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//===- llvm/CodeGen/DwarfDebug.cpp - Dwarf Debug Framework ----------------===//
//
// 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
//
//===----------------------------------------------------------------------===//
//
// This file contains support for writing dwarf debug info into asm files.
//
//===----------------------------------------------------------------------===//
#include "DwarfDebug.h"
#include "ByteStreamer.h"
#include "DIEHash.h"
#include "DebugLocEntry.h"
#include "DebugLocStream.h"
#include "DwarfCompileUnit.h"
#include "DwarfExpression.h"
#include "DwarfFile.h"
#include "DwarfUnit.h"
#include "llvm/ADT/APInt.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/MapVector.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/Triple.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/CodeGen/AccelTable.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/DIE.h"
#include "llvm/CodeGen/LexicalScopes.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineInstr.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineOperand.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetLowering.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/CodeGen/TargetSubtargetInfo.h"
#include "llvm/DebugInfo/DWARF/DWARFExpression.h"
#include "llvm/DebugInfo/DWARF/DWARFDataExtractor.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DebugInfoMetadata.h"
#include "llvm/IR/DebugLoc.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCTargetOptions.h"
#include "llvm/MC/MachineLocation.h"
#include "llvm/MC/SectionKind.h"
#include "llvm/Pass.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MD5.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Timer.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetLoweringObjectFile.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include <algorithm>
#include <cassert>
#include <cstddef>
#include <cstdint>
#include <iterator>
#include <string>
#include <utility>
#include <vector>
using namespace llvm;
#define DEBUG_TYPE "dwarfdebug"
STATISTIC(NumCSParams, "Number of dbg call site params created");
static cl::opt<bool>
DisableDebugInfoPrinting("disable-debug-info-print", cl::Hidden,
cl::desc("Disable debug info printing"));
static cl::opt<bool> UseDwarfRangesBaseAddressSpecifier(
"use-dwarf-ranges-base-address-specifier", cl::Hidden,
cl::desc("Use base address specifiers in debug_ranges"), cl::init(false));
static cl::opt<bool> GenerateARangeSection("generate-arange-section",
cl::Hidden,
cl::desc("Generate dwarf aranges"),
cl::init(false));
static cl::opt<bool>
GenerateDwarfTypeUnits("generate-type-units", cl::Hidden,
cl::desc("Generate DWARF4 type units."),
cl::init(false));
static cl::opt<bool> SplitDwarfCrossCuReferences(
"split-dwarf-cross-cu-references", cl::Hidden,
cl::desc("Enable cross-cu references in DWO files"), cl::init(false));
enum DefaultOnOff { Default, Enable, Disable };
static cl::opt<DefaultOnOff> UnknownLocations(
"use-unknown-locations", cl::Hidden,
cl::desc("Make an absence of debug location information explicit."),
cl::values(clEnumVal(Default, "At top of block or after label"),
clEnumVal(Enable, "In all cases"), clEnumVal(Disable, "Never")),
cl::init(Default));
static cl::opt<AccelTableKind> AccelTables(
"accel-tables", cl::Hidden, cl::desc("Output dwarf accelerator tables."),
cl::values(clEnumValN(AccelTableKind::Default, "Default",
"Default for platform"),
clEnumValN(AccelTableKind::None, "Disable", "Disabled."),
clEnumValN(AccelTableKind::Apple, "Apple", "Apple"),
clEnumValN(AccelTableKind::Dwarf, "Dwarf", "DWARF")),
cl::init(AccelTableKind::Default));
static cl::opt<DefaultOnOff>
DwarfInlinedStrings("dwarf-inlined-strings", cl::Hidden,
cl::desc("Use inlined strings rather than string section."),
cl::values(clEnumVal(Default, "Default for platform"),
clEnumVal(Enable, "Enabled"),
clEnumVal(Disable, "Disabled")),
cl::init(Default));
static cl::opt<bool>
NoDwarfRangesSection("no-dwarf-ranges-section", cl::Hidden,
cl::desc("Disable emission .debug_ranges section."),
cl::init(false));
static cl::opt<DefaultOnOff> DwarfSectionsAsReferences(
"dwarf-sections-as-references", cl::Hidden,
cl::desc("Use sections+offset as references rather than labels."),
cl::values(clEnumVal(Default, "Default for platform"),
clEnumVal(Enable, "Enabled"), clEnumVal(Disable, "Disabled")),
cl::init(Default));
enum LinkageNameOption {
DefaultLinkageNames,
AllLinkageNames,
AbstractLinkageNames
};
static cl::opt<LinkageNameOption>
DwarfLinkageNames("dwarf-linkage-names", cl::Hidden,
cl::desc("Which DWARF linkage-name attributes to emit."),
cl::values(clEnumValN(DefaultLinkageNames, "Default",
"Default for platform"),
clEnumValN(AllLinkageNames, "All", "All"),
clEnumValN(AbstractLinkageNames, "Abstract",
"Abstract subprograms")),
cl::init(DefaultLinkageNames));
static const char *const DWARFGroupName = "dwarf";
static const char *const DWARFGroupDescription = "DWARF Emission";
static const char *const DbgTimerName = "writer";
static const char *const DbgTimerDescription = "DWARF Debug Writer";
static constexpr unsigned ULEB128PadSize = 4;
void DebugLocDwarfExpression::emitOp(uint8_t Op, const char *Comment) {
getActiveStreamer().EmitInt8(
Op, Comment ? Twine(Comment) + " " + dwarf::OperationEncodingString(Op)
: dwarf::OperationEncodingString(Op));
}
void DebugLocDwarfExpression::emitSigned(int64_t Value) {
getActiveStreamer().EmitSLEB128(Value, Twine(Value));
}
void DebugLocDwarfExpression::emitUnsigned(uint64_t Value) {
getActiveStreamer().EmitULEB128(Value, Twine(Value));
}
void DebugLocDwarfExpression::emitData1(uint8_t Value) {
getActiveStreamer().EmitInt8(Value, Twine(Value));
}
void DebugLocDwarfExpression::emitBaseTypeRef(uint64_t Idx) {
assert(Idx < (1ULL << (ULEB128PadSize * 7)) && "Idx wont fit");
getActiveStreamer().EmitULEB128(Idx, Twine(Idx), ULEB128PadSize);
}
bool DebugLocDwarfExpression::isFrameRegister(const TargetRegisterInfo &TRI,
unsigned MachineReg) {
// This information is not available while emitting .debug_loc entries.
return false;
}
void DebugLocDwarfExpression::enableTemporaryBuffer() {
assert(!IsBuffering && "Already buffering?");
if (!TmpBuf)
TmpBuf = std::make_unique<TempBuffer>(OutBS.GenerateComments);
IsBuffering = true;
}
void DebugLocDwarfExpression::disableTemporaryBuffer() { IsBuffering = false; }
unsigned DebugLocDwarfExpression::getTemporaryBufferSize() {
return TmpBuf ? TmpBuf->Bytes.size() : 0;
}
void DebugLocDwarfExpression::commitTemporaryBuffer() {
if (!TmpBuf)
return;
for (auto Byte : enumerate(TmpBuf->Bytes)) {
const char *Comment = (Byte.index() < TmpBuf->Comments.size())
? TmpBuf->Comments[Byte.index()].c_str()
: "";
OutBS.EmitInt8(Byte.value(), Comment);
}
TmpBuf->Bytes.clear();
TmpBuf->Comments.clear();
}
const DIType *DbgVariable::getType() const {
return getVariable()->getType();
}
/// Get .debug_loc entry for the instruction range starting at MI.
static DbgValueLoc getDebugLocValue(const MachineInstr *MI) {
const DIExpression *Expr = MI->getDebugExpression();
assert(MI->getNumOperands() == 4);
if (MI->getOperand(0).isReg()) {
auto RegOp = MI->getOperand(0);
auto Op1 = MI->getOperand(1);
// If the second operand is an immediate, this is a
// register-indirect address.
assert((!Op1.isImm() || (Op1.getImm() == 0)) && "unexpected offset");
MachineLocation MLoc(RegOp.getReg(), Op1.isImm());
return DbgValueLoc(Expr, MLoc);
}
if (MI->getOperand(0).isTargetIndex()) {
auto Op = MI->getOperand(0);
return DbgValueLoc(Expr,
TargetIndexLocation(Op.getIndex(), Op.getOffset()));
}
if (MI->getOperand(0).isImm())
return DbgValueLoc(Expr, MI->getOperand(0).getImm());
if (MI->getOperand(0).isFPImm())
return DbgValueLoc(Expr, MI->getOperand(0).getFPImm());
if (MI->getOperand(0).isCImm())
return DbgValueLoc(Expr, MI->getOperand(0).getCImm());
llvm_unreachable("Unexpected 4-operand DBG_VALUE instruction!");
}
void DbgVariable::initializeDbgValue(const MachineInstr *DbgValue) {
assert(FrameIndexExprs.empty() && "Already initialized?");
assert(!ValueLoc.get() && "Already initialized?");
assert(getVariable() == DbgValue->getDebugVariable() && "Wrong variable");
assert(getInlinedAt() == DbgValue->getDebugLoc()->getInlinedAt() &&
"Wrong inlined-at");
ValueLoc = std::make_unique<DbgValueLoc>(getDebugLocValue(DbgValue));
if (auto *E = DbgValue->getDebugExpression())
if (E->getNumElements())
FrameIndexExprs.push_back({0, E});
}
ArrayRef<DbgVariable::FrameIndexExpr> DbgVariable::getFrameIndexExprs() const {
if (FrameIndexExprs.size() == 1)
return FrameIndexExprs;
assert(llvm::all_of(FrameIndexExprs,
[](const FrameIndexExpr &A) {
return A.Expr->isFragment();
}) &&
"multiple FI expressions without DW_OP_LLVM_fragment");
llvm::sort(FrameIndexExprs,
[](const FrameIndexExpr &A, const FrameIndexExpr &B) -> bool {
return A.Expr->getFragmentInfo()->OffsetInBits <
B.Expr->getFragmentInfo()->OffsetInBits;
});
return FrameIndexExprs;
}
void DbgVariable::addMMIEntry(const DbgVariable &V) {
assert(DebugLocListIndex == ~0U && !ValueLoc.get() && "not an MMI entry");
assert(V.DebugLocListIndex == ~0U && !V.ValueLoc.get() && "not an MMI entry");
assert(V.getVariable() == getVariable() && "conflicting variable");
assert(V.getInlinedAt() == getInlinedAt() && "conflicting inlined-at location");
assert(!FrameIndexExprs.empty() && "Expected an MMI entry");
assert(!V.FrameIndexExprs.empty() && "Expected an MMI entry");
// FIXME: This logic should not be necessary anymore, as we now have proper
// deduplication. However, without it, we currently run into the assertion
// below, which means that we are likely dealing with broken input, i.e. two
// non-fragment entries for the same variable at different frame indices.
if (FrameIndexExprs.size()) {
auto *Expr = FrameIndexExprs.back().Expr;
if (!Expr || !Expr->isFragment())
return;
}
for (const auto &FIE : V.FrameIndexExprs)
// Ignore duplicate entries.
if (llvm::none_of(FrameIndexExprs, [&](const FrameIndexExpr &Other) {
return FIE.FI == Other.FI && FIE.Expr == Other.Expr;
}))
FrameIndexExprs.push_back(FIE);
assert((FrameIndexExprs.size() == 1 ||
llvm::all_of(FrameIndexExprs,
[](FrameIndexExpr &FIE) {
return FIE.Expr && FIE.Expr->isFragment();
})) &&
"conflicting locations for variable");
}
static AccelTableKind computeAccelTableKind(unsigned DwarfVersion,
bool GenerateTypeUnits,
DebuggerKind Tuning,
const Triple &TT) {
// Honor an explicit request.
if (AccelTables != AccelTableKind::Default)
return AccelTables;
// Accelerator tables with type units are currently not supported.
if (GenerateTypeUnits)
return AccelTableKind::None;
// Accelerator tables get emitted if targetting DWARF v5 or LLDB. DWARF v5
// always implies debug_names. For lower standard versions we use apple
// accelerator tables on apple platforms and debug_names elsewhere.
if (DwarfVersion >= 5)
return AccelTableKind::Dwarf;
if (Tuning == DebuggerKind::LLDB)
return TT.isOSBinFormatMachO() ? AccelTableKind::Apple
: AccelTableKind::Dwarf;
return AccelTableKind::None;
}
DwarfDebug::DwarfDebug(AsmPrinter *A, Module *M)
: DebugHandlerBase(A), DebugLocs(A->OutStreamer->isVerboseAsm()),
InfoHolder(A, "info_string", DIEValueAllocator),
SkeletonHolder(A, "skel_string", DIEValueAllocator),
IsDarwin(A->TM.getTargetTriple().isOSDarwin()) {
const Triple &TT = Asm->TM.getTargetTriple();
// Make sure we know our "debugger tuning". The target option takes
// precedence; fall back to triple-based defaults.
if (Asm->TM.Options.DebuggerTuning != DebuggerKind::Default)
DebuggerTuning = Asm->TM.Options.DebuggerTuning;
else if (IsDarwin)
DebuggerTuning = DebuggerKind::LLDB;
else if (TT.isPS4CPU())
DebuggerTuning = DebuggerKind::SCE;
else
DebuggerTuning = DebuggerKind::GDB;
if (DwarfInlinedStrings == Default)
UseInlineStrings = TT.isNVPTX();
else
UseInlineStrings = DwarfInlinedStrings == Enable;
UseLocSection = !TT.isNVPTX();
HasAppleExtensionAttributes = tuneForLLDB();
// Handle split DWARF.
