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llvm-project/llvm/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
YunQiang Su 8f21294897
MIPS: Use pcrel|sdata4 for eh_frame (#91291) 
Gas uses encoding DW_EH_PE_absptr for PIC, and gnu ld converts it to
DW_EH_PE_sdata4|DW_EH_PE_pcrel.
LLD doesn't have this workarounding, thus complains
```
  relocation R_MIPS_32 cannot be used against local symbol; recompile with -fPIC
  relocation R_MIPS_64 cannot be used against local symbol; recompile with -fPIC
```

So, let's generates asm/obj files with `DW_EH_PE_sdata4|DW_EH_PE_pcrel`
encoding. In fact, GNU ld supports such OBJs well.

For N64, maybe we should use sdata8, while GNU ld doesn't support it
well, and in fact sdata4 is enough now. So we just ignore the `Large`
for `MCObjectFileInfo::initELFMCObjectFileInfo`. Maybe we should switch
back to sdata8 once GNU LD supports it well.

Fixes: #58377.
2024-05-08 17:30:14 +08:00

2747 lines
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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/BinaryFormat/COFF.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/BinaryFormat/MachO.h"
#include "llvm/BinaryFormat/Wasm.h"
#include "llvm/CodeGen/BasicBlockSectionUtils.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.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/DiagnosticInfo.h"
#include "llvm/IR/DiagnosticPrinter.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/PseudoProbe.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/MCSectionGOFF.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSectionWasm.h"
#include "llvm/MC/MCSectionXCOFF.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/Base64.h"
#include "llvm/Support/Casting.h"
#include "llvm/Support/CodeGen.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/Format.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/TargetParser/Triple.h"
#include <cassert>
#include <string>
using namespace llvm;
using namespace dwarf;
static cl::opt<bool> JumpTableInFunctionSection(
"jumptable-in-function-section", cl::Hidden, cl::init(false),
cl::desc("Putting Jump Table in function section"));
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();
}
// Backend generates L_OBJC_IMAGE_INFO from Swift ABI version + major + minor +
// "Objective-C Garbage Collection".
else if (Key == "Swift ABI Version") {
Flags |= (mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue()) << 8;
} else if (Key == "Swift Major Version") {
Flags |= (mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue()) << 24;
} else if (Key == "Swift Minor Version") {
Flags |= (mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue()) << 16;
}
}
}
//===----------------------------------------------------------------------===//
// ELF
//===----------------------------------------------------------------------===//
TargetLoweringObjectFileELF::TargetLoweringObjectFileELF() {
SupportDSOLocalEquivalentLowering = true;
}
void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
const TargetMachine &TgtM) {
TargetLoweringObjectFile::Initialize(Ctx, TgtM);
CodeModel::Model CM = TgtM.getCodeModel();
InitializeELF(TgtM.Options.UseInitArray);
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
[[fallthrough]];
case Triple::ppc:
case Triple::ppcle:
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_sdata4 : dwarf::DW_EH_PE_sdata8);
} 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:
case Triple::aarch64_32:
// 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.
//
// Use DW_EH_PE_indirect even for -fno-pic to avoid copy relocations.
LSDAEncoding = dwarf::DW_EH_PE_pcrel |
(TgtM.getTargetTriple().getEnvironment() == Triple::GNUILP32
? dwarf::DW_EH_PE_sdata4
: dwarf::DW_EH_PE_sdata8);
PersonalityEncoding = LSDAEncoding | dwarf::DW_EH_PE_indirect;
TTypeEncoding = LSDAEncoding | dwarf::DW_EH_PE_indirect;
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;
// 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 (isPositionIndependent() || 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;
}
CallSiteEncoding = dwarf::DW_EH_PE_udata4;
break;
case Triple::riscv32:
case Triple::riscv64:
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;
CallSiteEncoding = dwarf::DW_EH_PE_udata4;
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;
case Triple::loongarch32:
case Triple::loongarch64:
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;
break;
default:
break;
}
}
void TargetLoweringObjectFileELF::getModuleMetadata(Module &M) {
SmallVector<GlobalValue *, 4> Vec;
collectUsedGlobalVariables(M, Vec, false);
for (GlobalValue *GV : Vec)
if (auto *GO = dyn_cast<GlobalObject>(GV))
Used.insert(GO);
}
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.emitInt8(0);
}
}
}
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.emitInt8(0);
}
}
if (NamedMDNode *FuncInfo = M.getNamedMetadata(PseudoProbeDescMetadataName)) {
// Emit a descriptor for every function including functions that have an
// available external linkage. We may not want this for imported functions
// that has code in another thinLTO module but we don't have a good way to
// tell them apart from inline functions defined in header files. Therefore
// we put each descriptor in a separate comdat section and rely on the
// linker to deduplicate.
for (const auto *Operand : FuncInfo->operands()) {
const auto *MD = cast<MDNode>(Operand);
auto *GUID = mdconst::dyn_extract<ConstantInt>(MD->getOperand(0));
auto *Hash = mdconst::dyn_extract<ConstantInt>(MD->getOperand(1));
auto *Name = cast<MDString>(MD->getOperand(2));
auto *S = C.getObjectFileInfo()->getPseudoProbeDescSection(
TM->getFunctionSections() ? Name->getString() : StringRef());
Streamer.switchSection(S);
Streamer.emitInt64(GUID->getZExtValue());
Streamer.emitInt64(Hash->getZExtValue());
Streamer.emitULEB128IntValue(Name->getString().size());
Streamer.emitBytes(Name->getString());
}
}
if (NamedMDNode *LLVMStats = M.getNamedMetadata("llvm.stats")) {
// Emit the metadata for llvm statistics into .llvm_stats section, which is
// formatted as a list of key/value pair, the value is base64 encoded.
auto *S = C.getObjectFileInfo()->getLLVMStatsSection();
Streamer.switchSection(S);
for (const auto *Operand : LLVMStats->operands()) {
const auto *MD = cast<MDNode>(Operand);
assert(MD->getNumOperands() % 2 == 0 &&
("Operand num should be even for a list of key/value pair"));
for (size_t I = 0; I < MD->getNumOperands(); I += 2) {
// Encode the key string size.
auto *Key = cast<MDString>(MD->getOperand(I));
Streamer.emitULEB128IntValue(Key->getString().size());
Streamer.emitBytes(Key->getString());
// Encode the value into a Base64 string.
std::string Value = encodeBase64(
Twine(mdconst::dyn_extract<ConstantInt>(MD->getOperand(I + 1))
->getZExtValue())
.str());
Streamer.emitULEB128IntValue(Value.size());
Streamer.emitBytes(Value);
}
}
}
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.emitInt32(Version);
Streamer.emitInt32(Flags);
Streamer.addBlankLine();
}
emitCGProfileMetadata(Streamer, M);
}
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) ||
Name == getInstrProfSectionName(IPSK_covfun, Triple::ELF,
/*AddSegmentInfo=*/false) ||
Name == getInstrProfSectionName(IPSK_covdata, Triple::ELF,
/*AddSegmentInfo=*/false) ||
Name == getInstrProfSectionName(IPSK_covname, Triple::ELF,
/*AddSegmentInfo=*/false) ||
Name == ".llvmbc" || Name == ".llvmcmd")
return SectionKind::getMetadata();
if (!Name.starts_with(".")) return K;
// Default implementation based on some magic section names.
if (Name == ".bss" || Name.starts_with(".bss.") ||
Name.starts_with(".gnu.linkonce.b.") ||
Name.starts_with(".llvm.linkonce.b.") || Name == ".sbss" ||
Name.starts_with(".sbss.") || Name.starts_with(".gnu.linkonce.sb.") ||
Name.starts_with(".llvm.linkonce.sb."))
return SectionKind::getBSS();
if (Name == ".tdata" || Name.starts_with(".tdata.") ||
Name.starts_with(".gnu.linkonce.td.") ||
Name.starts_with(".llvm.linkonce.td."))
return SectionKind::getThreadData();
if (Name == ".tbss" || Name.starts_with(".tbss.") ||
Name.starts_with(".gnu.linkonce.tb.") ||
Name.starts_with(".llvm.linkonce.tb."))
