[ms-cxxabi] Implement member pointer emission and dereferencing

Summary:
Handles all inheritance models for both data and function member
pointers.

Also implements isZeroInitializable() and refactors some of the null
member pointer code.

MSVC supports converting member pointers through virtual bases, which
clang does not (yet?) support.  Implementing that extension is covered
by http://llvm.org/15713

Reviewers: rjmccall

CC: cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D613

git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@179305 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 281 insertions, 52 deletions

diff --git a/lib/CodeGen/MicrosoftCXXABI.cpp b/lib/CodeGen/MicrosoftCXXABI.cpp
index 00b15c9a49..2c7f89aa50 100644
--- a/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -111,17 +111,28 @@ public:
   static bool needThisReturn(GlobalDecl GD);
 
 private:
-  llvm::Constant *getSimpleNullMemberPointer(const MemberPointerType *MPT);
-
-  llvm::Constant *getZeroPtrDiff() {
-    return llvm::ConstantInt::get(CGM.PtrDiffTy, 0);
+  llvm::Constant *getZeroInt() {
+    return llvm::ConstantInt::get(CGM.IntTy, 0);
   }
 
-  llvm::Constant *getAllOnesPtrDiff() {
-    return  llvm::Constant::getAllOnesValue(CGM.PtrDiffTy);
+  llvm::Constant *getAllOnesInt() {
+    return  llvm::Constant::getAllOnesValue(CGM.IntTy);
   }
 
+  void
+  GetNullMemberPointerFields(const MemberPointerType *MPT,
+                             llvm::SmallVectorImpl<llvm::Constant *> &fields);
+
+  llvm::Value *AdjustVirtualBase(CodeGenFunction &CGF, const CXXRecordDecl *RD,
+                                 llvm::Value *Base,
+                                 llvm::Value *VirtualBaseAdjustmentOffset,
+                                 llvm::Value *VBPtrOffset /* optional */);
+
 public:
+  virtual llvm::Type *ConvertMemberPointerType(const MemberPointerType *MPT);
+
+  virtual bool isZeroInitializable(const MemberPointerType *MPT);
+
   virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
 
   virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
@@ -136,6 +147,12 @@ public:
                                                     llvm::Value *MemPtr,
                                                   const MemberPointerType *MPT);
 
+  virtual llvm::Value *
+  EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
+                                  llvm::Value *&This,
+                                  llvm::Value *MemPtr,
+                                  const MemberPointerType *MPT);
+
 };
 
 }
@@ -379,45 +396,125 @@ void MicrosoftCXXABI::EmitGuardedInit(CodeGenFunction &CGF, const VarDecl &D,
   CGF.EmitCXXGlobalVarDeclInit(D, DeclPtr, PerformInit);
 }
 
-// Returns true for member pointer types that we know how to represent with a
-// simple ptrdiff_t.  Currently we only know how to emit, test, and load member
-// data pointers for complete single inheritance classes.
-static bool isSimpleMemberPointer(const MemberPointerType *MPT) {
+// Member pointer helpers.
+static bool hasVBPtrOffsetField(MSInheritanceModel Inheritance) {
+  return Inheritance == MSIM_Unspecified;
+}
+
+// Only member pointers to functions need a this adjustment, since it can be
+// combined with the field offset for data pointers.
+static bool hasNonVirtualBaseAdjustmentField(const MemberPointerType *MPT,
+                                             MSInheritanceModel Inheritance) {
+  return (MPT->isMemberFunctionPointer() &&
+          Inheritance >= MSIM_Multiple);
+}
+
+static bool hasVirtualBaseAdjustmentField(MSInheritanceModel Inheritance) {
+  return Inheritance >= MSIM_Virtual;
+}
+
+// Use zero for the field offset of a null data member pointer if we can
+// guarantee that zero is not a valid field offset, or if the member pointer has
+// multiple fields.  Polymorphic classes have a vfptr at offset zero, so we can
+// use zero for null.  If there are multiple fields, we can use zero even if it
+// is a valid field offset because null-ness testing will check the other
+// fields.
+static bool nullFieldOffsetIsZero(MSInheritanceModel Inheritance) {
+  return Inheritance != MSIM_Multiple && Inheritance != MSIM_Single;
+}
+
+bool MicrosoftCXXABI::isZeroInitializable(const MemberPointerType *MPT) {
+  // Null-ness for function memptrs only depends on the first field, which is
+  // the function pointer.  The rest don't matter, so we can zero initialize.
+  if (MPT->isMemberFunctionPointer())
+    return true;
+
+  // The virtual base adjustment field is always -1 for null, so if we have one
+  // we can't zero initialize.  The field offset is sometimes also -1 if 0 is a
+  // valid field offset.
   const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
-  return (MPT->isMemberDataPointer() &&
-          !MPT->getClass()->isIncompleteType() &&
-          RD->getNumVBases() == 0);
+  MSInheritanceModel Inheritance = RD->getMSInheritanceModel();
+  return (!hasVirtualBaseAdjustmentField(Inheritance) &&
+          nullFieldOffsetIsZero(Inheritance));
 }
 
-llvm::Constant *
-MicrosoftCXXABI::getSimpleNullMemberPointer(const MemberPointerType *MPT) {
-  if (isSimpleMemberPointer(MPT)) {
-    const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
-    // A null member data pointer is represented as -1 if the class is not
-    // polymorphic, and 0 otherwise.
-    if (RD->isPolymorphic())
-      return getZeroPtrDiff();
-    return getAllOnesPtrDiff();
+llvm::Type *
+MicrosoftCXXABI::ConvertMemberPointerType(const MemberPointerType *MPT) {
+  const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
+  MSInheritanceModel Inheritance = RD->getMSInheritanceModel();
+  llvm::SmallVector<llvm::Type *, 4> fields;
+  if (MPT->isMemberFunctionPointer())
+    fields.push_back(CGM.VoidPtrTy);  // FunctionPointerOrVirtualThunk
+  else
+    fields.push_back(CGM.IntTy);  // FieldOffset
+
+  if (hasVBPtrOffsetField(Inheritance))
+    fields.push_back(CGM.IntTy);
+  if (hasNonVirtualBaseAdjustmentField(MPT, Inheritance))
+    fields.push_back(CGM.IntTy);
+  if (hasVirtualBaseAdjustmentField(Inheritance))
+    fields.push_back(CGM.IntTy);  // VirtualBaseAdjustmentOffset
+
+  if (fields.size() == 1)
+    return fields[0];
+  return llvm::StructType::get(CGM.getLLVMContext(), fields);
+}
+
+void MicrosoftCXXABI::
+GetNullMemberPointerFields(const MemberPointerType *MPT,
+                           llvm::SmallVectorImpl<llvm::Constant *> &fields) {
+  assert(fields.empty());
+  const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
+  MSInheritanceModel Inheritance = RD->getMSInheritanceModel();
+  if (MPT->isMemberFunctionPointer()) {
+    // FunctionPointerOrVirtualThunk
+    fields.push_back(llvm::Constant::getNullValue(CGM.VoidPtrTy));
+  } else {
+    if (nullFieldOffsetIsZero(Inheritance))
+      fields.push_back(getZeroInt());  // FieldOffset
+    else
+      fields.push_back(getAllOnesInt());  // FieldOffset
   }
-  return GetBogusMemberPointer(QualType(MPT, 0));
+
+  if (hasVBPtrOffsetField(Inheritance))
+    fields.push_back(getZeroInt());
+  if (hasNonVirtualBaseAdjustmentField(MPT, Inheritance))
+    fields.push_back(getZeroInt());
+  if (hasVirtualBaseAdjustmentField(Inheritance))
+    fields.push_back(getAllOnesInt());
 }
 
 llvm::Constant *
 MicrosoftCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
-  if (isSimpleMemberPointer(MPT))
-    return getSimpleNullMemberPointer(MPT);
-  // FIXME: Implement function member pointers.
-  return GetBogusMemberPointer(QualType(MPT, 0));
+  llvm::SmallVector<llvm::Constant *, 4> fields;
+  GetNullMemberPointerFields(MPT, fields);
+  if (fields.size() == 1)
+    return fields[0];
+  llvm::Constant *Res = llvm::ConstantStruct::getAnon(fields);
+  assert(Res->getType() == ConvertMemberPointerType(MPT));
+  return Res;
 }
 
