RPCS3/llvm-mirror
1
0
Fork 0
mirror of https://github.com/RPCS3/llvm-mirror.git synced 2024-11-24 20:09:46 +00:00
Code Issues Actions Packages Projects Releases Wiki Activity
65570213eb
llvm-mirror/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
Fangrui Song 0c234a7fc0 [TargetLoweringObjectFileImpl] Make .llvmbc and .llvmcmd non-SHF_ALLOC 
There are two ways .llvmbc can be produced:

* clang -c -fembed-bitcode=all (which also produces .llvmcmd)
* LTO backend: ld.lld -mllvm -lto-embed-bitcode or -plugin-opt=-lto-embed-bitcode

.llvmbc and .llvmcmd have the SHF_ALLOC flag, so they can be dropped by
--gc-sections.

This patch sets SectionKind::Metadata to drop the SHF_ALLOC flag. This
is conceptually correct: the two sections are not part of the process
image, so SHF_ALLOC is not appropriate.

`test/LTO/X86/embed-bitcode.ll`: changed `llvm-objcopy -O binary --only-section` to
`llvm-objcopy --dump-section`. `-O binary` does not dump non-SHF_ALLOC sections.

Reviewed By: tejohnson

Differential Revision: https://reviews.llvm.org/D86374
2020-08-25 13:37:29 -07:00

2205 lines
82 KiB
C++
Raw Blame History

//===- llvm/CodeGen/TargetLoweringObjectFileImpl.cpp - Object File Info ---===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements classes used to handle lowerings specific to common
// object file formats.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/StringRef.h"
#include "llvm/ADT/Triple.h"
#include "llvm/BinaryFormat/COFF.h"
#include "llvm/BinaryFormat/Dwarf.h"
#include "llvm/BinaryFormat/ELF.h"
#include "llvm/BinaryFormat/MachO.h"
#include "llvm/CodeGen/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/Type.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSectionCOFF.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSectionWasm.h"
#include "llvm/MC/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/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 <cassert>
#include <string>
using namespace llvm;
using namespace dwarf;
static void GetObjCImageInfo(Module &M, unsigned &Version, unsigned &Flags,
StringRef &Section) {
SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
M.getModuleFlagsMetadata(ModuleFlags);
for (const auto &MFE: ModuleFlags) {
// Ignore flags with 'Require' behaviour.
if (MFE.Behavior == Module::Require)
continue;
StringRef Key = MFE.Key->getString();
if (Key == "Objective-C Image Info Version") {
Version = mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
} else if (Key == "Objective-C Garbage Collection" ||
Key == "Objective-C GC Only" ||
Key == "Objective-C Is Simulated" ||
Key == "Objective-C Class Properties" ||
Key == "Objective-C Image Swift Version") {
Flags |= mdconst::extract<ConstantInt>(MFE.Val)->getZExtValue();
} else if (Key == "Objective-C Image Info Section") {
Section = cast<MDString>(MFE.Val)->getString();
}
// 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
//===----------------------------------------------------------------------===//
void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
const TargetMachine &TgtM) {
TargetLoweringObjectFile::Initialize(Ctx, TgtM);
TM = &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
LLVM_FALLTHROUGH;
case Triple::ppc:
case Triple::x86:
PersonalityEncoding = isPositionIndependent()
? dwarf::DW_EH_PE_indirect |
dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4
: dwarf::DW_EH_PE_absptr;
LSDAEncoding = isPositionIndependent()
? dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4
: dwarf::DW_EH_PE_absptr;
TTypeEncoding = isPositionIndependent()
? dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4
: dwarf::DW_EH_PE_absptr;
break;
case Triple::x86_64:
if (isPositionIndependent()) {
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
((CM == CodeModel::Small || CM == CodeModel::Medium)
? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
LSDAEncoding = dwarf::DW_EH_PE_pcrel |
(CM == CodeModel::Small
? dwarf::DW_EH_PE_sdata4 : dwarf::DW_EH_PE_sdata8);
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
((CM == CodeModel::Small || CM == CodeModel::Medium)
? dwarf::DW_EH_PE_sdata8 : dwarf::DW_EH_PE_sdata4);
} else {
PersonalityEncoding =
(CM == CodeModel::Small || CM == CodeModel::Medium)
? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
LSDAEncoding = (CM == CodeModel::Small)
? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
TTypeEncoding = (CM == CodeModel::Small)
? dwarf::DW_EH_PE_udata4 : dwarf::DW_EH_PE_absptr;
}
break;
case Triple::hexagon:
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
LSDAEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
if (isPositionIndependent()) {
PersonalityEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
LSDAEncoding |= dwarf::DW_EH_PE_pcrel;
TTypeEncoding |= dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel;
}
break;
case Triple::aarch64:
case Triple::aarch64_be:
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.
if (isPositionIndependent()) {
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata8;
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata8;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata8;
} else {
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
LSDAEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
}
break;
case Triple::lanai:
LSDAEncoding = dwarf::DW_EH_PE_absptr;
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
break;
case Triple::mips:
case Triple::mipsel:
case Triple::mips64:
case Triple::mips64el:
// MIPS uses indirect pointer to refer personality functions and types, so
// that the eh_frame section can be read-only. DW.ref.personality will be
// generated for relocation.