return SectionKind::getThreadBSS();
return K;
}
static bool hasPrefix(StringRef SectionName, StringRef Prefix) {
return SectionName.consume_front(Prefix) &&
(SectionName.empty() || SectionName[0] == '.');
}
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.starts_with(".note"))
return ELF::SHT_NOTE;
if (hasPrefix(Name, ".init_array"))
return ELF::SHT_INIT_ARRAY;
if (hasPrefix(Name, ".fini_array"))
return ELF::SHT_FINI_ARRAY;
if (hasPrefix(Name, ".preinit_array"))
return ELF::SHT_PREINIT_ARRAY;
if (hasPrefix(Name, ".llvm.offloading"))
return ELF::SHT_LLVM_OFFLOADING;
if (K.isBSS() || K.isThreadBSS())
return ELF::SHT_NOBITS;
return ELF::SHT_PROGBITS;
}
static unsigned getELFSectionFlags(SectionKind K) {
unsigned Flags = 0;
if (!K.isMetadata() && !K.isExclude())
Flags |= ELF::SHF_ALLOC;
if (K.isExclude())
Flags |= ELF::SHF_EXCLUDE;
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 &&
C->getSelectionKind() != Comdat::NoDeduplicate)
report_fatal_error("ELF COMDATs only support SelectionKind::Any and "
"SelectionKind::NoDeduplicate, '" +
C->getName() + "' cannot be lowered.");
return C;
}
static const MCSymbolELF *getLinkedToSymbol(const GlobalObject *GO,
const TargetMachine &TM) {
MDNode *MD = GO->getMetadata(LLVMContext::MD_associated);
if (!MD)
return nullptr;
auto *VM = cast<ValueAsMetadata>(MD->getOperand(0).get());
auto *OtherGV = dyn_cast<GlobalValue>(VM->getValue());
return OtherGV ? dyn_cast<MCSymbolELF>(TM.getSymbol(OtherGV)) : 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;
}
}
/// Return the section prefix name used by options FunctionsSections and
/// DataSections.
static StringRef getSectionPrefixForGlobal(SectionKind Kind, bool IsLarge) {
if (Kind.isText())
return IsLarge ? ".ltext" : ".text";
if (Kind.isReadOnly())
return IsLarge ? ".lrodata" : ".rodata";
if (Kind.isBSS())
return IsLarge ? ".lbss" : ".bss";
if (Kind.isThreadData())
return ".tdata";
if (Kind.isThreadBSS())
return ".tbss";
if (Kind.isData())
return IsLarge ? ".ldata" : ".data";
if (Kind.isReadOnlyWithRel())
return IsLarge ? ".ldata.rel.ro" : ".data.rel.ro";
llvm_unreachable("Unknown section kind");
}
static SmallString<128>
getELFSectionNameForGlobal(const GlobalObject *GO, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM,
unsigned EntrySize, bool UniqueSectionName) {
SmallString<128> Name =
getSectionPrefixForGlobal(Kind, TM.isLargeGlobalValue(GO));
if (Kind.isMergeableCString()) {
// We also need alignment here.
// FIXME: this is getting the alignment of the character, not the
// alignment of the global!
Align Alignment = GO->getParent()->getDataLayout().getPreferredAlign(
cast<GlobalVariable>(GO));
Name += ".str";
Name += utostr(EntrySize);
Name += ".";
Name += utostr(Alignment.value());
} else if (Kind.isMergeableConst()) {
Name += ".cst";
Name += utostr(EntrySize);
}
bool HasPrefix = false;
if (const auto *F = dyn_cast<Function>(GO)) {
if (std::optional<StringRef> Prefix = F->getSectionPrefix()) {
raw_svector_ostream(Name) << '.' << *Prefix;
HasPrefix = true;
}
}
if (UniqueSectionName) {
Name.push_back('.');
TM.getNameWithPrefix(Name, GO, Mang, /*MayAlwaysUsePrivate*/true);
} else if (HasPrefix)
// For distinguishing between .text.${text-section-prefix}. (with trailing
// dot) and .text.${function-name}
Name.push_back('.');
return Name;
}
namespace {
class LoweringDiagnosticInfo : public DiagnosticInfo {
const Twine &Msg;
public:
LoweringDiagnosticInfo(const Twine &DiagMsg,
DiagnosticSeverity Severity = DS_Error)
: DiagnosticInfo(DK_Lowering, Severity), Msg(DiagMsg) {}
void print(DiagnosticPrinter &DP) const override { DP << Msg; }
};
}
/// Calculate an appropriate unique ID for a section, and update Flags,
/// EntrySize and NextUniqueID where appropriate.
static unsigned
calcUniqueIDUpdateFlagsAndSize(const GlobalObject *GO, StringRef SectionName,
SectionKind Kind, const TargetMachine &TM,
MCContext &Ctx, Mangler &Mang, unsigned &Flags,
unsigned &EntrySize, unsigned &NextUniqueID,
const bool Retain, const bool ForceUnique) {
// Increment uniqueID if we are forced to emit a unique section.
// This works perfectly fine with section attribute or pragma section as the
// sections with the same name are grouped together by the assembler.
if (ForceUnique)
return NextUniqueID++;
// A section can have at most one associated section. Put each global with
// MD_associated in a unique section.
const bool Associated = GO->getMetadata(LLVMContext::MD_associated);
if (Associated) {
Flags |= ELF::SHF_LINK_ORDER;
return NextUniqueID++;
}
if (Retain) {
if (TM.getTargetTriple().isOSSolaris())
Flags |= ELF::SHF_SUNW_NODISCARD;
else if (Ctx.getAsmInfo()->useIntegratedAssembler() ||
Ctx.getAsmInfo()->binutilsIsAtLeast(2, 36))
Flags |= ELF::SHF_GNU_RETAIN;
return NextUniqueID++;
}
// If two symbols with differing sizes end up in the same mergeable section
// that section can be assigned an incorrect entry size. To avoid this we
// usually put symbols of the same size into distinct mergeable sections with
// the same name. Doing so relies on the ",unique ," assembly feature. This
// feature is not avalible until bintuils version 2.35
// (https://sourceware.org/bugzilla/show_bug.cgi?id=25380).
const bool SupportsUnique = Ctx.getAsmInfo()->useIntegratedAssembler() ||
Ctx.getAsmInfo()->binutilsIsAtLeast(2, 35);
if (!SupportsUnique) {
Flags &= ~ELF::SHF_MERGE;
EntrySize = 0;
return MCContext::GenericSectionID;
}
const bool SymbolMergeable = Flags & ELF::SHF_MERGE;
const bool SeenSectionNameBefore =
Ctx.isELFGenericMergeableSection(SectionName);
// If this is the first ocurrence of this section name, treat it as the
// generic section
if (!SymbolMergeable && !SeenSectionNameBefore) {
if (TM.getSeparateNamedSections())
return NextUniqueID++;
else
return MCContext::GenericSectionID;
}
// Symbols must be placed into sections with compatible entry sizes. Generate
// unique sections for symbols that have not been assigned to compatible
// sections.
const auto PreviousID =
Ctx.getELFUniqueIDForEntsize(SectionName, Flags, EntrySize);
if (PreviousID && (!TM.getSeparateNamedSections() ||
*PreviousID == MCContext::GenericSectionID))
return *PreviousID;
// If the user has specified the same section name as would be created
// implicitly for this symbol e.g. .rodata.str1.1, then we don't need
// to unique the section as the entry size for this symbol will be
// compatible with implicitly created sections.
SmallString<128> ImplicitSectionNameStem =
getELFSectionNameForGlobal(GO, Kind, Mang, TM, EntrySize, false);
if (SymbolMergeable &&
Ctx.isELFImplicitMergeableSectionNamePrefix(SectionName) &&
SectionName.starts_with(ImplicitSectionNameStem))
return MCContext::GenericSectionID;
// We have seen this section name before, but with different flags or entity
// size. Create a new unique ID.
return NextUniqueID++;
}
static std::tuple<StringRef, bool, unsigned>
getGlobalObjectInfo(const GlobalObject *GO, const TargetMachine &TM) {
StringRef Group = "";
bool IsComdat = false;
unsigned Flags = 0;
if (const Comdat *C = getELFComdat(GO)) {
Flags |= ELF::SHF_GROUP;
Group = C->getName();
IsComdat = C->getSelectionKind() == Comdat::Any;
}
if (TM.isLargeGlobalValue(GO))
Flags |= ELF::SHF_X86_64_LARGE;
return {Group, IsComdat, Flags};
}
static MCSection *selectExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM,
MCContext &Ctx, Mangler &Mang, unsigned &NextUniqueID,
bool Retain, bool ForceUnique) {
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("relro-section") && Kind.isReadOnlyWithRel()) {
SectionName = Attrs.getAttribute("relro-section").getValueAsString();
} else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
SectionName = Attrs.getAttribute("data-section").getValueAsString();
}
}
// Infer section flags from the section name if we can.
