| //===-- 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; | 
 |  | 
 |   CommDirectiveSupportsAlignment = true; | 
 |   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->isZero()) | 
 |       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; | 
 | } | 
 |  |