From 7589d713a14a1efbb0cbb7caa9fdbad2b081cf18 Mon Sep 17 00:00:00 2001
From: Gregory Szorc <gregory.szorc@gmail.com>
Date: Tue, 24 Jan 2023 01:34:44 -0800
Subject: [PATCH] gh-101060: conditionally add
 `-fno-reorder-blocks-and-partition` (gh-101061)

---
 ...-01-15-11-22-15.gh-issue-101060.0mYk9E.rst |  3 ++
 configure                                     | 41 ++++++++++++++++++-
 configure.ac                                  |  7 +++-
 3 files changed, 49 insertions(+), 2 deletions(-)
 create mode 100644 Misc/NEWS.d/next/Build/2023-01-15-11-22-15.gh-issue-101060.0mYk9E.rst

diff --git a/Misc/NEWS.d/next/Build/2023-01-15-11-22-15.gh-issue-101060.0mYk9E.rst b/Misc/NEWS.d/next/Build/2023-01-15-11-22-15.gh-issue-101060.0mYk9E.rst
new file mode 100644
index 00000000000000..bebbf8c898d547
--- /dev/null
+++ b/Misc/NEWS.d/next/Build/2023-01-15-11-22-15.gh-issue-101060.0mYk9E.rst
@@ -0,0 +1,3 @@
+Conditionally add ``-fno-reorder-blocks-and-partition`` in configure.
+Effectively fixes ``--enable-bolt`` when using Clang, as this appears to be
+a GCC-only flag.
diff --git a/configure b/configure
index e4ec5c40fd7a36..709913dee8314d 100755
--- a/configure
+++ b/configure
@@ -7914,8 +7914,47 @@ if test "$Py_BOLT" = 'true' ; then
   DEF_MAKE_ALL_RULE="bolt-opt"
   DEF_MAKE_RULE="build_all"
 
+  # -fno-reorder-blocks-and-partition is required for bolt to work.
+  # Possibly GCC only.
+  { $as_echo "$as_me:${as_lineno-$LINENO}: checking whether C compiler accepts -fno-reorder-blocks-and-partition" >&5
+$as_echo_n "checking whether C compiler accepts -fno-reorder-blocks-and-partition... " >&6; }
+if ${ax_cv_check_cflags___fno_reorder_blocks_and_partition+:} false; then :
+  $as_echo_n "(cached) " >&6
+else
+
+  ax_check_save_flags=$CFLAGS
+  CFLAGS="$CFLAGS  -fno-reorder-blocks-and-partition"
+  cat confdefs.h - <<_ACEOF >conftest.$ac_ext
+/* end confdefs.h.  */
+
+int
+main ()
+{
+
+  ;
+  return 0;
+}
+_ACEOF
+if ac_fn_c_try_compile "$LINENO"; then :
+  ax_cv_check_cflags___fno_reorder_blocks_and_partition=yes
+else
+  ax_cv_check_cflags___fno_reorder_blocks_and_partition=no
+fi
+rm -f core conftest.err conftest.$ac_objext conftest.$ac_ext
+  CFLAGS=$ax_check_save_flags
+fi
+{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ax_cv_check_cflags___fno_reorder_blocks_and_partition" >&5
+$as_echo "$ax_cv_check_cflags___fno_reorder_blocks_and_partition" >&6; }
+if test "x$ax_cv_check_cflags___fno_reorder_blocks_and_partition" = xyes; then :
+
+      CFLAGS_NODIST="$CFLAGS_NODIST -fno-reorder-blocks-and-partition"
+
+else
+  :
+fi
+
+
   # These flags are required for bolt to work:
-  CFLAGS_NODIST="$CFLAGS_NODIST -fno-reorder-blocks-and-partition"
   LDFLAGS_NODIST="$LDFLAGS_NODIST -Wl,--emit-relocs"
 
   # These flags are required to get good performance from bolt:
diff --git a/configure.ac b/configure.ac
index 15412054856fe4..12249b2d472900 100644
--- a/configure.ac
+++ b/configure.ac
@@ -1939,8 +1939,13 @@ if test "$Py_BOLT" = 'true' ; then
   DEF_MAKE_ALL_RULE="bolt-opt"
   DEF_MAKE_RULE="build_all"
 
+  # -fno-reorder-blocks-and-partition is required for bolt to work.
+  # Possibly GCC only.
+  AX_CHECK_COMPILE_FLAG([-fno-reorder-blocks-and-partition],[
+      CFLAGS_NODIST="$CFLAGS_NODIST -fno-reorder-blocks-and-partition"
+  ])
+
   # These flags are required for bolt to work:
-  CFLAGS_NODIST="$CFLAGS_NODIST -fno-reorder-blocks-and-partition"
   LDFLAGS_NODIST="$LDFLAGS_NODIST -Wl,--emit-relocs"
 
   # These flags are required to get good performance from bolt: