With large programs, compilation time in the use phase can improve significantly because the intermediate data is saved. Note that the saved data could increase disk space requirements considerably.
When you use -xprofile_ircache[=path], path overrides the location where the cached files are saved. By default, these files are saved in the same directory as the object file. Specifying a path is useful when the collect and use phases happen in two different directories. Here’s a typical sequence of commands:
example% cc -xO5 -xprofile=collect -xprofile_ircache t1.c t2.c example% a.out // run collects feedback data example% cc -xO5 -xprofile=use -xprofile_ircache t1.c t2.c