lib/Target/DarwinTargetAsmInfo.cpp

   1 //===-- DarwinTargetAsmInfo.cpp - Darwin asm properties ---------*- C++ -*-===//
   2 //
   3 //                     The LLVM Compiler Infrastructure
   4 //
   5 // This file is distributed under the University of Illinois Open Source
   6 // License. See LICENSE.TXT for details.
   7 //
   8 //===----------------------------------------------------------------------===//
   9 //
  10 // This file defines target asm properties related what form asm statements
  11 // should take in general on Darwin-based targets
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Constants.h"
  16 #include "llvm/DerivedTypes.h"
  17 #include "llvm/Function.h"
  18 #include "llvm/GlobalVariable.h"
  19 #include "llvm/ADT/StringExtras.h"
  20 #include "llvm/Support/ErrorHandling.h"
  21 #include "llvm/Support/Mangler.h"
  22 #include "llvm/Target/DarwinTargetAsmInfo.h"
  23 #include "llvm/Target/TargetMachine.h"
  24 #include "llvm/Target/TargetData.h"
  25
  26 using namespace llvm;
  27
  28 DarwinTargetAsmInfo::DarwinTargetAsmInfo(const TargetMachine &TM)
  29   : TargetAsmInfo(TM) {
  30
  31   CStringSection_ = getUnnamedSection("\t.cstring",
  32                                 SectionFlags::Mergeable |SectionFlags::Strings);
  33   FourByteConstantSection = getUnnamedSection("\t.literal4\n",
  34                                               SectionFlags::Mergeable);
  35   EightByteConstantSection = getUnnamedSection("\t.literal8\n",
  36                                                SectionFlags::Mergeable);
  37
  38   // Note: 16-byte constant section is subtarget specific and should be provided
  39   // there, if needed.
  40   SixteenByteConstantSection = 0;
  41
  42   ReadOnlySection = getUnnamedSection("\t.const\n", SectionFlags::None);
  43
  44   TextCoalSection =
  45     getNamedSection("\t__TEXT,__textcoal_nt,coalesced,pure_instructions",
  46                     SectionFlags::Code);
  47   ConstTextCoalSection = getNamedSection("\t__TEXT,__const_coal,coalesced",
  48                                          SectionFlags::None);
  49   ConstDataCoalSection = getNamedSection("\t__DATA,__const_coal,coalesced",
  50                                          SectionFlags::None);
  51   ConstDataSection = getUnnamedSection(".const_data", SectionFlags::None);
  52   DataCoalSection = getNamedSection("\t__DATA,__datacoal_nt,coalesced",
  53                                     SectionFlags::Writeable);
  54
  55
  56   // Common settings for all Darwin targets.
  57   // Syntax:
  58   GlobalPrefix = "_";
  59   PrivateGlobalPrefix = "L";
  60   LinkerPrivateGlobalPrefix = "l";  // Marker for some ObjC metadata
  61   NeedsSet = true;
  62   NeedsIndirectEncoding = true;
  63   AllowQuotesInName = true;
  64   HasSingleParameterDotFile = false;
  65
  66   // In non-PIC modes, emit a special label before jump tables so that the
  67   // linker can perform more accurate dead code stripping.  We do not check the
  68   // relocation model here since it can be overridden later.
  69   JumpTableSpecialLabelPrefix = "l";
  70
  71   // Directives:
  72   WeakDefDirective = "\t.weak_definition ";
  73   WeakRefDirective = "\t.weak_reference ";
  74   HiddenDirective = "\t.private_extern ";
  75
  76   // Sections:
  77   CStringSection = "\t.cstring";
  78   JumpTableDataSection = "\t.const\n";
  79   BSSSection = 0;
  80
  81   if (TM.getRelocationModel() == Reloc::Static) {
  82     StaticCtorsSection = ".constructor";
  83     StaticDtorsSection = ".destructor";
  84   } else {
  85     StaticCtorsSection = ".mod_init_func";
  86     StaticDtorsSection = ".mod_term_func";
  87   }
  88
  89   // _foo.eh symbols are currently always exported so that the linker knows
  90   // about them.  This may not strictly be necessary on 10.6 and later, but it
  91   // doesn't hurt anything.
