https://github.com/python/cpython/commit/aa284232013693103431fb672a0bcabac3d4200b
commit: aa284232013693103431fb672a0bcabac3d4200b
branch: main
author: Ken Jin <[email protected]>
committer: Fidget-Spinner <[email protected]>
date: 2025-02-13T17:27:19Z
summary:
Revert "gh-130048: Reintroduce full LTO as default on Clang (GH-130049)"
(#130088)
This reverts commit 34c06ccc4c6c21935b46302935f3df24b00daa2c.
files:
D Misc/NEWS.d/next/Build/2025-02-12-19-51-19.gh-issue-130048.kHNkzP.rst
M Doc/using/configure.rst
M Doc/whatsnew/3.14.rst
M configure
M configure.ac
diff --git a/Doc/using/configure.rst b/Doc/using/configure.rst
index e7116d55815679..72912cea2f0c28 100644
--- a/Doc/using/configure.rst
+++ b/Doc/using/configure.rst
@@ -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
diff --git a/Doc/whatsnew/3.14.rst b/Doc/whatsnew/3.14.rst
index 8e4b617181fd99..ece5afd4597ab8 100644
--- a/Doc/whatsnew/3.14.rst
+++ b/Doc/whatsnew/3.14.rst
@@ -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
diff --git
a/Misc/NEWS.d/next/Build/2025-02-12-19-51-19.gh-issue-130048.kHNkzP.rst
b/Misc/NEWS.d/next/Build/2025-02-12-19-51-19.gh-issue-130048.kHNkzP.rst
deleted file mode 100644
index 2344325e689f34..00000000000000
--- a/Misc/NEWS.d/next/Build/2025-02-12-19-51-19.gh-issue-130048.kHNkzP.rst
+++ /dev/null
@@ -1 +0,0 @@
-CPython now uses Full LTO as the default link time optimization policy on
Clang. This reverts an earlier change in CPython 3.12.
diff --git a/configure b/configure
index bebc8bc1a34f9b..453b0123ded0a4 100755
--- a/configure
+++ b/configure
@@ -8766,8 +8766,55 @@ printf "%s\n" "$as_me: llvm-ar found via xcrun:
${LLVM_AR}" >&6;}
# Any changes made here should be reflected in the GCC+Darwin case
below
if test $Py_LTO_POLICY = default
then
- LTOFLAGS="-flto -Wl,-export_dynamic
-Wl,-object_path_lto,\"\$@\".lto"
- LTOCFLAGS="-flto"
+ # Check that ThinLTO is accepted.
+ { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether C
compiler accepts -flto=thin" >&5
+printf %s "checking whether C compiler accepts -flto=thin... " >&6; }
+if test ${ax_cv_check_cflags___flto_thin+y}
+then :
+ printf %s "(cached) " >&6
+else case e in #(
+ e)
+ ax_check_save_flags=$CFLAGS
+ CFLAGS="$CFLAGS -flto=thin"
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+
+int
+main (void)
+{
+
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+ ax_cv_check_cflags___flto_thin=yes
+else case e in #(
+ e) ax_cv_check_cflags___flto_thin=no ;;
+esac
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+ CFLAGS=$ax_check_save_flags ;;
+esac
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result:
$ax_cv_check_cflags___flto_thin" >&5
+printf "%s\n" "$ax_cv_check_cflags___flto_thin" >&6; }
+if test "x$ax_cv_check_cflags___flto_thin" = xyes
+then :
+
+ LTOFLAGS="-flto=thin -Wl,-export_dynamic
-Wl,-object_path_lto,\"\$@\".lto"
+ LTOCFLAGS="-flto=thin"
+
+else case e in #(
+ e)
+ LTOFLAGS="-flto -Wl,-export_dynamic
-Wl,-object_path_lto,\"\$@\".lto"
+ LTOCFLAGS="-flto"
+
+ ;;
+esac
+fi
+
else
LTOFLAGS="-flto=${Py_LTO_POLICY} -Wl,-export_dynamic
-Wl,-object_path_lto,\"\$@\".lto"
LTOCFLAGS="-flto=${Py_LTO_POLICY}"
@@ -8776,7 +8823,48 @@ printf "%s\n" "$as_me: llvm-ar found via xcrun:
${LLVM_AR}" >&6;}
*)
if test $Py_LTO_POLICY = default
then
- LTOFLAGS="-flto"
+ # Check that ThinLTO is accepted
+ { printf "%s\n" "$as_me:${as_lineno-$LINENO}: checking whether C
compiler accepts -flto=thin" >&5
+printf %s "checking whether C compiler accepts -flto=thin... " >&6; }
+if test ${ax_cv_check_cflags___flto_thin+y}
+then :
+ printf %s "(cached) " >&6
+else case e in #(
+ e)
+ ax_check_save_flags=$CFLAGS
+ CFLAGS="$CFLAGS -flto=thin"
+ cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h. */
+
+int
+main (void)
+{
+
+ ;
+ return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"
+then :
+ ax_cv_check_cflags___flto_thin=yes
+else case e in #(
+ e) ax_cv_check_cflags___flto_thin=no ;;
+esac
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.beam conftest.$ac_ext
+ CFLAGS=$ax_check_save_flags ;;
+esac
+fi
+{ printf "%s\n" "$as_me:${as_lineno-$LINENO}: result:
$ax_cv_check_cflags___flto_thin" >&5
+printf "%s\n" "$ax_cv_check_cflags___flto_thin" >&6; }
+if test "x$ax_cv_check_cflags___flto_thin" = xyes
+then :
+ LTOFLAGS="-flto=thin"
+else case e in #(
+ e) LTOFLAGS="-flto" ;;
+esac
+fi
+
else
LTOFLAGS="-flto=${Py_LTO_POLICY}"
fi
diff --git a/configure.ac b/configure.ac
index e1e335a4d4b2a1..234ae90616af62 100644
--- a/configure.ac
+++ b/configure.ac
@@ -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=${Py_LTO_POLICY}"
@@ -1996,7 +2003,8 @@ if test "$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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