[avr-gcc-list] Reenabling interrupts in epilogue of interrupt function

[Christian Troedhandl]

If the following code is compiled with
'avr-gcc -O0 -mmcu=atmega103 -S test.c' (I use version 3.2.0 (20020708)
----------------------------------------
#include <io.h>

extern void bar(int *i);
void foo() __attribute__ ((interrupt));

void foo()
{
  int i;

  bar(&i);
}
---------------------------------------
the following epilogue is generated for function foo():

/* epilogue: frame size=2 */
        adiw r28,2
        cli
        out __SP_H__,r29
        out __SP_L__,r28
        pop r29
[some pop's deleted]
        pop r18
        pop __tmp_reg__
        out __SREG__,__tmp_reg__
        pop __tmp_reg__
        out __SREG__,__tmp_reg__
        pop __tmp_reg__
        pop __zero_reg__
        reti

The problem with this is, that the interrupt is not reenabled after
updating the stack pointer, and so interrupts are blocked for 41
clock ticks, which is not acceptable for our purposes.

Is there a possibility to tell the compiler to insert a 'sei'
instruction after the 'out __SP_H__,r29' instruction, like it is done in
the prologue of the function?

Thanks,
Christian

---------------------------------------------------------------------
Christian Troedhandl                   mailto:address@hidden
Real-Time Systems Group                     voice:+43 (1) 58801-18224
Vienna University of Technology
A-1040 Wien, Treitlstr. 3/182-1        http://www.vmars.tuwien.ac.at/


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