lib/MC/MCObjectWriter.cpp

   1 //===- lib/MC/MCObjectWriter.cpp - MCObjectWriter implementation ----------===//
   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/MCAssembler.h"
  11 #include "llvm/MC/MCExpr.h"
  12 #include "llvm/MC/MCObjectWriter.h"
  13 #include "llvm/MC/MCSymbol.h"
  14
  15 using namespace llvm;
  16
  17 MCObjectWriter::~MCObjectWriter() {
  18 }
  19
  20 /// Utility function to encode a SLEB128 value.
  21 void MCObjectWriter::EncodeSLEB128(int64_t Value, raw_ostream &OS) {
  22   bool More;
  23   do {
  24     uint8_t Byte = Value & 0x7f;
  25     // NOTE: this assumes that this signed shift is an arithmetic right shift.
  26     Value >>= 7;
  27     More = !((((Value == 0 ) && ((Byte & 0x40) == 0)) ||
  28               ((Value == -1) && ((Byte & 0x40) != 0))));
  29     if (More)
  30       Byte |= 0x80; // Mark this byte that that more bytes will follow.
  31     OS << char(Byte);
  32   } while (More);
  33 }
  34
  35 /// Utility function to encode a ULEB128 value.
  36 void MCObjectWriter::EncodeULEB128(uint64_t Value, raw_ostream &OS) {
  37   do {
  38     uint8_t Byte = Value & 0x7f;
  39     Value >>= 7;
  40     if (Value != 0)
  41       Byte |= 0x80; // Mark this byte that that more bytes will follow.
  42     OS << char(Byte);
  43   } while (Value != 0);
  44 }
  45
  46 bool
  47 MCObjectWriter::IsSymbolRefDifferenceFullyResolved(const MCAssembler &Asm,
  48                                                    const MCSymbolRefExpr *A,
  49                                                    const MCSymbolRefExpr *B,
  50                                                    bool InSet) const {
  51   // Modified symbol references cannot be resolved.
  52   if (A->getKind() != MCSymbolRefExpr::VK_None ||
  53       B->getKind() != MCSymbolRefExpr::VK_None)
  54     return false;
  55
  56   const MCSymbol &SA = A->getSymbol();
  57   const MCSymbol &SB = B->getSymbol();
  58   if (SA.AliasedSymbol().isUndefined() || SB.AliasedSymbol().isUndefined())
  59     return false;
  60
  61   const MCSymbolData &DataA = Asm.getSymbolData(SA);
  62   const MCSymbolData &DataB = Asm.getSymbolData(SB);
  63
  64   return IsSymbolRefDifferenceFullyResolvedImpl(Asm, DataA,
  65                                                 *DataB.getFragment(),
  66                                                 InSet,
  67                                                 false);
  68 }
  69
  70 bool
  71 MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
  72                                                       const MCSymbolData &DataA,
  73                                                       const MCFragment &FB,
  74                                                       bool InSet,
  75                                                       bool IsPCRel) const {
  76   const MCSection &SecA = DataA.getSymbol().AliasedSymbol().getSection();
  77   const MCSection &SecB = FB.getParent()->getSection();
  78   // On ELF and COFF  A - B is absolute if A and B are in the same section.
  79   return &SecA == &SecB;
  80 }