Use -ip (Linux*) or /Qip (Windows*) and -ipo (Linux) or /Qipo (Windows) to enable Interprocedural Optimizations (IPO), which allow the compiler to analyze your code to determine where you can benefit from the optimizations listed in the following tables.
Optimization |
Affected Aspect of Program |
---|---|
Inline function expansion |
Calls, jumps, branches and loops |
Interprocedural constant propagation |
Arguments, global variables and return values |
Monitoring module-level static variables |
Further optimizations and loop invariant code |
Dead code elimination |
Code size |
Propagation of function characteristics |
Call deletion and call movement |
Multifile optimization |
Same aspects as -ip (Linux) or /Qip (Windows) but across multiple files |
Optimization |
Affected Aspect of Program |
---|---|
Passing arguments in registers |
Calls and register usage |
Loop-invariant code motion |
Further optimizations and loop invariant code |
Inline function expansion is one of the main optimizations performed by the interprocedural optimizer. For function calls that the compiler believes are frequently executed, the compiler may decide to replace the instructions of the call with code for the function itself.
With -ip (Linux) or /Qip (Windows), the compiler performs inline function expansion for calls to procedures defined within the current source file. However, when you use -ipo (Linux) or /Qipo (Windows) to specify multifile IPO, the compiler performs inline function expansion for calls to procedures defined in separate files.
Caution
The -ip and -ipo (Linux) or /Qip and /Qipo (Windows) options can in some cases significantly increase compile time and code size.
On ItaniumŪ-based systems, the -auto-ilp32 (Linux) or /Qauto-ilp32 (Windows) option specifies interprocedural analysis over the whole program. This optimization allows the compiler to use 32-bit pointers whenever possible as long as the application does not exceed a 32-bit address space. Using the -auto-ilp32 (Linux) or /Qauto-ilp32 (Windows) option on programs that exceed 32-bit address space may cause unpredictable results during program execution.
Because this optimization requires interprocedural analysis over the whole program, you must use this option with the -ipo (Linux) or /Qipo (Windows) option.
Note
On IntelŪ EM64T systems, this option has no effect unless -xP or -axP (Linux) or /QxP or /QaxP (Windows) is also specified.