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llvm-mirror/lib/Target/TargetLoweringObjectFile.cpp
Chris Lattner 15e2a64ec2 stop using the .lcomm pseudoop on darwin, instead, directly use the 
.zerofill directive.  Streamerize its generation.

llvm-svn: 93868
2010-01-19 06:25:51 +00:00

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//===-- llvm/Target/TargetLoweringObjectFile.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/Target/TargetLoweringObjectFile.h"
#include "llvm/Constants.h"
#include "llvm/DerivedTypes.h"
#include "llvm/Function.h"
#include "llvm/GlobalVariable.h"
#include "llvm/MC/MCContext.h"
#include "llvm/MC/MCExpr.h"
#include "llvm/MC/MCSectionMachO.h"
#include "llvm/MC/MCSectionELF.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Target/Mangler.h"
#include "llvm/Target/TargetData.h"
#include "llvm/Target/TargetMachine.h"
#include "llvm/Target/TargetOptions.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/StringExtras.h"
using namespace llvm;
//===----------------------------------------------------------------------===//
// Generic Code
//===----------------------------------------------------------------------===//
TargetLoweringObjectFile::TargetLoweringObjectFile() : Ctx(0) {
TextSection = 0;
DataSection = 0;
BSSSection = 0;
ReadOnlySection = 0;
StaticCtorSection = 0;
StaticDtorSection = 0;
LSDASection = 0;
EHFrameSection = 0;
DwarfAbbrevSection = 0;
DwarfInfoSection = 0;
DwarfLineSection = 0;
DwarfFrameSection = 0;
DwarfPubNamesSection = 0;
DwarfPubTypesSection = 0;
DwarfDebugInlineSection = 0;
DwarfStrSection = 0;
DwarfLocSection = 0;
DwarfARangesSection = 0;
DwarfRangesSection = 0;
DwarfMacroInfoSection = 0;
}
TargetLoweringObjectFile::~TargetLoweringObjectFile() {
}
static bool isSuitableForBSS(const GlobalVariable *GV) {
Constant *C = GV->getInitializer();
// Must have zero initializer.
if (!C->isNullValue())
return false;
// Leave constant zeros in readonly constant sections, so they can be shared.
if (GV->isConstant())
return false;
// If the global has an explicit section specified, don't put it in BSS.
if (!GV->getSection().empty())
return false;
// If -nozero-initialized-in-bss is specified, don't ever use BSS.
if (NoZerosInBSS)
return false;
// Otherwise, put it in BSS!
return true;
}
/// IsNullTerminatedString - Return true if the specified constant (which is
/// known to have a type that is an array of 1/2/4 byte elements) ends with a
/// nul value and contains no other nuls in it.
static bool IsNullTerminatedString(const Constant *C) {
const ArrayType *ATy = cast<ArrayType>(C->getType());
// First check: is we have constant array of i8 terminated with zero
if (const ConstantArray *CVA = dyn_cast<ConstantArray>(C)) {
if (ATy->getNumElements() == 0) return false;
ConstantInt *Null =
dyn_cast<ConstantInt>(CVA->getOperand(ATy->getNumElements()-1));
if (Null == 0 || Null->getZExtValue() != 0)
return false; // Not null terminated.
// Verify that the null doesn't occur anywhere else in the string.
for (unsigned i = 0, e = ATy->getNumElements()-1; i != e; ++i)
// Reject constantexpr elements etc.
if (!isa<ConstantInt>(CVA->getOperand(i)) ||
CVA->getOperand(i) == Null)
return false;
return true;
}
// Another possibility: [1 x i8] zeroinitializer
if (isa<ConstantAggregateZero>(C))
return ATy->getNumElements() == 1;
return false;
}
/// getKindForGlobal - This is a top-level target-independent classifier for
/// a global variable. Given an global variable and information from TM, it
/// classifies the global in a variety of ways that make various target
/// implementations simpler. The target implementation is free to ignore this
/// extra info of course.
