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MCDwarf.cpp
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//===- lib/MC/MCDwarf.cpp - MCDwarf implementation ------------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCDwarf.h"
#include "llvm/ADT/ArrayRef.h"
#include "llvm/ADT/DenseMap.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/Optional.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Twine.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/Config/config.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/StringTableBuilder.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/Endian.h"
#include "llvm/Support/EndianStream.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/MathExtras.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/raw_ostream.h"
#include <cassert>
#include <cstdint>
#include <string>
#include <utility>
#include <vector>
using namespace llvm;
MCSymbol *mcdwarf::emitListsTableHeaderStart(MCStreamer &S) {
MCSymbol *Start =
S.getContext().createTempSymbol("debug_list_header_start", true, true);
MCSymbol *End =
S.getContext().createTempSymbol("debug_list_header_end", true, true);
S.AddComment("Length");
S.emitAbsoluteSymbolDiff(End, Start, 4);
S.emitLabel(Start);
S.AddComment("Version");
S.emitInt16(S.getContext().getDwarfVersion());
S.AddComment("Address size");
S.emitInt8(S.getContext().getAsmInfo()->getCodePointerSize());
S.AddComment("Segment selector size");
S.emitInt8(0);
return End;
}
/// Manage the .debug_line_str section contents, if we use it.
class llvm::MCDwarfLineStr {
MCSymbol *LineStrLabel = nullptr;
StringTableBuilder LineStrings{StringTableBuilder::DWARF};
bool UseRelocs = false;
public:
/// Construct an instance that can emit .debug_line_str (for use in a normal
/// v5 line table).
explicit MCDwarfLineStr(MCContext &Ctx) {
UseRelocs = Ctx.getAsmInfo()->doesDwarfUseRelocationsAcrossSections();
if (UseRelocs)
LineStrLabel =
Ctx.getObjectFileInfo()->getDwarfLineStrSection()->getBeginSymbol();
}
/// Emit a reference to the string.
void emitRef(MCStreamer *MCOS, StringRef Path);
/// Emit the .debug_line_str section if appropriate.
void emitSection(MCStreamer *MCOS);
};
static inline uint64_t ScaleAddrDelta(MCContext &Context, uint64_t AddrDelta) {
unsigned MinInsnLength = Context.getAsmInfo()->getMinInstAlignment();
if (MinInsnLength == 1)
return AddrDelta;
if (AddrDelta % MinInsnLength != 0) {
// TODO: report this error, but really only once.
;
}
return AddrDelta / MinInsnLength;
}
//
// This is called when an instruction is assembled into the specified section
// and if there is information from the last .loc directive that has yet to have
// a line entry made for it is made.
//
void MCDwarfLineEntry::Make(MCObjectStreamer *MCOS, MCSection *Section) {
if (!MCOS->getContext().getDwarfLocSeen())
return;
// Create a symbol at in the current section for use in the line entry.
MCSymbol *LineSym = MCOS->getContext().createTempSymbol();
// Set the value of the symbol to use for the MCDwarfLineEntry.
MCOS->emitLabel(LineSym);
// Get the current .loc info saved in the context.
const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();
// Create a (local) line entry with the symbol and the current .loc info.
MCDwarfLineEntry LineEntry(LineSym, DwarfLoc);
// clear DwarfLocSeen saying the current .loc info is now used.
MCOS->getContext().clearDwarfLocSeen();
// Add the line entry to this section's entries.
MCOS->getContext()
.getMCDwarfLineTable(MCOS->getContext().getDwarfCompileUnitID())
.getMCLineSections()
.addLineEntry(LineEntry, Section);
}
//
// This helper routine returns an expression of End - Start + IntVal .
//
static inline const MCExpr *MakeStartMinusEndExpr(const MCStreamer &MCOS,
const MCSymbol &Start,
const MCSymbol &End,
int IntVal) {
MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
const MCExpr *Res =
MCSymbolRefExpr::create(&End, Variant, MCOS.getContext());
const MCExpr *RHS =
MCSymbolRefExpr::create(&Start, Variant, MCOS.getContext());
const MCExpr *Res1 =
MCBinaryExpr::create(MCBinaryExpr::Sub, Res, RHS, MCOS.getContext());
const MCExpr *Res2 =
MCConstantExpr::create(IntVal, MCOS.getContext());
const MCExpr *Res3 =
MCBinaryExpr::create(MCBinaryExpr::Sub, Res1, Res2, MCOS.getContext());
return Res3;
}
//
// This helper routine returns an expression of Start + IntVal .
//
static inline const MCExpr *
makeStartPlusIntExpr(MCContext &Ctx, const MCSymbol &Start, int IntVal) {
MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
const MCExpr *LHS = MCSymbolRefExpr::create(&Start, Variant, Ctx);
const MCExpr *RHS = MCConstantExpr::create(IntVal, Ctx);
const MCExpr *Res = MCBinaryExpr::create(MCBinaryExpr::Add, LHS, RHS, Ctx);
return Res;
}
//
// This emits the Dwarf line table for the specified section from the entries
// in the LineSection.
//
static inline void emitDwarfLineTable(
MCObjectStreamer *MCOS, MCSection *Section,
const MCLineSection::MCDwarfLineEntryCollection &LineEntries) {
unsigned FileNum = 1;
unsigned LastLine = 1;
unsigned Column = 0;
unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
unsigned Isa = 0;
unsigned Discriminator = 0;
MCSymbol *LastLabel = nullptr;
// Loop through each MCDwarfLineEntry and encode the dwarf line number table.
for (const MCDwarfLineEntry &LineEntry : LineEntries) {
int64_t LineDelta = static_cast<int64_t>(LineEntry.getLine()) - LastLine;
if (FileNum != LineEntry.getFileNum()) {
FileNum = LineEntry.getFileNum();
MCOS->emitInt8(dwarf::DW_LNS_set_file);
MCOS->emitULEB128IntValue(FileNum);
}
if (Column != LineEntry.getColumn()) {
Column = LineEntry.getColumn();
MCOS->emitInt8(dwarf::DW_LNS_set_column);
MCOS->emitULEB128IntValue(Column);
}
if (Discriminator != LineEntry.getDiscriminator() &&
MCOS->getContext().getDwarfVersion() >= 4) {
Discriminator = LineEntry.getDiscriminator();
unsigned Size = getULEB128Size(Discriminator);
MCOS->emitInt8(dwarf::DW_LNS_extended_op);
MCOS->emitULEB128IntValue(Size + 1);
MCOS->emitInt8(dwarf::DW_LNE_set_discriminator);
MCOS->emitULEB128IntValue(Discriminator);
}
if (Isa != LineEntry.getIsa()) {
Isa = LineEntry.getIsa();
MCOS->emitInt8(dwarf::DW_LNS_set_isa);
MCOS->emitULEB128IntValue(Isa);
}
if ((LineEntry.getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
Flags = LineEntry.getFlags();
MCOS->emitInt8(dwarf::DW_LNS_negate_stmt);
}
if (LineEntry.getFlags() & DWARF2_FLAG_BASIC_BLOCK)
MCOS->emitInt8(dwarf::DW_LNS_set_basic_block);
if (LineEntry.getFlags() & DWARF2_FLAG_PROLOGUE_END)
MCOS->emitInt8(dwarf::DW_LNS_set_prologue_end);
if (LineEntry.getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
MCOS->emitInt8(dwarf::DW_LNS_set_epilogue_begin);
MCSymbol *Label = LineEntry.getLabel();
// At this point we want to emit/create the sequence to encode the delta in
// line numbers and the increment of the address from the previous Label
// and the current Label.
const MCAsmInfo *asmInfo = MCOS->getContext().getAsmInfo();
MCOS->emitDwarfAdvanceLineAddr(LineDelta, LastLabel, Label,
asmInfo->getCodePointerSize());
Discriminator = 0;
LastLine = LineEntry.getLine();
LastLabel = Label;
}
// Emit a DW_LNE_end_sequence for the end of the section.
// Use the section end label to compute the address delta and use INT64_MAX
// as the line delta which is the signal that this is actually a
// DW_LNE_end_sequence.
MCSymbol *SectionEnd = MCOS->endSection(Section);
// Switch back the dwarf line section, in case endSection had to switch the
// section.
MCContext &Ctx = MCOS->getContext();
MCOS->SwitchSection(Ctx.getObjectFileInfo()->getDwarfLineSection());
const MCAsmInfo *AsmInfo = Ctx.getAsmInfo();
MCOS->emitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, SectionEnd,
AsmInfo->getCodePointerSize());
}
//
// This emits the Dwarf file and the line tables.
//
void MCDwarfLineTable::Emit(MCObjectStreamer *MCOS,
MCDwarfLineTableParams Params) {
MCContext &context = MCOS->getContext();
auto &LineTables = context.getMCDwarfLineTables();
// Bail out early so we don't switch to the debug_line section needlessly and
// in doing so create an unnecessary (if empty) section.
if (LineTables.empty())
return;
// In a v5 non-split line table, put the strings in a separate section.
Optional<MCDwarfLineStr> LineStr;
if (context.getDwarfVersion() >= 5)
LineStr = MCDwarfLineStr(context);
// Switch to the section where the table will be emitted into.