Kind = getELFKindForNamedSection(SectionName, Kind);
unsigned Flags = getELFSectionFlags(Kind);
auto [Group, IsComdat, ExtraFlags] = getGlobalObjectInfo(GO, TM);
Flags |= ExtraFlags;
unsigned EntrySize = getEntrySizeForKind(Kind);
const unsigned UniqueID = calcUniqueIDUpdateFlagsAndSize(
GO, SectionName, Kind, TM, Ctx, Mang, Flags, EntrySize, NextUniqueID,
Retain, ForceUnique);
const MCSymbolELF *LinkedToSym = getLinkedToSymbol(GO, TM);
MCSectionELF *Section = Ctx.getELFSection(
SectionName, getELFSectionType(SectionName, Kind), Flags, EntrySize,
Group, IsComdat, UniqueID, LinkedToSym);
// 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->getLinkedToSymbol() == LinkedToSym &&
"Associated symbol mismatch between sections");
if (!(Ctx.getAsmInfo()->useIntegratedAssembler() ||
Ctx.getAsmInfo()->binutilsIsAtLeast(2, 35))) {
// If we are using GNU as before 2.35, then this symbol might have
// been placed in an incompatible mergeable section. Emit an error if this
// is the case to avoid creating broken output.
if ((Section->getFlags() & ELF::SHF_MERGE) &&
(Section->getEntrySize() != getEntrySizeForKind(Kind)))
GO->getContext().diagnose(LoweringDiagnosticInfo(
"Symbol '" + GO->getName() + "' from module '" +
(GO->getParent() ? GO->getParent()->getSourceFileName() : "unknown") +
"' required a section with entry-size=" +
Twine(getEntrySizeForKind(Kind)) + " but was placed in section '" +
SectionName + "' with entry-size=" + Twine(Section->getEntrySize()) +
": Explicit assignment by pragma or attribute of an incompatible "
"symbol to this section?"));
}
return Section;
}
MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
return selectExplicitSectionGlobal(GO, Kind, TM, getContext(), getMangler(),
NextUniqueID, Used.count(GO),
/* ForceUnique = */false);
}
static MCSectionELF *selectELFSectionForGlobal(
MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol) {
auto [Group, IsComdat, ExtraFlags] = getGlobalObjectInfo(GO, TM);
Flags |= ExtraFlags;
// Get the section entry size based on the kind.
unsigned EntrySize = getEntrySizeForKind(Kind);
bool UniqueSectionName = false;
unsigned UniqueID = MCContext::GenericSectionID;
if (EmitUniqueSection) {
if (TM.getUniqueSectionNames()) {
UniqueSectionName = true;
} else {
UniqueID = *NextUniqueID;
(*NextUniqueID)++;
}
}
SmallString<128> Name = getELFSectionNameForGlobal(
GO, Kind, Mang, TM, EntrySize, UniqueSectionName);
// 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, IsComdat, UniqueID,
AssociatedSymbol);
}
static MCSection *selectELFSectionForGlobal(
MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM, bool Retain, bool EmitUniqueSection,
unsigned Flags, unsigned *NextUniqueID) {
const MCSymbolELF *LinkedToSym = getLinkedToSymbol(GO, TM);
if (LinkedToSym) {
EmitUniqueSection = true;
Flags |= ELF::SHF_LINK_ORDER;
}
if (Retain) {
if (TM.getTargetTriple().isOSSolaris()) {
EmitUniqueSection = true;
Flags |= ELF::SHF_SUNW_NODISCARD;
} else if (Ctx.getAsmInfo()->useIntegratedAssembler() ||
Ctx.getAsmInfo()->binutilsIsAtLeast(2, 36)) {
EmitUniqueSection = true;
Flags |= ELF::SHF_GNU_RETAIN;
}
}
MCSectionELF *Section = selectELFSectionForGlobal(
Ctx, GO, Kind, Mang, TM, EmitUniqueSection, Flags,
NextUniqueID, LinkedToSym);
assert(Section->getLinkedToSymbol() == LinkedToSym);
return Section;
}
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();
return selectELFSectionForGlobal(getContext(), GO, Kind, getMangler(), TM,
Used.count(GO), EmitUniqueSection, Flags,
&NextUniqueID);
}
MCSection *TargetLoweringObjectFileELF::getUniqueSectionForFunction(
const Function &F, const TargetMachine &TM) const {
SectionKind Kind = SectionKind::getText();
unsigned Flags = getELFSectionFlags(Kind);
// If the function's section names is pre-determined via pragma or a
// section attribute, call selectExplicitSectionGlobal.
if (F.hasSection())
return selectExplicitSectionGlobal(
&F, Kind, TM, getContext(), getMangler(), NextUniqueID,
Used.count(&F), /* ForceUnique = */true);
else
return selectELFSectionForGlobal(
getContext(), &F, Kind, getMangler(), TM, Used.count(&F),
/*EmitUniqueSection=*/true, Flags, &NextUniqueID);
}
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);
}
MCSection *TargetLoweringObjectFileELF::getSectionForLSDA(
const Function &F, const MCSymbol &FnSym, const TargetMachine &TM) const {
// If neither COMDAT nor function sections, use the monolithic LSDA section.
// Re-use this path if LSDASection is null as in the Arm EHABI.
if (!LSDASection || (!F.hasComdat() && !TM.getFunctionSections()))
return LSDASection;
const auto *LSDA = cast<MCSectionELF>(LSDASection);
unsigned Flags = LSDA->getFlags();
const MCSymbolELF *LinkedToSym = nullptr;
StringRef Group;
bool IsComdat = false;
if (const Comdat *C = getELFComdat(&F)) {
Flags |= ELF::SHF_GROUP;
Group = C->getName();
IsComdat = C->getSelectionKind() == Comdat::Any;
}
// Use SHF_LINK_ORDER to facilitate --gc-sections if we can use GNU ld>=2.36
// or LLD, which support mixed SHF_LINK_ORDER & non-SHF_LINK_ORDER.
if (TM.getFunctionSections() &&
(getContext().getAsmInfo()->useIntegratedAssembler() &&
getContext().getAsmInfo()->binutilsIsAtLeast(2, 36))) {
Flags |= ELF::SHF_LINK_ORDER;
LinkedToSym = cast<MCSymbolELF>(&FnSym);
}
// Append the function name as the suffix like GCC, assuming
// -funique-section-names applies to .gcc_except_table sections.
return getContext().getELFSection(
(TM.getUniqueSectionNames() ? LSDA->getName() + "." + F.getName()
: LSDA->getName()),
LSDA->getType(), Flags, 0, Group, IsComdat, MCSection::NonUniqueID,
LinkedToSym);
}
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,
Align &Alignment) 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;
}
/// Returns a unique section for the given machine basic block.
MCSection *TargetLoweringObjectFileELF::getSectionForMachineBasicBlock(
const Function &F, const MachineBasicBlock &MBB,
const TargetMachine &TM) const {
assert(MBB.isBeginSection() && "Basic block does not start a section!");
unsigned UniqueID = MCContext::GenericSectionID;
// For cold sections use the .text.split. prefix along with the parent
// function name. All cold blocks for the same function go to the same
// section. Similarly all exception blocks are grouped by symbol name
// under the .text.eh prefix. For regular sections, we either use a unique
// name, or a unique ID for the section.
SmallString<128> Name;
StringRef FunctionSectionName = MBB.getParent()->getSection()->getName();
if (FunctionSectionName == ".text" ||
FunctionSectionName.starts_with(".text.")) {
// Function is in a regular .text section.
StringRef FunctionName = MBB.getParent()->getName();
if (MBB.getSectionID() == MBBSectionID::ColdSectionID) {
Name += BBSectionsColdTextPrefix;
Name += FunctionName;
} else if (MBB.getSectionID() == MBBSectionID::ExceptionSectionID) {
Name += ".text.eh.";
Name += FunctionName;
} else {
Name += FunctionSectionName;
if (TM.getUniqueBasicBlockSectionNames()) {
if (!Name.ends_with("."))
Name += ".";
Name += MBB.getSymbol()->getName();
} else {
UniqueID = NextUniqueID++;
}
}
} else {
// If the original function has a custom non-dot-text section, then emit
// all basic block sections into that section too, each with a unique id.
