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