Debug Info: Clarify the documentation for bitfields emission.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@240835 91177308-0d34-0410-b5e6-96231b3b80d8
This commit is contained in:
Adrian Prantl 2015-06-26 21:27:30 +00:00
parent 110ef3ea12
commit 7cb828a34d

View File

@ -1346,6 +1346,13 @@ void DwarfUnit::constructMemberDIE(DIE &Buffer, const DIDerivedType *DT) {
addUInt(MemberDie, dwarf::DW_AT_byte_size, None, FieldSize/8);
addUInt(MemberDie, dwarf::DW_AT_bit_size, None, Size);
// The DWARF 2 DW_AT_bit_offset is counting the bits between
// the high end of the aligned storage unit containing the bit
// field to the high end of the bit field.
//
// FIXME: DWARF 4 states that DW_AT_data_bit_offset (which
// counts from the beginning, regardless of endianness) should
// be used instead.
uint64_t Offset = DT->getOffsetInBits();
uint64_t AlignMask = ~(DT->getAlignInBits() - 1);
uint64_t HiMark = (Offset + FieldSize) & AlignMask;
@ -1357,8 +1364,6 @@ void DwarfUnit::constructMemberDIE(DIE &Buffer, const DIDerivedType *DT) {
Offset = FieldSize - (Offset + Size);
addUInt(MemberDie, dwarf::DW_AT_bit_offset, None, Offset);
// Here DW_AT_data_member_location points to the anonymous
// field that includes this bit field.
OffsetInBytes = FieldOffset >> 3;
} else
// This is not a bitfield.