Make a pass at implementing cbAtEndOfSimTime.

In Icarus Verilog, AtEndOfSimTime is practically the same as
cbReadWriteSync, since the latter is after non-blocking events
in Icarus Verilog.

vpi_user.h

@@ -495,6 +495,7 @@ typedef struct t_cb_data {
 #define cbExitInteractive   22
 #define cbInteractiveScopeChange 23
 #define cbUnresolvedSystf   24
+#define cbAtEndOfSimTime    31
 
 extern vpiHandle vpi_register_cb(p_cb_data data);
 extern PLI_INT32 vpi_remove_cb(vpiHandle ref);

vvp/schedule.cc

@@ -1029,6 +1029,20 @@ void schedule_at_start_of_simtime(vvp_gen_event_t obj, vvp_time64_t delay)
       schedule_event_(cur, delay, SEQ_START);
 }
 
+/*
+ * In the vvp runtime of Icarus Verilog, the SEQ_RWSYNC time step is
+ * after all of the non-blocking assignments, so is effectively the
+ * same as the ReadWriteSync time.
+ */
+void schedule_at_end_of_simtime(vvp_gen_event_t obj, vvp_time64_t delay)
+{
+      struct generic_event_s*cur = new generic_event_s;
+
+      cur->obj = obj;
+      cur->delete_obj_when_done = false;
+      schedule_event_(cur, delay, SEQ_RWSYNC);
+}
+
 static vvp_time64_t schedule_time;
 vvp_time64_t schedule_simtime(void)
 { return schedule_time; }

vvp/schedule.h

@@ -148,6 +148,7 @@ extern void schedule_generic(vvp_gen_event_t obj, vvp_time64_t delay,
 extern void schedule_functor(vvp_gen_event_t obj);
 
 extern void schedule_at_start_of_simtime(vvp_gen_event_t obj, vvp_time64_t delay);
+extern void schedule_at_end_of_simtime(vvp_gen_event_t obj, vvp_time64_t delay);
 
 /* Use this is schedule thread deletion (after rosync). */
 extern void schedule_del_thr(vthread_t thr);

vvp/vpi_callback.cc

@@ -357,7 +357,7 @@ static sync_callback* make_sync(p_cb_data data, bool readonly_flag)
       return obj;
 }
 
-static struct __vpiCallback* make_afterdelay(p_cb_data data, bool simtime_flag)
+static struct __vpiCallback* make_afterdelay(p_cb_data data)
 {
       sync_callback*obj = new sync_callback(data);
       struct sync_cb*cb = new sync_cb;
@@ -378,21 +378,78 @@ static struct __vpiCallback* make_afterdelay(p_cb_data data, bool simtime_flag)
 	    break;
       }
 
-      if (simtime_flag) {
-	    vvp_time64_t cur = schedule_simtime();
-	    if (cur > tv) {
-		  tv = 0;
-		  assert(0);
-	    } else if (cur == tv) {
-		  tv = 0;
-	    } else {
-		  tv -= cur;
-	    }
-	    schedule_at_start_of_simtime(cb, tv);
-      } else {
-	    schedule_generic(cb, tv, false);
+      schedule_generic(cb, tv, false);
+
+      return obj;
+}
+
+static struct __vpiCallback* make_at_start_of_sim_time(p_cb_data data)
+{
+      sync_callback*obj = new sync_callback(data);
+      struct sync_cb*cb = new sync_cb;
+      cb->sync_flag = false;
+      cb->handle = obj;
+      obj->cb_sync = cb;
+
+      vvp_time64_t tv = 0;
+      switch (obj->cb_time.type) {
+	  case vpiSimTime:
+	    tv = vpip_timestruct_to_time(&obj->cb_time);
+	    break;
+
+	  default:
+	    fprintf(stderr, "Unsupported time type %d.\n",
+	            (int)obj->cb_time.type);
+	    assert(0);
+	    break;
       }
 
+      vvp_time64_t cur = schedule_simtime();
+      if (cur > tv) {
+	    tv = 0;
+	    assert(0);
+      } else if (cur == tv) {
+	    tv = 0;
+      } else {
+	    tv -= cur;
+      }
+      schedule_at_start_of_simtime(cb, tv);
+
+      return obj;
+}
+
+static struct __vpiCallback* make_at_end_of_sim_time(p_cb_data data)
+{
+      sync_callback*obj = new sync_callback(data);
+      struct sync_cb*cb = new sync_cb;
+      cb->sync_flag = false;
+      cb->handle = obj;
+      obj->cb_sync = cb;
+
+      vvp_time64_t tv = 0;
+      switch (obj->cb_time.type) {
+	  case vpiSimTime:
+	    tv = vpip_timestruct_to_time(&obj->cb_time);
+	    break;
+
+	  default:
+	    fprintf(stderr, "Unsupported time type %d.\n",
+	            (int)obj->cb_time.type);
+	    assert(0);
+	    break;
+      }
+
+      vvp_time64_t cur = schedule_simtime();
+      if (cur > tv) {
+	    tv = 0;
+	    assert(0);
+      } else if (cur == tv) {
+	    tv = 0;
+      } else {
+	    tv -= cur;
+      }
+      schedule_at_end_of_simtime(cb, tv);
+
       return obj;
 }
 
@@ -573,11 +630,15 @@ vpiHandle vpi_register_cb(p_cb_data data)
 	    break;
 
 	  case cbAtStartOfSimTime:
-	    obj = make_afterdelay(data, true);
+	    obj = make_at_start_of_sim_time(data);
+	    break;
+
+	  case cbAtEndOfSimTime:
+	    obj = make_at_end_of_sim_time(data);
 	    break;
 
 	  case cbAfterDelay:
-	    obj = make_afterdelay(data, false);
+	    obj = make_afterdelay(data);
 	    break;
 
 	  case cbEndOfCompile: