Index: doc/extend.texi
===================================================================
--- doc/extend.texi	(Revision 172046)
+++ doc/extend.texi	(Arbeitskopie)
@@ -7924,6 +7924,7 @@ instructions, but allow the compiler to
 * Alpha Built-in Functions::
 * ARM iWMMXt Built-in Functions::
 * ARM NEON Intrinsics::
+* AVR Built-in Functions::
 * Blackfin Built-in Functions::
 * FR-V Built-in Functions::
 * X86 Built-in Functions::
@@ -8175,6 +8176,44 @@ when the @option{-mfpu=neon} switch is u
 
 @include arm-neon-intrinsics.texi
 
+@node AVR Built-in Functions
+@subsection AVR Built-in Functions
+
+For each built-in function for AVR, there is an equally named,
+uppercase built-in macro defined. That way users can easily query if
+or if not a specific built-in is implemented or not. For example, if
+@code{__builtin_avr_nop} is available the macro
+@code{__BUILTIN_AVR_NOP} is defined to @code{1} and undefined otherwise.
+
+The following built-in functions map to the respective machine
+instruction, i.e. @code{nop}, @code{sei}, @code{cli}, @code{sleep},
+@code{wdr}, @code{swap}, @code{fmul}, @code{fmuls}
+resp. @code{fmulsu}. The latter three are only available if the AVR
+device actually supports multiplication.
+
+@smallexample
+void __builtin_avr_nop (void)
+void __builtin_avr_sei (void)
+void __builtin_avr_cli (void)
+void __builtin_avr_sleep (void)
+void __builtin_avr_wdr (void)
+unsigned char __builtin_avr_swap (unsigned char)
+unsigned int __builtin_avr_fmul (unsigned char, unsigned char)
+int __builtin_avr_fmuls (char, char)
+int __builtin_avr_fmulsu (char, unsigned char)
+@end smallexample
+
+In order to delay execution for a specific number of cycles, GCC
+implements
+@smallexample
+void __builtin_avr_delay_cycles (unsigned long ticks)
+@end smallexample
+
+@code{ticks} is the number of ticks to delay execution. Note that this
+built-in does not take into account the effect of interrupts which
+might increase delay time. @code{ticks} must be a compile time
+integer constant; delays with a variable number of cycles are not supported.
+
 @node Blackfin Built-in Functions
 @subsection Blackfin Built-in Functions