lib/Target/TargetAsmInfo.cpp

   1 //===-- TargetAsmInfo.cpp - Asm Info ---------------------------------------==//
   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.
  12 //
  13 //===----------------------------------------------------------------------===//
  14
  15 #include "llvm/Constants.h"
  16 #include "llvm/DerivedTypes.h"
  17 #include "llvm/GlobalVariable.h"
  18 #include "llvm/Function.h"
  19 #include "llvm/Module.h"
  20 #include "llvm/Type.h"
  21 #include "llvm/Target/TargetAsmInfo.h"
  22 #include "llvm/Target/TargetMachine.h"
  23 #include "llvm/Target/TargetOptions.h"
  24 #include "llvm/Support/Dwarf.h"
  25 #include <cctype>
  26 #include <cstring>
  27
  28 using namespace llvm;
  29
  30 void TargetAsmInfo::fillDefaultValues() {
  31   BSSSection = "\t.bss";
  32   BSSSection_ = 0;
  33   ReadOnlySection = 0;
  34   SmallDataSection = 0;
  35   SmallBSSSection = 0;
  36   SmallRODataSection = 0;
  37   TLSDataSection = 0;
  38   TLSBSSSection = 0;
  39   ZeroFillDirective = 0;
  40   NonexecutableStackDirective = 0;
  41   NeedsSet = false;
  42   MaxInstLength = 4;
  43   PCSymbol = "$";
  44   SeparatorChar = ';';
  45   CommentString = "#";
  46   GlobalPrefix = "";
  47   PrivateGlobalPrefix = ".";
  48   LessPrivateGlobalPrefix = "";
  49   JumpTableSpecialLabelPrefix = 0;
  50   GlobalVarAddrPrefix = "";
  51   GlobalVarAddrSuffix = "";
  52   FunctionAddrPrefix = "";
  53   FunctionAddrSuffix = "";
  54   PersonalityPrefix = "";
  55   PersonalitySuffix = "";
  56   NeedsIndirectEncoding = false;
  57   InlineAsmStart = "#APP";
  58   InlineAsmEnd = "#NO_APP";
  59   AssemblerDialect = 0;
  60   StringConstantPrefix = ".str";
  61   ZeroDirective = "\t.zero\t";
  62   ZeroDirectiveSuffix = 0;
  63   AsciiDirective = "\t.ascii\t";
  64   AscizDirective = "\t.asciz\t";
  65   Data8bitsDirective = "\t.byte\t";
  66   Data16bitsDirective = "\t.short\t";
  67   Data32bitsDirective = "\t.long\t";
  68   Data64bitsDirective = "\t.quad\t";
  69   AlignDirective = "\t.align\t";
  70   AlignmentIsInBytes = true;
  71   TextAlignFillValue = 0;
  72   SwitchToSectionDirective = "\t.section\t";
  73   TextSectionStartSuffix = "";
  74   DataSectionStartSuffix = "";
  75   SectionEndDirectiveSuffix = 0;
  76   ConstantPoolSection = "\t.section .rodata";
  77   JumpTableDataSection = "\t.section .rodata";
  78   JumpTableDirective = 0;
  79   CStringSection = 0;
  80   CStringSection_ = 0;
  81   // FIXME: Flags are ELFish - replace with normal section stuff.
  82   StaticCtorsSection = "\t.section .ctors,\"aw\",@progbits";
  83   StaticDtorsSection = "\t.section .dtors,\"aw\",@progbits";
  84   GlobalDirective = "\t.globl\t";
  85   SetDirective = 0;
  86   LCOMMDirective = 0;
  87   COMMDirective = "\t.comm\t";
  88   COMMDirectiveTakesAlignment = true;
  89   HasDotTypeDotSizeDirective = true;
  90   HasSingleParameterDotFile = true;
  91   UsedDirective = 0;
  92   WeakRefDirective = 0;
  93   WeakDefDirective = 0;
  94   // FIXME: These are ELFish - move to ELFTAI.