Name = FunctionSectionName;
UniqueID = NextUniqueID++;
}
unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_EXECINSTR;
std::string GroupName;
if (F.hasComdat()) {
Flags |= ELF::SHF_GROUP;
GroupName = F.getComdat()->getName().str();
}
return getContext().getELFSection(Name, ELF::SHT_PROGBITS, Flags,
0 /* Entry Size */, GroupName,
F.hasComdat(), UniqueID, nullptr);
}
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, /*IsComdat=*/true);
}
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 correctness 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());
}
const MCExpr *TargetLoweringObjectFileELF::lowerDSOLocalEquivalent(
const DSOLocalEquivalent *Equiv, const TargetMachine &TM) const {
assert(supportDSOLocalEquivalentLowering());
const auto *GV = Equiv->getGlobalValue();
// A PLT entry is not needed for dso_local globals.
if (GV->isDSOLocal() || GV->isImplicitDSOLocal())
return MCSymbolRefExpr::create(TM.getSymbol(GV), getContext());
return MCSymbolRefExpr::create(TM.getSymbol(GV), PLTRelativeVariantKind,
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() {
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;
}
MCSection *TargetLoweringObjectFileMachO::getStaticDtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
return StaticDtorSection;
// In userspace, we lower global destructors via atexit(), but kernel/kext
// environments do not provide this function so we still need to support the
// legacy way here.
// See the -disable-atexit-based-global-dtor-lowering CodeGen flag for more
// context.
}
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(std::string(cast<MDString>(Piece)->getString()));
Streamer.emitLinkerOptions(StrOptions);
}
}
unsigned VersionVal = 0;
unsigned ImageInfoFlags = 0;
StringRef SectionVal;
GetObjCImageInfo(M, VersionVal, ImageInfoFlags, SectionVal);
emitCGProfileMetadata(Streamer, M);
// 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;
if (Error E = MCSectionMachO::ParseSectionSpecifier(
SectionVal, Segment, Section, TAA, TAAParsed, StubSize)) {
// If invalid, report the error with report_fatal_error.
report_fatal_error("Invalid section specifier '" + Section +
"': " + toString(std::move(E)) + ".");
}
// 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.emitInt32(VersionVal);
Streamer.emitInt32(ImageInfoFlags);
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 {
StringRef SectionName = GO->getSection();
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("relro-section") && Kind.isReadOnlyWithRel()) {
SectionName = Attrs.getAttribute("relro-section").getValueAsString();
} else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
SectionName = Attrs.getAttribute("data-section").getValueAsString();
}
}
// Parse the section specifier and create it if valid.
StringRef Segment, Section;
unsigned TAA = 0, StubSize = 0;
bool TAAParsed;
checkMachOComdat(GO);
if (Error E = MCSectionMachO::ParseSectionSpecifier(
SectionName, Segment, Section, TAA, TAAParsed, StubSize)) {
// If invalid, report the error with report_fatal_error.
report_fatal_error("Global variable '" + GO->getName() +
"' has an invalid section specifier '" +
GO->getSection() + "': " + toString(std::move(E)) + ".");
}
// 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().getPreferredAlign(
cast<GlobalVariable>(GO)) < Align(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().getPreferredAlign(
cast<GlobalVariable>(GO)) < Align(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,
Align &Alignment) 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
}
MCSection *TargetLoweringObjectFileMachO::getSectionForCommandLines() const {
return getContext().getMachOSection("__TEXT", "__command_line", 0,
SectionKind::getReadOnly());
}
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 GlobalValue *GV, 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
//
// The indirect symbol table (and sections of non_lazy_symbol_pointers type)
// may point to both local (same translation unit) and global (other
// translation units) symbols. Example:
//
// .section __DATA,__pointers,non_lazy_symbol_pointers
// L1:
// .indirect_symbol _myGlobal
// .long 0
// L2:
// .indirect_symbol _myLocal
// .long _myLocal
//
// If the symbol is local, instead of the symbol's index, the assembler
// places the constant INDIRECT_SYMBOL_LOCAL into the indirect symbol table.
// Then the linker will notice the constant in the table and will look at the
// content of the symbol.
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),
!GV->hasLocalLinkage());
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;
// FIXME: we should be able to use private labels for sections that can't be
// dead-stripped (there's no issue with blocking atomization there), but `ld
// -r` sometimes drops the no_dead_strip attribute from sections so for safety
// we don't allow it.
return false;
}
void TargetLoweringObjectFileMachO::getNameWithPrefix(
SmallVectorImpl<char> &OutName, const GlobalValue *GV,
const TargetMachine &TM) const {
bool CannotUsePrivateLabel = true;
if (auto *GO = GV->getAliaseeObject()) {
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.isExclude())
Flags |=
COFF::IMAGE_SCN_LNK_REMOVE | 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->getAliaseeObject();
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::NoDeduplicate:
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 {
StringRef Name = GO->getSection();
if (Name == getInstrProfSectionName(IPSK_covmap, Triple::COFF,
/*AddSegmentInfo=*/false) ||
Name == getInstrProfSectionName(IPSK_covfun, Triple::COFF,
/*AddSegmentInfo=*/false) ||
Name == getInstrProfSectionName(IPSK_covdata, Triple::COFF,
/*AddSegmentInfo=*/false) ||
Name == getInstrProfSectionName(IPSK_covname, Triple::COFF,
/*AddSegmentInfo=*/false))
Kind = SectionKind::getMetadata();
int Selection = 0;
unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
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);
}
static StringRef getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
if (Kind.isText())
return ".text";
if (Kind.isBSS())
return ".bss";
if (Kind.isThreadLocal())
return ".tls$";
if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
return ".rdata";
return ".data";
}
MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
// If we have -ffunction-sections then we should emit the global value to a
// uniqued section specifically for it.
bool EmitUniquedSection;
if (Kind.isText())
EmitUniquedSection = TM.getFunctionSections();
else
EmitUniquedSection = TM.getDataSections();
if ((EmitUniquedSection && !Kind.isCommon()) || GO->hasComdat()) {
SmallString<256> Name = getCOFFSectionNameForUniqueGlobal(Kind);
unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
int Selection = getSelectionForCOFF(GO);
if (!Selection)
Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
const GlobalValue *ComdatGV;
if (GO->hasComdat())
ComdatGV = getComdatGVForCOFF(GO);
else
ComdatGV = GO;
unsigned UniqueID = MCContext::GenericSectionID;
if (EmitUniquedSection)
UniqueID = NextUniqueID++;
if (!ComdatGV->hasPrivateLinkage()) {
MCSymbol *Sym = TM.getSymbol(ComdatGV);
StringRef COMDATSymName = Sym->getName();
if (const auto *F = dyn_cast<Function>(GO))
if (std::optional<StringRef> Prefix = F->getSectionPrefix())
raw_svector_ostream(Name) << '$' << *Prefix;
// Append "$symbol" to the section name *before* IR-level mangling is
// applied when targetting mingw. This is what GCC does, and the ld.bfd
// COFF linker will not properly handle comdats otherwise.
if (getContext().getTargetTriple().isWindowsGNUEnvironment())
raw_svector_ostream(Name) << '$' << ComdatGV->getName();
return getContext().getCOFFSection(Name, Characteristics, Kind,
COMDATSymName, Selection, UniqueID);
} else {
SmallString<256> TmpData;
getMangler().getNameWithPrefix(TmpData, GO, /*CannotUsePrivateLabel=*/true);
return getContext().getCOFFSection(Name, Characteristics, Kind, TmpData,
Selection, UniqueID);
}
}
if (Kind.isText())
return TextSection;
if (Kind.isThreadLocal())
return TLSDataSection;
if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
return ReadOnlySection;
// Note: we claim that common symbols are put in BSSSection, but they are
// really emitted with the magic .comm directive, which creates a symbol table
// entry but not a section.
if (Kind.isBSS() || Kind.isCommon())
return BSSSection;
return DataSection;
}
void TargetLoweringObjectFileCOFF::getNameWithPrefix(
SmallVectorImpl<char> &OutName, const GlobalValue *GV,
const TargetMachine &TM) const {
bool CannotUsePrivateLabel = false;
if (GV->hasPrivateLinkage() &&
((isa<Function>(GV) && TM.getFunctionSections()) ||
(isa<GlobalVariable>(GV) && TM.getDataSections())))
CannotUsePrivateLabel = true;
getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
}
MCSection *TargetLoweringObjectFileCOFF::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;
// FIXME: we should produce a symbol for F instead.
if (F.hasPrivateLinkage())
return ReadOnlySection;
MCSymbol *Sym = TM.getSymbol(&F);
StringRef COMDATSymName = Sym->getName();
SectionKind Kind = SectionKind::getReadOnly();
StringRef SecName = getCOFFSectionNameForUniqueGlobal(Kind);
unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
unsigned UniqueID = NextUniqueID++;
return getContext().getCOFFSection(
SecName, Characteristics, Kind, COMDATSymName,
COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE, UniqueID);
}
bool TargetLoweringObjectFileCOFF::shouldPutJumpTableInFunctionSection(
bool UsesLabelDifference, const Function &F) const {
if (TM->getTargetTriple().getArch() == Triple::x86_64) {
if (!JumpTableInFunctionSection) {
// We can always create relative relocations, so use another section
// that can be marked non-executable.
