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>ecl -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 and summary file of the performance optimization data with the file name pgopti.dpi.

    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 summary file generated in the previous step. The -Qprof_dir option specifies the directory containing the feedback information from the first step, and is required if the .dyn files are not in the current directory.

    Example: prompt>ecl -Qprof_use test.c