From 78cec1556c85db6beb4f3d9f918b5a1f421719ef Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 12 Nov 2016 18:09:32 +0200
Subject: [PATCH] Fix unused variable decetion for self-referenging assignments

Extend it to initialization expressions as well.
---
 source/programcompiler.cpp | 52 +++++++++++++++++++++++++++++++-------
 source/programcompiler.h   |  3 +++
 2 files changed, 46 insertions(+), 9 deletions(-)

diff --git a/source/programcompiler.cpp b/source/programcompiler.cpp
index 934416c2..55f62ae9 100644
--- a/source/programcompiler.cpp
+++ b/source/programcompiler.cpp
@@ -627,22 +627,34 @@ void ProgramCompiler::VariableRenamer::visit(VariableDeclaration &var)
 
 ProgramCompiler::UnusedVariableLocator::UnusedVariableLocator():
 	assignment(false),
-	assignment_target(0)
+	record_target(false),
+	assignment_target(0),
+	indeterminate_target(false),
+	self_referencing(false)
 { }
 
 void ProgramCompiler::UnusedVariableLocator::visit(VariableReference &var)
 {
-	if(assignment)
-		assignment_target = var.declaration;
+	if(record_target)
+	{
+		if(assignment_target)
+			indeterminate_target = true;
+		else
+			assignment_target = var.declaration;
+	}
 	else
 	{
 		unused_nodes.erase(var.declaration);
+
 		map<VariableDeclaration *, Node *>::iterator i = assignments.find(var.declaration);
 		if(i!=assignments.end())
 		{
 			unused_nodes.erase(i->second);
 			assignments.erase(i);
 		}
+
+		if(assignment && var.declaration==assignment_target)
+			self_referencing = true;
 	}
 }
 
@@ -656,9 +668,20 @@ void ProgramCompiler::UnusedVariableLocator::visit(BinaryExpression &binary)
 {
 	if(binary.assignment)
 	{
-		binary.right->visit(*this);
 		assignment = true;
+		{
+			SetFlag set(record_target);
+			binary.left->visit(*this);
+		}
+		if(binary.oper!="=")
+			self_referencing = true;
+		binary.right->visit(*this);
+	}
+	else if(record_target && binary.oper=="[")
+	{
 		binary.left->visit(*this);
+		SetForScope<bool> set(record_target, false);
+		binary.right->visit(*this);
 	}
 	else
 		TraversingVisitor::visit(binary);
@@ -668,17 +691,21 @@ void ProgramCompiler::UnusedVariableLocator::visit(ExpressionStatement &expr)
 {
 	assignment = false;
 	assignment_target = 0;
+	indeterminate_target = false;
+	self_referencing = false;
 	TraversingVisitor::visit(expr);
-	if(assignment && assignment_target)
+	if(assignment && assignment_target && !indeterminate_target)
 	{
 		Node *&assign = assignments[assignment_target];
-		if(assign)
+		if(self_referencing)
+			unused_nodes.erase(assign);
+		else if(assign)
 			unused_nodes.insert(assign);
 		assign = &expr;
-		if(assignment_target->interface!="out" || (stage->type!=FRAGMENT && !assignment_target->linked_declaration))
-			unused_nodes.insert(&expr);
-		else
+		if(assignment_target->interface=="out" && (stage->type==FRAGMENT || assignment_target->linked_declaration))
 			unused_nodes.erase(assignment_target);
+		else
+			unused_nodes.insert(&expr);
 	}
 	assignment = false;
 }
@@ -686,6 +713,11 @@ void ProgramCompiler::UnusedVariableLocator::visit(ExpressionStatement &expr)
 void ProgramCompiler::UnusedVariableLocator::visit(VariableDeclaration &var)
 {
 	unused_nodes.insert(&var);
+	if(var.init_expression)
+	{
+		unused_nodes.insert(&*var.init_expression);
+		assignments[&var] = &*var.init_expression;
+	}
 	TraversingVisitor::visit(var);
 }
 
@@ -731,6 +763,8 @@ void ProgramCompiler::NodeRemover::visit(VariableDeclaration &var)
 		if(var.linked_declaration)
 			var.linked_declaration->linked_declaration = 0;
 	}
+	else if(var.init_expression && to_remove.count(&*var.init_expression))
+		var.init_expression = 0;
 }
 
 void ProgramCompiler::NodeRemover::visit(InterfaceBlock &iface)
diff --git a/source/programcompiler.h b/source/programcompiler.h
index 34b64b55..f1ea1652 100644
--- a/source/programcompiler.h
+++ b/source/programcompiler.h
@@ -100,7 +100,10 @@ private:
 		std::set<ProgramSyntax::Node *> unused_nodes;
 		std::map<ProgramSyntax::VariableDeclaration *, ProgramSyntax::Node *> assignments;
 		bool assignment;
+		bool record_target;
 		ProgramSyntax::VariableDeclaration *assignment_target;
+		bool indeterminate_target;
+		bool self_referencing;
 
 		UnusedVariableLocator();
 
-- 
2.43.0