SectionKind TargetLoweringObjectFile::getKindForGlobal(const GlobalValue *GV,
const TargetMachine &TM){
assert(!GV->isDeclaration() && !GV->hasAvailableExternallyLinkage() &&
"Can only be used for global definitions");
Reloc::Model ReloModel = TM.getRelocationModel();
// Early exit - functions should be always in text sections.
const GlobalVariable *GVar = dyn_cast<GlobalVariable>(GV);
if (GVar == 0)
return SectionKind::getText();
// Handle thread-local data first.
if (GVar->isThreadLocal()) {
if (isSuitableForBSS(GVar))
return SectionKind::getThreadBSS();
return SectionKind::getThreadData();
}
// Variables with common linkage always get classified as common.
if (GVar->hasCommonLinkage())
return SectionKind::getCommon();
// Variable can be easily put to BSS section.
if (isSuitableForBSS(GVar)) {
if (GVar->hasLocalLinkage())
return SectionKind::getBSSLocal();
else if (GVar->hasExternalLinkage())
return SectionKind::getBSSExtern();
return SectionKind::getBSS();
}
Constant *C = GVar->getInitializer();
// If the global is marked constant, we can put it into a mergable section,
// a mergable string section, or general .data if it contains relocations.
if (GVar->isConstant()) {
// If the initializer for the global contains something that requires a
// relocation, then we may have to drop this into a wriable data section
// even though it is marked const.
switch (C->getRelocationInfo()) {
default: assert(0 && "unknown relocation info kind");
case Constant::NoRelocation:
// If initializer is a null-terminated string, put it in a "cstring"
// section of the right width.
if (const ArrayType *ATy = dyn_cast<ArrayType>(C->getType())) {
if (const IntegerType *ITy =
dyn_cast<IntegerType>(ATy->getElementType())) {
if ((ITy->getBitWidth() == 8 || ITy->getBitWidth() == 16 ||
ITy->getBitWidth() == 32) &&
IsNullTerminatedString(C)) {
if (ITy->getBitWidth() == 8)
return SectionKind::getMergeable1ByteCString();
if (ITy->getBitWidth() == 16)
return SectionKind::getMergeable2ByteCString();
assert(ITy->getBitWidth() == 32 && "Unknown width");
return SectionKind::getMergeable4ByteCString();
}
}
}
// Otherwise, just drop it into a mergable constant section. If we have
// a section for this size, use it, otherwise use the arbitrary sized
// mergable section.
switch (TM.getTargetData()->getTypeAllocSize(C->getType())) {
case 4: return SectionKind::getMergeableConst4();
case 8: return SectionKind::getMergeableConst8();
case 16: return SectionKind::getMergeableConst16();
default: return SectionKind::getMergeableConst();
}
case Constant::LocalRelocation:
// In static relocation model, the linker will resolve all addresses, so
// the relocation entries will actually be constants by the time the app
// starts up. However, we can't put this into a mergable section, because
// the linker doesn't take relocations into consideration when it tries to
// merge entries in the section.
if (ReloModel == Reloc::Static)
return SectionKind::getReadOnly();
// Otherwise, the dynamic linker needs to fix it up, put it in the
// writable data.rel.local section.
return SectionKind::getReadOnlyWithRelLocal();
case Constant::GlobalRelocations:
// In static relocation model, the linker will resolve all addresses, so
// the relocation entries will actually be constants by the time the app
// starts up. However, we can't put this into a mergable section, because
// the linker doesn't take relocations into consideration when it tries to
// merge entries in the section.
if (ReloModel == Reloc::Static)
return SectionKind::getReadOnly();
// Otherwise, the dynamic linker needs to fix it up, put it in the
// writable data.rel section.
return SectionKind::getReadOnlyWithRel();
}
}
// Okay, this isn't a constant. If the initializer for the global is going
// to require a runtime relocation by the dynamic linker, put it into a more
// specific section to improve startup time of the app. This coalesces these
// globals together onto fewer pages, improving the locality of the dynamic
// linker.
if (ReloModel == Reloc::Static)
return SectionKind::getDataNoRel();
switch (C->getRelocationInfo()) {
default: assert(0 && "unknown relocation info kind");
case Constant::NoRelocation:
return SectionKind::getDataNoRel();
case Constant::LocalRelocation:
return SectionKind::getDataRelLocal();
case Constant::GlobalRelocations:
return SectionKind::getDataRel();
}
}
/// SectionForGlobal - This method computes the appropriate section to emit
/// the specified global variable or function definition. This should not
/// be passed external (or available externally) globals.
const MCSection *TargetLoweringObjectFile::
SectionForGlobal(const GlobalValue *GV, SectionKind Kind, Mangler *Mang,
const TargetMachine &TM) const {
// Select section name.
if (GV->hasSection())
return getExplicitSectionGlobal(GV, Kind, Mang, TM);
// Use default section depending on the 'type' of global
return SelectSectionForGlobal(GV, Kind, Mang, TM);
}
// Lame default implementation. Calculate the section name for global.
