Re: [avr-gcc-list] Using __tmp_reg__ etc in assembly file

[Georg-Johann Lay]

Colin Wall schrieb:
> > gcc gererates a header in easch assembly output that looks like
> >
> >   .file   "fifo.c"
> >   .arch atmega168
> > __SREG__ = 0x3f
> > __SP_H__ = 0x3e
> > __SP_L__ = 0x3d
> > __tmp_reg__ = 0
> > __zero_reg__ = 1
> >   .global __do_copy_data
> >   .global __do_clear_bss
> >  ;  GNU C version 3.4.6 (avr)
> >
> > No, it does not exist in any header. It exists in gcc ;-)
> >
> > Georg-Johann
>
> So, from what I can see, the compiler makes these defines available to
> C source, but not to asm (.S) source, and I need to repeat them myself
> in the asm file to use them there.

No, these defines are not available in a C source. They are available in 
a assembler .s source that is generated by the compiler.
So you can use this in your inline asm.

If you like make you can make the assembler source(s) dependent on a 
dummy header:

.INTERMEDIATE: asm-defines.h dummy.c

%.S: asm-defines.h

dummy.c:
        touch $<

asm-defines.h: dummy.c
        avr-gcc -mmcu=$(MCU_TARGET) -S $< -o $@

and include the generated header in your files

#include "asm-defines.h"

in order to be always in sync with the compiler and the target.

> > You can make use of the constructions (examples):
> >    out  (_SFR_IO_ADDR(SREG)), r25
> >    out  (_SFR_IO_ADDR(SPL)), r26
> >    out  (_SFR_IO_ADDR(SPH)), r27
> > etc, if i remember correctly.
> These work in the asm file because SREG etc are defined when io.h is 
> included. I can't see a way to use __tmp_reg__ et al without re-defining
> them myself.

This is just an asm file head. You cannot use __SREG__ et al. without 
redefining it or letting avr-gcc write a file like described above.

Note that SREG is different from __SREG__:

SREG from libc header expands to the RAM address.
__SREG__ from gcc output is set to the SFR address in I/O space.


Georg-Johann