HasSplitDwarf = !Asm->TM.Options.MCOptions.SplitDwarfFile.empty();
// SCE defaults to linkage names only for abstract subprograms.
if (DwarfLinkageNames == DefaultLinkageNames)
UseAllLinkageNames = !tuneForSCE();
else
UseAllLinkageNames = DwarfLinkageNames == AllLinkageNames;
unsigned DwarfVersionNumber = Asm->TM.Options.MCOptions.DwarfVersion;
unsigned DwarfVersion = DwarfVersionNumber ? DwarfVersionNumber
: MMI->getModule()->getDwarfVersion();
// Use dwarf 4 by default if nothing is requested. For NVPTX, use dwarf 2.
DwarfVersion =
TT.isNVPTX() ? 2 : (DwarfVersion ? DwarfVersion : dwarf::DWARF_VERSION);
UseRangesSection = !NoDwarfRangesSection && !TT.isNVPTX();
// Use sections as references. Force for NVPTX.
if (DwarfSectionsAsReferences == Default)
UseSectionsAsReferences = TT.isNVPTX();
else
UseSectionsAsReferences = DwarfSectionsAsReferences == Enable;
// Don't generate type units for unsupported object file formats.
GenerateTypeUnits =
A->TM.getTargetTriple().isOSBinFormatELF() && GenerateDwarfTypeUnits;
TheAccelTableKind = computeAccelTableKind(
DwarfVersion, GenerateTypeUnits, DebuggerTuning, A->TM.getTargetTriple());
// Work around a GDB bug. GDB doesn't support the standard opcode;
// SCE doesn't support GNU's; LLDB prefers the standard opcode, which
// is defined as of DWARF 3.
// See GDB bug 11616 - DW_OP_form_tls_address is unimplemented
// https://sourceware.org/bugzilla/show_bug.cgi?id=11616
UseGNUTLSOpcode = tuneForGDB() || DwarfVersion < 3;
// GDB does not fully support the DWARF 4 representation for bitfields.
UseDWARF2Bitfields = (DwarfVersion < 4) || tuneForGDB();
// The DWARF v5 string offsets table has - possibly shared - contributions
// from each compile and type unit each preceded by a header. The string
// offsets table used by the pre-DWARF v5 split-DWARF implementation uses
// a monolithic string offsets table without any header.
UseSegmentedStringOffsetsTable = DwarfVersion >= 5;
Asm->OutStreamer->getContext().setDwarfVersion(DwarfVersion);
}
// Define out of line so we don't have to include DwarfUnit.h in DwarfDebug.h.
DwarfDebug::~DwarfDebug() = default;
static bool isObjCClass(StringRef Name) {
return Name.startswith("+") || Name.startswith("-");
}
static bool hasObjCCategory(StringRef Name) {
if (!isObjCClass(Name))
return false;
return Name.find(") ") != StringRef::npos;
}
static void getObjCClassCategory(StringRef In, StringRef &Class,
StringRef &Category) {
if (!hasObjCCategory(In)) {
Class = In.slice(In.find('[') + 1, In.find(' '));
Category = "";
return;
}
Class = In.slice(In.find('[') + 1, In.find('('));
Category = In.slice(In.find('[') + 1, In.find(' '));
}
static StringRef getObjCMethodName(StringRef In) {
return In.slice(In.find(' ') + 1, In.find(']'));
}
// Add the various names to the Dwarf accelerator table names.
void DwarfDebug::addSubprogramNames(const DICompileUnit &CU,
const DISubprogram *SP, DIE &Die) {
if (getAccelTableKind() != AccelTableKind::Apple &&
CU.getNameTableKind() == DICompileUnit::DebugNameTableKind::None)
return;
if (!SP->isDefinition())
return;
if (SP->getName() != "")
addAccelName(CU, SP->getName(), Die);
// If the linkage name is different than the name, go ahead and output that as
// well into the name table. Only do that if we are going to actually emit
// that name.
if (SP->getLinkageName() != "" && SP->getName() != SP->getLinkageName() &&
(useAllLinkageNames() || InfoHolder.getAbstractSPDies().lookup(SP)))
addAccelName(CU, SP->getLinkageName(), Die);
// If this is an Objective-C selector name add it to the ObjC accelerator
// too.
if (isObjCClass(SP->getName())) {
StringRef Class, Category;
getObjCClassCategory(SP->getName(), Class, Category);
addAccelObjC(CU, Class, Die);
if (Category != "")
addAccelObjC(CU, Category, Die);
// Also add the base method name to the name table.
addAccelName(CU, getObjCMethodName(SP->getName()), Die);
}
}
/// Check whether we should create a DIE for the given Scope, return true
/// if we don't create a DIE (the corresponding DIE is null).
bool DwarfDebug::isLexicalScopeDIENull(LexicalScope *Scope) {
if (Scope->isAbstractScope())
return false;
// We don't create a DIE if there is no Range.
const SmallVectorImpl<InsnRange> &Ranges = Scope->getRanges();
if (Ranges.empty())
return true;
if (Ranges.size() > 1)
return false;
// We don't create a DIE if we have a single Range and the end label
// is null.
return !getLabelAfterInsn(Ranges.front().second);
}
template <typename Func> static void forBothCUs(DwarfCompileUnit &CU, Func F) {
F(CU);
if (auto *SkelCU = CU.getSkeleton())
if (CU.getCUNode()->getSplitDebugInlining())
F(*SkelCU);
}
bool DwarfDebug::shareAcrossDWOCUs() const {
return SplitDwarfCrossCuReferences;
}
void DwarfDebug::constructAbstractSubprogramScopeDIE(DwarfCompileUnit &SrcCU,
LexicalScope *Scope) {
assert(Scope && Scope->getScopeNode());
assert(Scope->isAbstractScope());
assert(!Scope->getInlinedAt());
auto *SP = cast<DISubprogram>(Scope->getScopeNode());
// Find the subprogram's DwarfCompileUnit in the SPMap in case the subprogram
// was inlined from another compile unit.
if (useSplitDwarf() && !shareAcrossDWOCUs() && !SP->getUnit()->getSplitDebugInlining())
// Avoid building the original CU if it won't be used
SrcCU.constructAbstractSubprogramScopeDIE(Scope);
else {
auto &CU = getOrCreateDwarfCompileUnit(SP->getUnit());
if (auto *SkelCU = CU.getSkeleton()) {
(shareAcrossDWOCUs() ? CU : SrcCU)
.constructAbstractSubprogramScopeDIE(Scope);
if (CU.getCUNode()->getSplitDebugInlining())
SkelCU->constructAbstractSubprogramScopeDIE(Scope);
} else
CU.constructAbstractSubprogramScopeDIE(Scope);
}
}
/// Try to interpret values loaded into registers that forward parameters
/// for \p CallMI. Store parameters with interpreted value into \p Params.
static void collectCallSiteParameters(const MachineInstr *CallMI,
ParamSet &Params) {
auto *MF = CallMI->getMF();
auto CalleesMap = MF->getCallSitesInfo();
auto CallFwdRegsInfo = CalleesMap.find(CallMI);
// There is no information for the call instruction.
if (CallFwdRegsInfo == CalleesMap.end())
return;
auto *MBB = CallMI->getParent();
const auto &TRI = MF->getSubtarget().getRegisterInfo();
const auto &TII = MF->getSubtarget().getInstrInfo();
const auto &TLI = MF->getSubtarget().getTargetLowering();
// Skip the call instruction.
auto I = std::next(CallMI->getReverseIterator());
DenseSet<unsigned> ForwardedRegWorklist;
// Add all the forwarding registers into the ForwardedRegWorklist.
for (auto ArgReg : CallFwdRegsInfo->second) {
bool InsertedReg = ForwardedRegWorklist.insert(ArgReg.Reg).second;
assert(InsertedReg && "Single register used to forward two arguments?");
(void)InsertedReg;
}
// We erase, from the ForwardedRegWorklist, those forwarding registers for
// which we successfully describe a loaded value (by using
// the describeLoadedValue()). For those remaining arguments in the working
// list, for which we do not describe a loaded value by
// the describeLoadedValue(), we try to generate an entry value expression
// for their call site value desctipion, if the call is within the entry MBB.
// The RegsForEntryValues maps a forwarding register into the register holding
// the entry value.
// TODO: Handle situations when call site parameter value can be described
// as the entry value within basic blocks other then the first one.
bool ShouldTryEmitEntryVals = MBB->getIterator() == MF->begin();
DenseMap<unsigned, unsigned> RegsForEntryValues;
// If the MI is an instruction defining one or more parameters' forwarding
// registers, add those defines. We can currently only describe forwarded
// registers that are explicitly defined, but keep track of implicit defines
// also to remove those registers from the work list.
auto getForwardingRegsDefinedByMI = [&](const MachineInstr &MI,
SmallVectorImpl<unsigned> &Explicit,
SmallVectorImpl<unsigned> &Implicit) {
if (MI.isDebugInstr())
return;
for (const MachineOperand &MO : MI.operands()) {
if (MO.isReg() && MO.isDef() &&
Register::isPhysicalRegister(MO.getReg())) {
for (auto FwdReg : ForwardedRegWorklist) {
if (TRI->regsOverlap(FwdReg, MO.getReg())) {
if (MO.isImplicit())
Implicit.push_back(FwdReg);
else
Explicit.push_back(FwdReg);
}
}
}
}
};
auto finishCallSiteParam = [&](DbgValueLoc DbgLocVal, unsigned Reg) {
unsigned FwdReg = Reg;
if (ShouldTryEmitEntryVals) {
auto EntryValReg = RegsForEntryValues.find(Reg);
if (EntryValReg != RegsForEntryValues.end())
FwdReg = EntryValReg->second;
}
DbgCallSiteParam CSParm(FwdReg, DbgLocVal);
Params.push_back(CSParm);
++NumCSParams;
};
// Search for a loading value in forwarding registers.
for (; I != MBB->rend(); ++I) {
// Skip bundle headers.
if (I->isBundle())
continue;
// If the next instruction is a call we can not interpret parameter's
// forwarding registers or we finished the interpretation of all parameters.
if (I->isCall())
return;
if (ForwardedRegWorklist.empty())
return;
SmallVector<unsigned, 4> ExplicitFwdRegDefs;
SmallVector<unsigned, 4> ImplicitFwdRegDefs;
getForwardingRegsDefinedByMI(*I, ExplicitFwdRegDefs, ImplicitFwdRegDefs);
if (ExplicitFwdRegDefs.empty() && ImplicitFwdRegDefs.empty())
continue;
// If the MI clobbers more then one forwarding register we must remove
// all of them from the working list.
for (auto Reg : concat<unsigned>(ExplicitFwdRegDefs, ImplicitFwdRegDefs))
ForwardedRegWorklist.erase(Reg);
for (auto ParamFwdReg : ExplicitFwdRegDefs) {
if (auto ParamValue = TII->describeLoadedValue(*I, ParamFwdReg)) {
if (ParamValue->first.isImm()) {
int64_t Val = ParamValue->first.getImm();
DbgValueLoc DbgLocVal(ParamValue->second, Val);
finishCallSiteParam(DbgLocVal, ParamFwdReg);
} else if (ParamValue->first.isReg()) {
Register RegLoc = ParamValue->first.getReg();
// TODO: For now, there is no use of describing the value loaded into the
// register that is also the source registers (e.g. $r0 = add $r0, x).
if (ParamFwdReg == RegLoc)
continue;
unsigned SP = TLI->getStackPointerRegisterToSaveRestore();
Register FP = TRI->getFrameRegister(*MF);
bool IsSPorFP = (RegLoc == SP) || (RegLoc == FP);
if (TRI->isCalleeSavedPhysReg(RegLoc, *MF) || IsSPorFP) {
DbgValueLoc DbgLocVal(ParamValue->second,
MachineLocation(RegLoc,
/*IsIndirect=*/IsSPorFP));
finishCallSiteParam(DbgLocVal, ParamFwdReg);
// TODO: Add support for entry value plus an expression.
