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TargetLoweringObjectFileImpl.cpp
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TargetLoweringObjectFileImpl.cpp
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//===- llvm/CodeGen/TargetLoweringObjectFileImpl.cpp - Object File Info ---===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements classes used to handle lowerings specific to common
// object file formats.
//
//===----------------------------------------------------------------------===//
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineModuleInfoImpls.h"
#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
#include "llvm/IR/Comdat.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalAlias.h"
#include "llvm/IR/GlobalObject.h"
#include "llvm/IR/GlobalValue.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Metadata.h"
#include "llvm/IR/Module.h"
#include "llvm/IR/Type.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSectionCOFF.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSectionWasm.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/MC/MCSymbolELF.h"
#include "llvm/MC/MCValue.h"
#include "llvm/MC/SectionKind.h"
#include "llvm/ProfileData/InstrProf.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/COFF.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MachO.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include <cassert>
#include <string>
using namespace llvm;
using namespace dwarf;
//===----------------------------------------------------------------------===//
// ELF
//===----------------------------------------------------------------------===//
MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
const GlobalValue *GV, const TargetMachine &TM,
MachineModuleInfo *MMI) const {
unsigned Encoding = getPersonalityEncoding();
if ((Encoding & 0x80) == DW_EH_PE_indirect)
return getContext().getOrCreateSymbol(StringRef("DW.ref.") +
TM.getSymbol(GV)->getName());
if ((Encoding & 0x70) == DW_EH_PE_absptr)
return TM.getSymbol(GV);
report_fatal_error("We do not support this DWARF encoding yet!");
}
void TargetLoweringObjectFileELF::emitPersonalityValue(
MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
SmallString<64> NameData("DW.ref.");
NameData += Sym->getName();
MCSymbolELF *Label =
cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
MCSection *Sec = getContext().getELFNamedSection(".data", Label->getName(),
ELF::SHT_PROGBITS, Flags, 0);
unsigned Size = DL.getPointerSize();
Streamer.SwitchSection(Sec);
Streamer.EmitValueToAlignment(DL.getPointerABIAlignment());
Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
const MCExpr *E = MCConstantExpr::create(Size, getContext());
Streamer.emitELFSize(Label, E);
Streamer.EmitLabel(Label);
Streamer.EmitSymbolValue(Sym, Size);
}
const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
MachineModuleInfo *MMI, MCStreamer &Streamer) const {
if (Encoding & DW_EH_PE_indirect) {
MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", TM);
// Add information about the stub reference to ELFMMI so that the stub
// gets emitted by the asmprinter.
MachineModuleInfoImpl::StubValueTy &StubSym = ELFMMI.getGVStubEntry(SSym);
if (!StubSym.getPointer()) {
MCSymbol *Sym = TM.getSymbol(GV);
StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
}
return TargetLoweringObjectFile::
getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
Encoding & ~DW_EH_PE_indirect, Streamer);
}
return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
MMI, Streamer);
}
static SectionKind
getELFKindForNamedSection(StringRef Name, SectionKind K) {
// N.B.: The defaults used in here are no the same ones used in MC.
// We follow gcc, MC follows gas. For example, given ".section .eh_frame",
// both gas and MC will produce a section with no flags. Given
// section(".eh_frame") gcc will produce:
//
// .section .eh_frame,"a",@progbits
if (Name == getInstrProfSectionName(IPSK_covmap, Triple::ELF,
/*AddSegmentInfo=*/false))
return SectionKind::getMetadata();
if (Name.empty() || Name[0] != '.') return K;
// Some lame default implementation based on some magic section names.
if (Name == ".bss" ||
Name.startswith(".bss.") ||
Name.startswith(".gnu.linkonce.b.") ||
Name.startswith(".llvm.linkonce.b.") ||
Name == ".sbss" ||
Name.startswith(".sbss.") ||
Name.startswith(".gnu.linkonce.sb.") ||
Name.startswith(".llvm.linkonce.sb."))
return SectionKind::getBSS();
if (Name == ".tdata" ||
Name.startswith(".tdata.") ||
Name.startswith(".gnu.linkonce.td.") ||
Name.startswith(".llvm.linkonce.td."))
return SectionKind::getThreadData();
if (Name == ".tbss" ||
Name.startswith(".tbss.") ||
Name.startswith(".gnu.linkonce.tb.") ||
Name.startswith(".llvm.linkonce.tb."))
return SectionKind::getThreadBSS();
return K;
}
static unsigned getELFSectionType(StringRef Name, SectionKind K) {
// Use SHT_NOTE for section whose name starts with ".note" to allow
// emitting ELF notes from C variable declaration.
// See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77609
if (Name.startswith(".note"))
return ELF::SHT_NOTE;
if (Name == ".init_array")
return ELF::SHT_INIT_ARRAY;
if (Name == ".fini_array")
return ELF::SHT_FINI_ARRAY;
if (Name == ".preinit_array")
return ELF::SHT_PREINIT_ARRAY;
if (K.isBSS() || K.isThreadBSS())
return ELF::SHT_NOBITS;
return ELF::SHT_PROGBITS;
}
static unsigned getELFSectionFlags(SectionKind K) {
unsigned Flags = 0;
if (!K.isMetadata())
Flags |= ELF::SHF_ALLOC;
if (K.isText())
Flags |= ELF::SHF_EXECINSTR;
if (K.isExecuteOnly())
Flags |= ELF::SHF_ARM_PURECODE;
if (K.isWriteable())
Flags |= ELF::SHF_WRITE;
if (K.isThreadLocal())
Flags |= ELF::SHF_TLS;
if (K.isMergeableCString() || K.isMergeableConst())
Flags |= ELF::SHF_MERGE;
if (K.isMergeableCString())
Flags |= ELF::SHF_STRINGS;
return Flags;
}
static const Comdat *getELFComdat(const GlobalValue *GV) {
const Comdat *C = GV->getComdat();
if (!C)
return nullptr;
if (C->getSelectionKind() != Comdat::Any)
report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
C->getName() + "' cannot be lowered.");
return C;
}
static const MCSymbolELF *getAssociatedSymbol(const GlobalObject *GO,
const TargetMachine &TM) {
MDNode *MD = GO->getMetadata(LLVMContext::MD_associated);
if (!MD)
return nullptr;
auto *VM = dyn_cast<ValueAsMetadata>(MD->getOperand(0));
if (!VM)
report_fatal_error("MD_associated operand is not ValueAsMetadata");
GlobalObject *OtherGO = dyn_cast<GlobalObject>(VM->getValue());
return OtherGO ? dyn_cast<MCSymbolELF>(TM.getSymbol(OtherGO)) : nullptr;
}
MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
StringRef SectionName = GO->getSection();
// Infer section flags from the section name if we can.
Kind = getELFKindForNamedSection(SectionName, Kind);
StringRef Group = "";
unsigned Flags = getELFSectionFlags(Kind);
if (const Comdat *C = getELFComdat(GO)) {
Group = C->getName();
Flags |= ELF::SHF_GROUP;
}
// A section can have at most one associated section. Put each global with
// MD_associated in a unique section.
unsigned UniqueID = MCContext::GenericSectionID;
const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
if (AssociatedSymbol) {
UniqueID = NextUniqueID++;
Flags |= ELF::SHF_LINK_ORDER;
}
MCSectionELF *Section = getContext().getELFSection(
SectionName, getELFSectionType(SectionName, Kind), Flags,
/*EntrySize=*/0, Group, UniqueID, AssociatedSymbol);
// Make sure that we did not get some other section with incompatible sh_link.