const MCSection *
TargetLoweringObjectFile::SelectSectionForGlobal(const GlobalValue *GV,
SectionKind Kind,
Mangler *Mang,
const TargetMachine &TM) const{
assert(!Kind.isThreadLocal() && "Doesn't support TLS");
if (Kind.isText())
return getTextSection();
if (Kind.isBSS() && BSSSection != 0)
return BSSSection;
if (Kind.isReadOnly() && ReadOnlySection != 0)
return ReadOnlySection;
return getDataSection();
}
/// getSectionForConstant - Given a mergable constant with the
/// specified size and relocation information, return a section that it
/// should be placed in.
const MCSection *
TargetLoweringObjectFile::getSectionForConstant(SectionKind Kind) const {
if (Kind.isReadOnly() && ReadOnlySection != 0)
return ReadOnlySection;
return DataSection;
}
/// getSymbolForDwarfGlobalReference - Return an MCExpr to use for a
/// pc-relative reference to the specified global variable from exception
/// handling information. In addition to the symbol, this returns
/// by-reference:
///
/// IsIndirect - True if the returned symbol is actually a stub that contains
/// the address of the symbol, false if the symbol is the global itself.
///
/// IsPCRel - True if the symbol reference is already pc-relative, false if
/// the caller needs to subtract off the address of the reference from the
/// symbol.
///
const MCExpr *TargetLoweringObjectFile::
getSymbolForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
MachineModuleInfo *MMI,
bool &IsIndirect, bool &IsPCRel) const {
// The generic implementation of this just returns a direct reference to the
// symbol.
IsIndirect = false;
IsPCRel = false;
// FIXME: Use GetGlobalValueSymbol.
SmallString<128> Name;
Mang->getNameWithPrefix(Name, GV, false);
return MCSymbolRefExpr::Create(Name.str(), getContext());
}
//===----------------------------------------------------------------------===//
// ELF
//===----------------------------------------------------------------------===//
typedef StringMap<const MCSectionELF*> ELFUniqueMapTy;
TargetLoweringObjectFileELF::~TargetLoweringObjectFileELF() {
// If we have the section uniquing map, free it.
delete (ELFUniqueMapTy*)UniquingMap;
}
const MCSection *TargetLoweringObjectFileELF::
getELFSection(StringRef Section, unsigned Type, unsigned Flags,
SectionKind Kind, bool IsExplicit) const {
if (UniquingMap == 0)
UniquingMap = new ELFUniqueMapTy();
ELFUniqueMapTy &Map = *(ELFUniqueMapTy*)UniquingMap;
// Do the lookup, if we have a hit, return it.
const MCSectionELF *&Entry = Map[Section];
if (Entry) return Entry;
return Entry = MCSectionELF::Create(Section, Type, Flags, Kind, IsExplicit,
getContext());
}
void TargetLoweringObjectFileELF::Initialize(MCContext &Ctx,
const TargetMachine &TM) {
if (UniquingMap != 0)
((ELFUniqueMapTy*)UniquingMap)->clear();
TargetLoweringObjectFile::Initialize(Ctx, TM);
BSSSection =
getELFSection(".bss", MCSectionELF::SHT_NOBITS,
MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
SectionKind::getBSS());
TextSection =
getELFSection(".text", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_EXECINSTR | MCSectionELF::SHF_ALLOC,
SectionKind::getText());
DataSection =
getELFSection(".data", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_WRITE | MCSectionELF::SHF_ALLOC,
SectionKind::getDataRel());
ReadOnlySection =
getELFSection(".rodata", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC,
SectionKind::getReadOnly());
TLSDataSection =
getELFSection(".tdata", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
MCSectionELF::SHF_WRITE, SectionKind::getThreadData());
TLSBSSSection =
getELFSection(".tbss", MCSectionELF::SHT_NOBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_TLS |
MCSectionELF::SHF_WRITE, SectionKind::getThreadBSS());
DataRelSection =
getELFSection(".data.rel", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
SectionKind::getDataRel());
DataRelLocalSection =
getELFSection(".data.rel.local", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
SectionKind::getDataRelLocal());
DataRelROSection =
getELFSection(".data.rel.ro", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
SectionKind::getReadOnlyWithRel());
DataRelROLocalSection =
getELFSection(".data.rel.ro.local", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
SectionKind::getReadOnlyWithRelLocal());
MergeableConst4Section =
getELFSection(".rodata.cst4", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
SectionKind::getMergeableConst4());
MergeableConst8Section =
getELFSection(".rodata.cst8", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
SectionKind::getMergeableConst8());
MergeableConst16Section =
getELFSection(".rodata.cst16", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_MERGE,
SectionKind::getMergeableConst16());
StaticCtorSection =
getELFSection(".ctors", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
SectionKind::getDataRel());
StaticDtorSection =
getELFSection(".dtors", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
SectionKind::getDataRel());
// Exception Handling Sections.
