[Bug middle-end/78174] out of bounds array subscript in rtl.h NOTE_DATA macro

[msebor at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78174

--- Comment #4 from Martin Sebor <msebor at gcc dot gnu.org> ---
Yes, rtx_note derives from rtx_insn which derives from rtx_def which is where
the union containing the one-element fld array is defined.