path: root/lib/MC/MCDwarf.cpp

//===- 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/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCRegisterInfo.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Support/Path.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/ADT/FoldingSet.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/Twine.h"
#include "llvm/Config/config.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.