[3.12] pythongh-117804: Document how to suppress PGO unprofiled sourc…

…e warnings (pythonGH-117859) (python#117912) (cherry picked from commit 757891e) Co-authored-by: Erlend E. Aasland <[email protected]>
methane · Apr 15, 2024 · 556fb36 · 556fb36
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diff --git a/Doc/using/configure.rst b/Doc/using/configure.rst
@@ -302,6 +302,15 @@ also be used to improve performance.
    GCC is used: add ``-fno-semantic-interposition`` to the compiler and linker
    flags.
 
+   .. note::
+
+      During the build, you may encounter compiler warnings about
+      profile data not being available for some source files.
+      These warnings are harmless, as only a subset of the code is exercised
+      during profile data acquisition.
+      To disable these warnings on Clang, manually suppress them by adding
+      ``-Wno-profile-instr-unprofiled`` to :envvar:`CFLAGS`.
+
    .. versionadded:: 3.6
 
    .. versionchanged:: 3.10