Lower throwing COM interface method. (#2282)

* Lower throwing COM interface method.

* Fix.

* Fix warnings.

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

18 files changed, 708 insertions, 94 deletions

diff --git a/build/visual-studio/slang/slang.vcxproj b/build/visual-studio/slang/slang.vcxproj
index 42cb2f003..f9a76211a 100644
--- a/build/visual-studio/slang/slang.vcxproj
+++ b/build/visual-studio/slang/slang.vcxproj
@@ -363,12 +363,14 @@ IF EXIST ..\..\..\external\slang-binaries\bin\windows-aarch64\slang-glslang.dll\
     <ClInclude Include="..\..\..\source\slang\slang-ir-hoist-local-types.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-inline.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-inst-defs.h" />

+    <ClInclude Include="..\..\..\source\slang\slang-ir-inst-pass-base.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-insts.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-layout.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-legalize-varying-params.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-link.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-liveness.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-bit-cast.h" />

+    <ClInclude Include="..\..\..\source\slang\slang-ir-lower-com-methods.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-error-handling.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-existential.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-generic-call.h" />

@@ -378,9 +380,11 @@ IF EXIST ..\..\..\external\slang-binaries\bin\windows-aarch64\slang-glslang.dll\
     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-reinterpret.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-result-type.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-tuple-types.h" />

+    <ClInclude Include="..\..\..\source\slang\slang-ir-marshal-native-call.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-metadata.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-missing-return.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-optix-entry-point-uniforms.h" />

+    <ClInclude Include="..\..\..\source\slang\slang-ir-peephole.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-restructure-scoping.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-restructure.h" />

     <ClInclude Include="..\..\..\source\slang\slang-ir-sccp.h" />

@@ -519,6 +523,7 @@ IF EXIST ..\..\..\external\slang-binaries\bin\windows-aarch64\slang-glslang.dll\
     <ClCompile Include="..\..\..\source\slang\slang-ir-link.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-liveness.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-bit-cast.cpp" />

+    <ClCompile Include="..\..\..\source\slang\slang-ir-lower-com-methods.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-error-handling.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-existential.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-generic-call.cpp" />

@@ -528,9 +533,11 @@ IF EXIST ..\..\..\external\slang-binaries\bin\windows-aarch64\slang-glslang.dll\
     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-reinterpret.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-result-type.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-tuple-types.cpp" />

+    <ClCompile Include="..\..\..\source\slang\slang-ir-marshal-native-call.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-metadata.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-missing-return.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-optix-entry-point-uniforms.cpp" />

+    <ClCompile Include="..\..\..\source\slang\slang-ir-peephole.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-restructure-scoping.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-restructure.cpp" />

     <ClCompile Include="..\..\..\source\slang\slang-ir-sccp.cpp" />

diff --git a/build/visual-studio/slang/slang.vcxproj.filters b/build/visual-studio/slang/slang.vcxproj.filters
index ab0046185..3b07a8ef5 100644
--- a/build/visual-studio/slang/slang.vcxproj.filters
+++ b/build/visual-studio/slang/slang.vcxproj.filters
@@ -186,6 +186,9 @@
     <ClInclude Include="..\..\..\source\slang\slang-ir-inst-defs.h">

       <Filter>Header Files</Filter>

     </ClInclude>

+    <ClInclude Include="..\..\..\source\slang\slang-ir-inst-pass-base.h">

+      <Filter>Header Files</Filter>

+    </ClInclude>

     <ClInclude Include="..\..\..\source\slang\slang-ir-insts.h">

       <Filter>Header Files</Filter>

     </ClInclude>

@@ -204,6 +207,9 @@
     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-bit-cast.h">

       <Filter>Header Files</Filter>

     </ClInclude>

+    <ClInclude Include="..\..\..\source\slang\slang-ir-lower-com-methods.h">

+      <Filter>Header Files</Filter>

+    </ClInclude>

     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-error-handling.h">

       <Filter>Header Files</Filter>

     </ClInclude>

@@ -231,6 +237,9 @@
     <ClInclude Include="..\..\..\source\slang\slang-ir-lower-tuple-types.h">

       <Filter>Header Files</Filter>

     </ClInclude>

+    <ClInclude Include="..\..\..\source\slang\slang-ir-marshal-native-call.h">

+      <Filter>Header Files</Filter>

+    </ClInclude>

     <ClInclude Include="..\..\..\source\slang\slang-ir-metadata.h">

       <Filter>Header Files</Filter>

     </ClInclude>

@@ -240,6 +249,9 @@
     <ClInclude Include="..\..\..\source\slang\slang-ir-optix-entry-point-uniforms.h">

       <Filter>Header Files</Filter>

     </ClInclude>

+    <ClInclude Include="..\..\..\source\slang\slang-ir-peephole.h">

+      <Filter>Header Files</Filter>

+    </ClInclude>

     <ClInclude Include="..\..\..\source\slang\slang-ir-restructure-scoping.h">

       <Filter>Header Files</Filter>

     </ClInclude>

@@ -650,6 +662,9 @@
     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-bit-cast.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

+    <ClCompile Include="..\..\..\source\slang\slang-ir-lower-com-methods.cpp">

+      <Filter>Source Files</Filter>

+    </ClCompile>

     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-error-handling.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

@@ -677,6 +692,9 @@
     <ClCompile Include="..\..\..\source\slang\slang-ir-lower-tuple-types.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

