SLAU132V October 2004 – February 2020
When optimizing with the --opt_level=3 option (aliased as -O3), the compiler automatically inlines small functions. A command-line option, --auto_inline=size, specifies the size threshold. Any function larger than the size threshold is not automatically inlined. You can use the --auto_inline=size option in the following ways:
The compiler inlines the function only if the result is less than the size parameter. The compiler measures the size of a function in arbitrary units; however, the optimizer information file (created with the --gen_opt_level=1 or --gen_opt_level=2 option) reports the size of each function in the same units that the --auto_inline option uses.
The --auto_inline=size option controls only the inlining of functions that are not explicitly declared as inline. If you do not use the --auto_inline=size option, the compiler inlines very small functions.
For information about interactions between command-line options, pragmas, and keywords that affect inlining, see Section 2.11.
NOTE
Optimization Level 3 and InliningIn order to turn on automatic inlining, you must use the --opt_level=3 option. If you desire the --opt_level=3 optimizations, but not automatic inlining, use --auto_inline=0 with the --opt_level=3 option.
NOTE
Inlining and Code SizeExpanding functions inline increases code size, especially inlining a function that is called in a number of places. Function inlining is optimal for functions that are called only from a small number of places and for small functions. To prevent increases in code size because of inlining, use the --auto_inline=0 option. This option causes the compiler to inline intrinsics only.