// This should not be possible due to UniqueID code above.
assert(Section->getAssociatedSymbol() == AssociatedSymbol);
return Section;
}
/// Return the section prefix name used by options FunctionsSections and
/// DataSections.
static StringRef getSectionPrefixForGlobal(SectionKind Kind) {
if (Kind.isText())
return ".text";
if (Kind.isReadOnly())
return ".rodata";
if (Kind.isBSS())
return ".bss";
if (Kind.isThreadData())
return ".tdata";
if (Kind.isThreadBSS())
return ".tbss";
if (Kind.isData())
return ".data";
assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
return ".data.rel.ro";
}
static MCSectionELF *selectELFSectionForGlobal(
MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol) {
unsigned EntrySize = 0;
if (Kind.isMergeableCString()) {
if (Kind.isMergeable2ByteCString()) {
EntrySize = 2;
} else if (Kind.isMergeable4ByteCString()) {
EntrySize = 4;
} else {
EntrySize = 1;
assert(Kind.isMergeable1ByteCString() && "unknown string width");
}
} else if (Kind.isMergeableConst()) {
if (Kind.isMergeableConst4()) {
EntrySize = 4;
} else if (Kind.isMergeableConst8()) {
EntrySize = 8;
} else if (Kind.isMergeableConst16()) {
EntrySize = 16;
} else {
assert(Kind.isMergeableConst32() && "unknown data width");
EntrySize = 32;
}
}
StringRef Group = "";
if (const Comdat *C = getELFComdat(GO)) {
Flags |= ELF::SHF_GROUP;
Group = C->getName();
}
bool UniqueSectionNames = TM.getUniqueSectionNames();
SmallString<128> Name;
if (Kind.isMergeableCString()) {
// We also need alignment here.
// FIXME: this is getting the alignment of the character, not the
// alignment of the global!
unsigned Align = GO->getParent()->getDataLayout().getPreferredAlignment(
cast<GlobalVariable>(GO));
std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
Name = SizeSpec + utostr(Align);
} else if (Kind.isMergeableConst()) {
Name = ".rodata.cst";
Name += utostr(EntrySize);
} else {
Name = getSectionPrefixForGlobal(Kind);
}
if (const auto *F = dyn_cast<Function>(GO)) {
const auto &OptionalPrefix = F->getSectionPrefix();
if (OptionalPrefix)
Name += *OptionalPrefix;
}
if (EmitUniqueSection && UniqueSectionNames) {
Name.push_back('.');
TM.getNameWithPrefix(Name, GO, Mang, true);
}
unsigned UniqueID = MCContext::GenericSectionID;
if (EmitUniqueSection && !UniqueSectionNames) {
UniqueID = *NextUniqueID;
(*NextUniqueID)++;
}
// Use 0 as the unique ID for execute-only text
if (Kind.isExecuteOnly())
UniqueID = 0;
return Ctx.getELFSection(Name, getELFSectionType(Name, Kind), Flags,
EntrySize, Group, UniqueID, AssociatedSymbol);
}
MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
unsigned Flags = getELFSectionFlags(Kind);
// If we have -ffunction-section or -fdata-section then we should emit the
// global value to a uniqued section specifically for it.
bool EmitUniqueSection = false;
if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
if (Kind.isText())
EmitUniqueSection = TM.getFunctionSections();
else
EmitUniqueSection = TM.getDataSections();
}
EmitUniqueSection |= GO->hasComdat();
const MCSymbolELF *AssociatedSymbol = getAssociatedSymbol(GO, TM);
if (AssociatedSymbol) {
EmitUniqueSection = true;
Flags |= ELF::SHF_LINK_ORDER;
}
MCSectionELF *Section = selectELFSectionForGlobal(
getContext(), GO, Kind, getMangler(), TM, EmitUniqueSection, Flags,
&NextUniqueID, AssociatedSymbol);
assert(Section->getAssociatedSymbol() == AssociatedSymbol);
return Section;
}
MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
const Function &F, const TargetMachine &TM) const {
// If the function can be removed, produce a unique section so that
// the table doesn't prevent the removal.
