Re: different address spaces

[Paul Schlie <schlie at comcast dot net>]

> Martin Koegler wrote:
> I have redone the implementation of the eeprom attribute in my prototype.
> It is now a cleaner solution, but requires larger changes in the core,
> but the changes in the core should not affect any backend/frontend, if
> it does not uses them (except a missing case in tree_copy_mem_area, which
> will cause an assertion to fail).
> ...
> +void
> +tree_copy_mem_area (tree to, tree from)
> ....

Alternatively might it make sense to utilize the analogy defined in rtl.h?

  /* Copy the attributes that apply to memory locations from RHS to LHS.  */
  #define MEM_COPY_ATTRIBUTES(LHS, RHS)                \
    (MEM_VOLATILE_P (LHS) = MEM_VOLATILE_P (RHS),            \
     MEM_IN_STRUCT_P (LHS) = MEM_IN_STRUCT_P (RHS),        \
     MEM_SCALAR_P (LHS) = MEM_SCALAR_P (RHS),            \
     MEM_NOTRAP_P (LHS) = MEM_NOTRAP_P (RHS),            \
     MEM_READONLY_P (LHS) = MEM_READONLY_P (RHS),            \
     MEM_KEEP_ALIAS_SET_P (LHS) = MEM_KEEP_ALIAS_SET_P (RHS),    \
     MEM_ATTRS (LHS) = MEM_ATTRS (RHS))

As unfortunately GCC already inconsistently maintains and copies attributes
to memory references, it seems that introducing yet another function to do
so will only likely introduce more inconsistency.

Therefore wonder if it may be best to simply define MEM_ATTRS as you have
done, and then consistently utilize MEM_COPY_ATTRIBUTES to properly copy
attributes associated with memory references when new ones as may need to
be constructed (as all effective address optimizations should be doing, as
otherwise the attributes associated with the original reference will be
lost). I.e.:

Instead of: (as occasionally incorrectly done)
 rtx addr1 = copy_to_mode_reg (Pmode, XEXP (operands[1], 0));    // some EA
 emit_move_insn (tmp_reg_rtx, gen_rtx_MEM (QImode, addr1)); // lose attribs
 emit_move_insn (addr1, gen_rtx_PLUS (Pmode, addr1, const1_rtx)); // new EA

Something like this is necessary:

 rtx addr1 = copy_to_mode_reg (Pmode, XEXP (operands[1], 0));    // some EA
 rtx mem_1 = gen_rtx_MEM (QImode, addr1);         // gen mem
 MEM_COPY_ATTRIBUTES (mem_1, operands[1]);        // copy attributes
 emit_move_insn (tmp_reg_rtx, mem_1);             // read value
 emit_move_insn (addr1, gen_rtx_PLUS (Pmode, addr1, const1_rtx)); // new EA