udata_ovr compatibility issue with MPLAB

This is a MPLAB specific issue

The compiler generates a .register section with the
udata_ovr directive, the section is always located to
0x0000

Unfortunately such sections can only be located to a
"DATABANK" - the given example in the SDCC doc which
specifies 0x00-0x7f as "ACCESSBANK" does not work, the
linker returns following error message (example):

Error - section '.registers' can not fit the absolute
section. Section '.registers' start=0x00000000,
length=0x00000008

There are two possible workarounds, but both produce
other problems which are not solvable with the current
MPLAB release 7.11

1) replace "udata_ovr" by "udata_acs" in the generated
.asm file before it is passed to the assembler.
Problem: access sections cannot be overlayed, this
means: it works so long only one C file is compiled and
linked, but it leads to conflicts once multiple C files
are used

2) replace ACCESSBANK by DATABANK in the linker file.
The linker passes now, but it produces instructions in
BANKED mode if the access type is not specified

This can be checked with a disassembler - a "movf
r0x01, W" results to "movf r0x01, W, BANKED"

A proper solution would be a change in SDCC: if ",
ACCESS" is added to all instructions (except for movff,
etc...) which are using overlayed registers, it is
guaranteed that the linker will generate the right
opcodes (I've checked this with a converter script)

SDCC version:
mcs51/gbz80/z80/avr/ds390/pic16/pic14/TININative/xa51/ds400/hc08
2.5.0 #1020 (May 8 2005) (MINGW32)

Thorsten.Klose@gmx.de