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llvm/lib/MC/MCDwarf.cpp
Oliver Stannard 98ef3474ef Downgrade DWARF2 section limit error to a warning 
We currently emit an error when trying to assemble a file with more
than one section using DWARF2 debug info. This should be a warning
instead, as the resulting file will still be usable, but with a
degraded debug illusion.



git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@218241 91177308-0d34-0410-b5e6-96231b3b80d8
2014-09-22 10:45:16 +00:00

1585 lines
56 KiB
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//===- lib/MC/MCDwarf.cpp - MCDwarf implementation ------------------------===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCDwarf.h"
#include "llvm/ADT/Hashing.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/Twine.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/MCSymbol.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/raw_ostream.h"
using namespace llvm;
// Given a special op, return the address skip amount (in units of
// DWARF2_LINE_MIN_INSN_LENGTH.
#define SPECIAL_ADDR(op) (((op) - DWARF2_LINE_OPCODE_BASE)/DWARF2_LINE_RANGE)
// The maximum address skip amount that can be encoded with a special op.
#define MAX_SPECIAL_ADDR_DELTA SPECIAL_ADDR(255)
// First special line opcode - leave room for the standard opcodes.
// Note: If you want to change this, you'll have to update the
// "standard_opcode_lengths" table that is emitted in DwarfFileTable::Emit().
#define DWARF2_LINE_OPCODE_BASE 13
// Minimum line offset in a special line info. opcode. This value
// was chosen to give a reasonable range of values.
#define DWARF2_LINE_BASE -5
// Range of line offsets in a special line info. opcode.
#define DWARF2_LINE_RANGE 14
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 MCLineEntry::Make(MCObjectStreamer *MCOS, const 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 MCLineEntry.
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.
MCLineEntry 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 emits the Dwarf line table for the specified section from the entries
// in the LineSection.
//
static inline void
EmitDwarfLineTable(MCObjectStreamer *MCOS, const MCSection *Section,
const MCLineSection::MCLineEntryCollection &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 MCLineEntry and encode the dwarf line number table.
for (auto it = LineEntries.begin(),
ie = LineEntries.end();
it != ie; ++it) {
if (FileNum != it->getFileNum()) {
FileNum = it->getFileNum();
MCOS->EmitIntValue(dwarf::DW_LNS_set_file, 1);
MCOS->EmitULEB128IntValue(FileNum);
}
if (Column != it->getColumn()) {
Column = it->getColumn();
MCOS->EmitIntValue(dwarf::DW_LNS_set_column, 1);
MCOS->EmitULEB128IntValue(Column);
}
if (Discriminator != it->getDiscriminator()) {
Discriminator = it->getDiscriminator();
unsigned Size = getULEB128Size(Discriminator);
MCOS->EmitIntValue(dwarf::DW_LNS_extended_op, 1);
MCOS->EmitULEB128IntValue(Size + 1);
MCOS->EmitIntValue(dwarf::DW_LNE_set_discriminator, 1);
MCOS->EmitULEB128IntValue(Discriminator);
}
if (Isa != it->getIsa()) {
Isa = it->getIsa();
MCOS->EmitIntValue(dwarf::DW_LNS_set_isa, 1);
MCOS->EmitULEB128IntValue(Isa);
}
if ((it->getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
Flags = it->getFlags();
MCOS->EmitIntValue(dwarf::DW_LNS_negate_stmt, 1);
}
if (it->getFlags() & DWARF2_FLAG_BASIC_BLOCK)
MCOS->EmitIntValue(dwarf::DW_LNS_set_basic_block, 1);
if (it->getFlags() & DWARF2_FLAG_PROLOGUE_END)
MCOS->EmitIntValue(dwarf::DW_LNS_set_prologue_end, 1);
if (it->getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
MCOS->EmitIntValue(dwarf::DW_LNS_set_epilogue_begin, 1);
int64_t LineDelta = static_cast<int64_t>(it->getLine()) - LastLine;
MCSymbol *Label = it->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->getPointerSize());
LastLine = it->getLine();
LastLabel = Label;
}
// Emit a DW_LNE_end_sequence for the end of the section.
// Using the pointer Section create a temporary label at the end of the
// section and use that and the LastLabel 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.
// Switch to the section to be able to create a symbol at its end.
// TODO: keep track of the last subsection so that this symbol appears in the
// correct place.
MCOS->SwitchSection(Section);
MCContext &context = MCOS->getContext();
// Create a symbol at the end of the section.
MCSymbol *SectionEnd = context.CreateTempSymbol();
// Set the value of the symbol, as we are at the end of the section.
MCOS->EmitLabel(SectionEnd);
// Switch back the dwarf line section.
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfLineSection());
const MCAsmInfo *asmInfo = MCOS->getContext().getAsmInfo();
MCOS->EmitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, SectionEnd,
asmInfo->getPointerSize());
}
//
// This emits the Dwarf file and the line tables.
//
void MCDwarfLineTable::Emit(MCObjectStreamer *MCOS) {
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;
// 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);
}
void MCDwarfDwoLineTable::Emit(MCStreamer &MCOS) const {
MCOS.EmitLabel(Header.Emit(&MCOS, None).second);
}
std::pair<MCSymbol *, MCSymbol *> MCDwarfLineTableHeader::Emit(MCStreamer *MCOS) 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) == (DWARF2_LINE_OPCODE_BASE - 1));
return Emit(MCOS, StandardOpcodeLengths);
}
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);
}
std::pair<MCSymbol *, MCSymbol *>
MCDwarfLineTableHeader::Emit(MCStreamer *MCOS,
ArrayRef<char> StandardOpcodeLengths) 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, which is Dwarf 2.
MCOS->EmitIntValue(2, 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. Which is the start of the
// section to the end of the prologue. Not including the 4 bytes for the
// total length, the 2 bytes for the version, and these 4 bytes for the
// length of the prologue.
emitAbsValue(
*MCOS,
MakeStartMinusEndExpr(*MCOS, *LineStartSym, *ProEndSym, (4 + 2 + 4)), 4);
// Parameters of the state machine, are next.
