path: root/lib/MC/MCAssembler.cpp

//===- lib/MC/MCAssembler.cpp - Assembler Backend Implementation ----------===//
//
//                     The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "assembler"
#include "llvm/MC/MCAssembler.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Twine.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAsmLayout.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixupKindInfo.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCValue.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LEB128.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/raw_ostream.h"

using namespace llvm;

namespace {
namespace stats {
STATISTIC(EmittedFragments, "Number of emitted assembler fragments");
STATISTIC(evaluateFixup, "Number of evaluated fixups");
STATISTIC(FragmentLayouts, "Number of fragment layouts");
STATISTIC(ObjectBytes, "Number of emitted object file bytes");
STATISTIC(RelaxationSteps, "Number of assembler layout and relaxation steps");
STATISTIC(RelaxedInstructions, "Number of relaxed instructions");
}
}

// FIXME FIXME FIXME: There are number of places in this file where we convert
// what is a 64-bit assembler value used for computation into a value in the
// object file, which may truncate it. We should detect that truncation where
// invalid and report errors back.

/* *** */

MCAsmLayout::MCAsmLayout(MCAssembler &Asm)
  : Assembler(Asm), LastValidFragment()
 {
  // Compute the section layout order. Virtual sections must go last.
  for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
    if (!it->getSection().isVirtualSection())
      SectionOrder.push_back(&*it);
  for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
    if (it->getSection().isVirtualSection())
      SectionOrder.push_back(&*it);
}

bool MCAsmLayout::isFragmentUpToDate(const MCFragment *F) const {
  const MCSectionData &SD = *F->getParent();
  const MCFragment *LastValid = LastValidFragment.lookup(&SD);
  if (!LastValid)
    return false;
  assert(LastValid->getParent() == F->getParent());
  return F->getLayoutOrder() <= LastValid->getLayoutOrder();
}

void MCAsmLayout::Invalidate(MCFragment *F) {
  // If this fragment wasn't already up-to-date, we don't need to do anything.
  if (!isFragmentUpToDate(F))
    return;

  // Otherwise, reset the last valid fragment to this fragment.
  const MCSectionData &SD = *F->getParent();
  LastValidFragment[&SD] = F;
}

void MCAsmLayout::EnsureValid(const MCFragment *F) const {
  MCSectionData &SD = *F->getParent();

  MCFragment *Cur = LastValidFragment[&SD];
  if (!Cur)
    Cur = &*SD.begin();
  else
    Cur = Cur->getNextNode();

  // Advance the layout position until the fragment is up-to-date.
  while (!isFragmentUpToDate(F)) {
    const_cast<MCAsmLayout*>(this)->LayoutFragment(Cur);
    Cur = Cur->getNextNode();
  }
}

uint64_t MCAsmLayout::getFragmentOffset(const MCFragment *F) const {
  EnsureValid(F);
  assert(F->Offset != ~UINT64_C(0) && "Address not set!");
  return F->Offset;
}

uint64_t MCAsmLayout::getSymbolOffset(const MCSymbolData *SD) const {
  const MCSymbol &S = SD->getSymbol();

  // If this is a variable, then recursively evaluate now.
  if (S.isVariable()) {
    MCValue Target;
    if (!S.getVariableValue()->EvaluateAsRelocatable(Target, *this))
      report_fatal_error("unable to evaluate offset for variable '" +
                         S.getName() + "'");

    // Verify that any used symbols are defined.
    if (Target.getSymA() && Target.getSymA()->getSymbol().isUndefined())
      report_fatal_error("unable to evaluate offset to undefined symbol '" +
                         Target.getSymA()->getSymbol().getName() + "'");
    if (Target.getSymB() && Target.getSymB()->getSymbol().isUndefined())
      report_fatal_error("unable to evaluate offset to undefined symbol '" +
                         Target.getSymB()->getSymbol().getName() + "'");

    uint64_t Offset = Target.getConstant();
    if (Target.getSymA())
      Offset += getSymbolOffset(&Assembler.getSymbolData(
                                  Target.getSymA()->getSymbol()));
    if (Target.getSymB())
      Offset -= getSymbolOffset(&Assembler.getSymbolData(
                                  Target.getSymB