[WGSL] Enable arbitrary arrays in uniform buffers. (#5497)

* [WGSL] Enable arbitrary arrays in uniform buffers.

* format code

* Undo irrelevant change and fixups.

* Update expected failure list.

* Fix.

* Rename.

---------

Co-authored-by: slangbot <186143334+slangbot@users.noreply.github.com>

6 files changed, 281 insertions, 100 deletions

diff --git a/source/slang/slang-emit.cpp b/source/slang/slang-emit.cpp
index c23195f7c..1950f251c 100644
--- a/source/slang/slang-emit.cpp
+++ b/source/slang/slang-emit.cpp
@@ -1455,7 +1455,10 @@ Result linkAndOptimizeIR(
     if (requiredLoweringPassSet.meshOutput)
         legalizeMeshOutputTypes(irModule);
 
-    lowerBufferElementTypeToStorageType(targetProgram, irModule);
+    BufferElementTypeLoweringOptions bufferElementTypeLoweringOptions;
+    bufferElementTypeLoweringOptions.use16ByteArrayElementForConstantBuffer =
+        isWGPUTarget(targetRequest);
+    lowerBufferElementTypeToStorageType(targetProgram, irModule, bufferElementTypeLoweringOptions);
 
     // Rewrite functions that return arrays to return them via `out` parameter,
     // since our target languages doesn't allow returning arrays.
diff --git a/source/slang/slang-ir-insts.h b/source/slang/slang-ir-insts.h
index 9a081f9de..4baa786e3 100644
--- a/source/slang/slang-ir-insts.h
+++ b/source/slang/slang-ir-insts.h
@@ -3566,6 +3566,7 @@ public:
     IRInst* replaceOperand(IRUse* use, IRInst* newValue);
 
     IRInst* getBoolValue(bool value);
+    IRInst* getIntValue(IRIntegerValue value);
     IRInst* getIntValue(IRType* type, IRIntegerValue value);
     IRInst* getFloatValue(IRType* type, IRFloatingPointValue value);
     IRStringLit* getStringValue(const UnownedStringSlice& slice);
diff --git a/source/slang/slang-ir-lower-buffer-element-type.cpp b/source/slang/slang-ir-lower-buffer-element-type.cpp
index 7d722bf9c..f9017ebe1 100644
--- a/source/slang/slang-ir-lower-buffer-element-type.cpp
+++ b/source/slang/slang-ir-lower-buffer-element-type.cpp
@@ -12,6 +12,47 @@ struct LoweredElementTypeContext
 {
     static const IRIntegerValue kMaxArraySizeToUnroll = 32;
 
+    enum ConversionMethodKind
+    {
+        Func,
+        Opcode
+    };
+    struct ConversionMethod
+    {
+        ConversionMethodKind kind = ConversionMethodKind::Func;
+        union
+        {
+            IRFunc* func;
+            IROp op;
+        };
+        ConversionMethod() { func = nullptr; }
+        operator bool()
+        {
+            return kind == ConversionMethodKind::Func ? func != nullptr : op != kIROp_Nop;
+        }
+        ConversionMethod& operator=(IRFunc* f)
+        {
+            kind = ConversionMethodKind::Func;
+            this->func = f;
+            return *this;
+        }
+        ConversionMethod& operator=(IROp irop)
+        {
+            kind = ConversionMethodKind::Opcode;
+            this->op = irop;
+            return *this;
+        }
+        IRInst* apply(IRBuilder& builder, IRType* resultType, IRInst* operand)
+        {
+            if (!*this)
+                return operand;
+            if (kind == ConversionMethodKind::Func)
+                return builder.emitCallInst(resultType, func, 1, &operand);
+            else
+                return builder.emitIntrinsicInst(resultType, op, 1, &operand);
+        }
+    };
+
     struct LoweredElementTypeInfo
     {
         IRType* originalType;
@@ -22,25 +63,48 @@ struct LoweredElementTypeContext
         IRStructKey* loweredInnerStructKey =
             nullptr; // For matrix/array types that are lowered into a struct type, this is the
                      // struct key of the data field.
-        IRFunc* convertOriginalToLowered = nullptr;
-        IRFunc* convertLoweredToOriginal = nullptr;
+        ConversionMethod convertOriginalToLowered;
+        ConversionMethod convertLoweredToOriginal;
     };
 
     Dictionary<IRType*, LoweredElementTypeInfo> loweredTypeInfo[(int)IRTypeLayoutRuleName::_Count];
     Dictionary<IRType*, LoweredElementTypeInfo>
         mapLoweredTypeToInfo[(int)IRTypeLayoutRuleName::_Count];
 
+    struct ConversionMethodKey
+    {
+        IRType* toType;
+        IRType* fromType;
+        bool operator==(const ConversionMethodKey& other) const
+        {
+            return toType == other.toType && fromType == other.fromType;
+        }
+        HashCode64 getHashCode() const
+        {
+            return combineHash(Slang::getHashCode(toType), Slang::getHashCode(fromType));
+        }
+    };
+
+    Dictionary<ConversionMethodKey, ConversionMethod> conversionMethodMap;
+    ConversionMethod getConversionMethod(IRType* toType, IRType* fromType)
+    {
+        ConversionMethodKey key;
+        key.toType = toType;
+        key.fromType = fromType;
+        ConversionMethod method;
+        conversionMethodMap.tryGetValue(key, method);
+        return method;
+    }
+
     SlangMatrixLayoutMode defaultMatrixLayout = SLANG_MATRIX_LAYOUT_ROW_MAJOR;
     TargetProgram* target;
-    bool lowerBufferPointer = false;
+    BufferElementTypeLoweringOptions options;
 
     LoweredElementTypeContext(
         TargetProgram* target,
-        bool lowerBufferPointer,
+        BufferElementTypeLoweringOptions inOptions,
         SlangMatrixLayoutMode inDefaultMatrixLayout)
-        : target(target)
-        , defaultMatrixLayout(inDefaultMatrixLayout)
-        , lowerBufferPointer(lowerBufferPointer)
+        : target(target), defaultMatrixLayout(inDefaultMatrixLayout), options(inOptions)
     {
     }
 
@@ -133,6 +197,11 @@ struct LoweredElementTypeContext
                     auto element = elements[(Index)(r * colCount + c)];
                     vecArgs.add(element);
                 }
+                // Fill in default values for remaining elements in the vector.
+                for (IRIntegerValue r = rowCount; r < getIntVal(vectorType->getElementCount()); r++)
+                {
+                    vecArgs.add(builder.emitDefaultConstruct(vectorType->getElementType()));
+                }
                 auto colVector = builder.emitMakeVector(
                     vectorType,
                     (UInt)vecArgs.getCount(),
@@ -150,6 +219,11 @@ struct LoweredElementTypeContext
                     auto element = elements[(Index)(r * colCount + c)];
                     vecArgs.add(element);
                 }
+                // Fill in default values for remaining elements in the vector.
+                for (IRIntegerValue c = colCount; c < getIntVal(vectorType->getElementCount()); c++)
+                {
+                    vecArgs.add(builder.emitDefaultConstruct(vectorType->getElementType()));
+                }
                 auto rowVector = builder.emitMakeVector(
                     vectorType,
                     (UInt)vecArgs.getCount(),
@@ -192,13 +266,10 @@ struct LoweredElementTypeContext
             for (IRIntegerValue ii = 0; ii < count; ++ii)
             {
                 auto packedElement = builder.emitElementExtract(packedArray, ii);
-                auto originalElement = innerTypeInfo.convertLoweredToOriginal
-                                           ? builder.emitCallInst(
-                                                 innerTypeInfo.originalType,
-                                                 innerTypeInfo.convertLoweredToOriginal,
-                                                 1,
-                                                 &packedElement)
-                                           : packedElement;
+                auto originalElement = innerTypeInfo.convertLoweredToOriginal.apply(
+                    builder,
+                    innerTypeInfo.originalType,
+                    packedElement);
                 args[(Index)ii] = originalElement;
             }
             result = builder.emitMakeArray(arrayType, (UInt)args.getCount(), args.getBuffer());
@@ -218,13 +289,10 @@ struct LoweredElementTypeContext
 
