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llvm-project/llvm/lib/MC/MCELFStreamer.cpp
Fangrui Song eea7d32bd2 [MC] Move fixSymbolsInTLSFixups to ELFObjectWriter 
so that we only need to do it once during recordRelocation. In the
future, we should change fixSymbolsInTLSFixups to apply to MCValue
instead of MCExpr, similar to GNU assembler.
2025-03-12 19:49:52 -07:00

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//===- lib/MC/MCELFStreamer.cpp - ELF Object Output -----------------------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file assembles .s files and emits ELF .o object files.
//
//===----------------------------------------------------------------------===//
#include "llvm/MC/MCELFStreamer.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/BinaryFormat/ELF.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/MCELFObjectWriter.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCFixup.h"
#include "llvm/MC/MCFragment.h"
#include "llvm/MC/MCObjectFileInfo.h"
#include "llvm/MC/MCObjectWriter.h"
#include "llvm/MC/MCSection.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCSymbolELF.h"
#include "llvm/MC/TargetRegistry.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/LEB128.h"
#include <cassert>
#include <cstdint>
using namespace llvm;
MCELFStreamer::MCELFStreamer(MCContext &Context,
std::unique_ptr<MCAsmBackend> TAB,
std::unique_ptr<MCObjectWriter> OW,
std::unique_ptr<MCCodeEmitter> Emitter)
: MCObjectStreamer(Context, std::move(TAB), std::move(OW),
std::move(Emitter)) {}
ELFObjectWriter &MCELFStreamer::getWriter() {
return static_cast<ELFObjectWriter &>(getAssembler().getWriter());
}
bool MCELFStreamer::isBundleLocked() const {
return getCurrentSectionOnly()->isBundleLocked();
}
void MCELFStreamer::initSections(bool NoExecStack, const MCSubtargetInfo &STI) {
MCContext &Ctx = getContext();
switchSection(Ctx.getObjectFileInfo()->getTextSection());
emitCodeAlignment(Align(Ctx.getObjectFileInfo()->getTextSectionAlignment()),
&STI);
if (NoExecStack)
switchSection(Ctx.getAsmInfo()->getNonexecutableStackSection(Ctx));
}
void MCELFStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
auto *Symbol = cast<MCSymbolELF>(S);
MCObjectStreamer::emitLabel(Symbol, Loc);
const MCSectionELF &Section =
static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
if (Section.getFlags() & ELF::SHF_TLS)
Symbol->setType(ELF::STT_TLS);
}
void MCELFStreamer::emitLabelAtPos(MCSymbol *S, SMLoc Loc, MCDataFragment &F,
uint64_t Offset) {
auto *Symbol = cast<MCSymbolELF>(S);
MCObjectStreamer::emitLabelAtPos(Symbol, Loc, F, Offset);
const MCSectionELF &Section =
static_cast<const MCSectionELF &>(*getCurrentSectionOnly());
if (Section.getFlags() & ELF::SHF_TLS)
Symbol->setType(ELF::STT_TLS);
}
void MCELFStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
// Let the target do whatever target specific stuff it needs to do.
getAssembler().getBackend().handleAssemblerFlag(Flag);
}
// If bundle alignment is used and there are any instructions in the section, it
// needs to be aligned to at least the bundle size.
static void setSectionAlignmentForBundling(const MCAssembler &Assembler,
MCSection *Section) {
if (Assembler.isBundlingEnabled() && Section->hasInstructions())
Section->ensureMinAlignment(Align(Assembler.getBundleAlignSize()));
}
void MCELFStreamer::changeSection(MCSection *Section, uint32_t Subsection) {
MCAssembler &Asm = getAssembler();
if (auto *F = getCurrentFragment()) {
if (isBundleLocked())
report_fatal_error("Unterminated .bundle_lock when changing a section");
// Ensure the previous section gets aligned if necessary.
