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7cc33b4fa4
llvm-mirror/lib/MC/MCObjectStreamer.cpp
Reid Kleckner 7cc33b4fa4 [CodeView] Use assembler directives for line tables 
Adds a new family of .cv_* directives to LLVM's variant of GAS syntax:

- .cv_file: Similar to DWARF .file directives

- .cv_loc: Similar to the DWARF .loc directive, but starts with a
  function id. CodeView line tables are emitted by function instead of
  by compilation unit, so we needed an extra field to communicate this.
  Rather than overloading the .loc direction further, we decided it was
  better to have our own directive.

- .cv_stringtable: Emits the codeview string table at the current
  position. Currently this just contains the filenames as
  null-terminated strings.

- .cv_filechecksums: Emits the file checksum table for all files used
  with .cv_file so far. There is currently no support for emitting
  actual checksums, just filenames.

This moves the line table emission code down into the assembler.  This
is in preparation for implementing the inlined call site line table
format. The inline line table format encoding algorithm requires knowing
the absolute code offsets, so it must run after the assembler has laid
out the code.

David Majnemer collaborated on this patch.

llvm-svn: 259117
2016-01-28 23:31:52 +00:00

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//===- lib/MC/MCObjectStreamer.cpp - Object File MCStreamer Interface -----===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCObjectStreamer.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/MC/MCAsmBackend.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCAssembler.h"
#include "llvm/MC/MCCodeEmitter.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCDwarf.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/TargetRegistry.h"
using namespace llvm;
MCObjectStreamer::MCObjectStreamer(MCContext &Context, MCAsmBackend &TAB,
raw_pwrite_stream &OS,
MCCodeEmitter *Emitter_)
: MCStreamer(Context),
Assembler(new MCAssembler(Context, TAB, *Emitter_,
*TAB.createObjectWriter(OS))),
EmitEHFrame(true), EmitDebugFrame(false) {}
MCObjectStreamer::~MCObjectStreamer() {
delete &Assembler->getBackend();
delete &Assembler->getEmitter();
delete &Assembler->getWriter();
delete Assembler;
}
void MCObjectStreamer::flushPendingLabels(MCFragment *F, uint64_t FOffset) {
if (PendingLabels.empty())
return;
if (!F) {
F = new MCDataFragment();
MCSection *CurSection = getCurrentSectionOnly();
CurSection->getFragmentList().insert(CurInsertionPoint, F);
F->setParent(CurSection);
}
for (MCSymbol *Sym : PendingLabels) {
Sym->setFragment(F);
Sym->setOffset(FOffset);
}
PendingLabels.clear();
}
void MCObjectStreamer::emitAbsoluteSymbolDiff(const MCSymbol *Hi,
const MCSymbol *Lo,
unsigned Size) {
// If not assigned to the same (valid) fragment, fallback.
if (!Hi->getFragment() || Hi->getFragment() != Lo->getFragment() ||
Hi->isVariable() || Lo->isVariable()) {
MCStreamer::emitAbsoluteSymbolDiff(Hi, Lo, Size);
return;
}
EmitIntValue(Hi->getOffset() - Lo->getOffset(), Size);
}
void MCObjectStreamer::reset() {
if (Assembler)
Assembler->reset();
CurInsertionPoint = MCSection::iterator();
EmitEHFrame = true;
EmitDebugFrame = false;
PendingLabels.clear();
MCStreamer::reset();
}
void MCObjectStreamer::EmitFrames(MCAsmBackend *MAB) {
if (!getNumFrameInfos())
return;
if (EmitEHFrame)
MCDwarfFrameEmitter::Emit(*this, MAB, true);
if (EmitDebugFrame)
MCDwarfFrameEmitter::Emit(*this, MAB, false);
}
MCFragment *MCObjectStreamer::getCurrentFragment() const {
assert(getCurrentSectionOnly() && "No current section!");
if (CurInsertionPoint != getCurrentSectionOnly()->getFragmentList().begin())
return &*std::prev(CurInsertionPoint);
return nullptr;
}
MCDataFragment *MCObjectStreamer::getOrCreateDataFragment() {
MCDataFragment *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
// When bundling is enabled, we don't want to add data to a fragment that
// already has instructions (see MCELFStreamer::EmitInstToData for details)
if (!F || (Assembler->isBundlingEnabled() && !Assembler->getRelaxAll() &&
F->hasInstructions())) {
F = new MCDataFragment();
insert(F);
}
return F;
}
void MCObjectStreamer::visitUsedSymbol(const MCSymbol &Sym) {
Assembler->registerSymbol(Sym);
}
void MCObjectStreamer::EmitCFISections(bool EH, bool Debug) {
MCStreamer::EmitCFISections(EH, Debug);
EmitEHFrame = EH;
EmitDebugFrame = Debug;
}
void MCObjectStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
SMLoc Loc) {
MCStreamer::EmitValueImpl(Value, Size, Loc);
MCDataFragment *DF = getOrCreateDataFragment();
flushPendingLabels(DF, DF->getContents().size());
MCCVLineEntry::Make(this);
MCDwarfLineEntry::Make(this, getCurrentSection().first);
// Avoid fixups when possible.
int64_t AbsValue;
if (Value->evaluateAsAbsolute(AbsValue, getAssembler())) {
EmitIntValue(AbsValue, Size);
return;
}
DF->getFixups().push_back(
MCFixup::create(DF->getContents().size(), Value,
MCFixup::getKindForSize(Size, false), Loc));
DF->getContents().resize(DF->getContents().size() + Size, 0);
}
void MCObjectStreamer::EmitCFIStartProcImpl(MCDwarfFrameInfo &Frame) {
// We need to create a local symbol to avoid relocations.
Frame.Begin = getContext().createTempSymbol();
EmitLabel(Frame.Begin);
}
void MCObjectStreamer::EmitCFIEndProcImpl(MCDwarfFrameInfo &Frame) {
Frame.End = getContext().createTempSymbol();
EmitLabel(Frame.End);
}
void MCObjectStreamer::EmitLabel(MCSymbol *Symbol) {
MCStreamer::EmitLabel(Symbol);
getAssembler().registerSymbol(*Symbol);
// If there is a current fragment, mark the symbol as pointing into it.
// Otherwise queue the label and set its fragment pointer when we emit the
// next fragment.
auto *F = dyn_cast_or_null<MCDataFragment>(getCurrentFragment());
if (F && !(getAssembler().isBundlingEnabled() &&
getAssembler().getRelaxAll())) {
Symbol->setFragment(F);
Symbol->setOffset(F->getContents().size());
} else {
PendingLabels.push_back(Symbol);
}
}
void MCObjectStreamer::EmitULEB128Value(const MCExpr *Value) {
int64_t IntValue;
if (Value->evaluateAsAbsolute(IntValue, getAssembler())) {
EmitULEB128IntValue(IntValue);
return;
}
insert(new MCLEBFragment(*Value, false));
}
void MCObjectStreamer::EmitSLEB128Value(const MCExpr *Value) {
int64_t IntValue;
if (Value->evaluateAsAbsolute(IntValue, getAssembler())) {
EmitSLEB128IntValue(IntValue);
return;
}
insert(new MCLEBFragment(*Value, true));
}
void MCObjectStreamer::EmitWeakReference(MCSymbol *Alias,
const MCSymbol *Symbol) {
report_fatal_error("This file format doesn't support weak aliases.");
}
void MCObjectStreamer::ChangeSection(MCSection *Section,
const MCExpr *Subsection) {
changeSectionImpl(Section, Subsection);
}
bool MCObjectStreamer::changeSectionImpl(MCSection *Section,
const MCExpr *Subsection) {
assert(Section && "Cannot switch to a null section!");
flushPendingLabels(nullptr);
bool Created = getAssembler().registerSection(*Section);
int64_t IntSubsection = 0;
if (Subsection &&
!Subsection->evaluateAsAbsolute(IntSubsection, getAssembler()))
report_fatal_error("Cannot evaluate subsection number");
if (IntSubsection < 0 || IntSubsection > 8192)
report_fatal_error("Subsection number out of range");
CurInsertionPoint =
Section->getSubsectionInsertionPoint(unsigned(IntSubsection));
return Created;
}
void MCObjectStreamer::EmitAssignment(MCSymbol *Symbol, const MCExpr *Value) {
getAssembler().registerSymbol(*Symbol);
MCStreamer::EmitAssignment(Symbol, Value);
}
bool MCObjectStreamer::mayHaveInstructions(MCSection &Sec) const {
return Sec.hasInstructions();
}
void MCObjectStreamer::EmitInstruction(const MCInst &Inst,
const MCSubtargetInfo &STI) {
MCStreamer::EmitInstruction(Inst, STI);
MCSection *Sec = getCurrentSectionOnly();
Sec->setHasInstructions(true);
// Now that a machine instruction has been assembled into this section, make
// a line entry for any .loc directive that has been seen.
MCCVLineEntry::Make(this);
MCDwarfLineEntry::Make(this, getCurrentSection().first);
// If this instruction doesn't need relaxation, just emit it as data.
MCAssembler &Assembler = getAssembler();
