Re: [avr-gcc-list] Compiler error creating ISR prologue?

[Johannes Bauer]

Hi,

On 12.08.2010 19:13, István wrote:

> if I am not deluded by my memory, r1 permanently holds 0. Actually clr
> r1 is redundant.

Not in an ISR. http://www.nongnu.org/avr-libc/user-manual/FAQ.html says 
under "What registers are used by the C compiler?"

r1 - assumed to be always zero in any C code, may be used to remember 
something for a while within one piece of assembler code, but must then 
be cleared after use (clr r1). This includes any use of the [f]mul[s[u]] 
 instructions, which return their result in r1:r0. Interrupt handlers 
save and clear r1 on entry, and restore r1 on exit (in case it was 
non-zero).

Regards,
Johannes