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfLineSection());
// Handle the rest of the Compile Units.
for (const auto &CUIDTablePair : LineTables) {
CUIDTablePair.second.EmitCU(MCOS, Params, LineStr);
}
if (LineStr)
LineStr->emitSection(MCOS);
}
void MCDwarfDwoLineTable::Emit(MCStreamer &MCOS, MCDwarfLineTableParams Params,
MCSection *Section) const {
if (!HasSplitLineTable)
return;
Optional<MCDwarfLineStr> NoLineStr(None);
MCOS.SwitchSection(Section);
MCOS.emitLabel(Header.Emit(&MCOS, Params, None, NoLineStr).second);
}
std::pair<MCSymbol *, MCSymbol *>
MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
Optional<MCDwarfLineStr> &LineStr) const {
static const char StandardOpcodeLengths[] = {
0, // length of DW_LNS_copy
1, // length of DW_LNS_advance_pc
1, // length of DW_LNS_advance_line
1, // length of DW_LNS_set_file
1, // length of DW_LNS_set_column
0, // length of DW_LNS_negate_stmt
0, // length of DW_LNS_set_basic_block
0, // length of DW_LNS_const_add_pc
1, // length of DW_LNS_fixed_advance_pc
0, // length of DW_LNS_set_prologue_end
0, // length of DW_LNS_set_epilogue_begin
1 // DW_LNS_set_isa
};
assert(array_lengthof(StandardOpcodeLengths) >=
(Params.DWARF2LineOpcodeBase - 1U));
return Emit(
MCOS, Params,
makeArrayRef(StandardOpcodeLengths, Params.DWARF2LineOpcodeBase - 1),
LineStr);
}
static const MCExpr *forceExpAbs(MCStreamer &OS, const MCExpr* Expr) {
MCContext &Context = OS.getContext();
assert(!isa<MCSymbolRefExpr>(Expr));
if (Context.getAsmInfo()->hasAggressiveSymbolFolding())
return Expr;
MCSymbol *ABS = Context.createTempSymbol();
OS.emitAssignment(ABS, Expr);
return MCSymbolRefExpr::create(ABS, Context);
}
static void emitAbsValue(MCStreamer &OS, const MCExpr *Value, unsigned Size) {
const MCExpr *ABS = forceExpAbs(OS, Value);
OS.emitValue(ABS, Size);
}
void MCDwarfLineStr::emitSection(MCStreamer *MCOS) {
// Switch to the .debug_line_str section.
MCOS->SwitchSection(
MCOS->getContext().getObjectFileInfo()->getDwarfLineStrSection());
// Emit the strings without perturbing the offsets we used.
LineStrings.finalizeInOrder();
SmallString<0> Data;
Data.resize(LineStrings.getSize());
LineStrings.write((uint8_t *)Data.data());
MCOS->emitBinaryData(Data.str());
}
void MCDwarfLineStr::emitRef(MCStreamer *MCOS, StringRef Path) {
int RefSize = 4; // FIXME: Support DWARF-64
size_t Offset = LineStrings.add(Path);
if (UseRelocs) {
MCContext &Ctx = MCOS->getContext();
MCOS->emitValue(makeStartPlusIntExpr(Ctx, *LineStrLabel, Offset), RefSize);
} else
MCOS->emitIntValue(Offset, RefSize);
}
void MCDwarfLineTableHeader::emitV2FileDirTables(MCStreamer *MCOS) const {
// First the directory table.
for (auto &Dir : MCDwarfDirs) {
MCOS->emitBytes(Dir); // The DirectoryName, and...
MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
}
MCOS->emitInt8(0); // Terminate the directory list.
// Second the file table.
for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
assert(!MCDwarfFiles[i].Name.empty());
MCOS->emitBytes(MCDwarfFiles[i].Name); // FileName and...
MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
MCOS->emitULEB128IntValue(MCDwarfFiles[i].DirIndex); // Directory number.
MCOS->emitInt8(0); // Last modification timestamp (always 0).
MCOS->emitInt8(0); // File size (always 0).
}
MCOS->emitInt8(0); // Terminate the file list.
}
static void emitOneV5FileEntry(MCStreamer *MCOS, const MCDwarfFile &DwarfFile,
bool EmitMD5, bool HasSource,
Optional<MCDwarfLineStr> &LineStr) {
assert(!DwarfFile.Name.empty());
if (LineStr)
LineStr->emitRef(MCOS, DwarfFile.Name);
else {
MCOS->emitBytes(DwarfFile.Name); // FileName and...
MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
}
MCOS->emitULEB128IntValue(DwarfFile.DirIndex); // Directory number.
if (EmitMD5) {
const MD5::MD5Result &Cksum = *DwarfFile.Checksum;
MCOS->emitBinaryData(
StringRef(reinterpret_cast<const char *>(Cksum.Bytes.data()),
Cksum.Bytes.size()));
}
if (HasSource) {
if (LineStr)
LineStr->emitRef(MCOS, DwarfFile.Source.getValueOr(StringRef()));
else {
MCOS->emitBytes(
DwarfFile.Source.getValueOr(StringRef())); // Source and...
MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
}
}
}
void MCDwarfLineTableHeader::emitV5FileDirTables(
MCStreamer *MCOS, Optional<MCDwarfLineStr> &LineStr) const {
// The directory format, which is just a list of the directory paths. In a
// non-split object, these are references to .debug_line_str; in a split
// object, they are inline strings.