if (!Assembler.getBackend().mayNeedRelaxation(Inst)) {
EmitInstToData(Inst, STI);
return;
}
// Otherwise, relax and emit it as data if either:
// - The RelaxAll flag was passed
// - Bundling is enabled and this instruction is inside a bundle-locked
// group. We want to emit all such instructions into the same data
// fragment.
if (Assembler.getRelaxAll() ||
(Assembler.isBundlingEnabled() && Sec->isBundleLocked())) {
MCInst Relaxed;
getAssembler().getBackend().relaxInstruction(Inst, Relaxed);
while (getAssembler().getBackend().mayNeedRelaxation(Relaxed))
getAssembler().getBackend().relaxInstruction(Relaxed, Relaxed);
EmitInstToData(Relaxed, STI);
return;
}
// Otherwise emit to a separate fragment.
EmitInstToFragment(Inst, STI);
}
void MCObjectStreamer::EmitInstToFragment(const MCInst &Inst,
const MCSubtargetInfo &STI) {
if (getAssembler().getRelaxAll() && getAssembler().isBundlingEnabled())
llvm_unreachable("All instructions should have already been relaxed");
// Always create a new, separate fragment here, because its size can change
// during relaxation.
MCRelaxableFragment *IF = new MCRelaxableFragment(Inst, STI);
insert(IF);
SmallString<128> Code;
raw_svector_ostream VecOS(Code);
getAssembler().getEmitter().encodeInstruction(Inst, VecOS, IF->getFixups(),
STI);
IF->getContents().append(Code.begin(), Code.end());
}
#ifndef NDEBUG
static const char *const BundlingNotImplementedMsg =
"Aligned bundling is not implemented for this object format";
#endif
void MCObjectStreamer::EmitBundleAlignMode(unsigned AlignPow2) {
llvm_unreachable(BundlingNotImplementedMsg);
}
void MCObjectStreamer::EmitBundleLock(bool AlignToEnd) {
llvm_unreachable(BundlingNotImplementedMsg);
}
void MCObjectStreamer::EmitBundleUnlock() {
llvm_unreachable(BundlingNotImplementedMsg);
}
void MCObjectStreamer::EmitDwarfLocDirective(unsigned FileNo, unsigned Line,
unsigned Column, unsigned Flags,
unsigned Isa,
unsigned Discriminator,
StringRef FileName) {
// In case we see two .loc directives in a row, make sure the
// first one gets a line entry.
MCDwarfLineEntry::Make(this, getCurrentSection().first);
this->MCStreamer::EmitDwarfLocDirective(FileNo, Line, Column, Flags,
Isa, Discriminator, FileName);
}
static const MCExpr *buildSymbolDiff(MCObjectStreamer &OS, const MCSymbol *A,
const MCSymbol *B) {
MCContext &Context = OS.getContext();
MCSymbolRefExpr::VariantKind Variant = MCSymbolRefExpr::VK_None;
const MCExpr *ARef = MCSymbolRefExpr::create(A, Variant, Context);
const MCExpr *BRef = MCSymbolRefExpr::create(B, Variant, Context);
const MCExpr *AddrDelta =
MCBinaryExpr::create(MCBinaryExpr::Sub, ARef, BRef, Context);
return AddrDelta;
}
static void emitDwarfSetLineAddr(MCObjectStreamer &OS,
MCDwarfLineTableParams Params,
int64_t LineDelta, const MCSymbol *Label,
int PointerSize) {
// emit the sequence to set the address
OS.EmitIntValue(dwarf::DW_LNS_extended_op, 1);
OS.EmitULEB128IntValue(PointerSize + 1);
OS.EmitIntValue(dwarf::DW_LNE_set_address, 1);
OS.EmitSymbolValue(Label, PointerSize);
// emit the sequence for the LineDelta (from 1) and a zero address delta.
MCDwarfLineAddr::Emit(&OS, Params, LineDelta, 0);
}
void MCObjectStreamer::EmitDwarfAdvanceLineAddr(int64_t LineDelta,
const MCSymbol *LastLabel,
const MCSymbol *Label,
unsigned PointerSize) {
if (!LastLabel) {
emitDwarfSetLineAddr(*this, Assembler->getDWARFLinetableParams(), LineDelta,
Label, PointerSize);
return;
}
const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
int64_t Res;
if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) {
MCDwarfLineAddr::Emit(this, Assembler->getDWARFLinetableParams(), LineDelta,
Res);
return;
}
insert(new MCDwarfLineAddrFragment(LineDelta, *AddrDelta));
}
void MCObjectStreamer::EmitDwarfAdvanceFrameAddr(const MCSymbol *LastLabel,
const MCSymbol *Label) {
const MCExpr *AddrDelta = buildSymbolDiff(*this, Label, LastLabel);
int64_t Res;
if (AddrDelta->evaluateAsAbsolute(Res, getAssembler())) {
MCDwarfFrameEmitter::EmitAdvanceLoc(*this, Res);
return;
}
insert(new MCDwarfCallFrameFragment(*AddrDelta));
}
