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TargetLoweringObjectFileImpl.cpp
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//===- llvm/CodeGen/TargetLoweringObjectFileImpl.cpp - Object File Info ---===//
//
// 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 implements classes used to handle lowerings specific to common
// object file formats.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
#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/BinaryFormat/COFF.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/BinaryFormat/MachO.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/MachineModuleInfoImpls.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/Format.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include <cassert>
#include <string>
using namespace llvm;
using namespace dwarf;
static void GetObjCImageInfo(Module &M, unsigned &Version, unsigned &Flags,
StringRef &Section) {
SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
M.getModuleFlagsMetadata(ModuleFlags);
for (const auto &MFE: ModuleFlags) {
// Ignore flags with 'Require' behaviour.
if (MFE.Behavior == Module::Require)
continue;
StringRef Key = MFE.Key->getString();
if (Key == "Objective-C Image Info Version") {
Version = mdconst::extract<ConstantInt>(MFE.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") {
Flags |= mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
} else if (Key == "Objective-C Image Info Section") {
Section = cast<MDString>(MFE.Val)->getString();
}
}
}
//===----------------------------------------------------------------------===//
// ELF
//===----------------------------------------------------------------------===//
void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
const TargetMachine &TgtM) {
TargetLoweringObjectFile::Initialize(Ctx, TgtM);
TM = &TgtM;
CodeModel::Model CM = TgtM.getCodeModel();
switch (TgtM.getTargetTriple().getArch()) {
case Triple::arm:
case Triple::armeb:
case Triple::thumb:
case Triple::thumbeb:
if (Ctx.getAsmInfo()->getExceptionHandlingType() == ExceptionHandling::ARM)
break;
// Fallthrough if not using EHABI
LLVM_FALLTHROUGH;
case Triple::ppc:
case Triple::x86:
PersonalityEncoding = isPositionIndependent()
? dwarf::DW_EH_PE_indirect |
dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4
: dwarf::DW_EH_PE_absptr;
LSDAEncoding = isPositionIndependent()
? dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
: dwarf::DW_EH_PE_absptr;
TTypeEncoding = isPositionIndependent()
? dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4
: dwarf::DW_EH_PE_absptr;
break;
case Triple::x86_64:
if (isPositionIndependent()) {
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
((CM == CodeModel::Small || CM == CodeModel::Medium)
? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
LSDAEncoding = dwarf::DW_EH_PE_pcrel |
(CM == CodeModel::Small
? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
((CM == CodeModel::Small || CM == CodeModel::Medium)
? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
} else {
PersonalityEncoding =
(CM == CodeModel::Small || CM == CodeModel::Medium)
? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
LSDAEncoding = (CM == CodeModel::Small)
? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
TTypeEncoding = (CM == CodeModel::Small)
? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
}
break;
case Triple::hexagon:
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
LSDAEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
if (isPositionIndependent()) {
PersonalityEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
LSDAEncoding |= dwarf::DW_EH_PE_pcrel;
TTypeEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
}
break;
case Triple::aarch64:
case Triple::aarch64_be:
// The small model guarantees static code/data size < 4GB, but not where it
// will be in memory. Most of these could end up >2GB away so even a signed
// pc-relative 32-bit address is insufficient, theoretically.
if (isPositionIndependent()) {
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata8;
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata8;
} else {
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
LSDAEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
}
break;
case Triple::lanai:
LSDAEncoding = dwarf::DW_EH_PE_absptr;
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
break;
case Triple::mips:
case Triple::mipsel:
case Triple::mips64:
case Triple::mips64el:
// MIPS uses indirect pointer to refer personality functions and types, so
// that the eh_frame section can be read-only. DW.ref.personality will be
// generated for relocation.
PersonalityEncoding = dwarf::DW_EH_PE_indirect;
// FIXME: The N64 ABI probably ought to use DW_EH_PE_sdata8 but we can't
// identify N64 from just a triple.