  95   HiddenDirective = "\t.hidden\t";
  96   ProtectedDirective = "\t.protected\t";
  97   AbsoluteDebugSectionOffsets = false;
  98   AbsoluteEHSectionOffsets = false;
  99   HasLEB128 = false;
 100   HasDotLocAndDotFile = false;
 101   SupportsDebugInformation = false;
 102   SupportsExceptionHandling = false;
 103   DwarfRequiresFrameSection = true;
 104   DwarfUsesInlineInfoSection = false;
 105   SupportsMacInfoSection = true;
 106   NonLocalEHFrameLabel = false;
 107   GlobalEHDirective = 0;
 108   SupportsWeakOmittedEHFrame = true;
 109   DwarfSectionOffsetDirective = 0;
 110   DwarfAbbrevSection = ".debug_abbrev";
 111   DwarfInfoSection = ".debug_info";
 112   DwarfLineSection = ".debug_line";
 113   DwarfFrameSection = ".debug_frame";
 114   DwarfPubNamesSection = ".debug_pubnames";
 115   DwarfPubTypesSection = ".debug_pubtypes";
 116   DwarfDebugInlineSection = ".debug_inlined";
 117   DwarfStrSection = ".debug_str";
 118   DwarfLocSection = ".debug_loc";
 119   DwarfARangesSection = ".debug_aranges";
 120   DwarfRangesSection = ".debug_ranges";
 121   DwarfMacInfoSection = ".debug_macinfo";
 122   DwarfEHFrameSection = ".eh_frame";
 123   DwarfExceptionSection = ".gcc_except_table";
 124   AsmTransCBE = 0;
 125   TextSection = getUnnamedSection("\t.text", SectionFlags::Code);
 126   DataSection = getUnnamedSection("\t.data", SectionFlags::Writeable);
 127 }
 128
 129 TargetAsmInfo::TargetAsmInfo(const TargetMachine &tm)
 130   : TM(tm) {
 131   fillDefaultValues();
 132 }
 133
 134 TargetAsmInfo::~TargetAsmInfo() {
 135 }
 136
 137 /// Measure the specified inline asm to determine an approximation of its
 138 /// length.
 139 /// Comments (which run till the next SeparatorChar or newline) do not
 140 /// count as an instruction.
 141 /// Any other non-whitespace text is considered an instruction, with
 142 /// multiple instructions separated by SeparatorChar or newlines.
 143 /// Variable-length instructions are not handled here; this function
 144 /// may be overloaded in the target code to do that.
 145 unsigned TargetAsmInfo::getInlineAsmLength(const char *Str) const {
 146   // Count the number of instructions in the asm.
 147   bool atInsnStart = true;
 148   unsigned Length = 0;
 149   for (; *Str; ++Str) {
 150     if (*Str == '\n' || *Str == SeparatorChar)
 151       atInsnStart = true;
 152     if (atInsnStart && !isspace(*Str)) {
 153       Length += MaxInstLength;
 154       atInsnStart = false;
 155     }
 156     if (atInsnStart && strncmp(Str, CommentString, strlen(CommentString))==0)
 157       atInsnStart = false;
 158   }
 159
 160   return Length;
 161 }
 162
 163 unsigned TargetAsmInfo::PreferredEHDataFormat(DwarfEncoding::Target Reason,
 164                                               bool Global) const {
 165   return dwarf::DW_EH_PE_absptr;
 166 }
 167
 168 static bool isSuitableForBSS(const GlobalVariable *GV) {
 169   if (!GV->hasInitializer())
 170     return true;
 171
 172   // Leave constant zeros in readonly constant sections, so they can be shared
 173   Constant *C = GV->getInitializer();
 174   return (C->isNullValue() && !GV->isConstant() && !NoZerosInBSS);
 175 }
 176
 177 static bool isConstantString(const Constant *C) {
 178   // First check: is we have constant array of i8 terminated with zero
 179   const ConstantArray *CVA = dyn_cast<ConstantArray>(C);
 180   // Check, if initializer is a null-terminated string
 181   if (CVA && CVA->isCString())
 182     return true;
 183
 184   // Another possibility: [1 x i8] zeroinitializer
 185   if (isa<ConstantAggregateZero>(C)) {
 186     if (const ArrayType *Ty = dyn_cast<ArrayType>(C->getType())) {
 187       return (Ty->getElementType() == Type::Int8Ty &&
 188               Ty->getNumElements() == 1);
 189     }
 190   }
 191
 192   return false;
 193 }
 194
 195 unsigned TargetAsmInfo::RelocBehaviour() const {
 196   // By default - all relocations in PIC mode would force symbol to be
 197   // placed in r/w section.
