From be2f61bce244223e6dd6df9bc29e8f0d96e7f55d Mon Sep 17 00:00:00 2001
From: Christoph Oelckers <coelckers@users.noreply.github.com>
Date: Thu, 18 Aug 2022 19:14:50 +0200
Subject: [PATCH] - optimized TVector3::XY() to return a writable reference.

---
 source/common/utility/vectors.h | 11 +++++++++--
 1 file changed, 9 insertions(+), 2 deletions(-)

diff --git a/source/common/utility/vectors.h b/source/common/utility/vectors.h
index 355591020..7a8ef5321 100644
--- a/source/common/utility/vectors.h
+++ b/source/common/utility/vectors.h
@@ -308,6 +308,8 @@ template<class vec_t>
 struct TVector3
 {
 	typedef TVector2<vec_t> Vector2;
+	// this does not compile - should be true on all relevant hardware.
+	//static_assert(myoffsetof(TVector3, X) == myoffsetof(Vector2, X) && myoffsetof(TVector3, Y) == myoffsetof(Vector2, Y), "TVector2 and TVector3 are not aligned");
 
 	vec_t X, Y, Z;
 
@@ -492,9 +494,14 @@ struct TVector3
 	}
 
 	// returns the XY fields as a 2D-vector.
-	Vector2 XY() const
+	const Vector2& XY() const
 	{
-		return{ X, Y };
+		return *reinterpret_cast<const Vector2*>(this);
+	}
+
+	Vector2& XY()
+	{
+		return *reinterpret_cast<Vector2*>(this);
 	}
 
 	// Add a 3D vector and a 2D vector.