void MCObjectStreamer::EmitCVLocDirective(unsigned FunctionId, unsigned FileNo,
unsigned Line, unsigned Column,
bool PrologueEnd, bool IsStmt,
StringRef FileName) {
// In case we see two .cv_loc directives in a row, make sure the
// first one gets a line entry.
MCCVLineEntry::Make(this);
this->MCStreamer::EmitCVLocDirective(FunctionId, FileNo, Line, Column,
PrologueEnd, IsStmt, FileName);
}
void MCObjectStreamer::EmitCVLinetableDirective(unsigned FunctionId,
const MCSymbol *Begin,
const MCSymbol *End) {
getContext().getCVContext().emitLineTableForFunction(*this, FunctionId, Begin,
End);
this->MCStreamer::EmitCVLinetableDirective(FunctionId, Begin, End);
}
void MCObjectStreamer::EmitCVStringTableDirective() {
getContext().getCVContext().emitStringTable(*this);
}
void MCObjectStreamer::EmitCVFileChecksumsDirective() {
getContext().getCVContext().emitFileChecksums(*this);
}
void MCObjectStreamer::EmitBytes(StringRef Data) {
MCCVLineEntry::Make(this);
MCDwarfLineEntry::Make(this, getCurrentSection().first);
MCDataFragment *DF = getOrCreateDataFragment();
flushPendingLabels(DF, DF->getContents().size());
DF->getContents().append(Data.begin(), Data.end());
}
void MCObjectStreamer::EmitValueToAlignment(unsigned ByteAlignment,
int64_t Value,
unsigned ValueSize,
unsigned MaxBytesToEmit) {
if (MaxBytesToEmit == 0)
MaxBytesToEmit = ByteAlignment;
insert(new MCAlignFragment(ByteAlignment, Value, ValueSize, MaxBytesToEmit));
// Update the maximum alignment on the current section if necessary.
MCSection *CurSec = getCurrentSection().first;
if (ByteAlignment > CurSec->getAlignment())
CurSec->setAlignment(ByteAlignment);
}
void MCObjectStreamer::EmitCodeAlignment(unsigned ByteAlignment,
unsigned MaxBytesToEmit) {
EmitValueToAlignment(ByteAlignment, 0, 1, MaxBytesToEmit);
cast<MCAlignFragment>(getCurrentFragment())->setEmitNops(true);
}
void MCObjectStreamer::emitValueToOffset(const MCExpr *Offset,
unsigned char Value) {
insert(new MCOrgFragment(*Offset, Value));
}
// Associate GPRel32 fixup with data and resize data area
void MCObjectStreamer::EmitGPRel32Value(const MCExpr *Value) {
MCDataFragment *DF = getOrCreateDataFragment();
flushPendingLabels(DF, DF->getContents().size());
DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
Value, FK_GPRel_4));
DF->getContents().resize(DF->getContents().size() + 4, 0);
}
// Associate GPRel32 fixup with data and resize data area
void MCObjectStreamer::EmitGPRel64Value(const MCExpr *Value) {
MCDataFragment *DF = getOrCreateDataFragment();
flushPendingLabels(DF, DF->getContents().size());
DF->getFixups().push_back(MCFixup::create(DF->getContents().size(),
Value, FK_GPRel_4));
DF->getContents().resize(DF->getContents().size() + 8, 0);
}
bool MCObjectStreamer::EmitRelocDirective(const MCExpr &Offset, StringRef Name,
const MCExpr *Expr, SMLoc Loc) {
int64_t OffsetValue;
if (!Offset.evaluateAsAbsolute(OffsetValue))
llvm_unreachable("Offset is not absolute");
if (OffsetValue < 0)
llvm_unreachable("Offset is negative");
MCDataFragment *DF = getOrCreateDataFragment();
flushPendingLabels(DF, DF->getContents().size());
Optional<MCFixupKind> MaybeKind = Assembler->getBackend().getFixupKind(Name);
if (!MaybeKind.hasValue())
return true;
MCFixupKind Kind = *MaybeKind;
if (Expr == nullptr)
Expr =
MCSymbolRefExpr::create(getContext().createTempSymbol(), getContext());
DF->getFixups().push_back(MCFixup::create(OffsetValue, Expr, Kind, Loc));
return false;
}
void MCObjectStreamer::EmitFill(uint64_t NumBytes, uint8_t FillValue) {
const MCSection *Sec = getCurrentSection().first;
(void)Sec;
assert(Sec && "need a section");
insert(new MCFillFragment(FillValue, NumBytes));
}
void MCObjectStreamer::FinishImpl() {
// If we are generating dwarf for assembly source files dump out the sections.
if (getContext().getGenDwarfForAssembly())
MCGenDwarfInfo::Emit(this);
// Dump out the dwarf file & directory tables and line tables.
MCDwarfLineTable::Emit(this, getAssembler().getDWARFLinetableParams());
flushPendingLabels(nullptr);
getAssembler().Finish();
}
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