1 //===-- llvm/MC/MCFixup.h - Instruction Relocation and Patching -*- C++ -*-===//
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
7 //===----------------------------------------------------------------------===//
9 #ifndef LLVM_MC_MCFIXUP_H
10 #define LLVM_MC_MCFIXUP_H
12 #include "llvm/MC/MCExpr.h"
13 #include "llvm/Support/DataTypes.h"
14 #include "llvm/Support/ErrorHandling.h"
15 #include "llvm/Support/SMLoc.h"
21 /// Extensible enumeration to represent the type of a fixup.
23 FK_NONE = 0, ///< A no-op fixup.
24 FK_Data_1, ///< 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_Data_6b, ///< A six-bits fixup.
29 FK_PCRel_1, ///< A one-byte pc relative fixup.
30 FK_PCRel_2, ///< A two-byte pc relative fixup.
31 FK_PCRel_4, ///< A four-byte pc relative fixup.
32 FK_PCRel_8, ///< A eight-byte pc relative fixup.
33 FK_GPRel_1, ///< A one-byte gp relative fixup.
34 FK_GPRel_2, ///< A two-byte gp relative fixup.
35 FK_GPRel_4, ///< A four-byte gp relative fixup.
36 FK_GPRel_8, ///< A eight-byte gp relative fixup.
37 FK_DTPRel_4, ///< A four-byte dtp relative fixup.
38 FK_DTPRel_8, ///< A eight-byte dtp relative fixup.
39 FK_TPRel_4, ///< A four-byte tp relative fixup.
40 FK_TPRel_8, ///< A eight-byte tp relative fixup.
41 FK_SecRel_1, ///< A one-byte section relative fixup.
42 FK_SecRel_2, ///< A two-byte section relative fixup.
43 FK_SecRel_4, ///< A four-byte section relative fixup.
44 FK_SecRel_8, ///< A eight-byte section relative fixup.
45 FK_Data_Add_1, ///< A one-byte add fixup.
46 FK_Data_Add_2, ///< A two-byte add fixup.
47 FK_Data_Add_4, ///< A four-byte add fixup.
48 FK_Data_Add_8, ///< A eight-byte add fixup.
49 FK_Data_Add_6b, ///< A six-bits add fixup.
50 FK_Data_Sub_1, ///< A one-byte sub fixup.
51 FK_Data_Sub_2, ///< A two-byte sub fixup.
52 FK_Data_Sub_4, ///< A four-byte sub fixup.
53 FK_Data_Sub_8, ///< A eight-byte sub fixup.
54 FK_Data_Sub_6b, ///< A six-bits sub fixup.
56 FirstTargetFixupKind = 128,
58 // Limit range of target fixups, in case we want to pack more efficiently
60 MaxTargetFixupKind = (1 << 8)
63 /// Encode information on a single operation to perform on a byte
64 /// sequence (e.g., an encoded instruction) which requires assemble- or run-
67 /// Fixups are used any time the target instruction encoder needs to represent
68 /// some value in an instruction which is not yet concrete. The encoder will
69 /// encode the instruction assuming the value is 0, and emit a fixup which
70 /// communicates to the assembler backend how it should rewrite the encoded
73 /// During the process of relaxation, the assembler will apply fixups as
74 /// symbolic values become concrete. When relaxation is complete, any remaining
75 /// fixups become relocations in the object file (or errors, if the fixup cannot
76 /// be encoded on the target).
78 /// The value to put into the fixup location. The exact interpretation of the
79 /// expression is target dependent, usually it will be one of the operands to
80 /// an instruction or an assembler directive.
81 const MCExpr *Value = nullptr;
83 /// The byte index of start of the relocation inside the MCFragment.
86 /// The target dependent kind of fixup item this is. The kind is used to
87 /// determine how the operand value should be encoded into the instruction.
88 MCFixupKind Kind = FK_NONE;
90 /// The source location which gave rise to the fixup, if any.
93 static MCFixup create(uint32_t Offset, const MCExpr *Value,
94 MCFixupKind Kind, SMLoc Loc = SMLoc()) {
95 assert(Kind < MaxTargetFixupKind && "Kind out of range!");
104 /// Return a fixup corresponding to the add half of a add/sub fixup pair for
106 static MCFixup createAddFor(const MCFixup &Fixup) {
108 FI.Value = Fixup.getValue();
109 FI.Offset = Fixup.getOffset();
110 FI.Kind = getAddKindForKind(Fixup.getKind());
111 FI.Loc = Fixup.getLoc();
115 /// Return a fixup corresponding to the sub half of a add/sub fixup pair for
117 static MCFixup createSubFor(const MCFixup &Fixup) {
119 FI.Value = Fixup.getValue();
120 FI.Offset = Fixup.getOffset();
121 FI.Kind = getSubKindForKind(Fixup.getKind());
122 FI.Loc = Fixup.getLoc();
126 MCFixupKind getKind() const { return Kind; }
128 unsigned getTargetKind() const { return Kind; }
130 uint32_t getOffset() const { return Offset; }
131 void setOffset(uint32_t Value) { Offset = Value; }
133 const MCExpr *getValue() const { return Value; }
135 /// Return the generic fixup kind for a value with the given size. It
136 /// is an error to pass an unsupported size.
137 static MCFixupKind getKindForSize(unsigned Size, bool IsPCRel) {
139 default: llvm_unreachable("Invalid generic fixup size!");
141 return IsPCRel ? FK_PCRel_1 : FK_Data_1;
143 return IsPCRel ? FK_PCRel_2 : FK_Data_2;
145 return IsPCRel ? FK_PCRel_4 : FK_Data_4;
147 return IsPCRel ? FK_PCRel_8 : FK_Data_8;
151 /// Return the generic fixup kind for a value with the given size in bits.
152 /// It is an error to pass an unsupported size.
153 static MCFixupKind getKindForSizeInBits(unsigned Size, bool IsPCRel) {
156 llvm_unreachable("Invalid generic fixup size!");
158 assert(!IsPCRel && "Invalid pc-relative fixup size!");
161 return IsPCRel ? FK_PCRel_1 : FK_Data_1;
163 return IsPCRel ? FK_PCRel_2 : FK_Data_2;
165 return IsPCRel ? FK_PCRel_4 : FK_Data_4;
167 return IsPCRel ? FK_PCRel_8 : FK_Data_8;
171 /// Return the generic fixup kind for an addition with a given size. It
172 /// is an error to pass an unsupported size.
173 static MCFixupKind getAddKindForKind(MCFixupKind Kind) {
175 default: llvm_unreachable("Unknown type to convert!");
176 case FK_Data_1: return FK_Data_Add_1;
177 case FK_Data_2: return FK_Data_Add_2;
178 case FK_Data_4: return FK_Data_Add_4;
179 case FK_Data_8: return FK_Data_Add_8;
180 case FK_Data_6b: return FK_Data_Add_6b;
184 /// Return the generic fixup kind for an subtraction with a given size. It
185 /// is an error to pass an unsupported size.
186 static MCFixupKind getSubKindForKind(MCFixupKind Kind) {
188 default: llvm_unreachable("Unknown type to convert!");
189 case FK_Data_1: return FK_Data_Sub_1;
190 case FK_Data_2: return FK_Data_Sub_2;
191 case FK_Data_4: return FK_Data_Sub_4;
192 case FK_Data_8: return FK_Data_Sub_8;
193 case FK_Data_6b: return FK_Data_Sub_6b;
197 SMLoc getLoc() const { return Loc; }
200 } // End llvm namespace