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[BOLT] Refactor to use new APIs for getting offset of attribute
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Summary: Changing to use the new APIs for getting offset of attribute from .debug_info. They were split in to multiple ones so that Offset can be gotten seperatly.

(cherry picked from FBD30616705)
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@ayermolo @maksfb
ayermolo authored and maksfb committed Aug 27, 2021
1 parent 3e8af67 commit 23fc454
Showing 1 changed file with 76 additions and 42 deletions.
118 changes: 76 additions & 42 deletions bolt/src/DWARFRewriter.cpp
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Expand Up @@ -52,6 +52,37 @@ static void printDie(const DWARFDie &DIE) {
DIE.dump(dbgs(), 0, DumpOpts);
}

struct AttrInfo {
DWARFFormValue V;
uint64_t Offset;
};

/// Finds attributes FormValue and Offset.
///
/// \param DIE die to look up in.
/// \param Attr the attribute to extract.
/// \return an optional AttrInfo with DWARFFormValue and Offset.
Optional<AttrInfo> findAttributeInfo(const DWARFDie DIE,
dwarf::Attribute Attr) {
if (!DIE.isValid())
return None;
const DWARFAbbreviationDeclaration *AbbrevDecl =
DIE.getAbbreviationDeclarationPtr();
if (!AbbrevDecl)
return None;
Optional<uint32_t> Index = AbbrevDecl->findAttributeIndex(Attr);
if (!Index)
return None;
const DWARFUnit &U = *DIE.getDwarfUnit();
uint64_t Offset =
AbbrevDecl->getAttributeOffsetFromIndex(*Index, DIE.getOffset(), U);
Optional<DWARFFormValue> Value =
AbbrevDecl->getAttributeValueFromOffset(*Index, Offset, U);
if (!Value)
return None;
return AttrInfo{*Value, Offset};
}

using namespace llvm;
using namespace llvm::support::endian;
using namespace object;
Expand Down Expand Up @@ -173,23 +204,22 @@ void DWARFRewriter::updateDebugInfo() {

auto updateDWONameCompDir = [&](DWARFUnit &Unit) -> void {
const DWARFDie &DIE = Unit.getUnitDIE();
uint64_t AttrOffset = 0;
Optional<DWARFFormValue> ValDwoName =
DIE.find(dwarf::DW_AT_GNU_dwo_name, &AttrOffset);
(void)ValDwoName;
assert(ValDwoName && "Skeleton CU doesn't have dwo_name.");
Optional<AttrInfo> AttrInfoVal =
findAttributeInfo(DIE, dwarf::DW_AT_GNU_dwo_name);
(void)AttrInfoVal;
assert(AttrInfoVal && "Skeleton CU doesn't have dwo_name.");

std::string ObjectName = getDWOName(Unit, &NameToIndexMap, DWOIdToName);
uint32_t NewOffset = StrWriter->addString(ObjectName.c_str());
DebugInfoPatcher->addLE32Patch(AttrOffset, NewOffset);
DebugInfoPatcher->addLE32Patch(AttrInfoVal->Offset, NewOffset);

AttrInfoVal = findAttributeInfo(DIE, dwarf::DW_AT_comp_dir);
(void)AttrInfoVal;
assert(AttrInfoVal && "DW_AT_comp_dir is not in Skeleton CU.");

Optional<DWARFFormValue> ValCompDir =
DIE.find(dwarf::DW_AT_comp_dir, &AttrOffset);
(void)ValCompDir;
assert(ValCompDir && "DW_AT_comp_dir is not in Skeleton CU.");
if (!opts::DwarfOutputPath.empty()) {
uint32_t NewOffset = StrWriter->addString(opts::DwarfOutputPath.c_str());
DebugInfoPatcher->addLE32Patch(AttrOffset, NewOffset);
DebugInfoPatcher->addLE32Patch(AttrInfoVal->Offset, NewOffset);
}
};

