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
~MCObjectWriter()17 MCObjectWriter::~MCObjectWriter() {
18 }
19
20 /// Utility function to encode a SLEB128 value.
EncodeSLEB128(int64_t Value,raw_ostream & OS)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.
EncodeULEB128(uint64_t Value,raw_ostream & OS,unsigned Padding)36 void MCObjectWriter::EncodeULEB128(uint64_t Value, raw_ostream &OS,
37 unsigned Padding) {
38 do {
39 uint8_t Byte = Value & 0x7f;
40 Value >>= 7;
41 if (Value != 0 || Padding != 0)
42 Byte |= 0x80; // Mark this byte that that more bytes will follow.
43 OS << char(Byte);
44 } while (Value != 0);
45
46 // Pad with 0x80 and emit a null byte at the end.
47 if (Padding != 0) {
48 for (; Padding != 1; --Padding)
49 OS << '\x80';
50 OS << '\x00';
51 }
52 }
53
54 bool
IsSymbolRefDifferenceFullyResolved(const MCAssembler & Asm,const MCSymbolRefExpr * A,const MCSymbolRefExpr * B,bool InSet) const55 MCObjectWriter::IsSymbolRefDifferenceFullyResolved(const MCAssembler &Asm,
56 const MCSymbolRefExpr *A,
57 const MCSymbolRefExpr *B,
58 bool InSet) const {
59 // Modified symbol references cannot be resolved.
60 if (A->getKind() != MCSymbolRefExpr::VK_None ||
61 B->getKind() != MCSymbolRefExpr::VK_None)
62 return false;
63
64 const MCSymbol &SA = A->getSymbol();
65 const MCSymbol &SB = B->getSymbol();
66 if (SA.AliasedSymbol().isUndefined() || SB.AliasedSymbol().isUndefined())
67 return false;
68
69 const MCSymbolData &DataA = Asm.getSymbolData(SA);
70 const MCSymbolData &DataB = Asm.getSymbolData(SB);
71 if(!DataA.getFragment() || !DataB.getFragment())
72 return false;
73
74 return IsSymbolRefDifferenceFullyResolvedImpl(Asm, DataA,
75 *DataB.getFragment(),
76 InSet,
77 false);
78 }
79
80 bool
IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler & Asm,const MCSymbolData & DataA,const MCFragment & FB,bool InSet,bool IsPCRel) const81 MCObjectWriter::IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler &Asm,
82 const MCSymbolData &DataA,
83 const MCFragment &FB,
84 bool InSet,
85 bool IsPCRel) const {
86 const MCSection &SecA = DataA.getSymbol().AliasedSymbol().getSection();
87 const MCSection &SecB = FB.getParent()->getSection();
88 // On ELF and COFF A - B is absolute if A and B are in the same section.
89 return &SecA == &SecB;
90 }
91