[IRGen] Added LinkEntities for AsyncFunctionPointer.

Two LinkEntities are needed to enable the construction during both IRGen
and TBDGen.

Author: nate-chandler

include/swift/IRGen/Linking.h

@@ -293,6 +293,11 @@ class LinkEntity {
     /// the metadata cache once.
     CanonicalPrespecializedGenericTypeCachingOnceToken,
 
+    /// The same as AsyncFunctionPointer but with a different stored value, for
+    /// use by TBDGen.
+    /// The pointer is a AbstractStorageDecl*.
+    AsyncFunctionPointerAST,
+
     /// The pointer is a SILFunction*.
     DynamicallyReplaceableFunctionKey,
 
@@ -410,6 +415,13 @@ class LinkEntity {
     /// passed to swift_getCanonicalSpecializedMetadata.
     /// The pointer is a canonical TypeBase*.
     NoncanonicalSpecializedGenericTypeMetadataCacheVariable,
+
+    /// Provides the data required to invoke an async function using the async
+    /// calling convention in the form of the size of the context to allocate
+    /// and the relative address of the function to call with that allocated
+    /// context.
+    /// The pointer is a SILFunction*.
+    AsyncFunctionPointer,
   };
   friend struct llvm::DenseMapInfo<LinkEntity>;
 
@@ -418,7 +430,7 @@ class LinkEntity {
   }
 
   static bool isDeclKind(Kind k) {
-    return k <= Kind::CanonicalPrespecializedGenericTypeCachingOnceToken;
+    return k <= Kind::AsyncFunctionPointerAST;
   }
   static bool isTypeKind(Kind k) {
     return k >= Kind::ProtocolWitnessTableLazyAccessFunction;
@@ -1088,6 +1100,21 @@ class LinkEntity {
     return entity;
   }
 
+  static LinkEntity forAsyncFunctionPointer(SILFunction *silFunction) {
+    LinkEntity entity;
+    entity.Pointer = silFunction;
+    entity.SecondaryPointer = nullptr;
+    entity.Data = LINKENTITY_SET_FIELD(
+        Kind, unsigned(LinkEntity::Kind::AsyncFunctionPointer));
+    return entity;
+  }
+
+  static LinkEntity forAsyncFunctionPointer(AbstractFunctionDecl *decl) {
+    LinkEntity entity;
+    entity.setForDecl(Kind::AsyncFunctionPointerAST, decl);
+    return entity;
+  }
+
   void mangle(llvm::raw_ostream &out) const;
   void mangle(SmallVectorImpl<char> &buffer) const;
   std::string mangleAsString() const;
@@ -1110,14 +1137,15 @@ class LinkEntity {
   }
 
   bool hasSILFunction() const {
-    return getKind() == Kind::SILFunction ||
+    return getKind() == Kind::AsyncFunctionPointer ||
            getKind() == Kind::DynamicallyReplaceableFunctionVariable ||
-           getKind() == Kind::DynamicallyReplaceableFunctionKey;
+           getKind() == Kind::DynamicallyReplaceableFunctionKey ||
+           getKind() == Kind::SILFunction;
   }
 
   SILFunction *getSILFunction() const {
     assert(hasSILFunction());
-    return reinterpret_cast<SILFunction*>(Pointer);
+    return reinterpret_cast<SILFunction *>(Pointer);
   }
 
   SILGlobalVariable *getSILGlobalVariable() const {

lib/IRGen/Linking.cpp

@@ -430,6 +430,17 @@ std::string LinkEntity::mangleAsString() const {
     return mangler.mangleSILDifferentiabilityWitnessKey(
         {getSILDifferentiabilityWitness()->getOriginalFunction()->getName(),
          getSILDifferentiabilityWitness()->getConfig()});
+  case Kind::AsyncFunctionPointer: {
+    std::string Result(getSILFunction()->getName());
+    Result.append("AD");
+    return Result;
+  }
+  case Kind::AsyncFunctionPointerAST: {
+    std::string Result;
+    Result = mangler.mangleEntity(getDecl());
+    Result.append("AD");
+    return Result;
+  }
   }
   llvm_unreachable("bad entity kind!");
 }
@@ -663,9 +674,13 @@ SILLinkage LinkEntity::getLinkage(ForDefinition_t forDefinition) const {
   case Kind::DynamicallyReplaceableFunctionKey:
     return getSILFunction()->getLinkage();
 
