[gnome-builder] build: add GB_ENABLE_RDTSCP

[Christian Hergert <chergert src gnome org>]

commit 7eda84f7f0e140592b202b3f0c9a2994b7a60d67
Author: Christian Hergert <christian hergert me>
Date:   Sun May 17 23:40:20 2015 -0700

    build: add GB_ENABLE_RDTSCP
    
    Previous enable code was not working as expected. This pulls it out int
    a module where we can give it the attention required.
    
    Linux w/o rdtscp requires sched_getcpu(), requiring _GNU_SOURCE.
    
    Using rdtscp is not portable across all x86_64 versions. Distributions
    will likely want to compile with --disable-rdtscp unless they are
    optimizing for varous Core i[357] CPUs.
    
    The default is to disable rdtscp.

 build/autotools/gb_enable_rdtscp.m4 |   63 +++++++++++++++++++++++++++++++++++
 configure.ac                        |   27 ++-------------
 2 files changed, 66 insertions(+), 24 deletions(-)
---
diff --git a/build/autotools/gb_enable_rdtscp.m4 b/build/autotools/gb_enable_rdtscp.m4
new file mode 100644
index 0000000..d646b82
--- /dev/null
+++ b/build/autotools/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="$CFLAGS -D_GNU_SOURCE"],
+               [])
+])
+
diff --git a/configure.ac b/configure.ac
index cb6ba62..d2d9a91 100644
--- a/configure.ac
+++ b/configure.ac
@@ -93,30 +93,9 @@ AC_DEFINE_UNQUOTED([GNU_MAKE_NAME], ["$GMAKE"], [Name of GNU make on this system
 
 
 dnl ***********************************************************************
-dnl Check for Helpful Intrinsics
-dnl ***********************************************************************
-AC_ARG_ENABLE(rdtscp,
-              AS_HELP_STRING([--enable-rdtscp=@<:@no/yes@:>@],
-                             [use rdtscp for fast counters @<:@default=no@:>@]),
-              [
-                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="$CFLAGS -DHAVE_RDTSCP"
-                       enable_rdtscp=yes
-                     ], [enable_rdtscp=no])
-             ],
-              [enable_rdtscp=no])
-AS_IF([test "$enable_rdtscp" = "no"],
-      [AS_CASE(["$host"],
-              [*-*-linux*],[CFLAGS="$CFLAGS -D_GNU_SOURCE"],
-              [])])
+dnl Enable high-performance counters
+dnl ***********************************************************************
+GB_ENABLE_RDTSCP
 
 
 dnl ***********************************************************************