LLVM  9.0.0svn
MCFixup.h
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1 //===-- llvm/MC/MCFixup.h - Instruction Relocation and Patching -*- C++ -*-===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 
9 #ifndef LLVM_MC_MCFIXUP_H
10 #define LLVM_MC_MCFIXUP_H
11 
12 #include "llvm/MC/MCExpr.h"
13 #include "llvm/Support/DataTypes.h"
15 #include "llvm/Support/SMLoc.h"
16 #include <cassert>
17 
18 namespace llvm {
19 class MCExpr;
20 
21 /// Extensible enumeration to represent the type of a fixup.
23  FK_Data_1 = 0, ///< A one-byte fixup.
24  FK_Data_2, ///< A two-byte fixup.
25  FK_Data_4, ///< A four-byte fixup.
26  FK_Data_8, ///< A eight-byte fixup.
27  FK_PCRel_1, ///< A one-byte pc relative fixup.
28  FK_PCRel_2, ///< A two-byte pc relative fixup.
29  FK_PCRel_4, ///< A four-byte pc relative fixup.
30  FK_PCRel_8, ///< A eight-byte pc relative fixup.
31  FK_GPRel_1, ///< A one-byte gp relative fixup.
32  FK_GPRel_2, ///< A two-byte gp relative fixup.
33  FK_GPRel_4, ///< A four-byte gp relative fixup.
34  FK_GPRel_8, ///< A eight-byte gp relative fixup.
35  FK_DTPRel_4, ///< A four-byte dtp relative fixup.
36  FK_DTPRel_8, ///< A eight-byte dtp relative fixup.
37  FK_TPRel_4, ///< A four-byte tp relative fixup.
38  FK_TPRel_8, ///< A eight-byte tp relative fixup.
39  FK_SecRel_1, ///< A one-byte section relative fixup.
40  FK_SecRel_2, ///< A two-byte section relative fixup.
41  FK_SecRel_4, ///< A four-byte section relative fixup.
42  FK_SecRel_8, ///< A eight-byte section relative fixup.
43  FK_Data_Add_1, ///< A one-byte add fixup.
44  FK_Data_Add_2, ///< A two-byte add fixup.
45  FK_Data_Add_4, ///< A four-byte add fixup.
46  FK_Data_Add_8, ///< A eight-byte add fixup.
47  FK_Data_Sub_1, ///< A one-byte sub fixup.
48  FK_Data_Sub_2, ///< A two-byte sub fixup.
49  FK_Data_Sub_4, ///< A four-byte sub fixup.
50  FK_Data_Sub_8, ///< A eight-byte sub fixup.
51 
53 
54  // Limit range of target fixups, in case we want to pack more efficiently
55  // later.
56  MaxTargetFixupKind = (1 << 8)
57 };
58 
59 /// Encode information on a single operation to perform on a byte
60 /// sequence (e.g., an encoded instruction) which requires assemble- or run-
61 /// time patching.
62 ///
63 /// Fixups are used any time the target instruction encoder needs to represent
64 /// some value in an instruction which is not yet concrete. The encoder will
65 /// encode the instruction assuming the value is 0, and emit a fixup which
66 /// communicates to the assembler backend how it should rewrite the encoded
67 /// value.
68 ///
69 /// During the process of relaxation, the assembler will apply fixups as
70 /// symbolic values become concrete. When relaxation is complete, any remaining
71 /// fixups become relocations in the object file (or errors, if the fixup cannot
72 /// be encoded on the target).
73 class MCFixup {
74  /// The value to put into the fixup location. The exact interpretation of the
75  /// expression is target dependent, usually it will be one of the operands to
76  /// an instruction or an assembler directive.
77  const MCExpr *Value;
78 
79  /// The byte index of start of the relocation inside the MCFragment.
80  uint32_t Offset;
81 
82  /// The target dependent kind of fixup item this is. The kind is used to
83  /// determine how the operand value should be encoded into the instruction.
84  unsigned Kind;
85 
86  /// The source location which gave rise to the fixup, if any.
87  SMLoc Loc;
88 public:
89  static MCFixup create(uint32_t Offset, const MCExpr *Value,
90  MCFixupKind Kind, SMLoc Loc = SMLoc()) {
91  assert(unsigned(Kind) < MaxTargetFixupKind && "Kind out of range!");
92  MCFixup FI;
93  FI.Value = Value;
94  FI.Offset = Offset;
95  FI.Kind = unsigned(Kind);
96  FI.Loc = Loc;
97  return FI;
98  }
99 
100  /// Return a fixup corresponding to the add half of a add/sub fixup pair for
101  /// the given Fixup.
102  static MCFixup createAddFor(const MCFixup &Fixup) {
103  MCFixup FI;
104  FI.Value = Fixup.getValue();
105  FI.Offset = Fixup.getOffset();
106  FI.Kind = (unsigned)getAddKindForKind(Fixup.getKind());
107  FI.Loc = Fixup.getLoc();
108  return FI;
109  }
110 
111  /// Return a fixup corresponding to the sub half of a add/sub fixup pair for
112  /// the given Fixup.
113  static MCFixup createSubFor(const MCFixup &Fixup) {
114  MCFixup FI;
115  FI.Value = Fixup.getValue();
116  FI.Offset = Fixup.getOffset();
117  FI.Kind = (unsigned)getSubKindForKind(Fixup.getKind());
118  FI.Loc = Fixup.getLoc();
119  return FI;
120  }
121 
122  MCFixupKind getKind() const { return MCFixupKind(Kind); }
123 
124  uint32_t getOffset() const { return Offset; }
125  void setOffset(uint32_t Value) { Offset = Value; }
126 
127  const MCExpr *getValue() const { return Value; }
128 
129  /// Return the generic fixup kind for a value with the given size. It
130  /// is an error to pass an unsupported size.
