* AVR Options:: Options
* AVR Syntax:: Syntax
* AVR Opcodes:: Opcodes
+* AVR Pseudo Instructions:: Pseudo Instructions
@end menu
@node AVR Options
relocations when it can, and may be able to better compress some debug
information.
+@cindex @code{-mgcc-isr} command line option, AVR
+@item -mgcc-isr
+Enable the @code{__gcc_isr} pseudo instruction.
+
@end table
1001010100011001 eicall
1001010000011001 eijmp
@end smallexample
+
+@node AVR Pseudo Instructions
+@section Pseudo Instructions
+
+The only available pseudo-instruction @code{__gcc_isr} can be activated by
+option @option{-mgcc-isr}.
+
+@table @code
+
+@item __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 @code{tmp_reg}, push of @code{SREG},
+push and clear of @code{zero_reg}, push of @var{Reg}.
+
+@item __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 @var{Reg}, pop of @code{zero_reg},
+pop of @code{SREG}, pop of @code{tmp_reg}.
+
+@item __gcc_isr 0, @var{Reg}
+Finish avr-gcc ISR function. Scan code since the last prologue
+for usage of: @code{SREG}, @code{tmp_reg}, @code{zero_reg}.
+Prologue chunk and epilogue chunks will be replaced by appropriate code
+to save / restore @code{SREG}, @code{tmp_reg}, @code{zero_reg} and @var{Reg}.
+
+@end table
+
+Example input:
+
+@example
+__vector1:
+ __gcc_isr 1
+ lds r24, var
+ inc r24
+ sts var, r24
+ __gcc_isr 2
+ reti
+ __gcc_isr 0, r24
+@end example
+
+Example output:
+
+@example
+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
+@end example