MCOS->emitInt8(1);
MCOS->emitULEB128IntValue(dwarf::DW_LNCT_path);
MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
: dwarf::DW_FORM_string);
MCOS->emitULEB128IntValue(MCDwarfDirs.size() + 1);
// Try not to emit an empty compilation directory.
const StringRef CompDir = CompilationDir.empty()
? MCOS->getContext().getCompilationDir()
: StringRef(CompilationDir);
if (LineStr) {
// Record path strings, emit references here.
LineStr->emitRef(MCOS, CompDir);
for (const auto &Dir : MCDwarfDirs)
LineStr->emitRef(MCOS, Dir);
} else {
// The list of directory paths. Compilation directory comes first.
MCOS->emitBytes(CompDir);
MCOS->emitBytes(StringRef("\0", 1));
for (const auto &Dir : MCDwarfDirs) {
MCOS->emitBytes(Dir); // The DirectoryName, and...
MCOS->emitBytes(StringRef("\0", 1)); // its null terminator.
}
}
// The file format, which is the inline null-terminated filename and a
// directory index. We don't track file size/timestamp so don't emit them
// in the v5 table. Emit MD5 checksums and source if we have them.
uint64_t Entries = 2;
if (HasAllMD5)
Entries += 1;
if (HasSource)
Entries += 1;
MCOS->emitInt8(Entries);
MCOS->emitULEB128IntValue(dwarf::DW_LNCT_path);
MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
: dwarf::DW_FORM_string);
MCOS->emitULEB128IntValue(dwarf::DW_LNCT_directory_index);
MCOS->emitULEB128IntValue(dwarf::DW_FORM_udata);
if (HasAllMD5) {
MCOS->emitULEB128IntValue(dwarf::DW_LNCT_MD5);
MCOS->emitULEB128IntValue(dwarf::DW_FORM_data16);
}
if (HasSource) {
MCOS->emitULEB128IntValue(dwarf::DW_LNCT_LLVM_source);
MCOS->emitULEB128IntValue(LineStr ? dwarf::DW_FORM_line_strp
: dwarf::DW_FORM_string);
}
// Then the counted list of files. The root file is file #0, then emit the
// files as provide by .file directives.
// MCDwarfFiles has an unused element [0] so use size() not size()+1.
// But sometimes MCDwarfFiles is empty, in which case we still emit one file.
MCOS->emitULEB128IntValue(MCDwarfFiles.empty() ? 1 : MCDwarfFiles.size());
// To accommodate assembler source written for DWARF v4 but trying to emit
// v5: If we didn't see a root file explicitly, replicate file #1.
assert((!RootFile.Name.empty() || MCDwarfFiles.size() >= 1) &&
"No root file and no .file directives");
emitOneV5FileEntry(MCOS, RootFile.Name.empty() ? MCDwarfFiles[1] : RootFile,
HasAllMD5, HasSource, LineStr);
for (unsigned i = 1; i < MCDwarfFiles.size(); ++i)
emitOneV5FileEntry(MCOS, MCDwarfFiles[i], HasAllMD5, HasSource, LineStr);
}
std::pair<MCSymbol *, MCSymbol *>
MCDwarfLineTableHeader::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
ArrayRef<char> StandardOpcodeLengths,
Optional<MCDwarfLineStr> &LineStr) const {
MCContext &context = MCOS->getContext();
// Create a symbol at the beginning of the line table.
MCSymbol *LineStartSym = Label;
if (!LineStartSym)
LineStartSym = context.createTempSymbol();
// Set the value of the symbol, as we are at the start of the line table.
MCOS->emitLabel(LineStartSym);
// Create a symbol for the end of the section (to be set when we get there).
MCSymbol *LineEndSym = context.createTempSymbol();
// The first 4 bytes is the total length of the information for this
// compilation unit (not including these 4 bytes for the length).
emitAbsValue(*MCOS,
MakeStartMinusEndExpr(*MCOS, *LineStartSym, *LineEndSym, 4), 4);
// Next 2 bytes is the Version.
unsigned LineTableVersion = context.getDwarfVersion();
MCOS->emitInt16(LineTableVersion);
// Keep track of the bytes between the very start and where the header length
// comes out.
unsigned PreHeaderLengthBytes = 4 + 2;
// In v5, we get address info next.
if (LineTableVersion >= 5) {
MCOS->emitInt8(context.getAsmInfo()->getCodePointerSize());
MCOS->emitInt8(0); // Segment selector; same as EmitGenDwarfAranges.
PreHeaderLengthBytes += 2;
}
// Create a symbol for the end of the prologue (to be set when we get there).
MCSymbol *ProEndSym = context.createTempSymbol(); // Lprologue_end
// Length of the prologue, is the next 4 bytes. This is actually the length
// from after the length word, to the end of the prologue.
emitAbsValue(*MCOS,
MakeStartMinusEndExpr(*MCOS, *LineStartSym, *ProEndSym,
(PreHeaderLengthBytes + 4)),
4);
// Parameters of the state machine, are next.