PersonalityEncoding = dwarf::DW_EH_PE_indirect;
// FIXME: The N64 ABI probably ought to use DW_EH_PE_sdata8 but we can't
// identify N64 from just a triple.
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
// We don't support PC-relative LSDA references in GAS so we use the default
// DW_EH_PE_absptr for those.
// FreeBSD must be explicit about the data size and using pcrel since it's
// assembler/linker won't do the automatic conversion that the Linux tools
// do.
if (TgtM.getTargetTriple().isOSFreeBSD()) {
PersonalityEncoding |= dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
}
break;
case Triple::ppc64:
case Triple::ppc64le:
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_udata8;
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_udata8;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_udata8;
break;
case Triple::sparcel:
case Triple::sparc:
if (isPositionIndependent()) {
LSDAEncoding = dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
PersonalityEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
TTypeEncoding = dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel |
dwarf::DW_EH_PE_sdata4;
} else {
LSDAEncoding = dwarf::DW_EH_PE_absptr;
PersonalityEncoding = dwarf::DW_EH_PE_absptr;
TTypeEncoding = dwarf::DW_EH_PE_absptr;
}
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;
default:
break;
}
}
void TargetLoweringObjectFileELF::emitModuleMetadata(MCStreamer &Streamer,
Module &M) const {
auto &C = getContext();
if (NamedMDNode *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
auto *S = C.getELFSection(".linker-options", ELF::SHT_LLVM_LINKER_OPTIONS,
ELF::SHF_EXCLUDE);
Streamer.SwitchSection(S);
for (const auto *Operand : LinkerOptions->operands()) {
if (cast<MDNode>(Operand)->getNumOperands() != 2)
report_fatal_error("invalid llvm.linker.options");
for (const auto &Option : cast<MDNode>(Operand)->operands()) {
Streamer.emitBytes(cast<MDString>(Option)->getString());
Streamer.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);
}
}
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();
}
SmallVector<Module::ModuleFlagEntry, 8> ModuleFlags;
M.getModuleFlagsMetadata(ModuleFlags);
MDNode *CFGProfile = nullptr;
for (const auto &MFE : ModuleFlags) {
StringRef Key = MFE.Key->getString();
if (Key == "CG Profile") {
CFGProfile = cast<MDNode>(MFE.Val);
break;
}
}
if (!CFGProfile)
return;
auto GetSym = [this](const MDOperand &MDO) -> MCSymbol * {
if (!MDO)
return nullptr;
auto V = cast<ValueAsMetadata>(MDO);
const Function *F = cast<Function>(V->getValue());
return TM->getSymbol(F);
};
for (const auto &Edge : CFGProfile->operands()) {
MDNode *E = cast<MDNode>(Edge);
const MCSymbol *From = GetSym(E->getOperand(0));
const MCSymbol *To = GetSym(E->getOperand(1));
// Skip null functions. This can happen if functions are dead stripped after
// the CGProfile pass has been run.
if (!From || !To)
continue;
uint64_t Count = cast<ConstantAsMetadata>(E->getOperand(2))
->getValue()
->getUniqueInteger()
.getZExtValue();
Streamer.emitCGProfileEntry(
MCSymbolRefExpr::create(From, MCSymbolRefExpr::VK_None, C),
MCSymbolRefExpr::create(To, MCSymbolRefExpr::VK_None, C), Count);
}
}
MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
const GlobalValue *GV, const TargetMachine &TM,
MachineModuleInfo *MMI) const {
unsigned Encoding = getPersonalityEncoding();
if ((Encoding & 0x80) == DW_EH_PE_indirect)
return getContext().getOrCreateSymbol(StringRef("DW.ref.") +
TM.getSymbol(GV)->getName());
if ((Encoding & 0x70) == DW_EH_PE_absptr)
return TM.getSymbol(GV);
report_fatal_error("We do not support this DWARF encoding yet!");
}
void TargetLoweringObjectFileELF::emitPersonalityValue(
MCStreamer &Streamer, const DataLayout &DL, const MCSymbol *Sym) const {
SmallString<64> NameData("DW.ref.");
NameData += Sym->getName();
MCSymbolELF *Label =
cast<MCSymbolELF>(getContext().getOrCreateSymbol(NameData));
Streamer.emitSymbolAttribute(Label, MCSA_Hidden);
Streamer.emitSymbolAttribute(Label, MCSA_Weak);
unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
MCSection *Sec = getContext().getELFNamedSection(".data", Label->getName(),
ELF::SHT_PROGBITS, Flags, 0);
unsigned Size = DL.getPointerSize();
Streamer.SwitchSection(Sec);
Streamer.emitValueToAlignment(DL.getPointerABIAlignment(0).value());
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 == ".llvmbc" || Name == ".llvmcmd")
return SectionKind::getMetadata();
if (Name.empty() || Name[0] != '.') return K;
// Default implementation based on some magic section names.
if (Name == ".bss" ||
Name.startswith(".bss.") ||
Name.startswith(".gnu.linkonce.b.") ||
Name.startswith(".llvm.linkonce.b.") ||
Name == ".sbss" ||
Name.startswith(".sbss.") ||
Name.startswith(".gnu.linkonce.sb.") ||
Name.startswith(".llvm.linkonce.sb."))
return SectionKind::getBSS();
if (Name == ".tdata" ||
Name.startswith(".tdata.") ||
Name.startswith(".gnu.linkonce.td.") ||
Name.startswith(".llvm.linkonce.td."))
return SectionKind::getThreadData();
if (Name == ".tbss" ||
Name.startswith(".tbss.") ||
Name.startswith(".gnu.linkonce.tb.") ||
Name.startswith(".llvm.linkonce.tb."))
return SectionKind::getThreadBSS();
return K;
}
static unsigned getELFSectionType(StringRef Name, SectionKind K) {
// Use SHT_NOTE for section whose name starts with ".note" to allow
// emitting ELF notes from C variable declaration.
