(FP_REGNUM): define in terms of SP_REGNUM
rather than by absolute number. Also clearly comment that this
is a convenient lie in order to decrease future confusion.
(ACTUAL_FP_REGNUM): new macro for FP.
(FRAME_CHAIN_VALID): removed. Standard default works fine.
* m88k-tdep.c (frame_chain_valid): redundant, so removed.
(NEXT_PROLOGUE_INSN): removed unused fourth arg, fixed all
callers.
(read_next_frame_reg): declare static.
(examine_prologue): removed unused variabel insn2, rename insn1
to insn, rewrote comment about finding fp, sp, etc. set frame_fp
based on ACTUAL_FP_REGNUM rather than FP_REGNUM which is
actually a scammed alias for SP_REGNUM on m88k.