// FIXME: We're emitting LSDA info into a readonly section on ELF, even though
// it contains relocatable pointers. In PIC mode, this is probably a big
// runtime hit for C++ apps. Either the contents of the LSDA need to be
// adjusted or this should be a data section.
LSDASection =
getELFSection(".gcc_except_table", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC, SectionKind::getReadOnly());
EHFrameSection =
getELFSection(".eh_frame", MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC | MCSectionELF::SHF_WRITE,
SectionKind::getDataRel());
// Debug Info Sections.
DwarfAbbrevSection =
getELFSection(".debug_abbrev", MCSectionELF::SHT_PROGBITS, 0,
SectionKind::getMetadata());
DwarfInfoSection =
getELFSection(".debug_info", MCSectionELF::SHT_PROGBITS, 0,
SectionKind::getMetadata());
DwarfLineSection =
getELFSection(".debug_line", MCSectionELF::SHT_PROGBITS, 0,
SectionKind::getMetadata());
DwarfFrameSection =
getELFSection(".debug_frame", MCSectionELF::SHT_PROGBITS, 0,
SectionKind::getMetadata());
DwarfPubNamesSection =
getELFSection(".debug_pubnames", MCSectionELF::SHT_PROGBITS, 0,
SectionKind::getMetadata());
DwarfPubTypesSection =
getELFSection(".debug_pubtypes", MCSectionELF::SHT_PROGBITS, 0,
SectionKind::getMetadata());
DwarfStrSection =
getELFSection(".debug_str", MCSectionELF::SHT_PROGBITS, 0,
SectionKind::getMetadata());
DwarfLocSection =
getELFSection(".debug_loc", MCSectionELF::SHT_PROGBITS, 0,
SectionKind::getMetadata());
DwarfARangesSection =
getELFSection(".debug_aranges", MCSectionELF::SHT_PROGBITS, 0,
SectionKind::getMetadata());
DwarfRangesSection =
getELFSection(".debug_ranges", MCSectionELF::SHT_PROGBITS, 0,
SectionKind::getMetadata());
DwarfMacroInfoSection =
getELFSection(".debug_macinfo", MCSectionELF::SHT_PROGBITS, 0,
SectionKind::getMetadata());
}
static SectionKind
getELFKindForNamedSection(const char *Name, SectionKind K) {
if (Name[0] != '.') return K;
// Some lame default implementation based on some magic section names.
if (strcmp(Name, ".bss") == 0 ||
strncmp(Name, ".bss.", 5) == 0 ||
strncmp(Name, ".gnu.linkonce.b.", 16) == 0 ||
strncmp(Name, ".llvm.linkonce.b.", 17) == 0 ||
strcmp(Name, ".sbss") == 0 ||
strncmp(Name, ".sbss.", 6) == 0 ||
strncmp(Name, ".gnu.linkonce.sb.", 17) == 0 ||
strncmp(Name, ".llvm.linkonce.sb.", 18) == 0)
return SectionKind::getBSS();
if (strcmp(Name, ".tdata") == 0 ||
strncmp(Name, ".tdata.", 7) == 0 ||
strncmp(Name, ".gnu.linkonce.td.", 17) == 0 ||
strncmp(Name, ".llvm.linkonce.td.", 18) == 0)
return SectionKind::getThreadData();
if (strcmp(Name, ".tbss") == 0 ||
strncmp(Name, ".tbss.", 6) == 0 ||
strncmp(Name, ".gnu.linkonce.tb.", 17) == 0 ||
strncmp(Name, ".llvm.linkonce.tb.", 18) == 0)
return SectionKind::getThreadBSS();
return K;
}
static unsigned getELFSectionType(StringRef Name, SectionKind K) {
if (Name == ".init_array")
return MCSectionELF::SHT_INIT_ARRAY;
if (Name == ".fini_array")
return MCSectionELF::SHT_FINI_ARRAY;
if (Name == ".preinit_array")
return MCSectionELF::SHT_PREINIT_ARRAY;
if (K.isBSS() || K.isThreadBSS())
return MCSectionELF::SHT_NOBITS;
return MCSectionELF::SHT_PROGBITS;
}
static unsigned
getELFSectionFlags(SectionKind K) {
unsigned Flags = 0;
if (!K.isMetadata())
Flags |= MCSectionELF::SHF_ALLOC;
if (K.isText())
Flags |= MCSectionELF::SHF_EXECINSTR;
if (K.isWriteable())
Flags |= MCSectionELF::SHF_WRITE;
if (K.isThreadLocal())
Flags |= MCSectionELF::SHF_TLS;
// K.isMergeableConst() is left out to honour PR4650
if (K.isMergeableCString() || K.isMergeableConst4() ||
K.isMergeableConst8() || K.isMergeableConst16())
Flags |= MCSectionELF::SHF_MERGE;
if (K.isMergeableCString())
Flags |= MCSectionELF::SHF_STRINGS;
return Flags;
}
const MCSection *TargetLoweringObjectFileELF::
getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler *Mang, const TargetMachine &TM) const {
const char *SectionName = GV->getSection().c_str();
// Infer section flags from the section name if we can.