// See https://gcc.gnu.org/bugzilla/show_bug.cgi?id=77609
if (Name.startswith(".note"))
return ELF::SHT_NOTE;
if (Name == ".init_array")
return ELF::SHT_INIT_ARRAY;
if (Name == ".fini_array")
return ELF::SHT_FINI_ARRAY;
if (Name == ".preinit_array")
return ELF::SHT_PREINIT_ARRAY;
if (K.isBSS() || K.isThreadBSS())
return ELF::SHT_NOBITS;
return ELF::SHT_PROGBITS;
}
static unsigned getELFSectionFlags(SectionKind K) {
unsigned Flags = 0;
if (!K.isMetadata())
Flags |= ELF::SHF_ALLOC;
if (K.isText())
Flags |= ELF::SHF_EXECINSTR;
if (K.isExecuteOnly())
Flags |= ELF::SHF_ARM_PURECODE;
if (K.isWriteable())
Flags |= ELF::SHF_WRITE;
if (K.isThreadLocal())
Flags |= ELF::SHF_TLS;
if (K.isMergeableCString() || K.isMergeableConst())
Flags |= ELF::SHF_MERGE;
if (K.isMergeableCString())
Flags |= ELF::SHF_STRINGS;
return Flags;
}
static const Comdat *getELFComdat(const GlobalValue *GV) {
const Comdat *C = GV->getComdat();
if (!C)
return nullptr;
if (C->getSelectionKind() != Comdat::Any)
report_fatal_error("ELF COMDATs only support SelectionKind::Any, '" +
C->getName() + "' cannot be lowered.");
return C;
}
static const MCSymbolELF *getLinkedToSymbol(const GlobalObject *GO,
const TargetMachine &TM) {
MDNode *MD = GO->getMetadata(LLVMContext::MD_associated);
if (!MD)
return nullptr;
const MDOperand &Op = MD->getOperand(0);
if (!Op.get())
return nullptr;
auto *VM = dyn_cast<ValueAsMetadata>(Op);
if (!VM)
report_fatal_error("MD_associated operand is not ValueAsMetadata");
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) {
if (Kind.isText())
return ".text";
if (Kind.isReadOnly())
return ".rodata";
if (Kind.isBSS())
return ".bss";
if (Kind.isThreadData())
return ".tdata";
if (Kind.isThreadBSS())
return ".tbss";
if (Kind.isData())
return ".data";
if (Kind.isReadOnlyWithRel())
return ".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;
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));
std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
Name = SizeSpec + utostr(Alignment.value());
} else if (Kind.isMergeableConst()) {
Name = ".rodata.cst";
Name += utostr(EntrySize);
} else {
Name = getSectionPrefixForGlobal(Kind);
}
bool HasPrefix = false;
if (const auto *F = dyn_cast<Function>(GO)) {
if (Optional<StringRef> Prefix = F->getSectionPrefix()) {
Name += *Prefix;
HasPrefix = true;
}
}
if (UniqueSectionName) {
Name.push_back('.');
TM.getNameWithPrefix(Name, GO, Mang, /*MayAlwaysUsePrivate*/true);
} else if (HasPrefix)
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; }
};
}
MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
StringRef SectionName = GO->getSection();
// Check if '#pragma clang section' name is applicable.
// Note that pragma directive overrides -ffunction-section, -fdata-section
// and so section name is exactly as user specified and not uniqued.
const GlobalVariable *GV = dyn_cast<GlobalVariable>(GO);
if (GV && GV->hasImplicitSection()) {
auto Attrs = GV->getAttributes();
if (Attrs.hasAttribute("bss-section") && Kind.isBSS()) {
SectionName = Attrs.getAttribute("bss-section").getValueAsString();
} else if (Attrs.hasAttribute("rodata-section") && Kind.isReadOnly()) {
SectionName = Attrs.getAttribute("rodata-section").getValueAsString();
} else if (Attrs.hasAttribute("relro-section") && Kind.isReadOnlyWithRel()) {
SectionName = Attrs.getAttribute("relro-section").getValueAsString();
} else if (Attrs.hasAttribute("data-section") && Kind.isData()) {
SectionName = Attrs.getAttribute("data-section").getValueAsString();
}
}
const Function *F = dyn_cast<Function>(GO);
if (F && F->hasFnAttribute("implicit-section-name")) {
SectionName = F->getFnAttribute("implicit-section-name").getValueAsString();
}
// Infer section flags from the section name if we can.
