Dynamic dispatch for generic interface requirements.

-Lower interfaces into actual `IRInterfaceType` insts.
-Lower `DeclRef<AssocTypeDecl>` into `IRAssociatedType`
-Generate proper IRType for generic functions.
-Add a test case exercising dynamic dispatching a generic static function through an associated type.
-Bug fixes for the test case.

1 files changed, 173 insertions, 8 deletions

diff --git a/source/slang/slang-ir-lower-generics.cpp b/source/slang/slang-ir-lower-generics.cpp
index f6340a633..fe0fa3364 100644
--- a/source/slang/slang-ir-lower-generics.cpp
+++ b/source/slang/slang-ir-lower-generics.cpp
@@ -16,6 +16,7 @@ namespace Slang
         IRModule* module;
 
         Dictionary<IRInst*, IRInst*> loweredGenericFunctions;
+        HashSet<IRInterfaceType*> loweredInterfaceTypes;
 
         SharedIRBuilder sharedBuilderStorage;
 
@@ -45,6 +46,20 @@ namespace Slang
             workListSet.Add(inst);
         }
 
+        bool isPolymorphicType(IRInst* typeInst)
+        {
+            if (as<IRParam>(typeInst) && as<IRTypeType>(typeInst->getFullType()))
+                return true;
+            switch (typeInst->op)
+            {
+            case kIROp_AssociatedType:
+            case kIROp_InterfaceType:
+                return true;
+            default:
+                return false;
+            }
+        }
+
         IRInst* lowerGenericFunction(IRInst* genericValue)
         {
             IRInst* result = nullptr;
@@ -64,6 +79,7 @@ namespace Slang
             builder.sharedBuilder = &sharedBuilderStorage;
             builder.setInsertBefore(genericParent);
             auto loweredFunc = cloneInstAndOperands(&cloneEnv, &builder, func);
+            loweredFunc->setFullType(lowerGenericFuncType(&builder, cast<IRGeneric>(genericParent->typeUse.get())));
             List<IRInst*> clonedParams;
             for (auto genericParam : genericParent->getParams())
             {
@@ -82,7 +98,7 @@ namespace Slang
             // Turn generic parameters into void pointers.
             for (auto param : cast<IRFunc>(loweredFunc)->getParams())
             {
-                if (param->findDecoration<IRPolymorphicDecoration>())
+                if (isPolymorphicType(param->getFullType()))
                 {
                     param->setFullType(builder.getPtrType(builder.getVoidType()));
                 }
@@ -91,6 +107,106 @@ namespace Slang
             return loweredFunc;
         }
 