MCOS->emitInt8(context.getAsmInfo()->getMinInstAlignment());
// maximum_operations_per_instruction
// For non-VLIW architectures this field is always 1.
// FIXME: VLIW architectures need to update this field accordingly.
if (LineTableVersion >= 4)
MCOS->emitInt8(1);
MCOS->emitInt8(DWARF2_LINE_DEFAULT_IS_STMT);
MCOS->emitInt8(Params.DWARF2LineBase);
MCOS->emitInt8(Params.DWARF2LineRange);
MCOS->emitInt8(StandardOpcodeLengths.size() + 1);
// Standard opcode lengths
for (char Length : StandardOpcodeLengths)
MCOS->emitInt8(Length);
// Put out the directory and file tables. The formats vary depending on
// the version.
if (LineTableVersion >= 5)
emitV5FileDirTables(MCOS, LineStr);
else
emitV2FileDirTables(MCOS);
// This is the end of the prologue, so set the value of the symbol at the
// end of the prologue (that was used in a previous expression).
MCOS->emitLabel(ProEndSym);
return std::make_pair(LineStartSym, LineEndSym);
}
void MCDwarfLineTable::EmitCU(MCObjectStreamer *MCOS,
MCDwarfLineTableParams Params,
Optional<MCDwarfLineStr> &LineStr) const {
MCSymbol *LineEndSym = Header.Emit(MCOS, Params, LineStr).second;
// Put out the line tables.
for (const auto &LineSec : MCLineSections.getMCLineEntries())
emitDwarfLineTable(MCOS, LineSec.first, LineSec.second);
// This is the end of the section, so set the value of the symbol at the end
// of this section (that was used in a previous expression).
MCOS->emitLabel(LineEndSym);
}
Expected<unsigned> MCDwarfLineTable::tryGetFile(StringRef &Directory,
StringRef &FileName,
Optional<MD5::MD5Result> Checksum,
Optional<StringRef> Source,
uint16_t DwarfVersion,
unsigned FileNumber) {
return Header.tryGetFile(Directory, FileName, Checksum, Source, DwarfVersion,
FileNumber);
}
static bool isRootFile(const MCDwarfFile &RootFile, StringRef &Directory,
StringRef &FileName, Optional<MD5::MD5Result> Checksum) {
if (RootFile.Name.empty() || RootFile.Name != FileName.data())
return false;
return RootFile.Checksum == Checksum;
}
Expected<unsigned>
MCDwarfLineTableHeader::tryGetFile(StringRef &Directory,
StringRef &FileName,
Optional<MD5::MD5Result> Checksum,
Optional<StringRef> Source,
uint16_t DwarfVersion,
unsigned FileNumber) {
if (Directory == CompilationDir)
Directory = "";
if (FileName.empty()) {
FileName = "<stdin>";
Directory = "";
}
assert(!FileName.empty());
// Keep track of whether any or all files have an MD5 checksum.
// If any files have embedded source, they all must.
if (MCDwarfFiles.empty()) {
trackMD5Usage(Checksum.hasValue());
HasSource = (Source != None);
}
if (isRootFile(RootFile, Directory, FileName, Checksum) && DwarfVersion >= 5)
return 0;
if (FileNumber == 0) {
// File numbers start with 1 and/or after any file numbers
// allocated by inline-assembler .file directives.
FileNumber = MCDwarfFiles.empty() ? 1 : MCDwarfFiles.size();
SmallString<256> Buffer;
auto IterBool = SourceIdMap.insert(
std::make_pair((Directory + Twine('\0') + FileName).toStringRef(Buffer),
FileNumber));
if (!IterBool.second)
return IterBool.first->second;
}
// Make space for this FileNumber in the MCDwarfFiles vector if needed.
if (FileNumber >= MCDwarfFiles.size())
MCDwarfFiles.resize(FileNumber + 1);
// Get the new MCDwarfFile slot for this FileNumber.
MCDwarfFile &File = MCDwarfFiles[FileNumber];
// It is an error to see the same number more than once.
if (!File.Name.empty())
return make_error<StringError>("file number already allocated",
inconvertibleErrorCode());
// If any files have embedded source, they all must.
if (HasSource != (Source != None))
return make_error<StringError>("inconsistent use of embedded source",
inconvertibleErrorCode());
if (Directory.empty()) {
// Separate the directory part from the basename of the FileName.
StringRef tFileName = sys::path::filename(FileName);
if (!tFileName.empty()) {
Directory = sys::path::parent_path(FileName);
if (!Directory.empty())
FileName = tFileName;
}
}
// Find or make an entry in the MCDwarfDirs vector for this Directory.
// Capture directory name.
unsigned DirIndex;
if (Directory.empty()) {
// For FileNames with no directories a DirIndex of 0 is used.
DirIndex = 0;
} else {
DirIndex = llvm::find(MCDwarfDirs, Directory) - MCDwarfDirs.begin();
if (DirIndex >= MCDwarfDirs.size())
MCDwarfDirs.push_back(std::string(Directory));
// The DirIndex is one based, as DirIndex of 0 is used for FileNames with
// no directories. MCDwarfDirs[] is unlike MCDwarfFiles[] in that the
// directory names are stored at MCDwarfDirs[DirIndex-1] where FileNames
// are stored at MCDwarfFiles[FileNumber].Name .