+    <ClCompile Include="..\..\..\source\slang\slang-ir-marshal-native-call.cpp">

+      <Filter>Source Files</Filter>

+    </ClCompile>

     <ClCompile Include="..\..\..\source\slang\slang-ir-metadata.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

@@ -686,6 +704,9 @@
     <ClCompile Include="..\..\..\source\slang\slang-ir-optix-entry-point-uniforms.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

+    <ClCompile Include="..\..\..\source\slang\slang-ir-peephole.cpp">

+      <Filter>Source Files</Filter>

+    </ClCompile>

     <ClCompile Include="..\..\..\source\slang\slang-ir-restructure-scoping.cpp">

       <Filter>Source Files</Filter>

     </ClCompile>

diff --git a/source/slang/slang-emit-c-like.cpp b/source/slang/slang-emit-c-like.cpp
index e0b1a44f2..10ac2ca84 100644
--- a/source/slang/slang-emit-c-like.cpp
+++ b/source/slang/slang-emit-c-like.cpp
@@ -1810,6 +1810,22 @@ void CLikeSourceEmitter::defaultEmitInstExpr(IRInst* inst, const EmitOpInfo& inO
         m_writer->emit("GroupMemoryBarrierWithGroupSync()");
         break;
 
+    case kIROp_getNativeStr:
+        {
+            auto prec = getInfo(EmitOp::Postfix);
+            needClose = maybeEmitParens(outerPrec, prec);
+            emitOperand(inst->getOperand(0), leftSide(outerPrec, prec));
+            m_writer->emit("->getBuffer()");
+            break;
+        }
+    case kIROp_makeString:
+        {
+            m_writer->emit("String(");
+            emitOperand(inst->getOperand(0), EmitOpInfo());
+            m_writer->emit(")");
+            break;
+        }
+
     case kIROp_getElement:
     case kIROp_getElementPtr:
     case kIROp_ImageSubscript:
diff --git a/source/slang/slang-emit.cpp b/source/slang/slang-emit.cpp
index 0bb1d73e5..fb0f65c5f 100644
--- a/source/slang/slang-emit.cpp
+++ b/source/slang/slang-emit.cpp
@@ -206,12 +206,6 @@ Result linkAndOptimizeIR(
     switch (target)
     {
         case CodeGenTarget::CPPSource:
-        {
-            // TODO(JS):
-            // We want the interface transformation to take place for 'regular' CPPSource for now too.
-            lowerComInterfaces(irModule, artifactDesc.style, sink);
-            break;
-        }
         case CodeGenTarget::HostCPPSource:
         {
             lowerComInterfaces(irModule, artifactDesc.style, sink);
diff --git a/source/slang/slang-ir-com-interface.cpp b/source/slang/slang-ir-com-interface.cpp
index 899596209..d9d54d9d2 100644
--- a/source/slang/slang-ir-com-interface.cpp
+++ b/source/slang/slang-ir-com-interface.cpp
@@ -3,6 +3,7 @@
 
 #include "slang-ir.h"
 #include "slang-ir-insts.h"
+#include "slang-ir-lower-com-methods.h"
 
 namespace Slang
 {
@@ -38,7 +39,8 @@ static bool _canReplace(IRUse* use)
 
 void lowerComInterfaces(IRModule* module, ArtifactStyle artifactStyle, DiagnosticSink* sink)
 {
-    SLANG_UNUSED(sink);
+    // First, lower all COM methods and their call sites out of `Result` and other managed types.
+    lowerComMethods(module, sink);
 
     // Find all of the COM interfaces
     List<IRInterfaceType*> comInterfaces;
diff --git a/source/slang/slang-ir-dll-import.cpp b/source/slang/slang-ir-dll-import.cpp
index 02743cba4..b123dfb03 100644
--- a/source/slang/slang-ir-dll-import.cpp
+++ b/source/slang/slang-ir-dll-import.cpp
@@ -3,6 +3,7 @@
 
 #include "slang-ir.h"
 #include "slang-ir-insts.h"
+#include "slang-ir-marshal-native-call.h"
 
 namespace Slang
 {
@@ -83,82 +84,15 @@ struct DllImportContext
         return stringGetBufferFunc;
     }
 
-    IRType* getNativeType(IRBuilder& builder, IRType* type)
-    {
-        switch (type->getOp())
-        {
-        case kIROp_StringType:
-            return builder.getPtrType(builder.getCharType());
-        default:
-            return type;
-        }
-    }
-
-    IRType* getNativeFuncType(IRBuilder& builder, IRFunc* func)
-    {
-        List<IRInst*> nativeParamTypes;
-        auto declaredFuncType = func->getDataType();
-        assert(declaredFuncType->getOp() == kIROp_FuncType);
-        for (UInt i = 0; i < declaredFuncType->getParamCount(); ++i)
-        {
-            auto paramType = declaredFuncType->getParamType(i);
-            nativeParamTypes.add(getNativeType(builder, as<IRType>(paramType)));
-        }
-        IRType* returnType = getNativeType(builder, func->getResultType());
-        auto funcType = builder.getFuncType(
-            nativeParamTypes.getCount(), (IRType**)nativeParamTypes.getBuffer(), returnType);
-
-        return funcType;
-    }
-
-    void marshalImportRefParameter(IRBuilder& builder, IRParam* param, List<IRInst*>& args)
-    {
-        SLANG_UNUSED(builder);
-
-        auto innerType = as<IRPtrTypeBase>(param->getDataType())->getValueType();
-        switch (innerType->getOp())
-        {
-        case kIROp_StringType:
-            {
-                diagnosticSink->diagnose(
-                    param->sourceLoc,
-                    Diagnostics::invalidTypeMarshallingForImportedDLLSymbol,
-                    param->getParent()->getParent());
-            }
-            break;
-        default:
-            args.add(param);
-            break;
-        }
-    }
-
-    void marshalImportParameter(IRBuilder& builder, IRParam* param, List<IRInst*>& args)
-    {
-        switch (param->getDataType()->getOp())
-        {
-        case kIROp_InOutType:
-        case kIROp_RefType:
-            return marshalImportRefParameter(builder, param, args);
-        case kIROp_StringType:
-            {
-                auto getStringBufferFunc = getStringGetBufferFunc();
-                args.add(builder.emitCallInst(
-                    builder.getPtrType(builder.getCharType()), getStringBufferFunc, 1, (IRInst**)&param));
-            }
-            break;
-        default:
-            args.add(param);
-            break;
-        }
-    }
 
