FunctionPassContext: support setting arbitrary function type representations when creating specialized functions

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/ClosureSpecialization.swift

@@ -410,7 +410,7 @@ private struct SpecializationInfo {
         // The specialized function is always a thin function. This is important because we add additional
         // parameters after the Self parameter of witness methods. In this case the new function is not a
         // method anymore.
-        makeThin: true, makeBare: true)
+        withRepresentation: .thin, makeBare: true)
 
     context.buildSpecializedFunction(
       specializedFunction: specializedFunction,

SwiftCompilerSources/Sources/Optimizer/FunctionPasses/PackSpecialization.swift

@@ -553,7 +553,7 @@ private struct PackExplodedFunction {
         withParams: newParameters,
         withResults: newResults,
         // If a method has a dynamic self parameter, it cannot be converted into a thin function (non-method).
-        makeThin: !original.mayBindDynamicSelf)
+        withRepresentation: original.mayBindDynamicSelf ? nil : .thin)
 
       self.buildSpecializedFunction(context)
     }

SwiftCompilerSources/Sources/Optimizer/PassManager/FunctionPassContext.swift

@@ -168,12 +168,13 @@ struct FunctionPassContext : MutatingContext {
     from original: Function, withName specializedFunctionName: String,
     withParams specializedParameters: [ParameterInfo],
     withResults specializedResults: [ResultInfo]? = nil,
-    makeThin: Bool = false,
+    withRepresentation: FunctionTypeRepresentation? = nil,
     makeBare: Bool = false,
     preserveGenericSignature: Bool = true
   ) -> Function {
     return specializedFunctionName._withBridgedStringRef { nameRef in
       let bridgedParamInfos = specializedParameters.map { $0._bridged }
+      let repr = withRepresentation ?? original.loweredFunctionType.functionTypeRepresentation
 
       return bridgedParamInfos.withUnsafeBufferPointer { paramBuf in
 
@@ -183,7 +184,7 @@ struct FunctionPassContext : MutatingContext {
             return bridgedPassContext.createSpecializedFunctionDeclaration(
               nameRef, paramBuf.baseAddress, paramBuf.count,
               resultBuf.baseAddress, resultBuf.count,
-              original.bridged, makeThin, makeBare,
+              original.bridged, repr.bridged, makeBare,
               preserveGenericSignature
             ).function
           }
@@ -191,7 +192,7 @@ struct FunctionPassContext : MutatingContext {
           return bridgedPassContext.createSpecializedFunctionDeclaration(
             nameRef, paramBuf.baseAddress, paramBuf.count,
             nil, 0,
-            original.bridged, makeThin, makeBare,
+            original.bridged, repr.bridged, makeBare,
             preserveGenericSignature
           ).function
         }

include/swift/SILOptimizer/OptimizerBridging.h

@@ -274,7 +274,7 @@ struct BridgedPassContext {
                                                         const BridgedResultInfo *_Nullable specializedBridgedResults,
                                                         SwiftInt resultCount,
                                                         BridgedFunction bridgedOriginal,
-                                                        bool makeThin,
+                                                        BridgedASTType::FunctionTypeRepresentation representation,
                                                         bool makeBare,
                                                         bool preserveGenericSignature) const;
 

lib/SILOptimizer/Utils/OptimizerBridging.cpp

@@ -393,7 +393,7 @@ createSpecializedFunctionDeclaration(BridgedStringRef specializedName,
                                      const BridgedResultInfo * _Nullable specializedBridgedResults,
                                      SwiftInt resultCount,
                                      BridgedFunction bridgedOriginal,
-                                     bool makeThin,
+                                     BridgedASTType::FunctionTypeRepresentation representation,
                                      bool makeBare,
                                      bool preserveGenericSignature) const {
   auto *original = bridgedOriginal.getFunction();
@@ -415,9 +415,7 @@ createSpecializedFunctionDeclaration(BridgedStringRef specializedName,
   // The specialized function is always a thin function. This is important
   // because we may add additional parameters after the Self parameter of
   // witness methods. In this case the new function is not a method anymore.
-  auto extInfo = originalType->getExtInfo();
-  if (makeThin)
-    extInfo = extInfo.withRepresentation(SILFunctionTypeRepresentation::Thin);
+  auto extInfo = originalType->getExtInfo().withRepresentation((SILFunctionTypeRepresentation)representation);
 
   auto ClonedTy = SILFunctionType::get(
       preserveGenericSignature ? originalType->getInvocationGenericSignature() : GenericSignature(),