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466 lines
17 KiB
C++
466 lines
17 KiB
C++
//===- lib/MC/MCDwarf.cpp - MCDwarf implementation ------------------------===//
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//
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// The LLVM Compiler Infrastructure
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//
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// This file is distributed under the University of Illinois Open Source
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// License. See LICENSE.TXT for details.
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//
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//===----------------------------------------------------------------------===//
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#include "llvm/MC/MCDwarf.h"
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#include "llvm/MC/MCAssembler.h"
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#include "llvm/MC/MCStreamer.h"
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#include "llvm/MC/MCSymbol.h"
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#include "llvm/MC/MCExpr.h"
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#include "llvm/MC/MCContext.h"
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#include "llvm/MC/MCObjectWriter.h"
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#include "llvm/ADT/SmallString.h"
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#include "llvm/Support/Debug.h"
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#include "llvm/Support/raw_ostream.h"
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#include "llvm/Target/TargetAsmBackend.h"
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using namespace llvm;
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// Given a special op, return the address skip amount (in units of
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// DWARF2_LINE_MIN_INSN_LENGTH.
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#define SPECIAL_ADDR(op) (((op) - DWARF2_LINE_OPCODE_BASE)/DWARF2_LINE_RANGE)
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// The maximum address skip amount that can be encoded with a special op.
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#define MAX_SPECIAL_ADDR_DELTA SPECIAL_ADDR(255)
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// First special line opcode - leave room for the standard opcodes.
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// Note: If you want to change this, you'll have to update the
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// "standard_opcode_lengths" table that is emitted in DwarfFileTable::Emit().
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#define DWARF2_LINE_OPCODE_BASE 13
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// Minimum line offset in a special line info. opcode. This value
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// was chosen to give a reasonable range of values.
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#define DWARF2_LINE_BASE -5
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// Range of line offsets in a special line info. opcode.
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# define DWARF2_LINE_RANGE 14
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// Define the architecture-dependent minimum instruction length (in bytes).
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// This value should be rather too small than too big.
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# define DWARF2_LINE_MIN_INSN_LENGTH 1
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// Note: when DWARF2_LINE_MIN_INSN_LENGTH == 1 which is the current setting,
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// this routine is a nop and will be optimized away.
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static inline uint64_t ScaleAddrDelta(uint64_t AddrDelta)
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{
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if (DWARF2_LINE_MIN_INSN_LENGTH == 1)
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return AddrDelta;
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if (AddrDelta % DWARF2_LINE_MIN_INSN_LENGTH != 0) {
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// TODO: report this error, but really only once.
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;
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}
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return AddrDelta / DWARF2_LINE_MIN_INSN_LENGTH;
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}
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//
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// This is called when an instruction is assembled into the specified section
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// and if there is information from the last .loc directive that has yet to have
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// a line entry made for it is made.
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//
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void MCLineEntry::Make(MCStreamer *MCOS, const MCSection *Section) {
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if (!MCOS->getContext().getDwarfLocSeen())
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return;
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// Create a symbol at in the current section for use in the line entry.
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MCSymbol *LineSym = MCOS->getContext().CreateTempSymbol();
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// Set the value of the symbol to use for the MCLineEntry.
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MCOS->EmitLabel(LineSym);
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// Get the current .loc info saved in the context.
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const MCDwarfLoc &DwarfLoc = MCOS->getContext().getCurrentDwarfLoc();
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// Create a (local) line entry with the symbol and the current .loc info.
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MCLineEntry LineEntry(LineSym, DwarfLoc);
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// clear DwarfLocSeen saying the current .loc info is now used.
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MCOS->getContext().ClearDwarfLocSeen();
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// Get the MCLineSection for this section, if one does not exist for this
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// section create it.
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const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
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MCOS->getContext().getMCLineSections();
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MCLineSection *LineSection = MCLineSections.lookup(Section);
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if (!LineSection) {
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// Create a new MCLineSection. This will be deleted after the dwarf line
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// table is created using it by iterating through the MCLineSections
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// DenseMap.