 198   return (TM.getRelocationModel() != Reloc::Static ?
 199           Reloc::LocalOrGlobal : Reloc::None);
 200 }
 201
 202 SectionKind::Kind
 203 TargetAsmInfo::SectionKindForGlobal(const GlobalValue *GV) const {
 204   // Early exit - functions should be always in text sections.
 205   if (isa<Function>(GV))
 206     return SectionKind::Text;
 207
 208   const GlobalVariable* GVar = dyn_cast<GlobalVariable>(GV);
 209   bool isThreadLocal = GVar->isThreadLocal();
 210   assert(GVar && "Invalid global value for section selection");
 211
 212   if (isSuitableForBSS(GVar)) {
 213     // Variable can be easily put to BSS section.
 214     return (isThreadLocal ? SectionKind::ThreadBSS : SectionKind::BSS);
 215   } else if (GVar->isConstant() && !isThreadLocal) {
 216     // Now we know, that varible has initializer and it is constant. We need to
 217     // check its initializer to decide, which section to output it into. Also
 218     // note, there is no thread-local r/o section.
 219     Constant *C = GVar->getInitializer();
 220     if (C->ContainsRelocations(Reloc::LocalOrGlobal)) {
 221       // Decide, whether it is still possible to put symbol into r/o section.
 222       unsigned Reloc = RelocBehaviour();
 223
 224       // We already did a query for 'all' relocs, thus - early exits.
 225       if (Reloc == Reloc::LocalOrGlobal)
 226         return SectionKind::Data;
 227       else if (Reloc == Reloc::None)
 228         return SectionKind::ROData;
 229       else {
 230         // Ok, target wants something funny. Honour it.
 231         return (C->ContainsRelocations(Reloc) ?
 232                 SectionKind::Data : SectionKind::ROData);
 233       }
 234     } else {
 235       // Check, if initializer is a null-terminated string
 236       if (isConstantString(C))
 237         return SectionKind::RODataMergeStr;
 238       else
 239         return SectionKind::RODataMergeConst;
 240     }
 241   }
 242
 243   // Variable either is not constant or thread-local - output to data section.
 244   return (isThreadLocal ? SectionKind::ThreadData : SectionKind::Data);
 245 }
 246
 247 unsigned
 248 TargetAsmInfo::SectionFlagsForGlobal(const GlobalValue *GV,
 249                                      const char* Name) const {
 250   unsigned Flags = SectionFlags::None;
 251
 252   // Decode flags from global itself.
 253   if (GV) {
 254     SectionKind::Kind Kind = SectionKindForGlobal(GV);
 255     switch (Kind) {
 256      case SectionKind::Text:
 257       Flags |= SectionFlags::Code;
 258       break;
 259      case SectionKind::ThreadData:
 260      case SectionKind::ThreadBSS:
 261       Flags |= SectionFlags::TLS;
 262       // FALLS THROUGH
 263      case SectionKind::Data:
 264      case SectionKind::DataRel:
 265      case SectionKind::DataRelLocal:
 266      case SectionKind::DataRelRO:
 267      case SectionKind::DataRelROLocal:
 268      case SectionKind::BSS:
 269       Flags |= SectionFlags::Writeable;
 270       break;
 271      case SectionKind::ROData:
 272      case SectionKind::RODataMergeStr:
 273      case SectionKind::RODataMergeConst:
 274       // No additional flags here
 275       break;
 276      case SectionKind::SmallData:
 277      case SectionKind::SmallBSS:
 278       Flags |= SectionFlags::Writeable;
 279       // FALLS THROUGH
 280      case SectionKind::SmallROData:
 281       Flags |= SectionFlags::Small;
 282       break;
 283      default:
 284       assert(0 && "Unexpected section kind!");
 285     }
 286
 287     if (GV->isWeakForLinker())
 288       Flags |= SectionFlags::Linkonce;
 289   }
 290
 291   // Add flags from sections, if any.
