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llvm/lib/MC/MCDwarf.cpp
Jim Grosbach 958b68140e No reason not to allow defining the CFA as a reg w/ offset zero. 
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@131760 91177308-0d34-0410-b5e6-96231b3b80d8
2011-05-20 21:50:09 +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/ADT/FoldingSet.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetAsmBackend.h"
#include "llvm/Target/TargetAsmInfo.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
// Define the architecture-dependent minimum instruction length (in bytes).
// This value should be rather too small than too big.
# define DWARF2_LINE_MIN_INSN_LENGTH 1
// Note: when DWARF2_LINE_MIN_INSN_LENGTH == 1 which is the current setting,
// this routine is a nop and will be optimized away.
static inline uint64_t ScaleAddrDelta(uint64_t AddrDelta)
{
if (DWARF2_LINE_MIN_INSN_LENGTH == 1)
return AddrDelta;
if (AddrDelta % DWARF2_LINE_MIN_INSN_LENGTH != 0) {
// TODO: report this error, but really only once.
;
}
return AddrDelta / DWARF2_LINE_MIN_INSN_LENGTH;
}
//
// 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);
}
//
// 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 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()->begin(),
ie = LineSection->getMCLineEntries()->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.
MCOS->EmitDwarfAdvanceLineAddr(LineDelta, LastLabel, Label);
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.
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 the dwarf line section.
MCOS->SwitchSection(context.getTargetAsmInfo().getDwarfLineSection());
MCOS->EmitDwarfAdvanceLineAddr(INT64_MAX, LastLabel, SectionEnd);
}
//
// This emits the Dwarf file and the line tables.
//
void MCDwarfFileTable::Emit(MCStreamer *MCOS) {
MCContext &context = MCOS->getContext();
// Switch to the section where the table will be emitted into.
MCOS->SwitchSection(context.getTargetAsmInfo().getDwarfLineSection());
// Create a symbol at the beginning of this section.
MCSymbol *LineStartSym = context.CreateTempSymbol();
// Set the value of the symbol, as we are at the start of the section.
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, 0);
// Parameters of the state machine, are next.
MCOS->EmitIntValue(DWARF2_LINE_MIN_INSN_LENGTH, 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 std::vector<StringRef> &MCDwarfDirs =
context.getMCDwarfDirs();
for (unsigned i = 0; i < MCDwarfDirs.size(); i++) {
MCOS->EmitBytes(MCDwarfDirs[i], 0); // the DirectoryName
MCOS->EmitBytes(StringRef("\0", 1), 0); // the null term. of the string
}
MCOS->EmitIntValue(0, 1); // Terminate the directory list
// Second the file table.
const std::vector<MCDwarfFile *> &MCDwarfFiles =
MCOS->getContext().getMCDwarfFiles();
for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
MCOS->EmitBytes(MCDwarfFiles[i]->getName(), 0); // FileName
MCOS->EmitBytes(StringRef("\0", 1), 0); // 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);
// Now delete the MCLineSections that were created in MCLineEntry::Make()
// and used to emit the line table.
delete Line;
}
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);
}
/// Utility function to write the encoding to an object writer.
void MCDwarfLineAddr::Write(MCObjectWriter *OW, int64_t LineDelta,
uint64_t AddrDelta) {
SmallString<256> Tmp;
raw_svector_ostream OS(Tmp);
MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
OW->WriteBytes(OS.str());
}
/// Utility function to emit the encoding to a streamer.