             builder.setInsertBefore(loopBodyBlock->getFirstOrdinaryInst());
             auto packedElement = builder.emitElementExtract(packedArray, loopParam);
-            auto originalElement = innerTypeInfo.convertLoweredToOriginal
-                                       ? builder.emitCallInst(
-                                             innerTypeInfo.originalType,
-                                             innerTypeInfo.convertLoweredToOriginal,
-                                             1,
-                                             &packedElement)
-                                       : packedElement;
+            auto originalElement = innerTypeInfo.convertLoweredToOriginal.apply(
+                builder,
+                innerTypeInfo.originalType,
+                packedElement);
             auto varPtr = builder.emitElementAddress(resultVar, loopParam);
             builder.emitStore(varPtr, originalElement);
             builder.setInsertInto(loopBreakBlock);
@@ -259,13 +327,10 @@ struct LoweredElementTypeContext
             for (IRIntegerValue ii = 0; ii < count; ++ii)
             {
                 auto originalElement = builder.emitElementExtract(originalParam, ii);
-                auto packedElement = innerTypeInfo.convertOriginalToLowered
-                                         ? builder.emitCallInst(
-                                               innerTypeInfo.loweredType,
-                                               innerTypeInfo.convertOriginalToLowered,
-                                               1,
-                                               &originalElement)
-                                         : originalElement;
+                auto packedElement = innerTypeInfo.convertOriginalToLowered.apply(
+                    builder,
+                    innerTypeInfo.loweredType,
+                    originalElement);
                 args[(Index)ii] = packedElement;
             }
             packedArray =
@@ -286,13 +351,10 @@ struct LoweredElementTypeContext
 
             builder.setInsertBefore(loopBodyBlock->getFirstOrdinaryInst());
             auto originalElement = builder.emitElementExtract(originalParam, loopParam);
-            auto packedElement = innerTypeInfo.convertOriginalToLowered
-                                     ? builder.emitCallInst(
-                                           innerTypeInfo.loweredType,
-                                           innerTypeInfo.convertOriginalToLowered,
-                                           1,
-                                           &originalElement)
-                                     : originalElement;
+            auto packedElement = innerTypeInfo.convertOriginalToLowered.apply(
+                builder,
+                innerTypeInfo.loweredType,
+                originalElement);
             auto varPtr = builder.emitElementAddress(packedArrayVar, loopParam);
             builder.emitStore(varPtr, packedElement);
             builder.setInsertInto(loopBreakBlock);
@@ -319,6 +381,17 @@ struct LoweredElementTypeContext
         }
     }
 