Expand All @@ -199,19 +229,19 @@ void DWARFRewriter::updateDebugInfo() {
// .debug_info/.debug_abbrev
auto updateRangeBase = [&](DWARFUnit &Unit, uint64_t RangeBase,
bool WasRangeBaseUsed) -> void {
uint64_t AttrOffset = 0;
DWARFDie DIE = Unit.getUnitDIE();
Optional<DWARFFormValue> ValRangeBase =
DIE.find(dwarf::DW_AT_GNU_ranges_base, &AttrOffset);
bool NeedToPatch = ValRangeBase.hasValue();
Optional<AttrInfo> AttrInfoVal =
findAttributeInfo(DIE, dwarf::DW_AT_GNU_ranges_base);
bool NeedToPatch = AttrInfoVal.hasValue();
uint64_t AttrOffset = NeedToPatch ? AttrInfoVal->Offset : 0;
uint32_t PrevAbbrevOffsetModifier = AbbrevOffsetModifier;
// Case where Skeleton CU doesn't have DW_AT_GNU_ranges_base
if (!NeedToPatch && WasRangeBaseUsed) {
const DWARFAbbreviationDeclaration *AbbreviationDecl =
DIE.getAbbreviationDeclarationPtr();
if (Optional<DWARFFormValue> ValLowPC =
DIE.find(dwarf::DW_AT_low_pc, &AttrOffset)) {

if (Optional<AttrInfo> ValLowP =
findAttributeInfo(DIE, dwarf::DW_AT_low_pc)) {
AttrOffset = ValLowP->Offset;
Optional<DWARFFormValue> ValHighPC = DIE.find(dwarf::DW_AT_high_pc);
uint32_t NumBytesToFill = 7;

Expand Down Expand Up @@ -454,9 +484,10 @@ void DWARFRewriter::updateUnitDebugInfo(uint64_t CUIndex, DWARFUnit &Unit,
// Handle any tag that can have DW_AT_location attribute.
DWARFFormValue Value;
uint64_t AttrOffset;
if (Optional<DWARFFormValue> V =
DIE.find(dwarf::DW_AT_location, &AttrOffset)) {
Value = *V;
if (Optional<AttrInfo> AttrVal =
findAttributeInfo(DIE, dwarf::DW_AT_location)) {
AttrOffset = AttrVal->Offset;
Value = AttrVal->V;
if (Value.isFormClass(DWARFFormValue::FC_Constant) ||
Value.isFormClass(DWARFFormValue::FC_SectionOffset)) {
uint64_t Offset = Value.isFormClass(DWARFFormValue::FC_Constant)
Expand Down Expand Up @@ -570,9 +601,10 @@ void DWARFRewriter::updateUnitDebugInfo(uint64_t CUIndex, DWARFUnit &Unit,
}
}
}
} else if (Optional<DWARFFormValue> V =
DIE.find(dwarf::DW_AT_low_pc, &AttrOffset)) {
Value = *V;
} else if (Optional<AttrInfo> AttrVal =
findAttributeInfo(DIE, dwarf::DW_AT_low_pc)) {
AttrOffset = AttrVal->Offset;
Value = AttrVal->V;
const Optional<uint64_t> Result = Value.getAsAddress();
if (Result.hasValue()) {
const uint64_t Address = Result.getValue();
Expand Down Expand Up @@ -643,13 +675,11 @@ void DWARFRewriter::updateDWARFObjectAddressRanges(
if (AbbreviationDecl->findAttributeIndex(dwarf::DW_AT_ranges)) {
// Case 1: The object was already non-contiguous and had DW_AT_ranges.
// In this case we simply need to update the value of DW_AT_ranges.
uint64_t AttrOffset = -1U;
DIE.find(dwarf::DW_AT_ranges, &AttrOffset);
assert(AttrOffset != -1U && "failed to locate DWARF attribute");
Optional<AttrInfo> AttrVal = findAttributeInfo(DIE, dwarf::DW_AT_ranges);

