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/raw_ostream.h"
  15 using namespace llvm;
  16
  17 MCSectionELF::~MCSectionELF() {} // anchor.
  18
  19 // ShouldOmitSectionDirective - Decides whether a '.section' directive
  20 // should be printed before the section name
  21 bool MCSectionELF::ShouldOmitSectionDirective(StringRef Name,
  22                                               const MCAsmInfo &MAI) const {
  23
  24   // FIXME: Does .section .bss/.data/.text work everywhere??
  25   if (Name == ".text" || Name == ".data" ||
  26       (Name == ".bss" && !MAI.usesELFSectionDirectiveForBSS()))
  27     return true;
  28
  29   return false;
  30 }
  31
  32 // ShouldPrintSectionType - Only prints the section type if supported
  33 bool MCSectionELF::ShouldPrintSectionType(unsigned Ty) const {
  34   if (IsExplicit && !(Ty == SHT_NOBITS || Ty == SHT_PROGBITS))
  35     return false;
  36
  37   return true;
  38 }
  39
  40 void MCSectionELF::PrintSwitchToSection(const MCAsmInfo &MAI,
  41                                         raw_ostream &OS) const {
  42
  43   if (ShouldOmitSectionDirective(SectionName, MAI)) {
  44     OS << '\t' << getSectionName() << '\n';
  45     return;
  46   }
  47
  48   OS << "\t.section\t" << getSectionName();
  49
  50   // Handle the weird solaris syntax if desired.
  51   if (MAI.usesSunStyleELFSectionSwitchSyntax() &&
  52       !(Flags & MCSectionELF::SHF_MERGE)) {
  53     if (Flags & MCSectionELF::SHF_ALLOC)
  54       OS << ",#alloc";
  55     if (Flags & MCSectionELF::SHF_EXECINSTR)
  56       OS << ",#execinstr";
  57     if (Flags & MCSectionELF::SHF_WRITE)
  58       OS << ",#write";
  59     if (Flags & MCSectionELF::SHF_TLS)
  60       OS << ",#tls";
  61     OS << '\n';
  62     return;
  63   }
  64
  65   OS << ",\"";
  66   if (Flags & MCSectionELF::SHF_ALLOC)
  67     OS << 'a';
  68   if (Flags & MCSectionELF::SHF_EXECINSTR)
  69     OS << 'x';
  70   if (Flags & MCSectionELF::SHF_WRITE)
  71     OS << 'w';
  72   if (Flags & MCSectionELF::SHF_MERGE)
  73     OS << 'M';
  74   if (Flags & MCSectionELF::SHF_STRINGS)
  75     OS << 'S';
  76   if (Flags & MCSectionELF::SHF_TLS)
  77     OS << 'T';
  78
  79   // If there are target-specific flags, print them.
  80   if (Flags & MCSectionELF::XCORE_SHF_CP_SECTION)
  81     OS << 'c';
  82   if (Flags & MCSectionELF::XCORE_SHF_DP_SECTION)
  83     OS << 'd';
  84
  85   OS << '"';
  86
  87   if (ShouldPrintSectionType(Type)) {
  88     OS << ',';
  89
  90     // If comment string is '@', e.g. as on ARM - use '%' instead
  91     if (MAI.getCommentString()[0] == '@')
  92       OS << '%';
  93     else
  94       OS << '@';
  95
  96     if (Type == MCSectionELF::SHT_INIT_ARRAY)
  97       OS << "init_array";
  98     else if (Type == MCSectionELF::SHT_FINI_ARRAY)
  99       OS << "fini_array";
 100     else if (Type == MCSectionELF::SHT_PREINIT_ARRAY)
 101       OS << "preinit_array";
 102     else if (Type == MCSectionELF::SHT_NOBITS)
 103       OS << "nobits";
 104     else if (Type == MCSectionELF::SHT_PROGBITS)
 105       OS << "progbits";
 106
 107     if (EntrySize) {
 108       OS << "," << EntrySize;
 109     }
 110   }
 111
 112   OS << '\n';
 113 }
 114
 115 bool MCSectionELF::UseCodeAlign() const {
 116   return getFlags() & MCSectionELF::SHF_EXECINSTR;
 117 }
 118
 119 // HasCommonSymbols - True if this section holds common symbols, this is
 120 // indicated on the ELF object file by a symbol with SHN_COMMON section
 121 // header index.
 122 bool MCSectionELF::HasCommonSymbols() const {
 123
 124   if (StringRef(SectionName).startswith(".gnu.linkonce."))
 125     return true;
 126
 127   return false;
 128 }
 129
 130 unsigned MCSectionELF::DetermineEntrySize(SectionKind Kind) {
 131   if (Kind.isMergeable1ByteCString()) return 1;
 132   if (Kind.isMergeable2ByteCString()) return 2;
 133   if (Kind.isMergeable4ByteCString()) return 4;
 134   if (Kind.isMergeableConst4())       return 4;
 135   if (Kind.isMergeableConst8())       return 8;
 136   if (Kind.isMergeableConst16())      return 16;
 137   return 0;
 138 }