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

[zoecarver]

Summary

Adds CodeGen::emitCXXDestructorCall, a function that creates a CodeGenFunction using the arguments provided, then invokes CodeGenFunction::EmitCXXDestructorCall.

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: https://github.com/apple/swift/pull/32291

[rjmccall]

Can we do a design more like what we did with constructors?

[zoecarver]

• Remove emitCXXDestructorCall and add getCXXDestructorImplicitParam.

[zoecarver]

@rjmccall I updated this patch to introduce the function getCXXDestructorImplicitParam instead. This should be closer to D79942. It seems like there is never more than one implicit parameter so, I just have it return a single llvm::Value*.

[rjmccall]

LGTM

clang/include/clang/CodeGen/CodeGenABITypes.h

 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLVM_CLANG_CODEGEN_CODEGENABITYPES_H
 #define LLVM_CLANG_CODEGEN_CODEGENABITYPES_H
 
 #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;
 class Constant;
 class DataLayout;
 class Module;
 class Function;
 class FunctionType;
 class Type;
 }
 
 namespace clang {
 class ASTContext;
 class CXXConstructorDecl;
+class CXXDestructorDecl;
 class CXXRecordDecl;
 class CXXMethodDecl;
 class CodeGenOptions;
 class CoverageSourceInfo;
 class DiagnosticsEngine;
 class HeaderSearchOptions;
 class ObjCMethodDecl;
 class ObjCProtocolDecl;
const CGFunctionInfo &arrangeFreeFunctionCall(CodeGenModule &CGM,
                                               FunctionType::ExtInfo info,
                                               RequiredArgs args);
 
 /// Returns the implicit arguments to add to a complete, non-delegating C++
 /// constructor call.
 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);
 
 llvm::Type *convertTypeForMemory(CodeGenModule &CGM, QualType T);
 
 /// Given a non-bitfield struct field, return its index within the elements of
 /// the struct's converted type.  The returned index refers to a field number in

clang/lib/CodeGen/ABIInfo.h

 
 namespace clang {
   class ASTContext;
   class CodeGenOptions;
   class TargetInfo;
 
 namespace CodeGen {
   class ABIArgInfo;
-  class Address;
   class CGCXXABI;
   class CGFunctionInfo;
   class CodeGenFunction;
   class CodeGenTypes;
   class SwiftABIInfo;
 
 namespace swiftcall {
   class SwiftAggLowering;

clang/lib/CodeGen/CGCXXABI.h

public:
   ///
   /// \return The number of arguments added at the beginning and end of the
   /// call, which is typically zero or one.
   AddedStructorArgCounts
   addImplicitConstructorArgs(CodeGenFunction &CGF, const CXXConstructorDecl *D,
                              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,
                                   bool ForVirtualBase, bool Delegating,
                                   Address This, QualType ThisTy) = 0;
 
   /// Emits the VTable definitions required for the given record type.
   virtual void emitVTableDefinitions(CodeGenVTables &CGVT,

clang/lib/CodeGen/CodeGenABITypes.cpp

CodeGen::convertTypeForMemory(CodeGenModule &CGM, QualType T) {
   return CGM.getTypes().ConvertTypeForMem(T);
 }
 
 unsigned CodeGen::getLLVMFieldNumber(CodeGenModule &CGM,
                                      const RecordDecl *RD,
                                      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

public:
   void EmitInstanceFunctionProlog(CodeGenFunction &CGF) override;
 
   AddedStructorArgs getImplicitConstructorArgs(CodeGenFunction &CGF,
                                                const CXXConstructorDecl *D,
                                                CXXCtorType Type,
                                                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,
                           QualType ThisTy) override;
 
   void emitVTableDefinitions(CodeGenVTables &CGVT,
                              const CXXRecordDecl *RD) override;
 
CGCXXABI::AddedStructorArgs ItaniumCXXABI::getImplicitConstructorArgs(
 
   // Insert the implicit 'vtt' argument as the second argument.
   llvm::Value *VTT =
       CGF.GetVTTParameter(GlobalDecl(D, Type), ForVirtualBase, Delegating);
   QualType VTTTy = getContext().getPointerType(getContext().VoidPtrTy);
   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;
   if (getContext().getLangOpts().AppleKext &&
       Type != Dtor_Base && DD->isVirtual())
     Callee = CGF.BuildAppleKextVirtualDestructorCall(DD, Type, DD->getParent());
   else
     Callee = CGCallee::forDirect(CGM.getAddrOfCXXStructor(GD), GD);

clang/lib/CodeGen/MicrosoftCXXABI.cpp

public:
   void EmitInstanceFunctionProlog(CodeGenFunction &CGF) override;
 
   AddedStructorArgs getImplicitConstructorArgs(CodeGenFunction &CGF,
                                                const CXXConstructorDecl *D,
                                                CXXCtorType Type,
                                                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,
                           QualType ThisTy) override;
 
   void emitVTableTypeMetadata(const VPtrInfo &Info, const CXXRecordDecl *RD,
                               llvm::GlobalVariable *VTable);
 
if (Delegating) {
     MostDerivedArg = llvm::ConstantInt::get(CGM.Int32Ty, Type == Ctor_Complete);
   }
   if (FPT->isVariadic()) {
     return AddedStructorArgs::prefix({{MostDerivedArg, getContext().IntTy}});
   }
   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,
                                          bool Delegating, Address This,
                                          QualType ThisTy) {
   // Use the base destructor variant in place of the complete destructor variant
   // if the class has no virtual bases. This effectively implements some of the
   // -mconstructor-aliases optimization, but as part of the MS C++ ABI.
This = adjustThisArgumentForVirtualFunctionCall(CGF, GlobalDecl(DD, Type),
                                                     This, false);
   }
 
   llvm::BasicBlock *BaseDtorEndBB = nullptr;
   if (ForVirtualBase && isa<CXXConstructorDecl>(CGF.CurCodeDecl)) {
     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
     CGF.Builder.CreateBr(BaseDtorEndBB);
     CGF.EmitBlock(BaseDtorEndBB);
   }
 }