FIx issue with specializing witness tables (#4839)

1 files changed, 14 insertions, 1 deletions

diff --git a/source/slang/slang-ir-specialize.cpp b/source/slang/slang-ir-specialize.cpp
index 5c9e1ad24..c86906b2d 100644
--- a/source/slang/slang-ir-specialize.cpp
+++ b/source/slang/slang-ir-specialize.cpp
@@ -131,6 +131,15 @@ struct SpecializationContext
         return false;
     }
 
+    // Check if an inst is a dynamic dispatch witness table. 
+    // These insts may not have any uses yet, and do not have side effects,
+    // but should be specialized if necessary.
+    //
+    bool isWitnessTableType(IRInst* inst)
+    {
+        return inst->findDecoration<IRDynamicDispatchWitnessDecoration>();
+    }
+
     // When an instruction isn't fully specialized, but its operands *are*
     // then it is a candidate for specialization itself, so we will have
     // a query to check for the "all operands fully specialized" case.
@@ -826,8 +835,12 @@ struct SpecializationContext
                     // specialization opportunities (generic specialization,
                     // existential specialization, simplifications, etc.)
                     //
-                    if (inst->hasUses() || inst->mightHaveSideEffects())
+                    if (inst->hasUses() ||
+                        inst->mightHaveSideEffects() ||
+                        isWitnessTableType(inst))
+                    {
                         hasSpecialization |= maybeSpecializeInst(inst);
+                    }
 
                     // Finally, we need to make our logic recurse through
                     // the whole IR module, so we want to add the children