From ffd7ec10071c2b956d9237ff81e082d30d4d0511 Mon Sep 17 00:00:00 2001
From: Todd Strader <todd.strader@gmail.com>
Date: Mon, 20 Oct 2025 11:16:36 -0400
Subject: [PATCH] Fix DFG synthesis non-determinism (#6557) (#6568)

---
 src/V3DfgSynthesize.cpp | 9 ++++++++-
 1 file changed, 8 insertions(+), 1 deletion(-)

diff --git a/src/V3DfgSynthesize.cpp b/src/V3DfgSynthesize.cpp
index cae9778ff..b5009fd88 100644
--- a/src/V3DfgSynthesize.cpp
+++ b/src/V3DfgSynthesize.cpp
@@ -531,7 +531,14 @@ class AstToDfgSynthesize final {
 
     // TYPES
     using Variable = std::conditional_t<T_Scoped, AstVarScope, AstVar>;
-    using SymTab = std::unordered_map<Variable*, DfgVertexVar*>;
+
+    // SymTab must be ordered in order to yield stable results
+    struct VariableComparator final {
+        bool operator()(const Variable* lhs, const Variable* rhs) const {
+            return lhs->name() < rhs->name();
+        }
+    };
+    using SymTab = std::map<Variable*, DfgVertexVar*, VariableComparator>;
 
     // Represents a [potentially partial] driver of a variable
     struct Driver final {