Make Reactor destination variables non-const.

Bug swiftshader:27

Change-Id: I53e2e4858b10d810f649907fda98dc7863752551
Reviewed-on: https://swiftshader-review.googlesource.com/8090
Reviewed-by: Nicolas Capens <capn@google.com>
Tested-by: Nicolas Capens <capn@google.com>
Reviewed-on: https://swiftshader-review.googlesource.com/8232
Reviewed-by: Alexis Hétu <sugoi@google.com>

src/Shader/SetupRoutine.cpp

diff --git a/src/Shader/SetupRoutine.cpp b/src/Shader/SetupRoutine.cpp
index 1845047..c31bbec 100644
--- a/src/Shader/SetupRoutine.cpp
+++ b/src/Shader/SetupRoutine.cpp
@@ -555,25 +555,23 @@
 		}
 	}
 
-	void SetupRoutine::edge(Pointer<Byte> &primitive, Pointer<Byte> &data, const Int &X1, const Int &Y1, const Int &X2, const Int &Y2, Int &q)
+	void SetupRoutine::edge(Pointer<Byte> &primitive, Pointer<Byte> &data, const Int &Xa, const Int &Ya, const Int &Xb, const Int &Yb, Int &q)
 	{
-		If(Y1 != Y2)
+		If(Ya != Yb)
 		{
 			Int xMin = *Pointer<Int>(data + OFFSET(DrawData,scissorX0));
 			Int xMax = *Pointer<Int>(data + OFFSET(DrawData,scissorX1));
 
-			Bool swap = Y2 < Y1;
+			Bool swap = Yb < Ya;
 
 			Pointer<Byte> leftEdge = primitive + q * sizeof(Primitive) + OFFSET(Primitive,outline->left);
 			Pointer<Byte> rightEdge = primitive + q * sizeof(Primitive) + OFFSET(Primitive,outline->right);
 			Pointer<Byte> edge = IfThenElse(swap, rightEdge, leftEdge);
 
-			Int X0 = X1;
-			Int Y0 = Y1;
-			X1 = IfThenElse(swap, X2, X1);
-			X2 = IfThenElse(swap, X0, X2);
-			Y1 = IfThenElse(swap, Y2, Y1);
-			Y2 = IfThenElse(swap, Y0, Y2);
+			Int X1 = IfThenElse(swap, Xb, Xa);
+			Int X2 = IfThenElse(swap, Xa, Xb);
+			Int Y1 = IfThenElse(swap, Yb, Ya);
+			Int Y2 = IfThenElse(swap, Ya, Yb);
 
 			Int y1 = Max((Y1 + 0x0000000F) >> 4, *Pointer<Int>(data + OFFSET(DrawData,scissorY0)));
 			Int y2 = Min((Y2 + 0x0000000F) >> 4, *Pointer<Int>(data + OFFSET(DrawData,scissorY1)));