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comparison: build/docs/pgo.rst
build/docs/pgo.rst
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| 1 .. _pgo: | |
| 2 | |
| 3 =========================== | |
| 4 Profile Guided Optimization | |
| 5 =========================== | |
| 6 | |
| 7 :abbr:`PGO (Profile Guided Optimization)` is the process of adding | |
| 8 probes to a compiled binary, running said binary, then using the | |
| 9 run-time information to *recompile* the binary to (hopefully) make it | |
| 10 faster. | |
| 11 | |
| 12 How PGO Builds Work | |
| 13 =================== | |
| 14 | |
| 15 The supported interface for invoking a PGO build is to evaluate the | |
| 16 *build* target of client.mk with *MOZ_PGO* defined. e.g.:: | |
| 17 | |
| 18 $ make -f client.mk MOZ_PGO=1 | |
| 19 | |
| 20 This is equivalent to:: | |
| 21 | |
| 22 $ make -f client.mk profiledbuild | |
| 23 | |
| 24 Which is roughly equivalent to: | |
| 25 | |
| 26 #. Perform a build with *MOZ_PROFILE_GENERATE=1* and *MOZ_PGO_INSTRUMENTED=1* | |
| 27 #. Package with *MOZ_PGO_INSTRUMENTED=1* | |
| 28 #. Performing a run of the instrumented binaries | |
| 29 #. $ make maybe_clobber_profiledbuild | |
| 30 #. Perform a build with *MOZ_PROFILE_USE=1* | |
| 31 | |
| 32 Differences between toolchains | |
| 33 ============================== | |
| 34 | |
| 35 There are some implementation differences depending on the compiler | |
| 36 toolchain being used. | |
| 37 | |
| 38 The *maybe_clobber_profiledbuild* step gets its name because of a | |
| 39 difference. On Windows, this step merely moves some *.pgc* files around. | |
| 40 Using GCC or Clang, it is equivalent to a *make clean*. |
