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bpo-38980: Add -fno-semantic-interposition when building with optimizations #22862

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Oct 21, 2020
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bpo-38980: Add -fno-semantic-interposition when building with optimizations #22862

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bpo-38980: Add -fno-semantic-interposition when building with optimiz…
pablogsal Oct 21, 2020
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Update Doc/whatsnew/3.10.rst
pablogsal Oct 21, 2020
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8 changes: 8 additions & 0 deletions Doc/whatsnew/3.10.rst
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Original file line number Diff line number Diff line change
Expand Up @@ -256,6 +256,14 @@ Optimizations
It is about 36% faster now. (Contributed by Pablo Galindo and Yury Selivanov
in :issue:`42093`.)

* When building Python with ``--enable-optimizations`` now
``-fno-semantic-interposition`` is added to both the compile and link line.
This speeds builds of the Python interpreter created with ``--enable-shared``
with ``gcc`` by up to 30%. See `this article
<https://developers.redhat.com/blog/2020/06/25/red-hat-enterprise-linux-8-2-brings-faster-python-3-8-run-speeds/>`_
for more details. (Contributed by Victor Stinner and Pablo Galindo in
:issue:`38980`)

Deprecated
==========

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3 changes: 3 additions & 0 deletions Misc/NEWS.d/next/Build/2020-10-21-18-31-54.bpo-38980.xz7BNd.rst
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@@ -0,0 +1,3 @@
Add ``-fno-semantic-interposition`` to both the compile and link line when
building with ``--enable-optimizations``. Patch by Victor Stinner and Pablo
Galindo.
8 changes: 8 additions & 0 deletions configure
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Expand Up @@ -6482,6 +6482,14 @@ if test "$Py_OPT" = 'true' ; then
DEF_MAKE_ALL_RULE="profile-opt"
REQUIRE_PGO="yes"
DEF_MAKE_RULE="build_all"
case $CC in
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There is no conditional activation on --enable-shared because C extensions can also benefit from this (and they inherit the build flags).

*gcc*)
CFLAGS_NODIST="$CFLAGS_NODIST -fno-semantic-interposition"
LDFLAGS_NODIST="$LDFLAGS_NODIST -fno-semantic-interposition"
;;
esac


else
DEF_MAKE_ALL_RULE="build_all"
REQUIRE_PGO="no"
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8 changes: 8 additions & 0 deletions configure.ac
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Expand Up @@ -1318,6 +1318,14 @@ if test "$Py_OPT" = 'true' ; then
DEF_MAKE_ALL_RULE="profile-opt"
REQUIRE_PGO="yes"
DEF_MAKE_RULE="build_all"
case $CC in
*gcc*)
CFLAGS_NODIST="$CFLAGS_NODIST -fno-semantic-interposition"
LDFLAGS_NODIST="$LDFLAGS_NODIST -fno-semantic-interposition"
;;
esac


else
DEF_MAKE_ALL_RULE="build_all"
REQUIRE_PGO="no"
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