[clang] CodeGen: Make getOrEmitProtocol public for Swift

Summary:
Swift would like to use clang's apis to emit protocol declarations.

This commits adds the public API:

```
 emitObjCProtocolObject(CodeGenModule &CGM, const ObjCProtocolDecl *p);
```

rdar://60888524

Subscribers: cfe-commits

Tags: #clang

Differential Revision: https://reviews.llvm.org/D77077

clang/include/clang/CodeGen/CodeGenABITypes.h

@@ -28,11 +28,12 @@
 #include "clang/CodeGen/CGFunctionInfo.h"
 
 namespace llvm {
-  class DataLayout;
-  class Module;
-  class Function;
-  class FunctionType;
-  class Type;
+class Constant;
+class DataLayout;
+class Module;
+class Function;
+class FunctionType;
+class Type;
 }
 
 namespace clang {
@@ -44,6 +45,7 @@ class CoverageSourceInfo;
 class DiagnosticsEngine;
 class HeaderSearchOptions;
 class ObjCMethodDecl;
+class ObjCProtocolDecl;
 class PreprocessorOptions;
 
 namespace CodeGen {
@@ -137,6 +139,13 @@ llvm::Function *getNonTrivialCStructDestructor(CodeGenModule &CGM,
                                                CharUnits DstAlignment,
                                                bool IsVolatile, QualType QT);
 
+/// Get a pointer to a protocol object for the given declaration, emitting it if
+/// it hasn't already been emitted in this translation unit. Note that the ABI
+/// for emitting a protocol reference in code (e.g. for a protocol expression)
+/// in most runtimes is not as simple as just materializing a pointer to this
+/// object.
+llvm::Constant *emitObjCProtocolObject(CodeGenModule &CGM,
+                                       const ObjCProtocolDecl *p);
 }  // end namespace CodeGen
 }  // end namespace clang
 

clang/lib/CodeGen/CGObjCGNU.cpp

@@ -617,6 +617,13 @@ public:
   llvm::Value *GenerateProtocolRef(CodeGenFunction &CGF,
                                    const ObjCProtocolDecl *PD) override;
   void GenerateProtocol(const ObjCProtocolDecl *PD) override;
+
+  virtual llvm::Constant *GenerateProtocolRef(const ObjCProtocolDecl *PD);
+
+  llvm::Constant *GetOrEmitProtocol(const ObjCProtocolDecl *PD) override {
+    return GenerateProtocolRef(PD);
+  }
+
   llvm::Function *ModuleInitFunction() override;
   llvm::FunctionCallee GetPropertyGetFunction() override;
   llvm::FunctionCallee GetPropertySetFunction() override;
@@ -1348,7 +1355,7 @@ class CGObjCGNUstep2 : public CGObjCGNUstep {
   void GenerateProtocol(const ObjCProtocolDecl *PD) override {
     // Do nothing - we only emit referenced protocols.
   }
-  llvm::Constant *GenerateProtocolRef(const ObjCProtocolDecl *PD) {
+  llvm::Constant *GenerateProtocolRef(const ObjCProtocolDecl *PD) override {
     std::string ProtocolName = PD->getNameAsString();
     auto *&Protocol = ExistingProtocols[ProtocolName];
     if (Protocol)
@@ -3039,13 +3046,18 @@ CGObjCGNU::GenerateProtocolList(ArrayRef<std::string> Protocols) {
 
 llvm::Value *CGObjCGNU::GenerateProtocolRef(CodeGenFunction &CGF,
                                             const ObjCProtocolDecl *PD) {
+  auto protocol = GenerateProtocolRef(PD);
+  llvm::Type *T =
+      CGM.getTypes().ConvertType(CGM.getContext().getObjCProtoType());
+  return CGF.Builder.CreateBitCast(protocol, llvm::PointerType::getUnqual(T));
+}
+
+llvm::Constant *CGObjCGNU::GenerateProtocolRef(const ObjCProtocolDecl *PD) {
   llvm::Constant *&protocol = ExistingProtocols[PD->getNameAsString()];
   if (!protocol)
     GenerateProtocol(PD);
   assert(protocol && "Unknown protocol");
-  llvm::Type *T =
-    CGM.getTypes().ConvertType(CGM.getContext().getObjCProtoType());
-  return CGF.Builder.CreateBitCast(protocol, llvm::PointerType::getUnqual(T));
+  return protocol;
 }
 
 llvm::Constant *

clang/lib/CodeGen/CGObjCMac.cpp

@@ -1107,11 +1107,6 @@ public:
 
   void GenerateProtocol(const ObjCProtocolDecl *PD) override;
 
-  /// GetOrEmitProtocol - Get the protocol object for the given
-  /// declaration, emitting it if necessary. The return value has type
-  /// ProtocolPtrTy.
-  virtual llvm::Constant *GetOrEmitProtocol(const ObjCProtocolDecl *PD)=0;
-
   /// GetOrEmitProtocolRef - Get a forward reference to the protocol
   /// object for the given declaration, emitting it if needed. These
   /// forward references will be filled in with empty bodies if no

clang/lib/CodeGen/CGObjCRuntime.cpp

@@ -13,14 +13,15 @@
 //===----------------------------------------------------------------------===//
 
 #include "CGObjCRuntime.h"
-#include "CGCleanup.h"
 #include "CGCXXABI.h"
+#include "CGCleanup.h"
 #include "CGRecordLayout.h"
 #include "CodeGenFunction.h"
 #include "CodeGenModule.h"
 #include "clang/AST/RecordLayout.h"
 #include "clang/AST/StmtObjC.h"
 #include "clang/CodeGen/CGFunctionInfo.h"
+#include "clang/CodeGen/CodeGenABITypes.h"
 #include "llvm/Support/SaveAndRestore.h"
 
 using namespace clang;
@@ -383,3 +384,9 @@ CGObjCRuntime::getMessageSendInfo(const ObjCMethodDecl *method,
     CGM.getTypes().GetFunctionType(argsInfo)->getPointerTo();
   return MessageSendInfo(argsInfo, signatureType);
 }
+
+llvm::Constant *
+clang::CodeGen::emitObjCProtocolObject(CodeGenModule &CGM,
+                                       const ObjCProtocolDecl *protocol) {
+  return CGM.getObjCRuntime().GetOrEmitProtocol(protocol);
+}

clang/lib/CodeGen/CGObjCRuntime.h

@@ -211,6 +211,11 @@ public:
   /// implementations.
   virtual void GenerateProtocol(const ObjCProtocolDecl *OPD) = 0;
 
+  /// GetOrEmitProtocol - Get the protocol object for the given
+  /// declaration, emitting it if necessary. The return value has type
+  /// ProtocolPtrTy.
+  virtual llvm::Constant *GetOrEmitProtocol(const ObjCProtocolDecl *PD) = 0;
+
   /// Generate a function preamble for a method with the specified
   /// types.