setSectionAlignmentForBundling(Asm, F->getParent());
}
auto *SectionELF = static_cast<const MCSectionELF *>(Section);
const MCSymbol *Grp = SectionELF->getGroup();
if (Grp)
Asm.registerSymbol(*Grp);
if (SectionELF->getFlags() & ELF::SHF_GNU_RETAIN)
getWriter().markGnuAbi();
changeSectionImpl(Section, Subsection);
Asm.registerSymbol(*Section->getBeginSymbol());
}
void MCELFStreamer::emitWeakReference(MCSymbol *Alias, const MCSymbol *Symbol) {
getAssembler().registerSymbol(*Symbol);
const MCExpr *Value = MCSymbolRefExpr::create(
Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext());
Alias->setVariableValue(Value);
}
// When GNU as encounters more than one .type declaration for an object it seems
// to use a mechanism similar to the one below to decide which type is actually
// used in the object file. The greater of T1 and T2 is selected based on the
// following ordering:
// STT_NOTYPE < STT_OBJECT < STT_FUNC < STT_GNU_IFUNC < STT_TLS < anything else
// If neither T1 < T2 nor T2 < T1 according to this ordering, use T2 (the user
// provided type).
static unsigned CombineSymbolTypes(unsigned T1, unsigned T2) {
for (unsigned Type : {ELF::STT_NOTYPE, ELF::STT_OBJECT, ELF::STT_FUNC,
ELF::STT_GNU_IFUNC, ELF::STT_TLS}) {
if (T1 == Type)
return T2;
if (T2 == Type)
return T1;
}
return T2;
}
bool MCELFStreamer::emitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
auto *Symbol = cast<MCSymbolELF>(S);
// Adding a symbol attribute always introduces the symbol, note that an
// important side effect of calling registerSymbol here is to register
// the symbol with the assembler.
getAssembler().registerSymbol(*Symbol);
// The implementation of symbol attributes is designed to match 'as', but it
// leaves much to desired. It doesn't really make sense to arbitrarily add and
// remove flags, but 'as' allows this (in particular, see .desc).
//
// In the future it might be worth trying to make these operations more well
// defined.
switch (Attribute) {
case MCSA_Cold:
case MCSA_Extern:
case MCSA_LazyReference:
case MCSA_Reference:
case MCSA_SymbolResolver:
case MCSA_PrivateExtern:
case MCSA_WeakDefinition:
case MCSA_WeakDefAutoPrivate:
case MCSA_Invalid:
case MCSA_IndirectSymbol:
case MCSA_Exported:
case MCSA_WeakAntiDep:
return false;
case MCSA_NoDeadStrip:
// Ignore for now.
break;
case MCSA_ELF_TypeGnuUniqueObject:
Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
Symbol->setBinding(ELF::STB_GNU_UNIQUE);
getWriter().markGnuAbi();
break;
case MCSA_Global:
// For `.weak x; .global x`, GNU as sets the binding to STB_WEAK while we
// traditionally set the binding to STB_GLOBAL. This is error-prone, so we
// error on such cases. Note, we also disallow changed binding from .local.
if (Symbol->isBindingSet() && Symbol->getBinding() != ELF::STB_GLOBAL)
getContext().reportError(getStartTokLoc(),
Symbol->getName() +
" changed binding to STB_GLOBAL");
Symbol->setBinding(ELF::STB_GLOBAL);
break;
case MCSA_WeakReference:
case MCSA_Weak:
// For `.global x; .weak x`, both MC and GNU as set the binding to STB_WEAK.
// We emit a warning for now but may switch to an error in the future.
if (Symbol->isBindingSet() && Symbol->getBinding() != ELF::STB_WEAK)
getContext().reportWarning(
getStartTokLoc(), Symbol->getName() + " changed binding to STB_WEAK");
Symbol->setBinding(ELF::STB_WEAK);
break;
case MCSA_Local:
if (Symbol->isBindingSet() && Symbol->getBinding() != ELF::STB_LOCAL)
getContext().reportError(getStartTokLoc(),
Symbol->getName() +
" changed binding to STB_LOCAL");
Symbol->setBinding(ELF::STB_LOCAL);
break;
case MCSA_ELF_TypeFunction:
Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_FUNC));
break;
case MCSA_ELF_TypeIndFunction:
Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_GNU_IFUNC));
getWriter().markGnuAbi();
break;
case MCSA_ELF_TypeObject:
Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
break;
case MCSA_ELF_TypeTLS:
Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_TLS));
break;
case MCSA_ELF_TypeCommon:
// TODO: Emit these as a common symbol.
Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_OBJECT));
break;
case MCSA_ELF_TypeNoType:
Symbol->setType(CombineSymbolTypes(Symbol->getType(), ELF::STT_NOTYPE));
break;
case MCSA_Protected:
Symbol->setVisibility(ELF::STV_PROTECTED);
break;
case MCSA_Memtag:
Symbol->setMemtag(true);
break;
case MCSA_Hidden:
Symbol->setVisibility(ELF::STV_HIDDEN);
break;
case MCSA_Internal:
Symbol->setVisibility(ELF::STV_INTERNAL);
break;
case MCSA_AltEntry:
llvm_unreachable("ELF doesn't support the .alt_entry attribute");
case MCSA_LGlobal:
llvm_unreachable("ELF doesn't support the .lglobl attribute");
}
return true;
}
void MCELFStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
Align ByteAlignment) {
auto *Symbol = cast<MCSymbolELF>(S);
getAssembler().registerSymbol(*Symbol);
if (!Symbol->isBindingSet())
Symbol->setBinding(ELF::STB_GLOBAL);
Symbol->setType(ELF::STT_OBJECT);
if (Symbol->getBinding() == ELF::STB_LOCAL) {
MCSection &Section = *getAssembler().getContext().getELFSection(
".bss", ELF::SHT_NOBITS, ELF::SHF_WRITE | ELF::SHF_ALLOC);
MCSectionSubPair P = getCurrentSection();
switchSection(&Section);
emitValueToAlignment(ByteAlignment, 0, 1, 0);
emitLabel(Symbol);
emitZeros(Size);
switchSection(P.first, P.second);
} else {
if (Symbol->declareCommon(Size, ByteAlignment))
report_fatal_error(Twine("Symbol: ") + Symbol->getName() +
" redeclared as different type");
}
cast<MCSymbolELF>(Symbol)
->setSize(MCConstantExpr::create(Size, getContext()));
}
void MCELFStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
cast<MCSymbolELF>(Symbol)->setSize(Value);
}
void MCELFStreamer::emitELFSymverDirective(const MCSymbol *OriginalSym,
StringRef Name,
bool KeepOriginalSym) {
getWriter().Symvers.push_back(ELFObjectWriter::Symver{
getStartTokLoc(), OriginalSym, Name, KeepOriginalSym});
}
void MCELFStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
Align ByteAlignment) {
auto *Symbol = cast<MCSymbolELF>(S);
// FIXME: Should this be caught and done earlier?
getAssembler().registerSymbol(*Symbol);
Symbol->setBinding(ELF::STB_LOCAL);
emitCommonSymbol(Symbol, Size, ByteAlignment);
}
void MCELFStreamer::emitValueImpl(const MCExpr *Value, unsigned Size,
SMLoc Loc) {
if (isBundleLocked())
report_fatal_error("Emitting values inside a locked bundle is forbidden");
MCObjectStreamer::emitValueImpl(Value, Size, Loc);
}
void MCELFStreamer::emitValueToAlignment(Align Alignment, int64_t Value,
unsigned ValueSize,
unsigned MaxBytesToEmit) {
if (isBundleLocked())
report_fatal_error("Emitting values inside a locked bundle is forbidden");
MCObjectStreamer::emitValueToAlignment(Alignment, Value, ValueSize,
MaxBytesToEmit);
}
void MCELFStreamer::emitCGProfileEntry(const MCSymbolRefExpr *From,
const MCSymbolRefExpr *To,
uint64_t Count) {
getWriter().getCGProfile().push_back({From, To, Count});
}
void MCELFStreamer::emitIdent(StringRef IdentString) {
MCSection *Comment = getAssembler().getContext().getELFSection(
".comment", ELF::SHT_PROGBITS, ELF::SHF_MERGE | ELF::SHF_STRINGS, 1);
pushSection();
switchSection(Comment);
if (!SeenIdent) {
emitInt8(0);
SeenIdent = true;
}
emitBytes(IdentString);
emitInt8(0);
popSection();
}
void MCELFStreamer::finalizeCGProfileEntry(const MCSymbolRefExpr *&SRE,
uint64_t Offset) {
const MCSymbol *S = &SRE->getSymbol();
if (S->isTemporary()) {
if (!S->isInSection()) {
getContext().reportError(
SRE->getLoc(), Twine("Reference to undefined temporary symbol ") +
"`" + S->getName() + "`");
return;
}
S = S->getSection().getBeginSymbol();
S->setUsedInReloc();
SRE = MCSymbolRefExpr::create(S, getContext(), SRE->getLoc());
}
const MCConstantExpr *MCOffset = MCConstantExpr::create(Offset, getContext());
if (std::optional<std::pair<bool, std::string>> Err =
MCObjectStreamer::emitRelocDirective(
*MCOffset, "BFD_RELOC_NONE", SRE, SRE->getLoc(),
*getContext().getSubtargetInfo()))
report_fatal_error("Relocation for CG Profile could not be created: " +
Twine(Err->second));
}
void MCELFStreamer::finalizeCGProfile() {
ELFObjectWriter &W = getWriter();
if (W.getCGProfile().empty())
return;
MCSection *CGProfile = getAssembler().getContext().getELFSection(
".llvm.call-graph-profile", ELF::SHT_LLVM_CALL_GRAPH_PROFILE,
ELF::SHF_EXCLUDE, /*sizeof(Elf_CGProfile_Impl<>)=*/8);
pushSection();
switchSection(CGProfile);
uint64_t Offset = 0;
for (auto &E : W.getCGProfile()) {
finalizeCGProfileEntry(E.From, Offset);
finalizeCGProfileEntry(E.To, Offset);
emitIntValue(E.Count, sizeof(uint64_t));
Offset += sizeof(uint64_t);
}
popSection();
}
// A fragment can only have one Subtarget, and when bundling is enabled we
// sometimes need to use the same fragment. We give an error if there
// are conflicting Subtargets.
