Fix the detection of 128 bits atomics.

Thanks to Stefan Teleman for identifying this issue and providing a
proof-of-concept patch. It turns out we were missing the check for the
need of -latomic to get support for 128-bits atomics.

Signed-off-by: George Bosilca <bosilca@icl.utk.edu>

Author: bosilca

config/opal_config_asm.m4

@@ -2,7 +2,7 @@ dnl
 dnl Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
 dnl                         University Research and Technology
 dnl                         Corporation.  All rights reserved.
-dnl Copyright (c) 2004-2015 The University of Tennessee and The University
+dnl Copyright (c) 2004-2018 The University of Tennessee and The University
 dnl                         of Tennessee Research Foundation.  All rights
 dnl                         reserved.
 dnl Copyright (c) 2004-2006 High Performance Computing Center Stuttgart,
@@ -27,7 +27,7 @@ dnl
 
 AC_DEFUN([OPAL_CHECK_SYNC_BUILTIN_CSWAP_INT128], [
 
-  OPAL_VAR_SCOPE_PUSH([sync_bool_compare_and_swap_128_result CFLAGS_save])
+  OPAL_VAR_SCOPE_PUSH([sync_bool_compare_and_swap_128_result CFLAGS_save LDFLAGS_save])
 
   AC_ARG_ENABLE([cross-cmpset128],[AC_HELP_STRING([--enable-cross-cmpset128],
                 [enable the use of the __sync builtin atomic compare-and-swap 128 when cross compiling])])
@@ -57,6 +57,22 @@ AC_DEFUN([OPAL_CHECK_SYNC_BUILTIN_CSWAP_INT128], [
 
 	  CFLAGS=$CFLAGS_save
       fi
+
+      if test $sync_bool_compare_and_swap_128_result = 0 ; then
+          LDFLAGS_save=$LDFLAGS
+          LDFLAGS="$LDFLAGS -latomic"
+
+	  AC_MSG_CHECKING([for __sync builtin atomic compare-and-swap on 128-bit values with -latomic])
+	  AC_RUN_IFELSE([AC_LANG_PROGRAM([], [__int128 x = 0; __sync_bool_compare_and_swap (&x, 0, 1);])],
+              [AC_MSG_RESULT([yes])
+		  sync_bool_compare_and_swap_128_result=1
+		  LDFLAGS_save="$LDFLAGS"],
+              [AC_MSG_RESULT([no])],
+	      [AC_MSG_RESULT([no (cross compiling)])])
+
+          LDFLAGS=$LDFLAGS_save
+      fi
+
   else
       AC_MSG_CHECKING([for compiler support of __sync builtin atomic compare-and-swap on 128-bit values])
 
@@ -79,6 +95,21 @@ AC_DEFUN([OPAL_CHECK_SYNC_BUILTIN_CSWAP_INT128], [
 
 	  CFLAGS=$CFLAGS_save
       fi
+
+      if test $sync_bool_compare_and_swap_128_result = 0 ; then
+          LDFLAGS_save=$LDFLAGS
+          LDFLAGS="$LDFLAGS -latomic"
+
+	  AC_MSG_CHECKING([for __sync builtin atomic compare-and-swap on 128-bit values with -latomic])
+	  AC_TRY_LINK([], [__int128 x = 0; __sync_bool_compare_and_swap (&x, 0, 1);],
+              [AC_MSG_RESULT([yes])
+		  sync_bool_compare_and_swap_128_result=1
+		  LDFLAGS_save="$LDFLAGS"],
+              [AC_MSG_RESULT([no])])
+
+          LDFLAGS=$LDFLAGS_save
+      fi
+
   fi
 
   AC_DEFINE_UNQUOTED([OPAL_HAVE_SYNC_BUILTIN_CSWAP_INT128], [$sync_bool_compare_and_swap_128_result],
@@ -120,7 +151,7 @@ __sync_add_and_fetch(&tmp, 1);],
 
 AC_DEFUN([OPAL_CHECK_GCC_BUILTIN_CSWAP_INT128], [
 
-  OPAL_VAR_SCOPE_PUSH([atomic_compare_exchange_n_128_result CFLAGS_save])
+  OPAL_VAR_SCOPE_PUSH([atomic_compare_exchange_n_128_result CFLAGS_save LDFLAGS_save])
 
   AC_ARG_ENABLE([cross-cmpset128],[AC_HELP_STRING([--enable-cross-cmpset128],
                 [enable the use of the __sync builtin atomic compare-and-swap 128 when cross compiling])])
@@ -151,15 +182,35 @@ AC_DEFUN([OPAL_CHECK_GCC_BUILTIN_CSWAP_INT128], [
 	  CFLAGS=$CFLAGS_save
       fi
 
