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2c92085034
llvm/lib/MC/MCAssembler.cpp
Rafael Espindola 94ed5fca3f Change MCExpr::EvaluateAsRelocatableImpl of variables to return the original 
variable if recursing fails to simplify it.

Factor AliasedSymbol to be a method of MCSymbol.

Update MCAssembler::EvaluateFixup to match the change in
EvaluateAsRelocatableImpl.

Remove the WeakRefExpr hack, as the object writer now sees the weakref with
no extra effort needed.

Nothing else is using MCTargetExpr, but keep it for now.

Now that the ELF writer sees relocations with aliases, handle

    .weak    foo2
foo2:
    .weak    bar2
    .set    bar2,foo2
    .quad    bar2

the same way gas does and produce a relocation with bar2.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@119152 91177308-0d34-0410-b5e6-96231b3b80d8
2010-11-15 16:33:49 +00:00

1081 lines
35 KiB
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//===- 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;
Dst->Offset = Src->Offset;
Dst->EffectiveSize = Src->EffectiveSize;
}
uint64_t MCAsmLayout::getFragmentAddress(const MCFragment *F) const {
assert(F->getParent() && "Missing section()!");
return getSectionAddress(F->getParent()) + getFragmentOffset(F);
}
uint64_t MCAsmLayout::getFragmentEffectiveSize(const MCFragment *F) const {
EnsureValid(F);
assert(F->EffectiveSize != ~UINT64_C(0) && "Address not set!");
return F->EffectiveSize;
}
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::getSymbolAddress(const MCSymbolData *SD) const {
assert(SD->getFragment() && "Invalid getAddress() on undefined symbol!");
return getFragmentAddress(SD->getFragment()) + SD->getOffset();
}
uint64_t MCAsmLayout::getSectionAddress(const MCSectionData *SD) const {
EnsureValid(SD->begin());
assert(SD->Address != ~UINT64_C(0) && "Address not set!");
return SD->Address;
}
uint64_t MCAsmLayout::getSectionAddressSize(const MCSectionData *SD) const {
// The size is the last fragment's end offset.
const MCFragment &F = SD->getFragmentList().back();
return getFragmentOffset(&F) + getFragmentEffectiveSize(&F);
}
uint64_t MCAsmLayout::getSectionFileSize(const MCSectionData *SD) const {
// Virtual sections have no file size.
if (getAssembler().getBackend().isVirtualSection(SD->getSection()))
return 0;
// Otherwise, the file size is the same as the address space size.
return getSectionAddressSize(SD);
}
uint64_t MCAsmLayout::getSectionSize(const MCSectionData *SD) const {
// The logical size is the address space size minus any tail padding.
uint64_t Size = getSectionAddressSize(SD);
const MCAlignFragment *AF =
dyn_cast<MCAlignFragment>(&(SD->getFragmentList().back()));
if (AF && AF->hasOnlyAlignAddress())
Size -= getFragmentEffectiveSize(AF);
return Size;
}
/* *** */
MCFragment::MCFragment() : Kind(FragmentType(~0)) {
}
MCFragment::~MCFragment() {
}
MCFragment::MCFragment(FragmentType _Kind, MCSectionData *_Parent)
: Kind(_Kind), Parent(_Parent), Atom(0), Offset(~UINT64_C(0)),
EffectiveSize(~UINT64_C(0))
{
if (Parent)
Parent->getFragmentList().push_back(this);
}
/* *** */
MCSectionData::MCSectionData() : Section(0) {}
MCSectionData::MCSectionData(const MCSection &_Section, MCAssembler *A)
: Section(&_Section),
Alignment(1),
Address(~UINT64_C(0)),
HasInstructions(false)
{
if (A)
A->getSectionList().push_back(this);
}
/* *** */
MCSymbolData::MCSymbolData() : Symbol(0) {}
MCSymbolData::MCSymbolData(const MCSymbol &_Symbol, MCFragment *_Fragment,
uint64_t _Offset, MCAssembler *A)
: Symbol(&_Symbol), Fragment(_Fragment), Offset(_Offset),
IsExternal(false), IsPrivateExtern(false),
CommonSize(0), SymbolSize(0), CommonAlign(0),
Flags(0), Index(0)
{
if (A)
A->getSymbolList().push_back(this);
}
/* *** */
MCAssembler::MCAssembler(MCContext &_Context, TargetAsmBackend &_Backend,
MCCodeEmitter &_Emitter, bool _PadSectionToAlignment,
raw_ostream &_OS)
: Context(_Context), Backend(_Backend), Emitter(_Emitter),
OS(_OS), RelaxAll(false), SubsectionsViaSymbols(false),
PadSectionToAlignment(_PadSectionToAlignment)
{
}
MCAssembler::~MCAssembler() {
}
bool MCAssembler::isSymbolLinkerVisible(const MCSymbol &Symbol) const {
// Non-temporary labels should always be visible to the linker.
