[PATCH] Change configure to look for libpfm4 function first; then fallback to libpfm3

[Maynard J. <may...@us...>]

Change configure to look for libpfm4 function first; then fallback to libpfm3

This change only affects ppc64 architecture, since it's the only
architecture that uses libpfm to obtain the event hex code to pass
to perf_event_open.

This patch has been committed already, but as usual, review comments are
still welcome.

There were bugs in libpfm3 pertaining to POWER7 event definitions that
have been fixed in libpfm4.  So it's likely that some IBM POWER7 users
may want to install libpfm4 and build oprofile to link with it.  For
example, if libpfm4 were installed in /usr/local, the user would invoke
oprofile's configure thusly:

LDFLAGS="-L/usr/local/lib64" CPPFLAGS="-I/usr/local/include" ./configure

But if the user happens to also have libpfm3 already installed in /usr,
then the current order of config tests would result in choosing the libpfm3
library. This logic seems wrong.  The configure checking should go from most
recent to older library versions.  This patch changes the order of checking
so the libpfm4 library would be found first.

Signed-off-by: Maynard Johnson <may...@us...>
---
 configure.ac |    4 ++--
 1 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/configure.ac b/configure.ac
index 3078393..a9b1ee4 100644
--- a/configure.ac
+++ b/configure.ac
@@ -160,8 +160,8 @@ if test "$HAVE_PERF_EVENTS" = "1"; then
 	arch="`uname -m`"
 	if test "$arch" = "ppc64" || test "$arch" = "ppc"; then
 		AC_CHECK_HEADER(perfmon/pfmlib.h,,[AC_MSG_ERROR([pfmlib.h not found; usually provided in papi devel package])])
-		AC_CHECK_LIB(pfm,pfm_get_event_name, HAVE_LIBPFM3='1'; HAVE_LIBPFM='1', [
-			AC_CHECK_LIB(pfm,pfm_get_os_event_encoding, HAVE_LIBPFM3='0'; HAVE_LIBPFM='1',
+		AC_CHECK_LIB(pfm,pfm_get_os_event_encoding, HAVE_LIBPFM3='0'; HAVE_LIBPFM='1', [
+			AC_CHECK_LIB(pfm, pfm_get_event_name, HAVE_LIBPFM3='1'; HAVE_LIBPFM='1',
 			[AC_MSG_ERROR([libpfm not found; usually provided in papi devel package])])])
 		PFM_LIB="-lpfm"
 		AC_DEFINE_UNQUOTED(HAVE_LIBPFM3, $HAVE_LIBPFM3, [Define to 1 if using libpfm3; 0 if using newer libpfm])
-- 
1.7.1