Kind = getELFKindForNamedSection(SectionName, Kind);
StringRef Group = "";
unsigned Flags = getELFSectionFlags(Kind);
if (const Comdat *C = getELFComdat(GO)) {
Group = C->getName();
Flags |= ELF::SHF_GROUP;
}
unsigned EntrySize = getEntrySizeForKind(Kind);
// A section can have at most one associated section. Put each global with
// MD_associated in a unique section.
unsigned UniqueID = MCContext::GenericSectionID;
const MCSymbolELF *LinkedToSym = getLinkedToSymbol(GO, TM);
if (GO->getMetadata(LLVMContext::MD_associated)) {
UniqueID = NextUniqueID++;
Flags |= ELF::SHF_LINK_ORDER;
} else {
if (getContext().getAsmInfo()->useIntegratedAssembler()) {
// Symbols must be placed into sections with compatible entry
// sizes. Generate unique sections for symbols that have not
// been assigned to compatible sections.
if (Flags & ELF::SHF_MERGE) {
auto maybeID = getContext().getELFUniqueIDForEntsize(SectionName, Flags,
EntrySize);
if (maybeID)
UniqueID = *maybeID;
else {
// 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, getMangler(), TM, EntrySize, false);
if (!(getContext().isELFImplicitMergeableSectionNamePrefix(
SectionName) &&
SectionName.startswith(ImplicitSectionNameStem)))
UniqueID = NextUniqueID++;
}
} else {
// We need to unique the section if the user has explicity
// assigned a non-mergeable symbol to a section name for
// a generic mergeable section.
if (getContext().isELFGenericMergeableSection(SectionName)) {
auto maybeID = getContext().getELFUniqueIDForEntsize(
SectionName, Flags, EntrySize);
UniqueID = maybeID ? *maybeID : NextUniqueID++;
}
}
} else {
// 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).
Flags &= ~ELF::SHF_MERGE;
EntrySize = 0;
}
}
MCSectionELF *Section = getContext().getELFSection(
SectionName, getELFSectionType(SectionName, Kind), Flags,
EntrySize, Group, 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 (!getContext().getAsmInfo()->useIntegratedAssembler()) {
// If we are not using the integrated assembler 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;
}
static MCSectionELF *selectELFSectionForGlobal(
MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM, bool EmitUniqueSection, unsigned Flags,
unsigned *NextUniqueID, const MCSymbolELF *AssociatedSymbol) {
StringRef Group = "";
if (const Comdat *C = getELFComdat(GO)) {
Flags |= ELF::SHF_GROUP;
Group = C->getName();
}
// Get the section entry size based on the kind.
unsigned EntrySize = getEntrySizeForKind(Kind);
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, UniqueID, AssociatedSymbol);
}
MCSection *TargetLoweringObjectFileELF::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
unsigned Flags = getELFSectionFlags(Kind);
// If we have -ffunction-section or -fdata-section then we should emit the
// global value to a uniqued section specifically for it.
bool EmitUniqueSection = false;
if (!(Flags & ELF::SHF_MERGE) && !Kind.isCommon()) {
if (Kind.isText())
EmitUniqueSection = TM.getFunctionSections();
else
EmitUniqueSection = TM.getDataSections();
}
EmitUniqueSection |= GO->hasComdat();
const MCSymbolELF *LinkedToSym = getLinkedToSymbol(GO, TM);
if (LinkedToSym) {
EmitUniqueSection = true;
Flags |= ELF::SHF_LINK_ORDER;
}
MCSectionELF *Section = selectELFSectionForGlobal(
getContext(), GO, Kind, getMangler(), TM, EmitUniqueSection, Flags,
&NextUniqueID, LinkedToSym);
assert(Section->getLinkedToSymbol() == LinkedToSym);
return Section;
}
MCSection *TargetLoweringObjectFileELF::getSectionForJumpTable(
const Function &F, const TargetMachine &TM) const {
// If the function can be removed, produce a unique section so that
// the table doesn't prevent the removal.
const Comdat *C = F.getComdat();
bool EmitUniqueSection = TM.getFunctionSections() || C;
if (!EmitUniqueSection)
return ReadOnlySection;
return selectELFSectionForGlobal(getContext(), &F, SectionKind::getReadOnly(),
getMangler(), TM, EmitUniqueSection,
ELF::SHF_ALLOC, &NextUniqueID,
/* AssociatedSymbol */ nullptr);
}
bool TargetLoweringObjectFileELF::shouldPutJumpTableInFunctionSection(
bool UsesLabelDifference, const Function &F) const {
// We can always create relative relocations, so use another section
// that can be marked non-executable.
return false;
}
/// Given a mergeable constant with the specified size and relocation
/// information, return a section that it should be placed in.
MCSection *TargetLoweringObjectFileELF::getSectionForConstant(
const DataLayout &DL, SectionKind Kind, const Constant *C,
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.unlikely 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;
if (MBB.getSectionID() == MBBSectionID::ColdSectionID) {
Name += ".text.unlikely.";
Name += MBB.getParent()->getName();
} else if (MBB.getSectionID() == MBBSectionID::ExceptionSectionID) {
Name += ".text.eh.";
Name += MBB.getParent()->getName();
} else {
Name += MBB.getParent()->getSection()->getName();
if (TM.getUniqueBasicBlockSectionNames()) {
Name += ".";
Name += MBB.getSymbol()->getName();
} else {
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, 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);
}
MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
return getStaticStructorSection(getContext(), UseInitArray, true, Priority,
KeySym);
}
MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
return getStaticStructorSection(getContext(), UseInitArray, false, Priority,
KeySym);
}
const MCExpr *TargetLoweringObjectFileELF::lowerRelativeReference(
const GlobalValue *LHS, const GlobalValue *RHS,
const TargetMachine &TM) const {
// We may only use a PLT-relative relocation to refer to unnamed_addr
// functions.