if (!Symbol.isTemporary())
return true;
// Absolute temporary labels are never visible.
if (!Symbol.isInSection())
return false;
// Otherwise, check if the section requires symbols even for temporary labels.
return getBackend().doesSectionRequireSymbols(Symbol.getSection());
}
const MCSymbolData *MCAssembler::getAtom(const MCSymbolData *SD) const {
// Linker visible symbols define atoms.
if (isSymbolLinkerVisible(SD->getSymbol()))
return SD;
// Absolute and undefined symbols have no defining atom.
if (!SD->getFragment())
return 0;
// Non-linker visible symbols in sections which can't be atomized have no
// defining atom.
if (!getBackend().isSectionAtomizable(
SD->getFragment()->getParent()->getSection()))
return 0;
// Otherwise, return the atom for the containing fragment.
return SD->getFragment()->getAtom();
}
bool MCAssembler::EvaluateFixup(const MCObjectWriter &Writer,
const MCAsmLayout &Layout,
const MCFixup &Fixup, const MCFragment *DF,
MCValue &Target, uint64_t &Value) const {
++stats::EvaluateFixup;
if (!Fixup.getValue()->EvaluateAsRelocatable(Target, &Layout))
report_fatal_error("expected relocatable expression");
// FIXME: How do non-scattered symbols work in ELF? I presume the linker
// doesn't support small relocations, but then under what criteria does the
// assembler allow symbol differences?
Value = Target.getConstant();
bool IsPCRel = Emitter.getFixupKindInfo(
Fixup.getKind()).Flags & MCFixupKindInfo::FKF_IsPCRel;
bool IsResolved = true;
if (const MCSymbolRefExpr *A = Target.getSymA()) {
const MCSymbol &Sym = A->getSymbol().AliasedSymbol();
if (Sym.isDefined())
Value += Layout.getSymbolAddress(&getSymbolData(Sym));
else
IsResolved = false;
}
if (const MCSymbolRefExpr *B = Target.getSymB()) {
const MCSymbol &Sym = B->getSymbol().AliasedSymbol();
if (Sym.isDefined())
Value -= Layout.getSymbolAddress(&getSymbolData(Sym));
else
IsResolved = false;
}
if (IsResolved)
IsResolved = Writer.IsFixupFullyResolved(*this, Target, IsPCRel, DF);
if (IsPCRel)
Value -= Layout.getFragmentAddress(DF) + Fixup.getOffset();
return IsResolved;
}
uint64_t MCAssembler::ComputeFragmentSize(MCAsmLayout &Layout,
const MCFragment &F,
uint64_t SectionAddress,
uint64_t FragmentOffset) const {
switch (F.getKind()) {
case MCFragment::FT_Data:
return cast<MCDataFragment>(F).getContents().size();
case MCFragment::FT_Fill:
return cast<MCFillFragment>(F).getSize();
case MCFragment::FT_Inst:
return cast<MCInstFragment>(F).getInstSize();
case MCFragment::FT_LEB:
return cast<MCLEBFragment>(F).getSize();
case MCFragment::FT_Align: {
const MCAlignFragment &AF = cast<MCAlignFragment>(F);
assert((!AF.hasOnlyAlignAddress() || !AF.getNextNode()) &&
"Invalid OnlyAlignAddress bit, not the last fragment!");
uint64_t Size = OffsetToAlignment(SectionAddress + FragmentOffset,
AF.getAlignment());
// Honor MaxBytesToEmit.
if (Size > AF.getMaxBytesToEmit())
return 0;
return Size;
}
case MCFragment::FT_Org:
return cast<MCOrgFragment>(F).getSize();
case MCFragment::FT_Dwarf:
return cast<MCDwarfLineAddrFragment>(F).getSize();
}
assert(0 && "invalid fragment kind");
return 0;
}
void MCAsmLayout::LayoutFile() {
// Initialize the first section and set the valid fragment layout point. All
// actual layout computations are done lazily.