     void processFunc(IRFunc* func, IRDllImportDecoration* dllImportDecoration)
     {
         assert(func->getFirstBlock() == nullptr);
 
         IRBuilder builder(sharedBuilder);
+        NativeCallMarshallingContext marshalContext;
 
-        auto nativeType = getNativeFuncType(builder, func);
+        auto nativeType = marshalContext.getNativeFuncType(builder, func->getDataType());
         builder.setInsertInto(module->getModuleInst());
         auto funcPtr = builder.createGlobalVar(nativeType);
         builder.setInsertInto(funcPtr);
@@ -178,12 +112,6 @@ struct DllImportContext
             params.add(builder.emitParam((IRType*)paramType));
         }
 
-        // Marshal parameters to arguments into native func.
-        List<IRInst*> args;
-        for (auto param : params)
-        {
-            marshalImportParameter(builder, param, args);
-        }
         IRInst* cmpArgs[] = {builder.emitLoad(nativeType, funcPtr), builder.getPtrValue(nullptr)};
         auto isUninitialized =
             builder.emitIntrinsicInst(builder.getBoolType(), kIROp_Eql, 2, cmpArgs);
@@ -209,17 +137,15 @@ struct DllImportContext
         builder.emitBranch(afterBlock);
         builder.setInsertInto(afterBlock);
 
-        IRType* nativeReturnType = getNativeType(builder, func->getResultType());
-        auto nativeFunc = builder.emitLoad(funcPtr);
-        auto call = builder.emitCallInst(nativeReturnType, nativeFunc, args);
-        if (declaredFuncType->getResultType()->getOp() != kIROp_VoidType)
-        {
-            builder.emitReturn(call);
-        }
-        else
-        {
-            builder.emitReturn();
-        }
+        marshalContext.diagnosticSink = diagnosticSink;
+        auto callResult = marshalContext.marshalNativeCall(
+            builder,
+            declaredFuncType,
+            nativeType,
+            builder.emitLoad(funcPtr),
+            params.getCount(),
+            (IRInst**)params.getBuffer());
+        builder.emitReturn(callResult);
     }
 
     void processModule()
diff --git a/source/slang/slang-ir-inst-defs.h b/source/slang/slang-ir-inst-defs.h
index 4d927bdaf..c10ae8639 100644
--- a/source/slang/slang-ir-inst-defs.h
+++ b/source/slang/slang-ir-inst-defs.h
@@ -308,6 +308,12 @@ INST(getElement, getElement, 2, 0)
 INST(getElementPtr, getElementPtr, 2, 0)
 INST(getAddr, getAddr, 1, 0)
 
+// Get an unowned NativeString from a String.
+INST(getNativeStr, getNativeStr, 1, 0)
+
+// Make String from a NativeString.
+INST(makeString, makeString, 1, 0)
+
 // "Subscript" an image at a pixel coordinate to get pointer
 INST(ImageSubscript, imageSubscript, 2, 0)
 
diff --git a/source/slang/slang-ir-inst-pass-base.h b/source/slang/slang-ir-inst-pass-base.h
new file mode 100644
index 000000000..ec4506272
--- /dev/null
+++ b/source/slang/slang-ir-inst-pass-base.h
@@ -0,0 +1,83 @@
+// slang-ir-inst-pass-base.h
+#pragma once
+
+#include "slang-ir.h"
+#include "slang-ir-insts.h"
+
+namespace Slang
+{
+    struct IRModule;
+
+    class InstPassBase
+    {
+    protected:
+        IRModule* module;
+        SharedIRBuilder sharedBuilderStorage;
+
+        List<IRInst*> workList;
+        HashSet<IRInst*> workListSet;
+        void addToWorkList(IRInst* inst)
+        {
+            if (workListSet.Contains(inst))
+                return;
+
+            workList.add(inst);
+            workListSet.Add(inst);
+        }
+
+    public:
+        InstPassBase(IRModule* inModule)
+            : module(inModule)
+        {}
+
+        template <typename InstType, typename Func>
+        void processInstsOfType(IROp instOp, const Func& f)
+        {
+            workList.clear();
+            workListSet.Clear();
+
+            addToWorkList(module->getModuleInst());
+
+            while (workList.getCount() != 0)
+            {
+                IRInst* inst = workList.getLast();
+
+                workList.removeLast();
+                workListSet.Remove(inst);
+                if (inst->getOp() == instOp)
+                {
+                    f(as<InstType>(inst));
+                }
+
+                for (auto child = inst->getLastChild(); child; child = child->getPrevInst())
+                {
+                    addToWorkList(child);
+                }
+            }
+        }
+
+        template <typename Func>
+        void processAllInsts(const Func& f)
+        {
+            workList.clear();
+            workListSet.Clear();
+
+            addToWorkList(module->getModuleInst());
+
+            while (workList.getCount() != 0)
+            {
+                IRInst* inst = workList.getLast();
+
+                workList.removeLast();
+                workListSet.Remove(inst);
+                f(inst);
+
+                for (auto child = inst->getLastChild(); child; child = child->getPrevInst())
+                {
+                    addToWorkList(child);
+                }
+            }
+        }
+    };
+
+}
diff --git a/source/slang/slang-ir-insts.h b/source/slang/slang-ir-insts.h
index 80438504c..081c67d03 100644
--- a/source/slang/slang-ir-insts.h
+++ b/source/slang/slang-ir-insts.h
@@ -2401,6 +2401,10 @@ public:
         return emitMakeTuple(SLANG_COUNT_OF(args), args);
     }
 
