9.5.4 Pseudo Instructions

The only available pseudo-instruction __gcc_isr can be activated by option -mgcc-isr.

__gcc_isr 1

Emit code chunk to be used in avr-gcc ISR prologue. It will expand to at most six 1-word instructions, all optional: push of tmp_reg, push of SREG, push and clear of zero_reg, push of Reg.

__gcc_isr 2

Emit code chunk to be used in an avr-gcc ISR epilogue. It will expand to at most five 1-word instructions, all optional: pop of Reg, pop of zero_reg, pop of SREG, pop of tmp_reg.

__gcc_isr 0, Reg

Finish avr-gcc ISR function. Scan code since the last prologue for usage of: SREG, tmp_reg, zero_reg. Prologue chunk and epilogue chunks will be replaced by appropriate code to save / restore SREG, tmp_reg, zero_reg and Reg.

Example input:

     __vector1:
         __gcc_isr 1
         lds r24, var
         inc r24
         sts var, r24
         __gcc_isr 2
         reti
         __gcc_isr 0, r24

Example output:

     00000000 <__vector1>:
        0:   8f 93           push    r24
        2:   8f b7           in      r24, 0x3f
        4:   8f 93           push    r24
        6:   80 91 60 00     lds     r24, 0x0060     ; 0x800060 <var>
        a:   83 95           inc     r24
        c:   80 93 60 00     sts     0x0060, r24     ; 0x800060 <var>
       10:   8f 91           pop     r24
       12:   8f bf           out     0x3f, r24
       14:   8f 91           pop     r24
       16:   18 95           reti