From 7c818d30f73c9d6820587781189a4f3990c0c55d Mon Sep 17 00:00:00 2001
From: Jannis Harder <me@jix.one>
Date: Thu, 25 Jan 2024 16:08:52 +0100
Subject: [PATCH] sim: Bring $print trigger/sampling semantics in line with FFs

---
 passes/sat/sim.cc | 66 +++++++++++++++++++++++++----------------------
 1 file changed, 35 insertions(+), 31 deletions(-)

diff --git a/passes/sat/sim.cc b/passes/sat/sim.cc
index 542eb5c18..aeed16b97 100644
--- a/passes/sat/sim.cc
+++ b/passes/sat/sim.cc
@@ -813,7 +813,7 @@ struct SimInstance
 		}
 	}
 
-	void update_ph3(bool check_assertions)
+	void update_ph3(bool gclk_trigger)
 	{
 		for (auto &it : ff_database)
 		{
@@ -858,49 +858,53 @@ struct SimInstance
 			Const en = get_state(cell->getPort(ID::EN));
 			Const args = get_state(cell->getPort(ID::ARGS));
 
-			if (!en.as_bool())
-				goto update_print;
+			bool sampled = trg_en && trg.size() > 0;
 
-			if (trg.size() > 0 && trg_en) {
-				Const trg_pol = cell->getParam(ID::TRG_POLARITY);
-				for (int i = 0; i < trg.size(); i++) {
-					bool pol = trg_pol[i] == State::S1;
-					State curr = trg[i], past = print.past_trg[i];
-					if (pol && curr == State::S1 && past == State::S0)
+			if (sampled ? print.past_en.as_bool() : en.as_bool()) {
+				if (sampled) {
+					sampled = true;
+					Const trg_pol = cell->getParam(ID::TRG_POLARITY);
+					for (int i = 0; i < trg.size(); i++) {
+						bool pol = trg_pol[i] == State::S1;
+						State curr = trg[i], past = print.past_trg[i];
+						if (pol && curr == State::S1 && past == State::S0)
+							triggered = true;
+						if (!pol && curr == State::S0 && past == State::S1)
+							triggered = true;
+					}
+				} else if (trg_en) {
+					// initial $print (TRG width = 0, TRG_ENABLE = true)
+					if (!print.initial_done && en != print.past_en)
 						triggered = true;
-					if (!pol && curr == State::S0 && past == State::S1)
+				} else if (cell->get_bool_attribute(ID(trg_on_gclk))) {
+					// unified $print for cycle based FV semantics
+					triggered = gclk_trigger;
+				} else {
+					// always @(*) $print
+					if (args != print.past_args || en != print.past_en)
 						triggered = true;
 				}
-			} else if (trg_en) {
-				// initial $print (TRG width = 0, TRG_ENABLE = true)
-				if (!print.initial_done && en != print.past_en)
-					triggered = true;
-			} else {
-				// always @(*) $print
-				if (args != print.past_args || en != print.past_en)
-					triggered = true;
-			}
 
-			if (triggered) {
-				int pos = 0;
-				for (auto &part : print.fmt.parts) {
-					part.sig = args.extract(pos, part.sig.size());
-					pos += part.sig.size();
+				if (triggered) {
+					int pos = 0;
+					for (auto &part : print.fmt.parts) {
+						part.sig = (sampled ? print.past_args : args).extract(pos, part.sig.size());
+						pos += part.sig.size();
+					}
+
+					std::string rendered = print.fmt.render();
+					log("%s", rendered.c_str());
+					shared->display_output.emplace_back(shared->step, this, cell, rendered);
 				}
-
-				std::string rendered = print.fmt.render();
-				log("%s", rendered.c_str());
-				shared->display_output.emplace_back(shared->step, this, cell, rendered);
 			}
 
-		update_print:
 			print.past_trg = trg;
 			print.past_en = en;
 			print.past_args = args;
 			print.initial_done = true;
 		}
 
-		if (check_assertions)
+		if (gclk_trigger)
 		{
 			for (auto cell : formal_database)
 			{
@@ -932,7 +936,7 @@ struct SimInstance
 		}
 
 		for (auto it : children)
-			it.second->update_ph3(check_assertions);
+			it.second->update_ph3(gclk_trigger);
 	}
 
 	void set_initstate_outputs(State state)