if (!LHS->hasGlobalUnnamedAddr() || !LHS->getValueType()->isFunctionTy())
return nullptr;
// Basic sanity checks.
if (LHS->getType()->getPointerAddressSpace() != 0 ||
RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
RHS->isThreadLocal())
return nullptr;
return MCBinaryExpr::createSub(
MCSymbolRefExpr::create(TM.getSymbol(LHS), PLTRelativeVariantKind,
getContext()),
MCSymbolRefExpr::create(TM.getSymbol(RHS), getContext()), getContext());
}
MCSection *TargetLoweringObjectFileELF::getSectionForCommandLines() const {
// Use ".GCC.command.line" since this feature is to support clang's
// -frecord-gcc-switches which in turn attempts to mimic GCC's switch of the
// same name.
return getContext().getELFSection(".GCC.command.line", ELF::SHT_PROGBITS,
ELF::SHF_MERGE | ELF::SHF_STRINGS, 1, "");
}
void
TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
UseInitArray = UseInitArray_;
MCContext &Ctx = getContext();
if (!UseInitArray) {
StaticCtorSection = Ctx.getELFSection(".ctors", ELF::SHT_PROGBITS,
ELF::SHF_ALLOC | ELF::SHF_WRITE);
StaticDtorSection = Ctx.getELFSection(".dtors", ELF::SHT_PROGBITS,
ELF::SHF_ALLOC | ELF::SHF_WRITE);
return;
}
StaticCtorSection = Ctx.getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
ELF::SHF_WRITE | ELF::SHF_ALLOC);
StaticDtorSection = Ctx.getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
ELF::SHF_WRITE | ELF::SHF_ALLOC);
}
//===----------------------------------------------------------------------===//
// MachO
//===----------------------------------------------------------------------===//
TargetLoweringObjectFileMachO::TargetLoweringObjectFileMachO()
: TargetLoweringObjectFile() {
SupportIndirectSymViaGOTPCRel = true;
}
void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
const TargetMachine &TM) {
TargetLoweringObjectFile::Initialize(Ctx, TM);
if (TM.getRelocationModel() == Reloc::Static) {
StaticCtorSection = Ctx.getMachOSection("__TEXT", "__constructor", 0,
SectionKind::getData());
StaticDtorSection = Ctx.getMachOSection("__TEXT", "__destructor", 0,
SectionKind::getData());
} else {
StaticCtorSection = Ctx.getMachOSection("__DATA", "__mod_init_func",
MachO::S_MOD_INIT_FUNC_POINTERS,
SectionKind::getData());
StaticDtorSection = Ctx.getMachOSection("__DATA", "__mod_term_func",
MachO::S_MOD_TERM_FUNC_POINTERS,
SectionKind::getData());
}
PersonalityEncoding =
dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
LSDAEncoding = dwarf::DW_EH_PE_pcrel;
TTypeEncoding =
dwarf::DW_EH_PE_indirect | dwarf::DW_EH_PE_pcrel | dwarf::DW_EH_PE_sdata4;
}
void TargetLoweringObjectFileMachO::emitModuleMetadata(MCStreamer &Streamer,
Module &M) const {
// Emit the linker options if present.
if (auto *LinkerOptions = M.getNamedMetadata("llvm.linker.options")) {
for (const auto *Option : LinkerOptions->operands()) {
SmallVector<std::string, 4> StrOptions;
for (const auto &Piece : cast<MDNode>(Option)->operands())
StrOptions.push_back(std::string(cast<MDString>(Piece)->getString()));
Streamer.emitLinkerOptions(StrOptions);
}
}
unsigned VersionVal = 0;
unsigned ImageInfoFlags = 0;
StringRef SectionVal;
GetObjCImageInfo(M, VersionVal, ImageInfoFlags, SectionVal);
// The section is mandatory. If we don't have it, then we don't have GC info.
if (SectionVal.empty())
return;
StringRef Segment, Section;
unsigned TAA = 0, StubSize = 0;
bool TAAParsed;
std::string ErrorCode =
MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
TAA, TAAParsed, StubSize);
if (!ErrorCode.empty())
// If invalid, report the error with report_fatal_error.
report_fatal_error("Invalid section specifier '" + Section + "': " +
ErrorCode + ".");
// Get the section.
MCSectionMachO *S = getContext().getMachOSection(
Segment, Section, TAA, StubSize, SectionKind::getData());
Streamer.SwitchSection(S);
Streamer.emitLabel(getContext().
getOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
Streamer.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 {
// Parse the section specifier and create it if valid.
StringRef Segment, Section;
unsigned TAA = 0, StubSize = 0;
bool TAAParsed;
checkMachOComdat(GO);
std::string ErrorCode =
MCSectionMachO::ParseSectionSpecifier(GO->getSection(), Segment, Section,
TAA, TAAParsed, StubSize);
if (!ErrorCode.empty()) {
// If invalid, report the error with report_fatal_error.
report_fatal_error("Global variable '" + GO->getName() +
"' has an invalid section specifier '" +
GO->getSection() + "': " + ErrorCode + ".");
}
// Get the section.