Kind = getELFKindForNamedSection(SectionName, Kind);
return getELFSection(SectionName,
getELFSectionType(SectionName, Kind),
getELFSectionFlags(Kind), Kind, true);
}
static const char *getSectionPrefixForUniqueGlobal(SectionKind Kind) {
if (Kind.isText()) return ".gnu.linkonce.t.";
if (Kind.isReadOnly()) return ".gnu.linkonce.r.";
if (Kind.isThreadData()) return ".gnu.linkonce.td.";
if (Kind.isThreadBSS()) return ".gnu.linkonce.tb.";
if (Kind.isDataNoRel()) return ".gnu.linkonce.d.";
if (Kind.isDataRelLocal()) return ".gnu.linkonce.d.rel.local.";
if (Kind.isDataRel()) return ".gnu.linkonce.d.rel.";
if (Kind.isReadOnlyWithRelLocal()) return ".gnu.linkonce.d.rel.ro.local.";
assert(Kind.isReadOnlyWithRel() && "Unknown section kind");
return ".gnu.linkonce.d.rel.ro.";
}
const MCSection *TargetLoweringObjectFileELF::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler *Mang, const TargetMachine &TM) const {
// 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() && !Kind.isCommon() && !Kind.isBSS()) {
const char *Prefix = getSectionPrefixForUniqueGlobal(Kind);
SmallString<128> Name;
Name.append(Prefix, Prefix+strlen(Prefix));
Mang->getNameWithPrefix(Name, GV, false);
return getELFSection(Name.str(), getELFSectionType(Name.str(), Kind),
getELFSectionFlags(Kind), Kind);
}
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.getTargetData()->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 getELFSection(Name.c_str(), MCSectionELF::SHT_PROGBITS,
MCSectionELF::SHF_ALLOC |
MCSectionELF::SHF_MERGE |
MCSectionELF::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 {
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;
}
//===----------------------------------------------------------------------===//
// MachO
//===----------------------------------------------------------------------===//
typedef StringMap<const MCSectionMachO*> MachOUniqueMapTy;
TargetLoweringObjectFileMachO::~TargetLoweringObjectFileMachO() {
// If we have the MachO uniquing map, free it.
delete (MachOUniqueMapTy*)UniquingMap;
}
const MCSectionMachO *TargetLoweringObjectFileMachO::
getMachOSection(StringRef Segment, StringRef Section,
unsigned TypeAndAttributes,
unsigned Reserved2, SectionKind Kind) const {
// We unique sections by their segment/section pair. The returned section
// may not have the same flags as the requested section, if so this should be
// diagnosed by the client as an error.
// Create the map if it doesn't already exist.
if (UniquingMap == 0)
UniquingMap = new MachOUniqueMapTy();
MachOUniqueMapTy &Map = *(MachOUniqueMapTy*)UniquingMap;
// Form the name to look up.
