Fix expand_atomic_fetch_op wrt unused_result

[Richard Henderson]

Testing on coldfire revealed a double call to library functions for some omp 
atomic calls.  This was due to this function trying to return "target" for 
success for unused_result.  Except that for unused_result, target is null, 
which indicates expansion failure.  Oops.


r~

        * optabs.c (expand_atomic_fetch_op): Always return result.


diff --git a/gcc/optabs.c b/gcc/optabs.c
index 0ce21e9..a1917cc 100644
--- a/gcc/optabs.c
+++ b/gcc/optabs.c
@@ -8068,7 +8068,7 @@ expand_atomic_fetch_op (rtx target, rtx mem, rtx val, 
enum rtx_code code,
        {
          /* If the result isn't used, no need to do compensation code.  */
          if (unused_result)
-           return target;
+           return result;
 
          /* Issue compensation code.  Fetch_after  == fetch_before OP val.
             Fetch_before == after REVERSE_OP val.  */
@@ -8110,9 +8110,7 @@ expand_atomic_fetch_op (rtx target, rtx mem, rtx val, 
enum rtx_code code,
          result = emit_library_call_value (libfunc, NULL, LCT_NORMAL, mode,
                                            2, addr, ptr_mode, val, mode);
 
-         if (unused_result)
-           return target;
-         if (fixup)
+         if (!unused_result && fixup)
            result = expand_simple_binop (mode, code, result, val, target,
                                          true, OPTAB_LIB_WIDEN);
          return result;