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LineSection = new MCLineSection;
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// Save a pointer to the new LineSection into the MCLineSections DenseMap.
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MCOS->getContext().addMCLineSection(Section, LineSection);
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}
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// Add the line entry to this section's entries.
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LineSection->addLineEntry(LineEntry);
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}
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//
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// This helper routine returns an expression of End - Start + IntVal .
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//
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static inline const MCExpr *MakeStartMinusEndExpr(MCStreamer *MCOS,
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MCSymbol *Start,
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MCSymbol *End, int IntVal) {
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MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
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const MCExpr *Res =
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MCSymbolRefExpr::Create(End, Variant, MCOS->getContext());
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const MCExpr *RHS =
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MCSymbolRefExpr::Create(Start, Variant, MCOS->getContext());
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const MCExpr *Res1 =
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MCBinaryExpr::Create(MCBinaryExpr::Sub, Res, RHS, MCOS->getContext());
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const MCExpr *Res2 =
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MCConstantExpr::Create(IntVal, MCOS->getContext());
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const MCExpr *Res3 =
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MCBinaryExpr::Create(MCBinaryExpr::Sub, Res1, Res2, MCOS->getContext());
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return Res3;
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}
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//
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// This emits an "absolute" address used in the start of a dwarf line number
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// table. This will result in a relocatation entry for the address.
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//
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static inline void EmitDwarfSetAddress(MCStreamer *MCOS,
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MCSymbol *Symbol,
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int PointerSize) {
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MCOS->EmitIntValue(dwarf::DW_LNS_extended_op, 1);
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MCOS->EmitULEB128IntValue(PointerSize + 1);
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MCOS->EmitIntValue(dwarf::DW_LNE_set_address, 1);
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MCOS->EmitSymbolValue(Symbol, PointerSize);
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}
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//
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// This emits the Dwarf line table for the specified section from the entries
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// in the LineSection.
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//
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static inline void EmitDwarfLineTable(MCStreamer *MCOS,
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const MCSection *Section,
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const MCLineSection *LineSection,
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const MCSection *DwarfLineSection,
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MCSectionData *DLS,
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int PointerSize) {
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unsigned FileNum = 1;
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unsigned LastLine = 1;
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unsigned Column = 0;
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unsigned Flags = DWARF2_LINE_DEFAULT_IS_STMT ? DWARF2_FLAG_IS_STMT : 0;
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unsigned Isa = 0;
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MCSymbol *LastLabel = NULL;
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// Loop through each MCLineEntry and encode the dwarf line number table.
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for (MCLineSection::const_iterator
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it = LineSection->getMCLineEntries()->begin(),
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ie = LineSection->getMCLineEntries()->end(); it != ie; ++it) {
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if (FileNum != it->getFileNum()) {
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FileNum = it->getFileNum();
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MCOS->EmitIntValue(dwarf::DW_LNS_set_file, 1);
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MCOS->EmitULEB128IntValue(FileNum);
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}
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if (Column != it->getColumn()) {
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Column = it->getColumn();
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MCOS->EmitIntValue(dwarf::DW_LNS_set_column, 1);
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MCOS->EmitULEB128IntValue(Column);
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}
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if (Isa != it->getIsa()) {
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Isa = it->getIsa();
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MCOS->EmitIntValue(dwarf::DW_LNS_set_isa, 1);
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MCOS->EmitULEB128IntValue(Isa);
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}
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if ((it->getFlags() ^ Flags) & DWARF2_FLAG_IS_STMT) {
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Flags = it->getFlags();
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MCOS->EmitIntValue(dwarf::DW_LNS_negate_stmt, 1);
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}
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if (it->getFlags() & DWARF2_FLAG_BASIC_BLOCK)
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MCOS->EmitIntValue(dwarf::DW_LNS_set_basic_block, 1);
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if (it->getFlags() & DWARF2_FLAG_PROLOGUE_END)
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MCOS->EmitIntValue(dwarf::DW_LNS_set_prologue_end, 1);
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if (it->getFlags() & DWARF2_FLAG_EPILOGUE_BEGIN)
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MCOS->EmitIntValue(dwarf::DW_LNS_set_epilogue_begin, 1);
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int64_t LineDelta = static_cast<int64_t>(it->getLine()) - LastLine;
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MCSymbol *Label = it->getLabel();
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// At this point we want to emit/create the sequence to encode the delta in
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// line numbers and the increment of the address from the previous Label
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// and the current Label.