} else if (ShouldTryEmitEntryVals &&
ParamValue->second->getNumElements() == 0) {
ForwardedRegWorklist.insert(RegLoc);
RegsForEntryValues[RegLoc] = ParamFwdReg;
}
}
}
}
}
// Emit the call site parameter's value as an entry value.
if (ShouldTryEmitEntryVals) {
// Create an expression where the register's entry value is used.
DIExpression *EntryExpr = DIExpression::get(
MF->getFunction().getContext(), {dwarf::DW_OP_LLVM_entry_value, 1});
for (auto RegEntry : ForwardedRegWorklist) {
unsigned FwdReg = RegEntry;
auto EntryValReg = RegsForEntryValues.find(RegEntry);
if (EntryValReg != RegsForEntryValues.end())
FwdReg = EntryValReg->second;
DbgValueLoc DbgLocVal(EntryExpr, MachineLocation(RegEntry));
DbgCallSiteParam CSParm(FwdReg, DbgLocVal);
Params.push_back(CSParm);
++NumCSParams;
}
}
}
void DwarfDebug::constructCallSiteEntryDIEs(const DISubprogram &SP,
DwarfCompileUnit &CU, DIE &ScopeDIE,
const MachineFunction &MF) {
// Add a call site-related attribute (DWARF5, Sec. 3.3.1.3). Do this only if
// the subprogram is required to have one.
if (!SP.areAllCallsDescribed() || !SP.isDefinition())
return;
// Use DW_AT_call_all_calls to express that call site entries are present
// for both tail and non-tail calls. Don't use DW_AT_call_all_source_calls
// because one of its requirements is not met: call site entries for
// optimized-out calls are elided.
CU.addFlag(ScopeDIE, CU.getDwarf5OrGNUAttr(dwarf::DW_AT_call_all_calls));
const TargetInstrInfo *TII = MF.getSubtarget().getInstrInfo();
assert(TII && "TargetInstrInfo not found: cannot label tail calls");
bool ApplyGNUExtensions = getDwarfVersion() == 4 && tuneForGDB();
// Emit call site entries for each call or tail call in the function.
for (const MachineBasicBlock &MBB : MF) {
for (const MachineInstr &MI : MBB.instrs()) {
// Bundles with call in them will pass the isCall() test below but do not
// have callee operand information so skip them here. Iterator will
// eventually reach the call MI.
if (MI.isBundle())
continue;
// Skip instructions which aren't calls. Both calls and tail-calling jump
// instructions (e.g TAILJMPd64) are classified correctly here.
if (!MI.isCall())
continue;
// TODO: Add support for targets with delay slots (see: beginInstruction).
if (MI.hasDelaySlot())
return;
// If this is a direct call, find the callee's subprogram.
// In the case of an indirect call find the register that holds
// the callee.
const MachineOperand &CalleeOp = MI.getOperand(0);
if (!CalleeOp.isGlobal() && !CalleeOp.isReg())
continue;
unsigned CallReg = 0;
const DISubprogram *CalleeSP = nullptr;
const Function *CalleeDecl = nullptr;
if (CalleeOp.isReg()) {
CallReg = CalleeOp.getReg();
if (!CallReg)
continue;
} else {
CalleeDecl = dyn_cast<Function>(CalleeOp.getGlobal());
if (!CalleeDecl || !CalleeDecl->getSubprogram())
continue;
CalleeSP = CalleeDecl->getSubprogram();
}
// TODO: Omit call site entries for runtime calls (objc_msgSend, etc).
bool IsTail = TII->isTailCall(MI);
// If MI is in a bundle, the label was created after the bundle since
// EmitFunctionBody iterates over top-level MIs. Get that top-level MI
// to search for that label below.
const MachineInstr *TopLevelCallMI =
MI.isInsideBundle() ? &*getBundleStart(MI.getIterator()) : &MI;
// For tail calls, for non-gdb tuning, no return PC information is needed.
// For regular calls (and tail calls in GDB tuning), the return PC
// is needed to disambiguate paths in the call graph which could lead to
// some target function.
const MCExpr *PCOffset =
(IsTail && !tuneForGDB())
? nullptr
: getFunctionLocalOffsetAfterInsn(TopLevelCallMI);
// Return address of a call-like instruction for a normal call or a
// jump-like instruction for a tail call. This is needed for
// GDB + DWARF 4 tuning.
const MCSymbol *PCAddr =
ApplyGNUExtensions
? const_cast<MCSymbol *>(getLabelAfterInsn(TopLevelCallMI))
: nullptr;
assert((IsTail || PCOffset || PCAddr) &&
"Call without return PC information");
LLVM_DEBUG(dbgs() << "CallSiteEntry: " << MF.getName() << " -> "
<< (CalleeDecl ? CalleeDecl->getName()
: StringRef(MF.getSubtarget()
.getRegisterInfo()
->getName(CallReg)))
<< (IsTail ? " [IsTail]" : "") << "\n");
DIE &CallSiteDIE =
CU.constructCallSiteEntryDIE(ScopeDIE, CalleeSP, IsTail, PCAddr,
PCOffset, CallReg);
// GDB and LLDB support call site parameter debug info.
if (Asm->TM.Options.EnableDebugEntryValues &&
(tuneForGDB() || tuneForLLDB())) {
ParamSet Params;
// Try to interpret values of call site parameters.
collectCallSiteParameters(&MI, Params);
CU.constructCallSiteParmEntryDIEs(CallSiteDIE, Params);
}
}
}
}
void DwarfDebug::addGnuPubAttributes(DwarfCompileUnit &U, DIE &D) const {
if (!U.hasDwarfPubSections())
return;
U.addFlag(D, dwarf::DW_AT_GNU_pubnames);
}
void DwarfDebug::finishUnitAttributes(const DICompileUnit *DIUnit,
DwarfCompileUnit &NewCU) {
DIE &Die = NewCU.getUnitDie();
StringRef FN = DIUnit->getFilename();
StringRef Producer = DIUnit->getProducer();
StringRef Flags = DIUnit->getFlags();
if (!Flags.empty() && !useAppleExtensionAttributes()) {
std::string ProducerWithFlags = Producer.str() + " " + Flags.str();
NewCU.addString(Die, dwarf::DW_AT_producer, ProducerWithFlags);
} else
NewCU.addString(Die, dwarf::DW_AT_producer, Producer);
NewCU.addUInt(Die, dwarf::DW_AT_language, dwarf::DW_FORM_data2,
DIUnit->getSourceLanguage());
NewCU.addString(Die, dwarf::DW_AT_name, FN);
// Add DW_str_offsets_base to the unit DIE, except for split units.
if (useSegmentedStringOffsetsTable() && !useSplitDwarf())
NewCU.addStringOffsetsStart();
if (!useSplitDwarf()) {
NewCU.initStmtList();
// If we're using split dwarf the compilation dir is going to be in the
// skeleton CU and so we don't need to duplicate it here.
if (!CompilationDir.empty())
NewCU.addString(Die, dwarf::DW_AT_comp_dir, CompilationDir);
addGnuPubAttributes(NewCU, Die);
}
if (useAppleExtensionAttributes()) {
if (DIUnit->isOptimized())
NewCU.addFlag(Die, dwarf::DW_AT_APPLE_optimized);
StringRef Flags = DIUnit->getFlags();
if (!Flags.empty())
NewCU.addString(Die, dwarf::DW_AT_APPLE_flags, Flags);
if (unsigned RVer = DIUnit->getRuntimeVersion())
NewCU.addUInt(Die, dwarf::DW_AT_APPLE_major_runtime_vers,
dwarf::DW_FORM_data1, RVer);
}
if (DIUnit->getDWOId()) {
// This CU is either a clang module DWO or a skeleton CU.
NewCU.addUInt(Die, dwarf::DW_AT_GNU_dwo_id, dwarf::DW_FORM_data8,
DIUnit->getDWOId());
if (!DIUnit->getSplitDebugFilename().empty()) {
// This is a prefabricated skeleton CU.
dwarf::Attribute attrDWOName = getDwarfVersion() >= 5
? dwarf::DW_AT_dwo_name
: dwarf::DW_AT_GNU_dwo_name;
NewCU.addString(Die, attrDWOName, DIUnit->getSplitDebugFilename());
}
}
}
// Create new DwarfCompileUnit for the given metadata node with tag
// DW_TAG_compile_unit.
DwarfCompileUnit &
DwarfDebug::getOrCreateDwarfCompileUnit(const DICompileUnit *DIUnit) {
if (auto *CU = CUMap.lookup(DIUnit))
return *CU;
CompilationDir = DIUnit->getDirectory();
auto OwnedUnit = std::make_unique<DwarfCompileUnit>(
InfoHolder.getUnits().size(), DIUnit, Asm, this, &InfoHolder);
DwarfCompileUnit &NewCU = *OwnedUnit;
InfoHolder.addUnit(std::move(OwnedUnit));
for (auto *IE : DIUnit->getImportedEntities())
NewCU.addImportedEntity(IE);
// LTO with assembly output shares a single line table amongst multiple CUs.
// To avoid the compilation directory being ambiguous, let the line table
// explicitly describe the directory of all files, never relying on the
// compilation directory.
if (!Asm->OutStreamer->hasRawTextSupport() || SingleCU)
Asm->OutStreamer->emitDwarfFile0Directive(
CompilationDir, DIUnit->getFilename(),
NewCU.getMD5AsBytes(DIUnit->getFile()), DIUnit->getSource(),
NewCU.getUniqueID());
if (useSplitDwarf()) {
NewCU.setSkeleton(constructSkeletonCU(NewCU));
NewCU.setSection(Asm->getObjFileLowering().getDwarfInfoDWOSection());
} else {
finishUnitAttributes(DIUnit, NewCU);
NewCU.setSection(Asm->getObjFileLowering().getDwarfInfoSection());
}
// Create DIEs for function declarations used for call site debug info.
for (auto Scope : DIUnit->getRetainedTypes())
if (auto *SP = dyn_cast_or_null<DISubprogram>(Scope))
NewCU.getOrCreateSubprogramDIE(SP);
CUMap.insert({DIUnit, &NewCU});
CUDieMap.insert({&NewCU.getUnitDie(), &NewCU});
return NewCU;
}
void DwarfDebug::constructAndAddImportedEntityDIE(DwarfCompileUnit &TheCU,
const DIImportedEntity *N) {
if (isa<DILocalScope>(N->getScope()))
return;
if (DIE *D = TheCU.getOrCreateContextDIE(N->getScope()))
D->addChild(TheCU.constructImportedEntityDIE(N));
}
/// Sort and unique GVEs by comparing their fragment offset.
static SmallVectorImpl<DwarfCompileUnit::GlobalExpr> &
sortGlobalExprs(SmallVectorImpl<DwarfCompileUnit::GlobalExpr> &GVEs) {
llvm::sort(
GVEs, [](DwarfCompileUnit::GlobalExpr A, DwarfCompileUnit::GlobalExpr B) {
// Sort order: first null exprs, then exprs without fragment
// info, then sort by fragment offset in bits.