void MCDwarfLineAddr::Emit(MCStreamer *MCOS, int64_t LineDelta,
uint64_t AddrDelta) {
SmallString<256> Tmp;
raw_svector_ostream OS(Tmp);
MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
MCOS->EmitBytes(OS.str(), /*AddrSpace=*/0);
}
/// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
void MCDwarfLineAddr::Encode(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(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);
SmallString<32> Tmp;
raw_svector_ostream OSE(Tmp);
MCObjectWriter::EncodeULEB128(AddrDelta, OSE);
OS << OSE.str();
}
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);
SmallString<32> Tmp;
raw_svector_ostream OSE(Tmp);
MCObjectWriter::EncodeSLEB128(LineDelta, OSE);
OS << OSE.str();
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);
SmallString<32> Tmp;
raw_svector_ostream OSE(Tmp);
MCObjectWriter::EncodeULEB128(AddrDelta, OSE);
OS << OSE.str();
if (NeedCopy)
OS << char(dwarf::DW_LNS_copy);
else
OS << char(Temp);
}
void MCDwarfFile::print(raw_ostream &OS) const {
OS << '"' << getName() << '"';
}
void MCDwarfFile::dump() const {
print(dbgs());
}
static int getDataAlignmentFactor(MCStreamer &streamer) {
MCContext &context = streamer.getContext();
const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
int size = asmInfo.getPointerSize();
if (asmInfo.getStackGrowthDirection() == TargetFrameLowering::StackGrowsUp)
return size;
else
return -size;
}
static unsigned getSizeForEncoding(MCStreamer &streamer,
unsigned symbolEncoding) {
MCContext &context = streamer.getContext();
const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
unsigned format = symbolEncoding & 0x0f;
switch (format) {
default:
assert(0 && "Unknown Encoding");
case dwarf::DW_EH_PE_absptr:
case dwarf::DW_EH_PE_signed:
return asmInfo.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) {
MCContext &context = streamer.getContext();
const MCAsmInfo &asmInfo = context.getAsmInfo();
const MCExpr *v = asmInfo.getExprForFDESymbol(&symbol,
symbolEncoding,
streamer);
unsigned size = getSizeForEncoding(streamer, symbolEncoding);
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);
}
static const MachineLocation TranslateMachineLocation(
const TargetAsmInfo &AsmInfo,
const MachineLocation &Loc) {
unsigned Reg = Loc.getReg() == MachineLocation::VirtualFP ?
MachineLocation::VirtualFP :
unsigned(AsmInfo.getDwarfRegNum(Loc.getReg(), true));
const MachineLocation &NewLoc = Loc.isReg() ?
MachineLocation(Reg) : MachineLocation(Reg, Loc.getOffset());
return NewLoc;
}
namespace {
class FrameEmitterImpl {
int CFAOffset;
int CIENum;
bool UsingCFI;
bool IsEH;
const MCSymbol *SectionStart;
public:
FrameEmitterImpl(bool usingCFI, bool isEH, const MCSymbol *sectionStart) :
CFAOffset(0), CIENum(0), UsingCFI(usingCFI), IsEH(isEH),
SectionStart(sectionStart) {
}
const MCSymbol &EmitCIE(MCStreamer &streamer,
const MCSymbol *personality,
unsigned personalityEncoding,
const MCSymbol *lsda,
unsigned lsdaEncoding);
MCSymbol *EmitFDE(MCStreamer &streamer,
const MCSymbol &cieStart,
const MCDwarfFrameInfo &frame);
void EmitCFIInstructions(MCStreamer &streamer,
const std::vector<MCCFIInstruction> &Instrs,
MCSymbol *BaseLabel);
void EmitCFIInstruction(MCStreamer &Streamer,
const MCCFIInstruction &Instr);
};
}
void FrameEmitterImpl::EmitCFIInstruction(MCStreamer &Streamer,
const MCCFIInstruction &Instr) {
int dataAlignmentFactor = getDataAlignmentFactor(Streamer);
switch (Instr.getOperation()) {
case MCCFIInstruction::Move:
case MCCFIInstruction::RelMove: {
const MachineLocation &Dst = Instr.getDestination();
const MachineLocation &Src = Instr.getSource();
const bool IsRelative = Instr.getOperation() == MCCFIInstruction::RelMove;
// If advancing cfa.
if (Dst.isReg() && Dst.getReg() == MachineLocation::VirtualFP) {
if (Src.getReg() == MachineLocation::VirtualFP) {
Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_offset, 1);
} else {
Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa, 1);
Streamer.EmitULEB128IntValue(Src.getReg());
}
if (IsRelative)
CFAOffset += Src.getOffset();
else
CFAOffset = -Src.getOffset();
Streamer.EmitULEB128IntValue(CFAOffset);
return;
}
if (Src.isReg() && Src.getReg() == MachineLocation::VirtualFP) {
assert(Dst.isReg() && "Machine move not supported yet.");
Streamer.EmitIntValue(dwarf::DW_CFA_def_cfa_register, 1);
Streamer.EmitULEB128IntValue(Dst.getReg());
return;
}
unsigned Reg = Src.getReg();
int Offset = Dst.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::Remember:
Streamer.EmitIntValue(dwarf::DW_CFA_remember_state, 1);
return;
case MCCFIInstruction::Restore:
Streamer.EmitIntValue(dwarf::DW_CFA_restore_state, 1);
return;
case MCCFIInstruction::SameValue: {
unsigned Reg = Instr.getDestination().getReg();
Streamer.EmitIntValue(dwarf::DW_CFA_same_value, 1);
Streamer.EmitULEB128IntValue(Reg);
return;
}
}
llvm_unreachable("Unhandled case in switch");
}
/// EmitFrameMoves - Emit frame instructions to describe the layout of the
/// frame.
