setup GCC for new processor EVmicro

["Bernhard Schaffer" <b dot schaffer at evisioninc dot ch>]

hi !

i am currently trying to port gcc to a new micro controller architecture
and trying to understand the concept of gcc

the micro controller is a 16 bit risc architecture with
separate data and program memory.
it has 16 general purpose registers and
3 data pointer registers with the possibility
to index, increment and decrement.

registers:

r1 - r16: 			general purpose registers
ap/sp/fp: 			data pointer registers
64k data memory:


i have the following questions:

a) how should the register classes be defined to get
   the highest performance?

   - where should framepointer/argpointer/stackpointer
     be defined (memory registers or hard registers)

   - where should index register be defined ?


b) i have problems to understand the reloading concept
   for ap/fp and sp.

   - what are the basic functions to control reloading of
     the three pointers (concepts in .md *.h )?

   - how are the data pointers shared between
     ap/fp/sp and index registers

c) i have seen the following error message in my first
   compiler version:

---------------------
   c file:

   void mains()
{
    int *p;
    *p=5;
}
---------------------
   insn:

;; Function mains

(note 2 0 3 "" NOTE_INSN_DELETED)

(note 3 2 4 "" NOTE_INSN_FUNCTION_BEG)

(note 4 3 6 "" NOTE_INSN_DELETED)

(note 6 4 9 0 NOTE_INSN_BLOCK_BEG)

(insn 9 6 11 (set (reg:HI 25)
        (mem/f:HI (plus:HI (reg:HI 21)
                (const_int -2 [0xfffffffe])) 0)) -1 (nil)
    (nil))

(insn 11 9 12 (set (reg:HI 26)
        (const_int 5 [0x5])) -1 (nil)
    (nil))

(insn 12 11 14 (set (mem:HI (reg:HI 25) 0)
        (reg:HI 26)) -1 (nil)
    (nil))

(note 14 12 15 0 NOTE_INSN_BLOCK_END)

(note 15 14 17 "" NOTE_INSN_FUNCTION_END)

(code_label 17 15 0 2 "" [num uses: 0])
-----------------------
  error:

cpp: -lang-c: linker input file unused since linking not done
main_pointer.c: In function `mains':
main_pointer.c:54: fixed or forbidden register 16 (ap) was spilled for class
IND
EX_REGS.
main_pointer.c:54: This may be due to a compiler bug or to impossible asm
main_pointer.c:54: statements or clauses.
main_pointer.c:54: This is the instruction:

(insn 12 11 14 (set (mem:HI (reg:HI 1 r2) 0)
        (reg:HI 2 r3)) 2 {*movhi} (nil)
    (nil))
-------------------------

   reloading of (reg:HI 25) comes to a general purpose
   register r2 which is wrong.
   how can the reloading of (reg:HI 25) be
   controlled to end up in a data pointer ?


thank you very much for your help.

Bernhard Schaffer