[gnome-photos] build: Disable rdtscp by default

[Debarshi Ray <debarshir src gnome org>]

commit 6de0cdc15a861a27a936ddcef54be34e5abd68f6
Author: Debarshi Ray <debarshir gnome org>
Date:   Mon Sep 26 18:59:05 2016 +0200

    build: Disable rdtscp by default
    
    ... because it is only available in various Core i[357] CPUs and is
    not portable across all x86_64 versions. It is not prudent to
    automatically enable it during the build because a newer build machine
    will cause the application to crash with a SIGILL when run on
    something older.
    
    This is also a good time to switch to GB_ENABLE_RDTSCP.
    
    Original patch from Christian Hergert for gnome-builder.
    
    https://bugzilla.gnome.org/show_bug.cgi?id=771995

 configure.ac           |   13 +--------
 m4/gb_enable_rdtscp.m4 |   63 ++++++++++++++++++++++++++++++++++++++++++++++++
 2 files changed, 65 insertions(+), 11 deletions(-)
---
diff --git a/configure.ac b/configure.ac
index e24f941..5d55e98 100644
--- a/configure.ac
+++ b/configure.ac
@@ -78,17 +78,8 @@ if test "$have_langinfo_measurement" = "yes"; then
             [Define if _NL_MEASUREMENT_MEASUREMENT is available])
 fi
 
-AC_MSG_CHECKING([for fast counters with rdtscp])
-AC_RUN_IFELSE([AC_LANG_SOURCE([[
-#include <x86intrin.h>
-int main (int argc, char *argv[]) { int cpu; __builtin_ia32_rdtscp (&cpu); return 0; }]])],
-              [have_rdtscp=yes],
-              [have_rdtscp=no])
-              AC_MSG_RESULT([$have_rdtscp])
-              AS_IF([test "$have_rdtscp" = "yes"],
-              [CFLAGS="$CFLAGS -DEGG_HAVE_RDTSCP"])
-
-AS_CASE(["$host"], [*-*-linux*], [CFLAGS="$CFLAGS -D_GNU_SOURCE"], [])
+GB_ENABLE_RDTSCP
+AS_IF([test "x$enable_rdtscp" = "xyes"], [CFLAGS="$CFLAGS -DEGG_HAVE_RDTSCP"])
 AC_CHECK_FUNCS([sched_getcpu])
 
 AC_CHECK_FUNCS([shm_open], [LIBRT=], [AC_CHECK_LIB([rt], [shm_open], [LIBRT=-lrt], [LIBRT=])])
diff --git a/m4/gb_enable_rdtscp.m4 b/m4/gb_enable_rdtscp.m4
new file mode 100644
index 0000000..d646b82
--- /dev/null
+++ b/m4/gb_enable_rdtscp.m4
@@ -0,0 +1,63 @@
+#
+# SYNOPSIS
+#
+#   GB_ENABLE_RDTSCP
+#
+# DESCRIPTION
+#
+#   Enables support for rdtscp counters as supported by egg-counter.
+#
+#   Note: This may or may not override some variables such as CFLAGS.
+#
+# LICENSE
+#
+#   Copyright (c) 2015 Christian Hergert <christian hergert me>
+#
+#   This program is free software: you can redistribute it and/or modify it
+#   under the terms of the GNU General Public License as published by the
+#   Free Software Foundation, either version 3 of the License, or (at your
+#   option) any later version.
+#
+#   This program is distributed in the hope that it will be useful, but
+#   WITHOUT ANY WARRANTY; without even the implied warranty of
+#   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General
+#   Public License for more details.
+#
+#   You should have received a copy of the GNU General Public License along
+#   with this program. If not, see <http://www.gnu.org/licenses/>.
+#
+#   As a special exception, the respective Autoconf Macro's copyright owner
+#   gives unlimited permission to copy, distribute and modify the configure
+#   scripts that are the output of Autoconf when processing the Macro. You
+#   need not follow the terms of the GNU General Public License when using
+#   or distributing such scripts, even though portions of the text of the
+#   Macro appear in them. The GNU General Public License (GPL) does govern
+#   all other use of the material that constitutes the Autoconf Macro.
+#
+#   This special exception to the GPL applies to versions of the Autoconf
+#   Macro released by the Autoconf Archive. When you make and distribute a
+#   modified version of the Autoconf Macro, you may extend this special
+#   exception to the GPL to apply to your modified version as well.
+
+#serial 1
+
+AC_DEFUN([GB_ENABLE_RDTSCP], [
+       AC_ARG_ENABLE([rdtscp], [AC_HELP_STRING([--enable-rdtscp], [turn on rdtscp optimizations 
[default=no]])],
+                                 [enable_rdtscp=$enableval], [enable_rdtscp=no])
+
+       AS_IF([test "$enable_rdtscp" = "yes"], [
+               AC_MSG_CHECKING([for fast counters with rdtscp])
+               AC_RUN_IFELSE([AC_LANG_SOURCE([[
+#include <x86intrin.h>
+int main (int argc, char *argv[]) { int cpu; __builtin_ia32_rdtscp (&cpu); return 0; }
+]])],
+                             [enable_rdtscp=yes],
+                             [enable_rdtscp=no])
+               AC_MSG_RESULT(["$enable_rdtscp"])
+       ])
+
+       AS_CASE(["$host"],
+               [*-*-linux*],[CFLAGS="$CFLAGS -D_GNU_SOURCE"],
+               [])
+])
+