SmallString<64> Name;
Name += Segment;
Name.push_back(',');
Name += Section;
// Do the lookup, if we have a hit, return it.
const MCSectionMachO *&Entry = Map[Name.str()];
if (Entry) return Entry;
// Otherwise, return a new section.
return Entry = MCSectionMachO::Create(Segment, Section, TypeAndAttributes,
Reserved2, Kind, getContext());
}
void TargetLoweringObjectFileMachO::Initialize(MCContext &Ctx,
const TargetMachine &TM) {
if (UniquingMap != 0)
((MachOUniqueMapTy*)UniquingMap)->clear();
TargetLoweringObjectFile::Initialize(Ctx, TM);
TextSection // .text
= getMachOSection("__TEXT", "__text",
MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
SectionKind::getText());
DataSection // .data
= getMachOSection("__DATA", "__data", 0, SectionKind::getDataRel());
CStringSection // .cstring
= getMachOSection("__TEXT", "__cstring", MCSectionMachO::S_CSTRING_LITERALS,
SectionKind::getMergeable1ByteCString());
UStringSection
= getMachOSection("__TEXT","__ustring", 0,
SectionKind::getMergeable2ByteCString());
FourByteConstantSection // .literal4
= getMachOSection("__TEXT", "__literal4", MCSectionMachO::S_4BYTE_LITERALS,
SectionKind::getMergeableConst4());
EightByteConstantSection // .literal8
= getMachOSection("__TEXT", "__literal8", MCSectionMachO::S_8BYTE_LITERALS,
SectionKind::getMergeableConst8());
// ld_classic doesn't support .literal16 in 32-bit mode, and ld64 falls back
// to using it in -static mode.
SixteenByteConstantSection = 0;
if (TM.getRelocationModel() != Reloc::Static &&
TM.getTargetData()->getPointerSize() == 32)
SixteenByteConstantSection = // .literal16
getMachOSection("__TEXT", "__literal16",MCSectionMachO::S_16BYTE_LITERALS,
SectionKind::getMergeableConst16());
ReadOnlySection // .const
= getMachOSection("__TEXT", "__const", 0, SectionKind::getReadOnly());
TextCoalSection
= getMachOSection("__TEXT", "__textcoal_nt",
MCSectionMachO::S_COALESCED |
MCSectionMachO::S_ATTR_PURE_INSTRUCTIONS,
SectionKind::getText());
ConstTextCoalSection
= getMachOSection("__TEXT", "__const_coal", MCSectionMachO::S_COALESCED,
SectionKind::getText());
ConstDataCoalSection
= getMachOSection("__DATA","__const_coal", MCSectionMachO::S_COALESCED,
SectionKind::getText());
ConstDataSection // .const_data
= getMachOSection("__DATA", "__const", 0,
SectionKind::getReadOnlyWithRel());
DataCoalSection
= getMachOSection("__DATA","__datacoal_nt", MCSectionMachO::S_COALESCED,
SectionKind::getDataRel());
DataCommonSection
= getMachOSection("__DATA","__common", MCSectionMachO::S_ZEROFILL,
SectionKind::getBSS());
DataBSSSection
= getMachOSection("__DATA","__bss", MCSectionMachO::S_ZEROFILL,
SectionKind::getBSS());
LazySymbolPointerSection
= getMachOSection("__DATA", "__la_symbol_ptr",
MCSectionMachO::S_LAZY_SYMBOL_POINTERS,
SectionKind::getMetadata());
NonLazySymbolPointerSection
= getMachOSection("__DATA", "__nl_symbol_ptr",
MCSectionMachO::S_NON_LAZY_SYMBOL_POINTERS,
SectionKind::getMetadata());
if (TM.getRelocationModel() == Reloc::Static) {
StaticCtorSection
= getMachOSection("__TEXT", "__constructor", 0,SectionKind::getDataRel());
StaticDtorSection
= getMachOSection("__TEXT", "__destructor", 0, SectionKind::getDataRel());
} else {
StaticCtorSection
= getMachOSection("__DATA", "__mod_init_func",
MCSectionMachO::S_MOD_INIT_FUNC_POINTERS,
SectionKind::getDataRel());
StaticDtorSection
= getMachOSection("__DATA", "__mod_term_func",
MCSectionMachO::S_MOD_TERM_FUNC_POINTERS,
SectionKind::getDataRel());
}
// Exception Handling.
LSDASection = getMachOSection("__DATA", "__gcc_except_tab", 0,
SectionKind::getDataRel());
EHFrameSection =
getMachOSection("__TEXT", "__eh_frame",
MCSectionMachO::S_COALESCED |
MCSectionMachO::S_ATTR_NO_TOC |
MCSectionMachO::S_ATTR_STRIP_STATIC_SYMS |
MCSectionMachO::S_ATTR_LIVE_SUPPORT,
SectionKind::getReadOnly());
// Debug Information.