+    // Returns the number of elements N that ensures the IRVectorType(elementType,N)
+    // has 16-byte aligned size and N is no less than `minCount`.
+    IRIntegerValue get16ByteAlignedVectorElementCount(IRType* elementType, IRIntegerValue minCount)
+    {
+        IRSizeAndAlignment sizeAlignment;
+        getNaturalSizeAndAlignment(target->getOptionSet(), elementType, &sizeAlignment);
+        if (sizeAlignment.size)
+            return align(sizeAlignment.size * minCount, 16) / sizeAlignment.size;
+        return 4;
+    }
+
     LoweredElementTypeInfo getLoweredTypeInfoImpl(IRType* type, IRTypeLayoutRules* rules)
     {
         IRBuilder builder(type);
@@ -357,9 +430,18 @@ struct LoweredElementTypeContext
             builder.addNameHintDecoration(loweredType, nameSB.produceString().getUnownedSlice());
             auto structKey = builder.createStructKey();
             builder.addNameHintDecoration(structKey, UnownedStringSlice("data"));
-            auto vectorType = builder.getVectorType(
-                matrixType->getElementType(),
-                isColMajor ? matrixType->getRowCount() : matrixType->getColumnCount());
+            auto vectorSize = isColMajor ? matrixType->getRowCount() : matrixType->getColumnCount();
+            if (rules->ruleName == IRTypeLayoutRuleName::Std140 &&
+                options.use16ByteArrayElementForConstantBuffer)
+            {
+                // For constant buffer layout, we need to use 16-byte aligned vector if
+                // we are required to ensure array element types has 16-byte stride.
+                vectorSize = builder.getIntValue(get16ByteAlignedVectorElementCount(
+                    matrixType->getElementType(),
+                    getIntVal(vectorSize)));
+            }
+
+            auto vectorType = builder.getVectorType(matrixType->getElementType(), vectorSize);
             IRSizeAndAlignment elementSizeAlignment;
             getSizeAndAlignment(target->getOptionSet(), rules, vectorType, &elementSizeAlignment);
             elementSizeAlignment = rules->alignCompositeElement(elementSizeAlignment);
@@ -382,6 +464,52 @@ struct LoweredElementTypeContext
         else if (auto arrayType = as<IRArrayType>(type))
         {
             auto loweredInnerTypeInfo = getLoweredTypeInfo(arrayType->getElementType(), rules);
+
+            if (rules->ruleName == IRTypeLayoutRuleName::Std140 &&
+                options.use16ByteArrayElementForConstantBuffer)
+            {
+                // For constant buffer layout, we need to use 16-byte-aligned vector if
+                // we are required to ensure array element types has 16-byte stride.
+                // We only need to handle the case where the element type is a scalar or vector
+                // type here, because if the element type is a matrix type or struct type,
+                // the size promotion will be handled during lowering of the element type.
+                IRType* packedVectorType = nullptr;
+                if (auto vectorType = as<IRVectorType>(loweredInnerTypeInfo.loweredType))
+                {
+                    packedVectorType = builder.getVectorType(
+                        vectorType->getElementType(),
+                        builder.getIntValue(get16ByteAlignedVectorElementCount(
+                            vectorType->getElementType(),
+                            getIntVal(vectorType->getElementCount()))));
+                    if (packedVectorType != loweredInnerTypeInfo.originalType)
+                    {
+                        loweredInnerTypeInfo.convertLoweredToOriginal = kIROp_VectorReshape;
+                        loweredInnerTypeInfo.convertOriginalToLowered = kIROp_VectorReshape;
+                    }
+                }
+                else if (auto scalarType = as<IRBasicType>(loweredInnerTypeInfo.loweredType))
+                {
+                    packedVectorType = builder.getVectorType(
+                        loweredInnerTypeInfo.loweredType,
+                        get16ByteAlignedVectorElementCount(scalarType, 1));
+                    loweredInnerTypeInfo.convertLoweredToOriginal = kIROp_VectorReshape;
+                    loweredInnerTypeInfo.convertOriginalToLowered = kIROp_MakeVectorFromScalar;
+                }
+                if (packedVectorType)
+                {
+                    loweredInnerTypeInfo.loweredType = packedVectorType;
+                    if (loweredInnerTypeInfo.convertLoweredToOriginal)
+                        conversionMethodMap[ConversionMethodKey{
+                            packedVectorType,
+                            loweredInnerTypeInfo.originalType}] =
+                            loweredInnerTypeInfo.convertOriginalToLowered;
+                    if (loweredInnerTypeInfo.convertOriginalToLowered)
+                        conversionMethodMap[ConversionMethodKey{
+                            loweredInnerTypeInfo.originalType,
+                            packedVectorType}] = loweredInnerTypeInfo.convertLoweredToOriginal;
+                }
+            }
+
             // For spirv backend, we always want to lower all array types, even if the element type
             // comes out the same. This is because different layout rules may have different array
             // stride requirements.
@@ -393,6 +521,7 @@ struct LoweredElementTypeContext
                     return info;
                 }
             }
+
             auto loweredType = builder.createStructType();
             info.loweredType = loweredType;
             StringBuilder nameSB;
@@ -486,11 +615,11 @@ struct LoweredElementTypeContext
             {
                 builder.setInsertAfter(loweredType);
                 info.convertLoweredToOriginal = builder.createFunc();
-                builder.setInsertInto(info.convertLoweredToOriginal);
+                builder.setInsertInto(info.convertLoweredToOriginal.func);
                 builder.addNameHintDecoration(
-                    info.convertLoweredToOriginal,
+                    info.convertLoweredToOriginal.func,
                     UnownedStringSlice("unpackStorage"));
-                info.convertLoweredToOriginal->setFullType(
+                info.convertLoweredToOriginal.func->setFullType(
                     builder.getFuncType(1, (IRType**)&loweredType, type));
                 builder.emitBlock();
                 auto loweredParam = builder.emitParam(loweredType);
@@ -508,13 +637,10 @@ struct LoweredElementTypeContext
                         loweredParam,
                         field->getKey());
                     auto unpackedField =
-                        fieldLoweredTypeInfo[fieldId].convertLoweredToOriginal
-                            ? builder.emitCallInst(
-                                  field->getFieldType(),
-                                  fieldLoweredTypeInfo[fieldId].convertLoweredToOriginal,
-                                  1,
-                                  &storageField)
-                            : storageField;
+                        fieldLoweredTypeInfo[fieldId].convertLoweredToOriginal.apply(
+                            builder,
+                            field->getFieldType(),
+                            storageField);
                     args.add(unpackedField);
                     fieldId++;
                 }
@@ -524,13 +650,13 @@ struct LoweredElementTypeContext
 
