[CodeGen] Add public function to emit C++ destructor call.

Adds `CodeGen::getCXXDestructorImplicitParam`, to retrieve a C++ destructor's implicit parameter (after the "this" pointer) based on the ABI in the given CodeGenModule.

This will allow other frontends (Swift, for example) to easily emit calls to object destructors with correct ABI semantics and calling convetions.

This is needed for Swift C++ interop. Here's the corresponding Swift change: swiftlang/swift#32291

Differential Revision: https://reviews.llvm.org/D82392

Author: zoecarver

clang/include/clang/CodeGen/CodeGenABITypes.h

@@ -25,7 +25,9 @@
 
 #include "clang/AST/CanonicalType.h"
 #include "clang/AST/Type.h"
+#include "clang/Basic/ABI.h"
 #include "clang/CodeGen/CGFunctionInfo.h"
+#include "llvm/IR/BasicBlock.h"
 
 namespace llvm {
   class AttrBuilder;
@@ -40,6 +42,7 @@ namespace llvm {
 namespace clang {
 class ASTContext;
 class CXXConstructorDecl;
+class CXXDestructorDecl;
 class CXXRecordDecl;
 class CXXMethodDecl;
 class CodeGenOptions;
@@ -90,6 +93,12 @@ const CGFunctionInfo &arrangeFreeFunctionCall(CodeGenModule &CGM,
 ImplicitCXXConstructorArgs
 getImplicitCXXConstructorArgs(CodeGenModule &CGM, const CXXConstructorDecl *D);
 
+llvm::Value *
+getCXXDestructorImplicitParam(CodeGenModule &CGM, llvm::BasicBlock *InsertBlock,
+                              llvm::BasicBlock::iterator InsertPoint,
+                              const CXXDestructorDecl *D, CXXDtorType Type,
+                              bool ForVirtualBase, bool Delegating);
+
 /// Returns null if the function type is incomplete and can't be lowered.
 llvm::FunctionType *convertFreeFunctionType(CodeGenModule &CGM,
                                             const FunctionDecl *FD);

clang/lib/CodeGen/ABIInfo.h

@@ -28,7 +28,6 @@ namespace clang {
 
 namespace CodeGen {
   class ABIArgInfo;
-  class Address;
   class CGCXXABI;
   class CGFunctionInfo;
   class CodeGenFunction;

clang/lib/CodeGen/CGCXXABI.h

@@ -400,6 +400,13 @@ class CGCXXABI {
                              CXXCtorType Type, bool ForVirtualBase,
                              bool Delegating, CallArgList &Args);
 
+  /// Get the implicit (second) parameter that comes after the "this" pointer,
+  /// or nullptr if there is isn't one.
+  virtual llvm::Value *
+  getCXXDestructorImplicitParam(CodeGenFunction &CGF,
+                                const CXXDestructorDecl *DD, CXXDtorType Type,
+                                bool ForVirtualBase, bool Delegating) = 0;
+
   /// Emit the destructor call.
   virtual void EmitDestructorCall(CodeGenFunction &CGF,
                                   const CXXDestructorDecl *DD, CXXDtorType Type,

clang/lib/CodeGen/CodeGenABITypes.cpp

@@ -115,3 +115,16 @@ unsigned CodeGen::getLLVMFieldNumber(CodeGenModule &CGM,
                                      const FieldDecl *FD) {
   return CGM.getTypes().getCGRecordLayout(RD).getLLVMFieldNo(FD);
 }
+
+llvm::Value *CodeGen::getCXXDestructorImplicitParam(
+    CodeGenModule &CGM, llvm::BasicBlock *InsertBlock,
+    llvm::BasicBlock::iterator InsertPoint, const CXXDestructorDecl *D,
+    CXXDtorType Type, bool ForVirtualBase, bool Delegating) {
+  CodeGenFunction CGF(CGM, /*suppressNewContext=*/true);
+  CGF.CurCodeDecl = D;
+  CGF.CurFuncDecl = D;
+  CGF.CurFn = InsertBlock->getParent();
+  CGF.Builder.SetInsertPoint(InsertBlock, InsertPoint);
+  return CGM.getCXXABI().getCXXDestructorImplicitParam(
+      CGF, D, Type, ForVirtualBase, Delegating);
+}

clang/lib/CodeGen/ItaniumCXXABI.cpp

@@ -229,6 +229,12 @@ class ItaniumCXXABI : public CodeGen::CGCXXABI {
                                                bool ForVirtualBase,
                                                bool Delegating) override;
 
