[Async CC] Add constant "pointer" for async func.

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/CallEmission.h

@@ -67,6 +67,7 @@ class CallEmission {
   void emitToUnmappedExplosion(Explosion &out);
   virtual void emitCallToUnmappedExplosion(llvm::CallInst *call, Explosion &out) = 0;
   void emitYieldsToExplosion(Explosion &out);
+  virtual FunctionPointer getCalleeFunctionPointer() = 0;
   llvm::CallInst *emitCallSite();
 
   CallEmission(IRGenFunction &IGF, llvm::Value *selfValue, Callee &&callee)

lib/IRGen/Callee.h

@@ -124,7 +124,31 @@ namespace irgen {
 
   /// A function pointer value.
   class FunctionPointer {
-    /// The actual function pointer.
+  public:
+    struct KindTy {
+      enum class Value {
+        Function,
+        AsyncFunctionPointer,
+      };
+      static const Value Function = Value::Function;
+      static const Value AsyncFunctionPointer = Value::AsyncFunctionPointer;
+      Value value;
+      KindTy(Value value) : value(value) {}
+      KindTy(CanSILFunctionType fnType)
+          : value(fnType->isAsync() ? Value::AsyncFunctionPointer
+                                    : Value::Function) {}
+      friend bool operator==(const KindTy &lhs, const KindTy &rhs) {
+        return lhs.value == rhs.value;
+      }
+      friend bool operator!=(const KindTy &lhs, const KindTy &rhs) {
+        return !(lhs == rhs);
+      }
+    };
+
+  private:
+    KindTy Kind;
+
+    /// The actual pointer, either to the function or to its descriptor.
     llvm::Value *Value;
 
     PointerAuthInfo AuthInfo;
@@ -135,25 +159,27 @@ namespace irgen {
     /// Construct a FunctionPointer for an arbitrary pointer value.
     /// We may add more arguments to this; try to use the other
     /// constructors/factories if possible.
-    explicit FunctionPointer(llvm::Value *value, PointerAuthInfo authInfo,
+    explicit FunctionPointer(KindTy kind, llvm::Value *value,
+                             PointerAuthInfo authInfo,
                              const Signature &signature)
-        : Value(value), AuthInfo(authInfo), Sig(signature) {
+        : Kind(kind), Value(value), AuthInfo(authInfo), Sig(signature) {
       // The function pointer should have function type.
       assert(value->getType()->getPointerElementType()->isFunctionTy());
       // TODO: maybe assert similarity to signature.getType()?
     }
 
     // Temporary only!
-    explicit FunctionPointer(llvm::Value *value, const Signature &signature)
-      : FunctionPointer(value, PointerAuthInfo(), signature) {}
+    explicit FunctionPointer(KindTy kind, llvm::Value *value,
+                             const Signature &signature)
+        : FunctionPointer(kind, value, PointerAuthInfo(), signature) {}
 
     static FunctionPointer forDirect(IRGenModule &IGM,
                                      llvm::Constant *value,
                                      CanSILFunctionType fnType);
 
-    static FunctionPointer forDirect(llvm::Constant *value,
+    static FunctionPointer forDirect(KindTy kind, llvm::Constant *value,
                                      const Signature &signature) {
-      return FunctionPointer(value, PointerAuthInfo(), signature);
+      return FunctionPointer(kind, value, PointerAuthInfo(), signature);
     }
 
     static FunctionPointer forExplosionValue(IRGenFunction &IGF,
@@ -166,8 +192,17 @@ namespace irgen {
       return (isa<llvm::Constant>(Value) && AuthInfo.isConstant());
     }
 
+    KindTy getKind() const { return Kind; }
+
+    /// Given that this value is known to have been constructed from a direct
+    /// function,  Return the name of that function.
+    StringRef getName(IRGenModule &IGM) const;
+
     /// Return the actual function pointer.
-    llvm::Value *getPointer() const { return Value; }
+    llvm::Value *getPointer(IRGenFunction &IGF) const;
+
+    /// Return the actual function pointer.
+    llvm::Value *getRawPointer() const { return Value; }
 
     /// Given that this value is known to have been constructed from
     /// a direct function, return the function pointer.
@@ -205,6 +240,9 @@ namespace irgen {
 
     llvm::Value *getExplosionValue(IRGenFunction &IGF,
                                    CanSILFunctionType fnType) const;
+
+    /// Form a FunctionPointer whose KindTy is ::Function.
+    FunctionPointer getAsFunction(IRGenFunction &IGF) const;
   };
 
   class Callee {