From: Mikko Rasa <tdb@tdb.fi>
Date: Sun, 17 Dec 2023 10:44:51 +0000 (+0200)
Subject: Fix some issues with inlining variables in GLSL
X-Git-Url: https://git.tdb.fi/?a=commitdiff_plain;h=8d8e54806c5270148b55b2b8475f5e546a1ca9da;p=libs%2Fgl.git

Fix some issues with inlining variables in GLSL
---

diff --git a/source/glsl/optimize.cpp b/source/glsl/optimize.cpp
index 0086a072..6b2f1a03 100644
--- a/source/glsl/optimize.cpp
+++ b/source/glsl/optimize.cpp
@@ -351,6 +351,17 @@ bool ExpressionInliner::apply(Stage &s)
 	return any_inlined;
 }
 
+void ExpressionInliner::visit(Block &block)
+{
+	TraversingVisitor::visit(block);
+
+	/* Block inlining of any assignments from the scope as we leave it.  They
+	may depend on local variables or might not always be executed. */
+	for(ExpressionInfo &e: expressions)
+		if(e.assign_scope==&block)
+			e.blocked = true;
+}
+
 void ExpressionInliner::visit(NodePtr<Expression> &expr)
 {
 	r_ref_info = nullptr;
@@ -371,11 +382,6 @@ void ExpressionInliner::visit(NodePtr<Expression> &expr)
 			for(Block *i=iteration_body->parent; (!use.blocked && i); i=i->parent)
 				use.blocked = (i==r_ref_info->assign_scope);
 		}
-
-		/* Block inlining assignments from from inner scopes.  The assignment may
-		depend on local variables of that scope or may not always be executed. */
-		for(Block *i=r_ref_info->assign_scope->parent; (!use.blocked && i); i=i->parent)
-			use.blocked = (i==current_block);
 	}
 	r_oper = expr->oper;
 	r_ref_info = nullptr;
@@ -459,8 +465,16 @@ void ExpressionInliner::visit(Assignment &assign)
 
 		for(; (i!=assignments.end() && i->first.declaration==assign.target.declaration); ++i)
 			if(targets_overlap(i->first, assign.target))
+			{
 				i->second->blocked = true;
 
+				/* Block further inlining of any expressions which used the
+				previous value of this variable. */
+				for(const ExpressionUse &u: i->second->uses)
+					if(u.containing_expr)
+						u.containing_expr->blocked = true;
+			}
+
 		info->trivial = r_trivial;
 		assignments[assign.target] = info;
 	}
diff --git a/source/glsl/optimize.h b/source/glsl/optimize.h
index d3d475b6..55b5e11b 100644
--- a/source/glsl/optimize.h
+++ b/source/glsl/optimize.h
@@ -142,6 +142,7 @@ public:
 	bool apply(Stage &);
 
 private:
+	void visit(Block &) override;
 	void visit(NodePtr<Expression> &) override;
 	void visit(VariableReference &) override;
 	void visit(MemberAccess &) override;
diff --git a/tests/glsl/swap.glsl b/tests/glsl/swap.glsl
new file mode 100644
index 00000000..de7d5250
--- /dev/null
+++ b/tests/glsl/swap.glsl
@@ -0,0 +1,57 @@
+#pragma MSP stage(vertex)
+layout(location=0) in vec4 vertex;
+void main()
+{
+	float x = vertex.x;
+	float y = vertex.y;
+	float z = vertex.z;
+	if(x>y)
+	{
+		float temp = x;
+		x = y;
+		y = temp;
+	}
+	if(y>z)
+	{
+		float temp = y;
+		y = z;
+		z = temp;
+	}
+	if(x>y)
+	{
+		float temp = x;
+		x = y;
+		y = temp;
+	}
+	gl_Position = vec4(x, y, z, 1.0);
+}
+
+/* Expected output: vertex
+layout(location=0) in vec4 vertex;
+void main()
+{
+	float x = vertex.x;
+	float y = vertex.y;
+	float z = vertex.z;
+	if(x>y)
+	{
+		float temp = x;
+		x = y;
+		y = temp;
+	}
+	if(y>z)
+	{
+		float temp = y;
+		y = z;
+		z = temp;
+	}
+	if(x>y)
+	{
+		float temp = x;
+		x = y;
+		y = temp;
+	}
+	gl_Position = vec4(x, y, z, 1.0);
+	gl_Position.z = gl_Position.z*2.0-gl_Position.w;
+}
+*/