MCOS->EmitIntValue(context.getAsmInfo()->getMinInstAlignment(), 1);
MCOS->EmitIntValue(DWARF2_LINE_DEFAULT_IS_STMT, 1);
MCOS->EmitIntValue(DWARF2_LINE_BASE, 1);
MCOS->EmitIntValue(DWARF2_LINE_RANGE, 1);
MCOS->EmitIntValue(StandardOpcodeLengths.size() + 1, 1);
// Standard opcode lengths
for (char Length : StandardOpcodeLengths)
MCOS->EmitIntValue(Length, 1);
// Put out the directory and file tables.
// First the directory table.
for (unsigned i = 0; i < MCDwarfDirs.size(); i++) {
MCOS->EmitBytes(MCDwarfDirs[i]); // the DirectoryName
MCOS->EmitBytes(StringRef("\0", 1)); // the null term. of the string
}
MCOS->EmitIntValue(0, 1); // 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
MCOS->EmitBytes(StringRef("\0", 1)); // the null term. of the string
// the Directory num
MCOS->EmitULEB128IntValue(MCDwarfFiles[i].DirIndex);
MCOS->EmitIntValue(0, 1); // last modification timestamp (always 0)
MCOS->EmitIntValue(0, 1); // filesize (always 0)
}
MCOS->EmitIntValue(0, 1); // Terminate the file list
// 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) const {
MCSymbol *LineEndSym = Header.Emit(MCOS).second;
// Put out the line tables.
for (const auto &LineSec : MCLineSections.getMCLineEntries())
EmitDwarfLineTable(MCOS, LineSec.first, LineSec.second);
if (MCOS->getContext().getAsmInfo()->getLinkerRequiresNonEmptyDwarfLines() &&
MCLineSections.getMCLineEntries().empty()) {
// The darwin9 linker has a bug (see PR8715). For for 32-bit architectures
// it requires:
// total_length >= prologue_length + 10
// We are 4 bytes short, since we have total_length = 51 and
// prologue_length = 45
// The regular end_sequence should be sufficient.
MCDwarfLineAddr::Emit(MCOS, INT64_MAX, 0);
}
// 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);
}
unsigned MCDwarfLineTable::getFile(StringRef &Directory, StringRef &FileName,
unsigned FileNumber) {
return Header.getFile(Directory, FileName, FileNumber);
}
unsigned MCDwarfLineTableHeader::getFile(StringRef &Directory,
StringRef &FileName,
unsigned FileNumber) {
if (Directory == CompilationDir)
Directory = "";
if (FileName.empty()) {
FileName = "<stdin>";
Directory = "";
}
assert(!FileName.empty());
if (FileNumber == 0) {
FileNumber = SourceIdMap.size() + 1;
assert((MCDwarfFiles.empty() || FileNumber == MCDwarfFiles.size()) &&
"Don't mix autonumbered and explicit numbered line table usage");
StringMapEntry<unsigned> &Ent = SourceIdMap.GetOrCreateValue(
(Directory + Twine('\0') + FileName).str(), FileNumber);
if (Ent.getValue() != FileNumber)
return Ent.getValue();
}
// Make space for this FileNumber in the MCDwarfFiles vector if needed.
MCDwarfFiles.resize(FileNumber + 1);
// Get the new MCDwarfFile slot for this FileNumber.
MCDwarfFile &File = MCDwarfFiles[FileNumber];
// It is an error to use see the same number more than once.
if (!File.Name.empty())
return 0;
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 = 0;
for (unsigned End = MCDwarfDirs.size(); DirIndex < End; DirIndex++) {
if (Directory == MCDwarfDirs[DirIndex])
break;
}
if (DirIndex >= MCDwarfDirs.size())
MCDwarfDirs.push_back(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 = FileName;
File.DirIndex = DirIndex;
// return the allocated FileNumber.
return FileNumber;
}
/// Utility function to emit the encoding to a streamer.
void MCDwarfLineAddr::Emit(MCStreamer *MCOS, int64_t LineDelta,
uint64_t AddrDelta) {
MCContext &Context = MCOS->getContext();
SmallString<256> Tmp;
raw_svector_ostream OS(Tmp);
MCDwarfLineAddr::Encode(Context, LineDelta, AddrDelta, OS);
MCOS->EmitBytes(OS.str());
}
/// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
void MCDwarfLineAddr::Encode(MCContext &Context, int64_t LineDelta,
uint64_t AddrDelta, raw_ostream &OS) {
uint64_t Temp, Opcode;
bool NeedCopy = false;
// 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 == MAX_SPECIAL_ADDR_DELTA)
OS << char(dwarf::DW_LNS_const_add_pc);
else {
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 - DWARF2_LINE_BASE;
// If the line increment is out of range of a special opcode, we must encode
// it with DW_LNS_advance_line.
if (Temp >= DWARF2_LINE_RANGE) {
OS << char(dwarf::DW_LNS_advance_line);
encodeSLEB128(LineDelta, OS);
LineDelta = 0;
Temp = 0 - DWARF2_LINE_BASE;
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 += DWARF2_LINE_OPCODE_BASE;
// Avoid overflow when addr_delta is large.
if (AddrDelta < 256 + MAX_SPECIAL_ADDR_DELTA) {
// Try using a special opcode.
Opcode = Temp + AddrDelta * DWARF2_LINE_RANGE;
if (Opcode <= 255) {
OS << char(Opcode);
return;
}
// Try using DW_LNS_const_add_pc followed by special op.
Opcode = Temp + (AddrDelta - MAX_SPECIAL_ADDR_DELTA) * DWARF2_LINE_RANGE;
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
OS << char(Temp);
}
// 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->EmitIntValue(dwarf::DW_CHILDREN_yes, 1);
EmitAbbrev(MCOS, dwarf::DW_AT_stmt_list, dwarf::DW_FORM_data4);
if (MCOS->getContext().getGenDwarfSectionSyms().size() > 1 &&
MCOS->getContext().getDwarfVersion() >= 3) {
EmitAbbrev(MCOS, dwarf::DW_AT_ranges, 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->EmitIntValue(dwarf::DW_CHILDREN_yes, 1);
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->EmitIntValue(dwarf::DW_CHILDREN_no, 1);
EmitAbbrev(MCOS, 0, 0);
// Terminate the abbreviations for this compilation unit.
MCOS->EmitIntValue(0, 1);
}
// 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->getPointerSize();
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->EmitIntValue(Length - 4, 4);
// The 2 byte version, which is 2.
MCOS->EmitIntValue(2, 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->EmitIntValue(0, 4);
// The 1 byte size of an address.
MCOS->EmitIntValue(AddrSize, 1);
// The 1 byte size of a segment descriptor, we use a value of zero.
MCOS->EmitIntValue(0, 1);
// Align the header with the padding if needed, before we put out the table.
for(int i = 0; i < Pad; i++)
MCOS->EmitIntValue(0, 1);
// Now emit the table of pairs of PointerSize'ed values for the section
// addresses and sizes.
for (const auto &sec : Sections) {
MCSymbol *StartSymbol = sec.second.first;
MCSymbol *EndSymbol = sec.second.second;
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 *RangesSectionSymbol) {
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->EmitIntValue(context.getDwarfVersion(), 2);
const MCAsmInfo &AsmInfo = *context.getAsmInfo();
// 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->EmitIntValue(0, 4);
else
MCOS->EmitSymbolValue(AbbrevSectionSymbol, 4,
AsmInfo.needsDwarfSectionOffsetDirective());
const MCAsmInfo *asmInfo = context.getAsmInfo();
int AddrSize = asmInfo->getPointerSize();
// The 1 byte size of an address.
MCOS->EmitIntValue(AddrSize, 1);
// 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->EmitIntValue(0, 4);
if (RangesSectionSymbol) {
// There are multiple sections containing code, so we must use the
// .debug_ranges sections.
// AT_ranges, the 4 byte offset from the start of the .debug_ranges section
// to the address range list for this compilation unit.
MCOS->EmitSymbolValue(RangesSectionSymbol, 4);
} else {
// If we only have one non-empty code section, we can use the simpler
// AT_low_pc and AT_high_pc attributes.
// Find the first (and only) non-empty text section
auto &Sections = context.getGenDwarfSectionSyms();
const auto TextSection = Sections.begin();
assert(TextSection != Sections.end() && "No text section found");
MCSymbol *StartSymbol = TextSection->second.first;
MCSymbol *EndSymbol = TextSection->second.second;
assert(StartSymbol && "StartSymbol must not be NULL");
assert(EndSymbol && "EndSymbol must not be NULL");
// AT_low_pc, the first address of the default .text section.
const MCExpr *Start = MCSymbolRefExpr::Create(
StartSymbol, MCSymbolRefExpr::VK_None, context);
MCOS->EmitValue(Start, AddrSize);
// AT_high_pc, the last address of the default .text section.
const MCExpr *End = MCSymbolRefExpr::Create(
EndSymbol, MCSymbolRefExpr::VK_None, context);
MCOS->EmitValue(End, AddrSize);
}
// AT_name, the name of the source file. Reconstruct from the first directory
// and file table entries.
const SmallVectorImpl<std::string> &MCDwarfDirs = context.getMCDwarfDirs();
if (MCDwarfDirs.size() > 0) {
MCOS->EmitBytes(MCDwarfDirs[0]);
MCOS->EmitBytes(sys::path::get_separator());
}
const SmallVectorImpl<MCDwarfFile> &MCDwarfFiles =
MCOS->getContext().getMCDwarfFiles();
MCOS->EmitBytes(MCDwarfFiles[1].Name);
MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
// AT_comp_dir, the working directory the assembly was done in.
if (!context.getCompilationDir().empty()) {
MCOS->EmitBytes(context.getCompilationDir());
MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
}
// AT_APPLE_flags, the command line arguments of the assembler tool.
StringRef DwarfDebugFlags = context.getDwarfDebugFlags();
if (!DwarfDebugFlags.empty()){
MCOS->EmitBytes(DwarfDebugFlags);
MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
}
// AT_producer, the version of the assembler tool.
StringRef DwarfDebugProducer = context.getDwarfDebugProducer();
if (!DwarfDebugProducer.empty())
MCOS->EmitBytes(DwarfDebugProducer);
else
MCOS->EmitBytes(StringRef("llvm-mc (based on LLVM " PACKAGE_VERSION ")"));
MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
// AT_language, a 4 byte value. We use DW_LANG_Mips_Assembler as the dwarf2
// draft has no standard code for assembler.
MCOS->EmitIntValue(dwarf::DW_LANG_Mips_Assembler, 2);
// Third part: the list of label DIEs.
// Loop on saved info for dwarf labels and create the DIEs for them.
const std::vector<MCGenDwarfLabelEntry> &Entries =
MCOS->getContext().getMCGenDwarfLabelEntries();
for (const auto &Entry : Entries) {
// The DW_TAG_label DIE abbrev (2).
MCOS->EmitULEB128IntValue(2);
// AT_name, of the label without any leading underbar.
MCOS->EmitBytes(Entry.getName());
MCOS->EmitIntValue(0, 1); // NULL byte to terminate the string.
// AT_decl_file, index into the file table.
MCOS->EmitIntValue(Entry.getFileNumber(), 4);
// AT_decl_line, source line number.
MCOS->EmitIntValue(Entry.getLineNumber(), 4);
// AT_low_pc, start address of the label.
const MCExpr *AT_low_pc = MCSymbolRefExpr::Create(Entry.getLabel(),
MCSymbolRefExpr::VK_None, context);
MCOS->EmitValue(AT_low_pc, AddrSize);
// DW_AT_prototyped, a one byte flag value of 0 saying we have no prototype.
MCOS->EmitIntValue(0, 1);
// The DW_TAG_unspecified_parameters DIE abbrev (3).
MCOS->EmitULEB128IntValue(3);
// Add the NULL DIE terminating the DW_TAG_unspecified_parameters DIE's.
MCOS->EmitIntValue(0, 1);
}
// Add the NULL DIE terminating the Compile Unit DIE's.
MCOS->EmitIntValue(0, 1);
// Now set the value of the symbol at the end of the info section.
MCOS->EmitLabel(InfoEnd);
}
// When generating dwarf for assembly source files this emits the data for
// .debug_ranges section. We only emit one range list, which spans all of the
// executable sections of this file.
static void EmitGenDwarfRanges(MCStreamer *MCOS) {
MCContext &context = MCOS->getContext();
auto &Sections = context.getGenDwarfSectionSyms();
const MCAsmInfo *AsmInfo = context.getAsmInfo();
int AddrSize = AsmInfo->getPointerSize();
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfRangesSection());
for (const auto sec : Sections) {
MCSymbol *StartSymbol = sec.second.first;
MCSymbol *EndSymbol = sec.second.second;
assert(StartSymbol && "StartSymbol must not be NULL");
assert(EndSymbol && "EndSymbol must not be NULL");
// Emit a base address selection entry for the start of this section
const MCExpr *SectionStartAddr = MCSymbolRefExpr::Create(
StartSymbol, MCSymbolRefExpr::VK_None, context);
MCOS->EmitFill(AddrSize, 0xFF);
MCOS->EmitValue(SectionStartAddr, AddrSize);
// Emit a range list entry spanning this section
const MCExpr *SectionSize = MakeStartMinusEndExpr(*MCOS,
*StartSymbol, *EndSymbol, 0);
MCOS->EmitIntValue(0, AddrSize);
emitAbsValue(*MCOS, SectionSize, AddrSize);
}
// Emit end of list entry
MCOS->EmitIntValue(0, AddrSize);
MCOS->EmitIntValue(0, AddrSize);
}
//
// When generating dwarf for assembly source files this emits the Dwarf
// sections.
//
void MCGenDwarfInfo::Emit(MCStreamer *MCOS) {
MCContext &context = MCOS->getContext();
// Create the dwarf sections in this order (.debug_line already created).
const MCAsmInfo *AsmInfo = context.getAsmInfo();
bool CreateDwarfSectionSymbols =
AsmInfo->doesDwarfUseRelocationsAcrossSections();
MCSymbol *LineSectionSymbol = nullptr;
if (CreateDwarfSectionSymbols)
LineSectionSymbol = MCOS->getDwarfLineTableSymbol(0);
MCSymbol *AbbrevSectionSymbol = nullptr;
MCSymbol *InfoSectionSymbol = nullptr;
MCSymbol *RangesSectionSymbol = NULL;
// Create end symbols for each section, and remove empty sections
MCOS->getContext().finalizeDwarfSections(*MCOS);
// If there are no sections to generate debug info for, we don't need
// to do anything
if (MCOS->getContext().getGenDwarfSectionSyms().empty())
return;
// We only use the .debug_ranges section if we have multiple code sections,
// and we are emitting a DWARF version which supports it.
const bool UseRangesSection =
MCOS->getContext().getGenDwarfSectionSyms().size() > 1 &&
MCOS->getContext().getDwarfVersion() >= 3;
CreateDwarfSectionSymbols |= UseRangesSection;
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfInfoSection());
if (CreateDwarfSectionSymbols) {
InfoSectionSymbol = context.CreateTempSymbol();
MCOS->EmitLabel(InfoSectionSymbol);
}
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfAbbrevSection());
if (CreateDwarfSectionSymbols) {
AbbrevSectionSymbol = context.CreateTempSymbol();
MCOS->EmitLabel(AbbrevSectionSymbol);
}
if (UseRangesSection) {
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfRangesSection());
if (CreateDwarfSectionSymbols) {
RangesSectionSymbol = context.CreateTempSymbol();
MCOS->EmitLabel(RangesSectionSymbol);
}
}
assert((RangesSectionSymbol != NULL) || !UseRangesSection);
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection());
// Output the data for .debug_aranges section.
EmitGenDwarfAranges(MCOS, InfoSectionSymbol);
if (UseRangesSection)
EmitGenDwarfRanges(MCOS);
// Output the data for .debug_abbrev section.
EmitGenDwarfAbbrev(MCOS);
// Output the data for .debug_info section.
EmitGenDwarfInfo(MCOS, AbbrevSectionSymbol, LineSectionSymbol,
RangesSectionSymbol);
}
//
// When generating dwarf for assembly source files this is called when symbol
// for a label is created. If this symbol is not a temporary and is in the
// section that dwarf is being generated for, save the needed info to create
// a dwarf label.
//
void MCGenDwarfLabelEntry::Make(MCSymbol *Symbol, MCStreamer *MCOS,
SourceMgr &SrcMgr, SMLoc &Loc) {
// We won't create dwarf labels for temporary symbols.
if (Symbol->isTemporary())
return;
MCContext &context = MCOS->getContext();
// We won't create dwarf labels for symbols in sections that we are not
// generating debug info for.
if (!context.getGenDwarfSectionSyms().count(MCOS->getCurrentSection().first))
return;
// The dwarf label's name does not have the symbol name's leading
// underbar if any.
StringRef Name = Symbol->getName();
if (Name.startswith("_"))
Name = Name.substr(1, Name.size()-1);
// Get the dwarf file number to be used for the dwarf label.
unsigned FileNumber = context.getGenDwarfFileNumber();
// Finding the line number is the expensive part which is why we just don't
// pass it in as for some symbols we won't create a dwarf label.
unsigned CurBuffer = SrcMgr.FindBufferContainingLoc(Loc);
unsigned LineNumber = SrcMgr.FindLineNumber(Loc, CurBuffer);
// We create a temporary symbol for use for the AT_high_pc and AT_low_pc
// values so that they don't have things like an ARM thumb bit from the
// original symbol. So when used they won't get a low bit set after
// relocation.
MCSymbol *Label = context.CreateTempSymbol();
MCOS->EmitLabel(Label);
// Create and entry for the info and add it to the other entries.
MCOS->getContext().addMCGenDwarfLabelEntry(
MCGenDwarfLabelEntry(Name, FileNumber, LineNumber, Label));
}
static int getDataAlignmentFactor(MCStreamer &streamer) {
MCContext &context = streamer.getContext();
const MCAsmInfo *asmInfo = context.getAsmInfo();
int size = asmInfo->getCalleeSaveStackSlotSize();
if (asmInfo->isStackGrowthDirectionUp())
return size;
else
return -size;
}
static unsigned getSizeForEncoding(MCStreamer &streamer,
unsigned symbolEncoding) {
MCContext &context = streamer.getContext();
unsigned format = symbolEncoding & 0x0f;
switch (format) {
default: llvm_unreachable("Unknown Encoding");
case dwarf::DW_EH_PE_absptr:
case dwarf::DW_EH_PE_signed:
return context.getAsmInfo()->getPointerSize();
case dwarf::DW_EH_PE_udata2:
case dwarf::DW_EH_PE_sdata2:
return 2;
case dwarf::DW_EH_PE_udata4:
case dwarf::DW_EH_PE_sdata4:
return 4;
case dwarf::DW_EH_PE_udata8:
case dwarf::DW_EH_PE_sdata8:
return 8;
}
}
static void emitFDESymbol(MCObjectStreamer &streamer, const MCSymbol &symbol,
unsigned symbolEncoding, bool isEH) {
MCContext &context = streamer.getContext();
const MCAsmInfo *asmInfo = context.getAsmInfo();
const MCExpr *v = asmInfo->getExprForFDESymbol(&symbol,
symbolEncoding,
streamer);
unsigned size = getSizeForEncoding(streamer, symbolEncoding);
if (asmInfo->doDwarfFDESymbolsUseAbsDiff() && isEH)
emitAbsValue(streamer, v, size);
else
streamer.EmitValue(v, size);
}
static void EmitPersonality(MCStreamer &streamer, const MCSymbol &symbol,
unsigned symbolEncoding) {
MCContext &context = streamer.getContext();
const MCAsmInfo *asmInfo = context.getAsmInfo();
const MCExpr *v = asmInfo->getExprForPersonalitySymbol(&symbol,
symbolEncoding,
streamer);
unsigned size = getSizeForEncoding(streamer, symbolEncoding);
streamer.EmitValue(v, size);
}
namespace {
class FrameEmitterImpl {
int CFAOffset;
bool IsEH;
const MCSymbol *SectionStart;
public:
FrameEmitterImpl(bool isEH)
: CFAOffset(0), IsEH(isEH), SectionStart(nullptr) {}
void setSectionStart(const MCSymbol *Label) { SectionStart = Label; }
/// Emit the unwind information in a compact way.
void EmitCompactUnwind(MCObjectStreamer &streamer,
const MCDwarfFrameInfo &frame);
const MCSymbol &EmitCIE(MCObjectStreamer &streamer,
const MCSymbol *personality,
unsigned personalityEncoding,
const MCSymbol *lsda,
bool IsSignalFrame,
unsigned lsdaEncoding,
bool IsSimple);
MCSymbol *EmitFDE(MCObjectStreamer &streamer,
const MCSymbol &cieStart,
const MCDwarfFrameInfo &frame);
void EmitCFIInstructions(MCObjectStreamer &streamer,
ArrayRef<MCCFIInstruction> Instrs,
MCSymbol *BaseLabel);
void EmitCFIInstruction(MCObjectStreamer &Streamer,
const MCCFIInstruction &Instr);
};
} // end anonymous namespace
static void emitEncodingByte(MCObjectStreamer &Streamer, unsigned Encoding) {
Streamer.EmitIntValue(Encoding, 1);
}
void FrameEmitterImpl::EmitCFIInstruction(MCObjectStreamer &Streamer,
const MCCFIInstruction &Instr) {
int dataAlignmentFactor = getDataAlignmentFactor(Streamer);
switch (Instr.getOperation()) {
case MCCFIInstruction::OpRegister: {
unsigned Reg1 = Instr.getRegister();
unsigned Reg2 = Instr.getRegister2();
Streamer.EmitIntValue(dwarf::DW_CFA_register, 1);
Streamer.EmitULEB128IntValue(Reg1);
Streamer.EmitULEB128IntValue(Reg2);
return;
}
case MCCFIInstruction::OpWindowSave: {
Streamer.EmitIntValue(dwarf::DW_CFA_GNU_window_save, 1);
return;
}
case MCCFIInstruction::OpUndefined: {
unsigned Reg = Instr.getRegister();
Streamer.EmitIntValue(dwarf::DW_CFA_undefined, 1);
Streamer.EmitULEB128IntValue(Reg);
return;
}
case MCCFIInstruction::OpAdjustCfaOffset:
case MCCFIInstruction::OpDefCfaOffset: {
const bool IsRelative =
Instr.getOperation() == MCCFIInstruction::OpAdjustCfaOffset;
Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_offset, 1);
if (IsRelative)
CFAOffset += Instr.getOffset();
else
CFAOffset = -Instr.getOffset();
Streamer.EmitULEB128IntValue(CFAOffset);
return;
}
case MCCFIInstruction::OpDefCfa: {
Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa, 1);
Streamer.EmitULEB128IntValue(Instr.getRegister());
CFAOffset = -Instr.getOffset();
Streamer.EmitULEB128IntValue(CFAOffset);
return;
}
case MCCFIInstruction::OpDefCfaRegister: {
Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_register, 1);
Streamer.EmitULEB128IntValue(Instr.getRegister());
return;
}
case MCCFIInstruction::OpOffset:
case MCCFIInstruction::OpRelOffset: {
const bool IsRelative =
Instr.getOperation() == MCCFIInstruction::OpRelOffset;
unsigned Reg = Instr.getRegister();
int Offset = Instr.getOffset();
if (IsRelative)
Offset -= CFAOffset;
Offset = Offset / dataAlignmentFactor;
if (Offset < 0) {
Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended_sf, 1);
Streamer.EmitULEB128IntValue(Reg);
Streamer.EmitSLEB128IntValue(Offset);
} else if (Reg < 64) {
Streamer.EmitIntValue(dwarf::DW_CFA_offset + Reg, 1);
Streamer.EmitULEB128IntValue(Offset);
} else {
Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended, 1);
Streamer.EmitULEB128IntValue(Reg);
Streamer.EmitULEB128IntValue(Offset);
}
return;
}
case MCCFIInstruction::OpRememberState:
Streamer.EmitIntValue(dwarf::DW_CFA_remember_state, 1);
return;
case MCCFIInstruction::OpRestoreState:
Streamer.EmitIntValue(dwarf::DW_CFA_restore_state, 1);
return;
case MCCFIInstruction::OpSameValue: {
unsigned Reg = Instr.getRegister();
Streamer.EmitIntValue(dwarf::DW_CFA_same_value, 1);
Streamer.EmitULEB128IntValue(Reg);
return;
}
case MCCFIInstruction::OpRestore: {
unsigned Reg = Instr.getRegister();
Streamer.EmitIntValue(dwarf::DW_CFA_restore | Reg, 1);
return;
}
case MCCFIInstruction::OpEscape:
Streamer.EmitBytes(Instr.getValues());
return;
}
llvm_unreachable("Unhandled case in switch");
}
/// Emit frame instructions to describe the layout of the frame.
void FrameEmitterImpl::EmitCFIInstructions(MCObjectStreamer &streamer,
ArrayRef<MCCFIInstruction> Instrs,
MCSymbol *BaseLabel) {
for (unsigned i = 0, N = Instrs.size(); i < N; ++i) {
const MCCFIInstruction &Instr = Instrs[i];
MCSymbol *Label = Instr.getLabel();
// Throw out move if the label is invalid.
if (Label && !Label->isDefined()) continue; // Not emitted, in dead code.
// Advance row if new location.
if (BaseLabel && Label) {
MCSymbol *ThisSym = Label;
if (ThisSym != BaseLabel) {
streamer.EmitDwarfAdvanceFrameAddr(BaseLabel, ThisSym);
BaseLabel = ThisSym;
}
}
EmitCFIInstruction(streamer, Instr);
}
}
/// Emit the unwind information in a compact way.
void FrameEmitterImpl::EmitCompactUnwind(MCObjectStreamer &Streamer,
const MCDwarfFrameInfo &Frame) {
MCContext &Context = Streamer.getContext();
const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
// range-start range-length compact-unwind-enc personality-func lsda
// _foo LfooEnd-_foo 0x00000023 0 0
// _bar LbarEnd-_bar 0x00000025 __gxx_personality except_tab1
//
// .section __LD,__compact_unwind,regular,debug
//
// # compact unwind for _foo
// .quad _foo
// .set L1,LfooEnd-_foo
// .long L1
// .long 0x01010001
// .quad 0
// .quad 0
//
// # compact unwind for _bar
// .quad _bar
// .set L2,LbarEnd-_bar
// .long L2
// .long 0x01020011
// .quad __gxx_personality
// .quad except_tab1
uint32_t Encoding = Frame.CompactUnwindEncoding;
if (!Encoding) return;
bool DwarfEHFrameOnly = (Encoding == MOFI->getCompactUnwindDwarfEHFrameOnly());
// The encoding needs to know we have an LSDA.
if (!DwarfEHFrameOnly && Frame.Lsda)
Encoding |= 0x40000000;
// Range Start
unsigned FDEEncoding = MOFI->getFDEEncoding();
unsigned Size = getSizeForEncoding(Streamer, FDEEncoding);
Streamer.EmitSymbolValue(Frame.Begin, Size);
// Range Length
const MCExpr *Range = MakeStartMinusEndExpr(Streamer, *Frame.Begin,
*Frame.End, 0);
emitAbsValue(Streamer, Range, 4);
// Compact Encoding
Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_udata4);
Streamer.EmitIntValue(Encoding, Size);
// Personality Function
Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_absptr);
if (!DwarfEHFrameOnly && Frame.Personality)
Streamer.EmitSymbolValue(Frame.Personality, Size);
else
Streamer.EmitIntValue(0, Size); // No personality fn
// LSDA
Size = getSizeForEncoding(Streamer, Frame.LsdaEncoding);
if (!DwarfEHFrameOnly && Frame.Lsda)
Streamer.EmitSymbolValue(Frame.Lsda, Size);
else
Streamer.EmitIntValue(0, Size); // No LSDA
}
const MCSymbol &FrameEmitterImpl::EmitCIE(MCObjectStreamer &streamer,
const MCSymbol *personality,
unsigned personalityEncoding,
const MCSymbol *lsda,
bool IsSignalFrame,
unsigned lsdaEncoding,
bool IsSimple) {
MCContext &context = streamer.getContext();
const MCRegisterInfo *MRI = context.getRegisterInfo();
const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
MCSymbol *sectionStart = context.CreateTempSymbol();
streamer.EmitLabel(sectionStart);
MCSymbol *sectionEnd = context.CreateTempSymbol();
// Length
const MCExpr *Length = MakeStartMinusEndExpr(streamer, *sectionStart,
*sectionEnd, 4);
emitAbsValue(streamer, Length, 4);
// CIE ID
unsigned CIE_ID = IsEH ? 0 : -1;
streamer.EmitIntValue(CIE_ID, 4);
// Version
// For DWARF2, we use CIE version 1
// For DWARF3+, we use CIE version 3
uint8_t CIEVersion = context.getDwarfVersion() <= 2 ? 1 : 3;
streamer.EmitIntValue(CIEVersion, 1);
// Augmentation String
SmallString<8> Augmentation;
if (IsEH) {
Augmentation += "z";
if (personality)
Augmentation += "P";
if (lsda)
Augmentation += "L";
Augmentation += "R";
if (IsSignalFrame)
Augmentation += "S";
streamer.EmitBytes(Augmentation.str());
}
streamer.EmitIntValue(0, 1);
// Code Alignment Factor
streamer.EmitULEB128IntValue(context.getAsmInfo()->getMinInstAlignment());
// Data Alignment Factor
streamer.EmitSLEB128IntValue(getDataAlignmentFactor(streamer));
// Return Address Register
if (CIEVersion == 1) {
assert(MRI->getRARegister() <= 255 &&
"DWARF 2 encodes return_address_register in one byte");
streamer.EmitIntValue(MRI->getDwarfRegNum(MRI->getRARegister(), true), 1);
} else {
streamer.EmitULEB128IntValue(
MRI->getDwarfRegNum(MRI->getRARegister(), true));
}
// Augmentation Data Length (optional)
unsigned augmentationLength = 0;
if (IsEH) {
if (personality) {
// Personality Encoding
augmentationLength += 1;
// Personality
augmentationLength += getSizeForEncoding(streamer, personalityEncoding);
}
if (lsda)
augmentationLength += 1;
// Encoding of the FDE pointers
augmentationLength += 1;
streamer.EmitULEB128IntValue(augmentationLength);
// Augmentation Data (optional)
if (personality) {
// Personality Encoding
emitEncodingByte(streamer, personalityEncoding);
// Personality
EmitPersonality(streamer, *personality, personalityEncoding);
}
if (lsda)
emitEncodingByte(streamer, lsdaEncoding);
// Encoding of the FDE pointers
emitEncodingByte(streamer, MOFI->getFDEEncoding());
}
// Initial Instructions
const MCAsmInfo *MAI = context.getAsmInfo();
if (!IsSimple) {
const std::vector<MCCFIInstruction> &Instructions =
MAI->getInitialFrameState();
EmitCFIInstructions(streamer, Instructions, nullptr);
}
// Padding
streamer.EmitValueToAlignment(IsEH ? 4 : MAI->getPointerSize());
streamer.EmitLabel(sectionEnd);
return *sectionStart;
}
MCSymbol *FrameEmitterImpl::EmitFDE(MCObjectStreamer &streamer,
const MCSymbol &cieStart,
const MCDwarfFrameInfo &frame) {
MCContext &context = streamer.getContext();
MCSymbol *fdeStart = context.CreateTempSymbol();
MCSymbol *fdeEnd = context.CreateTempSymbol();
const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
// Length
const MCExpr *Length = MakeStartMinusEndExpr(streamer, *fdeStart, *fdeEnd, 0);
emitAbsValue(streamer, Length, 4);
streamer.EmitLabel(fdeStart);
// CIE Pointer
const MCAsmInfo *asmInfo = context.getAsmInfo();
if (IsEH) {
const MCExpr *offset = MakeStartMinusEndExpr(streamer, cieStart, *fdeStart,
0);
emitAbsValue(streamer, offset, 4);
} else if (!asmInfo->doesDwarfUseRelocationsAcrossSections()) {
const MCExpr *offset = MakeStartMinusEndExpr(streamer, *SectionStart,
cieStart, 0);
emitAbsValue(streamer, offset, 4);
} else {
streamer.EmitSymbolValue(&cieStart, 4);
}
// PC Begin
unsigned PCEncoding =
IsEH ? MOFI->getFDEEncoding() : (unsigned)dwarf::DW_EH_PE_absptr;
unsigned PCSize = getSizeForEncoding(streamer, PCEncoding);
emitFDESymbol(streamer, *frame.Begin, PCEncoding, IsEH);
// PC Range
const MCExpr *Range = MakeStartMinusEndExpr(streamer, *frame.Begin,
*frame.End, 0);
emitAbsValue(streamer, Range, PCSize);
if (IsEH) {
// Augmentation Data Length
unsigned augmentationLength = 0;
if (frame.Lsda)
augmentationLength += getSizeForEncoding(streamer, frame.LsdaEncoding);
streamer.EmitULEB128IntValue(augmentationLength);
// Augmentation Data
if (frame.Lsda)
emitFDESymbol(streamer, *frame.Lsda, frame.LsdaEncoding, true);
}
// Call Frame Instructions
EmitCFIInstructions(streamer, frame.Instructions, frame.Begin);
// Padding
streamer.EmitValueToAlignment(PCSize);
return fdeEnd;
}
namespace {
struct CIEKey {
static const CIEKey getEmptyKey() {
return CIEKey(nullptr, 0, -1, false, false);
}
static const CIEKey getTombstoneKey() {
return CIEKey(nullptr, -1, 0, false, false);
}
CIEKey(const MCSymbol *Personality_, unsigned PersonalityEncoding_,
unsigned LsdaEncoding_, bool IsSignalFrame_, bool IsSimple_)
: Personality(Personality_), PersonalityEncoding(PersonalityEncoding_),
LsdaEncoding(LsdaEncoding_), IsSignalFrame(IsSignalFrame_),
IsSimple(IsSimple_) {}
const MCSymbol *Personality;
unsigned PersonalityEncoding;
unsigned LsdaEncoding;
bool IsSignalFrame;
bool IsSimple;
};
}
namespace llvm {
template <>
struct DenseMapInfo<CIEKey> {
static CIEKey getEmptyKey() {
return CIEKey::getEmptyKey();
}
static CIEKey getTombstoneKey() {
return CIEKey::getTombstoneKey();
}
static unsigned getHashValue(const CIEKey &Key) {
return static_cast<unsigned>(hash_combine(Key.Personality,
Key.PersonalityEncoding,
Key.LsdaEncoding,
Key.IsSignalFrame,
Key.IsSimple));
}
static bool isEqual(const CIEKey &LHS,
const CIEKey &RHS) {
return LHS.Personality == RHS.Personality &&
LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
LHS.LsdaEncoding == RHS.LsdaEncoding &&
LHS.IsSignalFrame == RHS.IsSignalFrame &&
LHS.IsSimple == RHS.IsSimple;
}
};
}
void MCDwarfFrameEmitter::Emit(MCObjectStreamer &Streamer, MCAsmBackend *MAB,
bool IsEH) {
Streamer.generateCompactUnwindEncodings(MAB);
MCContext &Context = Streamer.getContext();
const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
FrameEmitterImpl Emitter(IsEH);
ArrayRef<MCDwarfFrameInfo> FrameArray = Streamer.getDwarfFrameInfos();
// Emit the compact unwind info if available.
bool NeedsEHFrameSection = !MOFI->getSupportsCompactUnwindWithoutEHFrame();
if (IsEH && MOFI->getCompactUnwindSection()) {
bool SectionEmitted = false;
for (unsigned i = 0, n = FrameArray.size(); i < n; ++i) {
const MCDwarfFrameInfo &Frame = FrameArray[i];
if (Frame.CompactUnwindEncoding == 0) continue;
if (!SectionEmitted) {
Streamer.SwitchSection(MOFI->getCompactUnwindSection());
Streamer.EmitValueToAlignment(Context.getAsmInfo()->getPointerSize());
SectionEmitted = true;
}
NeedsEHFrameSection |=
Frame.CompactUnwindEncoding ==
MOFI->getCompactUnwindDwarfEHFrameOnly();
Emitter.EmitCompactUnwind(Streamer, Frame);
}
}
if (!NeedsEHFrameSection) return;
const MCSection &Section =
IsEH ? *const_cast<MCObjectFileInfo*>(MOFI)->getEHFrameSection() :
*MOFI->getDwarfFrameSection();
Streamer.SwitchSection(&Section);
MCSymbol *SectionStart = Context.CreateTempSymbol();
Streamer.EmitLabel(SectionStart);
Emitter.setSectionStart(SectionStart);
MCSymbol *FDEEnd = nullptr;
DenseMap<CIEKey, const MCSymbol *> CIEStarts;
const MCSymbol *DummyDebugKey = nullptr;
NeedsEHFrameSection = !MOFI->getSupportsCompactUnwindWithoutEHFrame();
for (unsigned i = 0, n = FrameArray.size(); i < n; ++i) {
const MCDwarfFrameInfo &Frame = FrameArray[i];
// Emit the label from the previous iteration
if (FDEEnd) {
Streamer.EmitLabel(FDEEnd);
FDEEnd = nullptr;
}
if (!NeedsEHFrameSection && Frame.CompactUnwindEncoding !=
MOFI->getCompactUnwindDwarfEHFrameOnly())
// Don't generate an EH frame if we don't need one. I.e., it's taken care
// of by the compact unwind encoding.
continue;
CIEKey Key(Frame.Personality, Frame.PersonalityEncoding,
Frame.LsdaEncoding, Frame.IsSignalFrame, Frame.IsSimple);
const MCSymbol *&CIEStart = IsEH ? CIEStarts[Key] : DummyDebugKey;
if (!CIEStart)
CIEStart = &Emitter.EmitCIE(Streamer, Frame.Personality,
Frame.PersonalityEncoding, Frame.Lsda,
Frame.IsSignalFrame,
Frame.LsdaEncoding,
Frame.IsSimple);
FDEEnd = Emitter.EmitFDE(Streamer, *CIEStart, Frame);
}
Streamer.EmitValueToAlignment(Context.getAsmInfo()->getPointerSize());
if (FDEEnd)
Streamer.EmitLabel(FDEEnd);
}
void MCDwarfFrameEmitter::EmitAdvanceLoc(MCObjectStreamer &Streamer,
uint64_t AddrDelta) {
MCContext &Context = Streamer.getContext();
SmallString<256> Tmp;
raw_svector_ostream OS(Tmp);
MCDwarfFrameEmitter::EncodeAdvanceLoc(Context, AddrDelta, OS);
Streamer.EmitBytes(OS.str());
}
void MCDwarfFrameEmitter::EncodeAdvanceLoc(MCContext &Context,
uint64_t AddrDelta,
raw_ostream &OS) {
// Scale the address delta by the minimum instruction length.
AddrDelta = ScaleAddrDelta(Context, AddrDelta);
if (AddrDelta == 0) {
} else if (isUIntN(6, AddrDelta)) {
uint8_t Opcode = dwarf::DW_CFA_advance_loc | AddrDelta;
OS << Opcode;
} else if (isUInt<8>(AddrDelta)) {
OS << uint8_t(dwarf::DW_CFA_advance_loc1);
OS << uint8_t(AddrDelta);
} else if (isUInt<16>(AddrDelta)) {
// FIXME: check what is the correct behavior on a big endian machine.
OS << uint8_t(dwarf::DW_CFA_advance_loc2);
OS << uint8_t( AddrDelta & 0xff);
OS << uint8_t((AddrDelta >> 8) & 0xff);
} else {
// FIXME: check what is the correct behavior on a big endian machine.
assert(isUInt<32>(AddrDelta));
OS << uint8_t(dwarf::DW_CFA_advance_loc4);
OS << uint8_t( AddrDelta & 0xff);
OS << uint8_t((AddrDelta >> 8) & 0xff);
OS << uint8_t((AddrDelta >> 16) & 0xff);
OS << uint8_t((AddrDelta >> 24) & 0xff);
}
}
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