MCSectionMachO *S =
getContext().getMachOSection(Segment, Section, TAA, StubSize, Kind);
// If TAA wasn't set by ParseSectionSpecifier() above,
// use the value returned by getMachOSection() as a default.
if (!TAAParsed)
TAA = S->getTypeAndAttributes();
// Okay, now that we got the section, verify that the TAA & StubSize agree.
// If the user declared multiple globals with different section flags, we need
// to reject it here.
if (S->getTypeAndAttributes() != TAA || S->getStubSize() != StubSize) {
// If invalid, report the error with report_fatal_error.
report_fatal_error("Global variable '" + GO->getName() +
"' section type or attributes does not match previous"
" section specifier");
}
return S;
}
MCSection *TargetLoweringObjectFileMachO::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
checkMachOComdat(GO);
// Handle thread local data.
if (Kind.isThreadBSS()) return TLSBSSSection;
if (Kind.isThreadData()) return TLSDataSection;
if (Kind.isText())
return GO->isWeakForLinker() ? TextCoalSection : TextSection;
// If this is weak/linkonce, put this in a coalescable section, either in text
// or data depending on if it is writable.
if (GO->isWeakForLinker()) {
if (Kind.isReadOnly())
return ConstTextCoalSection;
if (Kind.isReadOnlyWithRel())
return ConstDataCoalSection;
return DataCoalSection;
}
// FIXME: Alignment check should be handled by section classifier.
if (Kind.isMergeable1ByteCString() &&
GO->getParent()->getDataLayout().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
}
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;
// If it is not dead stripped, it is safe to use private labels.
const MCSectionMachO &SMO = cast<MCSectionMachO>(Section);
if (SMO.hasAttribute(MachO::S_ATTR_NO_DEAD_STRIP))
return true;
return false;
}
void TargetLoweringObjectFileMachO::getNameWithPrefix(
SmallVectorImpl<char> &OutName, const GlobalValue *GV,
const TargetMachine &TM) const {
bool CannotUsePrivateLabel = true;
if (auto *GO = GV->getBaseObject()) {
SectionKind GOKind = TargetLoweringObjectFile::getKindForGlobal(GO, TM);
const MCSection *TheSection = SectionForGlobal(GO, GOKind, TM);
CannotUsePrivateLabel =
!canUsePrivateLabel(*TM.getMCAsmInfo(), *TheSection);
}
getMangler().getNameWithPrefix(OutName, GV, CannotUsePrivateLabel);
}
//===----------------------------------------------------------------------===//
// COFF
//===----------------------------------------------------------------------===//
static unsigned
getCOFFSectionFlags(SectionKind K, const TargetMachine &TM) {
unsigned Flags = 0;
bool isThumb = TM.getTargetTriple().getArch() == Triple::thumb;
if (K.isMetadata())
Flags |=
COFF::IMAGE_SCN_MEM_DISCARDABLE;
else if (K.isText())
Flags |=
COFF::IMAGE_SCN_MEM_EXECUTE |
COFF::IMAGE_SCN_MEM_READ |
COFF::IMAGE_SCN_CNT_CODE |
(isThumb ? COFF::IMAGE_SCN_MEM_16BIT : (COFF::SectionCharacteristics)0);
else if (K.isBSS())
Flags |=
COFF::IMAGE_SCN_CNT_UNINITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ |
COFF::IMAGE_SCN_MEM_WRITE;
else if (K.isThreadLocal())
Flags |=
COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ |
COFF::IMAGE_SCN_MEM_WRITE;
else if (K.isReadOnly() || K.isReadOnlyWithRel())
Flags |=
COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ;
else if (K.isWriteable())
Flags |=
COFF::IMAGE_SCN_CNT_INITIALIZED_DATA |
COFF::IMAGE_SCN_MEM_READ |
COFF::IMAGE_SCN_MEM_WRITE;
return Flags;
}
static const GlobalValue *getComdatGVForCOFF(const GlobalValue *GV) {
const Comdat *C = GV->getComdat();
assert(C && "expected GV to have a Comdat!");
StringRef ComdatGVName = C->getName();
const GlobalValue *ComdatGV = GV->getParent()->getNamedValue(ComdatGVName);
if (!ComdatGV)
report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
"' does not exist.");
if (ComdatGV->getComdat() != C)
report_fatal_error("Associative COMDAT symbol '" + ComdatGVName +
"' is not a key for its COMDAT.");
return ComdatGV;
}
static int getSelectionForCOFF(const GlobalValue *GV) {
if (const Comdat *C = GV->getComdat()) {
const GlobalValue *ComdatKey = getComdatGVForCOFF(GV);
if (const auto *GA = dyn_cast<GlobalAlias>(ComdatKey))
ComdatKey = GA->getBaseObject();
if (ComdatKey == GV) {
switch (C->getSelectionKind()) {
case Comdat::Any:
return COFF::IMAGE_COMDAT_SELECT_ANY;
case Comdat::ExactMatch:
return COFF::IMAGE_COMDAT_SELECT_EXACT_MATCH;
case Comdat::Largest:
return COFF::IMAGE_COMDAT_SELECT_LARGEST;
case Comdat::NoDuplicates:
return COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
case Comdat::SameSize:
return COFF::IMAGE_COMDAT_SELECT_SAME_SIZE;
}
} else {
return COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE;
}
}
return 0;
}
MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
int Selection = 0;
unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
StringRef Name = GO->getSection();
StringRef COMDATSymName = "";
if (GO->hasComdat()) {
Selection = getSelectionForCOFF(GO);
const GlobalValue *ComdatGV;
if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
ComdatGV = getComdatGVForCOFF(GO);
else
ComdatGV = GO;
if (!ComdatGV->hasPrivateLinkage()) {
MCSymbol *Sym = TM.getSymbol(ComdatGV);
COMDATSymName = Sym->getName();
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
} else {
Selection = 0;
}
}
return getContext().getCOFFSection(Name, Characteristics, Kind, COMDATSymName,
Selection);
}
static StringRef getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
if (Kind.isText())
return ".text";
if (Kind.isBSS())
return ".bss";
if (Kind.isThreadLocal())
return ".tls$";
if (Kind.isReadOnly() || Kind.isReadOnlyWithRel())
return ".rdata";
return ".data";
}
MCSection *TargetLoweringObjectFileCOFF::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
// If we have -ffunction-sections then we should emit the global value to a
// uniqued section specifically for it.