             // Create pack func.
             {
-                builder.setInsertAfter(info.convertLoweredToOriginal);
+                builder.setInsertAfter(info.convertLoweredToOriginal.func);
                 info.convertOriginalToLowered = builder.createFunc();
-                builder.setInsertInto(info.convertOriginalToLowered);
+                builder.setInsertInto(info.convertOriginalToLowered.func);
                 builder.addNameHintDecoration(
-                    info.convertOriginalToLowered,
+                    info.convertOriginalToLowered.func,
                     UnownedStringSlice("packStorage"));
-                info.convertOriginalToLowered->setFullType(
+                info.convertOriginalToLowered.func->setFullType(
                     builder.getFuncType(1, (IRType**)&type, loweredType));
                 builder.emitBlock();
                 auto param = builder.emitParam(type);
@@ -545,14 +671,10 @@ struct LoweredElementTypeContext
                     }
                     auto fieldVal =
                         builder.emitFieldExtract(field->getFieldType(), param, field->getKey());
-                    auto packedField =
-                        fieldLoweredTypeInfo[fieldId].convertOriginalToLowered
-                            ? builder.emitCallInst(
-                                  fieldLoweredTypeInfo[fieldId].loweredType,
-                                  fieldLoweredTypeInfo[fieldId].convertOriginalToLowered,
-                                  1,
-                                  &fieldVal)
-                            : fieldVal;
+                    auto packedField = fieldLoweredTypeInfo[fieldId].convertOriginalToLowered.apply(
+                        builder,
+                        fieldLoweredTypeInfo[fieldId].loweredType,
+                        fieldVal);
                     args.add(packedField);
                     fieldId++;
                 }
@@ -587,11 +709,11 @@ struct LoweredElementTypeContext
                         {
                             builder.setInsertAfter(type);
                             info.convertLoweredToOriginal = builder.createFunc();
-                            builder.setInsertInto(info.convertLoweredToOriginal);
+                            builder.setInsertInto(info.convertLoweredToOriginal.func);
                             builder.addNameHintDecoration(
-                                info.convertLoweredToOriginal,
+                                info.convertLoweredToOriginal.func,
                                 UnownedStringSlice("unpackStorage"));
-                            info.convertLoweredToOriginal->setFullType(
+                            info.convertLoweredToOriginal.func->setFullType(
                                 builder.getFuncType(1, (IRType**)&info.loweredType, type));
                             builder.emitBlock();
                             auto loweredParam = builder.emitParam(info.loweredType);
@@ -601,13 +723,13 @@ struct LoweredElementTypeContext
 
