lib/MC/MCSectionELF.cpp

   1 //===- lib/MC/MCSectionELF.cpp - ELF Code Section Representation ----------===//
   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 #include "llvm/MC/MCSectionELF.h"
  11 #include "llvm/MC/MCAsmInfo.h"
  12 #include "llvm/MC/MCContext.h"
  13 #include "llvm/MC/MCSymbol.h"
  14 #include "llvm/Support/ELF.h"
  15 #include "llvm/Support/raw_ostream.h"
  16
  17 using namespace llvm;
  18
  19 MCSectionELF::~MCSectionELF() {} // anchor.
  20
  21 // ShouldOmitSectionDirective - Decides whether a '.section' directive
  22 // should be printed before the section name
  23 bool MCSectionELF::ShouldOmitSectionDirective(StringRef Name,
  24                                               const MCAsmInfo &MAI) const {
  25
  26   // FIXME: Does .section .bss/.data/.text work everywhere??
  27   if (Name == ".text" || Name == ".data" ||
  28       (Name == ".bss" && !MAI.usesELFSectionDirectiveForBSS()))
  29     return true;
  30
  31   return false;
  32 }
  33
  34 void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI,
  35                                         raw_ostream &OS) const {
  36
  37   if (ShouldOmitSectionDirective(SectionName, MAI)) {
  38     OS << '\t' << getSectionName() << '\n';
  39     return;
  40   }
  41
  42   OS << "\t.section\t" << getSectionName();
  43
  44   // Handle the weird solaris syntax if desired.
  45   if (MAI.usesSunStyleELFSectionSwitchSyntax() &&
  46       !(Flags & ELF::SHF_MERGE)) {
  47     if (Flags & ELF::SHF_ALLOC)
  48       OS << ",#alloc";
  49     if (Flags & ELF::SHF_EXECINSTR)
  50       OS << ",#execinstr";
  51     if (Flags & ELF::SHF_WRITE)
  52       OS << ",#write";
  53     if (Flags & ELF::SHF_TLS)
  54       OS << ",#tls";
  55     OS << '\n';
  56     return;
  57   }
  58
  59   OS << ",\"";
  60   if (Flags & ELF::SHF_ALLOC)
  61     OS << 'a';
  62   if (Flags & ELF::SHF_EXECINSTR)
  63     OS << 'x';
  64   if (Flags & ELF::SHF_WRITE)
  65     OS << 'w';
  66   if (Flags & ELF::SHF_MERGE)
  67     OS << 'M';
  68   if (Flags & ELF::SHF_STRINGS)
  69     OS << 'S';
  70   if (Flags & ELF::SHF_TLS)
  71     OS << 'T';
  72
  73   // If there are target-specific flags, print them.
  74   if (Flags & ELF::XCORE_SHF_CP_SECTION)
  75     OS << 'c';
  76   if (Flags & ELF::XCORE_SHF_DP_SECTION)
  77     OS << 'd';
  78
  79   OS << '"';
  80
  81   OS << ',';
  82
  83   // If comment string is '@', e.g. as on ARM - use '%' instead
  84   if (MAI.getCommentString()[0] == '@')
  85     OS << '%';
  86   else
  87     OS << '@';
  88
  89   if (Type == ELF::SHT_INIT_ARRAY)
  90     OS << "init_array";
  91   else if (Type == ELF::SHT_FINI_ARRAY)
  92     OS << "fini_array";
  93   else if (Type == ELF::SHT_PREINIT_ARRAY)
  94     OS << "preinit_array";
  95   else if (Type == ELF::SHT_NOBITS)
  96     OS << "nobits";
  97   else if (Type == ELF::SHT_NOTE)
  98     OS << "note";
  99   else if (Type == ELF::SHT_PROGBITS)
 100     OS << "progbits";
 101
 102   if (EntrySize) {
 103     assert(Flags & ELF::SHF_MERGE);
 104     OS << "," << EntrySize;
 105   }
 106
 107   OS << '\n';
 108 }
 109
 110 bool MCSectionELF::UseCodeAlign() const {
 111   return getFlags() & ELF::SHF_EXECINSTR;
 112 }
 113
 114 bool MCSectionELF::isVirtualSection() const {
 115   return getType() == ELF::SHT_NOBITS;
 116 }
 117
 118 // HasCommonSymbols - True if this section holds common symbols, this is
 119 // indicated on the ELF object file by a symbol with SHN_COMMON section
 120 // header index.
 121 bool MCSectionELF::HasCommonSymbols() const {
 122
 123   if (StringRef(SectionName).startswith(".gnu.linkonce."))
 124     return true;
 125
 126   return false;
 127 }
 128
 129 unsigned MCSectionELF::DetermineEntrySize(SectionKind Kind) {
 130   if (Kind.isMergeable1ByteCString()) return 1;
 131   if (Kind.isMergeable2ByteCString()) return 2;
 132   if (Kind.isMergeable4ByteCString()) return 4;
 133   if (Kind.isMergeableConst4())       return 4;
 134   if (Kind.isMergeableConst8())       return 8;
 135   if (Kind.isMergeableConst16())      return 16;
 136   return 0;
 137 }