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llvm-6502/lib/CodeGen/TargetLoweringObjectFileImpl.cpp
David Majnemer 38d8be1ad8 CodeGen: Stick constant pool entries in COMDAT sections for WinCOFF 
COFF lacks a feature that other object file formats support: mergeable
sections.

To work around this, MSVC sticks constant pool entries in special COMDAT
sections so that each constant is in it's own section.  This permits
unused constants to be dropped and it also allows duplicate constants in
different translation units to get merged together.

This fixes PR20262.

Differential Revision: http://reviews.llvm.org/D4482

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@213006 91177308-0d34-0410-b5e6-96231b3b80d8
2014-07-14 22:57:27 +00:00

989 lines
35 KiB
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//===-- llvm/CodeGen/TargetLoweringObjectFileImpl.cpp - Object File Info --===//
//
// The LLVM Compiler Infrastructure
//
// This file is distributed under the University of Illinois Open Source
// License. See LICENSE.TXT for details.
//
//===----------------------------------------------------------------------===//
//
// This file implements classes used to handle lowerings specific to common
// object file formats.
//
//===----------------------------------------------------------------------===//
#include "llvm/CodeGen/TargetLoweringObjectFileImpl.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
#include "llvm/ADT/Triple.h"
#include "llvm/CodeGen/MachineModuleInfoImpls.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/DerivedTypes.h"
#include "llvm/IR/Function.h"
#include "llvm/IR/GlobalVariable.h"
#include "llvm/IR/Mangler.h"
#include "llvm/IR/Module.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/MCStreamer.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/Dwarf.h"
#include "llvm/Support/ELF.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetLowering.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;
using namespace dwarf;
//===----------------------------------------------------------------------===//
// ELF
//===----------------------------------------------------------------------===//
MCSymbol *TargetLoweringObjectFileELF::getCFIPersonalitySymbol(
const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
MachineModuleInfo *MMI) const {
unsigned Encoding = getPersonalityEncoding();
if ((Encoding & 0x80) == dwarf::DW_EH_PE_indirect)
return getContext().GetOrCreateSymbol(StringRef("DW.ref.") +
TM.getSymbol(GV, Mang)->getName());
if ((Encoding & 0x70) == dwarf::DW_EH_PE_absptr)
return TM.getSymbol(GV, Mang);
report_fatal_error("We do not support this DWARF encoding yet!");
}
void TargetLoweringObjectFileELF::emitPersonalityValue(MCStreamer &Streamer,
const TargetMachine &TM,
const MCSymbol *Sym) const {
SmallString<64> NameData("DW.ref.");
NameData += Sym->getName();
MCSymbol *Label = getContext().GetOrCreateSymbol(NameData);
Streamer.EmitSymbolAttribute(Label, MCSA_Hidden);
Streamer.EmitSymbolAttribute(Label, MCSA_Weak);
StringRef Prefix = ".data.";
NameData.insert(NameData.begin(), Prefix.begin(), Prefix.end());
unsigned Flags = ELF::SHF_ALLOC | ELF::SHF_WRITE | ELF::SHF_GROUP;
const MCSection *Sec = getContext().getELFSection(NameData,
ELF::SHT_PROGBITS,
Flags,
SectionKind::getDataRel(),
0, Label->getName());
unsigned Size = TM.getDataLayout()->getPointerSize();
Streamer.SwitchSection(Sec);
Streamer.EmitValueToAlignment(TM.getDataLayout()->getPointerABIAlignment());
Streamer.EmitSymbolAttribute(Label, MCSA_ELF_TypeObject);
const MCExpr *E = MCConstantExpr::Create(Size, getContext());
Streamer.EmitELFSize(Label, E);
Streamer.EmitLabel(Label);
Streamer.EmitSymbolValue(Sym, Size);
}
const MCExpr *TargetLoweringObjectFileELF::getTTypeGlobalReference(
const GlobalValue *GV, unsigned Encoding, Mangler &Mang,
const TargetMachine &TM, MachineModuleInfo *MMI,
MCStreamer &Streamer) const {
if (Encoding & dwarf::DW_EH_PE_indirect) {
MachineModuleInfoELF &ELFMMI = MMI->getObjFileInfo<MachineModuleInfoELF>();
MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, ".DW.stub", Mang, 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, Mang);
StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
}
return TargetLoweringObjectFile::
getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
}
return TargetLoweringObjectFile::
getTTypeGlobalReference(GV, Encoding, Mang, TM, MMI, Streamer);
}
static SectionKind
getELFKindForNamedSection(StringRef Name, SectionKind K) {
// N.B.: The defaults used in here are no the same ones used in MC.