const Comdat *C = F.getComdat();
bool EmitUniqueSection = TM.getFunctionSections() || C;
if (!EmitUniqueSection)
return ReadOnlySection;
return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
getMangler(), TM, EmitUniqueSection,
ELF::SHF_ALLOC, &NextUniqueID,
/* AssociatedSymbol */ nullptr);
}
bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
bool UsesLabelDifference, const Function &F) const {
// We can always create relative relocations, so use another section
// that can be marked non-executable.
return false;
}
/// Given a mergeable constant with the specified size and relocation
/// information, return a section that it should be placed in.
MCSection *TargetLoweringObjectFileELF::getSectionForConstant(
const DataLayout &DL, SectionKind Kind, const Constant *C,
unsigned &Align) const {
if (Kind.isMergeableConst4() && MergeableConst4Section)
return MergeableConst4Section;
if (Kind.isMergeableConst8() && MergeableConst8Section)
return MergeableConst8Section;
if (Kind.isMergeableConst16() && MergeableConst16Section)
return MergeableConst16Section;
if (Kind.isMergeableConst32() && MergeableConst32Section)
return MergeableConst32Section;
if (Kind.isReadOnly())
return ReadOnlySection;
assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
return DataRelROSection;
}
static MCSectionELF *getStaticStructorSection(MCContext &Ctx, bool UseInitArray,
bool IsCtor, unsigned Priority,
const MCSymbol *KeySym) {
std::string Name;
unsigned Type;
unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE;
StringRef COMDAT = KeySym ? KeySym->getName() : "";
if (KeySym)
Flags |= ELF::SHF_GROUP;
if (UseInitArray) {
if (IsCtor) {
Type = ELF::SHT_INIT_ARRAY;
Name = ".init_array";
} else {
Type = ELF::SHT_FINI_ARRAY;
Name = ".fini_array";
}
if (Priority != 65535) {
Name += '.';
Name += utostr(Priority);
}
} else {
// The default scheme is .ctor / .dtor, so we have to invert the priority
// numbering.
if (IsCtor)
Name = ".ctors";
else
Name = ".dtors";
if (Priority != 65535) {
Name += '.';
Name += utostr(65535 - Priority);
}
Type = ELF::SHT_PROGBITS;
}
return Ctx.getELFSection(Name, Type, Flags, 0, COMDAT);
}
MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
KeySym);
}
MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
KeySym);
}
const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
const GlobalValue *LHS, const GlobalValue *RHS,
const TargetMachine &TM) const {
// We may only use a PLT-relative relocation to refer to unnamed_addr
// functions.
if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
return nullptr;
// Basic sanity checks.
if (LHS->getType()->getPointerAddressSpace() != 0 ||
RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
RHS->isThreadLocal())
return nullptr;
return MCBinaryExpr::createSub(
MCSymbolRefExpr::create(TM.getSymbol(LHS), PLTRelativeVariantKind,
getContext()),
MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
}
void
TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
UseInitArray = UseInitArray_;
MCContext &Ctx = getContext();
if (!UseInitArray) {
StaticCtorSection = Ctx.getELFSection(".ctors", ELF::SHT_PROGBITS,
ELF::SHF_ALLOC | ELF::SHF_WRITE);
StaticDtorSection = Ctx.getELFSection(".dtors", ELF::SHT_PROGBITS,
ELF::SHF_ALLOC | ELF::SHF_WRITE);
return;
}
StaticCtorSection = Ctx.getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
ELF::SHF_WRITE | ELF::SHF_ALLOC);
StaticDtorSection = Ctx.getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
ELF::SHF_WRITE | ELF::SHF_ALLOC);
}
//===----------------------------------------------------------------------===//
// MachO
//===----------------------------------------------------------------------===//
TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
: TargetLoweringObjectFile() {
SupportIndirectSymViaGOTPCRel = true;
}
void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
const TargetMachine &TM) {
TargetLoweringObjectFile::Initialize(Ctx, TM);
if (TM.getRelocationModel() == Reloc::Static) {
StaticCtorSection = Ctx.getMachOSection("__TEXT", "__constructor", 0,
SectionKind::getData());
StaticDtorSection = Ctx.getMachOSection("__TEXT", "__destructor", 0,
SectionKind::getData());
} else {
StaticCtorSection = Ctx.getMachOSection("__DATA", "__mod_init_func",
MachO::S_MOD_INIT_FUNC_POINTERS,
SectionKind::getData());
StaticDtorSection = Ctx.getMachOSection("__DATA", "__mod_term_func",
MachO::S_MOD_TERM_FUNC_POINTERS,
SectionKind::getData());
}
}
/// emitModuleFlags - Perform code emission for module flags.
