From 241cf36a6d7735706804bb3c517529bbe078f1ee Mon Sep 17 00:00:00 2001
From: Mikko Rasa <tdb@tdb.fi>
Date: Mon, 8 Nov 2021 02:01:26 +0200
Subject: [PATCH] Process loop initialization outside the body in
 UnusedVariableRemover

If it's processed inside the scope of the loop, assignments to the
iteration variable may get discarded.
---
 source/glsl/optimize.cpp               |  8 ++++++-
 tests/glsl/complex_loop_increment.glsl | 30 ++++++++++++++++++++++++++
 2 files changed, 37 insertions(+), 1 deletion(-)
 create mode 100644 tests/glsl/complex_loop_increment.glsl

diff --git a/source/glsl/optimize.cpp b/source/glsl/optimize.cpp
index 3cb10e86..8008465e 100644
--- a/source/glsl/optimize.cpp
+++ b/source/glsl/optimize.cpp
@@ -1574,8 +1574,14 @@ void UnusedVariableRemover::visit(Iteration &iter)
 	vector<Node *> saved_refs;
 	swap(loop_ext_refs, saved_refs);
 	{
+		if(iter.init_statement)
+			iter.init_statement->visit(*this);
 		SetForScope<unsigned> set_loop(in_loop, in_loop+1);
-		TraversingVisitor::visit(iter);
+		if(iter.condition)
+			iter.condition->visit(*this);
+		iter.body.visit(*this);
+		if(iter.loop_expression)
+			iter.loop_expression->visit(*this);
 	}
 	swap(loop_ext_refs, saved_refs);
 
diff --git a/tests/glsl/complex_loop_increment.glsl b/tests/glsl/complex_loop_increment.glsl
new file mode 100644
index 00000000..fa0ea86e
--- /dev/null
+++ b/tests/glsl/complex_loop_increment.glsl
@@ -0,0 +1,30 @@
+#pragma MSP stage(vertex)
+void main()
+{
+	int n = 0;
+	for(int i=10; i!=1; )
+	{
+		if((i&1)==0)
+			i /= 2;
+		else
+			i = 3*i+1;
+		++n;
+	}
+	gl_Position = vec4(n);
+}
+
+/* Expected output: vertex
+void main()
+{
+	int n = 0;
+	for(int i = 10; i!=1;)
+	{
+		if((i&1)==0)
+			i /= 2;
+		else
+			i = 3*i+1;
+		++n;
+	}
+	gl_Position = vec4(0.0);
+}
+*/
-- 
2.43.0