+    IRInst* emitMakeString(IRInst* nativeStr);
+
+    IRInst* emitGetNativeString(IRInst* str);
+
     IRInst* emitGetTupleElement(IRType* type, IRInst* tuple, UInt element);
 
     IRInst* emitMakeResultError(IRType* resultType, IRInst* errorVal);
@@ -2687,6 +2691,8 @@ public:
     IRInst* emitBranch(
         IRBlock*    block);
 
+   IRInst* emitBranch(IRBlock* block, Int argCount, IRInst*const* args);
+
     IRInst* emitBreak(
         IRBlock*    target);
 
@@ -2714,6 +2720,16 @@ public:
         IRBlock*    falseBlock,
         IRBlock*    afterBlock);
 
+    // Create basic blocks and insert an `IfElse` inst at current position that jumps into the blocks.
+    // The current insert position is changed to inside `outTrueBlock` after the call.
+    IRInst* emitIfElseWithBlocks(
+        IRInst* val, IRBlock*& outTrueBlock, IRBlock*& outFalseBlock, IRBlock*& outAfterBlock);
+
+    // Create basic blocks and insert an `If` inst at current position that jumps into the blocks.
+    // The current insert position is changed to inside `outTrueBlock` after the call.
+    IRInst* emitIfWithBlocks(
+        IRInst* val, IRBlock*& outTrueBlock, IRBlock*& outAfterBlock);
+
     IRInst* emitLoopTest(
         IRInst*    val,
         IRBlock*    bodyBlock,
@@ -2778,6 +2794,8 @@ public:
     IRInst* emitMul(IRType* type, IRInst* left, IRInst* right);
     IRInst* emitEql(IRInst* left, IRInst* right);
     IRInst* emitNeq(IRInst* left, IRInst* right);
+    IRInst* emitLess(IRInst* left, IRInst* right);
+
     IRInst* emitShr(IRType* type, IRInst* op0, IRInst* op1);
     IRInst* emitShl(IRType* type, IRInst* op0, IRInst* op1);
 