DwarfAbbrevSection =
getMachOSection("__DWARF", "__debug_abbrev", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
DwarfInfoSection =
getMachOSection("__DWARF", "__debug_info", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
DwarfLineSection =
getMachOSection("__DWARF", "__debug_line", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
DwarfFrameSection =
getMachOSection("__DWARF", "__debug_frame", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
DwarfPubNamesSection =
getMachOSection("__DWARF", "__debug_pubnames", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
DwarfPubTypesSection =
getMachOSection("__DWARF", "__debug_pubtypes", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
DwarfStrSection =
getMachOSection("__DWARF", "__debug_str", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
DwarfLocSection =
getMachOSection("__DWARF", "__debug_loc", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
DwarfARangesSection =
getMachOSection("__DWARF", "__debug_aranges", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
DwarfRangesSection =
getMachOSection("__DWARF", "__debug_ranges", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
DwarfMacroInfoSection =
getMachOSection("__DWARF", "__debug_macinfo", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
DwarfDebugInlineSection =
getMachOSection("__DWARF", "__debug_inlined", MCSectionMachO::S_ATTR_DEBUG,
SectionKind::getMetadata());
}
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, StubSize;
std::string ErrorCode =
MCSectionMachO::ParseSectionSpecifier(GV->getSection(), Segment, Section,
TAA, StubSize);
if (!ErrorCode.empty()) {
// If invalid, report the error with llvm_report_error.
llvm_report_error("Global variable '" + GV->getNameStr() +
"' has an invalid section specifier '" + GV->getSection()+
"': " + ErrorCode + ".");
// Fall back to dropping it into the data section.
return DataSection;
}
// Get the section.
const MCSectionMachO *S =
getMachOSection(Segment, Section, TAA, StubSize, Kind);
// 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 llvm_report_error.
llvm_report_error("Global variable '" + GV->getNameStr() +
"' section type or attributes does not match previous"
" section specifier");
}
return S;
}
const MCSection *TargetLoweringObjectFileMachO::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler *Mang, const TargetMachine &TM) const {
assert(!Kind.isThreadLocal() && "Darwin doesn't support TLS");
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() ||
Kind.isMergeable2ByteCString()) {
if (TM.getTargetData()->getPreferredAlignment(
cast<GlobalVariable>(GV)) < 32) {
if (Kind.isMergeable1ByteCString())
return CStringSection;
assert(Kind.isMergeable2ByteCString());
return UStringSection;
}
}
if (Kind.isMergeableConst()) {
if (Kind.isMergeableConst4())
return FourByteConstantSection;
if (Kind.isMergeableConst8())
return EightByteConstantSection;
if (Kind.isMergeableConst16() && SixteenByteConstantSection)
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 {
// 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() && SixteenByteConstantSection)
return SixteenByteConstantSection;
return ReadOnlySection; // .const
}
/// shouldEmitUsedDirectiveFor - This hook allows targets to selectively decide
/// not to emit the UsedDirective for some symbols in llvm.used.
// FIXME: REMOVE this (rdar://7071300)
bool TargetLoweringObjectFileMachO::
shouldEmitUsedDirectiveFor(const GlobalValue *GV, Mangler *Mang) const {
/// On Darwin, internally linked data beginning with "L" or "l" does not have
/// the directive emitted (this occurs in ObjC metadata).
if (!GV) return false;
// Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
// FIXME: ObjC metadata is currently emitted as internal symbols that have
// \1L and \0l prefixes on them. Fix them to be Private/LinkerPrivate and
// this horrible hack can go away.
SmallString<64> Name;
Mang->getNameWithPrefix(Name, GV, false);
if (Name[0] == 'L' || Name[0] == 'l')
return false;
}
return true;
}
const MCExpr *TargetLoweringObjectFileMachO::
getSymbolForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang,
MachineModuleInfo *MMI,
bool &IsIndirect, bool &IsPCRel) const {
// The mach-o version of this method defaults to returning a stub reference.