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if (LastLabel == NULL || DLS == NULL) {
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// emit the sequence to set the address
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EmitDwarfSetAddress(MCOS, Label, PointerSize);
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// emit the sequence for the LineDelta (from 1) and a zero address delta.
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MCDwarfLineAddr::Emit(MCOS, LineDelta, 0);
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}
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else {
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// Create an expression for the address delta from the LastLabel and
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// this Label (plus 0).
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const MCExpr *AddrDelta = MakeStartMinusEndExpr(MCOS, LastLabel, Label,0);
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// Create a Dwarf Line fragment for the LineDelta and AddrDelta.
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new MCDwarfLineAddrFragment(LineDelta, *AddrDelta, DLS);
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}
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LastLine = it->getLine();
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LastLabel = Label;
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}
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// Emit a DW_LNE_end_sequence for the end of the section.
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// Using the pointer Section create a temporary label at the end of the
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// section and use that and the LastLabel to compute the address delta
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// and use INT64_MAX as the line delta which is the signal that this is
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// actually a DW_LNE_end_sequence.
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// Switch to the section to be able to create a symbol at its end.
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MCOS->SwitchSection(Section);
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// Create a symbol at the end of the section.
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MCSymbol *SectionEnd = MCOS->getContext().CreateTempSymbol();
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// Set the value of the symbol, as we are at the end of the section.
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MCOS->EmitLabel(SectionEnd);
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// Switch back the the dwarf line section.
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MCOS->SwitchSection(DwarfLineSection);
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if (DLS == NULL) {
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// emit the sequence to set the address
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EmitDwarfSetAddress(MCOS, SectionEnd, PointerSize);
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// emit the sequence for the LineDelta (from 1) and a zero address delta.
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MCDwarfLineAddr::Emit(MCOS, INT64_MAX, 0);
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} else {
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// Create an expression for the address delta from the LastLabel and this
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// SectionEnd label.
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const MCExpr *AddrDelta = MakeStartMinusEndExpr(MCOS, LastLabel, SectionEnd,
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0);
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// Create a Dwarf Line fragment for the LineDelta and AddrDelta.
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new MCDwarfLineAddrFragment(INT64_MAX, *AddrDelta, DLS);
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}
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}
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//
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// This emits the Dwarf file and the line tables.
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//
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void MCDwarfFileTable::Emit(MCStreamer *MCOS,
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const MCSection *DwarfLineSection,
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MCSectionData *DLS,
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int PointerSize) {
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// Switch to the section where the table will be emitted into.
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MCOS->SwitchSection(DwarfLineSection);
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// Create a symbol at the beginning of this section.
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MCSymbol *LineStartSym = MCOS->getContext().CreateTempSymbol();
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// Set the value of the symbol, as we are at the start of the section.
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MCOS->EmitLabel(LineStartSym);
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// Create a symbol for the end of the section (to be set when we get there).
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MCSymbol *LineEndSym = MCOS->getContext().CreateTempSymbol();
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// The first 4 bytes is the total length of the information for this
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// compilation unit (not including these 4 bytes for the length).
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MCOS->EmitValue(MakeStartMinusEndExpr(MCOS, LineStartSym, LineEndSym, 4),
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4, 0);
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// Next 2 bytes is the Version, which is Dwarf 2.
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MCOS->EmitIntValue(2, 2);
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// Create a symbol for the end of the prologue (to be set when we get there).
