A.2.122 -xF[=v[,v...]]

Enables optimal reordering of functions and variables by the linker.

This option instructs the compiler to place functions and/or data variables into separate section fragments, which enables the linker, using directions in a mapfile specified by the linker’s -M option, to reorder these sections to optimize program performance. Generally, this optimization is only effective when page fault time constitutes a significant fraction of program run time.

Reording of variables can help solve the following problems which negatively impact run-time performance:

• Cache and page contention caused by unrelated variables that are near each other in memory.

• Unnecessarily large work-set size as a result of related variables which are not near each other in memory.

• Unnecessarily large work-set size as a result of unused copies of weak variables that decrease the effective data density.

Reordering variables and functions for optimal performance requires the following operations:

1. Compiling and linking with -xF.

2. Following the instructions in the “Program Performance Analysis Tools” manual regarding how to generate a mapfile for functions or following the instructions in the “Linker and Libraries Guide” regarding how to generate a mapfile for data.

3. Relinking with the new mapfile by using the linker’s -M option.

4. Re-executing under the Analyzer to verify improvement.

A.2.122.1 Values

v can be one or more of the following:

Defaults

If you do not specify -xF, the default is -xF=%none. If you specify -xF without any arguments, the default is -xF=%none,func.

Interactions

Using -xF=lcldata inhibits some address calculation optimizations, so you should only use this flag when it is experimentally justified.

See also

analyzer(1), debugger(1), ld(1) man pages