using frame pointer + constant in reg_equiv_constant

[Joern Rennecke]

P.S.:
This is the ChangeLog entry.

Mon Nov 30 15:16:52 1998  J"orn Rennecke <amylaar@cygnus.co.uk>

        * local-alloc.c (function_invariant_p): New function.
        (update_equiv_regs): Use function_invariant_p instead of CONSTANT_P
        to decide if an equivalence should be recorded.
        * reload1.c (reload) Use function_invariant_p instead of CONSTANT_P
        to decide if an equivalence should be recorded.
        Unshare PLUS.
        (calculate_needs_all_insns): Skip insns that only set an equivalence.
        (eliminate_regs): Handle non-constant reg_equiv_constant.
        * rtl.h (function_invariant_p): Declare.