void FrameEmitterImpl::EmitCFIInstructions(MCStreamer &streamer,
const std::vector<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);
}
}
const MCSymbol &FrameEmitterImpl::EmitCIE(MCStreamer &streamer,
const MCSymbol *personality,
unsigned personalityEncoding,
const MCSymbol *lsda,
unsigned lsdaEncoding) {
MCContext &context = streamer.getContext();
const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
MCSymbol *sectionStart;
if (asmInfo.isFunctionEHFrameSymbolPrivate() || !IsEH)
sectionStart = context.CreateTempSymbol();
else
sectionStart = context.GetOrCreateSymbol(Twine("EH_frame") + Twine(CIENum));
CIENum++;
MCSymbol *sectionEnd = streamer.getContext().CreateTempSymbol();
// Length
const MCExpr *Length = MakeStartMinusEndExpr(streamer, *sectionStart,
*sectionEnd, 4);
streamer.EmitLabel(sectionStart);
streamer.EmitAbsValue(Length, 4);
// CIE ID
unsigned CIE_ID = IsEH ? 0 : -1;
streamer.EmitIntValue(CIE_ID, 4);
// Version
streamer.EmitIntValue(dwarf::DW_CIE_VERSION, 1);
// Augmentation String
SmallString<8> Augmentation;
if (IsEH) {
Augmentation += "z";
if (personality)
Augmentation += "P";
if (lsda)
Augmentation += "L";
Augmentation += "R";
streamer.EmitBytes(Augmentation.str(), 0);
}
streamer.EmitIntValue(0, 1);
// Code Alignment Factor
streamer.EmitULEB128IntValue(1);
// Data Alignment Factor
streamer.EmitSLEB128IntValue(getDataAlignmentFactor(streamer));
// Return Address Register
streamer.EmitULEB128IntValue(asmInfo.getDwarfRARegNum(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
streamer.EmitIntValue(personalityEncoding, 1);
// Personality
EmitPersonality(streamer, *personality, personalityEncoding);
}
if (lsda)
streamer.EmitIntValue(lsdaEncoding, 1); // LSDA Encoding
// Encoding of the FDE pointers
streamer.EmitIntValue(asmInfo.getFDEEncoding(UsingCFI), 1);
}
// Initial Instructions
const std::vector<MachineMove> Moves = asmInfo.getInitialFrameState();
std::vector<MCCFIInstruction> Instructions;
for (int i = 0, n = Moves.size(); i != n; ++i) {
MCSymbol *Label = Moves[i].getLabel();
const MachineLocation &Dst =
TranslateMachineLocation(asmInfo, Moves[i].getDestination());
const MachineLocation &Src =
TranslateMachineLocation(asmInfo, Moves[i].getSource());
MCCFIInstruction Inst(Label, Dst, Src);
Instructions.push_back(Inst);
}
EmitCFIInstructions(streamer, Instructions, NULL);
// Padding
streamer.EmitValueToAlignment(IsEH ? 4 : asmInfo.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 TargetAsmInfo &TAsmInfo = context.getTargetAsmInfo();
if (!TAsmInfo.isFunctionEHFrameSymbolPrivate() && IsEH) {
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);
streamer.EmitAbsValue(Length, 4);
streamer.EmitLabel(fdeStart);
// CIE Pointer
const MCAsmInfo &asmInfo = context.getAsmInfo();
if (IsEH) {
const MCExpr *offset = MakeStartMinusEndExpr(streamer, cieStart, *fdeStart,
0);
streamer.EmitAbsValue(offset, 4);
} else if (!asmInfo.doesDwarfRequireRelocationForSectionOffset()) {
const MCExpr *offset = MakeStartMinusEndExpr(streamer, *SectionStart,
cieStart, 0);
streamer.EmitAbsValue(offset, 4);
} else {
streamer.EmitSymbolValue(&cieStart, 4);
}
unsigned fdeEncoding = TAsmInfo.getFDEEncoding(UsingCFI);
unsigned size = getSizeForEncoding(streamer, fdeEncoding);
// PC Begin
unsigned PCBeginEncoding = IsEH ? fdeEncoding :
(unsigned)dwarf::DW_EH_PE_absptr;
unsigned PCBeginSize = getSizeForEncoding(streamer, PCBeginEncoding);
