Using PGO

To use profile-guided optimization, you must compile at least twice. Follow these steps:

1. Instrumented compilation
   Compile using the -Qprof_gen option (-prof_gen on Linux*).
   
   Example: prompt>icl -Qprof_gen test.c

2. Instrumented execution
   Run the application through a representative workload to generate a profile. This step generates a data file with a .dyn suffix.
   
   Example: prompt>test.exe

3. Feedback compilation
   Set the compiler to use the profile information the next time you recompile the application, using the -Qprof_use option (-prof_use on Linux). This step uses the dynamic information (.dyn file) generated in the previous step. Besides the optimization, the compiler produces a pgopti.dpi file. You typically specify the default optimizations (-O2) for phase 1, and specify more advanced optimizations (-Qip or -Qipo) for phase 3.
   
   Example: prompt>icl -Qprof_use test.c