`is` and `as` operator and `Optional<T>`. (#2355)

* `is` and `as` operator and `Optional<T>`.

* Fix.

Co-authored-by: Yong He <yhe@nvidia.com>

1 files changed, 239 insertions, 0 deletions

diff --git a/source/slang/slang-ir-lower-optional-type.cpp b/source/slang/slang-ir-lower-optional-type.cpp
new file mode 100644
index 000000000..79be4e042
--- /dev/null
+++ b/source/slang/slang-ir-lower-optional-type.cpp
@@ -0,0 +1,239 @@
+// slang-ir-lower-optional-type.cpp
+
+#include "slang-ir-lower-optional-type.h"
+#include "slang-ir.h"
+#include "slang-ir-insts.h"
+
+namespace Slang
+{
+    struct OptionalTypeLoweringContext
+    {
+        IRModule* module;
+        DiagnosticSink* sink;
+
+        SharedIRBuilder sharedBuilderStorage;
+
+        List<IRInst*> workList;
+        HashSet<IRInst*> workListSet;
+
+        struct LoweredOptionalTypeInfo : public RefObject
+        {
+            IRType* optionalType = nullptr;
+            IRType* valueType = nullptr;
+            IRType* loweredType = nullptr;
+            IRStructField* valueField = nullptr;
+            IRStructField* hasValueField = nullptr;
+        };
+        Dictionary<IRInst*, RefPtr<LoweredOptionalTypeInfo>> mapLoweredTypeToOptionalTypeInfo;
+        Dictionary<IRInst*, RefPtr<LoweredOptionalTypeInfo>> loweredOptionalTypes;
+
+        IRType* maybeLowerOptionalType(IRBuilder* builder, IRType* type)
+        {
+            if (auto info = getLoweredOptionalType(builder, type))
+                return info->loweredType;
+            else
+                return type;
+        }
+
+        LoweredOptionalTypeInfo* getLoweredOptionalType(IRBuilder* builder, IRInst* type)
+        {
+            if (auto loweredInfo = loweredOptionalTypes.TryGetValue(type))
+                return loweredInfo->Ptr();
+            if (auto loweredInfo = mapLoweredTypeToOptionalTypeInfo.TryGetValue(type))
+                return loweredInfo->Ptr();
+
+            if (!type)
+                return nullptr;
+            if (type->getOp() != kIROp_OptionalType)
+                return nullptr;
+
+            RefPtr<LoweredOptionalTypeInfo> info = new LoweredOptionalTypeInfo();
+            info->optionalType = (IRType*)type;
+            auto optionalType = cast<IROptionalType>(type);
+            auto valueType = optionalType->getValueType();
+            info->valueType = valueType;
+
+            auto structType = builder->createStructType();
+            info->loweredType = structType;
+            builder->addNameHintDecoration(structType, UnownedStringSlice("OptionalType"));
+
+            info->valueType = valueType;
+            auto valueKey = builder->createStructKey();
+            builder->addNameHintDecoration(valueKey, UnownedStringSlice("value"));
+            info->valueField = builder->createStructField(structType, valueKey, (IRType*)valueType);
+
+            auto boolType = builder->getBoolType();
+            auto hasValueKey = builder->createStructKey();
+            builder->addNameHintDecoration(hasValueKey, UnownedStringSlice("hasValue"));
+            info->hasValueField = builder->createStructField(structType, hasValueKey, (IRType*)boolType);
+
+            mapLoweredTypeToOptionalTypeInfo[info->loweredType] = info;
+            loweredOptionalTypes[type] = info;
+            return info.Ptr();
+        }
+
+        void addToWorkList(
+            IRInst* inst)
+        {
+            for (auto ii = inst->getParent(); ii; ii = ii->getParent())
+            {
+                if (as<IRGeneric>(ii))
+                    return;
+            }
+
+            if (workListSet.Contains(inst))
+                return;
+
+            workList.add(inst);
+            workListSet.Add(inst);
+        }
+
+        void processMakeOptionalValue(IRMakeOptionalValue* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto info = getLoweredOptionalType(builder, inst->getDataType());
+            List<IRInst*> operands;
+            operands.add(inst->getOperand(0));
+            operands.add(builder->getBoolValue(true));
+            auto makeStruct = builder->emitMakeStruct(info->loweredType, operands);
+            inst->replaceUsesWith(makeStruct);
+            inst->removeAndDeallocate();
+        }
+
+        void processMakeOptionalNone(IRMakeOptionalNone* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto info = getLoweredOptionalType(builder, inst->getDataType());
