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[clang][doc] Simplify Sampling-PGO use example #162588

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Oct 10, 2025
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[clang][doc] Simplify Sampling-PGO use example #162588

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[clang][doc] Simplify Sampling-PGO use example
HaohaiWen Oct 9, 2025
72c3bfb
Fix doc
HaohaiWen Oct 9, 2025
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Address comments
HaohaiWen Oct 10, 2025
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14 changes: 8 additions & 6 deletions clang/docs/UsersManual.rst
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Expand Up @@ -2778,7 +2778,7 @@ usual build cycle when using sample profilers for optimization:

> clang-cl /O2 -gdwarf -gline-tables-only ^
/clang:-fdebug-info-for-profiling /clang:-funique-internal-linkage-names ^
code.cc /Fe:code /fuse-ld=lld /link /debug:dwarf
code.cc /Fe:code -fuse-ld=lld /link /debug:dwarf

.. note::

Expand Down Expand Up @@ -2861,21 +2861,23 @@ usual build cycle when using sample profilers for optimization:
that executes faster than the original one. Note that you are not
required to build the code with the exact same arguments that you
used in the first step. The only requirement is that you build the code
with the same debug info options and ``-fprofile-sample-use``.
with the same debug info options and ``-fprofile-sample-use``. ``-gdwarf``
and ``-gline-tables-only`` can be omitted if you do not need debug info
in the final binary.

On Linux:

.. code-block:: console

$ clang++ -O2 -gline-tables-only \
$ clang++ -O2 \
-fdebug-info-for-profiling -funique-internal-linkage-names \
-fprofile-sample-use=code.prof code.cc -o code

On Windows:

.. code-block:: winbatch

> clang-cl /O2 -gdwarf -gline-tables-only ^
> clang-cl /O2 ^
/clang:-fdebug-info-for-profiling /clang:-funique-internal-linkage-names ^
-fprofile-sample-use=code.prof code.cc /Fe:code -fuse-ld=lld /link /debug:dwarf
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If we don't want DWARF in the binary can we also emit some of the link options like -fuse-ld=lld and /link /debug:dwarf?

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@HaohaiWen HaohaiWen Oct 10, 2025 •
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Good catch.


Expand All @@ -2886,15 +2888,15 @@ usual build cycle when using sample profilers for optimization:

.. code-block:: console

$ clang++ -fsample-profile-use-profi -O2 -gline-tables-only \
$ clang++ -fsample-profile-use-profi -O2 \
-fdebug-info-for-profiling -funique-internal-linkage-names \
-fprofile-sample-use=code.prof code.cc -o code

On Windows:

.. code-block:: winbatch

> clang-cl /clang:-fsample-profile-use-profi /O2 -gdwarf -gline-tables-only ^
> clang-cl /clang:-fsample-profile-use-profi /O2 ^
/clang:-fdebug-info-for-profiling /clang:-funique-internal-linkage-names ^
-fprofile-sample-use=code.prof code.cc /Fe:code -fuse-ld=lld /link /debug:dwarf

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