+        IRType* lowerGenericFuncType(IRBuilder* builder, IRGeneric* genericVal)
+        {
+            List<IRInst*> genericParamTypes;
+            for (auto genericParam : genericVal->getParams())
+            {
+                if (isPolymorphicType(genericParam->getFullType()))
+                {
+                    genericParamTypes.add(builder->getPtrType(builder->getVoidType()));
+                }
+                else
+                {
+                    genericParamTypes.add(genericParam->getFullType());
+                }
+            }
+
+            auto innerType = (IRFuncType*)lowerFuncType(
+                builder,
+                cast<IRFuncType>(findGenericReturnVal(genericVal)),
+                genericParamTypes.getCount());
+
+            for (int i = 0; i < genericParamTypes.getCount(); i++)
+            {
+                innerType->setOperand(
+                    innerType->getOperandCount() - genericParamTypes.getCount() + i,
+                    genericParamTypes[i]);
+            }
+
+            return innerType;
+        }
+
+        IRType* lowerFuncType(IRBuilder* builder, IRFuncType* funcType, UInt additionalParamCount = 0)
+        {
+            List<IRInst*> newOperands;
+            bool translated = false;
+            for (UInt i = 0; i < funcType->getOperandCount(); i++)
+            {
+                auto paramType = funcType->getOperand(i);
+                if (isPolymorphicType(paramType))
+                {
+                    newOperands.add(builder->getPtrType(builder->getVoidType()));
+                    translated = true;
+                }
+                else if (paramType->op == kIROp_Specialize)
+                {
+                    // TODO: handle static specialized type here.
+                    // For now treat all specialized types as dynamic.
+                    // In the future, we need to turn things like Array<IDynamic> into Array<void*>.
+                    newOperands.add(builder->getPtrType(builder->getVoidType()));
+                    translated = true;
+                }
+                else
+                {
+                    newOperands.add(paramType);
+                }
+            }
+            if (!translated)
+                return funcType;
+            for (UInt i = 0; i < additionalParamCount; i++)
+            {
+                newOperands.add(nullptr);
+            }
+            auto newFuncType = builder->getFuncType(
+                newOperands.getCount() - 1,
+                (IRType**)(newOperands.begin() + 1),
+                (IRType*)newOperands[0]);
+
+            IRCloneEnv cloneEnv;
+            cloneInstDecorationsAndChildren(&cloneEnv, &sharedBuilderStorage, funcType, newFuncType);
+            return newFuncType;
+        }
+
+        IRInterfaceType* maybeLowerInterfaceType(IRInterfaceType* interfaceType)
+        {
+            if (loweredInterfaceTypes.Contains(interfaceType))
+                return interfaceType;
+
+            IRBuilder builder;
+            builder.sharedBuilder = &sharedBuilderStorage;
+            builder.setInsertBefore(interfaceType);
+
+            // Translate IRFuncType in interface requirements.
+            for (UInt i = 0; i < interfaceType->getOperandCount(); i++)
+            {
+                if (auto entry = as<IRInterfaceRequirementEntry>(interfaceType->getOperand(i)))
+                {
+                    if (auto funcType = as<IRFuncType>(entry->getRequirementVal()))
+                    {
+                        entry->requirementVal.set(lowerFuncType(&builder, funcType));
+                    }
+                    else if (auto genericFuncType = as<IRGeneric>(entry->getRequirementVal()))
+                    {
+                        entry->requirementVal.set(lowerGenericFuncType(&builder, genericFuncType));
+                    }
+                }
+            }
+
+            loweredInterfaceTypes.Add(interfaceType);
+            return interfaceType;
+        }
+
         void processInst(IRInst* inst)
         {
             if (auto callInst = as<IRCall>(inst))
@@ -98,25 +214,53 @@ namespace Slang
                 // If we see a call(specialize(gFunc, Targs), args),
                 // translate it into call(gFunc, args, Targs).
                 auto funcOperand = callInst->getOperand(0);
+                IRInst* loweredFunc = nullptr;
                 if (auto specializeInst = as<IRSpecialize>(funcOperand))
                 {
-                    auto loweredFunc = lowerGenericFunction(specializeInst->getOperand(0));
-                    if (loweredFunc == specializeInst->getOperand(0))
+                    auto funcToSpecialize = specializeInst->getOperand(0);
+                    List<IRType*> paramTypes;
+                    if (auto interfaceLookup = as<IRLookupWitnessMethod>(funcToSpecialize))
                     {
-                        // This is an intrinsic function, don't transform.
-                        return;
+                        // The callee is a result of witness table lookup, we will only
+                        // translate the call.
+                        IRInst* callee = nullptr;
+                        auto interfaceType = maybeLowerInterfaceType(cast<IRInterfaceType>(interfaceLookup->getInterfaceType()));
+                        for (UInt i = 0; i < interfaceType->getOperandCount(); i++)
+                        {
+                            auto entry = cast<IRInterfaceRequirementEntry>(interfaceType->getOperand(i));
+                            if (entry->getRequirementKey() == interfaceLookup->getOperand(1))
+                            {
+                                callee = entry->getRequirementVal();
+                                break;
+                            }
+                        }
+                        auto funcType = cast<IRFuncType>(callee);
+                        for (UInt i = 0; i < funcType->getParamCount(); i++)
+                            paramTypes.add(funcType->getParamType(i));
+                        loweredFunc = funcToSpecialize;
+                    }
+                    else
+                    {
+                        loweredFunc = lowerGenericFunction(specializeInst->getOperand(0));
+                        if (loweredFunc == specializeInst->getOperand(0))
+                        {
+                            // This is an intrinsic function, don't transform.
+                            return;
+                        }
+                        for (auto param : as<IRFunc>(loweredFunc)->getParams())
+                            paramTypes.add(param->getDataType());
                     }
+
                     IRBuilder builderStorage;
                     auto builder = &builderStorage;
                     builder->sharedBuilder = &sharedBuilderStorage;
                     builder->setInsertBefore(inst);
                     List<IRInst*> args;
-                    auto pp = as<IRFunc>(loweredFunc)->getParams().begin();
                     auto voidPtrType = builder->getPtrType(builder->getVoidType());
                     for (UInt i = 0; i < callInst->getArgCount(); i++)
                     {
                         auto arg = callInst->getArg(i);
-                        if ((*pp)->getDataType() == voidPtrType &&
+                        if (paramTypes[i] == voidPtrType &&
                             arg->getDataType() != voidPtrType)
                         {
                             // We are calling a generic function that with an argument of
@@ -132,7 +276,6 @@ namespace Slang
                                 arg);
                         }
                         args.add(arg);
-                        ++pp;
                     }
                     for (UInt i = 0; i < specializeInst->getArgCount(); i++)
                         args.add(specializeInst->getArg(i));
@@ -141,6 +284,28 @@ namespace Slang
                     callInst->removeAndDeallocate();
                 }
             }
+            else if (auto witnessTable = as<IRWitnessTable>(inst))
+            {
+                // Lower generic functions in witness table.
+                for (auto child : witnessTable->getChildren())
+                {
+                    auto entry = as<IRWitnessTableEntry>(child);
+                    if (!entry)
+                        continue;
+                    if (auto genericVal = as<IRGeneric>(entry->getSatisfyingVal()))
+                    {
+                        if (findGenericReturnVal(genericVal)->op == kIROp_Func)
+                        {
+                            auto loweredFunc = lowerGenericFunction(genericVal);
+                            entry->satisfyingVal.set(loweredFunc);
+                        }
+                    }
+                }
+            }
+            else if (auto interfaceType = as<IRInterfaceType>(inst))
+            {
+                maybeLowerInterfaceType(interfaceType);
+            }
         }
 
         void processModule()