Re: [avr-gcc-list] Inline assembler now geenerates an error message

[Bernd Trog]

On Sun, 2 Nov 2003, Ebert, Rolf wrote:

> static inline void
> set_io (unsigned char port, unsigned char value) {

David Gay suggessted in
http://www.avr1.org/pipermail/avr-gcc-list/2003-July/004874.html
this:
set_io (const unsigned char port, const unsigned char value) {  

> avr-inline-pb.c: In function `main':
> avr-inline-pb.c:3: warning: asm operand 1 probably doesn't match constraints
> avr-inline-pb.c:3: error: impossible constraint in `asm'
> avr-inline-pb.c: In function `set_io':
> avr-inline-pb.c:3: warning: asm operand 1 probably doesn't match constraints

When you use 'const' you still get the warnings, but no errors..

> Why don't I simply write my code like this:
>
> #include <avr/io.h>
> ...
>   PORTD = 0xAA;
>
>
> Actually, I still want the Ada front end to get in a reasonable,
> i.e. usable, state.  Ada does not have a prepocessor which is used
> very cleverly in the above statement.

IMO, the clever part is in the gcc-backend/optimzer - not in the
frontend/macros: 

With '-O0'
  PORTD = 0xAA;
compiles to
   ldi     r24, 0xAA       ; 170
   sts     0x0032, r24

So, the goal should be, to feed the frontend with normal Ada code
and let the backend/optimzer do it's job...somehow...






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