131  static MCFixupKind getKindForSize(unsigned Size, bool isPCRel) {
132  switch (Size) {
133  default: llvm_unreachable("Invalid generic fixup size!");
134  case 1: return isPCRel ? FK_PCRel_1 : FK_Data_1;
135  case 2: return isPCRel ? FK_PCRel_2 : FK_Data_2;
136  case 4: return isPCRel ? FK_PCRel_4 : FK_Data_4;
137  case 8: return isPCRel ? FK_PCRel_8 : FK_Data_8;
138  }
139  }
140 
141  /// Return the generic fixup kind for an addition with a given size. It
142  /// is an error to pass an unsupported size.
143  static MCFixupKind getAddKindForKind(unsigned Kind) {
144  switch (Kind) {
145  default: llvm_unreachable("Unknown type to convert!");
146  case FK_Data_1: return FK_Data_Add_1;
147  case FK_Data_2: return FK_Data_Add_2;
148  case FK_Data_4: return FK_Data_Add_4;
149  case FK_Data_8: return FK_Data_Add_8;
150  }
151  }
152 
153  /// Return the generic fixup kind for an subtraction with a given size. It
154  /// is an error to pass an unsupported size.
155  static MCFixupKind getSubKindForKind(unsigned Kind) {
156  switch (Kind) {
157  default: llvm_unreachable("Unknown type to convert!");
158  case FK_Data_1: return FK_Data_Sub_1;
159  case FK_Data_2: return FK_Data_Sub_2;
160  case FK_Data_4: return FK_Data_Sub_4;
161  case FK_Data_8: return FK_Data_Sub_8;
162  }
163  }
164 
165  SMLoc getLoc() const { return Loc; }
166 };
167 
168 } // End llvm namespace
169 
170 #endif
A eight-byte pc relative fixup.
Definition: MCFixup.h:30
A eight-byte dtp relative fixup.
Definition: MCFixup.h:36
This class represents lattice values for constants.
Definition: AllocatorList.h:23
A eight-byte sub fixup.
Definition: MCFixup.h:50
static MCFixupKind getKindForSize(unsigned Size, bool isPCRel)
Return the generic fixup kind for a value with the given size.
Definition: MCFixup.h:131
Encode information on a single operation to perform on a byte sequence (e.g., an encoded instruction)...
Definition: MCFixup.h:73
A one-byte pc relative fixup.
Definition: MCFixup.h:27
A eight-byte add fixup.
Definition: MCFixup.h:46
A four-byte tp relative fixup.
Definition: MCFixup.h:37
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:35
static MCFixup createSubFor(const MCFixup &Fixup)
Return a fixup corresponding to the sub half of a add/sub fixup pair for the given Fixup...
Definition: MCFixup.h:113
A four-byte section relative fixup.
Definition: MCFixup.h:41
A four-byte fixup.
Definition: MCFixup.h:25
A four-byte gp relative fixup.
Definition: MCFixup.h:33
A two-byte section relative fixup.
Definition: MCFixup.h:40
A one-byte add fixup.
Definition: MCFixup.h:43
A four-byte dtp relative fixup.
Definition: MCFixup.h:35
void setOffset(uint32_t Value)
Definition: MCFixup.h:125
MCFixupKind
Extensible enumeration to represent the type of a fixup.
Definition: MCFixup.h:22
uint32_t getOffset() const
Definition: MCFixup.h:124
A eight-byte tp relative fixup.
Definition: MCFixup.h:38
static MCFixup create(uint32_t Offset, const MCExpr *Value, MCFixupKind Kind, SMLoc Loc=SMLoc())
Definition: MCFixup.h:89
#define llvm_unreachable(msg)
Marks that the current location is not supposed to be reachable.
A one-byte fixup.
Definition: MCFixup.h:23
SMLoc getLoc() const
Definition: MCFixup.h:165
A two-byte pc relative fixup.
Definition: MCFixup.h:28
A four-byte pc relative fixup.
Definition: MCFixup.h:29
A two-byte gp relative fixup.
Definition: MCFixup.h:32
A four-byte add fixup.
Definition: MCFixup.h:45
A one-byte section relative fixup.
Definition: MCFixup.h:39
A eight-byte gp relative fixup.
Definition: MCFixup.h:34
A two-byte sub fixup.
Definition: MCFixup.h:48
A eight-byte section relative fixup.
Definition: MCFixup.h:42
static MCFixup createAddFor(const MCFixup &Fixup)
Return a fixup corresponding to the add half of a add/sub fixup pair for the given Fixup...
Definition: MCFixup.h:102
A eight-byte fixup.
Definition: MCFixup.h:26
uint32_t Size
Definition: Profile.cpp:46
A one-byte sub fixup.
Definition: MCFixup.h:47
A four-byte sub fixup.
Definition: MCFixup.h:49
assert(ImpDefSCC.getReg()==AMDGPU::SCC &&ImpDefSCC.isDef())
A one-byte gp relative fixup.
Definition: MCFixup.h:31
LLVM Value Representation.
Definition: Value.h:72
A two-byte add fixup.
Definition: MCFixup.h:44
const MCExpr * getValue() const
Definition: MCFixup.h:127
static bool isPCRel(unsigned Kind)
Represents a location in source code.
Definition: SMLoc.h:23
A two-byte fixup.
Definition: MCFixup.h:24
static MCFixupKind getSubKindForKind(unsigned Kind)
Return the generic fixup kind for an subtraction with a given size.
Definition: MCFixup.h:155
MCFixupKind getKind() const
Definition: MCFixup.h:122
static MCFixupKind getAddKindForKind(unsigned Kind)
Return the generic fixup kind for an addition with a given size.
Definition: MCFixup.h:143