diff --git a/source/slang/slang-ir-lower-com-methods.cpp b/source/slang/slang-ir-lower-com-methods.cpp
new file mode 100644
index 000000000..6c3a3f289
--- /dev/null
+++ b/source/slang/slang-ir-lower-com-methods.cpp
@@ -0,0 +1,138 @@
+// slang-ir-lower-com-methods.cpp
+
+#include "slang-ir-lower-com-methods.h"
+
+#include "slang-ir.h"
+#include "slang-ir-insts.h"
+#include "slang-ir-marshal-native-call.h"
+#include "slang-ir-inst-pass-base.h"
+
+namespace Slang
+{
+
+struct ComMethodLoweringContext : public InstPassBase
+{
+    DiagnosticSink* diagnosticSink = nullptr;
+
+    NativeCallMarshallingContext marshal;
+
+    OrderedHashSet<IRLookupWitnessMethod*> comCallees;
+
+    ComMethodLoweringContext(IRModule* inModule)
+        : InstPassBase(inModule)
+    {}
+
+    void processComCall(IRCall* comCall)
+    {
+        IRBuilder builder(&sharedBuilderStorage);
+        builder.setInsertBefore(comCall);
+        auto callee = as<IRLookupWitnessMethod>(comCall->getCallee());
+        SLANG_ASSERT(callee);
+
+        comCallees.Add(callee);
+        
+        auto calleeType = as<IRFuncType>(comCall->getCallee()->getDataType());
+        SLANG_ASSERT(calleeType);
+
+        auto nativeFuncType = marshal.getNativeFuncType(builder, calleeType);
+        ShortList<IRInst*> args;
+        for (UInt i = 0; i < comCall->getArgCount(); i++)
+            args.add(comCall->getArg(i));
+        auto currentBlock = builder.getBlock();
+        auto nextInst = comCall->getNextInst();
+        auto newResult = marshal.marshalNativeCall(
+            builder,
+            calleeType,
+            nativeFuncType,
+            comCall->getCallee(),
+            args.getCount(),
+            args.getArrayView().getBuffer());
+
+        comCall->replaceUsesWith(newResult);
+        if (builder.getBlock() != currentBlock)
+        {
+            // `marshalNativeCall` may have replaced the original call with branch insts.
+            // If this is the case, we need to move all insts after the original call in the original
+            // basic block to the new basic block.
+            while (nextInst)
+            {
+                auto next = nextInst->getNextInst();
+                nextInst->removeFromParent();
+                nextInst->insertAtEnd(builder.getBlock());
+                nextInst = next;
+            }
+        }
+        comCall->removeAndDeallocate();
+    }
+
+    void processCall(IRCall* inst)
+    {
+        auto funcValue = inst->getOperand(0);
+
+        // Detect if this is a call into a COM interface method.
+        if (funcValue->getOp() == kIROp_lookup_interface_method)
+        {
+            const auto operand0TypeOp = funcValue->getOperand(0)->getDataType();
+            if (auto tableType = as<IRWitnessTableTypeBase>(operand0TypeOp))
+            {
+                if (tableType->getConformanceType()->findDecoration<IRComInterfaceDecoration>())
+                {
+                    processComCall(inst);
+                    return;
+                }
+            }
+        }
+    }
+
+    void processInterfaceType(IRInterfaceType* interfaceType)
+    {
+        if (!interfaceType->findDecoration<IRComInterfaceDecoration>())
+            return;
+        IRBuilder builder(&sharedBuilderStorage);
+        for (UInt i = 0; i < interfaceType->getOperandCount(); i++)
+        {
+            auto entry = as<IRInterfaceRequirementEntry>(interfaceType->getOperand(i));
+            if (!entry)
+                continue;
+            if (auto funcType = as<IRFuncType>(entry->getRequirementVal()))
+            {
+                builder.setInsertBefore(funcType);
+                entry->setRequirementVal(marshal.getNativeFuncType(builder, funcType));
+            }
+        }
+    }
+
+    void processModule()
+    {
+        sharedBuilderStorage.init(module);
+
+        // Deduplicate equivalent types.
+        sharedBuilderStorage.deduplicateAndRebuildGlobalNumberingMap();   
+
+        // Translate all Calls to interface methods.
+        processInstsOfType<IRCall>(kIROp_Call, [this](IRCall* inst) { processCall(inst); });
+
+        // Update functypes of com callees.
+        for (auto callee : comCallees)
+        {
+            IRBuilder builder(&sharedBuilderStorage);
+            builder.setInsertBefore(callee);
+            auto nativeType = marshal.getNativeFuncType(builder, as<IRFuncType>(callee->getDataType()));
+            callee->setFullType(nativeType);
+        }
+
+        // Update func types of COM interfaces.
+        processInstsOfType<IRInterfaceType>(kIROp_InterfaceType, [this](IRInterfaceType* inst) { processInterfaceType(inst); });
+
+    }
+};
+
+void lowerComMethods(IRModule* module, DiagnosticSink* sink)
+{
+    ComMethodLoweringContext context(module);
+    context.diagnosticSink = sink;
+    context.marshal.diagnosticSink = sink;
+
+    return context.processModule();
+}
+}
diff --git a/source/slang/slang-ir-lower-com-methods.h b/source/slang/slang-ir-lower-com-methods.h
new file mode 100644
index 000000000..145d12733
--- /dev/null
+++ b/source/slang/slang-ir-lower-com-methods.h
@@ -0,0 +1,14 @@
+// slang-ir-lower-com-methods.h
+#pragma once
+
+namespace Slang
+{
+
+struct IRModule;
+class DiagnosticSink;
+
+/// Lower the signature of COM interface methods out of types that
+/// cannot appear in a COM interface. For example, String, List, ComPtr, Result all need to be translated.
+void lowerComMethods(IRModule* module, DiagnosticSink* sink);
+
+}
diff --git a/source/slang/slang-ir-lower-result-type.cpp b/source/slang/slang-ir-lower-result-type.cpp
index 7e632241b..21e046849 100644
--- a/source/slang/slang-ir-lower-result-type.cpp
+++ b/source/slang/slang-ir-lower-result-type.cpp
@@ -124,7 +124,7 @@ namespace Slang
             builder->setInsertBefore(inst);
 