                         // Create pack func.
                         {
-                            builder.setInsertAfter(info.convertLoweredToOriginal);
+                            builder.setInsertAfter(info.convertLoweredToOriginal.func);
                             info.convertOriginalToLowered = builder.createFunc();
-                            builder.setInsertInto(info.convertOriginalToLowered);
+                            builder.setInsertInto(info.convertOriginalToLowered.func);
                             builder.addNameHintDecoration(
-                                info.convertOriginalToLowered,
+                                info.convertOriginalToLowered.func,
                                 UnownedStringSlice("packStorage"));
-                            info.convertOriginalToLowered->setFullType(
+                            info.convertOriginalToLowered.func->setFullType(
                                 builder.getFuncType(1, (IRType**)&type, info.loweredType));
                             builder.emitBlock();
                             auto param = builder.emitParam(type);
@@ -644,6 +766,8 @@ struct LoweredElementTypeContext
         getSizeAndAlignment(target->getOptionSet(), rules, info.loweredType, &sizeAlignment);
         loweredTypeInfo[(int)rules->ruleName].set(type, info);
         mapLoweredTypeToInfo[(int)rules->ruleName].set(info.loweredType, info);
+        conversionMethodMap[{info.originalType, info.loweredType}] = info.convertLoweredToOriginal;
+        conversionMethodMap[{info.loweredType, info.originalType}] = info.convertOriginalToLowered;
         return info;
     }
 
@@ -693,7 +817,7 @@ struct LoweredElementTypeContext
         for (auto globalInst : module->getGlobalInsts())
         {
             IRType* elementType = nullptr;
-            if (lowerBufferPointer)
+            if (options.lowerBufferPointer)
             {
                 if (auto ptrType = as<IRPtrType>(globalInst))
                 {
@@ -729,7 +853,8 @@ struct LoweredElementTypeContext
             auto loweredBufferElementTypeInfo = getLoweredTypeInfo(elementType, layoutRules);
 
             // If the lowered type is the same as original type, no change is required.
-            if (!loweredBufferElementTypeInfo.convertLoweredToOriginal)
+            if (loweredBufferElementTypeInfo.loweredType ==
+                loweredBufferElementTypeInfo.originalType)
                 continue;
 
             builder.setInsertBefore(bufferType);
@@ -862,8 +987,41 @@ struct LoweredElementTypeContext
                     }
                 }
 
-                auto loweredElementTypeInfo =
-                    getLoweredTypeInfo((IRType*)originalElementType, layoutRules);
+                LoweredElementTypeInfo loweredElementTypeInfo = {};
+                if (auto getElementPtr = as<IRGetElementPtr>(ptrVal))
+                {
+                    if (auto arrayType = as<IRArrayTypeBase>(
+                            tryGetPointedToType(&builder, getElementPtr->getBase()->getDataType())))
+                    {
+                        // For WGSL, an array of scalar or vector type will always be converted to
+                        // an array of 16-byte aligned vector type. In this case, we will run into a
+                        // GetElementPtr where the result type is different from the element type of
+                        // the base array.
+                        // We should setup loweredElementTypeInfo so the remaining logic can handle
+                        // this case and insert proper packing/unpacking logic around it.
+                        if (arrayType->getElementType() != originalElementType)
+                        {
+                            loweredElementTypeInfo.loweredType = arrayType->getElementType();
+                            loweredElementTypeInfo.originalType = (IRType*)originalElementType;
+                            loweredElementTypeInfo.convertLoweredToOriginal = getConversionMethod(
+                                loweredElementTypeInfo.originalType,
+                                loweredElementTypeInfo.loweredType);
+                            loweredElementTypeInfo.convertOriginalToLowered = getConversionMethod(
+                                loweredElementTypeInfo.loweredType,
+                                loweredElementTypeInfo.originalType);
+                        }
+                    }
+                }
+
+                // For general cases we simply check if the element type needs lowering.
+                // If so we will insert packing/unpacking logic if necessary.
+                //
+                if (!loweredElementTypeInfo.loweredType)
+                {
+                    loweredElementTypeInfo =
+                        getLoweredTypeInfo((IRType*)originalElementType, layoutRules);
+                }
+
                 if (!loweredElementTypeInfo.convertLoweredToOriginal)
                     continue;
 
