From 6425fd2ec9c7e1e13c3afa7a79a9a2442d9e5c50 Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Sat, 9 Apr 2022 19:01:25 +0300
Subject: [PATCH] Don't add depth range conversion if an assignment to
 gl_Position.z exists

This is kinda crude since it triggers from any such assignment, but it
allows the idempotence test cases to work.
---
 source/glsl/finalize.cpp | 35 ++++++++++++++++++++++++++++++++++-
 source/glsl/finalize.h   | 10 ++++++++++
 2 files changed, 44 insertions(+), 1 deletion(-)

diff --git a/source/glsl/finalize.cpp b/source/glsl/finalize.cpp
index fcf48c61..85a6b07a 100644
--- a/source/glsl/finalize.cpp
+++ b/source/glsl/finalize.cpp
@@ -251,9 +251,42 @@ void DepthRangeConverter::apply(Stage &stage, const Features &features)
 	stage.content.visit(*this);
 }
 
+void DepthRangeConverter::visit(VariableReference &var)
+{
+	const StructDeclaration *strct = dynamic_cast<const StructDeclaration *>(var.type);
+	r_gl_pervertex = (strct && strct->block_name=="gl_PerVertex");
+}
+
+void DepthRangeConverter::visit(MemberAccess &memacc)
+{
+	r_gl_pervertex = false;
+	memacc.left->visit(*this);
+	r_gl_position = (r_gl_pervertex && memacc.member=="gl_Position");
+}
+
+void DepthRangeConverter::visit(Swizzle &swiz)
+{
+	r_gl_position = false;
+	swiz.left->visit(*this);
+	if(assignment_target && r_gl_position && swiz.count==1 && swiz.components[0]==2)
+		r_position_z_assigned = true;
+}
+
+void DepthRangeConverter::visit(Assignment &assign)
+{
+	{
+		SetFlag set_target(assignment_target);
+		assign.left->visit(*this);
+	}
+	assign.right->visit(*this);
+}
+
 void DepthRangeConverter::visit(FunctionDeclaration &func)
 {
-	if(func.definition==&func && func.name=="main")
+	r_position_z_assigned = false;
+	TraversingVisitor::visit(func);
+
+	if(func.definition==&func && func.name=="main" && !r_position_z_assigned)
 	{
 		VariableReference *position = new VariableReference;
 		position->name = "gl_Position";
diff --git a/source/glsl/finalize.h b/source/glsl/finalize.h
index 6e96c65e..ec5f459a 100644
--- a/source/glsl/finalize.h
+++ b/source/glsl/finalize.h
@@ -61,10 +61,20 @@ Converts the output depth range to match expectations of the target API.
 */
 class DepthRangeConverter: private TraversingVisitor
 {
+private:
+	bool assignment_target = false;
+	bool r_gl_pervertex = false;
+	bool r_gl_position = false;
+	bool r_position_z_assigned = false;
+
 public:
 	void apply(Stage &, const Features &);
 
 private:
+	virtual void visit(VariableReference &);
+	virtual void visit(MemberAccess &);
+	virtual void visit(Swizzle &);
+	virtual void visit(Assignment &);
 	virtual void visit(FunctionDeclaration &);
 };
 
-- 
2.45.2