void TargetLoweringObjectFileMachO::emitModuleFlags(
MCStreamer &Streamer, ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
const TargetMachine &TM) const {
unsigned VersionVal = 0;
unsigned ImageInfoFlags = 0;
MDNode *LinkerOptions = nullptr;
StringRef SectionVal;
for (const auto &MFE : ModuleFlags) {
// Ignore flags with 'Require' behavior.
if (MFE.Behavior == Module::Require)
continue;
StringRef Key = MFE.Key->getString();
Metadata *Val = MFE.Val;
if (Key == "Objective-C Image Info Version") {
VersionVal = mdconst::extract<ConstantInt>(Val)->getZExtValue();
} else if (Key == "Objective-C Garbage Collection" ||
Key == "Objective-C GC Only" ||
Key == "Objective-C Is Simulated" ||
Key == "Objective-C Class Properties" ||
Key == "Objective-C Image Swift Version") {
ImageInfoFlags |= mdconst::extract<ConstantInt>(Val)->getZExtValue();
} else if (Key == "Objective-C Image Info Section") {
SectionVal = cast<MDString>(Val)->getString();
} else if (Key == "Linker Options") {
LinkerOptions = cast<MDNode>(Val);
}
}
// Emit the linker options if present.
if (LinkerOptions) {
for (const auto &Option : LinkerOptions->operands()) {
SmallVector<std::string, 4> StrOptions;
for (const auto &Piece : cast<MDNode>(Option)->operands())
StrOptions.push_back(cast<MDString>(Piece)->getString());
Streamer.EmitLinkerOptions(StrOptions);
}
}
// The section is mandatory. If we don't have it, then we don't have GC info.
if (SectionVal.empty()) return;
StringRef Segment, Section;
unsigned TAA = 0, StubSize = 0;
bool TAAParsed;
std::string ErrorCode =
MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
TAA, TAAParsed, StubSize);
if (!ErrorCode.empty())
// If invalid, report the error with report_fatal_error.
report_fatal_error("Invalid section specifier '" + Section + "': " +
ErrorCode + ".");
// Get the section.
MCSectionMachO *S = getContext().getMachOSection(
Segment, Section, TAA, StubSize, SectionKind::getData());
Streamer.SwitchSection(S);
Streamer.EmitLabel(getContext().
getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
Streamer.EmitIntValue(VersionVal, 4);
Streamer.EmitIntValue(ImageInfoFlags, 4);
Streamer.AddBlankLine();
}
static void checkMachOComdat(const GlobalValue *GV) {
const Comdat *C = GV->getComdat();
if (!C)
return;
report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
"' cannot be lowered.");
}
MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
// Parse the section specifier and create it if valid.