@@ -891,11 +1049,11 @@ struct LoweredElementTypeContext
                                 builder.setInsertBefore(user);
                                 auto newLoad = cloneInst(&cloneEnv, &builder, user);
                                 newLoad->setFullType(loweredElementTypeInfo.loweredType);
-                                auto unpackedVal = builder.emitCallInst(
-                                    (IRType*)originalElementType,
-                                    loweredElementTypeInfo.convertLoweredToOriginal,
-                                    1,
-                                    &newLoad);
+                                auto unpackedVal =
+                                    loweredElementTypeInfo.convertLoweredToOriginal.apply(
+                                        builder,
+                                        loweredElementTypeInfo.originalType,
+                                        newLoad);
                                 user->replaceUsesWith(unpackedVal);
                                 user->removeAndDeallocate();
                                 break;
@@ -910,11 +1068,11 @@ struct LoweredElementTypeContext
                                 IRCloneEnv cloneEnv = {};
                                 builder.setInsertBefore(user);
                                 auto originalVal = getStoreVal(user);
-                                auto packedVal = builder.emitCallInst(
-                                    loweredElementTypeInfo.loweredType,
-                                    loweredElementTypeInfo.convertOriginalToLowered,
-                                    1,
-                                    &originalVal);
+                                auto packedVal =
+                                    loweredElementTypeInfo.convertOriginalToLowered.apply(
+                                        builder,
+                                        loweredElementTypeInfo.loweredType,
+                                        originalVal);
                                 if (auto store = as<IRStore>(user))
                                     store->val.set(packedVal);
                                 else if (auto sbStore = as<IRRWStructuredBufferStore>(user))
@@ -954,9 +1112,9 @@ struct LoweredElementTypeContext
                                 }
                                 else
                                 {
-                                    // If we getting a derived address from the pointer, we need to
-                                    // recursively lower the new address. We do so by pushing the
-                                    // address inst into the work list.
+                                    // If we getting a derived address from the pointer, we need
+                                    // to recursively lower the new address. We do so by pushing
+                                    // the address inst into the work list.
                                     ptrValsWorkList.add(user);
                                 }
                             }
@@ -973,7 +1131,8 @@ struct LoweredElementTypeContext
                                 // an argument, we don't need to do any marshalling here.
                                 if (as<IRHLSLStructuredBufferTypeBase>(ptrVal->getDataType()))
                                     break;
-                                if (lowerBufferPointer && as<IRPtrType>(ptrVal->getDataType()))
+                                if (options.lowerBufferPointer &&
+                                    as<IRPtrType>(ptrVal->getDataType()))
                                     break;
                                 // If we are calling a function with an l-value pointer from buffer
                                 // access, we need to materialize the object as a local variable,
@@ -981,21 +1140,21 @@ struct LoweredElementTypeContext
                                 builder.setInsertBefore(user);
                                 auto newLoad =
                                     builder.emitLoad(loweredElementTypeInfo.loweredType, ptrVal);
-                                auto unpackedVal = builder.emitCallInst(
-                                    (IRType*)originalElementType,
-                                    loweredElementTypeInfo.convertLoweredToOriginal,
-                                    1,
-                                    &newLoad);
+                                auto unpackedVal =
+                                    loweredElementTypeInfo.convertLoweredToOriginal.apply(
+                                        builder,
+                                        (IRType*)originalElementType,
+                                        newLoad);
                                 auto var = builder.emitVar((IRType*)originalElementType);
                                 builder.emitStore(var, unpackedVal);
                                 use->set(var);
                                 builder.setInsertAfter(user);
                                 auto newVal = builder.emitLoad(var);
-                                auto packedVal = builder.emitCallInst(
-                                    (IRType*)loweredElementTypeInfo.loweredType,
-                                    loweredElementTypeInfo.convertOriginalToLowered,
-                                    1,
-                                    &newVal);
+                                auto packedVal =
+                                    loweredElementTypeInfo.convertOriginalToLowered.apply(
+                                        builder,
+                                        (IRType*)loweredElementTypeInfo.loweredType,
+                                        newVal);
                                 builder.emitStore(ptrVal, packedVal);
                             }
                             break;
@@ -1148,7 +1307,7 @@ struct LoweredElementTypeContext
 void lowerBufferElementTypeToStorageType(
     TargetProgram* target,
     IRModule* module,
-    bool lowerBufferPointer)
+    BufferElementTypeLoweringOptions options)
 {
     SlangMatrixLayoutMode defaultMatrixMode =
         (SlangMatrixLayoutMode)target->getOptionSet().getMatrixLayoutMode();
@@ -1157,7 +1316,7 @@ void lowerBufferElementTypeToStorageType(
         defaultMatrixMode = SLANG_MATRIX_LAYOUT_ROW_MAJOR;
     else if (defaultMatrixMode == SLANG_MATRIX_LAYOUT_MODE_UNKNOWN)
         defaultMatrixMode = SLANG_MATRIX_LAYOUT_ROW_MAJOR;
-    LoweredElementTypeContext context(target, lowerBufferPointer, defaultMatrixMode);
+    LoweredElementTypeContext context(target, options, defaultMatrixMode);
     context.processModule(module);
 }
 