DirIndex++;
}
File.Name = std::string(FileName);
File.DirIndex = DirIndex;
File.Checksum = Checksum;
trackMD5Usage(Checksum.hasValue());
File.Source = Source;
if (Source)
HasSource = true;
// return the allocated FileNumber.
return FileNumber;
}
/// Utility function to emit the encoding to a streamer.
void MCDwarfLineAddr::Emit(MCStreamer *MCOS, MCDwarfLineTableParams Params,
int64_t LineDelta, uint64_t AddrDelta) {
MCContext &Context = MCOS->getContext();
SmallString<256> Tmp;
raw_svector_ostream OS(Tmp);
MCDwarfLineAddr::Encode(Context, Params, LineDelta, AddrDelta, OS);
MCOS->emitBytes(OS.str());
}
/// Given a special op, return the address skip amount (in units of
/// DWARF2_LINE_MIN_INSN_LENGTH).
static uint64_t SpecialAddr(MCDwarfLineTableParams Params, uint64_t op) {
return (op - Params.DWARF2LineOpcodeBase) / Params.DWARF2LineRange;
}
/// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
void MCDwarfLineAddr::Encode(MCContext &Context, MCDwarfLineTableParams Params,
int64_t LineDelta, uint64_t AddrDelta,
raw_ostream &OS) {
uint64_t Temp, Opcode;
bool NeedCopy = false;
// The maximum address skip amount that can be encoded with a special op.
uint64_t MaxSpecialAddrDelta = SpecialAddr(Params, 255);
// Scale the address delta by the minimum instruction length.
AddrDelta = ScaleAddrDelta(Context, AddrDelta);
// A LineDelta of INT64_MAX is a signal that this is actually a
// DW_LNE_end_sequence. We cannot use special opcodes here, since we want the
// end_sequence to emit the matrix entry.
if (LineDelta == INT64_MAX) {
if (AddrDelta == MaxSpecialAddrDelta)
OS << char(dwarf::DW_LNS_const_add_pc);
else if (AddrDelta) {
OS << char(dwarf::DW_LNS_advance_pc);
encodeULEB128(AddrDelta, OS);
}
OS << char(dwarf::DW_LNS_extended_op);
OS << char(1);
OS << char(dwarf::DW_LNE_end_sequence);
return;
}
// Bias the line delta by the base.
Temp = LineDelta - Params.DWARF2LineBase;
// If the line increment is out of range of a special opcode, we must encode
// it with DW_LNS_advance_line.
if (Temp >= Params.DWARF2LineRange ||
Temp + Params.DWARF2LineOpcodeBase > 255) {
OS << char(dwarf::DW_LNS_advance_line);
encodeSLEB128(LineDelta, OS);
LineDelta = 0;
Temp = 0 - Params.DWARF2LineBase;
NeedCopy = true;
}
// Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
if (LineDelta == 0 && AddrDelta == 0) {
OS << char(dwarf::DW_LNS_copy);
return;
}
// Bias the opcode by the special opcode base.
Temp += Params.DWARF2LineOpcodeBase;
// Avoid overflow when addr_delta is large.
if (AddrDelta < 256 + MaxSpecialAddrDelta) {
// Try using a special opcode.
Opcode = Temp + AddrDelta * Params.DWARF2LineRange;
if (Opcode <= 255) {
OS << char(Opcode);
return;
}
// Try using DW_LNS_const_add_pc followed by special op.
Opcode = Temp + (AddrDelta - MaxSpecialAddrDelta) * Params.DWARF2LineRange;
if (Opcode <= 255) {
OS << char(dwarf::DW_LNS_const_add_pc);
OS << char(Opcode);
return;
}
}
// Otherwise use DW_LNS_advance_pc.
OS << char(dwarf::DW_LNS_advance_pc);
encodeULEB128(AddrDelta, OS);
if (NeedCopy)
OS << char(dwarf::DW_LNS_copy);
else {
assert(Temp <= 255 && "Buggy special opcode encoding.");
OS << char(Temp);
}
}
bool MCDwarfLineAddr::FixedEncode(MCContext &Context,
MCDwarfLineTableParams Params,
int64_t LineDelta, uint64_t AddrDelta,
raw_ostream &OS,
uint32_t *Offset, uint32_t *Size) {
if (LineDelta != INT64_MAX) {
OS << char(dwarf::DW_LNS_advance_line);
encodeSLEB128(LineDelta, OS);
}
// Use address delta to adjust address or use absolute address to adjust
// address.
bool SetDelta;
// According to DWARF spec., the DW_LNS_fixed_advance_pc opcode takes a
// single uhalf (unencoded) operand. So, the maximum value of AddrDelta
// is 65535. We set a conservative upper bound for it for relaxation.
if (AddrDelta > 60000) {
const MCAsmInfo *asmInfo = Context.getAsmInfo();
unsigned AddrSize = asmInfo->getCodePointerSize();
OS << char(dwarf::DW_LNS_extended_op);
encodeULEB128(1 + AddrSize, OS);
OS << char(dwarf::DW_LNE_set_address);
// Generate fixup for the address.