 llvm::Constant *
 MicrosoftCXXABI::EmitMemberDataPointer(const MemberPointerType *MPT,
                                        CharUnits offset) {
-  // Member data pointers are plain offsets when no virtual bases are involved.
-  if (isSimpleMemberPointer(MPT))
-    return llvm::ConstantInt::get(CGM.PtrDiffTy, offset.getQuantity());
-  // FIXME: Implement member pointers other inheritance models.
-  return GetBogusMemberPointer(QualType(MPT, 0));
+  const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
+  MSInheritanceModel Inheritance = RD->getMSInheritanceModel();
+  llvm::SmallVector<llvm::Constant *, 4> fields;
+  fields.push_back(llvm::ConstantInt::get(CGM.IntTy, offset.getQuantity()));
+  if (hasVBPtrOffsetField(Inheritance)) {
+    int64_t VBPtrOffset =
+      getContext().getASTRecordLayout(RD).getVBPtrOffset().getQuantity();
+    fields.push_back(llvm::ConstantInt::get(CGM.IntTy, VBPtrOffset));
+  }
+  assert(!hasNonVirtualBaseAdjustmentField(MPT, Inheritance));
+  // The virtual base field starts out zero.  It is adjusted by conversions to
+  // member pointer types of a more derived class.  See http://llvm.org/PR15713
+  if (hasVirtualBaseAdjustmentField(Inheritance))
+    fields.push_back(getZeroInt());
+  if (fields.size() == 1)
+    return fields[0];
+  return llvm::ConstantStruct::getAnon(fields);
 }
 
 llvm::Value *
@@ -425,16 +522,90 @@ MicrosoftCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
                                             llvm::Value *MemPtr,
                                             const MemberPointerType *MPT) {
   CGBuilderTy &Builder = CGF.Builder;
+  llvm::SmallVector<llvm::Constant *, 4> fields;
+  // We only need one field for member functions.
+  if (MPT->isMemberFunctionPointer())
+    fields.push_back(llvm::Constant::getNullValue(CGM.VoidPtrTy));
+  else
+    GetNullMemberPointerFields(MPT, fields);
+  assert(!fields.empty());
+  llvm::Value *FirstField = MemPtr;
+  if (MemPtr->getType()->isStructTy())
+    FirstField = Builder.CreateExtractValue(MemPtr, 0);
+  llvm::Value *Res = Builder.CreateICmpNE(FirstField, fields[0], "memptr.cmp0");
+
+  // For function member pointers, we only need to test the function pointer
+  // field.  The other fields if any can be garbage.
+  if (MPT->isMemberFunctionPointer())
+    return Res;
+
+  // Otherwise, emit a series of compares and combine the results.
+  for (int I = 1, E = fields.size(); I < E; ++I) {
+    llvm::Value *Field = Builder.CreateExtractValue(MemPtr, I);
+    llvm::Value *Next = Builder.CreateICmpNE(Field, fields[I], "memptr.cmp");
+    Res = Builder.CreateAnd(Res, Next, "memptr.tobool");
+  }
+  return Res;
+}
 
-  // For member data pointers, this is just a check against -1 or 0.
-  if (isSimpleMemberPointer(MPT)) {
-    llvm::Constant *Val = getSimpleNullMemberPointer(MPT);
-    return Builder.CreateICmpNE(MemPtr, Val, "memptr.tobool");
+// Returns an adjusted base cast to i8*, since we do more address arithmetic on
+// it.
+llvm::Value *
+MicrosoftCXXABI::AdjustVirtualBase(CodeGenFunction &CGF,
+                                   const CXXRecordDecl *RD, llvm::Value *Base,
+                                   llvm::Value *VirtualBaseAdjustmentOffset,
+                                   llvm::Value *VBPtrOffset) {
+  CGBuilderTy &Builder = CGF.Builder;
+  Base = Builder.CreateBitCast(Base, CGM.Int8PtrTy);
+  llvm::BasicBlock *OriginalBB = 0;
+  llvm::BasicBlock *SkipAdjustBB = 0;
+  llvm::BasicBlock *VBaseAdjustBB = 0;
+
+  // In the unspecified inheritance model, there might not be a vbtable at all,
+  // in which case we need to skip the virtual base lookup.  If there is a
+  // vbtable, the first entry is a no-op entry that gives back the original
+  // base, so look for a virtual base adjustment offset of zero.
+  if (VBPtrOffset) {
+    OriginalBB = Builder.GetInsertBlock();
+    VBaseAdjustBB = CGF.createBasicBlock("memptr.vadjust");
+    SkipAdjustBB = CGF.createBasicBlock("memptr.skip_vadjust");
+    llvm::Value *IsVirtual =
+      Builder.CreateICmpNE(VirtualBaseAdjustmentOffset, getZeroInt(),
+                           "memptr.is_vbase");
+    Builder.CreateCondBr(IsVirtual, VBaseAdjustBB, SkipAdjustBB);
+    CGF.EmitBlock(VBaseAdjustBB);
   }
 