// We follow gcc, MC follows gas. For example, given ".section .eh_frame",
// both gas and MC will produce a section with no flags. Given
// section(".eh_frame") gcc will produce:
//
// .section .eh_frame,"a",@progbits
if (Name.empty() || Name[0] != '.') return K;
// Some lame default implementation based on some magic section names.
if (Name == ".bss" ||
Name.startswith(".bss.") ||
Name.startswith(".gnu.linkonce.b.") ||
Name.startswith(".llvm.linkonce.b.") ||
Name == ".sbss" ||
Name.startswith(".sbss.") ||
Name.startswith(".gnu.linkonce.sb.") ||
Name.startswith(".llvm.linkonce.sb."))
return SectionKind::getBSS();
if (Name == ".tdata" ||
Name.startswith(".tdata.") ||
Name.startswith(".gnu.linkonce.td.") ||
Name.startswith(".llvm.linkonce.td."))
return SectionKind::getThreadData();
if (Name == ".tbss" ||
Name.startswith(".tbss.") ||
Name.startswith(".gnu.linkonce.tb.") ||
Name.startswith(".llvm.linkonce.tb."))
return SectionKind::getThreadBSS();
return K;
}
static unsigned getELFSectionType(StringRef Name, SectionKind K) {
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.isWriteable())
Flags |= ELF::SHF_WRITE;
if (K.isThreadLocal())
Flags |= ELF::SHF_TLS;
// K.isMergeableConst() is left out to honour PR4650
if (K.isMergeableCString() || K.isMergeableConst4() ||
K.isMergeableConst8() || K.isMergeableConst16())
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;
}
const MCSection *TargetLoweringObjectFileELF::getExplicitSectionGlobal(
const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM) const {
StringRef SectionName = GV->getSection();
// Infer section flags from the section name if we can.
Kind = getELFKindForNamedSection(SectionName, Kind);
StringRef Group = "";
unsigned Flags = getELFSectionFlags(Kind);
if (const Comdat *C = getELFComdat(GV)) {
Group = C->getName();
Flags |= ELF::SHF_GROUP;
}
return getContext().getELFSection(SectionName,
getELFSectionType(SectionName, Kind), Flags,
Kind, /*EntrySize=*/0, Group);
}
/// getSectionPrefixForGlobal - 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.isDataNoRel()) return ".data.";
if (Kind.isDataRelLocal()) return ".data.rel.local.";
if (Kind.isDataRel()) return ".data.rel.";
if (Kind.isReadOnlyWithRelLocal()) return ".data.rel.ro.local.";
assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
return ".data.rel.ro.";
}
const MCSection *TargetLoweringObjectFileELF::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
// If we have -ffunction-section or -fdata-section 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 this global is linkonce/weak and the target handles this by emitting it
// into a 'uniqued' section name, create and return the section now.
if ((GV->isWeakForLinker() || EmitUniquedSection || GV->hasComdat()) &&
!Kind.isCommon()) {
StringRef Prefix = getSectionPrefixForGlobal(Kind);
SmallString<128> Name(Prefix);
TM.getNameWithPrefix(Name, GV, Mang, true);
StringRef Group = "";
unsigned Flags = getELFSectionFlags(Kind);
if (GV->isWeakForLinker() || GV->hasComdat()) {
if (const Comdat *C = getELFComdat(GV))
Group = C->getName();
else
Group = Name.substr(Prefix.size());
Flags |= ELF::SHF_GROUP;
}
return getContext().getELFSection(Name.str(),
getELFSectionType(Name.str(), Kind),
Flags, Kind, 0, Group);
}
if (Kind.isText()) return TextSection;
if (Kind.isMergeable1ByteCString() ||
Kind.isMergeable2ByteCString() ||
Kind.isMergeable4ByteCString()) {
// We also need alignment here.
// FIXME: this is getting the alignment of the character, not the
// alignment of the global!
unsigned Align =
TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV));
const char *SizeSpec = ".rodata.str1.";
if (Kind.isMergeable2ByteCString())
SizeSpec = ".rodata.str2.";
else if (Kind.isMergeable4ByteCString())
SizeSpec = ".rodata.str4.";
else
assert(Kind.isMergeable1ByteCString() && "unknown string width");
std::string Name = SizeSpec + utostr(Align);
return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
ELF::SHF_ALLOC |
ELF::SHF_MERGE |
ELF::SHF_STRINGS,
Kind);
}
if (Kind.isMergeableConst()) {
if (Kind.isMergeableConst4() && MergeableConst4Section)
return MergeableConst4Section;
if (Kind.isMergeableConst8() && MergeableConst8Section)
return MergeableConst8Section;
if (Kind.isMergeableConst16() && MergeableConst16Section)
return MergeableConst16Section;
return ReadOnlySection; // .const
}
if (Kind.isReadOnly()) return ReadOnlySection;
if (Kind.isThreadData()) return TLSDataSection;
if (Kind.isThreadBSS()) return TLSBSSSection;
// 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;
if (Kind.isDataNoRel()) return DataSection;
if (Kind.isDataRelLocal()) return DataRelLocalSection;
if (Kind.isDataRel()) return DataRelSection;
if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
return DataRelROSection;
}
/// getSectionForConstant - Given a mergeable constant with the
/// specified size and relocation information, return a section that it
/// should be placed in.
const MCSection *
TargetLoweringObjectFileELF::getSectionForConstant(SectionKind Kind,
const Constant *C) const {
if (Kind.isMergeableConst4() && MergeableConst4Section)
return MergeableConst4Section;
if (Kind.isMergeableConst8() && MergeableConst8Section)
return MergeableConst8Section;
if (Kind.isMergeableConst16() && MergeableConst16Section)
return MergeableConst16Section;
if (Kind.isReadOnly())
return ReadOnlySection;
if (Kind.isReadOnlyWithRelLocal()) return DataRelROLocalSection;
assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
return DataRelROSection;
}
const MCSection *TargetLoweringObjectFileELF::getStaticCtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
// The default scheme is .ctor / .dtor, so we have to invert the priority
// numbering.
if (Priority == 65535)
return StaticCtorSection;
if (UseInitArray) {
std::string Name = std::string(".init_array.") + utostr(Priority);
return getContext().getELFSection(Name, ELF::SHT_INIT_ARRAY,
ELF::SHF_ALLOC | ELF::SHF_WRITE,
SectionKind::getDataRel());
} else {
std::string Name = std::string(".ctors.") + utostr(65535 - Priority);
return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
ELF::SHF_ALLOC |ELF::SHF_WRITE,
SectionKind::getDataRel());
}
}
const MCSection *TargetLoweringObjectFileELF::getStaticDtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
// The default scheme is .ctor / .dtor, so we have to invert the priority
// numbering.
if (Priority == 65535)
return StaticDtorSection;
if (UseInitArray) {
std::string Name = std::string(".fini_array.") + utostr(Priority);
return getContext().getELFSection(Name, ELF::SHT_FINI_ARRAY,
ELF::SHF_ALLOC | ELF::SHF_WRITE,
SectionKind::getDataRel());
} else {
std::string Name = std::string(".dtors.") + utostr(65535 - Priority);
return getContext().getELFSection(Name, ELF::SHT_PROGBITS,
ELF::SHF_ALLOC |ELF::SHF_WRITE,
SectionKind::getDataRel());
}
}
void
TargetLoweringObjectFileELF::InitializeELF(bool UseInitArray_) {
UseInitArray = UseInitArray_;
if (!UseInitArray)
return;
StaticCtorSection =
getContext().getELFSection(".init_array", ELF::SHT_INIT_ARRAY,
ELF::SHF_WRITE |
ELF::SHF_ALLOC,
SectionKind::getDataRel());
StaticDtorSection =
getContext().getELFSection(".fini_array", ELF::SHT_FINI_ARRAY,
ELF::SHF_WRITE |
ELF::SHF_ALLOC,
SectionKind::getDataRel());
}
//===----------------------------------------------------------------------===//
// MachO
//===----------------------------------------------------------------------===//
/// getDepLibFromLinkerOpt - Extract the dependent library name from a linker
/// option string. Returns StringRef() if the option does not specify a library.
StringRef TargetLoweringObjectFileMachO::
getDepLibFromLinkerOpt(StringRef LinkerOption) const {
const char *LibCmd = "-l";
if (LinkerOption.startswith(LibCmd))
return LinkerOption.substr(strlen(LibCmd));
return StringRef();
}
/// emitModuleFlags - Perform code emission for module flags.
void TargetLoweringObjectFileMachO::
emitModuleFlags(MCStreamer &Streamer,
ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
Mangler &Mang, const TargetMachine &TM) const {
unsigned VersionVal = 0;
unsigned ImageInfoFlags = 0;
MDNode *LinkerOptions = nullptr;
StringRef SectionVal;
for (ArrayRef<Module::ModuleFlagEntry>::iterator
i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
const Module::ModuleFlagEntry &MFE = *i;
// Ignore flags with 'Require' behavior.
if (MFE.Behavior == Module::Require)
continue;
StringRef Key = MFE.Key->getString();
Value *Val = MFE.Val;
if (Key == "Objective-C Image Info Version") {
VersionVal = cast<ConstantInt>(Val)->getZExtValue();
} else if (Key == "Objective-C Garbage Collection" ||
Key == "Objective-C GC Only" ||
Key == "Objective-C Is Simulated") {
ImageInfoFlags |= cast<ConstantInt>(Val)->getZExtValue();
} else if (Key == "Objective-C Image Info Section") {
SectionVal = cast<MDString>(Val)->getString();
} else if (Key == "Linker Options") {
LinkerOptions = cast<MDNode>(Val);
}
}
// Emit the linker options if present.
if (LinkerOptions) {
for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
SmallVector<std::string, 4> StrOptions;
// Convert to strings.
for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
StrOptions.push_back(MDOption->getString());
}
Streamer.EmitLinkerOptions(StrOptions);
}
}
// The section is mandatory. If we don't have it, then we don't have GC info.
if (SectionVal.empty()) return;
StringRef Segment, Section;
unsigned TAA = 0, StubSize = 0;
bool TAAParsed;
std::string ErrorCode =
MCSectionMachO::ParseSectionSpecifier(SectionVal, Segment, Section,
TAA, TAAParsed, StubSize);
if (!ErrorCode.empty())
// If invalid, report the error with report_fatal_error.
report_fatal_error("Invalid section specifier '" + Section + "': " +
ErrorCode + ".");
// Get the section.
const MCSectionMachO *S =
getContext().getMachOSection(Segment, Section, TAA, StubSize,
SectionKind::getDataNoRel());
Streamer.SwitchSection(S);
Streamer.EmitLabel(getContext().
GetOrCreateSymbol(StringRef("L_OBJC_IMAGE_INFO")));
Streamer.EmitIntValue(VersionVal, 4);
Streamer.EmitIntValue(ImageInfoFlags, 4);
Streamer.AddBlankLine();
}
static void checkMachOComdat(const GlobalValue *GV) {
const Comdat *C = GV->getComdat();
if (!C)
return;
report_fatal_error("MachO doesn't support COMDATs, '" + C->getName() +
"' cannot be lowered.");
}
const MCSection *TargetLoweringObjectFileMachO::getExplicitSectionGlobal(
const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM) const {
// Parse the section specifier and create it if valid.
StringRef Segment, Section;
unsigned TAA = 0, StubSize = 0;
bool TAAParsed;
checkMachOComdat(GV);
std::string ErrorCode =
MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
TAA, TAAParsed, StubSize);
if (!ErrorCode.empty()) {
// If invalid, report the error with report_fatal_error.
report_fatal_error("Global variable '" + GV->getName() +
"' has an invalid section specifier '" +
GV->getSection() + "': " + ErrorCode + ".");
}
// Get the section.
const 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 '" + GV->getName() +
"' section type or attributes does not match previous"
" section specifier");
}
return S;
}
bool TargetLoweringObjectFileMachO::isSectionAtomizableBySymbols(
const MCSection &Section) const {
const MCSectionMachO &SMO = static_cast<const MCSectionMachO&>(Section);
// Sections holding 1 byte strings are atomized based on the data
// they contain.
// Sections holding 2 byte strings require symbols in order to be
// atomized.
// There is no dedicated section for 4 byte strings.
if (SMO.getKind().isMergeable1ByteCString())
return false;
if (SMO.getSegmentName() == "__DATA" &&
SMO.getSectionName() == "__cfstring")
return false;
switch (SMO.getType()) {
default:
return true;
// These sections are atomized at the element boundaries without using
// symbols.
case MachO::S_4BYTE_LITERALS:
case MachO::S_8BYTE_LITERALS:
case MachO::S_16BYTE_LITERALS:
case MachO::S_LITERAL_POINTERS:
case MachO::S_NON_LAZY_SYMBOL_POINTERS:
case MachO::S_LAZY_SYMBOL_POINTERS:
case MachO::S_MOD_INIT_FUNC_POINTERS:
case MachO::S_MOD_TERM_FUNC_POINTERS:
case MachO::S_INTERPOSING:
return false;
}
}
const MCSection *TargetLoweringObjectFileMachO::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, const TargetMachine &TM) const {
checkMachOComdat(GV);
// Handle thread local data.
