Development Tools

-O

This option specifies the optimization level or the details of each optimization items.

[Specification format]

-O[level]

-O[item[=value][,item[=value]]...]

-	Interpretation when omitted

Only optimization that debugging is not affected is performed (It is the same result as when -Odefault option is specified).

[Detailed description]

-	This option specifies the optimization level or the details of each optimization items.

-	The items that can be specified as level are shown below. An error will occur if any other item is specified.

nothing	Optimization with debugging precedence Regards debugging as important and suppresses all optimization including default optimization.
default	Default Performs optimization that debugging is not affected (optimization of expressions and register allocation, and the like).
size	Optimization with the object size precedence Regards reducing the ROM/RAM capacity as important and performs the maximum optimization that is effective for general programs.
speed	Optimization with the execution speed precedence Regards shortening the execution speed as important and performs the maximum optimization that is effective for general programs.

-	If level and item are omitted, it is assumed that "size" has been specified.

-	The items that can be specified as item and value are shown below. An error will occur if any other item is specified.

Optimization Item (item)	Parameter (value)	Description
unroll	0 to 4294967295 (Integer value)	Loop expansion The loop statements (for, while, and do-while) are expanded. Use value to specify the maximum rate of increase in code size after loop expansion. A value of 0 set as value has the same meaning as a value of 1. If value is omitted, it is assumed that 4 has been specified. If the -Ospeed option is specified, this item is assumed that the -Ounroll=4 option is specified.
inline	0 to 3 (Integer value)	Inline expansion for functions value signifies the level of the expansion. 0: Suppresses all inline expansion including the function for which "#pragma inline" is specified. 1: Performs inline expansion for only a function for which "#pragma inline" is specified. 2: Distinguishes a function that is the target of expansion automatically and expands it. 3: Distinguishes the function that is the target of expansion automatically and expands it, while minimizing the increase in code size. However, if 1 to 3 is specified, the function that is specified by "#pragma inline" may not be expanded according to the content of the function and the status of compilation. If value is omitted, it is assumed that 2 has been specified. This item is valid when the -Osize or -Ospeed option is specified (when the -Osize option is specified, it is assumed that the -Oinline=3 option has been specified. When the -Ospeed option is specified, it is assumed that the -Oinline=2 option has been specified). If any of the -Osize, -Ospeed or -Oinline option is not specified, this item is assumed that the -Oinline=1 option is specified. If the -Onothing option is specified, this item is assumed that the -Oinline=0 option is specified.
inline_size	0 to 65535 (Integer value)	Size for inline expansion Specify the maximum increasing rate (%) of the code size up to which inline expansion is performed. If value is omitted, it is assumed that 100 has been specified. This item is valid when the -Oinline=2 option is specified (including when the -Ospped option is specified).
inline_init [V1.07.00 or later]	on or off	Using immediate value as initializer of auto variables If "on" is specified, auto variables are always initialized by assigning an immediate value. If "off" is specified, the compiler automatically selects to perform initialization by copying a value between memories or assigning an immediate value. If value is omitted, it is assumed that "on" has been specified.
delete_static_func	on or off	Deleting unused static functions If value is omitted, it is assumed that "on" has been specified. This item is valid when the -Onothing option is not specified.
pipeline	on or off	Pipeline optimization If value is omitted, it is assumed that "on" has been specified.
tail_call	on or off	End call optimization When "on" is specified, if there is a function call at the end of a function and certain conditions are met, a function call for that call is converted to an unconditional branch. The lp store/restore code will be removed, reducing the code size. However, some debug functions cannot be used. If value is omitted, it is assumed that "on" has been specified. This item is valid when the -Ospeed or -Osize option is specified.
map	file name	External variable access optimization Base addresses are set in accordance with the external symbol allocation information generated by the linker, and code for accessing external and static variables relative to the base addresses is generated. When symbol "__gp_data" is defined and a value is specified in gp in the code of the startup routine, code for accessing variables relative to gp when possible is generated in accordance with the external symbol allocation information. Specify the external symbol allocation information file generated by the optimizing linker as file name. If file name is omitted, it performs linking once, and then after creating the external symbol allocation information file, repeats the process from compilation to linking.
smap	None	Optimization of access to external variables defined in the compilation unit Base address is set for external and static variables defined in the file to be compiled, and code that accesses these relative to the base address is generated.
align [V2.03.00 or later]	on or off	Optimization by changing the alignment condition The number of generated instructions is decreased, the code size is reduced and the execution speed is increased by changing the variable alignment condition and then combining multiple accesses into one when, for example, accessing contiguous areas in a structure-type variable. As a result of changing the alignment condition, padding data is filled in and the amount of consumption may increase in the data storage area. If value is omitted, it is assumed that on has been specified. This item is valid when the -Osize or -Ospeed option is specified. If the -stuff option is specified at the same time, this item is invalid and the operation is the same as that when "off" is specified.

-	If this option is specified more than once for the same item, the option specified last will be valid.

-	If -Olevel is specified following -Oitem, -Oitem which was specified first will be invalid. Note, however, that -Omap or -Osmap will not be affected by -Olevel.

-	When -Oitem is not specified, the optimization items are interpreted as follows according to the -Olevel setting.

Optimization Item (item)	Optimization Level (level)
Optimization Item (item)	nothing	default	size	speed
unroll	1	1	1	4
inline	0	1	3	2
inline_size	-	-	-	100
inline_init	off	off	off	on
delete_static_func	off	on	on	on
pipeline	off	off	off	on
tail_call	off	off	on	on
map	-	-	-	-
smap	-	-	-	-
align	off	off	onNote	on

Note	If the -misalign option is specified at the same time, "off" is assumed.

This table does not ensure that the optimization result is the same between the case where an optimization level is selected and then each optimization item setting is changed to the value shown for another level in this table and the case where the latter level is specified from the beginning. For example, the code output by specifying "-Ospeed" may not be the same as that output by specifying "-Osize -Ounroll=4 -Oinline=2 -Oinline_size=100 -Opipeline=on".

[Example of use]

-	To perform optimization with the object size precedence, describe as:

>ccrh -Osize -Xcommon=rh850 main.c