             auto info = getLoweredResultType(builder, inst->getDataType());
-            if (info->loweredType->getOp() == kIROp_VoidType)
+            if (info->loweredType->getOp() == kIROp_StructType)
             {
                 List<IRInst*> operands;
                 operands.add(inst->getOperand(0));
diff --git a/source/slang/slang-ir-marshal-native-call.cpp b/source/slang/slang-ir-marshal-native-call.cpp
new file mode 100644
index 000000000..b8e2edb2f
--- /dev/null
+++ b/source/slang/slang-ir-marshal-native-call.cpp
@@ -0,0 +1,149 @@
+// slang-ir-marshal-native-call.h
+#include "slang-ir-marshal-native-call.h"
+#include "slang-ir.h"
+#include "slang-ir-insts.h"
+
+namespace Slang
+{
+
+    IRType* NativeCallMarshallingContext::getNativeType(IRBuilder& builder, IRType* type)
+    {
+        switch (type->getOp())
+        {
+        case kIROp_StringType:
+            return builder.getNativeStringType();
+        default:
+            return type;
+        }
+    }
+
+    IRFuncType* NativeCallMarshallingContext::getNativeFuncType(
+        IRBuilder& builder, IRFuncType* declaredFuncType)
+    {
+        List<IRInst*> nativeParamTypes;
+        assert(declaredFuncType->getOp() == kIROp_FuncType);
+        for (UInt i = 0; i < declaredFuncType->getParamCount(); ++i)
+        {
+            auto paramType = declaredFuncType->getParamType(i);
+            nativeParamTypes.add(getNativeType(builder, as<IRType>(paramType)));
+        }
+        IRType* returnType = declaredFuncType->getResultType();
+        if (auto resultType = as<IRResultType>(declaredFuncType->getResultType()))
+        {
+            nativeParamTypes.add(builder.getPtrType(resultType->getValueType()));
+            returnType = resultType->getErrorType();
+        }
+        getNativeType(builder, declaredFuncType->getResultType());
+        auto funcType = builder.getFuncType(
+            nativeParamTypes.getCount(), (IRType**)nativeParamTypes.getBuffer(), returnType);
+
+        return funcType;
+    }
+
+    void NativeCallMarshallingContext::marshalRefManagedValueToNativeValue(
+        IRBuilder& builder, IRInst* originalArg, List<IRInst*>& args)
+    {
+        SLANG_UNUSED(builder);
+        SLANG_UNUSED(originalArg);
+        args.add(originalArg);
+    }
+
+    void NativeCallMarshallingContext::marshalManagedValueToNativeValue(
+        IRBuilder& builder, IRInst* originalArg, List<IRInst*>& args)
+    {
+        switch (originalArg->getDataType()->getOp())
+        {
+        case kIROp_InOutType:
+        case kIROp_RefType:
+            return marshalRefManagedValueToNativeValue(
+                builder, originalArg, args);
+        case kIROp_StringType:
+            {
+                auto nativeStr = builder.emitGetNativeString(originalArg);
+                args.add(nativeStr);
+            }
+            break;
+        default:
+            args.add(originalArg);
+            break;
+        }
+    }
+
+    IRInst* NativeCallMarshallingContext::marshalNativeValueToManagedValue(
+        IRBuilder& builder, IRInst* nativeVal)
+    {
+        switch (nativeVal->getDataType()->getOp())
+        {
+        case kIROp_NativeStringType:
+            {
+                return builder.emitMakeString(nativeVal);
+            }
+            break;
+        default:
+            return nativeVal;
+            break;
+        }
+    }
+
+    IRInst* NativeCallMarshallingContext::marshalNativeCall(
+        IRBuilder& builder,
+        IRFuncType* originalFuncType,
+        IRFuncType* nativeFuncType,
+        IRInst* nativeFunc,
+        Int argCount,
+        IRInst*const* originalArgs)
+    {
+        // Marshal parameters to arguments into native func.
+        List<IRInst*> args;
+        for (Int i = 0; i < argCount; i++)
+        {
+            marshalManagedValueToNativeValue(builder, originalArgs[i], args);
+        }
+        IRType* originalReturnType = originalFuncType->getResultType();
+
+        IRVar* resultVar = nullptr;
+        if (auto resultType = as<IRResultType>(originalReturnType))
+        {
+            // Declare a local variable to receive result.
+            resultVar = builder.emitVar(getNativeType(builder, resultType->getValueType()));
+            args.add(resultVar);
+        }
+
+        // Insert call.
+        IRInst* call = builder.emitCallInst(nativeFuncType->getResultType(), nativeFunc, args);
+
+        // TODO: marshal output/ref args back to original args.
+
+        IRInst* returnValue = call;
+
+        // Marshal result and out arguments back to managed values.
+        if (auto resultType = as<IRResultType>(originalReturnType))
+        {
+            auto val = builder.emitLoad(resultVar);
+            auto err = call;
+            val = marshalNativeValueToManagedValue(builder, val);
+            auto intErr = err;
+            if (err->getDataType()->getOp() != kIROp_IntType)
+            {
+                intErr = builder.emitConstructorInst(builder.getIntType(), 1, &err);
+            }
+            auto errIsError = builder.emitLess(intErr, builder.getIntValue(builder.getIntType(), 0));
+            IRBlock *trueBlock, *falseBlock, *afterBlock;
+            builder.emitIfElseWithBlocks(errIsError, trueBlock, falseBlock, afterBlock);
+            builder.setInsertInto(trueBlock);
+            returnValue = builder.emitMakeResultError(resultType, err);
+            builder.emitBranch(afterBlock, 1, &returnValue);
+            builder.setInsertInto(falseBlock);
+            returnValue = builder.emitMakeResultValue(resultType, val);
+            builder.emitBranch(afterBlock, 1, &returnValue);
+            builder.setInsertInto(afterBlock);
+            returnValue = builder.emitParam(resultType);
+        }
+        else
+        {
+            returnValue = marshalNativeValueToManagedValue(builder, call);
+        }
+        return returnValue;
+    }
+
+} // namespace Slang
diff --git a/source/slang/slang-ir-marshal-native-call.h b/source/slang/slang-ir-marshal-native-call.h
new file mode 100644
index 000000000..bbc2078ea
--- /dev/null
+++ b/source/slang/slang-ir-marshal-native-call.h
@@ -0,0 +1,50 @@
+// slang-ir-marshal-native-call.h
+#pragma once
+
+#include "../core/slang-basic.h"
+
+namespace Slang
+{
+    class DiagnosticSink;