*Offset = OS.tell();
*Size = AddrSize;
SetDelta = false;
OS.write_zeros(AddrSize);
} else {
OS << char(dwarf::DW_LNS_fixed_advance_pc);
// Generate fixup for 2-bytes address delta.
*Offset = OS.tell();
*Size = 2;
SetDelta = true;
OS << char(0);
OS << char(0);
}
if (LineDelta == INT64_MAX) {
OS << char(dwarf::DW_LNS_extended_op);
OS << char(1);
OS << char(dwarf::DW_LNE_end_sequence);
} else {
OS << char(dwarf::DW_LNS_copy);
}
return SetDelta;
}
// Utility function to write a tuple for .debug_abbrev.
static void EmitAbbrev(MCStreamer *MCOS, uint64_t Name, uint64_t Form) {
MCOS->emitULEB128IntValue(Name);
MCOS->emitULEB128IntValue(Form);
}
// When generating dwarf for assembly source files this emits
// the data for .debug_abbrev section which contains three DIEs.
static void EmitGenDwarfAbbrev(MCStreamer *MCOS) {
MCContext &context = MCOS->getContext();
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
// DW_TAG_compile_unit DIE abbrev (1).
MCOS->emitULEB128IntValue(1);
MCOS->emitULEB128IntValue(dwarf::DW_TAG_compile_unit);
MCOS->emitInt8(dwarf::DW_CHILDREN_yes);
EmitAbbrev(MCOS, dwarf::DW_AT_stmt_list, context.getDwarfVersion() >= 4
? dwarf::DW_FORM_sec_offset
: dwarf::DW_FORM_data4);
if (context.getGenDwarfSectionSyms().size() > 1 &&
context.getDwarfVersion() >= 3) {
EmitAbbrev(MCOS, dwarf::DW_AT_ranges, context.getDwarfVersion() >= 4
? dwarf::DW_FORM_sec_offset
: dwarf::DW_FORM_data4);
} else {
EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
EmitAbbrev(MCOS, dwarf::DW_AT_high_pc, dwarf::DW_FORM_addr);
}
EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
if (!context.getCompilationDir().empty())
EmitAbbrev(MCOS, dwarf::DW_AT_comp_dir, dwarf::DW_FORM_string);
StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
if (!DwarfDebugFlags.empty())
EmitAbbrev(MCOS, dwarf::DW_AT_APPLE_flags, dwarf::DW_FORM_string);
EmitAbbrev(MCOS, dwarf::DW_AT_producer, dwarf::DW_FORM_string);
EmitAbbrev(MCOS, dwarf::DW_AT_language, dwarf::DW_FORM_data2);
EmitAbbrev(MCOS, 0, 0);
// DW_TAG_label DIE abbrev (2).
MCOS->emitULEB128IntValue(2);
MCOS->emitULEB128IntValue(dwarf::DW_TAG_label);
MCOS->emitInt8(dwarf::DW_CHILDREN_yes);
EmitAbbrev(MCOS, dwarf::DW_AT_name, dwarf::DW_FORM_string);
EmitAbbrev(MCOS, dwarf::DW_AT_decl_file, dwarf::DW_FORM_data4);
EmitAbbrev(MCOS, dwarf::DW_AT_decl_line, dwarf::DW_FORM_data4);
EmitAbbrev(MCOS, dwarf::DW_AT_low_pc, dwarf::DW_FORM_addr);
EmitAbbrev(MCOS, dwarf::DW_AT_prototyped, dwarf::DW_FORM_flag);
EmitAbbrev(MCOS, 0, 0);
// DW_TAG_unspecified_parameters DIE abbrev (3).
MCOS->emitULEB128IntValue(3);
MCOS->emitULEB128IntValue(dwarf::DW_TAG_unspecified_parameters);
MCOS->emitInt8(dwarf::DW_CHILDREN_no);
EmitAbbrev(MCOS, 0, 0);
// Terminate the abbreviations for this compilation unit.
MCOS->emitInt8(0);
}
// When generating dwarf for assembly source files this emits the data for
// .debug_aranges section. This section contains a header and a table of pairs
// of PointerSize'ed values for the address and size of section(s) with line
// table entries.
static void EmitGenDwarfAranges(MCStreamer *MCOS,
const MCSymbol *InfoSectionSymbol) {
MCContext &context = MCOS->getContext();
auto &Sections = context.getGenDwarfSectionSyms();
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection());
// This will be the length of the .debug_aranges section, first account for
// the size of each item in the header (see below where we emit these items).
int Length = 4 + 2 + 4 + 1 + 1;
// Figure the padding after the header before the table of address and size
// pairs who's values are PointerSize'ed.
const MCAsmInfo *asmInfo = context.getAsmInfo();
int AddrSize = asmInfo->getCodePointerSize();
int Pad = 2 * AddrSize - (Length & (2 * AddrSize - 1));
if (Pad == 2 * AddrSize)
Pad = 0;
Length += Pad;
// Add the size of the pair of PointerSize'ed values for the address and size
// of each section we have in the table.