LastValidFragment = 0;
if (!getSectionOrder().empty())
getSectionOrder().front()->Address = 0;
}
void MCAsmLayout::LayoutFragment(MCFragment *F) {
MCFragment *Prev = F->getPrevNode();
// We should never try to recompute something which is up-to-date.
assert(!isFragmentUpToDate(F) && "Attempt to recompute up-to-date fragment!");
// We should never try to compute the fragment layout if the section isn't
// up-to-date.
assert(isSectionUpToDate(F->getParent()) &&
"Attempt to compute fragment before it's section!");
// We should never try to compute the fragment layout if it's predecessor
// isn't up-to-date.
assert((!Prev || isFragmentUpToDate(Prev)) &&
"Attempt to compute fragment before it's predecessor!");
++stats::FragmentLayouts;
// Compute the fragment start address.
uint64_t StartAddress = F->getParent()->Address;
uint64_t Address = StartAddress;
if (Prev)
Address += Prev->Offset + Prev->EffectiveSize;
// Compute fragment offset and size.
F->Offset = Address - StartAddress;
F->EffectiveSize = getAssembler().ComputeFragmentSize(*this, *F, StartAddress,
F->Offset);
LastValidFragment = F;
// If this is the last fragment in a section, update the next section address.
if (!F->getNextNode()) {
unsigned NextIndex = F->getParent()->getLayoutOrder() + 1;
if (NextIndex != getSectionOrder().size())
LayoutSection(getSectionOrder()[NextIndex]);
}
}
void MCAsmLayout::LayoutSection(MCSectionData *SD) {
unsigned SectionOrderIndex = SD->getLayoutOrder();
++stats::SectionLayouts;
// Compute the section start address.
uint64_t StartAddress = 0;
if (SectionOrderIndex) {
MCSectionData *Prev = getSectionOrder()[SectionOrderIndex - 1];
StartAddress = getSectionAddress(Prev) + getSectionAddressSize(Prev);
}
// Honor the section alignment requirements.
StartAddress = RoundUpToAlignment(StartAddress, SD->getAlignment());
// Set the section address.
SD->Address = StartAddress;
}
/// WriteFragmentData - Write the \arg F data to the output file.
static void WriteFragmentData(const MCAssembler &Asm, const MCAsmLayout &Layout,
const MCFragment &F, MCObjectWriter *OW) {
uint64_t Start = OW->getStream().tell();
(void) Start;
++stats::EmittedFragments;
// FIXME: Embed in fragments instead?
uint64_t FragmentSize = Layout.getFragmentEffectiveSize(&F);
switch (F.getKind()) {
case MCFragment::FT_Align: {
MCAlignFragment &AF = cast<MCAlignFragment>(F);
uint64_t Count = FragmentSize / AF.getValueSize();
assert(AF.getValueSize() && "Invalid virtual align in concrete fragment!");
// FIXME: This error shouldn't actually occur (the front end should emit
// multiple .align directives to enforce the semantics it wants), but is
// severe enough that we want to report it. How to handle this?
if (Count * AF.getValueSize() != FragmentSize)
report_fatal_error("undefined .align directive, value size '" +
Twine(AF.getValueSize()) +
"' is not a divisor of padding size '" +
Twine(FragmentSize) + "'");
// See if we are aligning with nops, and if so do that first to try to fill
// the Count bytes. Then if that did not fill any bytes or there are any
// bytes left to fill use the the Value and ValueSize to fill the rest.
// If we are aligning with nops, ask that target to emit the right data.
if (AF.hasEmitNops()) {
if (!Asm.getBackend().WriteNopData(Count, OW))
report_fatal_error("unable to write nop sequence of " +
Twine(Count) + " bytes");
break;
}
// Otherwise, write out in multiples of the value size.
for (uint64_t i = 0; i != Count; ++i) {
switch (AF.getValueSize()) {
default:
assert(0 && "Invalid size!");
case 1: OW->Write8 (uint8_t (AF.getValue())); break;
case 2: OW->Write16(uint16_t(AF.getValue())); break;
case 4: OW->Write32(uint32_t(AF.getValue())); break;
case 8: OW->Write64(uint64_t(AF.getValue())); break;
}
}
break;
}
case MCFragment::FT_Data: {
MCDataFragment &DF = cast<MCDataFragment>(F);
assert(FragmentSize == DF.getContents().size() && "Invalid size!");
OW->WriteBytes(DF.getContents().str());
break;
}
case MCFragment::FT_Fill: {
MCFillFragment &FF = cast<MCFillFragment>(F);
assert(FF.getValueSize() && "Invalid virtual align in concrete fragment!");
for (uint64_t i = 0, e = FF.getSize() / FF.getValueSize(); i != e; ++i) {
switch (FF.getValueSize()) {
default:
assert(0 && "Invalid size!");
case 1: OW->Write8 (uint8_t (FF.getValue())); break;
case 2: OW->Write16(uint16_t(FF.getValue())); break;
case 4: OW->Write32(uint32_t(FF.getValue())); break;
case 8: OW->Write64(uint64_t(FF.getValue())); break;
}
}
break;
}
case MCFragment::FT_Inst:
llvm_unreachable("unexpected inst fragment after lowering");
break;
case MCFragment::FT_LEB: {
MCLEBFragment &LF = cast<MCLEBFragment>(F);
// FIXME: It is probably better if we don't call EvaluateAsAbsolute in
// here.
int64_t Value;
LF.getValue().EvaluateAsAbsolute(Value, &Layout);
SmallString<32> Tmp;
raw_svector_ostream OSE(Tmp);
if (LF.isSigned())
MCObjectWriter::EncodeSLEB128(Value, OSE);
else
MCObjectWriter::EncodeULEB128(Value, OSE);
OW->WriteBytes(OSE.str());
break;
}
case MCFragment::FT_Org: {
MCOrgFragment &OF = cast<MCOrgFragment>(F);
for (uint64_t i = 0, e = FragmentSize; i != e; ++i)
OW->Write8(uint8_t(OF.getValue()));
break;
}
case MCFragment::FT_Dwarf: {
const MCDwarfLineAddrFragment &OF = cast<MCDwarfLineAddrFragment>(F);
// The AddrDelta is really unsigned and it can only increase.
int64_t AddrDelta;
OF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
int64_t LineDelta;
LineDelta = OF.getLineDelta();
MCDwarfLineAddr::Write(OW, LineDelta, (uint64_t)AddrDelta);
break;
}
}
assert(OW->getStream().tell() - Start == FragmentSize);
}
void MCAssembler::WriteSectionData(const MCSectionData *SD,
const MCAsmLayout &Layout,
MCObjectWriter *OW) const {
// Ignore virtual sections.
if (getBackend().isVirtualSection(SD->getSection())) {
assert(Layout.getSectionFileSize(SD) == 0 && "Invalid size for section!");
// Check that contents are only things legal inside a virtual section.
for (MCSectionData::const_iterator it = SD->begin(),
ie = SD->end(); it != ie; ++it) {
switch (it->getKind()) {
default:
assert(0 && "Invalid fragment in virtual section!");
case MCFragment::FT_Data: {
// Check that we aren't trying to write a non-zero contents (or fixups)
// into a virtual section. This is to support clients which use standard
// directives to fill the contents of virtual sections.
MCDataFragment &DF = cast<MCDataFragment>(*it);
assert(DF.fixup_begin() == DF.fixup_end() &&
"Cannot have fixups in virtual section!");
for (unsigned i = 0, e = DF.getContents().size(); i != e; ++i)
assert(DF.getContents()[i] == 0 &&
"Invalid data value for virtual section!");
break;
}
case MCFragment::FT_Align:
// Check that we aren't trying to write a non-zero value into a virtual
// section.
assert((!cast<MCAlignFragment>(it)->getValueSize() ||
!cast<MCAlignFragment>(it)->getValue()) &&
"Invalid align in virtual section!");
break;
case MCFragment::FT_Fill:
assert(!cast<MCFillFragment>(it)->getValueSize() &&
"Invalid fill in virtual section!");
break;
}
}
return;
}
uint64_t Start = OW->getStream().tell();
(void) Start;
for (MCSectionData::const_iterator it = SD->begin(),
ie = SD->end(); it != ie; ++it)
WriteFragmentData(*this, Layout, *it, OW);
assert(OW->getStream().tell() - Start == Layout.getSectionFileSize(SD));
}
void MCAssembler::AddSectionToTheEnd(const MCObjectWriter &Writer,
MCSectionData &SD, MCAsmLayout &Layout) {
// Create dummy fragments and assign section ordinals.