// FIXME: Come up with a more comprehensive comparator so
// the sorting isn't non-deterministic, and so the following
// std::unique call works correctly.
if (!A.Expr || !B.Expr)
return !!B.Expr;
auto FragmentA = A.Expr->getFragmentInfo();
auto FragmentB = B.Expr->getFragmentInfo();
if (!FragmentA || !FragmentB)
return !!FragmentB;
return FragmentA->OffsetInBits < FragmentB->OffsetInBits;
});
GVEs.erase(std::unique(GVEs.begin(), GVEs.end(),
[](DwarfCompileUnit::GlobalExpr A,
DwarfCompileUnit::GlobalExpr B) {
return A.Expr == B.Expr;
}),
GVEs.end());
return GVEs;
}
// Emit all Dwarf sections that should come prior to the content. Create
// global DIEs and emit initial debug info sections. This is invoked by
// the target AsmPrinter.
void DwarfDebug::beginModule() {
NamedRegionTimer T(DbgTimerName, DbgTimerDescription, DWARFGroupName,
DWARFGroupDescription, TimePassesIsEnabled);
if (DisableDebugInfoPrinting) {
MMI->setDebugInfoAvailability(false);
return;
}
const Module *M = MMI->getModule();
unsigned NumDebugCUs = std::distance(M->debug_compile_units_begin(),
M->debug_compile_units_end());
// Tell MMI whether we have debug info.
assert(MMI->hasDebugInfo() == (NumDebugCUs > 0) &&
"DebugInfoAvailabilty initialized unexpectedly");
SingleCU = NumDebugCUs == 1;
DenseMap<DIGlobalVariable *, SmallVector<DwarfCompileUnit::GlobalExpr, 1>>
GVMap;
for (const GlobalVariable &Global : M->globals()) {
SmallVector<DIGlobalVariableExpression *, 1> GVs;
Global.getDebugInfo(GVs);
for (auto *GVE : GVs)
GVMap[GVE->getVariable()].push_back({&Global, GVE->getExpression()});
}
// Create the symbol that designates the start of the unit's contribution
// to the string offsets table. In a split DWARF scenario, only the skeleton
// unit has the DW_AT_str_offsets_base attribute (and hence needs the symbol).
if (useSegmentedStringOffsetsTable())
(useSplitDwarf() ? SkeletonHolder : InfoHolder)
.setStringOffsetsStartSym(Asm->createTempSymbol("str_offsets_base"));
// Create the symbols that designates the start of the DWARF v5 range list
// and locations list tables. They are located past the table headers.
if (getDwarfVersion() >= 5) {
DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
Holder.setRnglistsTableBaseSym(
Asm->createTempSymbol("rnglists_table_base"));
if (useSplitDwarf())
InfoHolder.setRnglistsTableBaseSym(
Asm->createTempSymbol("rnglists_dwo_table_base"));
}
// Create the symbol that points to the first entry following the debug
// address table (.debug_addr) header.
AddrPool.setLabel(Asm->createTempSymbol("addr_table_base"));
DebugLocs.setSym(Asm->createTempSymbol("loclists_table_base"));
for (DICompileUnit *CUNode : M->debug_compile_units()) {
// FIXME: Move local imported entities into a list attached to the
// subprogram, then this search won't be needed and a
// getImportedEntities().empty() test should go below with the rest.
bool HasNonLocalImportedEntities = llvm::any_of(
CUNode->getImportedEntities(), [](const DIImportedEntity *IE) {
return !isa<DILocalScope>(IE->getScope());
});
if (!HasNonLocalImportedEntities && CUNode->getEnumTypes().empty() &&
CUNode->getRetainedTypes().empty() &&
CUNode->getGlobalVariables().empty() && CUNode->getMacros().empty())
continue;
DwarfCompileUnit &CU = getOrCreateDwarfCompileUnit(CUNode);
// Global Variables.
for (auto *GVE : CUNode->getGlobalVariables()) {
// Don't bother adding DIGlobalVariableExpressions listed in the CU if we
// already know about the variable and it isn't adding a constant
// expression.
auto &GVMapEntry = GVMap[GVE->getVariable()];
auto *Expr = GVE->getExpression();
if (!GVMapEntry.size() || (Expr && Expr->isConstant()))
GVMapEntry.push_back({nullptr, Expr});
}
DenseSet<DIGlobalVariable *> Processed;
for (auto *GVE : CUNode->getGlobalVariables()) {
DIGlobalVariable *GV = GVE->getVariable();
if (Processed.insert(GV).second)
CU.getOrCreateGlobalVariableDIE(GV, sortGlobalExprs(GVMap[GV]));
}
for (auto *Ty : CUNode->getEnumTypes()) {
// The enum types array by design contains pointers to
// MDNodes rather than DIRefs. Unique them here.
CU.getOrCreateTypeDIE(cast<DIType>(Ty));
}
for (auto *Ty : CUNode->getRetainedTypes()) {
// The retained types array by design contains pointers to
// MDNodes rather than DIRefs. Unique them here.
if (DIType *RT = dyn_cast<DIType>(Ty))
// There is no point in force-emitting a forward declaration.
CU.getOrCreateTypeDIE(RT);
}
// Emit imported_modules last so that the relevant context is already
// available.
for (auto *IE : CUNode->getImportedEntities())
constructAndAddImportedEntityDIE(CU, IE);
}
}
void DwarfDebug::finishEntityDefinitions() {
for (const auto &Entity : ConcreteEntities) {
DIE *Die = Entity->getDIE();
assert(Die);
// FIXME: Consider the time-space tradeoff of just storing the unit pointer
// in the ConcreteEntities list, rather than looking it up again here.
// DIE::getUnit isn't simple - it walks parent pointers, etc.
DwarfCompileUnit *Unit = CUDieMap.lookup(Die->getUnitDie());
assert(Unit);
Unit->finishEntityDefinition(Entity.get());
}
}
void DwarfDebug::finishSubprogramDefinitions() {
for (const DISubprogram *SP : ProcessedSPNodes) {
assert(SP->getUnit()->getEmissionKind() != DICompileUnit::NoDebug);
forBothCUs(
getOrCreateDwarfCompileUnit(SP->getUnit()),
[&](DwarfCompileUnit &CU) { CU.finishSubprogramDefinition(SP); });
}
}
void DwarfDebug::finalizeModuleInfo() {
const TargetLoweringObjectFile &TLOF = Asm->getObjFileLowering();
finishSubprogramDefinitions();
finishEntityDefinitions();
// Include the DWO file name in the hash if there's more than one CU.
// This handles ThinLTO's situation where imported CUs may very easily be
// duplicate with the same CU partially imported into another ThinLTO unit.
StringRef DWOName;
if (CUMap.size() > 1)
DWOName = Asm->TM.Options.MCOptions.SplitDwarfFile;
// Handle anything that needs to be done on a per-unit basis after
// all other generation.
for (const auto &P : CUMap) {
auto &TheCU = *P.second;
if (TheCU.getCUNode()->isDebugDirectivesOnly())
continue;
// Emit DW_AT_containing_type attribute to connect types with their
// vtable holding type.
TheCU.constructContainingTypeDIEs();
// Add CU specific attributes if we need to add any.
// If we're splitting the dwarf out now that we've got the entire
// CU then add the dwo id to it.
auto *SkCU = TheCU.getSkeleton();
bool HasSplitUnit = SkCU && !TheCU.getUnitDie().children().empty();
if (HasSplitUnit) {
dwarf::Attribute attrDWOName = getDwarfVersion() >= 5
? dwarf::DW_AT_dwo_name
: dwarf::DW_AT_GNU_dwo_name;
finishUnitAttributes(TheCU.getCUNode(), TheCU);
TheCU.addString(TheCU.getUnitDie(), attrDWOName,
Asm->TM.Options.MCOptions.SplitDwarfFile);
SkCU->addString(SkCU->getUnitDie(), attrDWOName,
Asm->TM.Options.MCOptions.SplitDwarfFile);
// Emit a unique identifier for this CU.
uint64_t ID =
DIEHash(Asm).computeCUSignature(DWOName, TheCU.getUnitDie());
if (getDwarfVersion() >= 5) {
TheCU.setDWOId(ID);
SkCU->setDWOId(ID);
} else {
TheCU.addUInt(TheCU.getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
dwarf::DW_FORM_data8, ID);
SkCU->addUInt(SkCU->getUnitDie(), dwarf::DW_AT_GNU_dwo_id,
dwarf::DW_FORM_data8, ID);
}
if (getDwarfVersion() < 5 && !SkeletonHolder.getRangeLists().empty()) {
const MCSymbol *Sym = TLOF.getDwarfRangesSection()->getBeginSymbol();
SkCU->addSectionLabel(SkCU->getUnitDie(), dwarf::DW_AT_GNU_ranges_base,
Sym, Sym);
}
} else if (SkCU) {
finishUnitAttributes(SkCU->getCUNode(), *SkCU);
}
// If we have code split among multiple sections or non-contiguous
// ranges of code then emit a DW_AT_ranges attribute on the unit that will
// remain in the .o file, otherwise add a DW_AT_low_pc.
// FIXME: We should use ranges allow reordering of code ala
// .subsections_via_symbols in mach-o. This would mean turning on
// ranges for all subprogram DIEs for mach-o.
DwarfCompileUnit &U = SkCU ? *SkCU : TheCU;
if (unsigned NumRanges = TheCU.getRanges().size()) {
if (NumRanges > 1 && useRangesSection())
// A DW_AT_low_pc attribute may also be specified in combination with
// DW_AT_ranges to specify the default base address for use in
// location lists (see Section 2.6.2) and range lists (see Section
// 2.17.3).
U.addUInt(U.getUnitDie(), dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr, 0);
else
U.setBaseAddress(TheCU.getRanges().front().Begin);
U.attachRangesOrLowHighPC(U.getUnitDie(), TheCU.takeRanges());
}
// We don't keep track of which addresses are used in which CU so this
// is a bit pessimistic under LTO.
if ((!AddrPool.isEmpty() || TheCU.hasRangeLists()) &&
(getDwarfVersion() >= 5 || HasSplitUnit))
U.addAddrTableBase();
if (getDwarfVersion() >= 5) {
if (U.hasRangeLists())
U.addRnglistsBase();
if (!DebugLocs.getLists().empty()) {
if (!useSplitDwarf())
U.addSectionLabel(U.getUnitDie(), dwarf::DW_AT_loclists_base,
DebugLocs.getSym(),
TLOF.getDwarfLoclistsSection()->getBeginSymbol());
}
}
auto *CUNode = cast<DICompileUnit>(P.first);
// If compile Unit has macros, emit "DW_AT_macro_info" attribute.
if (CUNode->getMacros()) {
if (useSplitDwarf())
TheCU.addSectionDelta(TheCU.getUnitDie(), dwarf::DW_AT_macro_info,
U.getMacroLabelBegin(),
TLOF.getDwarfMacinfoDWOSection()->getBeginSymbol());
else
U.addSectionLabel(U.getUnitDie(), dwarf::DW_AT_macro_info,
U.getMacroLabelBegin(),
TLOF.getDwarfMacinfoSection()->getBeginSymbol());
}
}
// Emit all frontend-produced Skeleton CUs, i.e., Clang modules.
for (auto *CUNode : MMI->getModule()->debug_compile_units())
if (CUNode->getDWOId())
getOrCreateDwarfCompileUnit(CUNode);
// Compute DIE offsets and sizes.
InfoHolder.computeSizeAndOffsets();
if (useSplitDwarf())
SkeletonHolder.computeSizeAndOffsets();
}
// Emit all Dwarf sections that should come after the content.
void DwarfDebug::endModule() {
assert(CurFn == nullptr);
assert(CurMI == nullptr);
for (const auto &P : CUMap) {
auto &CU = *P.second;
CU.createBaseTypeDIEs();
}
// If we aren't actually generating debug info (check beginModule -
// conditionalized on !DisableDebugInfoPrinting and the presence of the
// llvm.dbg.cu metadata node)
if (!MMI->hasDebugInfo())
return;
// Finalize the debug info for the module.
finalizeModuleInfo();
emitDebugStr();
if (useSplitDwarf())
// Emit debug_loc.dwo/debug_loclists.dwo section.
emitDebugLocDWO();
else
// Emit debug_loc/debug_loclists section.
emitDebugLoc();
// Corresponding abbreviations into a abbrev section.
emitAbbreviations();
// Emit all the DIEs into a debug info section.
emitDebugInfo();
// Emit info into a debug aranges section.
if (GenerateARangeSection)
emitDebugARanges();
// Emit info into a debug ranges section.
emitDebugRanges();
if (useSplitDwarf())
// Emit info into a debug macinfo.dwo section.
emitDebugMacinfoDWO();
else
// Emit info into a debug macinfo section.
emitDebugMacinfo();
if (useSplitDwarf()) {
emitDebugStrDWO();
emitDebugInfoDWO();
emitDebugAbbrevDWO();
emitDebugLineDWO();
emitDebugRangesDWO();
}
emitDebugAddr();
// Emit info into the dwarf accelerator table sections.
switch (getAccelTableKind()) {
case AccelTableKind::Apple:
emitAccelNames();
emitAccelObjC();
emitAccelNamespaces();
emitAccelTypes();
break;
case AccelTableKind::Dwarf:
emitAccelDebugNames();
break;
case AccelTableKind::None:
break;
case AccelTableKind::Default:
llvm_unreachable("Default should have already been resolved.");
}
// Emit the pubnames and pubtypes sections if requested.
emitDebugPubSections();
// clean up.
// FIXME: AbstractVariables.clear();
}
void DwarfDebug::ensureAbstractEntityIsCreated(DwarfCompileUnit &CU,
const DINode *Node,
const MDNode *ScopeNode) {
if (CU.getExistingAbstractEntity(Node))
return;
CU.createAbstractEntity(Node, LScopes.getOrCreateAbstractScope(
cast<DILocalScope>(ScopeNode)));
}
void DwarfDebug::ensureAbstractEntityIsCreatedIfScoped(DwarfCompileUnit &CU,
const DINode *Node, const MDNode *ScopeNode) {
if (CU.getExistingAbstractEntity(Node))
return;
if (LexicalScope *Scope =
LScopes.findAbstractScope(cast_or_null<DILocalScope>(ScopeNode)))
CU.createAbstractEntity(Node, Scope);
}
// Collect variable information from side table maintained by MF.
void DwarfDebug::collectVariableInfoFromMFTable(
DwarfCompileUnit &TheCU, DenseSet<InlinedEntity> &Processed) {
SmallDenseMap<InlinedEntity, DbgVariable *> MFVars;
for (const auto &VI : Asm->MF->getVariableDbgInfo()) {
if (!VI.Var)
continue;
assert(VI.Var->isValidLocationForIntrinsic(VI.Loc) &&
"Expected inlined-at fields to agree");
InlinedEntity Var(VI.Var, VI.Loc->getInlinedAt());
Processed.insert(Var);
LexicalScope *Scope = LScopes.findLexicalScope(VI.Loc);
// If variable scope is not found then skip this variable.
if (!Scope)
continue;
ensureAbstractEntityIsCreatedIfScoped(TheCU, Var.first, Scope->getScopeNode());
auto RegVar = std::make_unique<DbgVariable>(
cast<DILocalVariable>(Var.first), Var.second);
RegVar->initializeMMI(VI.Expr, VI.Slot);
if (DbgVariable *DbgVar = MFVars.lookup(Var))
DbgVar->addMMIEntry(*RegVar);
else if (InfoHolder.addScopeVariable(Scope, RegVar.get())) {
MFVars.insert({Var, RegVar.get()});
ConcreteEntities.push_back(std::move(RegVar));
}
}
}
/// Determine whether a *singular* DBG_VALUE is valid for the entirety of its
/// enclosing lexical scope. The check ensures there are no other instructions
/// in the same lexical scope preceding the DBG_VALUE and that its range is
/// either open or otherwise rolls off the end of the scope.
static bool validThroughout(LexicalScopes &LScopes,
const MachineInstr *DbgValue,
const MachineInstr *RangeEnd) {
assert(DbgValue->getDebugLoc() && "DBG_VALUE without a debug location");
auto MBB = DbgValue->getParent();
auto DL = DbgValue->getDebugLoc();
auto *LScope = LScopes.findLexicalScope(DL);
// Scope doesn't exist; this is a dead DBG_VALUE.
if (!LScope)
return false;
auto &LSRange = LScope->getRanges();
if (LSRange.size() == 0)
return false;
// Determine if the DBG_VALUE is valid at the beginning of its lexical block.
const MachineInstr *LScopeBegin = LSRange.front().first;
// Early exit if the lexical scope begins outside of the current block.
if (LScopeBegin->getParent() != MBB)
return false;
MachineBasicBlock::const_reverse_iterator Pred(DbgValue);
for (++Pred; Pred != MBB->rend(); ++Pred) {
if (Pred->getFlag(MachineInstr::FrameSetup))
break;
auto PredDL = Pred->getDebugLoc();
if (!PredDL || Pred->isMetaInstruction())
continue;
// Check whether the instruction preceding the DBG_VALUE is in the same
// (sub)scope as the DBG_VALUE.
if (DL->getScope() == PredDL->getScope())
return false;
auto *PredScope = LScopes.findLexicalScope(PredDL);
if (!PredScope || LScope->dominates(PredScope))
return false;
}
// If the range of the DBG_VALUE is open-ended, report success.
if (!RangeEnd)
return true;
// Fail if there are instructions belonging to our scope in another block.
const MachineInstr *LScopeEnd = LSRange.back().second;
if (LScopeEnd->getParent() != MBB)
return false;
// Single, constant DBG_VALUEs in the prologue are promoted to be live
// throughout the function. This is a hack, presumably for DWARF v2 and not
// necessarily correct. It would be much better to use a dbg.declare instead
// if we know the constant is live throughout the scope.
if (DbgValue->getOperand(0).isImm() && MBB->pred_empty())
return true;
return false;
}
/// Build the location list for all DBG_VALUEs in the function that
/// describe the same variable. The resulting DebugLocEntries will have
/// strict monotonically increasing begin addresses and will never
/// overlap. If the resulting list has only one entry that is valid
/// throughout variable's scope return true.
//
// See the definition of DbgValueHistoryMap::Entry for an explanation of the
// different kinds of history map entries. One thing to be aware of is that if
// a debug value is ended by another entry (rather than being valid until the
// end of the function), that entry's instruction may or may not be included in
// the range, depending on if the entry is a clobbering entry (it has an
// instruction that clobbers one or more preceding locations), or if it is an
// (overlapping) debug value entry. This distinction can be seen in the example
// below. The first debug value is ended by the clobbering entry 2, and the
// second and third debug values are ended by the overlapping debug value entry
// 4.
//
// Input:
//
// History map entries [type, end index, mi]
//
// 0 | [DbgValue, 2, DBG_VALUE $reg0, [...] (fragment 0, 32)]
// 1 | | [DbgValue, 4, DBG_VALUE $reg1, [...] (fragment 32, 32)]
// 2 | | [Clobber, $reg0 = [...], -, -]
// 3 | | [DbgValue, 4, DBG_VALUE 123, [...] (fragment 64, 32)]
// 4 [DbgValue, ~0, DBG_VALUE @g, [...] (fragment 0, 96)]
//
// Output [start, end) [Value...]:
//
// [0-1) [(reg0, fragment 0, 32)]
// [1-3) [(reg0, fragment 0, 32), (reg1, fragment 32, 32)]
// [3-4) [(reg1, fragment 32, 32), (123, fragment 64, 32)]
// [4-) [(@g, fragment 0, 96)]
bool DwarfDebug::buildLocationList(SmallVectorImpl<DebugLocEntry> &DebugLoc,
const DbgValueHistoryMap::Entries &Entries) {
using OpenRange =
std::pair<DbgValueHistoryMap::EntryIndex, DbgValueLoc>;
SmallVector<OpenRange, 4> OpenRanges;
bool isSafeForSingleLocation = true;
const MachineInstr *StartDebugMI = nullptr;
const MachineInstr *EndMI = nullptr;
for (auto EB = Entries.begin(), EI = EB, EE = Entries.end(); EI != EE; ++EI) {
const MachineInstr *Instr = EI->getInstr();
// Remove all values that are no longer live.
size_t Index = std::distance(EB, EI);
auto Last =
remove_if(OpenRanges, [&](OpenRange &R) { return R.first <= Index; });
OpenRanges.erase(Last, OpenRanges.end());
// If we are dealing with a clobbering entry, this iteration will result in
// a location list entry starting after the clobbering instruction.
const MCSymbol *StartLabel =
EI->isClobber() ? getLabelAfterInsn(Instr) : getLabelBeforeInsn(Instr);
assert(StartLabel &&
"Forgot label before/after instruction starting a range!");
const MCSymbol *EndLabel;
if (std::next(EI) == Entries.end()) {
EndLabel = Asm->getFunctionEnd();
if (EI->isClobber())
EndMI = EI->getInstr();
}
else if (std::next(EI)->isClobber())
EndLabel = getLabelAfterInsn(std::next(EI)->getInstr());
else
EndLabel = getLabelBeforeInsn(std::next(EI)->getInstr());
assert(EndLabel && "Forgot label after instruction ending a range!");
if (EI->isDbgValue())
LLVM_DEBUG(dbgs() << "DotDebugLoc: " << *Instr << "\n");
// If this history map entry has a debug value, add that to the list of
// open ranges and check if its location is valid for a single value
// location.
if (EI->isDbgValue()) {
// Do not add undef debug values, as they are redundant information in
// the location list entries. An undef debug results in an empty location
// description. If there are any non-undef fragments then padding pieces
// with empty location descriptions will automatically be inserted, and if
// all fragments are undef then the whole location list entry is
// redundant.
if (!Instr->isUndefDebugValue()) {
auto Value = getDebugLocValue(Instr);
OpenRanges.emplace_back(EI->getEndIndex(), Value);
// TODO: Add support for single value fragment locations.
if (Instr->getDebugExpression()->isFragment())
isSafeForSingleLocation = false;
if (!StartDebugMI)
StartDebugMI = Instr;
} else {
isSafeForSingleLocation = false;
}
}
// Location list entries with empty location descriptions are redundant
// information in DWARF, so do not emit those.
if (OpenRanges.empty())
continue;
// Omit entries with empty ranges as they do not have any effect in DWARF.
if (StartLabel == EndLabel) {
LLVM_DEBUG(dbgs() << "Omitting location list entry with empty range.\n");
continue;
}
SmallVector<DbgValueLoc, 4> Values;
for (auto &R : OpenRanges)
Values.push_back(R.second);
DebugLoc.emplace_back(StartLabel, EndLabel, Values);
// Attempt to coalesce the ranges of two otherwise identical
// DebugLocEntries.
auto CurEntry = DebugLoc.rbegin();
LLVM_DEBUG({
dbgs() << CurEntry->getValues().size() << " Values:\n";
for (auto &Value : CurEntry->getValues())
Value.dump();
dbgs() << "-----\n";
});
auto PrevEntry = std::next(CurEntry);
if (PrevEntry != DebugLoc.rend() && PrevEntry->MergeRanges(*CurEntry))
DebugLoc.pop_back();
}
return DebugLoc.size() == 1 && isSafeForSingleLocation &&
validThroughout(LScopes, StartDebugMI, EndMI);
}
DbgEntity *DwarfDebug::createConcreteEntity(DwarfCompileUnit &TheCU,
LexicalScope &Scope,
const DINode *Node,
const DILocation *Location,
const MCSymbol *Sym) {
ensureAbstractEntityIsCreatedIfScoped(TheCU, Node, Scope.getScopeNode());
if (isa<const DILocalVariable>(Node)) {
ConcreteEntities.push_back(
std::make_unique<DbgVariable>(cast<const DILocalVariable>(Node),
Location));
InfoHolder.addScopeVariable(&Scope,
cast<DbgVariable>(ConcreteEntities.back().get()));
} else if (isa<const DILabel>(Node)) {
ConcreteEntities.push_back(
std::make_unique<DbgLabel>(cast<const DILabel>(Node),
Location, Sym));
InfoHolder.addScopeLabel(&Scope,
cast<DbgLabel>(ConcreteEntities.back().get()));
}
return ConcreteEntities.back().get();
}
// Find variables for each lexical scope.
void DwarfDebug::collectEntityInfo(DwarfCompileUnit &TheCU,
const DISubprogram *SP,
DenseSet<InlinedEntity> &Processed) {
// Grab the variable info that was squirreled away in the MMI side-table.
collectVariableInfoFromMFTable(TheCU, Processed);
for (const auto &I : DbgValues) {
InlinedEntity IV = I.first;
if (Processed.count(IV))
continue;
// Instruction ranges, specifying where IV is accessible.
const auto &HistoryMapEntries = I.second;
if (HistoryMapEntries.empty())
continue;
LexicalScope *Scope = nullptr;
const DILocalVariable *LocalVar = cast<DILocalVariable>(IV.first);
if (const DILocation *IA = IV.second)
Scope = LScopes.findInlinedScope(LocalVar->getScope(), IA);
else
Scope = LScopes.findLexicalScope(LocalVar->getScope());
// If variable scope is not found then skip this variable.
if (!Scope)
continue;
Processed.insert(IV);
DbgVariable *RegVar = cast<DbgVariable>(createConcreteEntity(TheCU,
*Scope, LocalVar, IV.second));
const MachineInstr *MInsn = HistoryMapEntries.front().getInstr();
assert(MInsn->isDebugValue() && "History must begin with debug value");
// Check if there is a single DBG_VALUE, valid throughout the var's scope.
