| //===-- 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/MCStreamer.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/Dwarf.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/raw_ostream.h" |
| #include "llvm/ADT/SmallString.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; |
| |
| IsFunctionEHSymbolGlobal = false; |
| IsFunctionEHFrameSymbolPrivate = true; |
| SupportsWeakOmittedEHFrame = true; |
| } |
| |
| 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; |
| } |
| |
| /// getExprForDwarfGlobalReference - Return an MCExpr to use for a |
| /// reference to the specified global variable from exception |
| /// handling information. |
| const MCExpr *TargetLoweringObjectFile:: |
| getExprForDwarfGlobalReference(const GlobalValue *GV, Mangler *Mang, |
| MachineModuleInfo *MMI, unsigned Encoding, |
| MCStreamer &Streamer) const { |
| const MCSymbol *Sym = Mang->getSymbol(GV); |
| return getExprForDwarfReference(Sym, Mang, MMI, Encoding, Streamer); |
| } |
| |
| const MCExpr *TargetLoweringObjectFile:: |
| getExprForDwarfReference(const MCSymbol *Sym, Mangler *Mang, |
| MachineModuleInfo *MMI, unsigned Encoding, |
| MCStreamer &Streamer) const { |
| const MCExpr *Res = MCSymbolRefExpr::Create(Sym, getContext()); |
| |
| switch (Encoding & 0xF0) { |
| default: |
| report_fatal_error("We do not support this DWARF encoding yet!"); |
| case dwarf::DW_EH_PE_absptr: |
| // Do nothing special |
| return Res; |
| case dwarf::DW_EH_PE_pcrel: { |
| // Emit a label to the streamer for the current position. This gives us |
| // .-foo addressing. |
| MCSymbol *PCSym = getContext().CreateTempSymbol(); |
| Streamer.EmitLabel(PCSym); |
| const MCExpr *PC = MCSymbolRefExpr::Create(PCSym, getContext()); |
| return MCBinaryExpr::CreateSub(Res, PC, getContext()); |
| } |
| } |
| } |
| |
| unsigned TargetLoweringObjectFile::getPersonalityEncoding() const { |
| return dwarf::DW_EH_PE_absptr; |
| } |
| |
| unsigned TargetLoweringObjectFile::getLSDAEncoding() const { |
| return dwarf::DW_EH_PE_absptr; |
| } |
| |
| unsigned TargetLoweringObjectFile::getFDEEncoding() const { |
| return dwarf::DW_EH_PE_absptr; |
| } |
| |
| unsigned TargetLoweringObjectFile::getTTypeEncoding() const { |
| return dwarf::DW_EH_PE_absptr; |
| } |
| |