IsIndirect = true;
IsPCRel = false;
SmallString<128> Name;
Mang->getNameWithPrefix(Name, GV, true);
Name += "$non_lazy_ptr";
return MCSymbolRefExpr::Create(Name.str(), getContext());
}
//===----------------------------------------------------------------------===//
// COFF
//===----------------------------------------------------------------------===//
typedef StringMap<const MCSectionCOFF*> COFFUniqueMapTy;
TargetLoweringObjectFileCOFF::~TargetLoweringObjectFileCOFF() {
delete (COFFUniqueMapTy*)UniquingMap;
}
const MCSection *TargetLoweringObjectFileCOFF::
getCOFFSection(StringRef Name, bool isDirective, SectionKind Kind) const {
// Create the map if it doesn't already exist.
if (UniquingMap == 0)
UniquingMap = new MachOUniqueMapTy();
COFFUniqueMapTy &Map = *(COFFUniqueMapTy*)UniquingMap;
// Do the lookup, if we have a hit, return it.
const MCSectionCOFF *&Entry = Map[Name];
if (Entry) return Entry;
return Entry = MCSectionCOFF::Create(Name, isDirective, Kind, getContext());
}
void TargetLoweringObjectFileCOFF::Initialize(MCContext &Ctx,
const TargetMachine &TM) {
if (UniquingMap != 0)
((COFFUniqueMapTy*)UniquingMap)->clear();
TargetLoweringObjectFile::Initialize(Ctx, TM);
TextSection = getCOFFSection("\t.text", true, SectionKind::getText());
DataSection = getCOFFSection("\t.data", true, SectionKind::getDataRel());
StaticCtorSection =
getCOFFSection(".ctors", false, SectionKind::getDataRel());
StaticDtorSection =
getCOFFSection(".dtors", false, SectionKind::getDataRel());
// FIXME: We're emitting LSDA info into a readonly section on COFF, even
// though it contains relocatable pointers. In PIC mode, this is probably a
// big runtime hit for C++ apps. Either the contents of the LSDA need to be
// adjusted or this should be a data section.
LSDASection =
getCOFFSection(".gcc_except_table", false, SectionKind::getReadOnly());
EHFrameSection =
getCOFFSection(".eh_frame", false, SectionKind::getDataRel());
// Debug info.
// FIXME: Don't use 'directive' mode here.
DwarfAbbrevSection =
getCOFFSection("\t.section\t.debug_abbrev,\"dr\"",
true, SectionKind::getMetadata());
DwarfInfoSection =
getCOFFSection("\t.section\t.debug_info,\"dr\"",
true, SectionKind::getMetadata());
DwarfLineSection =
getCOFFSection("\t.section\t.debug_line,\"dr\"",
true, SectionKind::getMetadata());
DwarfFrameSection =
getCOFFSection("\t.section\t.debug_frame,\"dr\"",
true, SectionKind::getMetadata());
DwarfPubNamesSection =
getCOFFSection("\t.section\t.debug_pubnames,\"dr\"",
true, SectionKind::getMetadata());
DwarfPubTypesSection =
getCOFFSection("\t.section\t.debug_pubtypes,\"dr\"",
true, SectionKind::getMetadata());
DwarfStrSection =
getCOFFSection("\t.section\t.debug_str,\"dr\"",
true, SectionKind::getMetadata());
DwarfLocSection =
getCOFFSection("\t.section\t.debug_loc,\"dr\"",
true, SectionKind::getMetadata());
DwarfARangesSection =
getCOFFSection("\t.section\t.debug_aranges,\"dr\"",
true, SectionKind::getMetadata());
DwarfRangesSection =
getCOFFSection("\t.section\t.debug_ranges,\"dr\"",
true, SectionKind::getMetadata());
DwarfMacroInfoSection =
getCOFFSection("\t.section\t.debug_macinfo,\"dr\"",
true, SectionKind::getMetadata());
}
const MCSection *TargetLoweringObjectFileCOFF::
getExplicitSectionGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler *Mang, const TargetMachine &TM) const {
return getCOFFSection(GV->getSection().c_str(), false, Kind);
}
static const char *getCOFFSectionPrefixForUniqueGlobal(SectionKind Kind) {
if (Kind.isText())
return ".text$linkonce";
if (Kind.isWriteable())
return ".data$linkonce";
return ".rdata$linkonce";
}
const MCSection *TargetLoweringObjectFileCOFF::
SelectSectionForGlobal(const GlobalValue *GV, SectionKind Kind,
Mangler *Mang, const TargetMachine &TM) const {
assert(!Kind.isThreadLocal() && "Doesn't support TLS");
// 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()) {
const char *Prefix = getCOFFSectionPrefixForUniqueGlobal(Kind);
SmallString<128> Name(Prefix, Prefix+strlen(Prefix));
Mang->getNameWithPrefix(Name, GV, false);
return getCOFFSection(Name.str(), false, Kind);
}
if (Kind.isText())
return getTextSection();
return getDataSection();
}
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