unsigned SectionIndex = size();
SD.setOrdinal(SectionIndex);
// Assign layout order indices to sections and fragments.
const MCFragment &Last = *Layout.getSectionOrder().back()->rbegin();
unsigned FragmentIndex = Last.getLayoutOrder() + 1;
SD.setLayoutOrder(Layout.getSectionOrder().size());
for (MCSectionData::iterator it2 = SD.begin(),
ie2 = SD.end(); it2 != ie2; ++it2) {
it2->setLayoutOrder(FragmentIndex++);
}
Layout.getSectionOrder().push_back(&SD);
Layout.LayoutSection(&SD);
}
void MCAssembler::Finish(MCObjectWriter *Writer) {
DEBUG_WITH_TYPE("mc-dump", {
llvm::errs() << "assembler backend - pre-layout\n--\n";
dump(); });
// Create the layout object.
MCAsmLayout Layout(*this);
// Insert additional align fragments for concrete sections to explicitly pad
// the previous section to match their alignment requirements. This is for
// 'gas' compatibility, it shouldn't strictly be necessary.
if (PadSectionToAlignment) {
for (unsigned i = 1, e = Layout.getSectionOrder().size(); i < e; ++i) {
MCSectionData *SD = Layout.getSectionOrder()[i];
// Ignore sections without alignment requirements.
unsigned Align = SD->getAlignment();
if (Align <= 1)
continue;
// Ignore virtual sections, they don't cause file size modifications.
if (getBackend().isVirtualSection(SD->getSection()))
continue;
// Otherwise, create a new align fragment at the end of the previous
// section.
MCAlignFragment *AF = new MCAlignFragment(Align, 0, 1, Align,
Layout.getSectionOrder()[i - 1]);
AF->setOnlyAlignAddress(true);
}
}
// Create dummy fragments and assign section ordinals.
unsigned SectionIndex = 0;
for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
// Create dummy fragments to eliminate any empty sections, this simplifies
// layout.
if (it->getFragmentList().empty())
new MCDataFragment(it);
it->setOrdinal(SectionIndex++);
}
// Assign layout order indices to sections and fragments.
unsigned FragmentIndex = 0;
for (unsigned i = 0, e = Layout.getSectionOrder().size(); i != e; ++i) {
MCSectionData *SD = Layout.getSectionOrder()[i];
SD->setLayoutOrder(i);
for (MCSectionData::iterator it2 = SD->begin(),
ie2 = SD->end(); it2 != ie2; ++it2)
it2->setLayoutOrder(FragmentIndex++);
}
llvm::OwningPtr<MCObjectWriter> OwnWriter(0);
if (Writer == 0) {
//no custom Writer_ : create the default one life-managed by OwningPtr
OwnWriter.reset(getBackend().createObjectWriter(OS));
Writer = OwnWriter.get();
if (!Writer)
report_fatal_error("unable to create object writer!");
}
// Layout until everything fits.
while (LayoutOnce(*Writer, Layout))
continue;
DEBUG_WITH_TYPE("mc-dump", {
llvm::errs() << "assembler backend - post-relaxation\n--\n";
dump(); });
// Finalize the layout, including fragment lowering.
FinishLayout(Layout);
DEBUG_WITH_TYPE("mc-dump", {
llvm::errs() << "assembler backend - final-layout\n--\n";
dump(); });
uint64_t StartOffset = OS.tell();
// Allow the object writer a chance to perform post-layout binding (for
// example, to set the index fields in the symbol data).
Writer->ExecutePostLayoutBinding(*this);
// Evaluate and apply the fixups, generating relocation entries as necessary.
for (MCAssembler::iterator it = begin(), ie = end(); it != ie; ++it) {
for (MCSectionData::iterator it2 = it->begin(),
ie2 = it->end(); it2 != ie2; ++it2) {
MCDataFragment *DF = dyn_cast<MCDataFragment>(it2);
if (!DF)
continue;
for (MCDataFragment::fixup_iterator it3 = DF->fixup_begin(),
ie3 = DF->fixup_end(); it3 != ie3; ++it3) {
MCFixup &Fixup = *it3;
// Evaluate the fixup.
MCValue Target;
uint64_t FixedValue;
if (!EvaluateFixup(*Writer, Layout, Fixup, DF, Target, FixedValue)) {
// The fixup was unresolved, we need a relocation. Inform the object
// writer of the relocation, and give it an opportunity to adjust the
// fixup value if need be.