StringRef Segment, Section;
unsigned TAA = 0, StubSize = 0;
bool TAAParsed;
checkMachOComdat(GO);
std::string ErrorCode =
MCSectionMachO::ParseSectionSpecifier(GO->getSection(), Segment, Section,
TAA, TAAParsed, StubSize);
if (!ErrorCode.empty()) {
// If invalid, report the error with report_fatal_error.
report_fatal_error("Global variable '" + GO->getName() +
"' has an invalid section specifier '" +
GO->getSection() + "': " + ErrorCode + ".");
}
// Get the section.
MCSectionMachO *S =
getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
// If TAA wasn't set by ParseSectionSpecifier() above,
// use the value returned by getMachOSection() as a default.
if (!TAAParsed)
TAA = S->getTypeAndAttributes();
// Okay, now that we got the section, verify that the TAA & StubSize agree.
// If the user declared multiple globals with different section flags, we need
// to reject it here.
if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
// If invalid, report the error with report_fatal_error.
report_fatal_error("Global variable '" + GO->getName() +
"' section type or attributes does not match previous"
" section specifier");
}
return S;
}
MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
checkMachOComdat(GO);
// Handle thread local data.
if (Kind.isThreadBSS()) return TLSBSSSection;
if (Kind.isThreadData()) return TLSDataSection;
if (Kind.isText())
return GO->isWeakForLinker() ? TextCoalSection : TextSection;
// If this is weak/linkonce, put this in a coalescable section, either in text
// or data depending on if it is writable.
if (GO->isWeakForLinker()) {
if (Kind.isReadOnly())
return ConstTextCoalSection;
return DataCoalSection;
}
// FIXME: Alignment check should be handled by section classifier.
if (Kind.isMergeable1ByteCString() &&
GO->getParent()->getDataLayout().getPreferredAlignment(
cast<GlobalVariable>(GO)) < 32)
return CStringSection;
// Do not put 16-bit arrays in the UString section if they have an
// externally visible label, this runs into issues with certain linker
// versions.
if (Kind.isMergeable2ByteCString() && !GO->hasExternalLinkage() &&
GO->getParent()->getDataLayout().getPreferredAlignment(
cast<GlobalVariable>(GO)) < 32)
return UStringSection;
// With MachO only variables whose corresponding symbol starts with 'l' or
// 'L' can be merged, so we only try merging GVs with private linkage.
if (GO->hasPrivateLinkage() && Kind.isMergeableConst()) {
if (Kind.isMergeableConst4())
return FourByteConstantSection;
if (Kind.isMergeableConst8())
return EightByteConstantSection;
if (Kind.isMergeableConst16())
return SixteenByteConstantSection;
}
// Otherwise, if it is readonly, but not something we can specially optimize,
// just drop it in .const.
if (Kind.isReadOnly())
return ReadOnlySection;
// If this is marked const, put it into a const section. But if the dynamic
// linker needs to write to it, put it in the data segment.
if (Kind.isReadOnlyWithRel())
return ConstDataSection;
// Put zero initialized globals with strong external linkage in the
// DATA, __common section with the .zerofill directive.
if (Kind.isBSSExtern())
return DataCommonSection;
// Put zero initialized globals with local linkage in __DATA,__bss directive
// with the .zerofill directive (aka .lcomm).
if (Kind.isBSSLocal())
return DataBSSSection;
// Otherwise, just drop the variable in the normal data section.
return DataSection;
}
MCSection *TargetLoweringObjectFileMachO::getSectionForConstant(
const DataLayout &DL, SectionKind Kind, const Constant *C,
unsigned &Align) const {
// If this constant requires a relocation, we have to put it in the data
// segment, not in the text segment.
if (Kind.isData() || Kind.isReadOnlyWithRel())
return ConstDataSection;
if (Kind.isMergeableConst4())
return FourByteConstantSection;
if (Kind.isMergeableConst8())
return EightByteConstantSection;
if (Kind.isMergeableConst16())
return SixteenByteConstantSection;
return ReadOnlySection; // .const
}
const MCExpr *TargetLoweringObjectFileMachO::getTTypeGlobalReference(
const GlobalValue *GV, unsigned Encoding, const TargetMachine &TM,
MachineModuleInfo *MMI, MCStreamer &Streamer) const {
// The mach-o version of this method defaults to returning a stub reference.
if (Encoding & DW_EH_PE_indirect) {
MachineModuleInfoMachO &MachOMMI =
MMI->getObjFileInfo<MachineModuleInfoMachO>();
MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
// Add information about the stub reference to MachOMMI so that the stub
// gets emitted by the asmprinter.
MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
if (!StubSym.getPointer()) {
MCSymbol *Sym = TM.getSymbol(GV);
StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
}
return TargetLoweringObjectFile::
getTTypeReference(MCSymbolRefExpr::create(SSym, getContext()),
Encoding & ~DW_EH_PE_indirect, Streamer);
}
return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, TM,
MMI, Streamer);
}
MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
const GlobalValue *GV, const TargetMachine &TM,
MachineModuleInfo *MMI) const {
// The mach-o version of this method defaults to returning a stub reference.
MachineModuleInfoMachO &MachOMMI =
MMI->getObjFileInfo<MachineModuleInfoMachO>();
MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", TM);
// Add information about the stub reference to MachOMMI so that the stub
// gets emitted by the asmprinter.
MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(SSym);
if (!StubSym.getPointer()) {
MCSymbol *Sym = TM.getSymbol(GV);
StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
}
return SSym;
}
const MCExpr *TargetLoweringObjectFileMachO::getIndirectSymViaGOTPCRel(
const MCSymbol *Sym, const MCValue &MV, int64_t Offset,
MachineModuleInfo *MMI, MCStreamer &Streamer) const {
// Although MachO 32-bit targets do not explicitly have a GOTPCREL relocation
// as 64-bit do, we replace the GOT equivalent by accessing the final symbol
// through a non_lazy_ptr stub instead. One advantage is that it allows the
// computation of deltas to final external symbols. Example:
//
// _extgotequiv:
// .long _extfoo
//
// _delta:
// .long _extgotequiv-_delta
//
// is transformed to:
//
// _delta:
// .long L_extfoo$non_lazy_ptr-(_delta+0)
//
// .section __IMPORT,__pointers,non_lazy_symbol_pointers
// L_extfoo$non_lazy_ptr:
// .indirect_symbol _extfoo
// .long 0
//
MachineModuleInfoMachO &MachOMMI =
MMI->getObjFileInfo<MachineModuleInfoMachO>();
MCContext &Ctx = getContext();
// The offset must consider the original displacement from the base symbol
// since 32-bit targets don't have a GOTPCREL to fold the PC displacement.
Offset = -MV.getConstant();
const MCSymbol *BaseSym = &MV.getSymB()->getSymbol();
// Access the final symbol via sym$non_lazy_ptr and generate the appropriated
// non_lazy_ptr stubs.
SmallString<128> Name;
StringRef Suffix = "$non_lazy_ptr";
Name += MMI->getModule()->getDataLayout().getPrivateGlobalPrefix();
Name += Sym->getName();
Name += Suffix;
MCSymbol *Stub = Ctx.getOrCreateSymbol(Name);
MachineModuleInfoImpl::StubValueTy &StubSym = MachOMMI.getGVStubEntry(Stub);
if (!StubSym.getPointer())
StubSym = MachineModuleInfoImpl::
StubValueTy(const_cast<MCSymbol *>(Sym), true /* access indirectly */);
const MCExpr *BSymExpr =
MCSymbolRefExpr::create(BaseSym, MCSymbolRefExpr::VK_None, Ctx);
const MCExpr *LHS =
MCSymbolRefExpr::create(Stub, MCSymbolRefExpr::VK_None, Ctx);
if (!Offset)
return MCBinaryExpr::createSub(LHS, BSymExpr, Ctx);
const MCExpr *RHS =
MCBinaryExpr::createAdd(BSymExpr, MCConstantExpr::create(Offset, Ctx), Ctx);
return MCBinaryExpr::createSub(LHS, RHS, Ctx);
}
static bool canUsePrivateLabel(const MCAsmInfo &AsmInfo,
const MCSection &Section) {
if (!AsmInfo.isSectionAtomizableBySymbols(Section))
return true;
// If it is not dead stripped, it is safe to use private labels.