bool EmitUniquedSection;
if (Kind.isText())
EmitUniquedSection = TM.getFunctionSections();
else
EmitUniquedSection = TM.getDataSections();
if ((EmitUniquedSection && !Kind.isCommon()) || GO->hasComdat()) {
SmallString<256> Name = getCOFFSectionNameForUniqueGlobal(Kind);
unsigned Characteristics = getCOFFSectionFlags(Kind, TM);
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
int Selection = getSelectionForCOFF(GO);
if (!Selection)
Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
const GlobalValue *ComdatGV;
if (GO->hasComdat())
ComdatGV = getComdatGVForCOFF(GO);
else
ComdatGV = GO;
unsigned UniqueID = MCContext::GenericSectionID;
if (EmitUniquedSection)
UniqueID = NextUniqueID++;
if (!ComdatGV->hasPrivateLinkage()) {
MCSymbol *Sym = TM.getSymbol(ComdatGV);
StringRef COMDATSymName = Sym->getName();
// Append "$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 (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);
}
void TargetLoweringObjectFileCOFF::emitModuleMetadata(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);
}
}
}
unsigned Version = 0;
unsigned Flags = 0;
StringRef Section;
GetObjCImageInfo(M, Version, Flags, Section);
if (Section.empty())
return;
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();
}
void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
const TargetMachine &TM) {
TargetLoweringObjectFile::Initialize(Ctx, 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$XCA00001" for them.
SmallString<24> Name;
raw_svector_ostream OS(Name);
OS << ".CRT$X" << (IsCtor ? "C" : "T") <<
(Priority < 200 ? 'A' : 'T') << 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(), getTargetTriple(), true,
Priority, KeySym,
cast<MCSectionCOFF>(StaticCtorSection));
}
MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
return getCOFFStaticStructorSection(getContext(), getTargetTriple(), false,
Priority, KeySym,
cast<MCSectionCOFF>(StaticDtorSection));
}
void TargetLoweringObjectFileCOFF::emitLinkerFlagsForGlobal(
raw_ostream &OS, const GlobalValue *GV) const {
emitLinkerFlagsForGlobalCOFF(OS, GV, getTargetTriple(), getMangler());
}
void TargetLoweringObjectFileCOFF::emitLinkerFlagsForUsed(
raw_ostream &OS, const GlobalValue *GV) const {
emitLinkerFlagsForUsedCOFF(OS, GV, getTargetTriple(), getMangler());
}
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 = AI.toString(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::getNullValue(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;
}
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();
}
MCSectionWasm* Section =
getContext().getWasmSection(Name, Kind, Group,
MCContext::GenericSectionID);
return Section;
}
static MCSectionWasm *selectWasmSectionForGlobal(
MCContext &Ctx, const GlobalObject *GO, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM, bool EmitUniqueSection, unsigned *NextUniqueID) {
StringRef Group = "";
if (const Comdat *C = getWasmComdat(GO)) {
Group = C->getName();
}
bool UniqueSectionNames = TM.getUniqueSectionNames();
SmallString<128> Name = getSectionPrefixForGlobal(Kind);
if (const auto *F = dyn_cast<Function>(GO)) {
const auto &OptionalPrefix = F->getSectionPrefix();
if (OptionalPrefix)
Name += *OptionalPrefix;
}
if (EmitUniqueSection && UniqueSectionNames) {
Name.push_back('.');
TM.getNameWithPrefix(Name, GO, Mang, true);
}
unsigned UniqueID = MCContext::GenericSectionID;
if (EmitUniqueSection && !UniqueSectionNames) {
UniqueID = *NextUniqueID;
(*NextUniqueID)++;
}
return Ctx.getWasmSection(Name, Kind, 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();
return selectWasmSectionForGlobal(getContext(), GO, Kind, getMangler(), TM,
EmitUniqueSection, &NextUniqueID);
}
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 sanity checks.
if (LHS->getType()->getPointerAddressSpace() != 0 ||
RHS->getType()->getPointerAddressSpace() != 0 || LHS->isThreadLocal() ||
RHS->isThreadLocal())
return nullptr;
return MCBinaryExpr::createSub(
MCSymbolRefExpr::create(TM.getSymbol(LHS), 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 {
llvm_unreachable("@llvm.global_dtors should have been lowered already");
return nullptr;
}
//===----------------------------------------------------------------------===//
// XCOFF
//===----------------------------------------------------------------------===//
MCSymbol *
TargetLoweringObjectFileXCOFF::getTargetSymbol(const GlobalValue *GV,
const TargetMachine &TM) const {
if (TM.getDataSections())
report_fatal_error("XCOFF unique data sections not yet implemented");
// We always use a qualname symbol for a GV that represents
// a declaration, a function descriptor, or a common symbol.