static void CheckBundleSubtargets(const MCSubtargetInfo *OldSTI,
const MCSubtargetInfo *NewSTI) {
if (OldSTI && NewSTI && OldSTI != NewSTI)
report_fatal_error("A Bundle can only have one Subtarget.");
}
void MCELFStreamer::emitInstToData(const MCInst &Inst,
const MCSubtargetInfo &STI) {
MCAssembler &Assembler = getAssembler();
// There are several possibilities here:
//
// If bundling is disabled, append the encoded instruction to the current data
// fragment (or create a new such fragment if the current fragment is not a
// data fragment, or the Subtarget has changed).
//
// If bundling is enabled:
// - If we're not in a bundle-locked group, emit the instruction into a
// fragment of its own.
// - If we're in a bundle-locked group, append the instruction to the current
// data fragment because we want all the instructions in a group to get into
// the same fragment. Be careful not to do that for the first instruction in
// the group, though.
MCDataFragment *DF;
if (Assembler.isBundlingEnabled()) {
MCSection &Sec = *getCurrentSectionOnly();
if (isBundleLocked() && !Sec.isBundleGroupBeforeFirstInst()) {
// If we are bundle-locked, we re-use the current fragment.
// The bundle-locking directive ensures this is a new data fragment.
DF = cast<MCDataFragment>(getCurrentFragment());
CheckBundleSubtargets(DF->getSubtargetInfo(), &STI);
} else {
DF = getContext().allocFragment<MCDataFragment>();
insert(DF);
}
if (Sec.getBundleLockState() == MCSection::BundleLockedAlignToEnd) {
// If this fragment is for a group marked "align_to_end", set a flag
// in the fragment. This can happen after the fragment has already been
// created if there are nested bundle_align groups and an inner one
// is the one marked align_to_end.
DF->setAlignToBundleEnd(true);
}
// We're now emitting an instruction in a bundle group, so this flag has
// to be turned off.
Sec.setBundleGroupBeforeFirstInst(false);
} else {
DF = getOrCreateDataFragment(&STI);
}
// Emit instruction directly into data fragment.
size_t FixupStartIndex = DF->getFixups().size();
size_t CodeOffset = DF->getContents().size();
Assembler.getEmitter().encodeInstruction(Inst, DF->getContents(),
DF->getFixups(), STI);
auto Fixups = MutableArrayRef(DF->getFixups()).slice(FixupStartIndex);
for (auto &Fixup : Fixups)
Fixup.setOffset(Fixup.getOffset() + CodeOffset);
DF->setHasInstructions(STI);
if (!Fixups.empty() && Fixups.back().getTargetKind() ==
getAssembler().getBackend().RelaxFixupKind)
DF->setLinkerRelaxable();
}
void MCELFStreamer::emitBundleAlignMode(Align Alignment) {
assert(Log2(Alignment) <= 30 && "Invalid bundle alignment");
MCAssembler &Assembler = getAssembler();
if (Alignment > 1 && (Assembler.getBundleAlignSize() == 0 ||
Assembler.getBundleAlignSize() == Alignment.value()))
Assembler.setBundleAlignSize(Alignment.value());
else
report_fatal_error(".bundle_align_mode cannot be changed once set");
}
void MCELFStreamer::emitBundleLock(bool AlignToEnd) {
MCSection &Sec = *getCurrentSectionOnly();
if (!getAssembler().isBundlingEnabled())
report_fatal_error(".bundle_lock forbidden when bundling is disabled");
if (!isBundleLocked())
Sec.setBundleGroupBeforeFirstInst(true);
Sec.setBundleLockState(AlignToEnd ? MCSection::BundleLockedAlignToEnd
: MCSection::BundleLocked);
}
void MCELFStreamer::emitBundleUnlock() {
MCSection &Sec = *getCurrentSectionOnly();
if (!getAssembler().isBundlingEnabled())
report_fatal_error(".bundle_unlock forbidden when bundling is disabled");
else if (!isBundleLocked())
report_fatal_error(".bundle_unlock without matching lock");
else if (Sec.isBundleGroupBeforeFirstInst())
report_fatal_error("Empty bundle-locked group is forbidden");
Sec.setBundleLockState(MCSection::NotBundleLocked);
}
void MCELFStreamer::finishImpl() {
// Emit the .gnu attributes section if any attributes have been added.