+  llvm::Value *getCXXDestructorImplicitParam(CodeGenFunction &CGF,
+                                             const CXXDestructorDecl *DD,
+                                             CXXDtorType Type,
+                                             bool ForVirtualBase,
+                                             bool Delegating) override;
+
   void EmitDestructorCall(CodeGenFunction &CGF, const CXXDestructorDecl *DD,
                           CXXDtorType Type, bool ForVirtualBase,
                           bool Delegating, Address This,
@@ -1717,13 +1723,21 @@ CGCXXABI::AddedStructorArgs ItaniumCXXABI::getImplicitConstructorArgs(
   return AddedStructorArgs::prefix({{VTT, VTTTy}});
 }
 
+llvm::Value *ItaniumCXXABI::getCXXDestructorImplicitParam(
+    CodeGenFunction &CGF, const CXXDestructorDecl *DD, CXXDtorType Type,
+    bool ForVirtualBase, bool Delegating) {
+  GlobalDecl GD(DD, Type);
+  return CGF.GetVTTParameter(GD, ForVirtualBase, Delegating);
+}
+
 void ItaniumCXXABI::EmitDestructorCall(CodeGenFunction &CGF,
                                        const CXXDestructorDecl *DD,
                                        CXXDtorType Type, bool ForVirtualBase,
                                        bool Delegating, Address This,
                                        QualType ThisTy) {
   GlobalDecl GD(DD, Type);
-  llvm::Value *VTT = CGF.GetVTTParameter(GD, ForVirtualBase, Delegating);
+  llvm::Value *VTT =
+      getCXXDestructorImplicitParam(CGF, DD, Type, ForVirtualBase, Delegating);
   QualType VTTTy = getContext().getPointerType(getContext().VoidPtrTy);
 
   CGCallee Callee;

clang/lib/CodeGen/MicrosoftCXXABI.cpp

@@ -259,6 +259,12 @@ class MicrosoftCXXABI : public CGCXXABI {
                                                bool ForVirtualBase,
                                                bool Delegating) override;
 
+  llvm::Value *getCXXDestructorImplicitParam(CodeGenFunction &CGF,
+                                             const CXXDestructorDecl *DD,
+                                             CXXDtorType Type,
+                                             bool ForVirtualBase,
+                                             bool Delegating) override;
+
   void EmitDestructorCall(CodeGenFunction &CGF, const CXXDestructorDecl *DD,
                           CXXDtorType Type, bool ForVirtualBase,
                           bool Delegating, Address This,
@@ -1577,6 +1583,12 @@ CGCXXABI::AddedStructorArgs MicrosoftCXXABI::getImplicitConstructorArgs(
   return AddedStructorArgs::suffix({{MostDerivedArg, getContext().IntTy}});
 }
 
+llvm::Value *MicrosoftCXXABI::getCXXDestructorImplicitParam(
+    CodeGenFunction &CGF, const CXXDestructorDecl *DD, CXXDtorType Type,
+    bool ForVirtualBase, bool Delegating) {
+  return nullptr;
+}
+
 void MicrosoftCXXABI::EmitDestructorCall(CodeGenFunction &CGF,
                                          const CXXDestructorDecl *DD,
                                          CXXDtorType Type, bool ForVirtualBase,
@@ -1603,8 +1615,11 @@ void MicrosoftCXXABI::EmitDestructorCall(CodeGenFunction &CGF,
     BaseDtorEndBB = EmitDtorCompleteObjectHandler(CGF);
   }
 
+  llvm::Value *Implicit =
+      getCXXDestructorImplicitParam(CGF, DD, Type, ForVirtualBase,
+                                    Delegating); // = nullptr
   CGF.EmitCXXDestructorCall(GD, Callee, This.getPointer(), ThisTy,
-                            /*ImplicitParam=*/nullptr,
+                            /*ImplicitParam=*/Implicit,
                             /*ImplicitParamTy=*/QualType(), nullptr);
   if (BaseDtorEndBB) {
     // Complete object handler should continue to be the remaining