return false;
}
}
return TargetLoweringObjectFile::shouldPutJumpTableInFunctionSection(
UsesLabelDifference, F);
}
void TargetLoweringObjectFileCOFF::emitModuleMetadata(MCStreamer &Streamer,
Module &M) const {
emitLinkerDirectives(Streamer, M);
unsigned Version = 0;
unsigned Flags = 0;
StringRef Section;
GetObjCImageInfo(M, Version, Flags, Section);
if (!Section.empty()) {
auto &C = getContext();
auto *S = C.getCOFFSection(Section,
COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ,
SectionKind::getReadOnly());
Streamer.switchSection(S);
Streamer.emitLabel(C.getOrCreateSymbol(StringRef("OBJC_IMAGE_INFO")));
Streamer.emitInt32(Version);
Streamer.emitInt32(Flags);
Streamer.addBlankLine();
}
emitCGProfileMetadata(Streamer, M);
}
void TargetLoweringObjectFileCOFF::emitLinkerDirectives(
MCStreamer &Streamer, Module &M) const {
if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
// Emit the linker options to the linker .drectve section. According to the
// spec, this section is a space-separated string containing flags for
// linker.
MCSection *Sec = getDrectveSection();
Streamer.switchSection(Sec);
for (const auto *Option : LinkerOptions->operands()) {
for (const auto &Piece : cast<MDNode>(Option)->operands()) {
// Lead with a space for consistency with our dllexport implementation.
std::string Directive(" ");
Directive.append(std::string(cast<MDString>(Piece)->getString()));
Streamer.emitBytes(Directive);
}
}
}
// Emit /EXPORT: flags for each exported global as necessary.
std::string Flags;
for (const GlobalValue &GV : M.global_values()) {
raw_string_ostream OS(Flags);
emitLinkerFlagsForGlobalCOFF(OS, &GV, getContext().getTargetTriple(),
getMangler());
OS.flush();
if (!Flags.empty()) {
Streamer.switchSection(getDrectveSection());
Streamer.emitBytes(Flags);
}
Flags.clear();
}
// Emit /INCLUDE: flags for each used global as necessary.
if (const auto *LU = M.getNamedGlobal("llvm.used")) {
assert(LU->hasInitializer() && "expected llvm.used to have an initializer");
assert(isa<ArrayType>(LU->getValueType()) &&
"expected llvm.used to be an array type");
if (const auto *A = cast<ConstantArray>(LU->getInitializer())) {
for (const Value *Op : A->operands()) {
const auto *GV = cast<GlobalValue>(Op->stripPointerCasts());
// Global symbols with internal or private linkage are not visible to
// the linker, and thus would cause an error when the linker tried to
// preserve the symbol due to the `/include:` directive.
if (GV->hasLocalLinkage())
continue;
raw_string_ostream OS(Flags);
emitLinkerFlagsForUsedCOFF(OS, GV, getContext().getTargetTriple(),
getMangler());
OS.flush();
if (!Flags.empty()) {
Streamer.switchSection(getDrectveSection());
Streamer.emitBytes(Flags);
}
Flags.clear();
}
}
}
}
void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
const TargetMachine &TM) {
TargetLoweringObjectFile::Initialize(Ctx, TM);
this->TM = &TM;
const Triple &T = TM.getTargetTriple();
if (T.isWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
StaticCtorSection =
Ctx.getCOFFSection(".CRT$XCU", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ,
SectionKind::getReadOnly());
StaticDtorSection =
Ctx.getCOFFSection(".CRT$XTX", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ,
SectionKind::getReadOnly());
} else {
StaticCtorSection = Ctx.getCOFFSection(
".ctors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
SectionKind::getData());
StaticDtorSection = Ctx.getCOFFSection(
".dtors", COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ | COFF::IMAGE_SCN_MEM_WRITE,
SectionKind::getData());
}
}
static MCSectionCOFF *getCOFFStaticStructorSection(MCContext &Ctx,
const Triple &T, bool IsCtor,
unsigned Priority,
const MCSymbol *KeySym,
MCSectionCOFF *Default) {
if (T.isWindowsMSVCEnvironment() || T.isWindowsItaniumEnvironment()) {
// If the priority is the default, use .CRT$XCU, possibly associative.
if (Priority == 65535)
return Ctx.getAssociativeCOFFSection(Default, KeySym, 0);
// Otherwise, we need to compute a new section name. Low priorities should
// run earlier. The linker will sort sections ASCII-betically, and we need a
// string that sorts between .CRT$XCA and .CRT$XCU. In the general case, we
// make a name like ".CRT$XCT12345", since that runs before .CRT$XCU. Really
// low priorities need to sort before 'L', since the CRT uses that
// internally, so we use ".CRT$XCA00001" for them. We have a contract with
// the frontend that "init_seg(compiler)" corresponds to priority 200 and
// "init_seg(lib)" corresponds to priority 400, and those respectively use
// 'C' and 'L' without the priority suffix. Priorities between 200 and 400
// use 'C' with the priority as a suffix.
SmallString<24> Name;
char LastLetter = 'T';
bool AddPrioritySuffix = Priority != 200 && Priority != 400;
if (Priority < 200)
LastLetter = 'A';
else if (Priority < 400)
LastLetter = 'C';
else if (Priority == 400)
LastLetter = 'L';
raw_svector_ostream OS(Name);
OS << ".CRT$X" << (IsCtor ? "C" : "T") << LastLetter;
if (AddPrioritySuffix)
OS << format("%05u", Priority);
MCSectionCOFF *Sec = Ctx.getCOFFSection(
Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA | COFF::IMAGE_SCN_MEM_READ,
SectionKind::getReadOnly());
return Ctx.getAssociativeCOFFSection(Sec, KeySym, 0);
}
std::string Name = IsCtor ? ".ctors" : ".dtors";
if (Priority != 65535)
raw_string_ostream(Name) << format(".%05u", 65535 - Priority);
return Ctx.getAssociativeCOFFSection(
Ctx.getCOFFSection(Name, COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ |
COFF::IMAGE_SCN_MEM_WRITE,
SectionKind::getData()),
KeySym, 0);
}
MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
return getCOFFStaticStructorSection(
getContext(), getContext().getTargetTriple(), true, Priority, KeySym,
cast<MCSectionCOFF>(StaticCtorSection));
}
MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
return getCOFFStaticStructorSection(
getContext(), getContext().getTargetTriple(), false, Priority, KeySym,
cast<MCSectionCOFF>(StaticDtorSection));
}
const MCExpr *TargetLoweringObjectFileCOFF::lowerRelativeReference(
const GlobalValue *LHS, const GlobalValue *RHS,
const TargetMachine &TM) const {
const Triple &T = TM.getTargetTriple();
if (T.isOSCygMing())
return nullptr;
// Our symbols should exist in address space zero, cowardly no-op if
// otherwise.
if (LHS->getType()->getPointerAddressSpace() != 0 ||
RHS->getType()->getPointerAddressSpace() != 0)
return nullptr;
// Both ptrtoint instructions must wrap global objects:
// - Only global variables are eligible for image relative relocations.
// - The subtrahend refers to the special symbol __ImageBase, a GlobalVariable.
// We expect __ImageBase to be a global variable without a section, externally
// defined.
