Pass to the targets if an implicit T0 trigger event is needed.

elaborate.cc

@@ -4208,6 +4208,9 @@ NetProc* PEventStatement::elaborate_st(Design*des, NetScope*scope,
 	    if (synthesis || search_funcs_) {
 		  rem_out = true;
 	    }
+	      // If this is an always_comp/latch then we need an implicit T0
+	      // trigger of the event expression.
+	    if (search_funcs_) wa->set_t0_trigger();
 	    NexusSet*nset = enet->nex_input(rem_out, search_funcs_);
 	    if (nset == 0) {
 		  cerr << get_fileline() << ": error: Unable to elaborate:"
@@ -6111,7 +6114,7 @@ bool Design::check_proc_delay() const
 
       for (const NetProcTop*pr = procs_ ;  pr ;  pr = pr->next_) {
 	      /* If this is an always block and we have no or zero delay then
-	       * a runtime infinite loop will happen. If we possible have some
+	       * a runtime infinite loop will happen. If we possibly have some
 	       * delay then print a warning that an infinite loop is possible.
 	       */
 	    if ((pr->type() == IVL_PR_ALWAYS) ||

ivl.def

@@ -294,6 +294,7 @@ ivl_stmt_lval
 ivl_stmt_lvals
 ivl_stmt_lwidth
 ivl_stmt_name
+ivl_stmt_needs_t0_trigger
 ivl_stmt_nevent
 ivl_stmt_opcode
 ivl_stmt_parm

ivl_target.h

@@ -2105,6 +2105,7 @@ extern unsigned ivl_stmt_lineno(ivl_statement_t net);
  *    handle disable statements.
  *
  * ivl_stmt_events
+ * ivl_stmt_needs_t0_trigger
  * ivl_stmt_nevent
  *    Statements that have event arguments (TRIGGER and WAIT) make
  *    those event objects available through these methods.
@@ -2232,6 +2233,7 @@ extern ivl_expr_t ivl_stmt_delay_expr(ivl_statement_t net);
   /* IVL_ST_DELAY */
 extern uint64_t ivl_stmt_delay_val(ivl_statement_t net);
   /* IVL_ST_WAIT IVL_ST_TRIGGER */
+extern unsigned    ivl_stmt_needs_t0_trigger(ivl_statement_t net);
 extern unsigned    ivl_stmt_nevent(ivl_statement_t net);
 extern ivl_event_t ivl_stmt_events(ivl_statement_t net, unsigned idx);
   /* IVL_ST_CONTRIB */

netlist.h

@@ -3398,10 +3398,12 @@ class NetEvWait  : public NetProc {
 
       void add_event(NetEvent*tgt);
       void replace_event(NetEvent*orig, NetEvent*repl);
+      inline void set_t0_trigger() { has_t0_trigger_ = true; };
 
       inline unsigned nevents() const { return events_.size(); }
       inline const NetEvent*event(unsigned idx) const { return events_[idx]; }
       inline NetEvent*event(unsigned idx) { return events_[idx]; }
+      inline bool has_t0_trigger() const { return has_t0_trigger_; };
 
       NetProc*statement();
 
@@ -3442,6 +3444,7 @@ class NetEvWait  : public NetProc {
       NetProc*statement_;
 	// Events that I might wait for.
       std::vector<NetEvent*>events_;
+      bool has_t0_trigger_;
 };
 
 ostream& operator << (ostream&out, const NetEvWait&obj);

t-dll-api.cc

@@ -2815,6 +2815,16 @@ extern "C" uint64_t ivl_stmt_delay_val(ivl_statement_t net)
       return net->u_.delay_.value;
 }
 
+extern "C" unsigned ivl_stmt_needs_t0_trigger(ivl_statement_t net)
+{
+      assert(net);
+      if (net->type_ == IVL_ST_WAIT) {
+	    return net->u_.wait_.needs_t0_trigger;
+      } else {
+	    return 0;
+      }
+}
+
 extern "C" unsigned ivl_stmt_nevent(ivl_statement_t net)
 {
       assert(net);

t-dll-proc.cc

@@ -1,5 +1,5 @@
 /*
- * Copyright (c) 2000-2013 Stephen Williams (steve@icarus.com)
+ * Copyright (c) 2000-2017 Stephen Williams (steve@icarus.com)
  *
  *    This source code is free software; you can redistribute it
  *    and/or modify it in source code form under the terms of the GNU
@@ -847,12 +847,15 @@ bool dll_target::proc_wait(const NetEvWait*net)
 
 	/* This is a wait fork statement. */
       if ((net->nevents() == 1) && (net->event(0) == 0)) {
+	    stmt_cur_->u_.wait_.needs_t0_trigger = 0;
 	    stmt_cur_->u_.wait_.event = 0;
 	    stmt_cur_->type_ = IVL_ST_WAIT;
 	    stmt_cur_->u_.wait_.stmt_->type_ = IVL_ST_NOOP;
 	    return true;
       }
 
+      stmt_cur_->u_.wait_.needs_t0_trigger = net->has_t0_trigger();
+
 	// This event processing code is also in the NB assign above.
       if (net->nevents() > 1) {
 	    stmt_cur_->u_.wait_.events = (ivl_event_t*)

t-dll.h

@@ -862,6 +862,7 @@ struct ivl_statement_s {
 	    } utask_;
 
 	    struct { /* IVL_ST_TRIGGER IVL_ST_WAIT */
+		  unsigned needs_t0_trigger;
 		  unsigned nevent;
 		  union {
 			ivl_event_t event;