 292   if (Name && *Name) {
 293     Flags |= SectionFlags::Named;
 294
 295     // Some lame default implementation based on some magic section names.
 296     if (strncmp(Name, ".gnu.linkonce.b.", 16) == 0 ||
 297         strncmp(Name, ".llvm.linkonce.b.", 17) == 0 ||
 298         strncmp(Name, ".gnu.linkonce.sb.", 17) == 0 ||
 299         strncmp(Name, ".llvm.linkonce.sb.", 18) == 0)
 300       Flags |= SectionFlags::BSS;
 301     else if (strcmp(Name, ".tdata") == 0 ||
 302              strncmp(Name, ".tdata.", 7) == 0 ||
 303              strncmp(Name, ".gnu.linkonce.td.", 17) == 0 ||
 304              strncmp(Name, ".llvm.linkonce.td.", 18) == 0)
 305       Flags |= SectionFlags::TLS;
 306     else if (strcmp(Name, ".tbss") == 0 ||
 307              strncmp(Name, ".tbss.", 6) == 0 ||
 308              strncmp(Name, ".gnu.linkonce.tb.", 17) == 0 ||
 309              strncmp(Name, ".llvm.linkonce.tb.", 18) == 0)
 310       Flags |= SectionFlags::BSS | SectionFlags::TLS;
 311   }
 312
 313   return Flags;
 314 }
 315
 316 const Section*
 317 TargetAsmInfo::SectionForGlobal(const GlobalValue *GV) const {
 318   const Section* S;
 319   // Select section name
 320   if (GV->hasSection()) {
 321     // Honour section already set, if any
 322     unsigned Flags = SectionFlagsForGlobal(GV,
 323                                            GV->getSection().c_str());
 324     S = getNamedSection(GV->getSection().c_str(), Flags);
 325   } else {
 326     // Use default section depending on the 'type' of global
 327     S = SelectSectionForGlobal(GV);
 328   }
 329
 330   return S;
 331 }
 332
 333 // Lame default implementation. Calculate the section name for global.
 334 const Section*
 335 TargetAsmInfo::SelectSectionForGlobal(const GlobalValue *GV) const {
 336   SectionKind::Kind Kind = SectionKindForGlobal(GV);
 337
 338   if (GV->isWeakForLinker()) {
 339     std::string Name = UniqueSectionForGlobal(GV, Kind);
 340     unsigned Flags = SectionFlagsForGlobal(GV, Name.c_str());
 341     return getNamedSection(Name.c_str(), Flags);
 342   } else {
 343     if (Kind == SectionKind::Text)
 344       return getTextSection();
 345     else if (isBSS(Kind) && getBSSSection_())
 346       return getBSSSection_();
 347     else if (getReadOnlySection() && SectionKind::isReadOnly(Kind))
 348       return getReadOnlySection();
 349   }
 350
 351   return getDataSection();
 352 }
 353
 354 // Lame default implementation. Calculate the section name for machine const.