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
// We don't support PC-relative LSDA references in GAS so we use the default
// DW_EH_PE_absptr for those.
// FreeBSD must be explicit about the data size and using pcrel since it's
// assembler/linker won't do the automatic conversion that the Linux tools
// do.
if (TgtM.getTargetTriple().isOSFreeBSD()) {
PersonalityEncoding |= dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
}
break;
case Triple::ppc64:
case Triple::ppc64le:
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_udata8;
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_udata8;
break;
case Triple::sparcel:
case Triple::sparc:
if (isPositionIndependent()) {
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
} else {
LSDAEncoding = dwarf::DW_EH_PE_absptr;
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
}
break;
case Triple::sparcv9:
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
if (isPositionIndependent()) {
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
} else {
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
}
break;
case Triple::systemz:
// All currently-defined code models guarantee that 4-byte PC-relative
// values will be in range.
if (isPositionIndependent()) {
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
} else {
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
LSDAEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
}
break;
default:
break;
}
}
void TargetLoweringObjectFileELF::emitModuleMetadata(MCStreamer &Streamer,
Module &M) const {
auto &C = getContext();
if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
auto *S = C.getELFSection(".linker-options", ELF::SHT_LLVM_LINKER_OPTIONS,
ELF::SHF_EXCLUDE);
Streamer.SwitchSection(S);
for (const auto &Operand : LinkerOptions->operands()) {
if (cast<MDNode>(Operand)->getNumOperands() != 2)
report_fatal_error("invalid llvm.linker.options");
for (const auto &Option : cast<MDNode>(Operand)->operands()) {
Streamer.EmitBytes(cast<MDString>(Option)->getString());
Streamer.EmitIntValue(0, 1);
}
}
}
if (NamedMDNode *DependentLibraries = M.getNamedMetadata("llvm.dependent-libraries")) {
auto *S = C.getELFSection(".deplibs", ELF::SHT_LLVM_DEPENDENT_LIBRARIES,
ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
Streamer.SwitchSection(S);
for (const auto &Operand : DependentLibraries->operands()) {
Streamer.EmitBytes(
cast<MDString>(cast<MDNode>(Operand)->getOperand(0))->getString());
Streamer.EmitIntValue(0, 1);
}
}
unsigned Version = 0;
unsigned Flags = 0;
StringRef Section;
GetObjCImageInfo(M, Version, Flags, Section);
if (!Section.empty()) {
auto *S = C.getELFSection(Section, ELF::SHT_PROGBITS, ELF::SHF_ALLOC);
Streamer.SwitchSection(S);
Streamer.EmitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
Streamer.EmitIntValue(Version, 4);
Streamer.EmitIntValue(Flags, 4);
Streamer.AddBlankLine();
}
SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
M.getModuleFlagsMetadata(ModuleFlags);
MDNode *CFGProfile = nullptr;
for (const auto &MFE : ModuleFlags) {
StringRef Key = MFE.Key->getString();
if (Key == "CG Profile") {
CFGProfile = cast<MDNode>(MFE.Val);
break;
}
}
if (!CFGProfile)
return;
auto GetSym = [this](const MDOperand &MDO) -> MCSymbol * {
if (!MDO)
return nullptr;
auto V = cast<ValueAsMetadata>(MDO);
const Function *F = cast<Function>(V->getValue());
return TM->getSymbol(F);
};
for (const auto &Edge : CFGProfile->operands()) {
MDNode *E = cast<MDNode>(Edge);
const MCSymbol *From = GetSym(E->getOperand(0));
const MCSymbol *To = GetSym(E->getOperand(1));
// Skip null functions. This can happen if functions are dead stripped after
// the CGProfile pass has been run.