//
// It should look something like this: @__ImageBase = external constant i8
if (!isa<GlobalObject>(LHS) || !isa<GlobalVariable>(RHS) ||
LHS->isThreadLocal() || RHS->isThreadLocal() ||
RHS->getName() != "__ImageBase" || !RHS->hasExternalLinkage() ||
cast<GlobalVariable>(RHS)->hasInitializer() || RHS->hasSection())
return nullptr;
return MCSymbolRefExpr::create(TM.getSymbol(LHS),
MCSymbolRefExpr::VK_COFF_IMGREL32,
getContext());
}
static std::string APIntToHexString(const APInt &AI) {
unsigned Width = (AI.getBitWidth() / 8) * 2;
std::string HexString = toString(AI, 16, /*Signed=*/false);
llvm::transform(HexString, HexString.begin(), tolower);
unsigned Size = HexString.size();
assert(Width >= Size && "hex string is too large!");
HexString.insert(HexString.begin(), Width - Size, '0');
return HexString;
}
static std::string scalarConstantToHexString(const Constant *C) {
Type *Ty = C->getType();
if (isa<UndefValue>(C)) {
return APIntToHexString(APInt::getZero(Ty->getPrimitiveSizeInBits()));
} else if (const auto *CFP = dyn_cast<ConstantFP>(C)) {
return APIntToHexString(CFP->getValueAPF().bitcastToAPInt());
} else if (const auto *CI = dyn_cast<ConstantInt>(C)) {
return APIntToHexString(CI->getValue());
} else {
unsigned NumElements;
if (auto *VTy = dyn_cast<VectorType>(Ty))
NumElements = cast<FixedVectorType>(VTy)->getNumElements();
else
NumElements = Ty->getArrayNumElements();
std::string HexString;
for (int I = NumElements - 1, E = -1; I != E; --I)
HexString += scalarConstantToHexString(C->getAggregateElement(I));
return HexString;
}
}
MCSection *TargetLoweringObjectFileCOFF::getSectionForConstant(
const DataLayout &DL, SectionKind Kind, const Constant *C,
Align &Alignment) const {
if (Kind.isMergeableConst() && C &&
getContext().getAsmInfo()->hasCOFFComdatConstants()) {
// This creates comdat sections with the given symbol name, but unless
// AsmPrinter::GetCPISymbol actually makes the symbol global, the symbol
// will be created with a null storage class, which makes GNU binutils
// error out.
const unsigned Characteristics = COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ |
COFF::IMAGE_SCN_LNK_COMDAT;
std::string COMDATSymName;
if (Kind.isMergeableConst4()) {
if (Alignment <= 4) {
COMDATSymName = "__real@" + scalarConstantToHexString(C);
Alignment = Align(4);
}
} else if (Kind.isMergeableConst8()) {
if (Alignment <= 8) {
COMDATSymName = "__real@" + scalarConstantToHexString(C);
Alignment = Align(8);
}
} else if (Kind.isMergeableConst16()) {
// FIXME: These may not be appropriate for non-x86 architectures.
if (Alignment <= 16) {
COMDATSymName = "__xmm@" + scalarConstantToHexString(C);
Alignment = Align(16);
}
} else if (Kind.isMergeableConst32()) {
if (Alignment <= 32) {
COMDATSymName = "__ymm@" + scalarConstantToHexString(C);
Alignment = Align(32);
}
}
if (!COMDATSymName.empty())
return getContext().getCOFFSection(".rdata", Characteristics, Kind,
COMDATSymName,
COFF::IMAGE_COMDAT_SELECT_ANY);
}
return TargetLoweringObjectFile::getSectionForConstant(DL, Kind, C,
Alignment);
}
//===----------------------------------------------------------------------===//
// Wasm
//===----------------------------------------------------------------------===//
static const Comdat *getWasmComdat(const GlobalValue *GV) {
const Comdat *C = GV->getComdat();
if (!C)
return nullptr;
if (C->getSelectionKind() != Comdat::Any)
report_fatal_error("WebAssembly COMDATs only support "
"SelectionKind::Any, '" + C->getName() + "' cannot be "
"lowered.");
return C;
}
static unsigned getWasmSectionFlags(SectionKind K, bool Retain) {
unsigned Flags = 0;
if (K.isThreadLocal())
Flags |= wasm::WASM_SEG_FLAG_TLS;
if (K.isMergeableCString())
Flags |= wasm::WASM_SEG_FLAG_STRINGS;
if (Retain)
Flags |= wasm::WASM_SEG_FLAG_RETAIN;
// TODO(sbc): Add suport for K.isMergeableConst()
return Flags;
}
void TargetLoweringObjectFileWasm::getModuleMetadata(Module &M) {
SmallVector<GlobalValue *, 4> Vec;
collectUsedGlobalVariables(M, Vec, false);
for (GlobalValue *GV : Vec)
if (auto *GO = dyn_cast<GlobalObject>(GV))
Used.insert(GO);
}
MCSection *TargetLoweringObjectFileWasm::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
// We don't support explict section names for functions in the wasm object
// format. Each function has to be in its own unique section.
if (isa<Function>(GO)) {
return SelectSectionForGlobal(GO, Kind, TM);
}
StringRef Name = GO->getSection();
// Certain data sections we treat as named custom sections rather than
// segments within the data section.
// This could be avoided if all data segements (the wasm sense) were
// represented as their own sections (in the llvm sense).
// TODO(sbc): https://github.com/WebAssembly/tool-conventions/issues/138
if (Name == ".llvmcmd" || Name == ".llvmbc")
Kind = SectionKind::getMetadata();
StringRef Group = "";
if (const Comdat *C = getWasmComdat(GO)) {
Group = C->getName();
}
unsigned Flags = getWasmSectionFlags(Kind, Used.count(GO));
MCSectionWasm *Section = getContext().getWasmSection(
Name, Kind, Flags, Group, MCContext::GenericSectionID);
return Section;
}
static MCSectionWasm *
selectWasmSectionForGlobal(MCContext &Ctx, const GlobalObject *GO,
SectionKind Kind, Mangler &Mang,
const TargetMachine &TM, bool EmitUniqueSection,
unsigned *NextUniqueID, bool Retain) {
StringRef Group = "";
if (const Comdat *C = getWasmComdat(GO)) {
Group = C->getName();
}
bool UniqueSectionNames = TM.getUniqueSectionNames();
SmallString<128> Name = getSectionPrefixForGlobal(Kind, /*IsLarge=*/false);
if (const auto *F = dyn_cast<Function>(GO)) {
const auto &OptionalPrefix = F->getSectionPrefix();
if (OptionalPrefix)
raw_svector_ostream(Name) << '.' << *OptionalPrefix;
}
if (EmitUniqueSection && UniqueSectionNames) {
Name.push_back('.');
TM.getNameWithPrefix(Name, GO, Mang, true);
}
unsigned UniqueID = MCContext::GenericSectionID;
if (EmitUniqueSection && !UniqueSectionNames) {
UniqueID = *NextUniqueID;
(*NextUniqueID)++;
}
unsigned Flags = getWasmSectionFlags(Kind, Retain);
return Ctx.getWasmSection(Name, Kind, Flags, Group, UniqueID);
}
MCSection *TargetLoweringObjectFileWasm::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
if (Kind.isCommon())
report_fatal_error("mergable sections not supported yet on wasm");
// 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 (Kind.isText())
EmitUniqueSection = TM.getFunctionSections();
else
EmitUniqueSection = TM.getDataSections();
EmitUniqueSection |= GO->hasComdat();
bool Retain = Used.count(GO);
EmitUniqueSection |= Retain;
return selectWasmSectionForGlobal(getContext(), GO, Kind, getMangler(), TM,
EmitUniqueSection, &NextUniqueID, Retain);
}
bool TargetLoweringObjectFileWasm::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;
}
const MCExpr *TargetLoweringObjectFileWasm::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 correctness checks.
if (LHS->getType()->getPointerAddressSpace() != 0 ||
RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
RHS->isThreadLocal())
return nullptr;
return MCBinaryExpr::createSub(
MCSymbolRefExpr::create(TM.getSymbol(LHS), MCSymbolRefExpr::VK_None,
getContext()),
MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
}
void TargetLoweringObjectFileWasm::InitializeWasm() {
StaticCtorSection =
getContext().getWasmSection(".init_array", SectionKind::getData());
// We don't use PersonalityEncoding and LSDAEncoding because we don't emit
// .cfi directives. We use TTypeEncoding to encode typeinfo global variables.
TTypeEncoding = dwarf::DW_EH_PE_absptr;
}
MCSection *TargetLoweringObjectFileWasm::getStaticCtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
return Priority == UINT16_MAX ?
StaticCtorSection :
getContext().getWasmSection(".init_array." + utostr(Priority),
SectionKind::getData());
}
MCSection *TargetLoweringObjectFileWasm::getStaticDtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
report_fatal_error("@llvm.global_dtors should have been lowered already");
}
//===----------------------------------------------------------------------===//
// XCOFF
//===----------------------------------------------------------------------===//
bool TargetLoweringObjectFileXCOFF::ShouldEmitEHBlock(
const MachineFunction *MF) {
if (!MF->getLandingPads().empty())
return true;
const Function &F = MF->getFunction();
if (!F.hasPersonalityFn() || !F.needsUnwindTableEntry())
return false;
const GlobalValue *Per =
dyn_cast<GlobalValue>(F.getPersonalityFn()->stripPointerCasts());
assert(Per && "Personality routine is not a GlobalValue type.");
if (isNoOpWithoutInvoke(classifyEHPersonality(Per)))
return false;
return true;
}
bool TargetLoweringObjectFileXCOFF::ShouldSetSSPCanaryBitInTB(
const MachineFunction *MF) {
const Function &F = MF->getFunction();
if (!F.hasStackProtectorFnAttr())
return false;
// FIXME: check presence of canary word
// There are cases that the stack protectors are not really inserted even if
// the attributes are on.
return true;
}
MCSymbol *
TargetLoweringObjectFileXCOFF::getEHInfoTableSymbol(const MachineFunction *MF) {
MCSymbol *EHInfoSym = MF->getMMI().getContext().getOrCreateSymbol(
"__ehinfo." + Twine(MF->getFunctionNumber()));
cast<MCSymbolXCOFF>(EHInfoSym)->setEHInfo();
return EHInfoSym;
}
MCSymbol *
TargetLoweringObjectFileXCOFF::getTargetSymbol(const GlobalValue *GV,
const TargetMachine &TM) const {
// We always use a qualname symbol for a GV that represents
// a declaration, a function descriptor, or a common symbol.
