From b9a001eeac28d75e73ef643500724585e03d6714 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Tue, 2 Mar 2021 01:13:23 +0200
Subject: [PATCH] Remove expression statements without side effects

---
 source/glsl/optimize.cpp | 20 +++++++++++++++++++-
 source/glsl/optimize.h   |  3 +++
 2 files changed, 22 insertions(+), 1 deletion(-)

diff --git a/source/glsl/optimize.cpp b/source/glsl/optimize.cpp
index 40d1c26f..d6e5fa55 100644
--- a/source/glsl/optimize.cpp
+++ b/source/glsl/optimize.cpp
@@ -283,7 +283,8 @@ UnusedVariableRemover::UnusedVariableRemover():
 	aggregate(0),
 	assignment(0),
 	assignment_target(false),
-	assign_to_subscript(false)
+	assign_to_subscript(false),
+	side_effects(false)
 { }
 
 bool UnusedVariableRemover::apply(Stage &stage)
@@ -333,6 +334,13 @@ void UnusedVariableRemover::visit(MemberAccess &memacc)
 	unused_nodes.erase(memacc.declaration);
 }
 
+void UnusedVariableRemover::visit(UnaryExpression &unary)
+{
+	TraversingVisitor::visit(unary);
+	if(unary.oper=="++" || unary.oper=="--")
+		side_effects = true;
+}
+
 void UnusedVariableRemover::visit(BinaryExpression &binary)
 {
 	if(binary.oper=="[")
@@ -356,6 +364,13 @@ void UnusedVariableRemover::visit(Assignment &assign)
 	}
 	assign.right->visit(*this);
 	assignment = &assign;
+	side_effects = true;
+}
+
+void UnusedVariableRemover::visit(FunctionCall &call)
+{
+	TraversingVisitor::visit(call);
+	side_effects = true;
 }
 
 void UnusedVariableRemover::record_assignment(VariableDeclaration &var, Node &node, bool chained)
@@ -380,9 +395,12 @@ void UnusedVariableRemover::clear_assignments(VariableInfo &var_info, bool mark_
 void UnusedVariableRemover::visit(ExpressionStatement &expr)
 {
 	assignment = 0;
+	side_effects = false;
 	TraversingVisitor::visit(expr);
 	if(assignment && assignment->target_declaration)
 		record_assignment(*assignment->target_declaration, expr, (assignment->self_referencing || assign_to_subscript));
+	if(!side_effects)
+		unused_nodes.insert(&expr);
 }
 
 void UnusedVariableRemover::visit(StructDeclaration &strct)
diff --git a/source/glsl/optimize.h b/source/glsl/optimize.h
index eae90399..1c044fb4 100644
--- a/source/glsl/optimize.h
+++ b/source/glsl/optimize.h
@@ -124,6 +124,7 @@ private:
 	Assignment *assignment;
 	bool assignment_target;
 	bool assign_to_subscript;
+	bool side_effects;
 
 public:
 	UnusedVariableRemover();
@@ -134,10 +135,12 @@ private:
 	virtual void visit(VariableReference &);
 	virtual void visit(InterfaceBlockReference &);
 	virtual void visit(MemberAccess &);
+	virtual void visit(UnaryExpression &);
 	virtual void visit(BinaryExpression &);
 	virtual void visit(Assignment &);
 	void record_assignment(VariableDeclaration &, Node &, bool);
 	void clear_assignments(VariableInfo &, bool);
+	virtual void visit(FunctionCall &);
 	virtual void visit(ExpressionStatement &);
 	virtual void visit(StructDeclaration &);
 	virtual void visit(VariableDeclaration &);
-- 
2.43.0