From 7caeb922a0fc9e5f8fc7b670d2f58d16d6156e50 Mon Sep 17 00:00:00 2001
From: Jannis Harder <me@jix.one>
Date: Thu, 25 May 2023 12:46:16 +0200
Subject: [PATCH] sim: Run level triggered async updates to fixpoint during
 initialization

---
 passes/sat/sim.cc | 28 +++++++++++++++++++++-------
 1 file changed, 21 insertions(+), 7 deletions(-)

diff --git a/passes/sat/sim.cc b/passes/sat/sim.cc
index 273e9db86..b970ee568 100644
--- a/passes/sat/sim.cc
+++ b/passes/sat/sim.cc
@@ -589,7 +589,7 @@ struct SimInstance
 		}
 	}
 
-	bool update_ph2(bool gclk)
+	bool update_ph2(bool gclk, bool stable_past_update = false)
 	{
 		bool did_something = false;
 
@@ -600,7 +600,7 @@ struct SimInstance
 
 			Const current_q = get_state(ff.data.sig_q);
 
-			if (ff_data.has_clk) {
+			if (ff_data.has_clk && !stable_past_update) {
 				// flip-flops
 				State current_clk = get_state(ff_data.sig_clk)[0];
 				if (ff_data.pol_clk ? (ff.past_clk == State::S0 && current_clk != State::S0) :
@@ -621,7 +621,7 @@ struct SimInstance
 			if (ff_data.has_aload) {
 				State current_aload = get_state(ff_data.sig_aload)[0];
 				if (current_aload == (ff_data.pol_aload ? State::S1 : State::S0)) {
-					current_q = ff_data.has_clk ? ff.past_ad : get_state(ff.data.sig_ad);
+					current_q = ff_data.has_clk && !stable_past_update ? ff.past_ad : get_state(ff.data.sig_ad);
 				}
 			}
 			// async reset
@@ -672,6 +672,8 @@ struct SimInstance
 				}
 				else
 				{
+					if (stable_past_update)
+						continue;
 					if (port.clk_polarity ?
 							(mdb.past_wr_clk[port_idx] == State::S1 || get_state(port.clk) != State::S1) :
 							(mdb.past_wr_clk[port_idx] == State::S0 || get_state(port.clk) != State::S0))
@@ -701,7 +703,7 @@ struct SimInstance
 		}
 
 		for (auto it : children)
-			if (it.second->update_ph2(gclk)) {
+			if (it.second->update_ph2(gclk, stable_past_update)) {
 				dirty_children.insert(it.second);
 				did_something = true;
 			}
@@ -1197,9 +1199,21 @@ struct SimWorker : SimShared
 
 	void initialize_stable_past()
 	{
-		if (debug)
-			log("\n-- ph1 (initialize) --\n");
-		top->update_ph1();
+
+		while (1)
+		{
+			if (debug)
+				log("\n-- ph1 (initialize) --\n");
+
+			top->update_ph1();
+
+			if (debug)
+				log("\n-- ph2 (initialize) --\n");
+
+			if (!top->update_ph2(false, true))
+				break;
+		}
+
 		if (debug)
 			log("\n-- ph3 (initialize) --\n");
 		top->update_ph3(true);