Writer->RecordRelocation(*this, Layout, DF, Fixup, Target,FixedValue);
}
getBackend().ApplyFixup(Fixup, *DF, FixedValue);
}
}
}
// Write the object file.
Writer->WriteObject(*this, Layout);
stats::ObjectBytes += OS.tell() - StartOffset;
}
bool MCAssembler::FixupNeedsRelaxation(const MCObjectWriter &Writer,
const MCFixup &Fixup,
const MCFragment *DF,
const MCAsmLayout &Layout) const {
if (getRelaxAll())
return true;
// If we cannot resolve the fixup value, it requires relaxation.
MCValue Target;
uint64_t Value;
if (!EvaluateFixup(Writer, Layout, Fixup, DF, Target, Value))
return true;
// Otherwise, relax if the value is too big for a (signed) i8.
//
// FIXME: This is target dependent!
return int64_t(Value) != int64_t(int8_t(Value));
}
bool MCAssembler::FragmentNeedsRelaxation(const MCObjectWriter &Writer,
const MCInstFragment *IF,
const MCAsmLayout &Layout) const {
// If this inst doesn't ever need relaxation, ignore it. This occurs when we
// are intentionally pushing out inst fragments, or because we relaxed a
// previous instruction to one that doesn't need relaxation.
if (!getBackend().MayNeedRelaxation(IF->getInst()))
return false;
for (MCInstFragment::const_fixup_iterator it = IF->fixup_begin(),
ie = IF->fixup_end(); it != ie; ++it)
if (FixupNeedsRelaxation(Writer, *it, IF, Layout))
return true;
return false;
}
bool MCAssembler::RelaxInstruction(const MCObjectWriter &Writer,
MCAsmLayout &Layout,
MCInstFragment &IF) {
if (!FragmentNeedsRelaxation(Writer, &IF, Layout))
return false;
++stats::RelaxedInstructions;
// FIXME-PERF: We could immediately lower out instructions if we can tell
// they are fully resolved, to avoid retesting on later passes.
// Relax the fragment.
MCInst Relaxed;
getBackend().RelaxInstruction(IF.getInst(), Relaxed);
// Encode the new instruction.
//
// FIXME-PERF: If it matters, we could let the target do this. It can
// probably do so more efficiently in many cases.
SmallVector<MCFixup, 4> Fixups;
SmallString<256> Code;
raw_svector_ostream VecOS(Code);
getEmitter().EncodeInstruction(Relaxed, VecOS, Fixups);
VecOS.flush();
// Update the instruction fragment.
int SlideAmount = Code.size() - IF.getInstSize();
IF.setInst(Relaxed);
IF.getCode() = Code;
IF.getFixups().clear();
// FIXME: Eliminate copy.
for (unsigned i = 0, e = Fixups.size(); i != e; ++i)
IF.getFixups().push_back(Fixups[i]);
// Update the layout, and remember that we relaxed.
Layout.UpdateForSlide(&IF, SlideAmount);
return true;
}
bool MCAssembler::RelaxOrg(const MCObjectWriter &Writer,
MCAsmLayout &Layout,
MCOrgFragment &OF) {
int64_t TargetLocation;
if (!OF.getOffset().EvaluateAsAbsolute(TargetLocation, &Layout))
report_fatal_error("expected assembly-time absolute expression");
// FIXME: We need a way to communicate this error.
uint64_t FragmentOffset = Layout.getFragmentOffset(&OF);
int64_t Offset = TargetLocation - FragmentOffset;
if (Offset < 0 || Offset >= 0x40000000)
report_fatal_error("invalid .org offset '" + Twine(TargetLocation) +
"' (at offset '" + Twine(FragmentOffset) + "')");
unsigned OldSize = OF.getSize();
OF.setSize(Offset);
return OldSize != OF.getSize();
}
bool MCAssembler::RelaxLEB(const MCObjectWriter &Writer,
MCAsmLayout &Layout,
MCLEBFragment &LF) {
int64_t Value;
LF.getValue().EvaluateAsAbsolute(Value, &Layout);
SmallString<32> Tmp;
raw_svector_ostream OSE(Tmp);
if (LF.isSigned())
MCObjectWriter::EncodeSLEB128(Value, OSE);
else
MCObjectWriter::EncodeULEB128(Value, OSE);
uint64_t OldSize = LF.getSize();
LF.setSize(OSE.GetNumBytesInBuffer());
return OldSize != LF.getSize();
}
bool MCAssembler::RelaxDwarfLineAddr(const MCObjectWriter &Writer,
MCAsmLayout &Layout,
MCDwarfLineAddrFragment &DF) {
int64_t AddrDelta;
DF.getAddrDelta().EvaluateAsAbsolute(AddrDelta, &Layout);
int64_t LineDelta;
LineDelta = DF.getLineDelta();
uint64_t OldSize = DF.getSize();
DF.setSize(MCDwarfLineAddr::ComputeSize(LineDelta, AddrDelta));
return OldSize != DF.getSize();
}
bool MCAssembler::LayoutOnce(const MCObjectWriter &Writer,
MCAsmLayout &Layout) {
++stats::RelaxationSteps;
// Layout the sections in order.