diff --git a/source/slang/slang-ir-lower-buffer-element-type.h b/source/slang/slang-ir-lower-buffer-element-type.h
index d6082798f..2c69c5476 100644
--- a/source/slang/slang-ir-lower-buffer-element-type.h
+++ b/source/slang/slang-ir-lower-buffer-element-type.h
@@ -8,6 +8,14 @@ class TargetProgram;
 struct IRTypeLayoutRules;
 struct IRType;
 
+struct BufferElementTypeLoweringOptions
+{
+    bool lowerBufferPointer = false;
+
+    // For WGSL, we can only create arrays that has a stride of 16 bytes for constant buffers.
+    bool use16ByteArrayElementForConstantBuffer = false;
+};
+
 // For each struct type S used as element type of a ConstantBuffer, ParameterBlock or
 // [RW]StructuredBuffer, we create a lowered type L, where matrix types are lowered to arrays of
 // vectors based on major-ness, and loads from the buffer are converted to L_to_S(load(buffer)), and
@@ -18,7 +26,7 @@ struct IRType;
 void lowerBufferElementTypeToStorageType(
     TargetProgram* target,
     IRModule* module,
-    bool lowerBufferPointer = false);
+    BufferElementTypeLoweringOptions options = BufferElementTypeLoweringOptions());
 
 
 // Returns the type layout rules should be used for a buffer resource type.
diff --git a/source/slang/slang-ir-spirv-legalize.cpp b/source/slang/slang-ir-spirv-legalize.cpp
index ff1ddadca..4baa28d67 100644
--- a/source/slang/slang-ir-spirv-legalize.cpp
+++ b/source/slang/slang-ir-spirv-legalize.cpp
@@ -2205,7 +2205,12 @@ struct SPIRVLegalizationContext : public SourceEmitterBase
         // pointers in this pass. In the future we should consider separate out IRAddress as
         // the type for IRVar, and use IRPtrType to dedicate pointers in user code, so we can
         // safely lower the pointer load stores early together with other buffer types.
-        lowerBufferElementTypeToStorageType(m_sharedContext->m_targetProgram, m_module, true);
+        BufferElementTypeLoweringOptions bufferElementTypeLoweringOptions;
+        bufferElementTypeLoweringOptions.lowerBufferPointer = true;
+        lowerBufferElementTypeToStorageType(
+            m_sharedContext->m_targetProgram,
+            m_module,
+            bufferElementTypeLoweringOptions);
 
         // The above step may produce empty struct types, so we need to lower them out of existence.
         legalizeEmptyTypes(m_sharedContext->m_targetProgram, m_module, m_sink);
diff --git a/source/slang/slang-ir.cpp b/source/slang/slang-ir.cpp
index 2cbafea6c..823b3cd7d 100644
--- a/source/slang/slang-ir.cpp
+++ b/source/slang/slang-ir.cpp
@@ -2264,6 +2264,11 @@ IRInst* IRBuilder::getBoolValue(bool inValue)
     return _findOrEmitConstant(keyInst);
 }
 
+IRInst* IRBuilder::getIntValue(IRIntegerValue value)
+{
+    return getIntValue(getIntType(), value);
+}
+
 IRInst* IRBuilder::getIntValue(IRType* type, IRIntegerValue inValue)
 {
     IRConstant keyInst;