[ms-cxxabi] Implement member data pointers for non-dynamic classes

Summary:
For non-dynamic classes (no virtual bases), member data pointers are
simple offsets from the base of the record.  Dynamic classes use an
aggregate for member data pointers and are therefore currently
unsupported.

Unlike Itanium, the ms ABI uses 0 to represent null for polymorphic
classes.  Non-polymorphic classes use -1 like Itanium, since 0 is a
valid field offset.

Reviewers: rjmccall

CC: timurrrr, cfe-commits

Differential Revision: http://llvm-reviews.chandlerc.com/D558

llvm-svn: 177753

1 files changed, 116 insertions, 0 deletions

diff --git a/clang/lib/CodeGen/MicrosoftCXXABI.cpp b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
index 85d926023f3..00b15c9a49c 100644
--- a/clang/lib/CodeGen/MicrosoftCXXABI.cpp
+++ b/clang/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -109,6 +109,33 @@ public:
                                    llvm::Value *allocPtr,
                                    CharUnits cookieSize);
   static bool needThisReturn(GlobalDecl GD);
+
+private:
+  llvm::Constant *getSimpleNullMemberPointer(const MemberPointerType *MPT);
+
+  llvm::Constant *getZeroPtrDiff() {
+    return llvm::ConstantInt::get(CGM.PtrDiffTy, 0);
+  }
+
+  llvm::Constant *getAllOnesPtrDiff() {
+    return  llvm::Constant::getAllOnesValue(CGM.PtrDiffTy);
+  }
+
+public:
+  virtual llvm::Constant *EmitNullMemberPointer(const MemberPointerType *MPT);
+
+  virtual llvm::Constant *EmitMemberDataPointer(const MemberPointerType *MPT,
+                                                CharUnits offset);
+
+  virtual llvm::Value *EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
+                                                  llvm::Value *MemPtr,
+                                                  const MemberPointerType *MPT);
+
+  virtual llvm::Value *EmitMemberDataPointerAddress(CodeGenFunction &CGF,
+                                                    llvm::Value *Base,
+                                                    llvm::Value *MemPtr,
+                                                  const MemberPointerType *MPT);
+
 };
 
 }
@@ -352,6 +379,95 @@ 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) {
+  const CXXRecordDecl *RD = MPT->getClass()->getAsCXXRecordDecl();
+  return (MPT->isMemberDataPointer() &&
+          !MPT->getClass()->isIncompleteType() &&
+          RD->getNumVBases() == 0);
+}
+
+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();
+  }
+  return GetBogusMemberPointer(QualType(MPT, 0));
+}
+
+llvm::Constant *
+MicrosoftCXXABI::EmitNullMemberPointer(const MemberPointerType *MPT) {
+  if (isSimpleMemberPointer(MPT))
+    return getSimpleNullMemberPointer(MPT);
+  // FIXME: Implement function member pointers.
+  return GetBogusMemberPointer(QualType(MPT, 0));
+}
+
+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));
+}
+
+llvm::Value *
+MicrosoftCXXABI::EmitMemberPointerIsNotNull(CodeGenFunction &CGF,
+                                            llvm::Value *MemPtr,
+                                            const MemberPointerType *MPT) {
+  CGBuilderTy &Builder = CGF.Builder;
+
+  // 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");
+  }
+
+  // FIXME: Implement member pointers other inheritance models.
+  ErrorUnsupportedABI(CGF, "function member pointer tests");
+  return GetBogusMemberPointer(QualType(MPT, 0));
+}
+
+llvm::Value *
+MicrosoftCXXABI::EmitMemberDataPointerAddress(CodeGenFunction &CGF,
+                                              llvm::Value *Base,
+                                              llvm::Value *MemPtr,
+                                              const MemberPointerType *MPT) {
+  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);
+  }
+
+  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);
+  }
+
+  // Cast the address to the appropriate pointer type, adopting the address
+  // space of the base pointer.
+  return Builder.CreateBitCast(Addr, PType);
+}
+
 CGCXXABI *clang::CodeGen::CreateMicrosoftCXXABI(CodeGenModule &CGM) {
   return new MicrosoftCXXABI(CGM);
 }