+FN_(tryPutMVarzh_fast)
+{
+ StgMVar *mvar;
+ const StgInfoTable *info;
+
+ FB_
+ /* args: R1 = MVar, R2 = value */
+
+ mvar = (StgMVar *)R1.p;
+
+#ifdef SMP
+ info = LOCK_CLOSURE(mvar);
+#else
+ info = GET_INFO(mvar);
+#endif
+
+ if (info == &stg_FULL_MVAR_info) {
+
+#ifdef SMP
+ /* unlock the MVar */
+ mvar->header.info = &stg_FULL_MVAR_info;
+#endif
+
+ RET_N(0);
+ }
+
+ mvar->value = R2.cl;
+
+ /* wake up the first thread on the queue, it will continue with the
+ * takeMVar operation and mark the MVar empty again.
+ */
+ if (mvar->head != (StgTSO *)&stg_END_TSO_QUEUE_closure) {
+ ASSERT(mvar->head->why_blocked == BlockedOnMVar);
+#if defined(GRAN) || defined(PAR)
+ /* ToDo: check 2nd arg (mvar) is right */
+ mvar->head = RET_STGCALL2(StgTSO *,unblockOne,mvar->head,mvar);
+#else
+ mvar->head = RET_STGCALL1(StgTSO *,unblockOne,mvar->head);
+#endif
+ if (mvar->head == (StgTSO *)&stg_END_TSO_QUEUE_closure) {
+ mvar->tail = (StgTSO *)&stg_END_TSO_QUEUE_closure;
+ }
+ }
+
+ /* unlocks the MVar in the SMP case */
+ SET_INFO(mvar,&stg_FULL_MVAR_info);
+
+ /* ToDo: yield here for better communication performance? */
+ RET_N(1);
+ FE_
+}
+