if (!From || !To)
continue;
uint64_t Count = cast<ConstantAsMetadata>(E->getOperand(2))
->getValue()
->getUniqueInteger()
.getZExtValue();
Streamer.emitCGProfileEntry(
MCSymbolRefExpr::create(From, MCSymbolRefExpr::VK_None, C),
MCSymbolRefExpr::create(To, MCSymbolRefExpr::VK_None, C), Count);
}
}
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(0));
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 not 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;
// 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;
const MDOperand &Op = MD->getOperand(0);
if (!Op.get())
return nullptr;
auto *VM = dyn_cast<ValueAsMetadata>(Op);
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;
}
static unsigned getEntrySizeForKind(SectionKind Kind) {
if (Kind.isMergeable1ByteCString())
return 1;
else if (Kind.isMergeable2ByteCString())
return 2;
else if (Kind.isMergeable4ByteCString())
return 4;
else if (Kind.isMergeableConst4())
return 4;
else if (Kind.isMergeableConst8())
return 8;
else if (Kind.isMergeableConst16())
return 16;
else if (Kind.isMergeableConst32())
return 32;
else {
// We shouldn't have mergeable C strings or mergeable constants that we
// didn't handle above.
assert(!Kind.isMergeableCString() && "unknown string width");
assert(!Kind.isMergeableConst() && "unknown data width");
return 0;
}
}
MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
StringRef SectionName = GO->getSection();
// Check if '#pragma clang section' name is applicable.
// Note that pragma directive overrides -ffunction-section, -fdata-section
// and so section name is exactly as user specified and not uniqued.
const GlobalVariable *GV = dyn_cast<GlobalVariable>(GO);
if (GV && GV->hasImplicitSection()) {
auto Attrs = GV->getAttributes();
if (Attrs.hasAttribute("bss-section") && Kind.isBSS()) {
SectionName = Attrs.getAttribute("bss-section").getValueAsString();
} else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()) {
SectionName = Attrs.getAttribute("rodata-section").getValueAsString();
} else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
SectionName = Attrs.getAttribute("data-section").getValueAsString();
}
}
const Function *F = dyn_cast<Function>(GO);
if (F && F->hasFnAttribute("implicit-section-name")) {
SectionName = F->getFnAttribute("implicit-section-name").getValueAsString();
}
// 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,
getEntrySizeForKind(Kind), 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 &&
"Associated symbol mismatch between sections");
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) {
StringRef Group = "";
if (const Comdat *C = getELFComdat(GO)) {
Flags |= ELF::SHF_GROUP;
Group = C->getName();
}
// Get the section entry size based on the kind.
unsigned EntrySize = getEntrySizeForKind(Kind);
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;
}
unsigned UniqueID = MCContext::GenericSectionID;
if (EmitUniqueSection) {
if (TM.getUniqueSectionNames()) {
Name.push_back('.');
TM.getNameWithPrefix(Name, GO, Mang, true /*MayAlwaysUsePrivate*/);
} else {
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)
raw_string_ostream(Name) << format(".%05u", 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());
}
MCSection *TargetLoweringObjectFileELF::getSectionForCommandLines() const {
// Use ".GCC.command.line" since this feature is to support clang's
// -frecord-gcc-switches which in turn attempts to mimic GCC's switch of the
// same name.
return getContext().getELFSection(".GCC.command.line", ELF::SHT_PROGBITS,
ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
}
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());
}
PersonalityEncoding =
dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
LSDAEncoding = dwarf::DW_EH_PE_pcrel;
TTypeEncoding =
dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
}
void TargetLoweringObjectFileMachO::emitModuleMetadata(MCStreamer &Streamer,
Module &M) const {
// Emit the linker options if present.
if (auto *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
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);
}
}
unsigned VersionVal = 0;
unsigned ImageInfoFlags = 0;
StringRef SectionVal;
GetObjCImageInfo(M, VersionVal, ImageInfoFlags, SectionVal);
// 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;
if (Kind.isReadOnlyWithRel())
return ConstDataCoalSection;
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.