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Revert "gh-130048: Reintroduce full LTO as default on Clang (GH-130049)" #130088

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Merged
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Feb 13, 2025
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Revert "gh-130048: Reintroduce full LTO as default on Clang (GH-130049)" #130088

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3 changes: 0 additions & 3 deletions Doc/using/configure.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -575,9 +575,6 @@ also be used to improve performance.
.. versionchanged:: 3.12
Use ThinLTO as the default optimization policy on Clang if the compiler accepts the flag.

.. versionchanged:: next
Revert to using full LTO as the default optimization policy on Clang.

.. option:: --enable-bolt

Enable usage of the `BOLT post-link binary optimizer
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4 changes: 0 additions & 4 deletions Doc/whatsnew/3.14.rst
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Expand Up @@ -1279,10 +1279,6 @@ Build changes
* GNU Autoconf 2.72 is now required to generate :file:`configure`.
(Contributed by Erlend Aasland in :gh:`115765`.)

* CPython now uses Full LTO as the default link time optimization policy
on Clang. This reverts an earlier change in CPython 3.12.
(Contributed by Ken Jin in :gh:`130049`.)

.. _whatsnew314-pep761:

PEP 761: Discontinuation of PGP signatures
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1 change: 0 additions & 1 deletion Misc/NEWS.d/next/Build/2025-02-12-19-51-19.gh-issue-130048.kHNkzP.rst
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94 changes: 91 additions & 3 deletions configure
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14 changes: 11 additions & 3 deletions configure.ac
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Expand Up @@ -1986,8 +1986,15 @@ if test "$Py_LTO" = 'true' ; then
# Any changes made here should be reflected in the GCC+Darwin case below
if test $Py_LTO_POLICY = default
then
LTOFLAGS="-flto -Wl,-export_dynamic -Wl,-object_path_lto,\"\$@\".lto"
LTOCFLAGS="-flto"
# Check that ThinLTO is accepted.
AX_CHECK_COMPILE_FLAG([-flto=thin],[
LTOFLAGS="-flto=thin -Wl,-export_dynamic -Wl,-object_path_lto,\"\$@\".lto"
LTOCFLAGS="-flto=thin"
],[
LTOFLAGS="-flto -Wl,-export_dynamic -Wl,-object_path_lto,\"\$@\".lto"
LTOCFLAGS="-flto"
]
)
else
LTOFLAGS="-flto=${Py_LTO_POLICY} -Wl,-export_dynamic -Wl,-object_path_lto,\"\$@\".lto"
LTOCFLAGS="-flto=${Py_LTO_POLICY}"
Expand All @@ -1996,7 +2003,8 @@ if test "$Py_LTO" = 'true' ; then
*)
if test $Py_LTO_POLICY = default
then
LTOFLAGS="-flto"
# Check that ThinLTO is accepted
AX_CHECK_COMPILE_FLAG([-flto=thin],[LTOFLAGS="-flto=thin"],[LTOFLAGS="-flto"])
else
LTOFLAGS="-flto=${Py_LTO_POLICY}"
fi
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