+
+            List<IRInst*> operands;
+            operands.add(inst->getDefaultValue());
+            operands.add(builder->getBoolValue(false));
+            auto makeStruct = builder->emitMakeStruct(info->loweredType, operands);
+            inst->replaceUsesWith(makeStruct);
+            inst->removeAndDeallocate();
+        }
+
+        IRInst* getOptionalHasValue(IRBuilder* builder, IRInst* optionalInst)
+        {
+            auto loweredOptionalTypeInfo = getLoweredOptionalType(builder, optionalInst->getDataType());
+            SLANG_ASSERT(loweredOptionalTypeInfo);
+
+            auto value = builder->emitFieldExtract(
+                builder->getBoolType(),
+                optionalInst,
+                loweredOptionalTypeInfo->hasValueField->getKey());
+            return value;
+        }
+
+        void processGetOptionalHasValue(IROptionalHasValue* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto optionalValue = inst->getOptionalOperand();
+            auto hasVal = getOptionalHasValue(builder, optionalValue);
+            inst->replaceUsesWith(hasVal);
+            inst->removeAndDeallocate();
+        }
+
+        void processGetOptionalValue(IRGetOptionalValue* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto base = inst->getOptionalOperand();
+            auto loweredOptionalTypeInfo = getLoweredOptionalType(builder, base->getDataType());
+            SLANG_ASSERT(loweredOptionalTypeInfo);
+            SLANG_ASSERT(loweredOptionalTypeInfo->valueField);
+            auto getElement = builder->emitFieldExtract(
+                loweredOptionalTypeInfo->valueType,
+                base,
+                loweredOptionalTypeInfo->valueField->getKey());
+            inst->replaceUsesWith(getElement);
+            inst->removeAndDeallocate();
+        }
+
+        void processOptionalType(IROptionalType* inst)
+        {
+            IRBuilder builderStorage(sharedBuilderStorage);
+            auto builder = &builderStorage;
+            builder->setInsertBefore(inst);
+
+            auto loweredOptionalTypeInfo = getLoweredOptionalType(builder, inst);
+            SLANG_ASSERT(loweredOptionalTypeInfo);
+            SLANG_UNUSED(loweredOptionalTypeInfo);
+        }
+
+        void processInst(IRInst* inst)
+        {
+            switch (inst->getOp())
+            {
+            case kIROp_MakeOptionalValue:
+                processMakeOptionalValue((IRMakeOptionalValue*)inst);
+                break;
+            case kIROp_MakeOptionalNone:
+                processMakeOptionalNone((IRMakeOptionalNone*)inst);
+                break;
+            case kIROp_OptionalHasValue:
+                processGetOptionalHasValue((IROptionalHasValue*)inst);
+                break;
+            case kIROp_GetOptionalValue:
+                processGetOptionalValue((IRGetOptionalValue*)inst);
+                break;
+            case kIROp_OptionalType:
+                processOptionalType((IROptionalType*)inst);
+                break;
+            default:
+                break;
+            }
+        }
+
+        void processModule()
+        {
+            SharedIRBuilder* sharedBuilder = &sharedBuilderStorage;
+            sharedBuilder->init(module);
+
+            // Deduplicate equivalent types.
+            sharedBuilder->deduplicateAndRebuildGlobalNumberingMap();
+
+            addToWorkList(module->getModuleInst());
+
+            while (workList.getCount() != 0)
+            {
+                IRInst* inst = workList.getLast();
+
+                workList.removeLast();
+                workListSet.Remove(inst);
+
+                processInst(inst);
+
+                for (auto child = inst->getLastChild(); child; child = child->getPrevInst())
+                {
+                    addToWorkList(child);
+                }
+            }
+
+            // Replace all optional types with lowered struct types.
+            for (auto kv : loweredOptionalTypes)
+            {
+                kv.Key->replaceUsesWith(kv.Value->loweredType);
+            }
+        }
+    };
+    
+    void lowerOptionalType(IRModule* module, DiagnosticSink* sink)
+    {
+        OptionalTypeLoweringContext context;
+        context.module = module;
+        context.sink = sink;
+        context.processModule();
+    }
+}