From 5e5c08dc5ddf7989faf2f9f8ad76e260ba6385d7 Mon Sep 17 00:00:00 2001
From: Gangzheng Tong <tonggangzheng@gmail.com>
Date: Fri, 9 May 2025 02:00:39 -0700
Subject: Destroy unused witness table after hoisting (#7009)

* Destroy unused witness table after hoisting
---
 source/slang/slang-ir-autodiff.cpp | 3 +++
 1 file changed, 3 insertions(+)

diff --git a/source/slang/slang-ir-autodiff.cpp b/source/slang/slang-ir-autodiff.cpp
index f70e30b72..6ad8c5dbb 100644
--- a/source/slang/slang-ir-autodiff.cpp
+++ b/source/slang/slang-ir-autodiff.cpp
@@ -3249,6 +3249,9 @@ struct AutoDiffPass : public InstPassBase
                     }
                 }
 
+                // Destroy the old witness table
+                innerResult.diffWitness->replaceUsesWith(newWitnessTable);
+                innerResult.diffWitness->removeAndDeallocate();
                 result.diffWitness =
                     hoistValueFromGeneric(builder, newWitnessTable, specInst, true);
             }
-- 
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