https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61300
--- Comment #7 from Alan Modra <amodra at gmail dot com> --- No, I don't believe there is a convenient way we can look at the REG_PARM_STACK_SPACE argument to determine whether it was used for a call or for a function body. (I did think it might be possible, hence my comment #2, but that was remembering the situation from way back before TYPE_ACTUAL_ARG_TYPES became private to C lang tree nodes.) function.c (function body case) always passes the function decl as the argument. calls.c (call case) sometimes passes a function decl, and sometimes a function type. If calls.c always passed a type it would be easy.. A cursory glance over all target defines of REG_PARM_STACK_SPACE says that it should be possible to change calls.c to do this. Is that a better design change than defining INCOMING_REG_PARM_STACK_SPACE? I don't think so..
