From 18291c20d2b17689729d9c36b08967e928e4e32a Mon Sep 17 00:00:00 2001
From: whitequark <whitequark@whitequark.org>
Date: Sun, 23 Dec 2018 09:04:23 +0000
Subject: [PATCH] proc_clean: remove any empty cases if all cases use all-def
 compare.

---
 kernel/rtlil.cc           | 10 ++++++++++
 kernel/rtlil.h            |  4 ++++
 passes/proc/proc_clean.cc | 34 ++++++++++++++++++++++++++++------
 3 files changed, 42 insertions(+), 6 deletions(-)

diff --git a/kernel/rtlil.cc b/kernel/rtlil.cc
index 14259f8ed..8404db5e9 100644
--- a/kernel/rtlil.cc
+++ b/kernel/rtlil.cc
@@ -3793,6 +3793,11 @@ RTLIL::CaseRule::~CaseRule()
 		delete *it;
 }
 
+bool RTLIL::CaseRule::empty() const
+{
+	return actions.empty() && switches.empty();
+}
+
 RTLIL::CaseRule *RTLIL::CaseRule::clone() const
 {
 	RTLIL::CaseRule *new_caserule = new RTLIL::CaseRule;
@@ -3809,6 +3814,11 @@ RTLIL::SwitchRule::~SwitchRule()
 		delete *it;
 }
 
+bool RTLIL::SwitchRule::empty() const
+{
+	return cases.empty();
+}
+
 RTLIL::SwitchRule *RTLIL::SwitchRule::clone() const
 {
 	RTLIL::SwitchRule *new_switchrule = new RTLIL::SwitchRule;
diff --git a/kernel/rtlil.h b/kernel/rtlil.h
index 276540aa1..f877622aa 100644
--- a/kernel/rtlil.h
+++ b/kernel/rtlil.h
@@ -1227,6 +1227,8 @@ struct RTLIL::CaseRule
 	~CaseRule();
 	void optimize();
 
+	bool empty() const;
+
 	template<typename T> void rewrite_sigspecs(T &functor);
 	RTLIL::CaseRule *clone() const;
 };
@@ -1238,6 +1240,8 @@ struct RTLIL::SwitchRule : public RTLIL::AttrObject
 
 	~SwitchRule();
 
+	bool empty() const;
+
 	template<typename T> void rewrite_sigspecs(T &functor);
 	RTLIL::SwitchRule *clone() const;
 };
diff --git a/passes/proc/proc_clean.cc b/passes/proc/proc_clean.cc
index 477d1ac60..3919e4b9c 100644
--- a/passes/proc/proc_clean.cc
+++ b/passes/proc/proc_clean.cc
@@ -77,14 +77,36 @@ void proc_clean_switch(RTLIL::SwitchRule *sw, RTLIL::CaseRule *parent, bool &did
 	}
 	else
 	{
-		for (auto cs : sw->cases) {
+		bool all_fully_def = true;
+		for (auto cs : sw->cases)
+		{
 			if (max_depth != 0)
 				proc_clean_case(cs, did_something, count, max_depth-1);
+			for (auto cmp : cs->compare)
+				if (!cmp.is_fully_def())
+					all_fully_def = false;
 		}
-		while (!sw->cases.empty() && (sw->cases.back()->actions.empty() && sw->cases.back()->switches.empty())) {
-			did_something = true;
-			delete sw->cases.back();
-			sw->cases.pop_back();
+		if (all_fully_def)
+		{
+			for (auto cs = sw->cases.begin(); cs != sw->cases.end();)
+			{
+				if ((*cs)->empty())
+				{
+					did_something = true;
+					delete *cs;
+					cs = sw->cases.erase(cs);
+				}
+				else ++cs;
+			}
+		}
+		else
+		{
+			while (!sw->cases.empty() && sw->cases.back()->empty())
+			{
+				did_something = true;
+				delete sw->cases.back();
+				sw->cases.pop_back();
+			}
 		}
 	}
 }
@@ -102,7 +124,7 @@ void proc_clean_case(RTLIL::CaseRule *cs, bool &did_something, int &count, int m
 	}
 	for (size_t i = 0; i < cs->switches.size(); i++) {
 		RTLIL::SwitchRule *sw = cs->switches[i];
-		if (sw->cases.size() == 0) {
+		if (sw->empty()) {
 			cs->switches.erase(cs->switches.begin() + (i--));
 			did_something = true;
 			delete sw;
-- 
2.30.2