Squashme: result of George+Jeff discussion. This may actually fix the

IBM CI (and I may have unfairly been maligning IBM's CI if it was
showing an actual problem... oops!).

Signed-off-by: Jeff Squyres <[email protected]>

Author: jsquyres

config/opal_config_asm.m4

@@ -131,6 +131,9 @@ dnl Check with:
 dnl 1. No compiler/linker flags.
 dnl 2. CFLAGS += -mcx16
 dnl 3. LIBS += -latomic
+dnl 4. Finally, if it links ok with any of #1, #2, or #3, actually try
+dnl to run the test code (if we're not cross-compiling) and verify
+dnl that it actually gives us the correct result.
 dnl
 dnl Note that we unfortunately can't use AC SEARCH_LIBS because its
 dnl check incorrectly fails (because these functions are special compiler
@@ -186,6 +189,18 @@ AC_DEFUN([OPAL_ASM_CHECK_ATOMIC_FUNC],[
               AC_MSG_RESULT([no])])
          ])
 
+    dnl If we have it, try it and make sure it gives a correct result.
+    dnl As of Aug 2018, we know that it links but does *not* work on clang
+    dnl 6 on ARM64.
+    AS_IF([test $opal_asm_check_func_happy -eq 1],
+        [AC_MSG_CHECKING([if $1 gives correct results])
+         AC_RUN_IFELSE([$2],
+              [AC_MSG_RESULT([yes])],
+              [opal_asm_check_func_happy=0
+               AC_MSG_RESULT([no])],
+              [AC_MSG_RESULT([cannot test -- assume yes (cross compiling)])])
+         ])
+
     AS_IF([test $opal_asm_check_func_happy -eq 1], [$3], [$4])
 
     OPAL_VAR_SCOPE_POP
@@ -204,17 +219,6 @@ AC_DEFUN([OPAL_CHECK_SYNC_BUILTIN_CSWAP_INT128], [
       [sync_bool_compare_and_swap_128_result=1],
       [sync_bool_compare_and_swap_128_result=0])
 
-  # If we have it, try it, and make sure it works.  As of Aug 2018, we
-  # know that it links but does *not* work on clang 6 on ARM64.
-  AS_IF([test $sync_bool_compare_and_swap_128_result -eq 1],
-        [AC_MSG_CHECKING([if __sync_bool_compare_and_swap works])
-         AC_RUN_IFELSE([AC_LANG_SOURCE(OPAL_SYNC_BOOL_COMPARE_AND_SWAP_TEST_SOURCE)],
-              [AC_MSG_RESULT([yes])],
-              [sync_bool_compare_and_swap_128_result=0
-               AC_MSG_RESULT([no])],
-              [AC_MSG_RESULT([cannot test -- assume yes (cross compiling)])])
-         ])
-
   AC_DEFINE_UNQUOTED([OPAL_HAVE_SYNC_BUILTIN_CSWAP_INT128],
         [$sync_bool_compare_and_swap_128_result],
         [Whether the __sync builtin atomic compare and swap supports 128-bit values])
@@ -267,17 +271,6 @@ AC_DEFUN([OPAL_CHECK_GCC_BUILTIN_CSWAP_INT128], [
       [atomic_compare_exchange_n_128_result=1],
       [atomic_compare_exchange_n_128_result=0])
 
-  # If we have it, try it, and make sure it works.  As of Aug 2018, we
-  # know that it does *not* work on clang 6 on ARM64.
-  AS_IF([test $atomic_compare_exchange_n_128_result -eq 1],
-        [AC_MSG_CHECKING([if __atomic_compare_exchange_n works])
-         AC_RUN_IFELSE([AC_LANG_SOURCE(OPAL_ATOMIC_COMPARE_EXCHANGE_N_TEST_SOURCE)],
-              [AC_MSG_RESULT([yes])],
-              [atomic_compare_exchange_n_128_result=0
-               AC_MSG_RESULT([no])],
-              [AC_MSG_RESULT([cannot test -- assume yes (cross compiling)])])
-         ])
-
   # If we have it and it works, check to make sure it is always lock
   # free.
   AS_IF([test $atomic_compare_exchange_n_128_result -eq 1],