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)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
IsSymbolRefDifferenceFullyResolved(const MCAssembler & Asm,const MCSymbolRefExpr * A,const MCSymbolRefExpr * B,bool InSet) const47 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
IsSymbolRefDifferenceFullyResolvedImpl(const MCAssembler & Asm,const MCSymbolData & DataA,const MCFragment & FB,bool InSet,bool IsPCRel) const71 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 }
81