Loop restructuring includes loop interchange, loop fusion, scalar replacement, and elimination of “dead” array assignments. If optimization is not at -xO3 or higher, the compiler raises optimization to -xO3 and issues a warning.
If you do not specify -xdepend, the default is -xdepend=no which means the compiler does not analyze loops for data dependencies. If you specify -xdepend, but do not specify an argument, the compiler sets the option to -xdepend=yes which means the compiler analyzes loops for data dependencies.
Dependency analysis is also included with -xautopar or -xparallel. The dependency analysis is done at compile time.
Dependency analysis may help on single-processor systems. However, if you try -xdepend on single-processor systems, you should not use either -xautopar or -xexplicitpar. If either of them is on, then the -xdepend optimization is done for multiple-processor systems.