diff options
Diffstat (limited to 'gcc-4.6/gcc/doc/extend.texi')
| -rw-r--r-- | gcc-4.6/gcc/doc/extend.texi | 50 |
1 files changed, 40 insertions, 10 deletions
diff --git a/gcc-4.6/gcc/doc/extend.texi b/gcc-4.6/gcc/doc/extend.texi index c93ec2c..a429584 100644 --- a/gcc-4.6/gcc/doc/extend.texi +++ b/gcc-4.6/gcc/doc/extend.texi @@ -3033,6 +3033,33 @@ compiled with more aggressive optimization options that produce faster and larger code, while other functions can be called with less aggressive options. +@item OS_main/OS_task +@cindex @code{OS_main} AVR function attribute +@cindex @code{OS_task} AVR function attribute +On AVR, functions with the @code{OS_main} or @code{OS_task} attribute +do not save/restore any call-saved register in their prologue/epilogue. + +The @code{OS_main} attribute can be used when there @emph{is +guarantee} that interrupts are disabled at the time when the function +is entered. This will save resources when the stack pointer has to be +changed to set up a frame for local variables. + +The @code{OS_task} attribute can be used when there is @emph{no +guarantee} that interrupts are disabled at that time when the function +is entered like for, e@.g@. task functions in a multi-threading operating +system. In that case, changing the stack pointer register will be +guarded by save/clear/restore of the global interrupt enable flag. + +The differences to the @code{naked} function attrubute are: +@itemize @bullet +@item @code{naked} functions do not have a return instruction whereas +@code{OS_main} and @code{OS_task} functions will have a @code{RET} or +@code{RETI} return instruction. +@item @code{naked} functions do not set up a frame for local variables +or a frame pointer whereas @code{OS_main} and @code{OS_task} do this +as needed. +@end itemize + @item pcs @cindex @code{pcs} function attribute @@ -4521,6 +4548,19 @@ The @code{dllexport} attribute is described in @ref{Function Attributes}. @end table +@subsection AVR Variable Attributes + +@table @code +@item progmem +@cindex @code{progmem} AVR variable attribute +The @code{progmem} attribute is used on the AVR to place data in the program +memory address space (flash). This is accomplished by putting +respective variables into a section whose name starts with @code{.progmem}. + +AVR is a Harvard architecture processor and data and reas only data +normally resides in the data memory address space (RAM). +@end table + @subsection Blackfin Variable Attributes Three attributes are currently defined for the Blackfin. @@ -4790,16 +4830,6 @@ placed in either the @code{.bss_below100} section or the @end table -@subsection AVR Variable Attributes - -@table @code -@item progmem -@cindex @code{progmem} variable attribute -The @code{progmem} attribute is used on the AVR to place data in the Program -Memory address space. The AVR is a Harvard Architecture processor and data -normally resides in the Data Memory address space. -@end table - @node Type Attributes @section Specifying Attributes of Types @cindex attribute of types |