const MCSectionMachO &SMO = cast<MCSectionMachO>(Section);
if (SMO.hasAttribute(MachO::S_ATTR_NO_DEAD_STRIP))
return true;
return false;
}
void TargetLoweringObjectFileMachO::getNameWithPrefix(
SmallVectorImpl<char> &OutName, const GlobalValue *GV,
const TargetMachine &TM) const {
bool CannotUsePrivateLabel = true;
if (auto *GO = GV->getBaseObject()) {
SectionKind GOKind = TargetLoweringObjectFile::getKindForGlobal(GO, TM);
const MCSection *TheSection = SectionForGlobal(GO, GOKind, TM);
CannotUsePrivateLabel =
!canUsePrivateLabel(*TM.getMCAsmInfo(), *TheSection);
}
getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
}
//===----------------------------------------------------------------------===//
// COFF
//===----------------------------------------------------------------------===//
static unsigned
getCOFFSectionFlags(SectionKind K, const TargetMachine &TM) {
unsigned Flags = 0;
bool isThumb = TM.getTargetTriple().getArch() == Triple::thumb;
if (K.isMetadata())
Flags |=
COFF::IMAGE_SCN_MEM_DISCARDABLE;
else if (K.isText())
Flags |=
COFF::IMAGE_SCN_MEM_EXECUTE |
COFF::IMAGE_SCN_MEM_READ |
COFF::IMAGE_SCN_CNT_CODE |
(isThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0);
else if (K.isBSS())
Flags |=
COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ |
COFF::IMAGE_SCN_MEM_WRITE;
else if (K.isThreadLocal())
Flags |=
COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ |
COFF::IMAGE_SCN_MEM_WRITE;
else if (K.isReadOnly() || K.isReadOnlyWithRel())
Flags |=
COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ;
else if (K.isWriteable())
Flags |=
COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ |
COFF::IMAGE_SCN_MEM_WRITE;
return Flags;
}
static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
const Comdat *C = GV->getComdat();
assert(C && "expected GV to have a Comdat!");
StringRef ComdatGVName = C->getName();
const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
if (!ComdatGV)
report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
"' does not exist.");
if (ComdatGV->getComdat() != C)
report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
"' is not a key for its COMDAT.");
return ComdatGV;
}
static int getSelectionForCOFF(const GlobalValue *GV) {
if (const Comdat *C = GV->getComdat()) {
const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
ComdatKey = GA->getBaseObject();
if (ComdatKey == GV) {
switch (C->getSelectionKind()) {
case Comdat::Any:
return COFF::IMAGE_COMDAT_SELECT_ANY;
case Comdat::ExactMatch:
return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
case Comdat::Largest:
return COFF::IMAGE_COMDAT_SELECT_LARGEST;
case Comdat::NoDuplicates:
return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
case Comdat::SameSize:
return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
}
} else {
return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
}
}
return 0;
}
MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
int Selection = 0;
unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
StringRef Name = GO->getSection();
StringRef COMDATSymName = "";
if (GO->hasComdat()) {
Selection = getSelectionForCOFF(GO);
const GlobalValue *ComdatGV;
if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
ComdatGV = getComdatGVForCOFF(GO);
else
ComdatGV = GO;
if (!ComdatGV->hasPrivateLinkage()) {
MCSymbol *Sym = TM.getSymbol(ComdatGV);
COMDATSymName = Sym->getName();
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
} else {
Selection = 0;
}
}
return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
Selection);
}