Update comments

Author: jkwak-work

source/slang/slang-ir-autodiff.cpp

@@ -1861,6 +1861,7 @@ IRInst* DifferentiableTypeConformanceContext::buildDifferentiablePairWitness(
             sharedContext->differentiableInterfaceType,
             (IRType*)pairType);
 
+        // Add WitnessTableEntry only once
         if (table->getFirstDecorationOrChild() == nullptr)
         {
             // And place it in the synthesized witness table.
@@ -1946,6 +1947,7 @@ IRInst* DifferentiableTypeConformanceContext::buildDifferentiablePairWitness(
             sharedContext->differentiablePtrInterfaceType,
             (IRType*)pairType);
 
+        // Add WitnessTableEntry only once
         if (table->getFirstDecorationOrChild() == nullptr)
         {
             // And place it in the synthesized witness table.
@@ -1992,6 +1994,7 @@ IRInst* DifferentiableTypeConformanceContext::buildArrayWitness(
             sharedContext->differentiableInterfaceType,
             (IRType*)arrayType);
 
+        // Add WitnessTableEntry only once
         if (table->getFirstDecorationOrChild() == nullptr)
         {
             // And place it in the synthesized witness table.
@@ -2074,6 +2077,7 @@ IRInst* DifferentiableTypeConformanceContext::buildArrayWitness(
             sharedContext->differentiablePtrInterfaceType,
             (IRType*)arrayType);
 
+        // Add WitnessTableEntry only once
         if (table->getFirstDecorationOrChild() == nullptr)
         {
             // And place it in the synthesized witness table.
@@ -2118,6 +2122,7 @@ IRInst* DifferentiableTypeConformanceContext::buildTupleWitness(
             sharedContext->differentiableInterfaceType,
             (IRType*)inTupleType);
 
+        // Add WitnessTableEntry only once
         if (table->getFirstDecorationOrChild() == nullptr)
         {
             // And place it in the synthesized witness table.
@@ -2234,6 +2239,7 @@ IRInst* DifferentiableTypeConformanceContext::buildTupleWitness(
             sharedContext->differentiablePtrInterfaceType,
             (IRType*)inTupleType);
 
+        // Add WitnessTableEntry only once
         if (table->getFirstDecorationOrChild() == nullptr)
         {
             // And place it in the synthesized witness table.
@@ -3096,6 +3102,7 @@ struct AutoDiffPass : public InstPassBase
             builder.createWitnessTable(autodiffContext->differentiableInterfaceType, originalType);
         result.diffWitness = origTypeIsDiffWitness;
 
+        // Add WitnessTableEntry only once
         if (origTypeIsDiffWitness->getFirstDecorationOrChild() == nullptr)
         {
             builder.createWitnessTableEntry(
@@ -3116,6 +3123,7 @@ struct AutoDiffPass : public InstPassBase
                 addMethod);
         }
 
+        // Add WitnessTableEntry only once
         if (diffTypeIsDiffWitness->getFirstDecorationOrChild() == nullptr)
         {
             builder.createWitnessTableEntry(
@@ -3212,6 +3220,7 @@ struct AutoDiffPass : public InstPassBase
                 auto witnessTableType = innerResult.diffWitness->getFullType();
                 auto newWitnessTable = builder.createWitnessTable(witnessTableType, concreteType);
 
+                // Add WitnessTableEntry only once
                 if (newWitnessTable->getFirstDecorationOrChild() == nullptr)
                 {
                     builder.setInsertInto(newWitnessTable);

source/slang/slang-ir-specialize.cpp

@@ -3029,31 +3029,6 @@ void finalizeSpecialization(IRModule* module)
     }
 }
 
-// Returns true when "a" depends on "b".
-bool IsIRInstDependOn(IRInst* a, IRInst* b)
-{
-    if (a->getFullType() == b)
-        return true;
-
-    for (UInt i = 0; i < a->getOperandCount(); i++)
-    {
-        auto operand = a->getOperand(i);
-        if (operand == b)
-            return true;
-    }
-
-    if (auto wt = as<IRWitnessTable>(a))
-    {
-        for (auto entry : wt->getEntries())
-        {
-            if (entry->getRequirementKey() == b || entry->getSatisfyingVal() == b)
-                return true;
-        }
-    }
-
-    return false;
-}
-
 IRInst* specializeGenericImpl(
     IRGeneric* genericVal,
     IRSpecialize* specializeInst,

source/slang/slang-ir.cpp

@@ -1696,10 +1696,11 @@ void addHoistableInst(IRBuilder* builder, IRInst* inst)
 
     if (inst->getOp() == kIROp_WitnessTable)
     {
-        // WitnessTable can refer to IRSpecialize from its WitnessTableEntry
-        // children. In this case, specialize insts must be cloned before the
-        // WitnessTable. Similar an WitnessTables can have depdency to another
-        // WitnessTable.
+        SLANG_ASSERT(getIROpInfo(kIROp_WitnessTable).isHoistable());
+
+        // WitnessTable can refer to IRSpecialize from its WitnessTableEntry children. In this case,
+        // specialize insts must be cloned before the WitnessTable. Similar an WitnessTables can
+        // have depdency to another WitnessTable.
         //
         for (IRInst* iter = insertBeforeInst; iter;)
         {
@@ -4633,7 +4634,7 @@ void addGlobalValue(IRBuilder* builder, IRInst* value)
         parent = builder->getModule()->getModuleInst();
     }
 
-    // If the value is already in the parent, keep it as it. Because WitnessTable is Hoistable, the
+    // If the value is already in the parent, keep it as-is. Because WitnessTable is Hoistable, the
     // parent can have only one instance of this WitnessTable. The order among siblings should
     // remain because the later siblings may have dependency to the earlier siblings.
     // 

source/slang/slang-lower-to-ir.cpp

@@ -8016,9 +8016,10 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
                             irWitnessTableBaseType,
                             irWitnessTable->getConcreteType());
 
-                        // Since IRWitnessTable is Hoistable, `createWitnessTable()` may return an
-                        // IRWitnessTable that already has decorations/children. We need to avoid
-                        // adding them more than once.
+                        // Since IRWitnessTable is Hoistable, `createWitnessTable()` may return
+                        // an IRWitnessTable that already has decorations/children. We should
+                        // add them only once.
+                        //
                         if (irSatisfyingWitnessTable->getFirstDecorationOrChild() == nullptr)
                         {
                             auto mangledName = getMangledNameForConformanceWitness(
@@ -8168,9 +8169,9 @@ struct DeclLoweringVisitor : DeclVisitor<DeclLoweringVisitor, LoweredValInfo>
             inheritanceDecl,
             LoweredValInfo::simple(findOuterMostGeneric(irWitnessTable)));
 
-        // Since IRWitnessTable is Hoistable, `createWitnessTable()` may return an
-        // IRWitnessTable that already has decorations/children. We need to avoid adding them
-        // more than once.
+        // Since IRWitnessTable is Hoistable, `createWitnessTable()` may return
+        // an IRWitnessTable that already has decorations/children. We should
+        // add them only once.
         //
         if (irWitnessTable->getFirstDecorationOrChild() == nullptr)
         {