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MCSymbol *ProEndSym = MCOS->getContext().CreateTempSymbol(); // Lprologue_end
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// Length of the prologue, is the next 4 bytes. Which is the start of the
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// section to the end of the prologue. Not including the 4 bytes for the
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// total length, the 2 bytes for the version, and these 4 bytes for the
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// length of the prologue.
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MCOS->EmitValue(MakeStartMinusEndExpr(MCOS, LineStartSym, ProEndSym,
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(4 + 2 + 4)),
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4, 0);
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// Parameters of the state machine, are next.
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MCOS->EmitIntValue(DWARF2_LINE_MIN_INSN_LENGTH, 1);
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MCOS->EmitIntValue(DWARF2_LINE_DEFAULT_IS_STMT, 1);
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MCOS->EmitIntValue(DWARF2_LINE_BASE, 1);
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MCOS->EmitIntValue(DWARF2_LINE_RANGE, 1);
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MCOS->EmitIntValue(DWARF2_LINE_OPCODE_BASE, 1);
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// Standard opcode lengths
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MCOS->EmitIntValue(0, 1); // length of DW_LNS_copy
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MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_pc
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MCOS->EmitIntValue(1, 1); // length of DW_LNS_advance_line
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MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_file
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MCOS->EmitIntValue(1, 1); // length of DW_LNS_set_column
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MCOS->EmitIntValue(0, 1); // length of DW_LNS_negate_stmt
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MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_basic_block
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MCOS->EmitIntValue(0, 1); // length of DW_LNS_const_add_pc
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MCOS->EmitIntValue(1, 1); // length of DW_LNS_fixed_advance_pc
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MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_prologue_end
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MCOS->EmitIntValue(0, 1); // length of DW_LNS_set_epilogue_begin
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MCOS->EmitIntValue(1, 1); // DW_LNS_set_isa
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// Put out the directory and file tables.
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// First the directory table.
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const std::vector<StringRef> &MCDwarfDirs =
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MCOS->getContext().getMCDwarfDirs();
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for (unsigned i = 0; i < MCDwarfDirs.size(); i++) {
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MCOS->EmitBytes(MCDwarfDirs[i], 0); // the DirectoryName
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MCOS->EmitBytes(StringRef("\0", 1), 0); // the null term. of the string
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}
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MCOS->EmitIntValue(0, 1); // Terminate the directory list
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// Second the file table.
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const std::vector<MCDwarfFile *> &MCDwarfFiles =
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MCOS->getContext().getMCDwarfFiles();
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for (unsigned i = 1; i < MCDwarfFiles.size(); i++) {
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MCOS->EmitBytes(MCDwarfFiles[i]->getName(), 0); // FileName
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MCOS->EmitBytes(StringRef("\0", 1), 0); // the null term. of the string
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// the Directory num
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MCOS->EmitULEB128IntValue(MCDwarfFiles[i]->getDirIndex());
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MCOS->EmitIntValue(0, 1); // last modification timestamp (always 0)
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MCOS->EmitIntValue(0, 1); // filesize (always 0)
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}
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MCOS->EmitIntValue(0, 1); // Terminate the file list
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// This is the end of the prologue, so set the value of the symbol at the
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// end of the prologue (that was used in a previous expression).
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MCOS->EmitLabel(ProEndSym);
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// Put out the line tables.
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const DenseMap<const MCSection *, MCLineSection *> &MCLineSections =
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MCOS->getContext().getMCLineSections();
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const std::vector<const MCSection *> &MCLineSectionOrder =
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MCOS->getContext().getMCLineSectionOrder();
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for (std::vector<const MCSection*>::const_iterator it =
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MCLineSectionOrder.begin(), ie = MCLineSectionOrder.end(); it != ie;
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++it) {
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const MCSection *Sec = *it;
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const MCLineSection *Line = MCLineSections.lookup(Sec);
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EmitDwarfLineTable(MCOS, Sec, Line, DwarfLineSection, DLS,
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PointerSize);
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// Now delete the MCLineSections that were created in MCLineEntry::Make()
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// and used to emit the line table.