 355 const Section*
 356 TargetAsmInfo::SelectSectionForMachineConst(const Type *Ty) const {
 357   // FIXME: Support data.rel stuff someday
 358   return getDataSection();
 359 }
 360
 361 std::string
 362 TargetAsmInfo::UniqueSectionForGlobal(const GlobalValue* GV,
 363                                       SectionKind::Kind Kind) const {
 364   switch (Kind) {
 365    case SectionKind::Text:
 366     return ".gnu.linkonce.t." + GV->getName();
 367    case SectionKind::Data:
 368     return ".gnu.linkonce.d." + GV->getName();
 369    case SectionKind::DataRel:
 370     return ".gnu.linkonce.d.rel" + GV->getName();
 371    case SectionKind::DataRelLocal:
 372     return ".gnu.linkonce.d.rel.local" + GV->getName();
 373    case SectionKind::DataRelRO:
 374     return ".gnu.linkonce.d.rel.ro" + GV->getName();
 375    case SectionKind::DataRelROLocal:
 376     return ".gnu.linkonce.d.rel.ro.local" + GV->getName();
 377    case SectionKind::SmallData:
 378     return ".gnu.linkonce.s." + GV->getName();
 379    case SectionKind::BSS:
 380     return ".gnu.linkonce.b." + GV->getName();
 381    case SectionKind::SmallBSS:
 382     return ".gnu.linkonce.sb." + GV->getName();
 383    case SectionKind::ROData:
 384    case SectionKind::RODataMergeConst:
 385    case SectionKind::RODataMergeStr:
 386     return ".gnu.linkonce.r." + GV->getName();
 387    case SectionKind::SmallROData:
 388     return ".gnu.linkonce.s2." + GV->getName();
 389    case SectionKind::ThreadData:
 390     return ".gnu.linkonce.td." + GV->getName();
 391    case SectionKind::ThreadBSS:
 392     return ".gnu.linkonce.tb." + GV->getName();
 393    default:
 394     assert(0 && "Unknown section kind");
 395   }
 396   return NULL;
 397 }
 398
 399 const Section*
 400 TargetAsmInfo::getNamedSection(const char *Name, unsigned Flags,
 401                                bool Override) const {
 402   Section& S = Sections[Name];
 403
 404   // This is newly-created section, set it up properly.
 405   if (S.Flags == SectionFlags::Invalid || Override) {
 406     S.Flags = Flags | SectionFlags::Named;
 407     S.Name = Name;
 408   }
 409
 410   return &S;
 411 }
 412
 413 const Section*
 414 TargetAsmInfo::getUnnamedSection(const char *Directive, unsigned Flags,
 415                                  bool Override) const {
 416   Section& S = Sections[Directive];
 417
 418   // This is newly-created section, set it up properly.
 419   if (S.Flags == SectionFlags::Invalid || Override) {
 420     S.Flags = Flags & ~SectionFlags::Named;
 421     S.Name = Directive;
 422   }
 423
 424   return &S;
 425 }
 426
 427 const std::string&
 428 TargetAsmInfo::getSectionFlags(unsigned Flags) const {
 429   SectionFlags::FlagsStringsMapType::iterator I = FlagsStrings.find(Flags);
 430
 431   // We didn't print these flags yet, print and save them to map. This reduces
 432   // amount of heap trashing due to std::string construction / concatenation.
 433   if (I == FlagsStrings.end())
 434     I = FlagsStrings.insert(std::make_pair(Flags,
 435                                            printSectionFlags(Flags))).first;
 436
 437   return I->second;
 438 }
 439
 440 unsigned TargetAsmInfo::getULEB128Size(unsigned Value) {
 441   unsigned Size = 0;
 442   do {
 443     Value >>= 7;
 444     Size += sizeof(int8_t);
 445   } while (Value);
 446   return Size;
 447 }
 448
 449 unsigned TargetAsmInfo::getSLEB128Size(int Value) {
 450   unsigned Size = 0;
 451   int Sign = Value >> (8 * sizeof(Value) - 1);
 452   bool IsMore;
 453
 454   do {
 455     unsigned Byte = Value & 0x7f;
 456     Value >>= 7;
 457     IsMore = Value != Sign || ((Byte ^ Sign) & 0x40) != 0;
 458     Size += sizeof(int8_t);
 459   } while (IsMore);
 460   return Size;
 461 }