std::lock_guard<std::mutex> Lock(DebugInfoPatcherMutex);
DebugInfoPatcher.addLE32Patch(
AttrOffset, DebugRangesOffset - DebugInfoPatcher.getRangeBase());
AttrVal->Offset, DebugRangesOffset - DebugInfoPatcher.getRangeBase());
} else {
// Case 2: The object has both DW_AT_low_pc and DW_AT_high_pc emitted back
// to back. We replace the attributes with DW_AT_ranges and DW_AT_low_pc.
Expand Down Expand Up @@ -711,10 +741,11 @@ void DWARFRewriter::updateLineTableOffsets() {
if (!Label)
continue;

const uint64_t LTOffset =
BC.DwCtx->getAttrFieldOffsetForUnit(CU.get(), dwarf::DW_AT_stmt_list);
if (!LTOffset)
Optional<AttrInfo> AttrVal =
findAttributeInfo(CU.get()->getUnitDIE(), dwarf::DW_AT_stmt_list);
if (!AttrVal)
continue;
const uint64_t LTOffset = AttrVal->Offset;

// Line tables are stored in MCContext in ascending order of offset in the
// output file, thus we can compute all table's offset by passing through
Expand Down Expand Up @@ -757,10 +788,11 @@ void DWARFRewriter::updateLineTableOffsets() {

for (const std::unique_ptr<DWARFUnit> &TU : BC.DwCtx->types_section_units()) {
DWARFUnit *Unit = TU.get();
const uint64_t LTOffset =
BC.DwCtx->getAttrFieldOffsetForUnit(Unit, dwarf::DW_AT_stmt_list);
if (!LTOffset)
Optional<AttrInfo> AttrVal =
findAttributeInfo(TU.get()->getUnitDIE(), dwarf::DW_AT_stmt_list);
if (!AttrVal)
continue;
const uint64_t LTOffset = AttrVal->Offset;
auto Iter = DebugLineOffsetMap.find(GetStatementListValue(Unit));
assert(Iter != DebugLineOffsetMap.end() &&
"Type Unit Updated Line Number Entry does not exist.");
Expand Down Expand Up @@ -812,11 +844,11 @@ void DWARFRewriter::finalizeDebugSections(
AddressSectionContents.size());
for (auto &CU : BC.DwCtx->compile_units()) {
DWARFDie DIE = CU->getUnitDIE();
uint64_t AttrOffset = 0;
if (Optional<DWARFFormValue> Val =
DIE.find(dwarf::DW_AT_GNU_addr_base, &AttrOffset)) {
if (Optional<AttrInfo> AttrVal =
findAttributeInfo(DIE, dwarf::DW_AT_GNU_addr_base)) {
uint64_t Offset = AddrWriter->getOffset(*CU->getDWOId());
DebugInfoPatcher.addLE32Patch(AttrOffset, static_cast<int32_t>(Offset));
DebugInfoPatcher.addLE32Patch(AttrVal->Offset,
static_cast<int32_t>(Offset));
}
}
}
Expand Down Expand Up @@ -1407,10 +1439,12 @@ namespace {
void getRangeAttrData(DWARFDie DIE, uint64_t &LowPCOffset,
uint64_t &HighPCOffset, DWARFFormValue &LowPCFormValue,
DWARFFormValue &HighPCFormValue) {
LowPCOffset = -1U;
HighPCOffset = -1U;
LowPCFormValue = *DIE.find(dwarf::DW_AT_low_pc, &LowPCOffset);
HighPCFormValue = *DIE.find(dwarf::DW_AT_high_pc, &HighPCOffset);
Optional<AttrInfo> LowPCVal = findAttributeInfo(DIE, dwarf::DW_AT_low_pc);
Optional<AttrInfo> HighPCVal = findAttributeInfo(DIE, dwarf::DW_AT_high_pc);
LowPCOffset = LowPCVal->Offset;
HighPCOffset = HighPCVal->Offset;
LowPCFormValue = LowPCVal->V;
HighPCFormValue = HighPCVal->V;

if ((LowPCFormValue.getForm() != dwarf::DW_FORM_addr &&
LowPCFormValue.getForm() != dwarf::DW_FORM_GNU_addr_index) ||
Expand Down

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