From ba8f011189283dc591732b77fc3608fb996cc699 Mon Sep 17 00:00:00 2001
From: Aparajit Pratap <aparajit.pratap@autodesk.com>
Date: Thu, 7 Dec 2023 21:48:48 -0500
Subject: [PATCH] add code comments

---
 src/Engine/ProtoAssociative/CodeGen_SSA.cs | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/src/Engine/ProtoAssociative/CodeGen_SSA.cs b/src/Engine/ProtoAssociative/CodeGen_SSA.cs
index 9629d77b6b4..2958837dfc1 100644
--- a/src/Engine/ProtoAssociative/CodeGen_SSA.cs
+++ b/src/Engine/ProtoAssociative/CodeGen_SSA.cs
@@ -275,6 +275,10 @@ private List<AssociativeNode> BuildSSA(List<AssociativeNode> astList, ProtoCore.
                         BinaryExpressionNode bnode = (node as BinaryExpressionNode);
                         int generatedUID = ProtoCore.DSASM.Constants.kInvalidIndex;
 
+                        // Skip SSA for input ASTs that are first assigned null such as this:
+                        // a = null; (update "a") => a = <some primitive>;
+                        // SSA would break up the null AST into two assignments, which then breaks update:
+                        // a = null; (SSA) => temp = null; a = temp;
                         if (context.applySSATransform && core.Options.GenerateSSA && !bnode.IsInputExpression)
                         {
                             int ssaID = ProtoCore.DSASM.Constants.kInvalidIndex;