  92   Is_EHSymbolPrivate = false;
  93
  94   DwarfAbbrevSection = ".section __DWARF,__debug_abbrev,regular,debug";
  95   DwarfInfoSection = ".section __DWARF,__debug_info,regular,debug";
  96   DwarfLineSection = ".section __DWARF,__debug_line,regular,debug";
  97   DwarfFrameSection = ".section __DWARF,__debug_frame,regular,debug";
  98   DwarfPubNamesSection = ".section __DWARF,__debug_pubnames,regular,debug";
  99   DwarfPubTypesSection = ".section __DWARF,__debug_pubtypes,regular,debug";
 100   DwarfStrSection = ".section __DWARF,__debug_str,regular,debug";
 101   DwarfLocSection = ".section __DWARF,__debug_loc,regular,debug";
 102   DwarfARangesSection = ".section __DWARF,__debug_aranges,regular,debug";
 103   DwarfRangesSection = ".section __DWARF,__debug_ranges,regular,debug";
 104   DwarfMacroInfoSection = ".section __DWARF,__debug_macinfo,regular,debug";
 105 }
 106
 107 /// emitUsedDirectiveFor - On Darwin, internally linked data beginning with
 108 /// the PrivateGlobalPrefix or the LinkerPrivateGlobalPrefix does not have the
 109 /// directive emitted (this occurs in ObjC metadata).
 110 bool DarwinTargetAsmInfo::emitUsedDirectiveFor(const GlobalValue* GV,
 111                                                Mangler *Mang) const {
 112   if (!GV) return false;
 113
 114   // Check whether the mangled name has the "Private" or "LinkerPrivate" prefix.
 115   if (GV->hasLocalLinkage() && !isa<Function>(GV)) {
 116     // FIXME: ObjC metadata is currently emitted as internal symbols that have
 117     // \1L and \0l prefixes on them.  Fix them to be Private/LinkerPrivate and
 118     // this horrible hack can go away.
 119     const std::string &Name = Mang->getMangledName(GV);
 120     if (Name[0] == 'L' || Name[0] == 'l')
 121       return false;
 122   }
 123
 124   return true;
 125 }
 126
 127 const Section*
 128 DarwinTargetAsmInfo::SelectSectionForGlobal(const GlobalValue *GV,
 129                                             SectionKind::Kind Kind) const {
 130   bool isWeak = GV->isWeakForLinker();
 131   bool isNonStatic = TM.getRelocationModel() != Reloc::Static;
 132
 133   switch (Kind) {
 134   case SectionKind::ThreadData:
 135   case SectionKind::ThreadBSS:
 136     llvm_unreachable("Darwin doesn't support TLS");
 137   case SectionKind::Text:
 138     if (isWeak)
 139       return TextCoalSection;
 140     return TextSection;
 141   case SectionKind::Data:
 142   case SectionKind::DataRelLocal:
 143   case SectionKind::DataRel:
 144   case SectionKind::BSS:
 145     if (cast<GlobalVariable>(GV)->isConstant())
 146       return isWeak ? ConstDataCoalSection : ConstDataSection;
 147     return isWeak ? DataCoalSection : DataSection;
 148
 149   case SectionKind::ROData:
 150   case SectionKind::DataRelRO:
 151   case SectionKind::DataRelROLocal:
 152     return (isWeak ? ConstDataCoalSection :
 153             (isNonStatic ? ConstDataSection : getReadOnlySection()));
 154   case SectionKind::RODataMergeStr:
 155     return (isWeak ?
 156             ConstTextCoalSection :
 157             MergeableStringSection(cast<GlobalVariable>(GV)));
 158   case SectionKind::RODataMergeConst: {
 159     if (isWeak) return ConstDataCoalSection;
 160     const Type *Ty = cast<GlobalVariable>(GV)->getInitializer()->getType();
 161     const TargetData *TD = TM.getTargetData();
 162     return getSectionForMergableConstant(TD->getTypeAllocSize(Ty), 0);
 163   }
 164   default:
 165     llvm_unreachable("Unsuported section kind for global");
 166   }
 167
 168   // FIXME: Do we have any extra special weird cases?
 169   return NULL;
 170 }
 171
 172 const Section*
 173 DarwinTargetAsmInfo::MergeableStringSection(const GlobalVariable *GV) const {
 174   const TargetData *TD = TM.getTargetData();
 175   Constant *C = cast<GlobalVariable>(GV)->getInitializer();
 176   const Type *Ty = cast<ArrayType>(C->getType())->getElementType();
 177
 178   unsigned Size = TD->getTypeAllocSize(Ty);
 179   if (Size) {
 180     unsigned Align = TD->getPreferredAlignment(GV);
 181     if (Align <= 32)
 182       return getCStringSection_();
 183   }
 184
 185   return getReadOnlySection();
 186 }
 187
 188 const Section *
 189 DarwinTargetAsmInfo::getSectionForMergableConstant(uint64_t Size,
 190                                                    unsigned ReloInfo) const {
 191   // If this constant requires a relocation, we have to put it in the data
 192   // segment, not in the text segment.
 193   if (ReloInfo != 0)
 194     return ConstDataSection;
 195
 196   switch (Size) {
 197   default: break;
 198   case 4:
 199     return FourByteConstantSection;
 200   case 8:
 201     return EightByteConstantSection;
 202   case 16:
 203     if (SixteenByteConstantSection)
 204       return SixteenByteConstantSection;
 205     break;
 206   }
 207
 208   return ReadOnlySection;  // .const
 209 }
 210