-  // FIXME: Implement member pointers other inheritance models.
-  ErrorUnsupportedABI(CGF, "function member pointer tests");
-  return GetBogusMemberPointer(QualType(MPT, 0));
+  // If we weren't given a dynamic vbptr offset, RD should be complete and we'll
+  // know the vbptr offset.
+  if (!VBPtrOffset) {
+    CharUnits offs = getContext().getASTRecordLayout(RD).getVBPtrOffset();
+    VBPtrOffset = llvm::ConstantInt::get(CGM.IntTy, offs.getQuantity());
+  }
+  // Load the vbtable pointer from the vbtable offset in the instance.
+  llvm::Value *VBPtr =
+    Builder.CreateInBoundsGEP(Base, VBPtrOffset, "memptr.vbptr");
+  llvm::Value *VBTable =
+    Builder.CreateBitCast(VBPtr, CGM.Int8PtrTy->getPointerTo(0));
+  VBTable = Builder.CreateLoad(VBTable, "memptr.vbtable");
+  // Load an i32 offset from the vb-table.
+  llvm::Value *VBaseOffs =
+    Builder.CreateInBoundsGEP(VBTable, VirtualBaseAdjustmentOffset);
+  VBaseOffs = Builder.CreateBitCast(VBaseOffs, CGM.Int32Ty->getPointerTo(0));
+  VBaseOffs = Builder.CreateLoad(VBaseOffs, "memptr.vbase_offs");
+  // Add it to VBPtr.  GEP will sign extend the i32 value for us.
+  llvm::Value *AdjustedBase = Builder.CreateInBoundsGEP(VBPtr, VBaseOffs);
+
+  // Merge control flow with the case where we didn't have to adjust.
+  if (VBaseAdjustBB) {
+    Builder.CreateBr(SkipAdjustBB);
+    CGF.EmitBlock(SkipAdjustBB);
+    llvm::PHINode *Phi = Builder.CreatePHI(CGM.Int8PtrTy, 2, "memptr.base");
+    Phi->addIncoming(Base, OriginalBB);
+    Phi->addIncoming(AdjustedBase, VBaseAdjustBB);
+    return Phi;
+  }
+  return AdjustedBase;
 }
 
 llvm::Value *
@@ -442,32 +613,90 @@ MicrosoftCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF,
                                               llvm::Value *Base,
                                               llvm::Value *MemPtr,
                                               const MemberPointerType *MPT) {
+  assert(MPT->isMemberDataPointer());
   unsigned AS = Base->getType()->getPointerAddressSpace();
   llvm::Type *PType =
       CGF.ConvertTypeForMem(MPT->getPointeeType())->getPointerTo(AS);
   CGBuilderTy &Builder = CGF.Builder;
-
-  if (MPT->isMemberFunctionPointer()) {
-    ErrorUnsupportedABI(CGF, "function member pointer address");
-    return llvm::Constant::getNullValue(PType);
+  const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
+  MSInheritanceModel Inheritance = RD->getMSInheritanceModel();
+
+  // Extract the fields we need, regardless of model.  We'll apply them if we
+  // have them.
+  llvm::Value *FieldOffset = MemPtr;
+  llvm::Value *VirtualBaseAdjustmentOffset = 0;
+  llvm::Value *VBPtrOffset = 0;
+  if (MemPtr->getType()->isStructTy()) {
+    // We need to extract values.
+    unsigned I = 0;
+    FieldOffset = Builder.CreateExtractValue(MemPtr, I++);
+    if (hasVBPtrOffsetField(Inheritance))
+      VBPtrOffset = Builder.CreateExtractValue(MemPtr, I++);
+    if (hasVirtualBaseAdjustmentField(Inheritance))
+      VirtualBaseAdjustmentOffset = Builder.CreateExtractValue(MemPtr, I++);
   }
 