Layout.LayoutFile();
// Scan for fragments that need relaxation.
bool WasRelaxed = false;
for (iterator it = begin(), ie = end(); it != ie; ++it) {
MCSectionData &SD = *it;
for (MCSectionData::iterator it2 = SD.begin(),
ie2 = SD.end(); it2 != ie2; ++it2) {
// Check if this is an fragment that needs relaxation.
switch(it2->getKind()) {
default:
break;
case MCFragment::FT_Inst:
WasRelaxed |= RelaxInstruction(Writer, Layout,
*cast<MCInstFragment>(it2));
break;
case MCFragment::FT_Org:
WasRelaxed |= RelaxOrg(Writer, Layout, *cast<MCOrgFragment>(it2));
break;
case MCFragment::FT_Dwarf:
WasRelaxed |= RelaxDwarfLineAddr(Writer, Layout,
*cast<MCDwarfLineAddrFragment>(it2));
break;
case MCFragment::FT_LEB:
WasRelaxed |= RelaxLEB(Writer, Layout, *cast<MCLEBFragment>(it2));
break;
}
}
}
return WasRelaxed;
}
void MCAssembler::FinishLayout(MCAsmLayout &Layout) {
// Lower out any instruction fragments, to simplify the fixup application and
// output.
//
// FIXME-PERF: We don't have to do this, but the assumption is that it is
// cheap (we will mostly end up eliminating fragments and appending on to data
// fragments), so the extra complexity downstream isn't worth it. Evaluate
// this assumption.
for (iterator it = begin(), ie = end(); it != ie; ++it) {
MCSectionData &SD = *it;
for (MCSectionData::iterator it2 = SD.begin(),
ie2 = SD.end(); it2 != ie2; ++it2) {
MCInstFragment *IF = dyn_cast<MCInstFragment>(it2);
if (!IF)
continue;
// Create a new data fragment for the instruction.
//
// FIXME-PERF: Reuse previous data fragment if possible.
MCDataFragment *DF = new MCDataFragment();
SD.getFragmentList().insert(it2, DF);
// Update the data fragments layout data.
DF->setParent(IF->getParent());
DF->setAtom(IF->getAtom());
DF->setLayoutOrder(IF->getLayoutOrder());
Layout.FragmentReplaced(IF, DF);
// Copy in the data and the fixups.
DF->getContents().append(IF->getCode().begin(), IF->getCode().end());
for (unsigned i = 0, e = IF->getFixups().size(); i != e; ++i)
DF->getFixups().push_back(IF->getFixups()[i]);
// Delete the instruction fragment and update the iterator.