// If the history map contains a single debug value, there may be an
// additional entry which clobbers the debug value.
size_t HistSize = HistoryMapEntries.size();
bool SingleValueWithClobber =
HistSize == 2 && HistoryMapEntries[1].isClobber();
if (HistSize == 1 || SingleValueWithClobber) {
const auto *End =
SingleValueWithClobber ? HistoryMapEntries[1].getInstr() : nullptr;
if (validThroughout(LScopes, MInsn, End)) {
RegVar->initializeDbgValue(MInsn);
continue;
}
}
// Do not emit location lists if .debug_loc secton is disabled.
if (!useLocSection())
continue;
// Handle multiple DBG_VALUE instructions describing one variable.
DebugLocStream::ListBuilder List(DebugLocs, TheCU, *Asm, *RegVar, *MInsn);
// Build the location list for this variable.
SmallVector<DebugLocEntry, 8> Entries;
bool isValidSingleLocation = buildLocationList(Entries, HistoryMapEntries);
// Check whether buildLocationList managed to merge all locations to one
// that is valid throughout the variable's scope. If so, produce single
// value location.
if (isValidSingleLocation) {
RegVar->initializeDbgValue(Entries[0].getValues()[0]);
continue;
}
// If the variable has a DIBasicType, extract it. Basic types cannot have
// unique identifiers, so don't bother resolving the type with the
// identifier map.
const DIBasicType *BT = dyn_cast<DIBasicType>(
static_cast<const Metadata *>(LocalVar->getType()));
// Finalize the entry by lowering it into a DWARF bytestream.
for (auto &Entry : Entries)
Entry.finalize(*Asm, List, BT, TheCU);
}
// For each InlinedEntity collected from DBG_LABEL instructions, convert to
// DWARF-related DbgLabel.
for (const auto &I : DbgLabels) {
InlinedEntity IL = I.first;
const MachineInstr *MI = I.second;
if (MI == nullptr)
continue;
LexicalScope *Scope = nullptr;
const DILabel *Label = cast<DILabel>(IL.first);
// The scope could have an extra lexical block file.
const DILocalScope *LocalScope =
Label->getScope()->getNonLexicalBlockFileScope();
// Get inlined DILocation if it is inlined label.
if (const DILocation *IA = IL.second)
Scope = LScopes.findInlinedScope(LocalScope, IA);
else
Scope = LScopes.findLexicalScope(LocalScope);
// If label scope is not found then skip this label.
if (!Scope)
continue;
Processed.insert(IL);
/// At this point, the temporary label is created.
/// Save the temporary label to DbgLabel entity to get the
/// actually address when generating Dwarf DIE.
MCSymbol *Sym = getLabelBeforeInsn(MI);
createConcreteEntity(TheCU, *Scope, Label, IL.second, Sym);
}
// Collect info for variables/labels that were optimized out.
for (const DINode *DN : SP->getRetainedNodes()) {
if (!Processed.insert(InlinedEntity(DN, nullptr)).second)
continue;
LexicalScope *Scope = nullptr;
if (auto *DV = dyn_cast<DILocalVariable>(DN)) {
Scope = LScopes.findLexicalScope(DV->getScope());
} else if (auto *DL = dyn_cast<DILabel>(DN)) {
Scope = LScopes.findLexicalScope(DL->getScope());
}
if (Scope)
createConcreteEntity(TheCU, *Scope, DN, nullptr);
}
}
// Process beginning of an instruction.
void DwarfDebug::beginInstruction(const MachineInstr *MI) {
DebugHandlerBase::beginInstruction(MI);
assert(CurMI);
const auto *SP = MI->getMF()->getFunction().getSubprogram();
if (!SP || SP->getUnit()->getEmissionKind() == DICompileUnit::NoDebug)
return;
// Check if source location changes, but ignore DBG_VALUE and CFI locations.
// If the instruction is part of the function frame setup code, do not emit
// any line record, as there is no correspondence with any user code.
if (MI->isMetaInstruction() || MI->getFlag(MachineInstr::FrameSetup))
return;
const DebugLoc &DL = MI->getDebugLoc();
// When we emit a line-0 record, we don't update PrevInstLoc; so look at
// the last line number actually emitted, to see if it was line 0.
unsigned LastAsmLine =
Asm->OutStreamer->getContext().getCurrentDwarfLoc().getLine();
// Request a label after the call in order to emit AT_return_pc information
// in call site entries. TODO: Add support for targets with delay slots.
if (SP->areAllCallsDescribed() && MI->isCall() && !MI->hasDelaySlot())
requestLabelAfterInsn(MI);
if (DL == PrevInstLoc) {
// If we have an ongoing unspecified location, nothing to do here.
if (!DL)
return;
// We have an explicit location, same as the previous location.
// But we might be coming back to it after a line 0 record.
if (LastAsmLine == 0 && DL.getLine() != 0) {
// Reinstate the source location but not marked as a statement.
const MDNode *Scope = DL.getScope();
recordSourceLine(DL.getLine(), DL.getCol(), Scope, /*Flags=*/0);
}
return;
}
if (!DL) {
// We have an unspecified location, which might want to be line 0.
// If we have already emitted a line-0 record, don't repeat it.
if (LastAsmLine == 0)
return;
// If user said Don't Do That, don't do that.
if (UnknownLocations == Disable)
return;
// See if we have a reason to emit a line-0 record now.
// Reasons to emit a line-0 record include:
// - User asked for it (UnknownLocations).
// - Instruction has a label, so it's referenced from somewhere else,
// possibly debug information; we want it to have a source location.
// - Instruction is at the top of a block; we don't want to inherit the
// location from the physically previous (maybe unrelated) block.
if (UnknownLocations == Enable || PrevLabel ||
(PrevInstBB && PrevInstBB != MI->getParent())) {
// Preserve the file and column numbers, if we can, to save space in
// the encoded line table.
// Do not update PrevInstLoc, it remembers the last non-0 line.
const MDNode *Scope = nullptr;
unsigned Column = 0;
if (PrevInstLoc) {
Scope = PrevInstLoc.getScope();
Column = PrevInstLoc.getCol();
}
recordSourceLine(/*Line=*/0, Column, Scope, /*Flags=*/0);
}
return;
}
// We have an explicit location, different from the previous location.
// Don't repeat a line-0 record, but otherwise emit the new location.
// (The new location might be an explicit line 0, which we do emit.)
if (DL.getLine() == 0 && LastAsmLine == 0)
return;
unsigned Flags = 0;
if (DL == PrologEndLoc) {
Flags |= DWARF2_FLAG_PROLOGUE_END | DWARF2_FLAG_IS_STMT;
PrologEndLoc = DebugLoc();
}
// If the line changed, we call that a new statement; unless we went to
// line 0 and came back, in which case it is not a new statement.
unsigned OldLine = PrevInstLoc ? PrevInstLoc.getLine() : LastAsmLine;
if (DL.getLine() && DL.getLine() != OldLine)
Flags |= DWARF2_FLAG_IS_STMT;
const MDNode *Scope = DL.getScope();
recordSourceLine(DL.getLine(), DL.getCol(), Scope, Flags);
// If we're not at line 0, remember this location.
if (DL.getLine())
PrevInstLoc = DL;
}
static DebugLoc findPrologueEndLoc(const MachineFunction *MF) {
// First known non-DBG_VALUE and non-frame setup location marks
// the beginning of the function body.
for (const auto &MBB : *MF)
for (const auto &MI : MBB)
if (!MI.isMetaInstruction() && !MI.getFlag(MachineInstr::FrameSetup) &&
MI.getDebugLoc())
return MI.getDebugLoc();
return DebugLoc();
}
/// Register a source line with debug info. Returns the unique label that was
/// emitted and which provides correspondence to the source line list.
static void recordSourceLine(AsmPrinter &Asm, unsigned Line, unsigned Col,
const MDNode *S, unsigned Flags, unsigned CUID,
uint16_t DwarfVersion,
ArrayRef<std::unique_ptr<DwarfCompileUnit>> DCUs) {
StringRef Fn;
unsigned FileNo = 1;
unsigned Discriminator = 0;
if (auto *Scope = cast_or_null<DIScope>(S)) {
Fn = Scope->getFilename();
if (Line != 0 && DwarfVersion >= 4)
if (auto *LBF = dyn_cast<DILexicalBlockFile>(Scope))
Discriminator = LBF->getDiscriminator();
FileNo = static_cast<DwarfCompileUnit &>(*DCUs[CUID])
.getOrCreateSourceID(Scope->getFile());
}
Asm.OutStreamer->EmitDwarfLocDirective(FileNo, Line, Col, Flags, 0,
Discriminator, Fn);
}
DebugLoc DwarfDebug::emitInitialLocDirective(const MachineFunction &MF,
unsigned CUID) {
// Get beginning of function.
if (DebugLoc PrologEndLoc = findPrologueEndLoc(&MF)) {
// Ensure the compile unit is created if the function is called before
// beginFunction().
(void)getOrCreateDwarfCompileUnit(
MF.getFunction().getSubprogram()->getUnit());
// We'd like to list the prologue as "not statements" but GDB behaves
// poorly if we do that. Revisit this with caution/GDB (7.5+) testing.
const DISubprogram *SP = PrologEndLoc->getInlinedAtScope()->getSubprogram();
::recordSourceLine(*Asm, SP->getScopeLine(), 0, SP, DWARF2_FLAG_IS_STMT,
CUID, getDwarfVersion(), getUnits());
return PrologEndLoc;
}
return DebugLoc();
}
// Gather pre-function debug information. Assumes being called immediately
// after the function entry point has been emitted.
void DwarfDebug::beginFunctionImpl(const MachineFunction *MF) {
CurFn = MF;
auto *SP = MF->getFunction().getSubprogram();
assert(LScopes.empty() || SP == LScopes.getCurrentFunctionScope()->getScopeNode());
if (SP->getUnit()->getEmissionKind() == DICompileUnit::NoDebug)
return;
SectionLabels.insert(std::make_pair(&Asm->getFunctionBegin()->getSection(),
Asm->getFunctionBegin()));
DwarfCompileUnit &CU = getOrCreateDwarfCompileUnit(SP->getUnit());
// Set DwarfDwarfCompileUnitID in MCContext to the Compile Unit this function
// belongs to so that we add to the correct per-cu line table in the
// non-asm case.
if (Asm->OutStreamer->hasRawTextSupport())
// Use a single line table if we are generating assembly.
Asm->OutStreamer->getContext().setDwarfCompileUnitID(0);
else
Asm->OutStreamer->getContext().setDwarfCompileUnitID(CU.getUniqueID());
// Record beginning of function.
PrologEndLoc = emitInitialLocDirective(
*MF, Asm->OutStreamer->getContext().getDwarfCompileUnitID());
}
void DwarfDebug::skippedNonDebugFunction() {
// If we don't have a subprogram for this function then there will be a hole
// in the range information. Keep note of this by setting the previously used
// section to nullptr.
PrevCU = nullptr;
CurFn = nullptr;
}
// Gather and emit post-function debug information.
void DwarfDebug::endFunctionImpl(const MachineFunction *MF) {
const DISubprogram *SP = MF->getFunction().getSubprogram();
assert(CurFn == MF &&
"endFunction should be called with the same function as beginFunction");
// Set DwarfDwarfCompileUnitID in MCContext to default value.