-  llvm::Value *Addr;
-  if (isSimpleMemberPointer(MPT)) {
-    // Add the offset with GEP and i8*.
-    assert(MemPtr->getType() == CGM.PtrDiffTy);
-    Base = Builder.CreateBitCast(Base, Builder.getInt8Ty()->getPointerTo(AS));
-    Addr = Builder.CreateInBoundsGEP(Base, MemPtr, "memptr.offset");
-  } else {
-    ErrorUnsupportedABI(CGF, "non-scalar member pointers");
-    return llvm::Constant::getNullValue(PType);
+  if (VirtualBaseAdjustmentOffset) {
+    Base = AdjustVirtualBase(CGF, RD, Base, VirtualBaseAdjustmentOffset,
+                             VBPtrOffset);
   }
+  llvm::Value *Addr =
+    Builder.CreateInBoundsGEP(Base, FieldOffset, "memptr.offset");
 
   // Cast the address to the appropriate pointer type, adopting the address
   // space of the base pointer.
   return Builder.CreateBitCast(Addr, PType);
 }
 
+llvm::Value *
+MicrosoftCXXABI::EmitLoadOfMemberFunctionPointer(CodeGenFunction &CGF,
+                                                 llvm::Value *&This,
+                                                 llvm::Value *MemPtr,
+                                                 const MemberPointerType *MPT) {
+  assert(MPT->isMemberFunctionPointer());
+  const FunctionProtoType *FPT =
+    MPT->getPointeeType()->castAs<FunctionProtoType>();
+  const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
+  llvm::FunctionType *FTy =
+    CGM.getTypes().GetFunctionType(
+      CGM.getTypes().arrangeCXXMethodType(RD, FPT));
+  CGBuilderTy &Builder = CGF.Builder;
+
+  MSInheritanceModel Inheritance = RD->getMSInheritanceModel();
+
+  // Extract the fields we need, regardless of model.  We'll apply them if we
+  // have them.
+  llvm::Value *FunctionPointer = MemPtr;
+  llvm::Value *NonVirtualBaseAdjustment = NULL;
+  llvm::Value *VirtualBaseAdjustmentOffset = NULL;
+  llvm::Value *VBPtrOffset = NULL;
+  if (MemPtr->getType()->isStructTy()) {
+    // We need to extract values.
+    unsigned I = 0;
+    FunctionPointer = Builder.CreateExtractValue(MemPtr, I++);
+    if (hasVBPtrOffsetField(Inheritance))
+      VBPtrOffset = Builder.CreateExtractValue(MemPtr, I++);
+    if (hasNonVirtualBaseAdjustmentField(MPT, Inheritance))
+      NonVirtualBaseAdjustment = Builder.CreateExtractValue(MemPtr, I++);
+    if (hasVirtualBaseAdjustmentField(Inheritance))
+      VirtualBaseAdjustmentOffset = Builder.CreateExtractValue(MemPtr, I++);
+  }
+
+  if (VirtualBaseAdjustmentOffset) {
+    This = AdjustVirtualBase(CGF, RD, This, VirtualBaseAdjustmentOffset,
+                             VBPtrOffset);
+  }
+
+  if (NonVirtualBaseAdjustment) {
+    // Apply the adjustment and cast back to the original struct type.
+    llvm::Value *Ptr = Builder.CreateBitCast(This, Builder.getInt8PtrTy());
+    Ptr = Builder.CreateInBoundsGEP(Ptr, NonVirtualBaseAdjustment);
+    This = Builder.CreateBitCast(Ptr, This->getType(), "this.adjusted");
+  }
+
+  return Builder.CreateBitCast(FunctionPointer, FTy->getPointerTo());
+}
+
 CGCXXABI *clang::CodeGen::CreateMicrosoftCXXABI(CodeGenModule &CGM) {
   return new MicrosoftCXXABI(CGM);
 }