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/MC/MCAsmLayout.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCValue.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/ADT/OwningPtr.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/StringExtras.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/TargetRegistry.h"
#include "llvm/Target/TargetAsmBackend.h"

#include <vector>
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");
STATISTIC(SectionLayouts, "Number of section layouts");
}
}

// 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(0)
 {
  // Compute the section layout order. Virtual sections must go last.
  for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
    if (!Asm.getBackend().isVirtualSection(it->getSection()))
      SectionOrder.push_back(&*it);
  for (MCAssembler::iterator it = Asm.begin(), ie = Asm.end(); it != ie; ++it)
    if (Asm.getBackend().isVirtualSection(it->getSection()))
      SectionOrder.push_back(&*it);
}

bool MCAsmLayout::isSectionUpToDate(const MCSectionData *SD) const {
  // The first section is always up-to-date.
  unsigned Index = SD->getLayoutOrder();
  if (!Index)
    return true;

  // Otherwise, sections are always implicitly computed when the preceeding
  // fragment is layed out.
  const MCSectionData *Prev = getSectionOrder()[Index - 1];
  return isFragmentUpToDate(&(Prev->getFragmentList().back()));
}

bool MCAsmLayout::isFragmentUpToDate(const MCFragment *F) const {
  return (LastValidFragment &&
          F->getLayoutOrder() <= LastValidFragment->getLayoutOrder());
}

void MCAsmLayout::UpdateForSlide(MCFragment *F, int SlideAmount) {
  // 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 the predecessor of the
  // invalidated fragment.
  LastValidFragment = F->getPrevNode();
  if (!LastValidFragment) {
    unsigned Index = F->getParent()->getLayoutOrder();
    if (Index != 0) {
      MCSectionData *Prev = getSectionOrder()[Index - 1];
      LastValidFragment = &(Prev->getFragmentList().back());
    }
  }
}

void MCAsmLayout::EnsureValid(const MCFragment *F) const {
  // Advance the layout position until the fragment is up-to-date.
  while (!isFragmentUpToDate(F)) {
    // Advance to the next fragment.
    MCFragment *Cur = LastValidFragment;
    if (Cur)
      Cur = Cur->getNextNode();
    if (!Cur) {
      unsigned NextIndex = 0;
      if (LastValidFragment)
        NextIndex = LastValidFragment->getParent()->getLayoutOrder() + 1;
      Cur = SectionOrder[NextIndex]->begin();
    }

    const_cast<MCAsmLayout*>(this)->LayoutFragment(Cur);
  }
}

void MCAsmLayout::FragmentReplaced(MCFragment *Src, MCFragment *Dst) {
  if (LastValidFragment == Src)
    LastValidFragment = Dst;