// 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();
SectionKind GOKind = getKindForGlobal(GO, TM);
if (GOKind.isText())
return cast<MCSectionXCOFF>(
getSectionForFunctionDescriptor(cast<Function>(GO), TM))
->getQualNameSymbol();
if (GOKind.isCommon() || GOKind.isBSSLocal())
return cast<MCSectionXCOFF>(SectionForGlobal(GO, GOKind, TM))
->getQualNameSymbol();
}
// For all other cases, fall back to getSymbol to return the unqualified name.
// This could change for a GV that is a GlobalVariable when we decide to
// support -fdata-sections since we could avoid having label symbols if the
// linkage name is applied to the csect symbol.
return nullptr;
}
MCSection *TargetLoweringObjectFileXCOFF::getExplicitSectionGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
report_fatal_error("XCOFF explicit sections not yet implemented.");
}
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);
// Externals go into a csect of type ER.
return getContext().getXCOFFSection(
Name, isa<Function>(GO) ? XCOFF::XMC_DS : XCOFF::XMC_UA, XCOFF::XTY_ER,
SectionKind::getMetadata());
}
MCSection *TargetLoweringObjectFileXCOFF::SelectSectionForGlobal(
const GlobalObject *GO, SectionKind Kind, const TargetMachine &TM) const {
assert(!TM.getDataSections() &&
"XCOFF unique data sections not yet implemented.");
// Common symbols go into a csect with matching name which will get mapped
// into the .bss section.
if (Kind.isBSSLocal() || Kind.isCommon()) {
SmallString<128> Name;
getNameWithPrefix(Name, GO, TM);
return getContext().getXCOFFSection(
Name, Kind.isBSSLocal() ? XCOFF::XMC_BS : XCOFF::XMC_RW, XCOFF::XTY_CM,
Kind, /* BeginSymbolName */ nullptr);
}
if (Kind.isMergeableCString()) {
Align Alignment = GO->getParent()->getDataLayout().getPreferredAlign(
cast<GlobalVariable>(GO));
unsigned EntrySize = getEntrySizeForKind(Kind);
std::string SizeSpec = ".rodata.str" + utostr(EntrySize) + ".";
SmallString<128> Name;
Name = SizeSpec + utostr(Alignment.value());
return getContext().getXCOFFSection(Name, XCOFF::XMC_RO, XCOFF::XTY_SD,
Kind, /*BeginSymbolName*/ nullptr);
}
if (Kind.isText()) {
if (TM.getFunctionSections()) {
return cast<MCSymbolXCOFF>(getFunctionEntryPointSymbol(GO, TM))
->getRepresentedCsect();
}
return TextSection;
}
if (Kind.isData() || Kind.isReadOnlyWithRel())
// TODO: We may put this under option control, because user may want to
// have read-only data with relocations placed into a read-only section by
// the compiler.
return DataSection;
// 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.isBSS())
return DataSection;
if (Kind.isReadOnly())
return ReadOnlySection;
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, XCOFF::XMC_RO, XCOFF::XTY_SD,
SectionKind::getReadOnly());
}
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.
return ReadOnlySection;
}
void TargetLoweringObjectFileXCOFF::Initialize(MCContext &Ctx,
const TargetMachine &TgtM) {
TargetLoweringObjectFile::Initialize(Ctx, TgtM);
TTypeEncoding = 0;
PersonalityEncoding = 0;
LSDAEncoding = 0;
}
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 {
report_fatal_error("XCOFF not yet implemented.");
}
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)->getBaseObject()))) &&
"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, 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->isDeclaration()) &&
isa<Function>(Func)) {
return cast<MCSectionXCOFF>(
getContext().getXCOFFSection(
NameStr, XCOFF::XMC_PR,
Func->isDeclaration() ? XCOFF::XTY_ER : XCOFF::XTY_SD,
SectionKind::getText()))
->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, XCOFF::XMC_DS, XCOFF::XTY_SD,
SectionKind::getData());
}
MCSection *TargetLoweringObjectFileXCOFF::getSectionForTOCEntry(
const MCSymbol *Sym, const TargetMachine &TM) const {
// Use TE storage-mapping class when large code model is enabled so that
// the chance of needing -bbigtoc is decreased.
return getContext().getXCOFFSection(
cast<MCSymbolXCOFF>(Sym)->getSymbolTableName(),
TM.getCodeModel() == CodeModel::Large ? XCOFF::XMC_TE : XCOFF::XMC_TC,
XCOFF::XTY_SD, SectionKind::getData());
}
Reference in New Issue View Git Blame Copy Permalink