[avr-gcc-list] Long prologue/epilogue sequences

[Simon Han]

Hi all,

	Maybe I don't know how to write SIGNAL handler.  Most of my handlers 
have rather long prologue and epilogue.  They push r18 to r27 and r30 
to r31.  On the way out, they pop these 12 registers.  All these 
routines do very minimal things, but they all call other functions at 
the end of SIGNAL handling.

	One thing I don't understand is why all these register pushes.  
Wouldn't it be more efficient to only push the ones that SIGNAL uses?  
It seems to me that when there is function call in SIGNAL handler, 
there will be at least 12 register pushes/pops.  When there is no 
function in SIGNAL handler, the register pushes are like normal 
function calls with "reti".

	Could someone point me the documentation that talks about the reason 
and/or possible solution to this?

Thank you in advance,
Simon