writeback

The compiler optimizes object files passed to the linker with object files compiled with -xipo that reside in the archive library (.a) before producing an executable. Any object files contained in the library that were optimized during the compilation are replaced with an optimized version.

For parallel links that use a common set of archive libraries, each link should create its own copy of archive libraries to be optimized before linking. 

readonly

The compiler optimizes object files passed to the linker with object files compiled with -xipo that reside in the archive library (.a) before producing an executable.

The option -xipo_archive=readonly enables cross-module inlining and interprocedural data flow analysis of object files in an archive library specified at link time. However, it does not enable cross-module optimization of the archive library's code except for code that has been inserted into other modules by cross module inlining.

To apply cross-module optimization to code within an archive library, -xipo_archive=writeback is required. Note that doing so modifies the contents of the archive library from which the code was extracted.

none

This is the default. There is no processing of archive files. The compiler does not apply cross-module inlining or other cross-module optimizations to object files compiled using -xipo and extracted from an archive library at link time. To do that, both -xipo and either -xipo_archive=readonly or -xipo_archive=writeback must be specified at link time.