I see that your GCC port uses textual prologues. As it happens, I just
implemented dwarf generation for that mechanism (for Thumb), so I know
how it's supposed to work. Here's your problem. First you have:
/* FIXME: Slightly redundant calculation, as we do the same in
pieces below. This offset must be the total adjustment of the
stack-pointer. We can then def_cfa call at the end of this
function with the current implementation of execute_cfa_insn, but
that wouldn't really be clean. */
cfa_label = dwarf2out_cfi_label ();
dwarf2out_def_cfa (cfa_label, cfa_reg, cfa_offset);
but that label is at the beginning of the function, so this is
incorrect. That's not what the CFA is at the beginning of the
function.