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delete Line;
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}
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// This is the end of the section, so set the value of the symbol at the end
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// of this section (that was used in a previous expression).
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MCOS->EmitLabel(LineEndSym);
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}
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/// Utility function to compute the size of the encoding.
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uint64_t MCDwarfLineAddr::ComputeSize(int64_t LineDelta, uint64_t AddrDelta) {
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SmallString<256> Tmp;
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raw_svector_ostream OS(Tmp);
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MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
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return OS.GetNumBytesInBuffer();
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}
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/// Utility function to write the encoding to an object writer.
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void MCDwarfLineAddr::Write(MCObjectWriter *OW, int64_t LineDelta,
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uint64_t AddrDelta) {
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SmallString<256> Tmp;
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raw_svector_ostream OS(Tmp);
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MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
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OW->WriteBytes(OS.str());
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}
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/// Utility function to emit the encoding to a streamer.
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void MCDwarfLineAddr::Emit(MCStreamer *MCOS, int64_t LineDelta,
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uint64_t AddrDelta) {
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SmallString<256> Tmp;
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raw_svector_ostream OS(Tmp);
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MCDwarfLineAddr::Encode(LineDelta, AddrDelta, OS);
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MCOS->EmitBytes(OS.str(), /*AddrSpace=*/0);
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}
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/// Utility function to encode a Dwarf pair of LineDelta and AddrDeltas.
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void MCDwarfLineAddr::Encode(int64_t LineDelta, uint64_t AddrDelta,
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raw_ostream &OS) {
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uint64_t Temp, Opcode;
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bool NeedCopy = false;
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// Scale the address delta by the minimum instruction length.
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AddrDelta = ScaleAddrDelta(AddrDelta);
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// A LineDelta of INT64_MAX is a signal that this is actually a
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// DW_LNE_end_sequence. We cannot use special opcodes here, since we want the
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// end_sequence to emit the matrix entry.
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if (LineDelta == INT64_MAX) {
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if (AddrDelta == MAX_SPECIAL_ADDR_DELTA)
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OS << char(dwarf::DW_LNS_const_add_pc);
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else {
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OS << char(dwarf::DW_LNS_advance_pc);
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SmallString<32> Tmp;
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raw_svector_ostream OSE(Tmp);
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MCObjectWriter::EncodeULEB128(AddrDelta, OSE);
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OS << OSE.str();
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}
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OS << char(dwarf::DW_LNS_extended_op);
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OS << char(1);
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OS << char(dwarf::DW_LNE_end_sequence);
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return;
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}
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// Bias the line delta by the base.
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Temp = LineDelta - DWARF2_LINE_BASE;
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// If the line increment is out of range of a special opcode, we must encode
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// it with DW_LNS_advance_line.
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if (Temp >= DWARF2_LINE_RANGE) {
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OS << char(dwarf::DW_LNS_advance_line);
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SmallString<32> Tmp;
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raw_svector_ostream OSE(Tmp);
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MCObjectWriter::EncodeSLEB128(LineDelta, OSE);
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OS << OSE.str();
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LineDelta = 0;
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Temp = 0 - DWARF2_LINE_BASE;
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NeedCopy = true;
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}
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// Use DW_LNS_copy instead of a "line +0, addr +0" special opcode.
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if (LineDelta == 0 && AddrDelta == 0) {
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OS << char(dwarf::DW_LNS_copy);
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return;
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}
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// Bias the opcode by the special opcode base.
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Temp += DWARF2_LINE_OPCODE_BASE;
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// Avoid overflow when addr_delta is large.
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if (AddrDelta < 256 + MAX_SPECIAL_ADDR_DELTA) {
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// Try using a special opcode.
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Opcode = Temp + AddrDelta * DWARF2_LINE_RANGE;
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if (Opcode <= 255) {
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|
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());
|
|
}
|
|
|