+      if test $atomic_compare_exchange_n_128_result = 0 ; then
+	  LDFLAGS_save=$LDFLAGS
+	  LDFLAGS="$LDFLAGS -latomic"
+
+	  AC_MSG_CHECKING([for __atomic builtin atomic compare-and-swap on 128-bit values with -latomic])
+          AC_RUN_IFELSE([AC_LANG_PROGRAM([], [__int128 x = 0, y = 0; __atomic_compare_exchange_n (&x, &y, 1, 0, __ATOMIC_RELAXED, __ATOMIC_RELAXED);])],
+              [AC_MSG_RESULT([yes])
+		  atomic_compare_exchange_n_128_result=1
+		  LDFLAGS_save="$LDFLAGS"],
+              [AC_MSG_RESULT([no])],
+	      [AC_MSG_RESULT([no (cross compiling)])])
+
+	  LDFLAGS=$LDFLAGS_save
+      fi
+
       if test $atomic_compare_exchange_n_128_result = 1 ; then
-         AC_MSG_CHECKING([if __int128 atomic compare-and-swap is always lock-free])
+          AC_MSG_CHECKING([if __int128 atomic compare-and-swap is always lock-free])
           AC_RUN_IFELSE([AC_LANG_PROGRAM([], [if (!__atomic_always_lock_free(16, 0)) { return 1; }])],
               [AC_MSG_RESULT([yes])],
               [AC_MSG_RESULT([no])
+dnl Because of the variable PUSH/POP scope we need to manually unset these 2 variables
+dnl before going into OPAL_CHECK_SYNC_BUILTIN_CSWAP_INT128
+                 unset CFLAGS_save
+                 unset LDFLAGS_save
                  OPAL_CHECK_SYNC_BUILTIN_CSWAP_INT128
                  atomic_compare_exchange_n_128_result=0],
              [AC_MSG_RESULT([no (cross compiling)])])
       fi
+
   else
       AC_MSG_CHECKING([for compiler support of __atomic builtin atomic compare-and-swap on 128-bit values])
 
@@ -182,6 +233,21 @@ AC_DEFUN([OPAL_CHECK_GCC_BUILTIN_CSWAP_INT128], [
 
 	  CFLAGS=$CFLAGS_save
       fi
+
+      if test $atomic_compare_exchange_n_128_result = 0 ; then
+	  LDFLAGS_save=$LDFLAGS
+	  LDFLAGS="$LDFLAGS -latomic"
+
+	  AC_MSG_CHECKING([for __atomic builtin atomic compare-and-swap on 128-bit values with -latomic])
+          AC_TRY_LINK([], [__int128 x = 0, y = 0; __atomic_compare_exchange_n (&x, &y, 1, 0, __ATOMIC_RELAXED, __ATOMIC_RELAXED);],
+              [AC_MSG_RESULT([yes])
+		  atomic_compare_exchange_n_128_result=1
+		  LDFLAGS_save="$LDFLAGS"],
+              [AC_MSG_RESULT([no])])
+
+	  LDFLAGS=$LDFLAGS_save
+      fi
+
   fi
 
   AC_DEFINE_UNQUOTED([OPAL_HAVE_GCC_BUILTIN_CSWAP_INT128], [$atomic_compare_exchange_n_128_result],

config/opal_functions.m4

@@ -3,7 +3,7 @@ dnl
 dnl Copyright (c) 2004-2005 The Trustees of Indiana University and Indiana
 dnl                         University Research and Technology
 dnl                         Corporation.  All rights reserved.
-dnl Copyright (c) 2004-2005 The University of Tennessee and The University
+dnl Copyright (c) 2004-2018 The University of Tennessee and The University
 dnl                         of Tennessee Research Foundation.  All rights
 dnl                         reserved.
 dnl Copyright (c) 2004-2005 High Performance Computing Center Stuttgart,
@@ -506,7 +506,7 @@ dnl #######################################################################
 dnl #######################################################################
 dnl #######################################################################
 
-# Declare some variables; use OPAL_VAR_SCOPE_END to ensure that they
+# Declare some variables; use OPAL_VAR_SCOPE_POP to ensure that they
 # are cleaned up / undefined.
 AC_DEFUN([OPAL_VAR_SCOPE_PUSH],[
 
@@ -524,7 +524,7 @@ AC_DEFUN([OPAL_VAR_SCOPE_PUSH],[
         eval $opal_str
 
         if test "x$opal_str" != "x"; then
-            AC_MSG_WARN([Found configure shell variable clash!])
+            AC_MSG_WARN([Found configure shell variable clash at line $LINENO!])
             AC_MSG_WARN([[OPAL_VAR_SCOPE_PUSH] called on "$opal_var",])
             AC_MSG_WARN([but it is already defined with value "$opal_str"])
             AC_MSG_WARN([This usually indicates an error in configure.])