if (Kind.isThreadBSS()) return TLSBSSSection;
if (Kind.isThreadData()) return TLSDataSection;
if (Kind.isText())
return GV->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 (GV->isWeakForLinker()) {
if (Kind.isReadOnly())
return ConstTextCoalSection;
return DataCoalSection;
}
// FIXME: Alignment check should be handled by section classifier.
if (Kind.isMergeable1ByteCString() &&
TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 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() && !GV->hasExternalLinkage() &&
TM.getDataLayout()->getPreferredAlignment(cast<GlobalVariable>(GV)) < 32)
return UStringSection;
if (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;
}
const MCSection *
TargetLoweringObjectFileMachO::getSectionForConstant(SectionKind Kind,
const Constant *C) const {
// If this constant requires a relocation, we have to put it in the data
// segment, not in the text segment.
if (Kind.isDataRel() || 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, Mangler &Mang,
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, "$non_lazy_ptr", Mang, TM);
// Add information about the stub reference to MachOMMI so that the stub
// gets emitted by the asmprinter.
MachineModuleInfoImpl::StubValueTy &StubSym =
GV->hasHiddenVisibility() ? MachOMMI.getHiddenGVStubEntry(SSym) :
MachOMMI.getGVStubEntry(SSym);
if (!StubSym.getPointer()) {
MCSymbol *Sym = TM.getSymbol(GV, Mang);
StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
}
return TargetLoweringObjectFile::
getTTypeReference(MCSymbolRefExpr::Create(SSym, getContext()),
Encoding & ~dwarf::DW_EH_PE_indirect, Streamer);
}
return TargetLoweringObjectFile::getTTypeGlobalReference(GV, Encoding, Mang,
TM, MMI, Streamer);
}
MCSymbol *TargetLoweringObjectFileMachO::getCFIPersonalitySymbol(
const GlobalValue *GV, Mangler &Mang, const TargetMachine &TM,
MachineModuleInfo *MMI) const {
// The mach-o version of this method defaults to returning a stub reference.
MachineModuleInfoMachO &MachOMMI =
MMI->getObjFileInfo<MachineModuleInfoMachO>();
MCSymbol *SSym = getSymbolWithGlobalValueBase(GV, "$non_lazy_ptr", Mang, 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, Mang);
StubSym = MachineModuleInfoImpl::StubValueTy(Sym, !GV->hasLocalLinkage());
}
return SSym;
}
//===----------------------------------------------------------------------===//
// COFF
//===----------------------------------------------------------------------===//
static unsigned
getCOFFSectionFlags(SectionKind K) {
unsigned Flags = 0;
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;
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())
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 it's 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;
}
} else if (GV->isWeakForLinker()) {
return COFF::IMAGE_COMDAT_SELECT_ANY;
}
return 0;
}
const MCSection *TargetLoweringObjectFileCOFF::getExplicitSectionGlobal(
const GlobalValue *GV, SectionKind Kind, Mangler &Mang,
const TargetMachine &TM) const {
int Selection = 0;
unsigned Characteristics = getCOFFSectionFlags(Kind);
StringRef Name = GV->getSection();
StringRef COMDATSymName = "";
if ((GV->isWeakForLinker() || GV->hasComdat()) && !Kind.isCommon()) {
Selection = getSelectionForCOFF(GV);
const GlobalValue *ComdatGV;
if (Selection == COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE)
ComdatGV = getComdatGVForCOFF(GV);
else
ComdatGV = GV;
if (!ComdatGV->hasPrivateLinkage()) {
MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
COMDATSymName = Sym->getName();
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
} else {
Selection = 0;
}
}
return getContext().getCOFFSection(Name,
Characteristics,
Kind,
COMDATSymName,
Selection);
}
static const char *getCOFFSectionNameForUniqueGlobal(SectionKind Kind) {
if (Kind.isText())
return ".text";
if (Kind.isBSS())
return ".bss";
if (Kind.isThreadLocal())
return ".tls$";
if (Kind.isWriteable())
return ".data";
return ".rdata";
}
const MCSection *TargetLoweringObjectFileCOFF::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler &Mang, 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 this global is linkonce/weak and the target handles this by emitting it
// into a 'uniqued' section name, create and return the section now.