EmitSymbol(streamer, *frame.Begin, PCBeginEncoding);
// PC Range
const MCExpr *Range = MakeStartMinusEndExpr(streamer, *frame.Begin,
*frame.End, 0);
streamer.EmitAbsValue(Range, size);
if (IsEH) {
// Augmentation Data Length
unsigned augmentationLength = 0;
if (frame.Lsda)
augmentationLength += getSizeForEncoding(streamer, frame.LsdaEncoding);
streamer.EmitULEB128IntValue(augmentationLength);
// Augmentation Data
if (frame.Lsda)
EmitSymbol(streamer, *frame.Lsda, frame.LsdaEncoding);
}
// Call Frame Instructions
EmitCFIInstructions(streamer, frame.Instructions, frame.Begin);
// Padding
streamer.EmitValueToAlignment(PCBeginSize);
return fdeEnd;
}
namespace {
struct CIEKey {
static const CIEKey getEmptyKey() { return CIEKey(0, 0, -1); }
static const CIEKey getTombstoneKey() { return CIEKey(0, -1, 0); }
CIEKey(const MCSymbol* Personality_, unsigned PersonalityEncoding_,
unsigned LsdaEncoding_) : Personality(Personality_),
PersonalityEncoding(PersonalityEncoding_),
LsdaEncoding(LsdaEncoding_) {
}
const MCSymbol* Personality;
unsigned PersonalityEncoding;
unsigned LsdaEncoding;
};
}
namespace llvm {
template <>
struct DenseMapInfo<CIEKey> {
static CIEKey getEmptyKey() {
return CIEKey::getEmptyKey();
}
static CIEKey getTombstoneKey() {
return CIEKey::getTombstoneKey();
}
static unsigned getHashValue(const CIEKey &Key) {
FoldingSetNodeID ID;
ID.AddPointer(Key.Personality);
ID.AddInteger(Key.PersonalityEncoding);
ID.AddInteger(Key.LsdaEncoding);
return ID.ComputeHash();
}
static bool isEqual(const CIEKey &LHS,
const CIEKey &RHS) {
return LHS.Personality == RHS.Personality &&
LHS.PersonalityEncoding == RHS.PersonalityEncoding &&
LHS.LsdaEncoding == RHS.LsdaEncoding;
}
};
}
void MCDwarfFrameEmitter::Emit(MCStreamer &streamer,
bool usingCFI,
bool isEH) {
MCContext &context = streamer.getContext();
const TargetAsmInfo &asmInfo = context.getTargetAsmInfo();
const MCSection &section = isEH ?
*asmInfo.getEHFrameSection() : *asmInfo.getDwarfFrameSection();
streamer.SwitchSection(&section);
MCSymbol *SectionStart = context.CreateTempSymbol();
streamer.EmitLabel(SectionStart);
MCSymbol *fdeEnd = NULL;
DenseMap<CIEKey, const MCSymbol*> CIEStarts;
FrameEmitterImpl Emitter(usingCFI, isEH, SectionStart);
const MCSymbol *DummyDebugKey = NULL;
for (unsigned i = 0, n = streamer.getNumFrameInfos(); i < n; ++i) {
const MCDwarfFrameInfo &frame = streamer.getFrameInfo(i);
CIEKey key(frame.Personality, frame.PersonalityEncoding,
frame.LsdaEncoding);
const MCSymbol *&cieStart = isEH ? CIEStarts[key] : DummyDebugKey;
if (!cieStart)
cieStart = &Emitter.EmitCIE(streamer, frame.Personality,
frame.PersonalityEncoding, frame.Lsda,
frame.LsdaEncoding);
fdeEnd = Emitter.EmitFDE(streamer, *cieStart, frame);
if (i != n - 1)
streamer.EmitLabel(fdeEnd);
}
streamer.EmitValueToAlignment(asmInfo.getPointerSize());
if (fdeEnd)
streamer.EmitLabel(fdeEnd);
}
void MCDwarfFrameEmitter::EmitAdvanceLoc(MCStreamer &Streamer,
uint64_t AddrDelta) {
SmallString<256> Tmp;
raw_svector_ostream OS(Tmp);
MCDwarfFrameEmitter::EncodeAdvanceLoc(AddrDelta, OS);
Streamer.EmitBytes(OS.str(), /*AddrSpace=*/0);
}
void MCDwarfFrameEmitter::EncodeAdvanceLoc(uint64_t AddrDelta,
raw_ostream &OS) {
// FIXME: Assumes the code alignment factor is 1.
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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