Asm->OutStreamer->getContext().setDwarfCompileUnitID(0);
LexicalScope *FnScope = LScopes.getCurrentFunctionScope();
assert(!FnScope || SP == FnScope->getScopeNode());
DwarfCompileUnit &TheCU = *CUMap.lookup(SP->getUnit());
if (TheCU.getCUNode()->isDebugDirectivesOnly()) {
PrevLabel = nullptr;
CurFn = nullptr;
return;
}
DenseSet<InlinedEntity> Processed;
collectEntityInfo(TheCU, SP, Processed);
// Add the range of this function to the list of ranges for the CU.
TheCU.addRange({Asm->getFunctionBegin(), Asm->getFunctionEnd()});
// Under -gmlt, skip building the subprogram if there are no inlined
// subroutines inside it. But with -fdebug-info-for-profiling, the subprogram
// is still needed as we need its source location.
if (!TheCU.getCUNode()->getDebugInfoForProfiling() &&
TheCU.getCUNode()->getEmissionKind() == DICompileUnit::LineTablesOnly &&
LScopes.getAbstractScopesList().empty() && !IsDarwin) {
assert(InfoHolder.getScopeVariables().empty());
PrevLabel = nullptr;
CurFn = nullptr;
return;
}
#ifndef NDEBUG
size_t NumAbstractScopes = LScopes.getAbstractScopesList().size();
#endif
// Construct abstract scopes.
for (LexicalScope *AScope : LScopes.getAbstractScopesList()) {
auto *SP = cast<DISubprogram>(AScope->getScopeNode());
for (const DINode *DN : SP->getRetainedNodes()) {
if (!Processed.insert(InlinedEntity(DN, nullptr)).second)
continue;
const MDNode *Scope = nullptr;
if (auto *DV = dyn_cast<DILocalVariable>(DN))
Scope = DV->getScope();
else if (auto *DL = dyn_cast<DILabel>(DN))
Scope = DL->getScope();
else
llvm_unreachable("Unexpected DI type!");
// Collect info for variables/labels that were optimized out.
ensureAbstractEntityIsCreated(TheCU, DN, Scope);
assert(LScopes.getAbstractScopesList().size() == NumAbstractScopes
&& "ensureAbstractEntityIsCreated inserted abstract scopes");
}
constructAbstractSubprogramScopeDIE(TheCU, AScope);
}
ProcessedSPNodes.insert(SP);
DIE &ScopeDIE = TheCU.constructSubprogramScopeDIE(SP, FnScope);
if (auto *SkelCU = TheCU.getSkeleton())
if (!LScopes.getAbstractScopesList().empty() &&
TheCU.getCUNode()->getSplitDebugInlining())
SkelCU->constructSubprogramScopeDIE(SP, FnScope);
// Construct call site entries.
constructCallSiteEntryDIEs(*SP, TheCU, ScopeDIE, *MF);
// Clear debug info
// Ownership of DbgVariables is a bit subtle - ScopeVariables owns all the
// DbgVariables except those that are also in AbstractVariables (since they
// can be used cross-function)
InfoHolder.getScopeVariables().clear();
InfoHolder.getScopeLabels().clear();
PrevLabel = nullptr;
CurFn = nullptr;
}
// Register a source line with debug info. Returns the unique label that was
// emitted and which provides correspondence to the source line list.
void DwarfDebug::recordSourceLine(unsigned Line, unsigned Col, const MDNode *S,
unsigned Flags) {
::recordSourceLine(*Asm, Line, Col, S, Flags,
Asm->OutStreamer->getContext().getDwarfCompileUnitID(),
getDwarfVersion(), getUnits());
}
//===----------------------------------------------------------------------===//
// Emit Methods
//===----------------------------------------------------------------------===//
// Emit the debug info section.
void DwarfDebug::emitDebugInfo() {
DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
Holder.emitUnits(/* UseOffsets */ false);
}
// Emit the abbreviation section.
void DwarfDebug::emitAbbreviations() {
DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
Holder.emitAbbrevs(Asm->getObjFileLowering().getDwarfAbbrevSection());
}
void DwarfDebug::emitStringOffsetsTableHeader() {
DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
Holder.getStringPool().emitStringOffsetsTableHeader(
*Asm, Asm->getObjFileLowering().getDwarfStrOffSection(),
Holder.getStringOffsetsStartSym());
}
template <typename AccelTableT>
void DwarfDebug::emitAccel(AccelTableT &Accel, MCSection *Section,
StringRef TableName) {
Asm->OutStreamer->SwitchSection(Section);
// Emit the full data.
emitAppleAccelTable(Asm, Accel, TableName, Section->getBeginSymbol());
}
void DwarfDebug::emitAccelDebugNames() {
// Don't emit anything if we have no compilation units to index.
if (getUnits().empty())
return;
emitDWARF5AccelTable(Asm, AccelDebugNames, *this, getUnits());
}
// Emit visible names into a hashed accelerator table section.
void DwarfDebug::emitAccelNames() {
emitAccel(AccelNames, Asm->getObjFileLowering().getDwarfAccelNamesSection(),
"Names");
}
// Emit objective C classes and categories into a hashed accelerator table
// section.
void DwarfDebug::emitAccelObjC() {
emitAccel(AccelObjC, Asm->getObjFileLowering().getDwarfAccelObjCSection(),
"ObjC");
}
// Emit namespace dies into a hashed accelerator table.
void DwarfDebug::emitAccelNamespaces() {
emitAccel(AccelNamespace,
Asm->getObjFileLowering().getDwarfAccelNamespaceSection(),
"namespac");
}
// Emit type dies into a hashed accelerator table.
void DwarfDebug::emitAccelTypes() {
emitAccel(AccelTypes, Asm->getObjFileLowering().getDwarfAccelTypesSection(),
"types");
}
// Public name handling.
// The format for the various pubnames:
//
// dwarf pubnames - offset/name pairs where the offset is the offset into the CU
// for the DIE that is named.
//
// gnu pubnames - offset/index value/name tuples where the offset is the offset
// into the CU and the index value is computed according to the type of value
// for the DIE that is named.
//
// For type units the offset is the offset of the skeleton DIE. For split dwarf
// it's the offset within the debug_info/debug_types dwo section, however, the
// reference in the pubname header doesn't change.
/// computeIndexValue - Compute the gdb index value for the DIE and CU.
static dwarf::PubIndexEntryDescriptor computeIndexValue(DwarfUnit *CU,
const DIE *Die) {
// Entities that ended up only in a Type Unit reference the CU instead (since
// the pub entry has offsets within the CU there's no real offset that can be
// provided anyway). As it happens all such entities (namespaces and types,
// types only in C++ at that) are rendered as TYPE+EXTERNAL. If this turns out
// not to be true it would be necessary to persist this information from the
// point at which the entry is added to the index data structure - since by
// the time the index is built from that, the original type/namespace DIE in a
// type unit has already been destroyed so it can't be queried for properties
// like tag, etc.
if (Die->getTag() == dwarf::DW_TAG_compile_unit)
return dwarf::PubIndexEntryDescriptor(dwarf::GIEK_TYPE,
dwarf::GIEL_EXTERNAL);
dwarf::GDBIndexEntryLinkage Linkage = dwarf::GIEL_STATIC;
// We could have a specification DIE that has our most of our knowledge,
// look for that now.
if (DIEValue SpecVal = Die->findAttribute(dwarf::DW_AT_specification)) {
DIE &SpecDIE = SpecVal.getDIEEntry().getEntry();
if (SpecDIE.findAttribute(dwarf::DW_AT_external))
Linkage = dwarf::GIEL_EXTERNAL;
} else if (Die->findAttribute(dwarf::DW_AT_external))
Linkage = dwarf::GIEL_EXTERNAL;
switch (Die->getTag()) {
case dwarf::DW_TAG_class_type:
case dwarf::DW_TAG_structure_type:
case dwarf::DW_TAG_union_type:
case dwarf::DW_TAG_enumeration_type:
return dwarf::PubIndexEntryDescriptor(
dwarf::GIEK_TYPE,
dwarf::isCPlusPlus((dwarf::SourceLanguage)CU->getLanguage())
? dwarf::GIEL_EXTERNAL
: dwarf::GIEL_STATIC);
case dwarf::DW_TAG_typedef:
case dwarf::DW_TAG_base_type:
case dwarf::DW_TAG_subrange_type:
return dwarf::PubIndexEntryDescriptor(dwarf::GIEK_TYPE, dwarf::GIEL_STATIC);
case dwarf::DW_TAG_namespace:
return dwarf::GIEK_TYPE;
case dwarf::DW_TAG_subprogram:
return dwarf::PubIndexEntryDescriptor(dwarf::GIEK_FUNCTION, Linkage);
case dwarf::DW_TAG_variable:
return dwarf::PubIndexEntryDescriptor(dwarf::GIEK_VARIABLE, Linkage);
case dwarf::DW_TAG_enumerator:
return dwarf::PubIndexEntryDescriptor(dwarf::GIEK_VARIABLE,
dwarf::GIEL_STATIC);
default:
return dwarf::GIEK_NONE;
}
}
/// emitDebugPubSections - Emit visible names and types into debug pubnames and
/// pubtypes sections.
void DwarfDebug::emitDebugPubSections() {
for (const auto &NU : CUMap) {
DwarfCompileUnit *TheU = NU.second;
if (!TheU->hasDwarfPubSections())
continue;
bool GnuStyle = TheU->getCUNode()->getNameTableKind() ==
DICompileUnit::DebugNameTableKind::GNU;
Asm->OutStreamer->SwitchSection(
GnuStyle ? Asm->getObjFileLowering().getDwarfGnuPubNamesSection()
: Asm->getObjFileLowering().getDwarfPubNamesSection());
emitDebugPubSection(GnuStyle, "Names", TheU, TheU->getGlobalNames());
Asm->OutStreamer->SwitchSection(
GnuStyle ? Asm->getObjFileLowering().getDwarfGnuPubTypesSection()
: Asm->getObjFileLowering().getDwarfPubTypesSection());
emitDebugPubSection(GnuStyle, "Types", TheU, TheU->getGlobalTypes());
}
}
void DwarfDebug::emitSectionReference(const DwarfCompileUnit &CU) {
if (useSectionsAsReferences())
Asm->EmitDwarfOffset(CU.getSection()->getBeginSymbol(),
CU.getDebugSectionOffset());
else
Asm->emitDwarfSymbolReference(CU.getLabelBegin());
}
void DwarfDebug::emitDebugPubSection(bool GnuStyle, StringRef Name,
DwarfCompileUnit *TheU,
const StringMap<const DIE *> &Globals) {
if (auto *Skeleton = TheU->getSkeleton())
TheU = Skeleton;
// Emit the header.
Asm->OutStreamer->AddComment("Length of Public " + Name + " Info");
MCSymbol *BeginLabel = Asm->createTempSymbol("pub" + Name + "_begin");
MCSymbol *EndLabel = Asm->createTempSymbol("pub" + Name + "_end");
Asm->EmitLabelDifference(EndLabel, BeginLabel, 4);
Asm->OutStreamer->EmitLabel(BeginLabel);
Asm->OutStreamer->AddComment("DWARF Version");
Asm->emitInt16(dwarf::DW_PUBNAMES_VERSION);
Asm->OutStreamer->AddComment("Offset of Compilation Unit Info");
emitSectionReference(*TheU);
Asm->OutStreamer->AddComment("Compilation Unit Length");
Asm->emitInt32(TheU->getLength());
// Emit the pubnames for this compilation unit.
for (const auto &GI : Globals) {
const char *Name = GI.getKeyData();
const DIE *Entity = GI.second;
Asm->OutStreamer->AddComment("DIE offset");
Asm->emitInt32(Entity->getOffset());
if (GnuStyle) {
dwarf::PubIndexEntryDescriptor Desc = computeIndexValue(TheU, Entity);
Asm->OutStreamer->AddComment(
Twine("Attributes: ") + dwarf::GDBIndexEntryKindString(Desc.Kind) +
", " + dwarf::GDBIndexEntryLinkageString(Desc.Linkage));
Asm->emitInt8(Desc.toBits());
}
Asm->OutStreamer->AddComment("External Name");
Asm->OutStreamer->EmitBytes(StringRef(Name, GI.getKeyLength() + 1));
}
Asm->OutStreamer->AddComment("End Mark");
Asm->emitInt32(0);
Asm->OutStreamer->EmitLabel(EndLabel);
}
/// Emit null-terminated strings into a debug str section.
void DwarfDebug::emitDebugStr() {
MCSection *StringOffsetsSection = nullptr;
if (useSegmentedStringOffsetsTable()) {
emitStringOffsetsTableHeader();
StringOffsetsSection = Asm->getObjFileLowering().getDwarfStrOffSection();
}
DwarfFile &Holder = useSplitDwarf() ? SkeletonHolder : InfoHolder;
Holder.emitStrings(Asm->getObjFileLowering().getDwarfStrSection(),
StringOffsetsSection, /* UseRelativeOffsets = */ true);
}
void DwarfDebug::emitDebugLocEntry(ByteStreamer &Streamer,
const DebugLocStream::Entry &Entry,
const DwarfCompileUnit *CU) {
auto &&Comments = DebugLocs.getComments(Entry);
auto Comment = Comments.begin();
auto End = Comments.end();
// The expressions are inserted into a byte stream rather early (see
// DwarfExpression::addExpression) so for those ops (e.g. DW_OP_convert) that
// need to reference a base_type DIE the offset of that DIE is not yet known.