// Section names depend on the name of the symbol which is not feasible if the
// symbol has private linkage.
if ((GV->isWeakForLinker() || EmitUniquedSection || GV->hasComdat()) &&
!Kind.isCommon()) {
const char *Name = getCOFFSectionNameForUniqueGlobal(Kind);
unsigned Characteristics = getCOFFSectionFlags(Kind);
Characteristics |= COFF::IMAGE_SCN_LNK_COMDAT;
int Selection = getSelectionForCOFF(GV);
if (!Selection)
Selection = COFF::IMAGE_COMDAT_SELECT_NODUPLICATES;
const GlobalValue *ComdatGV;
if (GV->hasComdat())
ComdatGV = getComdatGVForCOFF(GV);
else
ComdatGV = GV;
if (!ComdatGV->hasPrivateLinkage()) {
MCSymbol *Sym = TM.getSymbol(ComdatGV, Mang);
StringRef COMDATSymName = Sym->getName();
return getContext().getCOFFSection(Name, Characteristics, Kind,
COMDATSymName, Selection);
}
}
if (Kind.isText())
return TextSection;
if (Kind.isThreadLocal())
return TLSDataSection;
if (Kind.isReadOnly())
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;
}
StringRef TargetLoweringObjectFileCOFF::
getDepLibFromLinkerOpt(StringRef LinkerOption) const {
const char *LibCmd = "/DEFAULTLIB:";
if (LinkerOption.startswith(LibCmd))
return LinkerOption.substr(strlen(LibCmd));
return StringRef();
}
void TargetLoweringObjectFileCOFF::
emitModuleFlags(MCStreamer &Streamer,
ArrayRef<Module::ModuleFlagEntry> ModuleFlags,
Mangler &Mang, const TargetMachine &TM) const {
MDNode *LinkerOptions = nullptr;
// Look for the "Linker Options" flag, since it's the only one we support.
for (ArrayRef<Module::ModuleFlagEntry>::iterator
i = ModuleFlags.begin(), e = ModuleFlags.end(); i != e; ++i) {
const Module::ModuleFlagEntry &MFE = *i;
StringRef Key = MFE.Key->getString();
Value *Val = MFE.Val;
if (Key == "Linker Options") {
LinkerOptions = cast<MDNode>(Val);
break;
}
}
if (!LinkerOptions)
return;
// Emit the linker options to the linker .drectve section. According to the
// spec, this section is a space-separated string containing flags for linker.
const MCSection *Sec = getDrectveSection();
Streamer.SwitchSection(Sec);
for (unsigned i = 0, e = LinkerOptions->getNumOperands(); i != e; ++i) {
MDNode *MDOptions = cast<MDNode>(LinkerOptions->getOperand(i));
for (unsigned ii = 0, ie = MDOptions->getNumOperands(); ii != ie; ++ii) {
MDString *MDOption = cast<MDString>(MDOptions->getOperand(ii));
StringRef Op = MDOption->getString();
// Lead with a space for consistency with our dllexport implementation.
std::string Escaped(" ");
if (Op.find(" ") != StringRef::npos) {
// The PE-COFF spec says args with spaces must be quoted. It doesn't say
// how to escape quotes, but it probably uses this algorithm:
// http://msdn.microsoft.com/en-us/library/17w5ykft(v=vs.85).aspx
// FIXME: Reuse escaping code from Support/Windows/Program.inc
Escaped.push_back('\"');
Escaped.append(Op);
Escaped.push_back('\"');
} else {
Escaped.append(Op);
}
Streamer.EmitBytes(Escaped);
}
}
}
static const MCSection *getAssociativeCOFFSection(MCContext &Ctx,
const MCSection *Sec,
const MCSymbol *KeySym) {
// Return the normal section if we don't have to be associative.
if (!KeySym)
return Sec;
// Make an associative section with the same name and kind as the normal
// section.
const MCSectionCOFF *SecCOFF = cast<MCSectionCOFF>(Sec);
unsigned Characteristics =
SecCOFF->getCharacteristics() | COFF::IMAGE_SCN_LNK_COMDAT;
return Ctx.getCOFFSection(SecCOFF->getSectionName(), Characteristics,
SecCOFF->getKind(), KeySym->getName(),
COFF::IMAGE_COMDAT_SELECT_ASSOCIATIVE);
}
const MCSection *TargetLoweringObjectFileCOFF::getStaticCtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
return getAssociativeCOFFSection(getContext(), StaticCtorSection, KeySym);
}
const MCSection *TargetLoweringObjectFileCOFF::getStaticDtorSection(
unsigned Priority, const MCSymbol *KeySym) const {
return getAssociativeCOFFSection(getContext(), StaticDtorSection, KeySym);
}
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