+    struct IRModule;
+    struct IRBuilder;
+    struct IRType;
+    struct IRFunc;
+    struct IRFuncType;
+    struct IRCall;
+    struct IRInst;
+
+    class NativeCallMarshallingContext
+    {
+    public:
+        DiagnosticSink* diagnosticSink = nullptr;
+    public:
+        // Get a native type for `type` that can be used directly in a native function signature.
+        IRType* getNativeType(IRBuilder& builder, IRType* type);
+
+        // Get a native function type of `func`.
+        IRFuncType* getNativeFuncType(IRBuilder& builder, IRFuncType* declaredFuncType);
+
+        // Insert a call at builder's current position into a native func with original arguments.
+        // `originalArgs` will be marshalled to native args before the actual call.
+        // returns the managed result value of the call.
+        // Note: additional insts maybe inserted after the call inst to marshal the native output values back
+        // to non-native arguments/return values.
+        IRInst* marshalNativeCall(
+            IRBuilder& builder,
+            IRFuncType* originalFuncType,
+            IRFuncType* nativeFuncType,
+            IRInst* nativeFunc,
+            Int argCount,
+            IRInst* const* originalArgs);
+
+        void marshalRefManagedValueToNativeValue(
+            IRBuilder& builder, IRInst* originalArg, List<IRInst*>& args);
+
+        void marshalManagedValueToNativeValue(
+            IRBuilder& builder, IRInst* originalArg, List<IRInst*>& args);
+
+        IRInst* marshalNativeValueToManagedValue(
+            IRBuilder& builder, IRInst* nativeValue);
+    };
+}
diff --git a/source/slang/slang-ir-peephole.cpp b/source/slang/slang-ir-peephole.cpp
new file mode 100644
index 000000000..6cb5d2971
--- /dev/null
+++ b/source/slang/slang-ir-peephole.cpp
@@ -0,0 +1,110 @@
+#include "slang-ir-peephole.h"
+#include "slang-ir-inst-pass-base.h"
+
+namespace Slang
+{
+struct PeepholeContext : InstPassBase
+{
+    PeepholeContext(IRModule* inModule)
+        : InstPassBase(inModule)
+    {}
+
+    bool changed = false;
+
+    void processInst(IRInst* inst)
+    {
+        switch (inst->getOp())
+        {
+        case kIROp_GetResultError:
+            if (inst->getOperand(0)->getOp() == kIROp_MakeResultError)
+            {
+                inst->replaceUsesWith(inst->getOperand(0)->getOperand(0));
+                changed = true;
+            }
+            break;
+        case kIROp_GetResultValue:
+            if (inst->getOperand(0)->getOp() == kIROp_MakeResultValue)
+            {
+                inst->replaceUsesWith(inst->getOperand(0)->getOperand(0));
+                inst->removeAndDeallocate();
+                changed = true;
+            }
+            break;
+        case kIROp_IsResultError:
+            if (inst->getOperand(0)->getOp() == kIROp_MakeResultError)
+            {
+                IRBuilder builder(&sharedBuilderStorage);
+                inst->replaceUsesWith(builder.getBoolValue(true));
+                inst->removeAndDeallocate();
+                changed = true;
+            }
+            else if (inst->getOperand(0)->getOp() == kIROp_MakeResultValue)
+            {
+                IRBuilder builder(&sharedBuilderStorage);
+                inst->replaceUsesWith(builder.getBoolValue(false));
+                inst->removeAndDeallocate();
+                changed = true;
+            }
+            break;
+        case kIROp_GetTupleElement:
+            if (inst->getOperand(0)->getOp() == kIROp_MakeTuple)
+            {
+                auto element = inst->getOperand(1);
+                if (auto intLit = as<IRIntLit>(element))
+                {
+                    inst->replaceUsesWith(inst->getOperand(0)->getOperand((UInt)intLit->value.intVal));
+                    inst->removeAndDeallocate();
+                    changed = true;
+                }
+            }
+            break;
+        case kIROp_FieldExtract:
+            if (inst->getOperand(0)->getOp() == kIROp_makeStruct)
+            {
+                auto field = as<IRFieldExtract>(inst)->field.get();
+                Index fieldIndex = -1;
+                auto structType = as<IRStructType>(inst->getOperand(0)->getDataType());
+                if (structType)
+                {
+                    Index i = 0;
+                    for (auto sfield : structType->getFields())
+                    {
+                        if (sfield == field)
+                        {
+                            fieldIndex = i;
+                            break;
+                        }
+                        i++;
+                    }
+                    if (fieldIndex != -1 && fieldIndex < (Index)inst->getOperand(0)->getOperandCount())
+                    {
+                        inst->replaceUsesWith(inst->getOperand(0)->getOperand((UInt)fieldIndex));
+                        inst->removeAndDeallocate();
+                        changed = true;
+                    }
+                }
+            }
+            break;
+        default:
+            break;
+        }
+    }
+
+    bool processModule()
+    {
+        SharedIRBuilder* sharedBuilder = &sharedBuilderStorage;
+        sharedBuilder->init(module);
+
+        changed = false;
+        processAllInsts([this](IRInst* inst) { processInst(inst); });
+        return changed;
+    }
+};
+
+bool peepholeOptimize(IRModule* module)
+{
+    PeepholeContext context = PeepholeContext(module);
+    return context.processModule();
+}
+
+} // namespace Slang
diff --git a/source/slang/slang-ir-peephole.h b/source/slang/slang-ir-peephole.h
new file mode 100644
index 000000000..e05c533eb
--- /dev/null
+++ b/source/slang/slang-ir-peephole.h
@@ -0,0 +1,11 @@
+// slang-ir-peephole.h
+#pragma once
+
+namespace Slang
+{
+    struct IRModule;
+    struct IRCall;
+
+        /// Apply peephole optimizations.
+    bool peepholeOptimize(IRModule* module);
+}
diff --git a/source/slang/slang-ir-ssa-simplification.cpp b/source/slang/slang-ir-ssa-simplification.cpp
index fcc6dc4ae..22aea8d36 100644
--- a/source/slang/slang-ir-ssa-simplification.cpp
+++ b/source/slang/slang-ir-ssa-simplification.cpp
@@ -5,6 +5,7 @@
 #include "slang-ir-sccp.h"
 #include "slang-ir-dce.h"
 #include "slang-ir-simplify-cfg.h"
+#include "slang-ir-peephole.h"
 