// To deal with this we instead insert a placeholder early and then extract
// it here and replace it with the real reference.
unsigned PtrSize = Asm->MAI->getCodePointerSize();
DWARFDataExtractor Data(StringRef(DebugLocs.getBytes(Entry).data(),
DebugLocs.getBytes(Entry).size()),
Asm->getDataLayout().isLittleEndian(), PtrSize);
DWARFExpression Expr(Data, getDwarfVersion(), PtrSize);
using Encoding = DWARFExpression::Operation::Encoding;
uint64_t Offset = 0;
for (auto &Op : Expr) {
assert(Op.getCode() != dwarf::DW_OP_const_type &&
"3 operand ops not yet supported");
Streamer.EmitInt8(Op.getCode(), Comment != End ? *(Comment++) : "");
Offset++;
for (unsigned I = 0; I < 2; ++I) {
if (Op.getDescription().Op[I] == Encoding::SizeNA)
continue;
if (Op.getDescription().Op[I] == Encoding::BaseTypeRef) {
if (CU) {
uint64_t Offset = CU->ExprRefedBaseTypes[Op.getRawOperand(I)].Die->getOffset();
assert(Offset < (1ULL << (ULEB128PadSize * 7)) && "Offset wont fit");
Asm->EmitULEB128(Offset, nullptr, ULEB128PadSize);
} else {
// Emit a reference to the 'generic type'.
Asm->EmitULEB128(0, nullptr, ULEB128PadSize);
}
// Make sure comments stay aligned.
for (unsigned J = 0; J < ULEB128PadSize; ++J)
if (Comment != End)
Comment++;
} else {
for (uint64_t J = Offset; J < Op.getOperandEndOffset(I); ++J)
Streamer.EmitInt8(Data.getData()[J], Comment != End ? *(Comment++) : "");
}
Offset = Op.getOperandEndOffset(I);
}
assert(Offset == Op.getEndOffset());
}
}
void DwarfDebug::emitDebugLocValue(const AsmPrinter &AP, const DIBasicType *BT,
const DbgValueLoc &Value,
DwarfExpression &DwarfExpr) {
auto *DIExpr = Value.getExpression();
DIExpressionCursor ExprCursor(DIExpr);
DwarfExpr.addFragmentOffset(DIExpr);
// Regular entry.
if (Value.isInt()) {
if (BT && (BT->getEncoding() == dwarf::DW_ATE_signed ||
BT->getEncoding() == dwarf::DW_ATE_signed_char))
DwarfExpr.addSignedConstant(Value.getInt());
else
DwarfExpr.addUnsignedConstant(Value.getInt());
} else if (Value.isLocation()) {
MachineLocation Location = Value.getLoc();
if (Location.isIndirect())
DwarfExpr.setMemoryLocationKind();
DIExpressionCursor Cursor(DIExpr);
if (DIExpr->isEntryValue()) {
DwarfExpr.setEntryValueFlag();
DwarfExpr.beginEntryValueExpression(Cursor);
}
const TargetRegisterInfo &TRI = *AP.MF->getSubtarget().getRegisterInfo();
if (!DwarfExpr.addMachineRegExpression(TRI, Cursor, Location.getReg()))
return;
return DwarfExpr.addExpression(std::move(Cursor));
} else if (Value.isTargetIndexLocation()) {
TargetIndexLocation Loc = Value.getTargetIndexLocation();
// TODO TargetIndexLocation is a target-independent. Currently only the WebAssembly-specific
// encoding is supported.
DwarfExpr.addWasmLocation(Loc.Index, Loc.Offset);
} else if (Value.isConstantFP()) {
APInt RawBytes = Value.getConstantFP()->getValueAPF().bitcastToAPInt();
DwarfExpr.addUnsignedConstant(RawBytes);
}
DwarfExpr.addExpression(std::move(ExprCursor));
}
void DebugLocEntry::finalize(const AsmPrinter &AP,
DebugLocStream::ListBuilder &List,
const DIBasicType *BT,
DwarfCompileUnit &TheCU) {
assert(!Values.empty() &&
"location list entries without values are redundant");
assert(Begin != End && "unexpected location list entry with empty range");
DebugLocStream::EntryBuilder Entry(List, Begin, End);
BufferByteStreamer Streamer = Entry.getStreamer();
DebugLocDwarfExpression DwarfExpr(AP.getDwarfVersion(), Streamer, TheCU);
const DbgValueLoc &Value = Values[0];
if (Value.isFragment()) {
// Emit all fragments that belong to the same variable and range.
assert(llvm::all_of(Values, [](DbgValueLoc P) {
return P.isFragment();
}) && "all values are expected to be fragments");
assert(std::is_sorted(Values.begin(), Values.end()) &&
"fragments are expected to be sorted");
for (auto Fragment : Values)
DwarfDebug::emitDebugLocValue(AP, BT, Fragment, DwarfExpr);
} else {
assert(Values.size() == 1 && "only fragments may have >1 value");
DwarfDebug::emitDebugLocValue(AP, BT, Value, DwarfExpr);
}
DwarfExpr.finalize();
if (DwarfExpr.TagOffset)
List.setTagOffset(*DwarfExpr.TagOffset);
}
void DwarfDebug::emitDebugLocEntryLocation(const DebugLocStream::Entry &Entry,
const DwarfCompileUnit *CU) {
// Emit the size.
Asm->OutStreamer->AddComment("Loc expr size");
if (getDwarfVersion() >= 5)
Asm->EmitULEB128(DebugLocs.getBytes(Entry).size());
else if (DebugLocs.getBytes(Entry).size() <= std::numeric_limits<uint16_t>::max())
Asm->emitInt16(DebugLocs.getBytes(Entry).size());
else {
// The entry is too big to fit into 16 bit, drop it as there is nothing we
// can do.
Asm->emitInt16(0);
return;
}
// Emit the entry.
APByteStreamer Streamer(*Asm);
emitDebugLocEntry(Streamer, Entry, CU);
}
// Emit the common part of the DWARF 5 range/locations list tables header.
static void emitListsTableHeaderStart(AsmPrinter *Asm,
MCSymbol *TableStart,
MCSymbol *TableEnd) {
// Build the table header, which starts with the length field.
Asm->OutStreamer->AddComment("Length");
Asm->EmitLabelDifference(TableEnd, TableStart, 4);
Asm->OutStreamer->EmitLabel(TableStart);
// Version number (DWARF v5 and later).
Asm->OutStreamer->AddComment("Version");
Asm->emitInt16(Asm->OutStreamer->getContext().getDwarfVersion());
// Address size.
Asm->OutStreamer->AddComment("Address size");
Asm->emitInt8(Asm->MAI->getCodePointerSize());
// Segment selector size.
Asm->OutStreamer->AddComment("Segment selector size");
Asm->emitInt8(0);
}
// Emit the header of a DWARF 5 range list table list table. Returns the symbol
// that designates the end of the table for the caller to emit when the table is
// complete.
static MCSymbol *emitRnglistsTableHeader(AsmPrinter *Asm,
const DwarfFile &Holder) {
MCSymbol *TableStart = Asm->createTempSymbol("debug_rnglist_table_start");
MCSymbol *TableEnd = Asm->createTempSymbol("debug_rnglist_table_end");
emitListsTableHeaderStart(Asm, TableStart, TableEnd);
Asm->OutStreamer->AddComment("Offset entry count");
Asm->emitInt32(Holder.getRangeLists().size());
Asm->OutStreamer->EmitLabel(Holder.getRnglistsTableBaseSym());
for (const RangeSpanList &List : Holder.getRangeLists())
Asm->EmitLabelDifference(List.Label, Holder.getRnglistsTableBaseSym(),
4);
return TableEnd;
}
// Emit the header of a DWARF 5 locations list table. Returns the symbol that
// designates the end of the table for the caller to emit when the table is
// complete.
static MCSymbol *emitLoclistsTableHeader(AsmPrinter *Asm,
const DwarfDebug &DD) {
MCSymbol *TableStart = Asm->createTempSymbol("debug_loclist_table_start");
MCSymbol *TableEnd = Asm->createTempSymbol("debug_loclist_table_end");
emitListsTableHeaderStart(Asm, TableStart, TableEnd);
const auto &DebugLocs = DD.getDebugLocs();
Asm->OutStreamer->AddComment("Offset entry count");
Asm->emitInt32(DebugLocs.getLists().size());
Asm->OutStreamer->EmitLabel(DebugLocs.getSym());
for (const auto &List : DebugLocs.getLists())
Asm->EmitLabelDifference(List.Label, DebugLocs.getSym(), 4);
return TableEnd;
}
template <typename Ranges, typename PayloadEmitter>
static void emitRangeList(
DwarfDebug &DD, AsmPrinter *Asm, MCSymbol *Sym, const Ranges &R,
const DwarfCompileUnit &CU, unsigned BaseAddressx, unsigned OffsetPair,
unsigned StartxLength, unsigned EndOfList,
StringRef (*StringifyEnum)(unsigned),
bool ShouldUseBaseAddress,
PayloadEmitter EmitPayload) {
auto Size = Asm->MAI->getCodePointerSize();
bool UseDwarf5 = DD.getDwarfVersion() >= 5;
// Emit our symbol so we can find the beginning of the range.
Asm->OutStreamer->EmitLabel(Sym);
// Gather all the ranges that apply to the same section so they can share
// a base address entry.
MapVector<const MCSection *, std::vector<decltype(&*R.begin())>> SectionRanges;
for (const auto &Range : R)
SectionRanges[&Range.Begin->getSection()].push_back(&Range);
const MCSymbol *CUBase = CU.getBaseAddress();
bool BaseIsSet = false;
for (const auto &P : SectionRanges) {
auto *Base = CUBase;
if (!Base && ShouldUseBaseAddress) {
const MCSymbol *Begin = P.second.front()->Begin;
const MCSymbol *NewBase = DD.getSectionLabel(&Begin->getSection());
if (!UseDwarf5) {
Base = NewBase;
BaseIsSet = true;
Asm->OutStreamer->EmitIntValue(-1, Size);
Asm->OutStreamer->AddComment(" base address");
Asm->OutStreamer->EmitSymbolValue(Base, Size);
} else if (NewBase != Begin || P.second.size() > 1) {
// Only use a base address if
// * the existing pool address doesn't match (NewBase != Begin)
// * or, there's more than one entry to share the base address
Base = NewBase;
BaseIsSet = true;
Asm->OutStreamer->AddComment(StringifyEnum(BaseAddressx));
Asm->emitInt8(BaseAddressx);
Asm->OutStreamer->AddComment(" base address index");
Asm->EmitULEB128(DD.getAddressPool().getIndex(Base));
}
} else if (BaseIsSet && !UseDwarf5) {
BaseIsSet = false;
assert(!Base);
Asm->OutStreamer->EmitIntValue(-1, Size);
Asm->OutStreamer->EmitIntValue(0, Size);
}
for (const auto *RS : P.second) {
const MCSymbol *Begin = RS->Begin;
const MCSymbol *End = RS->End;
assert(Begin && "Range without a begin symbol?");
assert(End && "Range without an end symbol?");
if (Base) {
if (UseDwarf5) {
// Emit offset_pair when we have a base.
Asm->OutStreamer->AddComment(StringifyEnum(OffsetPair));
Asm->emitInt8(OffsetPair);
Asm->OutStreamer->AddComment(" starting offset");
Asm->EmitLabelDifferenceAsULEB128(Begin, Base);