https://gcc.gnu.org/bugzilla/show_bug.cgi?id=98692
--- Comment #12 from Mark Wielaard <mark at gcc dot gnu.org> --- OK, so according to memcheck the load uses a pointer value that isn't initialized properly. And it thinks that value originated from a stack value in the isVariable call. Unfortunately my powerpc assembly is not strong enough to know how to read this precisely, what the calling conventions are and how the address is setup in isVariable.