// If a GV represents a GlobalVariable and -fdata-sections is enabled, we
// also return a qualname so that a label symbol could be avoided.
// It is inherently ambiguous when the GO represents the address of a
// function, as the GO could either represent a function descriptor or a
// function entry point. We choose to always return a function descriptor
// here.
if (const GlobalObject *GO = dyn_cast<GlobalObject>(GV)) {
if (GO->isDeclarationForLinker())
return cast<MCSectionXCOFF>(getSectionForExternalReference(GO, TM))
->getQualNameSymbol();
if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV))
if (GVar->hasAttribute("toc-data"))
return cast<MCSectionXCOFF>(
SectionForGlobal(GVar, SectionKind::getData(), TM))
->getQualNameSymbol();
SectionKind GOKind = getKindForGlobal(GO, TM);
if (GOKind.isText())
return cast<MCSectionXCOFF>(
getSectionForFunctionDescriptor(cast<Function>(GO), TM))
->getQualNameSymbol();
if ((TM.getDataSections() && !GO->hasSection()) || GO->hasCommonLinkage() ||
GOKind.isBSSLocal() || GOKind.isThreadBSSLocal())
return cast<MCSectionXCOFF>(SectionForGlobal(GO, GOKind, TM))
->getQualNameSymbol();
}
// For all other cases, fall back to getSymbol to return the unqualified name.
return nullptr;
}
MCSection *TargetLoweringObjectFileXCOFF::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
if (!GO->hasSection())
report_fatal_error("#pragma clang section is not yet supported");
StringRef SectionName = GO->getSection();
// Handle the XCOFF::TD case first, then deal with the rest.
if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GO))
if (GVar->hasAttribute("toc-data"))
return getContext().getXCOFFSection(
SectionName, Kind,
XCOFF::CsectProperties(/*MappingClass*/ XCOFF::XMC_TD, XCOFF::XTY_SD),
/* MultiSymbolsAllowed*/ true);
XCOFF::StorageMappingClass MappingClass;
if (Kind.isText())
MappingClass = XCOFF::XMC_PR;
else if (Kind.isData() || Kind.isBSS())
MappingClass = XCOFF::XMC_RW;
else if (Kind.isReadOnlyWithRel())
MappingClass =
TM.Options.XCOFFReadOnlyPointers ? XCOFF::XMC_RO : XCOFF::XMC_RW;
else if (Kind.isReadOnly())
MappingClass = XCOFF::XMC_RO;
else
report_fatal_error("XCOFF other section types not yet implemented.");
return getContext().getXCOFFSection(
SectionName, Kind, XCOFF::CsectProperties(MappingClass, XCOFF::XTY_SD),
/* MultiSymbolsAllowed*/ true);
}
MCSection *TargetLoweringObjectFileXCOFF::getSectionForExternalReference(
const GlobalObject *GO, const TargetMachine &TM) const {
assert(GO->isDeclarationForLinker() &&
"Tried to get ER section for a defined global.");
SmallString<128> Name;
getNameWithPrefix(Name, GO, TM);
// AIX TLS local-dynamic does not need the external reference for the
// "_$TLSML" symbol.
if (GO->getThreadLocalMode() == GlobalVariable::LocalDynamicTLSModel &&
GO->hasName() && GO->getName() == "_$TLSML") {
return getContext().getXCOFFSection(
Name, SectionKind::getData(),
XCOFF::CsectProperties(XCOFF::XMC_TC, XCOFF::XTY_SD));
}
XCOFF::StorageMappingClass SMC =
isa<Function>(GO) ? XCOFF::XMC_DS : XCOFF::XMC_UA;
if (GO->isThreadLocal())
SMC = XCOFF::XMC_UL;
if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GO))
if (GVar->hasAttribute("toc-data"))
SMC = XCOFF::XMC_TD;
// Externals go into a csect of type ER.
return getContext().getXCOFFSection(
Name, SectionKind::getMetadata(),
XCOFF::CsectProperties(SMC, XCOFF::XTY_ER));
}
MCSection *TargetLoweringObjectFileXCOFF::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
// Handle the XCOFF::TD case first, then deal with the rest.
if (const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GO))
if (GVar->hasAttribute("toc-data")) {
SmallString<128> Name;
getNameWithPrefix(Name, GO, TM);
XCOFF::SymbolType symType =
GO->hasCommonLinkage() ? XCOFF::XTY_CM : XCOFF::XTY_SD;
return getContext().getXCOFFSection(
Name, Kind, XCOFF::CsectProperties(XCOFF::XMC_TD, symType),
/* MultiSymbolsAllowed*/ true);
}
// Common symbols go into a csect with matching name which will get mapped
// into the .bss section.
// Zero-initialized local TLS symbols go into a csect with matching name which
// will get mapped into the .tbss section.
if (Kind.isBSSLocal() || GO->hasCommonLinkage() || Kind.isThreadBSSLocal()) {
SmallString<128> Name;
getNameWithPrefix(Name, GO, TM);
XCOFF::StorageMappingClass SMC = Kind.isBSSLocal() ? XCOFF::XMC_BS
: Kind.isCommon() ? XCOFF::XMC_RW
: XCOFF::XMC_UL;
return getContext().getXCOFFSection(
Name, Kind, XCOFF::CsectProperties(SMC, XCOFF::XTY_CM));
}
if (Kind.isText()) {
if (TM.getFunctionSections()) {
return cast<MCSymbolXCOFF>(getFunctionEntryPointSymbol(GO, TM))
->getRepresentedCsect();
}
return TextSection;
}
if (TM.Options.XCOFFReadOnlyPointers && Kind.isReadOnlyWithRel()) {
if (!TM.getDataSections())
report_fatal_error(
"ReadOnlyPointers is supported only if data sections is turned on");
SmallString<128> Name;
getNameWithPrefix(Name, GO, TM);
return getContext().getXCOFFSection(
Name, SectionKind::getReadOnly(),
XCOFF::CsectProperties(XCOFF::XMC_RO, XCOFF::XTY_SD));
}
// For BSS kind, zero initialized data must be emitted to the .data section
// because external linkage control sections that get mapped to the .bss
// section will be linked as tentative defintions, which is only appropriate
// for SectionKind::Common.
if (Kind.isData() || Kind.isReadOnlyWithRel() || Kind.isBSS()) {
if (TM.getDataSections()) {
SmallString<128> Name;
getNameWithPrefix(Name, GO, TM);
return getContext().getXCOFFSection(
Name, SectionKind::getData(),
XCOFF::CsectProperties(XCOFF::XMC_RW, XCOFF::XTY_SD));
}
return DataSection;
}
if (Kind.isReadOnly()) {
if (TM.getDataSections()) {
SmallString<128> Name;
getNameWithPrefix(Name, GO, TM);
return getContext().getXCOFFSection(
Name, SectionKind::getReadOnly(),
XCOFF::CsectProperties(XCOFF::XMC_RO, XCOFF::XTY_SD));
}
return ReadOnlySection;
}
// External/weak TLS data and initialized local TLS data are not eligible
// to be put into common csect. If data sections are enabled, thread
// data are emitted into separate sections. Otherwise, thread data
// are emitted into the .tdata section.
if (Kind.isThreadLocal()) {
if (TM.getDataSections()) {
SmallString<128> Name;
getNameWithPrefix(Name, GO, TM);
return getContext().getXCOFFSection(
Name, Kind, XCOFF::CsectProperties(XCOFF::XMC_TL, XCOFF::XTY_SD));
}
return TLSDataSection;
}
report_fatal_error("XCOFF other section types not yet implemented.");
}
MCSection *TargetLoweringObjectFileXCOFF::getSectionForJumpTable(
const Function &F, const TargetMachine &TM) const {
assert (!F.getComdat() && "Comdat not supported on XCOFF.");
if (!TM.getFunctionSections())
return ReadOnlySection;
// If the function can be removed, produce a unique section so that
// the table doesn't prevent the removal.