+  case Kind::AsyncFunctionPointer:
   case Kind::SILFunction:
     return getSILFunction()->getEffectiveSymbolLinkage();
 
+  case Kind::AsyncFunctionPointerAST:
+    return getSILLinkage(getDeclLinkage(getDecl()), forDefinition);
+
   case Kind::DynamicallyReplaceableFunctionImpl:
   case Kind::DynamicallyReplaceableFunctionKeyAST:
     return getSILLinkage(getDeclLinkage(getDecl()), forDefinition);
@@ -712,6 +727,8 @@ bool LinkEntity::isContextDescriptor() const {
   case Kind::ProtocolDescriptor:
   case Kind::OpaqueTypeDescriptor:
     return true;
+  case Kind::AsyncFunctionPointer:
+  case Kind::AsyncFunctionPointerAST:
   case Kind::PropertyDescriptor:
   case Kind::DispatchThunk:
   case Kind::DispatchThunkInitializer:
@@ -780,6 +797,8 @@ bool LinkEntity::isContextDescriptor() const {
 
 llvm::Type *LinkEntity::getDefaultDeclarationType(IRGenModule &IGM) const {
   switch (getKind()) {
+  case Kind::AsyncFunctionPointer:
+    return IGM.AsyncFunctionPointerTy;
   case Kind::ModuleDescriptor:
   case Kind::ExtensionDescriptor:
   case Kind::AnonymousDescriptor:
@@ -909,6 +928,7 @@ Alignment LinkEntity::getAlignment(IRGenModule &IGM) const {
   case Kind::MethodDescriptorAllocator:
   case Kind::OpaqueTypeDescriptor:
     return Alignment(4);
+  case Kind::AsyncFunctionPointer:
   case Kind::ObjCClassRef:
   case Kind::ObjCClass:
   case Kind::TypeMetadataLazyCacheVariable:
@@ -951,6 +971,7 @@ bool LinkEntity::isWeakImported(ModuleDecl *module) const {
       return getSILGlobalVariable()->getDecl()->isWeakImported(module);
     }
     return false;
+  case Kind::AsyncFunctionPointer:
   case Kind::DynamicallyReplaceableFunctionKey:
   case Kind::DynamicallyReplaceableFunctionVariable:
   case Kind::SILFunction: {
@@ -977,6 +998,7 @@ bool LinkEntity::isWeakImported(ModuleDecl *module) const {
     return false;
   }
 
+  case Kind::AsyncFunctionPointerAST:
   case Kind::DispatchThunk:
   case Kind::DispatchThunkInitializer:
   case Kind::DispatchThunkAllocator:
@@ -1053,6 +1075,7 @@ bool LinkEntity::isWeakImported(ModuleDecl *module) const {
 
 DeclContext *LinkEntity::getDeclContextForEmission() const {
   switch (getKind()) {
+  case Kind::AsyncFunctionPointerAST:
   case Kind::DispatchThunk:
   case Kind::DispatchThunkInitializer:
   case Kind::DispatchThunkAllocator:
@@ -1095,6 +1118,7 @@ DeclContext *LinkEntity::getDeclContextForEmission() const {
   case Kind::CanonicalSpecializedGenericSwiftMetaclassStub:
     return getType()->getClassOrBoundGenericClass()->getDeclContext();
 
+  case Kind::AsyncFunctionPointer:
   case Kind::SILFunction:
   case Kind::DynamicallyReplaceableFunctionVariable:
   case Kind::DynamicallyReplaceableFunctionKey: