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llvm-6502/lib/MC/MCDwarf.cpp
Andrew Trick e15c1079cb Fix a crash that occurs when PWD is invalid. 
MCJIT needs to be able to run in hostile environments, even when PWD
is invalid. There's no need to crash MCJIT in this case.

The obvious fix is to simply leave MCContext's CompilationDir empty
when PWD can't be determined. This way, MCJIT clients,
and other clients that link with LLVM don’t need a valid working directory.

If we do want to guarantee valid CompilationDir, that should be done
only for clients of getCompilationDir(). This is as simple as checking
for an empty string.

The only current use of getCompilationDir is EmitGenDwarfInfo, which
won’t conceivably run with an invalid working dir. However, in the
purely hypothetically and untestable case that this happens, the
AT_comp_dir will be omitted from the compilation_unit DIE.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@196874 91177308-0d34-0410-b5e6-96231b3b80d8
2013-12-10 04:39:09 +00:00

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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/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/MCRegisterInfo.h"
#include "llvm/MC/MCStreamer.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(MCStreamer *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();
// Get the MCLineSection for this section, if one does not exist for this
// section create it.
const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
MCOS->getContext().getMCLineSections();
MCLineSection *LineSection = MCLineSections.lookup(Section);
if (!LineSection) {
// Create a new MCLineSection. This will be deleted after the dwarf line
// table is created using it by iterating through the MCLineSections
// DenseMap.
LineSection = new MCLineSection;
// Save a pointer to the new LineSection into the MCLineSections DenseMap.
MCOS->getContext().addMCLineSection(Section, LineSection);
}
// Add the line entry to this section's entries.
LineSection->addLineEntry(LineEntry,
MCOS->getContext().getDwarfCompileUnitID());
}
//
// 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(MCStreamer *MCOS,
const MCSection *Section,
const MCLineSection *LineSection,
unsigned CUID) {
// This LineSection does not contain any LineEntry for the given Compile Unit.
if (!LineSection->containEntriesForID(CUID))
return;
unsigned FileNum = 1;
unsigned LastLine = 1;
unsigned Column = 0;
unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
unsigned Isa = 0;
MCSymbol *LastLabel = NULL;
// Loop through each MCLineEntry and encode the dwarf line number table.
for (MCLineSection::const_iterator
it = LineSection->getMCLineEntries(CUID).begin(),
ie = LineSection->getMCLineEntries(CUID).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 (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.
//
const MCSymbol *MCDwarfFileTable::Emit(MCStreamer *MCOS) {
MCContext &context = MCOS->getContext();
// Switch to the section where the table will be emitted into.
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfLineSection());
const DenseMap<unsigned, MCSymbol *> &MCLineTableSymbols =
MCOS->getContext().getMCLineTableSymbols();
// CUID and MCLineTableSymbols are set in DwarfDebug, when DwarfDebug does
// not exist, CUID will be 0 and MCLineTableSymbols will be empty.
// Handle Compile Unit 0, the line table start symbol is the section symbol.
const MCSymbol *LineStartSym = EmitCU(MCOS, 0);
// Handle the rest of the Compile Units.
for (unsigned Is = 1, Ie = MCLineTableSymbols.size(); Is < Ie; Is++)
EmitCU(MCOS, Is);
// Now delete the MCLineSections that were created in MCLineEntry::Make()
// and used to emit the line table.
const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
MCOS->getContext().getMCLineSections();
for (DenseMap<const MCSection *, MCLineSection *>::const_iterator it =
MCLineSections.begin(), ie = MCLineSections.end(); it != ie;
++it)
delete it->second;
return LineStartSym;
}
const MCSymbol *MCDwarfFileTable::EmitCU(MCStreamer *MCOS, unsigned CUID) {
MCContext &context = MCOS->getContext();
// Create a symbol at the beginning of the line table.
MCSymbol *LineStartSym = MCOS->getContext().getMCLineTableSymbol(CUID);
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).
MCOS->EmitAbsValue(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.
MCOS->EmitAbsValue(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(DWARF2_LINE_OPCODE_BASE, 1);
// Standard opcode lengths
MCOS->EmitIntValue(0, 1); // length of DW_LNS_copy
MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_pc
MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_line
MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_file
MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_column
MCOS->EmitIntValue(0, 1); // length of DW_LNS_negate_stmt
MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_basic_block
MCOS->EmitIntValue(0, 1); // length of DW_LNS_const_add_pc
MCOS->EmitIntValue(1, 1); // length of DW_LNS_fixed_advance_pc
MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_prologue_end
MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_epilogue_begin
MCOS->EmitIntValue(1, 1); // DW_LNS_set_isa
// Put out the directory and file tables.
// First the directory table.
const SmallVectorImpl<StringRef> &MCDwarfDirs =
context.getMCDwarfDirs(CUID);
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.
const SmallVectorImpl<MCDwarfFile *> &MCDwarfFiles =
MCOS->getContext().getMCDwarfFiles(CUID);
for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
MCOS->EmitBytes(MCDwarfFiles[i]->getName()); // FileName
MCOS->EmitBytes(StringRef("\0", 1)); // the null term. of the string
// the Directory num
MCOS->EmitULEB128IntValue(MCDwarfFiles[i]->getDirIndex());
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);
// Put out the line tables.
const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
MCOS->getContext().getMCLineSections();
const std::vector<const MCSection *> &MCLineSectionOrder =
MCOS->getContext().getMCLineSectionOrder();
for (std::vector<const MCSection*>::const_iterator it =
MCLineSectionOrder.begin(), ie = MCLineSectionOrder.end(); it != ie;
++it) {
const MCSection *Sec = *it;
const MCLineSection *Line = MCLineSections.lookup(Sec);
EmitDwarfLineTable(MCOS, Sec, Line, CUID);
}
if (MCOS->getContext().getAsmInfo()->getLinkerRequiresNonEmptyDwarfLines()
&& MCLineSectionOrder.begin() == MCLineSectionOrder.end()) {
// 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);
return LineStartSym;
}
/// 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);
}
void MCDwarfFile::print(raw_ostream &OS) const {
OS << '"' << getName() << '"';
}
#if !defined(NDEBUG) || defined(LLVM_ENABLE_DUMP)
void MCDwarfFile::dump() const {
print(dbgs());
}
#endif
// 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);
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. Which contains a header and a table of pairs of
// PointerSize'ed values for the address and size of section(s) with line table
// entries (just the default .text in our case) and a terminating pair of zeros.
static void EmitGenDwarfAranges(MCStreamer *MCOS,
const MCSymbol *InfoSectionSymbol) {
MCContext &context = MCOS->getContext();
// Create a symbol at the end of the section that we are creating the dwarf
// debugging info to use later in here as part of the expression to calculate
// the size of the section for the table.
MCOS->SwitchSection(context.getGenDwarfSection());
MCSymbol *SectionEndSym = context.CreateTempSymbol();
MCOS->EmitLabel(SectionEndSym);
context.setGenDwarfSectionEndSym(SectionEndSym);
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 the one default .text section we have in the table.
Length += 2 * AddrSize;
// 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);
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(s)
// address and size, in our case just the one default .text section.
const MCExpr *Addr = MCSymbolRefExpr::Create(
context.getGenDwarfSectionStartSym(), MCSymbolRefExpr::VK_None, context);
const MCExpr *Size = MakeStartMinusEndExpr(*MCOS,
*context.getGenDwarfSectionStartSym(), *SectionEndSym, 0);
MCOS->EmitAbsValue(Addr, AddrSize);
MCOS->EmitAbsValue(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) {
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);
MCOS->EmitAbsValue(Length, 4);
// The 2 byte DWARF version, which is 2.
MCOS->EmitIntValue(2, 2);
// 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) {
MCOS->EmitSymbolValue(AbbrevSectionSymbol, 4);
} else {
MCOS->EmitIntValue(0, 4);
}
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);
} else {
MCOS->EmitIntValue(0, 4);
}
// AT_low_pc, the first address of the default .text section.
const MCExpr *Start = MCSymbolRefExpr::Create(
context.getGenDwarfSectionStartSym(), MCSymbolRefExpr::VK_None, context);
MCOS->EmitAbsValue(Start, AddrSize);
// AT_high_pc, the last address of the default .text section.
const MCExpr *End = MCSymbolRefExpr::Create(
context.getGenDwarfSectionEndSym(), MCSymbolRefExpr::VK_None, context);
MCOS->EmitAbsValue(End, AddrSize);
// AT_name, the name of the source file. Reconstruct from the first directory
// and file table entries.
const SmallVectorImpl<StringRef> &MCDwarfDirs =
context.getMCDwarfDirs();
if (MCDwarfDirs.size() > 0) {
MCOS->EmitBytes(MCDwarfDirs[0]);
MCOS->EmitBytes("/");
}
const SmallVectorImpl<MCDwarfFile *> &MCDwarfFiles =
MCOS->getContext().getMCDwarfFiles();
MCOS->EmitBytes(MCDwarfFiles[1]->getName());
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 "));
MCOS->EmitBytes(StringRef(PACKAGE_VERSION));
MCOS->EmitBytes(StringRef(")"));
}
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<const MCGenDwarfLabelEntry *> &Entries =
MCOS->getContext().getMCGenDwarfLabelEntries();
for (std::vector<const MCGenDwarfLabelEntry *>::const_iterator it =
Entries.begin(), ie = Entries.end(); it != ie;
++it) {
const MCGenDwarfLabelEntry *Entry = *it;
// 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->EmitAbsValue(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);
}
// Deallocate the MCGenDwarfLabelEntry classes that saved away the info
// for the dwarf labels.
for (std::vector<const MCGenDwarfLabelEntry *>::const_iterator it =
Entries.begin(), ie = Entries.end(); it != ie;
++it) {
const MCGenDwarfLabelEntry *Entry = *it;
delete Entry;
}
// 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 Dwarf
// sections.
//
void MCGenDwarfInfo::Emit(MCStreamer *MCOS, const MCSymbol *LineSectionSymbol) {
// Create the dwarf sections in this order (.debug_line already created).
MCContext &context = MCOS->getContext();
const MCAsmInfo *AsmInfo = context.getAsmInfo();
bool CreateDwarfSectionSymbols =
AsmInfo->doesDwarfUseRelocationsAcrossSections();
if (!CreateDwarfSectionSymbols)
LineSectionSymbol = NULL;
MCSymbol *AbbrevSectionSymbol = NULL;
MCSymbol *InfoSectionSymbol = NULL;
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);
}
MCOS->SwitchSection(context.getObjectFileInfo()->getDwarfARangesSection());
// If there are no line table entries then do not emit any section contents.
if (context.getMCLineSections().empty())
return;
// Output the data for .debug_aranges section.
EmitGenDwarfAranges(MCOS, InfoSectionSymbol);
// Output the data for .debug_abbrev section.
EmitGenDwarfAbbrev(MCOS);
// Output the data for .debug_info section.
EmitGenDwarfInfo(MCOS, AbbrevSectionSymbol, LineSectionSymbol);
}
//
// 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 or symbols not in
// the default text.
if (Symbol->isTemporary())
return;
MCContext &context = MCOS->getContext();
if (context.getGenDwarfSection() != 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.
int 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.
MCGenDwarfLabelEntry *Entry =
new MCGenDwarfLabelEntry(Name, FileNumber, LineNumber, Label);
MCOS->getContext().addMCGenDwarfLabelEntry(Entry);
}
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 EmitSymbol(MCStreamer &streamer, const MCSymbol &symbol,
unsigned symbolEncoding, const char *comment = 0) {
MCContext &context = streamer.getContext();
const MCAsmInfo *asmInfo = context.getAsmInfo();
const MCExpr *v = asmInfo->getExprForFDESymbol(&symbol,
symbolEncoding,
streamer);
unsigned size = getSizeForEncoding(streamer, symbolEncoding);
if (streamer.isVerboseAsm() && comment) streamer.AddComment(comment);
streamer.EmitAbsValue(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;
int CIENum;
bool UsingCFI;
bool IsEH;
const MCSymbol *SectionStart;
public:
FrameEmitterImpl(bool usingCFI, bool isEH)
: CFAOffset(0), CIENum(0), UsingCFI(usingCFI), IsEH(isEH),
SectionStart(0) {}
void setSectionStart(const MCSymbol *Label) { SectionStart = Label; }
/// EmitCompactUnwind - Emit the unwind information in a compact way.
void EmitCompactUnwind(MCStreamer &streamer,
const MCDwarfFrameInfo &frame);
const MCSymbol &EmitCIE(MCStreamer &streamer,
const MCSymbol *personality,
unsigned personalityEncoding,
const MCSymbol *lsda,
bool IsSignalFrame,
unsigned lsdaEncoding);
MCSymbol *EmitFDE(MCStreamer &streamer,
const MCSymbol &cieStart,
const MCDwarfFrameInfo &frame);
void EmitCFIInstructions(MCStreamer &streamer,
ArrayRef<MCCFIInstruction> Instrs,
MCSymbol *BaseLabel);
void EmitCFIInstruction(MCStreamer &Streamer,
const MCCFIInstruction &Instr);
};
} // end anonymous namespace
static void EmitEncodingByte(MCStreamer &Streamer, unsigned Encoding,
StringRef Prefix) {
if (Streamer.isVerboseAsm()) {
const char *EncStr;
switch (Encoding) {
default: EncStr = "<unknown encoding>"; break;
case dwarf::DW_EH_PE_absptr: EncStr = "absptr"; break;
case dwarf::DW_EH_PE_omit: EncStr = "omit"; break;
case dwarf::DW_EH_PE_pcrel: EncStr = "pcrel"; break;
case dwarf::DW_EH_PE_udata4: EncStr = "udata4"; break;
case dwarf::DW_EH_PE_udata8: EncStr = "udata8"; break;
case dwarf::DW_EH_PE_sdata4: EncStr = "sdata4"; break;
case dwarf::DW_EH_PE_sdata8: EncStr = "sdata8"; break;
case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata4:
EncStr = "pcrel udata4";
break;
case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4:
EncStr = "pcrel sdata4";
break;
case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8:
EncStr = "pcrel udata8";
break;
case dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8:
EncStr = "screl sdata8";
break;
case dwarf::DW_EH_PE_indirect |dwarf::DW_EH_PE_pcrel|dwarf::DW_EH_PE_udata4:
EncStr = "indirect pcrel udata4";
break;
case dwarf::DW_EH_PE_indirect |dwarf::DW_EH_PE_pcrel|dwarf::DW_EH_PE_sdata4:
EncStr = "indirect pcrel sdata4";
break;
case dwarf::DW_EH_PE_indirect |dwarf::DW_EH_PE_pcrel|dwarf::DW_EH_PE_udata8:
EncStr = "indirect pcrel udata8";
break;
case dwarf::DW_EH_PE_indirect |dwarf::DW_EH_PE_pcrel|dwarf::DW_EH_PE_sdata8:
EncStr = "indirect pcrel sdata8";
break;
}
Streamer.AddComment(Twine(Prefix) + " = " + EncStr);
}
Streamer.EmitIntValue(Encoding, 1);
}
void FrameEmitterImpl::EmitCFIInstruction(MCStreamer &Streamer,
const MCCFIInstruction &Instr) {
int dataAlignmentFactor = getDataAlignmentFactor(Streamer);
bool VerboseAsm = Streamer.isVerboseAsm();
switch (Instr.getOperation()) {
case MCCFIInstruction::OpRegister: {
unsigned Reg1 = Instr.getRegister();
unsigned Reg2 = Instr.getRegister2();
if (VerboseAsm) {
Streamer.AddComment("DW_CFA_register");
Streamer.AddComment(Twine("Reg1 ") + Twine(Reg1));
Streamer.AddComment(Twine("Reg2 ") + Twine(Reg2));
}
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();
if (VerboseAsm) {
Streamer.AddComment("DW_CFA_undefined");
Streamer.AddComment(Twine("Reg ") + Twine(Reg));
}
Streamer.EmitIntValue(dwarf::DW_CFA_undefined, 1);
Streamer.EmitULEB128IntValue(Reg);
return;
}
case MCCFIInstruction::OpAdjustCfaOffset:
case MCCFIInstruction::OpDefCfaOffset: {
const bool IsRelative =
Instr.getOperation() == MCCFIInstruction::OpAdjustCfaOffset;
if (VerboseAsm)
Streamer.AddComment("DW_CFA_def_cfa_offset");
Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_offset, 1);
if (IsRelative)
CFAOffset += Instr.getOffset();
else
CFAOffset = -Instr.getOffset();
if (VerboseAsm)
Streamer.AddComment(Twine("Offset " + Twine(CFAOffset)));
Streamer.EmitULEB128IntValue(CFAOffset);
return;
}
case MCCFIInstruction::OpDefCfa: {
if (VerboseAsm)
Streamer.AddComment("DW_CFA_def_cfa");
Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa, 1);
if (VerboseAsm)
Streamer.AddComment(Twine("Reg ") + Twine(Instr.getRegister()));
Streamer.EmitULEB128IntValue(Instr.getRegister());
CFAOffset = -Instr.getOffset();
if (VerboseAsm)
Streamer.AddComment(Twine("Offset " + Twine(CFAOffset)));
Streamer.EmitULEB128IntValue(CFAOffset);
return;
}
case MCCFIInstruction::OpDefCfaRegister: {
if (VerboseAsm)
Streamer.AddComment("DW_CFA_def_cfa_register");
Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_register, 1);
if (VerboseAsm)
Streamer.AddComment(Twine("Reg ") + Twine(Instr.getRegister()));
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) {
if (VerboseAsm) Streamer.AddComment("DW_CFA_offset_extended_sf");
Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended_sf, 1);
if (VerboseAsm) Streamer.AddComment(Twine("Reg ") + Twine(Reg));
Streamer.EmitULEB128IntValue(Reg);
if (VerboseAsm) Streamer.AddComment(Twine("Offset ") + Twine(Offset));
Streamer.EmitSLEB128IntValue(Offset);
} else if (Reg < 64) {
if (VerboseAsm) Streamer.AddComment(Twine("DW_CFA_offset + Reg(") +
Twine(Reg) + ")");
Streamer.EmitIntValue(dwarf::DW_CFA_offset + Reg, 1);
if (VerboseAsm) Streamer.AddComment(Twine("Offset ") + Twine(Offset));
Streamer.EmitULEB128IntValue(Offset);
} else {
if (VerboseAsm) Streamer.AddComment("DW_CFA_offset_extended");
Streamer.EmitIntValue(dwarf::DW_CFA_offset_extended, 1);
if (VerboseAsm) Streamer.AddComment(Twine("Reg ") + Twine(Reg));
Streamer.EmitULEB128IntValue(Reg);
if (VerboseAsm) Streamer.AddComment(Twine("Offset ") + Twine(Offset));
Streamer.EmitULEB128IntValue(Offset);
}
return;
}
case MCCFIInstruction::OpRememberState:
if (VerboseAsm) Streamer.AddComment("DW_CFA_remember_state");
Streamer.EmitIntValue(dwarf::DW_CFA_remember_state, 1);
return;
case MCCFIInstruction::OpRestoreState:
if (VerboseAsm) Streamer.AddComment("DW_CFA_restore_state");
Streamer.EmitIntValue(dwarf::DW_CFA_restore_state, 1);
return;
case MCCFIInstruction::OpSameValue: {
unsigned Reg = Instr.getRegister();
if (VerboseAsm) Streamer.AddComment("DW_CFA_same_value");
Streamer.EmitIntValue(dwarf::DW_CFA_same_value, 1);
if (VerboseAsm) Streamer.AddComment(Twine("Reg ") + Twine(Reg));
Streamer.EmitULEB128IntValue(Reg);
return;
}
case MCCFIInstruction::OpRestore: {
unsigned Reg = Instr.getRegister();
if (VerboseAsm) {
Streamer.AddComment("DW_CFA_restore");
Streamer.AddComment(Twine("Reg ") + Twine(Reg));
}
Streamer.EmitIntValue(dwarf::DW_CFA_restore | Reg, 1);
return;
}
case MCCFIInstruction::OpEscape:
if (VerboseAsm) Streamer.AddComment("Escape bytes");
Streamer.EmitBytes(Instr.getValues());
return;
}
llvm_unreachable("Unhandled case in switch");
}
/// EmitFrameMoves - Emit frame instructions to describe the layout of the
/// frame.
void FrameEmitterImpl::EmitCFIInstructions(MCStreamer &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) {
if (streamer.isVerboseAsm()) streamer.AddComment("DW_CFA_advance_loc4");
streamer.EmitDwarfAdvanceFrameAddr(BaseLabel, ThisSym);
BaseLabel = ThisSym;
}
}
EmitCFIInstruction(streamer, Instr);
}
}
/// EmitCompactUnwind - Emit the unwind information in a compact way.
void FrameEmitterImpl::EmitCompactUnwind(MCStreamer &Streamer,
const MCDwarfFrameInfo &Frame) {
MCContext &Context = Streamer.getContext();
const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
bool VerboseAsm = Streamer.isVerboseAsm();
// 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(UsingCFI);
unsigned Size = getSizeForEncoding(Streamer, FDEEncoding);
if (VerboseAsm) Streamer.AddComment("Range Start");
Streamer.EmitSymbolValue(Frame.Function, Size);
// Range Length
const MCExpr *Range = MakeStartMinusEndExpr(Streamer, *Frame.Begin,
*Frame.End, 0);
if (VerboseAsm) Streamer.AddComment("Range Length");
Streamer.EmitAbsValue(Range, 4);
// Compact Encoding
Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_udata4);
if (VerboseAsm) Streamer.AddComment("Compact Unwind Encoding: 0x" +
Twine::utohexstr(Encoding));
Streamer.EmitIntValue(Encoding, Size);
// Personality Function
Size = getSizeForEncoding(Streamer, dwarf::DW_EH_PE_absptr);
if (VerboseAsm) Streamer.AddComment("Personality Function");
if (!DwarfEHFrameOnly && Frame.Personality)
Streamer.EmitSymbolValue(Frame.Personality, Size);
else
Streamer.EmitIntValue(0, Size); // No personality fn
// LSDA
Size = getSizeForEncoding(Streamer, Frame.LsdaEncoding);
if (VerboseAsm) Streamer.AddComment("LSDA");
if (!DwarfEHFrameOnly && Frame.Lsda)
Streamer.EmitSymbolValue(Frame.Lsda, Size);
else
Streamer.EmitIntValue(0, Size); // No LSDA
}
const MCSymbol &FrameEmitterImpl::EmitCIE(MCStreamer &streamer,
const MCSymbol *personality,
unsigned personalityEncoding,
const MCSymbol *lsda,
bool IsSignalFrame,
unsigned lsdaEncoding) {
MCContext &context = streamer.getContext();
const MCRegisterInfo *MRI = context.getRegisterInfo();
const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
bool verboseAsm = streamer.isVerboseAsm();
MCSymbol *sectionStart;
if (MOFI->isFunctionEHFrameSymbolPrivate() || !IsEH)
sectionStart = context.CreateTempSymbol();
else
sectionStart = context.GetOrCreateSymbol(Twine("EH_frame") + Twine(CIENum));
streamer.EmitLabel(sectionStart);
CIENum++;
MCSymbol *sectionEnd = context.CreateTempSymbol();
// Length
const MCExpr *Length = MakeStartMinusEndExpr(streamer, *sectionStart,
*sectionEnd, 4);
if (verboseAsm) streamer.AddComment("CIE Length");
streamer.EmitAbsValue(Length, 4);
// CIE ID
unsigned CIE_ID = IsEH ? 0 : -1;
if (verboseAsm) streamer.AddComment("CIE ID Tag");
streamer.EmitIntValue(CIE_ID, 4);
// Version
if (verboseAsm) streamer.AddComment("DW_CIE_VERSION");
streamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1);
// Augmentation String
SmallString<8> Augmentation;
if (IsEH) {
if (verboseAsm) streamer.AddComment("CIE Augmentation");
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
if (verboseAsm) streamer.AddComment("CIE Code Alignment Factor");
streamer.EmitULEB128IntValue(context.getAsmInfo()->getMinInstAlignment());
// Data Alignment Factor
if (verboseAsm) streamer.AddComment("CIE Data Alignment Factor");
streamer.EmitSLEB128IntValue(getDataAlignmentFactor(streamer));
// Return Address Register
if (verboseAsm) streamer.AddComment("CIE Return Address Column");
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;
if (verboseAsm) streamer.AddComment("Augmentation Size");
streamer.EmitULEB128IntValue(augmentationLength);
// Augmentation Data (optional)
if (personality) {
// Personality Encoding
EmitEncodingByte(streamer, personalityEncoding,
"Personality Encoding");
// Personality
if (verboseAsm) streamer.AddComment("Personality");
EmitPersonality(streamer, *personality, personalityEncoding);
}
if (lsda)
EmitEncodingByte(streamer, lsdaEncoding, "LSDA Encoding");
// Encoding of the FDE pointers
EmitEncodingByte(streamer, MOFI->getFDEEncoding(UsingCFI),
"FDE Encoding");
}
// Initial Instructions
const MCAsmInfo *MAI = context.getAsmInfo();
const std::vector<MCCFIInstruction> &Instructions =
MAI->getInitialFrameState();
EmitCFIInstructions(streamer, Instructions, NULL);
// Padding
streamer.EmitValueToAlignment(IsEH ? 4 : MAI->getPointerSize());
streamer.EmitLabel(sectionEnd);
return *sectionStart;
}
MCSymbol *FrameEmitterImpl::EmitFDE(MCStreamer &streamer,
const MCSymbol &cieStart,
const MCDwarfFrameInfo &frame) {
MCContext &context = streamer.getContext();
MCSymbol *fdeStart = context.CreateTempSymbol();
MCSymbol *fdeEnd = context.CreateTempSymbol();
const MCObjectFileInfo *MOFI = context.getObjectFileInfo();
bool verboseAsm = streamer.isVerboseAsm();
if (IsEH && frame.Function && !MOFI->isFunctionEHFrameSymbolPrivate()) {
MCSymbol *EHSym =
context.GetOrCreateSymbol(frame.Function->getName() + Twine(".eh"));
streamer.EmitEHSymAttributes(frame.Function, EHSym);
streamer.EmitLabel(EHSym);
}
// Length
const MCExpr *Length = MakeStartMinusEndExpr(streamer, *fdeStart, *fdeEnd, 0);
if (verboseAsm) streamer.AddComment("FDE Length");
streamer.EmitAbsValue(Length, 4);
streamer.EmitLabel(fdeStart);
// CIE Pointer
const MCAsmInfo *asmInfo = context.getAsmInfo();
if (IsEH) {
const MCExpr *offset = MakeStartMinusEndExpr(streamer, cieStart, *fdeStart,
0);
if (verboseAsm) streamer.AddComment("FDE CIE Offset");
streamer.EmitAbsValue(offset, 4);
} else if (!asmInfo->doesDwarfUseRelocationsAcrossSections()) {
const MCExpr *offset = MakeStartMinusEndExpr(streamer, *SectionStart,
cieStart, 0);
streamer.EmitAbsValue(offset, 4);
} else {
streamer.EmitSymbolValue(&cieStart, 4);
}
// PC Begin
unsigned PCEncoding = IsEH ? MOFI->getFDEEncoding(UsingCFI)
: (unsigned)dwarf::DW_EH_PE_absptr;
unsigned PCSize = getSizeForEncoding(streamer, PCEncoding);
EmitSymbol(streamer, *frame.Begin, PCEncoding, "FDE initial location");
// PC Range
const MCExpr *Range = MakeStartMinusEndExpr(streamer, *frame.Begin,
*frame.End, 0);
if (verboseAsm) streamer.AddComment("FDE address range");
streamer.EmitAbsValue(Range, PCSize);
if (IsEH) {
// Augmentation Data Length
unsigned augmentationLength = 0;
if (frame.Lsda)
augmentationLength += getSizeForEncoding(streamer, frame.LsdaEncoding);
if (verboseAsm) streamer.AddComment("Augmentation size");
streamer.EmitULEB128IntValue(augmentationLength);
// Augmentation Data
if (frame.Lsda)
EmitSymbol(streamer, *frame.Lsda, frame.LsdaEncoding,
"Language Specific Data Area");
}
// Call Frame Instructions
EmitCFIInstructions(streamer, frame.Instructions, frame.Begin);
// Padding
streamer.EmitValueToAlignment(PCSize);
return fdeEnd;
}
namespace {
struct CIEKey {
static const CIEKey getEmptyKey() { return CIEKey(0, 0, -1, false); }
static const CIEKey getTombstoneKey() { return CIEKey(0, -1, 0, false); }
CIEKey(const MCSymbol* Personality_, unsigned PersonalityEncoding_,
unsigned LsdaEncoding_, bool IsSignalFrame_) :
Personality(Personality_), PersonalityEncoding(PersonalityEncoding_),
LsdaEncoding(LsdaEncoding_), IsSignalFrame(IsSignalFrame_) {
}
const MCSymbol* Personality;
unsigned PersonalityEncoding;
unsigned LsdaEncoding;
bool IsSignalFrame;
};
}
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));
}
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;
}
};
}
void MCDwarfFrameEmitter::Emit(MCStreamer &Streamer, MCAsmBackend *MAB,
bool UsingCFI, bool IsEH) {
Streamer.generateCompactUnwindEncodings(MAB);
MCContext &Context = Streamer.getContext();
const MCObjectFileInfo *MOFI = Context.getObjectFileInfo();
FrameEmitterImpl Emitter(UsingCFI, IsEH);
ArrayRef<MCDwarfFrameInfo> FrameArray = Streamer.getFrameInfos();
// Emit the compact unwind info if available.
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;
}
Emitter.EmitCompactUnwind(Streamer, Frame);
}
}
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 = NULL;
DenseMap<CIEKey, const MCSymbol*> CIEStarts;
const MCSymbol *DummyDebugKey = NULL;
for (unsigned i = 0, n = FrameArray.size(); i < n; ++i) {
const MCDwarfFrameInfo &Frame = FrameArray[i];
CIEKey Key(Frame.Personality, Frame.PersonalityEncoding,
Frame.LsdaEncoding, Frame.IsSignalFrame);
const MCSymbol *&CIEStart = IsEH ? CIEStarts[Key] : DummyDebugKey;
if (!CIEStart)
CIEStart = &Emitter.EmitCIE(Streamer, Frame.Personality,
Frame.PersonalityEncoding, Frame.Lsda,
Frame.IsSignalFrame,
Frame.LsdaEncoding);
FDEEnd = Emitter.EmitFDE(Streamer, *CIEStart, Frame);
if (i != n - 1)
Streamer.EmitLabel(FDEEnd);
}
Streamer.EmitValueToAlignment(Context.getAsmInfo()->getPointerSize());
if (FDEEnd)
Streamer.EmitLabel(FDEEnd);
}
void MCDwarfFrameEmitter::EmitAdvanceLoc(MCStreamer &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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