SmallString<128> NameStr(".rodata.jmp..");
getNameWithPrefix(NameStr, &F, TM);
return getContext().getXCOFFSection(
NameStr, SectionKind::getReadOnly(),
XCOFF::CsectProperties(XCOFF::XMC_RO, XCOFF::XTY_SD));
}
bool TargetLoweringObjectFileXCOFF::shouldPutJumpTableInFunctionSection(
bool UsesLabelDifference, const Function &F) const {
return false;
}
/// Given a mergeable constant with the specified size and relocation
/// information, return a section that it should be placed in.
MCSection *TargetLoweringObjectFileXCOFF::getSectionForConstant(
const DataLayout &DL, SectionKind Kind, const Constant *C,
Align &Alignment) const {
// TODO: Enable emiting constant pool to unique sections when we support it.
if (Alignment > Align(16))
report_fatal_error("Alignments greater than 16 not yet supported.");
if (Alignment == Align(8)) {
assert(ReadOnly8Section && "Section should always be initialized.");
return ReadOnly8Section;
}
if (Alignment == Align(16)) {
assert(ReadOnly16Section && "Section should always be initialized.");
return ReadOnly16Section;
}
return ReadOnlySection;
}
void TargetLoweringObjectFileXCOFF::Initialize(MCContext &Ctx,
const TargetMachine &TgtM) {
TargetLoweringObjectFile::Initialize(Ctx, TgtM);
TTypeEncoding =
dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_datarel |
(TgtM.getTargetTriple().isArch32Bit() ? dwarf::DW_EH_PE_sdata4
: dwarf::DW_EH_PE_sdata8);
PersonalityEncoding = 0;
LSDAEncoding = 0;
CallSiteEncoding = dwarf::DW_EH_PE_udata4;
// AIX debug for thread local location is not ready. And for integrated as
// mode, the relocatable address for the thread local variable will cause
// linker error. So disable the location attribute generation for thread local
// variables for now.
// FIXME: when TLS debug on AIX is ready, remove this setting.
SupportDebugThreadLocalLocation = false;
}
MCSection *TargetLoweringObjectFileXCOFF::getStaticCtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
report_fatal_error("no static constructor section on AIX");
}
MCSection *TargetLoweringObjectFileXCOFF::getStaticDtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
report_fatal_error("no static destructor section on AIX");
}
const MCExpr *TargetLoweringObjectFileXCOFF::lowerRelativeReference(
const GlobalValue *LHS, const GlobalValue *RHS,
const TargetMachine &TM) const {
/* Not implemented yet, but don't crash, return nullptr. */
return nullptr;
}
XCOFF::StorageClass
TargetLoweringObjectFileXCOFF::getStorageClassForGlobal(const GlobalValue *GV) {
assert(!isa<GlobalIFunc>(GV) && "GlobalIFunc is not supported on AIX.");
switch (GV->getLinkage()) {
case GlobalValue::InternalLinkage:
case GlobalValue::PrivateLinkage:
return XCOFF::C_HIDEXT;
case GlobalValue::ExternalLinkage:
case GlobalValue::CommonLinkage:
case GlobalValue::AvailableExternallyLinkage:
return XCOFF::C_EXT;
case GlobalValue::ExternalWeakLinkage:
case GlobalValue::LinkOnceAnyLinkage:
case GlobalValue::LinkOnceODRLinkage:
case GlobalValue::WeakAnyLinkage:
case GlobalValue::WeakODRLinkage:
return XCOFF::C_WEAKEXT;
case GlobalValue::AppendingLinkage:
report_fatal_error(
"There is no mapping that implements AppendingLinkage for XCOFF.");
}
llvm_unreachable("Unknown linkage type!");
}
MCSymbol *TargetLoweringObjectFileXCOFF::getFunctionEntryPointSymbol(
const GlobalValue *Func, const TargetMachine &TM) const {
assert((isa<Function>(Func) ||
(isa<GlobalAlias>(Func) &&
isa_and_nonnull<Function>(
cast<GlobalAlias>(Func)->getAliaseeObject()))) &&
"Func must be a function or an alias which has a function as base "
"object.");
SmallString<128> NameStr;
NameStr.push_back('.');
getNameWithPrefix(NameStr, Func, TM);
// When -function-sections is enabled and explicit section is not specified,
// it's not necessary to emit function entry point label any more. We will use
// function entry point csect instead. And for function delcarations, the
// undefined symbols gets treated as csect with XTY_ER property.
if (((TM.getFunctionSections() && !Func->hasSection()) ||
Func->isDeclarationForLinker()) &&
isa<Function>(Func)) {
return getContext()
.getXCOFFSection(
NameStr, SectionKind::getText(),
XCOFF::CsectProperties(XCOFF::XMC_PR, Func->isDeclarationForLinker()
? XCOFF::XTY_ER
: XCOFF::XTY_SD))
->getQualNameSymbol();
}
return getContext().getOrCreateSymbol(NameStr);
}
MCSection *TargetLoweringObjectFileXCOFF::getSectionForFunctionDescriptor(
const Function *F, const TargetMachine &TM) const {
SmallString<128> NameStr;
getNameWithPrefix(NameStr, F, TM);
return getContext().getXCOFFSection(
NameStr, SectionKind::getData(),
XCOFF::CsectProperties(XCOFF::XMC_DS, XCOFF::XTY_SD));
}
MCSection *TargetLoweringObjectFileXCOFF::getSectionForTOCEntry(
const MCSymbol *Sym, const TargetMachine &TM) const {
const XCOFF::StorageMappingClass SMC = [](const MCSymbol *Sym,
const TargetMachine &TM) {
const MCSymbolXCOFF *XSym = cast<MCSymbolXCOFF>(Sym);
// The "_$TLSML" symbol for TLS local-dynamic mode requires XMC_TC,
// otherwise the AIX assembler will complain.
if (XSym->getSymbolTableName() == "_$TLSML")
return XCOFF::XMC_TC;
// Use large code model toc entries for ehinfo symbols as they are
// never referenced directly. The runtime loads their TOC entry
// addresses from the trace-back table.
if (XSym->isEHInfo())
return XCOFF::XMC_TE;
// If the symbol does not have a code model specified use the module value.
if (!XSym->hasPerSymbolCodeModel())
return TM.getCodeModel() == CodeModel::Large ? XCOFF::XMC_TE
: XCOFF::XMC_TC;
return XSym->getPerSymbolCodeModel() == MCSymbolXCOFF::CM_Large
? XCOFF::XMC_TE
: XCOFF::XMC_TC;
}(Sym, TM);
return getContext().getXCOFFSection(
cast<MCSymbolXCOFF>(Sym)->getSymbolTableName(), SectionKind::getData(),
XCOFF::CsectProperties(SMC, XCOFF::XTY_SD));
}
MCSection *TargetLoweringObjectFileXCOFF::getSectionForLSDA(
const Function &F, const MCSymbol &FnSym, const TargetMachine &TM) const {
auto *LSDA = cast<MCSectionXCOFF>(LSDASection);
if (TM.getFunctionSections()) {
// If option -ffunction-sections is on, append the function name to the
// name of the LSDA csect so that each function has its own LSDA csect.
// This helps the linker to garbage-collect EH info of unused functions.
SmallString<128> NameStr = LSDA->getName();
raw_svector_ostream(NameStr) << '.' << F.getName();
LSDA = getContext().getXCOFFSection(NameStr, LSDA->getKind(),
LSDA->getCsectProp());
}
return LSDA;
}
//===----------------------------------------------------------------------===//
// GOFF
//===----------------------------------------------------------------------===//
TargetLoweringObjectFileGOFF::TargetLoweringObjectFileGOFF() = default;
MCSection *TargetLoweringObjectFileGOFF::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
return SelectSectionForGlobal(GO, Kind, TM);
}
MCSection *TargetLoweringObjectFileGOFF::getSectionForLSDA(
const Function &F, const MCSymbol &FnSym, const TargetMachine &TM) const {
std::string Name = ".gcc_exception_table." + F.getName().str();
return getContext().getGOFFSection(Name, SectionKind::getData(), nullptr,
nullptr);
}
MCSection *TargetLoweringObjectFileGOFF::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
auto *Symbol = TM.getSymbol(GO);
if (Kind.isBSS())
return getContext().getGOFFSection(Symbol->getName(), SectionKind::getBSS(),
nullptr, nullptr);
return getContext().getObjectFileInfo()->getTextSection();
}
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