Length += 2 * AddrSize * Sections.size();
// And the pair of terminating zeros.
Length += 2 * AddrSize;
// Emit the header for this section.
// The 4 byte length not including the 4 byte value for the length.
MCOS->emitInt32(Length - 4);
// The 2 byte version, which is 2.
MCOS->emitInt16(2);
// The 4 byte offset to the compile unit in the .debug_info from the start
// of the .debug_info.
if (InfoSectionSymbol)
MCOS->emitSymbolValue(InfoSectionSymbol, 4,
asmInfo->needsDwarfSectionOffsetDirective());
else
MCOS->emitInt32(0);
// The 1 byte size of an address.
MCOS->emitInt8(AddrSize);
// The 1 byte size of a segment descriptor, we use a value of zero.
MCOS->emitInt8(0);
// Align the header with the padding if needed, before we put out the table.
for(int i = 0; i < Pad; i++)
MCOS->emitInt8(0);
// Now emit the table of pairs of PointerSize'ed values for the section
// addresses and sizes.
for (MCSection *Sec : Sections) {
const MCSymbol *StartSymbol = Sec->getBeginSymbol();
MCSymbol *EndSymbol = Sec->getEndSymbol(context);
assert(StartSymbol && "StartSymbol must not be NULL");
assert(EndSymbol && "EndSymbol must not be NULL");
const MCExpr *Addr = MCSymbolRefExpr::create(
StartSymbol, MCSymbolRefExpr::VK_None, context);
const MCExpr *Size = MakeStartMinusEndExpr(*MCOS,
*StartSymbol, *EndSymbol, 0);
MCOS->emitValue(Addr, AddrSize);
emitAbsValue(*MCOS, Size, AddrSize);
}
// And finally the pair of terminating zeros.
MCOS->emitIntValue(0, AddrSize);
MCOS->emitIntValue(0, AddrSize);
}
// When generating dwarf for assembly source files this emits the data for
// .debug_info section which contains three parts. The header, the compile_unit
// DIE and a list of label DIEs.
static void EmitGenDwarfInfo(MCStreamer *MCOS,
const MCSymbol *AbbrevSectionSymbol,
const MCSymbol *LineSectionSymbol,
const MCSymbol *RangesSymbol) {
MCContext &context = MCOS->getContext();
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfInfoSection());
// Create a symbol at the start and end of this section used in here for the
// expression to calculate the length in the header.
MCSymbol *InfoStart = context.createTempSymbol();
MCOS->emitLabel(InfoStart);
MCSymbol *InfoEnd = context.createTempSymbol();
// First part: the header.
// The 4 byte total length of the information for this compilation unit, not
// including these 4 bytes.
const MCExpr *Length = MakeStartMinusEndExpr(*MCOS, *InfoStart, *InfoEnd, 4);
emitAbsValue(*MCOS, Length, 4);
// The 2 byte DWARF version.
MCOS->emitInt16(context.getDwarfVersion());
// The DWARF v5 header has unit type, address size, abbrev offset.
// Earlier versions have abbrev offset, address size.
const MCAsmInfo &AsmInfo = *context.getAsmInfo();
int AddrSize = AsmInfo.getCodePointerSize();
if (context.getDwarfVersion() >= 5) {
MCOS->emitInt8(dwarf::DW_UT_compile);
MCOS->emitInt8(AddrSize);
}
// The 4 byte offset to the debug abbrevs from the start of the .debug_abbrev,
// it is at the start of that section so this is zero.
if (AbbrevSectionSymbol == nullptr)
MCOS->emitInt32(0);
else
MCOS->emitSymbolValue(AbbrevSectionSymbol, 4,
AsmInfo.needsDwarfSectionOffsetDirective());
if (context.getDwarfVersion() <= 4)
MCOS->emitInt8(AddrSize);
// Second part: the compile_unit DIE.
// The DW_TAG_compile_unit DIE abbrev (1).
MCOS->emitULEB128IntValue(1);
// DW_AT_stmt_list, a 4 byte offset from the start of the .debug_line section,
// which is at the start of that section so this is zero.
if (LineSectionSymbol)
MCOS->emitSymbolValue(LineSectionSymbol, 4,
AsmInfo.needsDwarfSectionOffsetDirective());
else
MCOS->emitInt32(0);
if (RangesSymbol) {
// There are multiple sections containing code, so we must use
// .debug_ranges/.debug_rnglists. AT_ranges, the 4 byte offset from the
// start of the .debug_ranges/.debug_rnglists.