SD.getFragmentList().erase(IF);
it2 = DF;
}
}
}
// Debugging methods
namespace llvm {
raw_ostream &operator<<(raw_ostream &OS, const MCFixup &AF) {
OS << "<MCFixup" << " Offset:" << AF.getOffset()
<< " Value:" << *AF.getValue()
<< " Kind:" << AF.getKind() << ">";
return OS;
}
}
void MCFragment::dump() {
raw_ostream &OS = llvm::errs();
OS << "<";
switch (getKind()) {
case MCFragment::FT_Align: OS << "MCAlignFragment"; break;
case MCFragment::FT_Data: OS << "MCDataFragment"; break;
case MCFragment::FT_Fill: OS << "MCFillFragment"; break;
case MCFragment::FT_Inst: OS << "MCInstFragment"; break;
case MCFragment::FT_Org: OS << "MCOrgFragment"; break;
case MCFragment::FT_Dwarf: OS << "MCDwarfFragment"; break;
case MCFragment::FT_LEB: OS << "MCLEBFragment"; break;
}
OS << "<MCFragment " << (void*) this << " LayoutOrder:" << LayoutOrder
<< " Offset:" << Offset << " EffectiveSize:" << EffectiveSize << ">";
switch (getKind()) {
case MCFragment::FT_Align: {
const MCAlignFragment *AF = cast<MCAlignFragment>(this);
if (AF->hasEmitNops())
OS << " (emit nops)";
if (AF->hasOnlyAlignAddress())
OS << " (only align section)";
OS << "\n ";
OS << " Alignment:" << AF->getAlignment()
<< " Value:" << AF->getValue() << " ValueSize:" << AF->getValueSize()
<< " MaxBytesToEmit:" << AF->getMaxBytesToEmit() << ">";
break;
}
case MCFragment::FT_Data: {
const MCDataFragment *DF = cast<MCDataFragment>(this);
OS << "\n ";
OS << " Contents:[";
const SmallVectorImpl<char> &Contents = DF->getContents();
for (unsigned i = 0, e = Contents.size(); i != e; ++i) {
if (i) OS << ",";
OS << hexdigit((Contents[i] >> 4) & 0xF) << hexdigit(Contents[i] & 0xF);
}
OS << "] (" << Contents.size() << " bytes)";
if (!DF->getFixups().empty()) {
OS << ",\n ";
OS << " Fixups:[";
for (MCDataFragment::const_fixup_iterator it = DF->fixup_begin(),
ie = DF->fixup_end(); it != ie; ++it) {
if (it != DF->fixup_begin()) OS << ",\n ";
OS << *it;
}
OS << "]";
}
break;
}
case MCFragment::FT_Fill: {
const MCFillFragment *FF = cast<MCFillFragment>(this);
OS << " Value:" << FF->getValue() << " ValueSize:" << FF->getValueSize()
<< " Size:" << FF->getSize();
break;
}
case MCFragment::FT_Inst: {
const MCInstFragment *IF = cast<MCInstFragment>(this);
OS << "\n ";
OS << " Inst:";
IF->getInst().dump_pretty(OS);
break;
}
case MCFragment::FT_Org: {
const MCOrgFragment *OF = cast<MCOrgFragment>(this);
OS << "\n ";
OS << " Offset:" << OF->getOffset() << " Value:" << OF->getValue();
break;
}
case MCFragment::FT_Dwarf: {
const MCDwarfLineAddrFragment *OF = cast<MCDwarfLineAddrFragment>(this);
OS << "\n ";
OS << " AddrDelta:" << OF->getAddrDelta()
<< " LineDelta:" << OF->getLineDelta();
break;
}
case MCFragment::FT_LEB: {
const MCLEBFragment *LF = cast<MCLEBFragment>(this);
OS << "\n ";
OS << " Value:" << LF->getValue() << " Signed:" << LF->isSigned();
break;
}
}
OS << ">";
}
void MCSectionData::dump() {
raw_ostream &OS = llvm::errs();
OS << "<MCSectionData";
OS << " Alignment:" << getAlignment() << " Address:" << Address
<< " Fragments:[\n ";
for (iterator it = begin(), ie = end(); it != ie; ++it) {
if (it != begin()) OS << ",\n ";
it->dump();
}
OS << "]>";
}
void MCSymbolData::dump() {
raw_ostream &OS = llvm::errs();
OS << "<MCSymbolData Symbol:" << getSymbol()
<< " Fragment:" << getFragment() << " Offset:" << getOffset()
<< " Flags:" << getFlags() << " Index:" << getIndex();
if (isCommon())
OS << " (common, size:" << getCommonSize()
<< " align: " << getCommonAlignment() << ")";
if (isExternal())
OS << " (external)";
if (isPrivateExtern())
OS << " (private extern)";
OS << ">";
}
void MCAssembler::dump() {
raw_ostream &OS = llvm::errs();
OS << "<MCAssembler\n";
OS << " Sections:[\n ";
for (iterator it = begin(), ie = end(); it != ie; ++it) {
if (it != begin()) OS << ",\n ";
it->dump();
}
OS << "],\n";
OS << " Symbols:[";
for (symbol_iterator it = symbol_begin(), ie = symbol_end(); it != ie; ++it) {
if (it != symbol_begin()) OS << ",\n ";
it->dump();
}
OS << "]>\n";
}
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