LLVM  6.0.0svn
MCFixup.h
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1 //===-- llvm/MC/MCFixup.h - Instruction Relocation and Patching -*- C++ -*-===//
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 #ifndef LLVM_MC_MCFIXUP_H
11 #define LLVM_MC_MCFIXUP_H
12 
13 #include "llvm/MC/MCExpr.h"
14 #include "llvm/Support/DataTypes.h"
16 #include "llvm/Support/SMLoc.h"
17 #include <cassert>
18 
19 namespace llvm {
20 class MCExpr;
21 
22 /// \brief Extensible enumeration to represent the type of a fixup.
24  FK_Data_1 = 0, ///< A one-byte fixup.
25  FK_Data_2, ///< A two-byte fixup.
26  FK_Data_4, ///< A four-byte fixup.
27  FK_Data_8, ///< A eight-byte fixup.
28  FK_PCRel_1, ///< A one-byte pc relative fixup.
29  FK_PCRel_2, ///< A two-byte pc relative fixup.
30  FK_PCRel_4, ///< A four-byte pc relative fixup.
31  FK_PCRel_8, ///< A eight-byte pc relative fixup.
32  FK_GPRel_1, ///< A one-byte gp relative fixup.
33  FK_GPRel_2, ///< A two-byte gp relative fixup.
34  FK_GPRel_4, ///< A four-byte gp relative fixup.
35  FK_GPRel_8, ///< A eight-byte gp relative fixup.
36  FK_DTPRel_4, ///< A four-byte dtp relative fixup.
37  FK_DTPRel_8, ///< A eight-byte dtp relative fixup.
38  FK_TPRel_4, ///< A four-byte tp relative fixup.
39  FK_TPRel_8, ///< A eight-byte tp relative fixup.
40  FK_SecRel_1, ///< A one-byte section relative fixup.
41  FK_SecRel_2, ///< A two-byte section relative fixup.
42  FK_SecRel_4, ///< A four-byte section relative fixup.
43  FK_SecRel_8, ///< A eight-byte section relative fixup.
44 
46 
47  // Limit range of target fixups, in case we want to pack more efficiently
48  // later.
49  MaxTargetFixupKind = (1 << 8)
50 };
51 
52 /// \brief Encode information on a single operation to perform on a byte
53 /// sequence (e.g., an encoded instruction) which requires assemble- or run-
54 /// time patching.
55 ///
56 /// Fixups are used any time the target instruction encoder needs to represent
57 /// some value in an instruction which is not yet concrete. The encoder will
58 /// encode the instruction assuming the value is 0, and emit a fixup which
59 /// communicates to the assembler backend how it should rewrite the encoded
60 /// value.
61 ///
62 /// During the process of relaxation, the assembler will apply fixups as
63 /// symbolic values become concrete. When relaxation is complete, any remaining
64 /// fixups become relocations in the object file (or errors, if the fixup cannot
65 /// be encoded on the target).
66 class MCFixup {
67  /// The value to put into the fixup location. The exact interpretation of the
68  /// expression is target dependent, usually it will be one of the operands to
69  /// an instruction or an assembler directive.
70  const MCExpr *Value;
71 
72  /// The byte index of start of the relocation inside the MCFragment.
73  uint32_t Offset;
74 
75  /// The target dependent kind of fixup item this is. The kind is used to
76  /// determine how the operand value should be encoded into the instruction.
77  unsigned Kind;
78 
79  /// The source location which gave rise to the fixup, if any.
80  SMLoc Loc;
81 public:
82  static MCFixup create(uint32_t Offset, const MCExpr *Value,
83  MCFixupKind Kind, SMLoc Loc = SMLoc()) {
84  assert(unsigned(Kind) < MaxTargetFixupKind && "Kind out of range!");
85  MCFixup FI;
86  FI.Value = Value;
87  FI.Offset = Offset;
88  FI.Kind = unsigned(Kind);
89  FI.Loc = Loc;
90  return FI;
91  }
92 
93  MCFixupKind getKind() const { return MCFixupKind(Kind); }
94 
95  uint32_t getOffset() const { return Offset; }
96  void setOffset(uint32_t Value) { Offset = Value; }
97 
98  const MCExpr *getValue() const { return Value; }
99 
100  /// \brief Return the generic fixup kind for a value with the given size. It
101  /// is an error to pass an unsupported size.
102  static MCFixupKind getKindForSize(unsigned Size, bool isPCRel) {
103  switch (Size) {
104  default: llvm_unreachable("Invalid generic fixup size!");
105  case 1: return isPCRel ? FK_PCRel_1 : FK_Data_1;
106  case 2: return isPCRel ? FK_PCRel_2 : FK_Data_2;
107  case 4: return isPCRel ? FK_PCRel_4 : FK_Data_4;
108  case 8: return isPCRel ? FK_PCRel_8 : FK_Data_8;
109  }
110  }
111 
112  SMLoc getLoc() const { return Loc; }
113 };
114 
115 } // End llvm namespace
116 
117 #endif
A eight-byte pc relative fixup.
Definition: MCFixup.h:31
A eight-byte dtp relative fixup.
Definition: MCFixup.h:37
Compute iterated dominance frontiers using a linear time algorithm.
Definition: AllocatorList.h:24
static MCFixupKind getKindForSize(unsigned Size, bool isPCRel)
Return the generic fixup kind for a value with the given size.
Definition: MCFixup.h:102
Encode information on a single operation to perform on a byte sequence (e.g., an encoded instruction)...
Definition: MCFixup.h:66
A one-byte pc relative fixup.
Definition: MCFixup.h:28
A four-byte tp relative fixup.
Definition: MCFixup.h:38
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:36
A four-byte section relative fixup.
Definition: MCFixup.h:42
A four-byte fixup.
Definition: MCFixup.h:26
A four-byte gp relative fixup.
Definition: MCFixup.h:34
A two-byte section relative fixup.
Definition: MCFixup.h:41
A four-byte dtp relative fixup.
Definition: MCFixup.h:36
void setOffset(uint32_t Value)
Definition: MCFixup.h:96
MCFixupKind
Extensible enumeration to represent the type of a fixup.
Definition: MCFixup.h:23
uint32_t getOffset() const
Definition: MCFixup.h:95
A eight-byte tp relative fixup.
Definition: MCFixup.h:39
static MCFixup create(uint32_t Offset, const MCExpr *Value, MCFixupKind Kind, SMLoc Loc=SMLoc())
Definition: MCFixup.h:82
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
A one-byte fixup.
Definition: MCFixup.h:24
SMLoc getLoc() const
Definition: MCFixup.h:112
A two-byte pc relative fixup.
Definition: MCFixup.h:29
A four-byte pc relative fixup.
Definition: MCFixup.h:30
A two-byte gp relative fixup.
Definition: MCFixup.h:33
A one-byte section relative fixup.
Definition: MCFixup.h:40
A eight-byte gp relative fixup.
Definition: MCFixup.h:35
A eight-byte section relative fixup.
Definition: MCFixup.h:43
A eight-byte fixup.
Definition: MCFixup.h:27
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
A one-byte gp relative fixup.
Definition: MCFixup.h:32
LLVM Value Representation.
Definition: Value.h:73
constexpr char Size[]
Key for Kernel::Arg::Metadata::mSize.
const MCExpr * getValue() const
Definition: MCFixup.h:98
static bool isPCRel(unsigned Kind)
Represents a location in source code.
Definition: SMLoc.h:24
A two-byte fixup.
Definition: MCFixup.h:25
MCFixupKind getKind() const
Definition: MCFixup.h:93