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

Author: pablogsal

Doc/whatsnew/3.10.rst

@@ -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
 ==========
 

Misc/NEWS.d/next/Build/2020-10-21-18-31-54.bpo-38980.xz7BNd.rst

@@ -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.

configure

@@ -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 $CC in
+    *gcc*)
+      CFLAGS_NODIST="$CFLAGS_NODIST -fno-semantic-interposition"
+      LDFLAGS_NODIST="$LDFLAGS_NODIST -fno-semantic-interposition"
+      ;;
+  esac
+
+
 else
   DEF_MAKE_ALL_RULE="build_all"
   REQUIRE_PGO="no"

configure.ac

@@ -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"