if (!GNUAttributes.empty()) {
MCSection *DummyAttributeSection = nullptr;
createAttributesSection("gnu", ".gnu.attributes", ELF::SHT_GNU_ATTRIBUTES,
DummyAttributeSection, GNUAttributes);
}
// Ensure the last section gets aligned if necessary.
if (MCFragment *F = getCurrentFragment())
setSectionAlignmentForBundling(getAssembler(), F->getParent());
finalizeCGProfile();
emitFrames(nullptr);
this->MCObjectStreamer::finishImpl();
}
void MCELFStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
llvm_unreachable("ELF doesn't support this directive");
}
void MCELFStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
uint64_t Size, Align ByteAlignment,
SMLoc Loc) {
llvm_unreachable("ELF doesn't support this directive");
}
void MCELFStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
uint64_t Size, Align ByteAlignment) {
llvm_unreachable("ELF doesn't support this directive");
}
void MCELFStreamer::setAttributeItem(unsigned Attribute, unsigned Value,
bool OverwriteExisting) {
// Look for existing attribute item
if (AttributeItem *Item = getAttributeItem(Attribute)) {
if (!OverwriteExisting)
return;
Item->Type = AttributeItem::NumericAttribute;
Item->IntValue = Value;
return;
}
// Create new attribute item
AttributeItem Item = {AttributeItem::NumericAttribute, Attribute, Value,
std::string(StringRef(""))};
Contents.push_back(Item);
}
void MCELFStreamer::setAttributeItem(unsigned Attribute, StringRef Value,
bool OverwriteExisting) {
// Look for existing attribute item
if (AttributeItem *Item = getAttributeItem(Attribute)) {
if (!OverwriteExisting)
return;
Item->Type = AttributeItem::TextAttribute;
Item->StringValue = std::string(Value);
return;
}
// Create new attribute item
AttributeItem Item = {AttributeItem::TextAttribute, Attribute, 0,
std::string(Value)};
Contents.push_back(Item);
}
void MCELFStreamer::setAttributeItems(unsigned Attribute, unsigned IntValue,
StringRef StringValue,
bool OverwriteExisting) {
// Look for existing attribute item
if (AttributeItem *Item = getAttributeItem(Attribute)) {
if (!OverwriteExisting)
return;
Item->Type = AttributeItem::NumericAndTextAttributes;
Item->IntValue = IntValue;
Item->StringValue = std::string(StringValue);
return;
}
// Create new attribute item
AttributeItem Item = {AttributeItem::NumericAndTextAttributes, Attribute,
IntValue, std::string(StringValue)};
Contents.push_back(Item);
}
MCELFStreamer::AttributeItem *
MCELFStreamer::getAttributeItem(unsigned Attribute) {
for (AttributeItem &Item : Contents)
if (Item.Tag == Attribute)
return &Item;
return nullptr;
}
size_t MCELFStreamer::calculateContentSize(
SmallVector<AttributeItem, 64> &AttrsVec) const {
size_t Result = 0;
for (const AttributeItem &Item : AttrsVec) {
switch (Item.Type) {
case AttributeItem::HiddenAttribute:
break;
case AttributeItem::NumericAttribute:
Result += getULEB128Size(Item.Tag);
Result += getULEB128Size(Item.IntValue);
break;
case AttributeItem::TextAttribute:
Result += getULEB128Size(Item.Tag);
Result += Item.StringValue.size() + 1; // string + '\0'
break;
case AttributeItem::NumericAndTextAttributes:
Result += getULEB128Size(Item.Tag);
Result += getULEB128Size(Item.IntValue);
Result += Item.StringValue.size() + 1; // string + '\0';
break;
}
}
return Result;
}
void MCELFStreamer::createAttributesSection(
StringRef Vendor, const Twine &Section, unsigned Type,
MCSection *&AttributeSection, SmallVector<AttributeItem, 64> &AttrsVec) {
// <format-version>
// [ <section-length> "vendor-name"
// [ <file-tag> <size> <attribute>*
// | <section-tag> <size> <section-number>* 0 <attribute>*
// | <symbol-tag> <size> <symbol-number>* 0 <attribute>*
// ]+
// ]*
// Switch section to AttributeSection or get/create the section.
