ffff6681c00 >>> 9 PHI 0x7ffff6681a00 >>> 6 PHI 0x7ffff6681900 >>> 3 PHI 0x7ffff66af500 >>> 7 PHI 0x7ffff66af600 >>> 10 PHI 0x7ffff66af900 >>> 9 PHI 0x7ffff66af700 >>> 6 PHI 0x7ffff66afb00 >>> 3 PHI 0x7ffff66afd00 >>> 7 PHI 0x7ffff66aff00 >>> 10 PHI 0x7ffff66afe00 >>> 9 PHI 0x7ffff66afc00 >>> 6 PHI 0x7ffff66af200 >>> 10 PHI 0x7ffff66af100 >>> 9 Segmentation fault (core dumped) which shows that while we never recurse to the same PHI we seem to recursively go between PHIs in a CFG cycle thus the recursion depth is CFG cycle size * "PHI width". It might make sense to simply limit the recursion depth with a --param or to avoid visiting backedges at all.
