[Bug tree-optimization/81489] invalid phi argument used in find_implicit_erroneous_behavior

[vries at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81489

--- Comment #3 from Tom de Vries <vries at gcc dot gnu.org> ---
Created attachment 41797
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=41797&action=edit
Patch with more strict checking in gimple_phi_arg, bootstrapped and reg-tested

This is the patch with which this PR was found.