if (AttributeSection) {
switchSection(AttributeSection);
} else {
AttributeSection = getContext().getELFSection(Section, Type, 0);
switchSection(AttributeSection);
// Format version
emitInt8(0x41);
}
// Vendor size + Vendor name + '\0'
const size_t VendorHeaderSize = 4 + Vendor.size() + 1;
// Tag + Tag Size
const size_t TagHeaderSize = 1 + 4;
const size_t ContentsSize = calculateContentSize(AttrsVec);
emitInt32(VendorHeaderSize + TagHeaderSize + ContentsSize);
emitBytes(Vendor);
emitInt8(0); // '\0'
emitInt8(ARMBuildAttrs::File);
emitInt32(TagHeaderSize + ContentsSize);
// Size should have been accounted for already, now
// emit each field as its type (ULEB or String)
for (const AttributeItem &Item : AttrsVec) {
emitULEB128IntValue(Item.Tag);
switch (Item.Type) {
default:
llvm_unreachable("Invalid attribute type");
case AttributeItem::NumericAttribute:
emitULEB128IntValue(Item.IntValue);
break;
case AttributeItem::TextAttribute:
emitBytes(Item.StringValue);
emitInt8(0); // '\0'
break;
case AttributeItem::NumericAndTextAttributes:
emitULEB128IntValue(Item.IntValue);
emitBytes(Item.StringValue);
emitInt8(0); // '\0'
break;
}
}
AttrsVec.clear();
}
void MCELFStreamer::createAttributesWithSubsection(
MCSection *&AttributeSection, const Twine &Section, unsigned Type,
SmallVector<AttributeSubSection, 64> &SubSectionVec) {
// <format-version: 'A'>
// [ <uint32: subsection-length> NTBS: vendor-name
// <bytes: vendor-data>
// ]*
// vendor-data expends to:
// <uint8: optional> <uint8: parameter type> <attribute>*
if (0 == SubSectionVec.size()) {
return;
}
// Switch section to AttributeSection or get/create the section.
if (AttributeSection) {
switchSection(AttributeSection);
} else {
AttributeSection = getContext().getELFSection(Section, Type, 0);
switchSection(AttributeSection);
// Format version
emitInt8(0x41);
}
for (AttributeSubSection &SubSection : SubSectionVec) {
// subsection-length + vendor-name + '\0'
const size_t VendorHeaderSize = 4 + SubSection.VendorName.size() + 1;
// optional + parameter-type
const size_t VendorParameters = 1 + 1;
const size_t ContentsSize = calculateContentSize(SubSection.Content);
emitInt32(VendorHeaderSize + VendorParameters + ContentsSize);
emitBytes(SubSection.VendorName);
emitInt8(0); // '\0'
emitInt8(SubSection.IsOptional);
emitInt8(SubSection.ParameterType);
for (AttributeItem &Item : SubSection.Content) {
emitULEB128IntValue(Item.Tag);
switch (Item.Type) {
default:
assert(0 && "Invalid attribute type");
break;
case AttributeItem::NumericAttribute:
emitULEB128IntValue(Item.IntValue);
break;
case AttributeItem::TextAttribute:
emitBytes(Item.StringValue);
emitInt8(0); // '\0'
break;
case AttributeItem::NumericAndTextAttributes:
emitULEB128IntValue(Item.IntValue);
emitBytes(Item.StringValue);
emitInt8(0); // '\0'
break;
}
}
}
SubSectionVec.clear();
}
MCStreamer *llvm::createELFStreamer(MCContext &Context,
std::unique_ptr<MCAsmBackend> &&MAB,
std::unique_ptr<MCObjectWriter> &&OW,
std::unique_ptr<MCCodeEmitter> &&CE) {
MCELFStreamer *S =
new MCELFStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
return S;
}
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