Types.cpp

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//===----------------------------------------------------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
 
#include "llvm/ABI/Types.h"
#include "llvm/Support/Casting.h"
 
using namespace llvm;
using namespace llvm::abi;
 
bool RecordType::isEmpty() const {
  if (hasFlexibleArrayMember())
    return false;
 
  // We shouldn't need to check for emptiness if the record has virtual bases
  // because it can't be passed in registers. This assertion is here to enforce
  // that assumption.
  assert(getNumVirtualBaseClasses() == 0 || !canPassInRegisters());
 
  if (getNumVirtualBaseClasses() > 0)
    return false;
 
  for (const FieldInfo &Base : getBaseClasses()) {
    const auto *BaseRT = dyn_cast<RecordType>(Base.FieldType);
    if (!BaseRT || !BaseRT->isEmpty())
      return false;
  }
 
  for (const FieldInfo &FI : getFields())
    if (!FI.isEmpty())
      return false;
 
  return true;
}
 
const FieldInfo *
RecordType::getElementContainingOffset(unsigned OffsetInBits) const {
  auto Contains = [&](const FieldInfo &Element) {
    unsigned Start = Element.OffsetInBits;
    unsigned Size = Element.FieldType->getSizeInBits().getFixedValue();
    return OffsetInBits >= Start && OffsetInBits < Start + Size;
  };
 
  for (const FieldInfo &Base : getBaseClasses()) {
    const auto *BaseRT = dyn_cast<RecordType>(Base.FieldType);
    if ((!BaseRT || !BaseRT->isEmpty()) && Contains(Base))
      return &Base;
  }
 
  for (const FieldInfo &VBase : getVirtualBaseClasses()) {
    const auto *VBaseRT = dyn_cast<RecordType>(VBase.FieldType);
    if ((!VBaseRT || !VBaseRT->isEmpty()) && Contains(VBase))
      return &VBase;
  }
 
  for (const FieldInfo &Field : getFields()) {
    if (Field.IsUnnamedBitfield)
      continue;
    if (Contains(Field))
      return &Field;
  }
 
  return nullptr;
}
 
bool FieldInfo::isEmpty() const {
  if (IsUnnamedBitfield)
    return true;
 
  const Type *Ty = FieldType;
  bool WasArray = false;
  while (const auto *AT = dyn_cast<ArrayType>(Ty)) {
    // Constant arrays of zero length always count as empty.
    if (AT->getNumElements() == 0)
      return true;
    Ty = AT->getElementType();
    WasArray = true;
  }
 
  const auto *RT = dyn_cast<RecordType>(Ty);
  if (!RT)
    return false;
 
  // C++ record fields are never empty unless [[no_unique_address]] applies.
  // That exception does not apply to arrays of C++ empty records.
  if (RT->isCXXRecord() && (WasArray || !HasNoUniqueAddress))
    return false;
 
  return RT->isEmpty();
}