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- .. _pgo:
- ===========================
- Profile Guided Optimization
- ===========================
- :abbr:`PGO (Profile Guided Optimization)` is the process of adding
- probes to a compiled binary, running said binary, then using the
- run-time information to *recompile* the binary to (hopefully) make it
- faster.
- How PGO Builds Work
- ===================
- The supported interface for invoking a PGO build is to evaluate the
- *build* target of client.mk with *MOZ_PGO* defined. e.g.::
- $ make -f client.mk MOZ_PGO=1
- This is equivalent to::
- $ make -f client.mk profiledbuild
- Which is roughly equivalent to:
- #. Perform a build with *MOZ_PROFILE_GENERATE=1* and *MOZ_PGO_INSTRUMENTED=1*
- #. Package with *MOZ_PGO_INSTRUMENTED=1*
- #. Performing a run of the instrumented binaries
- #. $ make maybe_clobber_profiledbuild
- #. Perform a build with *MOZ_PROFILE_USE=1*
- Differences between toolchains
- ==============================
- There are some implementation differences depending on the compiler
- toolchain being used.
- The *maybe_clobber_profiledbuild* step gets its name because of a
- difference. On Windows, this step merely moves some *.pgc* files around.
- Using GCC or Clang, it is equivalent to a *make clean*.
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