 namespace Slang
 {
@@ -21,6 +22,7 @@ namespace Slang
         {
             changed = false;
             changed |= applySparseConditionalConstantPropagation(module);
+            changed |= peepholeOptimize(module);
             changed |= simplifyCFG(module);
 
             // Note: we disregard the `changed` state from dead code elimination pass since
diff --git a/source/slang/slang-ir.cpp b/source/slang/slang-ir.cpp
index 562d0ea1a..42ff5823b 100644
--- a/source/slang/slang-ir.cpp
+++ b/source/slang/slang-ir.cpp
@@ -3224,6 +3224,16 @@ namespace Slang
         return emitMakeTuple(type, count, args);
     }
 
+    IRInst* IRBuilder::emitMakeString(IRInst* nativeStr)
+    {
+        return emitIntrinsicInst(getStringType(), kIROp_makeString, 1, &nativeStr);
+    }
+
+    IRInst* IRBuilder::emitGetNativeString(IRInst* str)
+    {
+        return emitIntrinsicInst(getNativeStringType(), kIROp_getNativeStr, 1, &str);
+    }
+
     IRInst* IRBuilder::emitGetTupleElement(IRType* type, IRInst* tuple, UInt element)
     {
         // As a quick simplification/optimization, if the user requests
@@ -4022,6 +4032,18 @@ namespace Slang
         return inst;
     }
 
+    IRInst* IRBuilder::emitBranch(IRBlock* block, Int argCount, IRInst* const* args)
+    {
+        List<IRInst*> argList;
+        argList.add(block);
+        for (Int i = 0; i < argCount; ++i)
+            argList.add(args[i]);
+        auto inst =
+            createInst<IRUnconditionalBranch>(this, kIROp_unconditionalBranch, nullptr, argList.getCount(), argList.getBuffer());
+        addInst(inst);
+        return inst;
+    }
+
     IRInst* IRBuilder::emitBreak(
         IRBlock*    target)
     {
@@ -4089,6 +4111,25 @@ namespace Slang
         return inst;
     }
 
+    IRInst* IRBuilder::emitIfElseWithBlocks(
+        IRInst* val, IRBlock*& outTrueBlock, IRBlock*& outFalseBlock, IRBlock*& outAfterBlock)
+    {
+        outTrueBlock = createBlock();
+        outAfterBlock = createBlock();
+        outFalseBlock = createBlock();
+        auto f = getFunc();
+        SLANG_ASSERT(f);
+        if (f)
+        {
+            f->addBlock(outTrueBlock);
+            f->addBlock(outAfterBlock);
+            f->addBlock(outFalseBlock);
+        }
+        auto result = emitIfElse(val, outTrueBlock, outFalseBlock, outAfterBlock);
+        setInsertInto(outTrueBlock);
+        return result;
+    }
+
     IRInst* IRBuilder::emitIf(
         IRInst*    val,
         IRBlock*    trueBlock,
@@ -4097,6 +4138,18 @@ namespace Slang
         return emitIfElse(val, trueBlock, afterBlock, afterBlock);
     }
 
+    IRInst* IRBuilder::emitIfWithBlocks(
+        IRInst* val, IRBlock*& outTrueBlock, IRBlock*& outAfterBlock)
+    {
+        outTrueBlock = createBlock();
+        outAfterBlock = createBlock();
+        auto result = emitIf(val, outTrueBlock, outAfterBlock);
+        insertBlock(outTrueBlock);
+        insertBlock(outAfterBlock);
+        setInsertInto(outTrueBlock);
+        return result;
+    }
+
     IRInst* IRBuilder::emitLoopTest(
         IRInst*     val,
         IRBlock*    bodyBlock,
@@ -4320,6 +4373,13 @@ namespace Slang
         return inst;
     }
 
+    IRInst* IRBuilder::emitLess(IRInst* left, IRInst* right)
+    {
+        auto inst = createInst<IRInst>(this, kIROp_Less, getBoolType(), left, right);
+        addInst(inst);
+        return inst;
+    }
+
     IRInst* IRBuilder::emitMul(IRType* type, IRInst* left, IRInst* right)
     {
         auto inst = createInst<IRInst>(
@@ -5886,6 +5946,13 @@ namespace Slang
         case kIROp_MakeMatrix:
         case kIROp_makeArray:
         case kIROp_makeStruct:
+        case kIROp_makeString:
+        case kIROp_getNativeStr:
+        case kIROp_MakeResultError:
+        case kIROp_MakeResultValue:
+        case kIROp_GetResultError:
+        case kIROp_GetResultValue:
+        case kIROp_IsResultError:
         case kIROp_Load:    // We are ignoring the possibility of loads from bad addresses, or `volatile` loads
         case kIROp_ImageSubscript:
         case kIROp_FieldExtract: