1 //===-- llvm/MC/MCFixup.h - Instruction Relocation and Patching -*- C++ -*-===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
10 #ifndef LLVM_MC_MCFIXUP_H
11 #define LLVM_MC_MCFIXUP_H
13 #include "llvm/MC/MCExpr.h"
14 #include "llvm/Support/DataTypes.h"
15 #include "llvm/Support/ErrorHandling.h"
16 #include "llvm/Support/SMLoc.h"
22 /// MCFixupKind - 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_SecRel_1, ///< A one-byte section relative fixup.
37 FK_SecRel_2, ///< A two-byte section relative fixup.
38 FK_SecRel_4, ///< A four-byte section relative fixup.
39 FK_SecRel_8, ///< A eight-byte section relative fixup.
41 FirstTargetFixupKind = 128,
43 // Limit range of target fixups, in case we want to pack more efficiently
45 MaxTargetFixupKind = (1 << 8)
48 /// MCFixup - Encode information on a single operation to perform on a byte
49 /// sequence (e.g., an encoded instruction) which requires assemble- or run-
52 /// Fixups are used any time the target instruction encoder needs to represent
53 /// some value in an instruction which is not yet concrete. The encoder will
54 /// encode the instruction assuming the value is 0, and emit a fixup which
55 /// communicates to the assembler backend how it should rewrite the encoded
58 /// During the process of relaxation, the assembler will apply fixups as
59 /// symbolic values become concrete. When relaxation is complete, any remaining
60 /// fixups become relocations in the object file (or errors, if the fixup cannot
61 /// be encoded on the target).
63 /// The value to put into the fixup location. The exact interpretation of the
64 /// expression is target dependent, usually it will be one of the operands to
65 /// an instruction or an assembler directive.
68 /// The byte index of start of the relocation inside the encoded instruction.
71 /// The target dependent kind of fixup item this is. The kind is used to
72 /// determine how the operand value should be encoded into the instruction.
75 /// The source location which gave rise to the fixup, if any.
78 static MCFixup Create(uint32_t Offset, const MCExpr *Value,
79 MCFixupKind Kind, SMLoc Loc = SMLoc()) {
80 assert(unsigned(Kind) < MaxTargetFixupKind && "Kind out of range!");
84 FI.Kind = unsigned(Kind);
89 MCFixupKind getKind() const { return MCFixupKind(Kind); }
91 uint32_t getOffset() const { return Offset; }
92 void setOffset(uint32_t Value) { Offset = Value; }
94 const MCExpr *getValue() const { return Value; }
96 /// getKindForSize - Return the generic fixup kind for a value with the given
97 /// size. It is an error to pass an unsupported size.
98 static MCFixupKind getKindForSize(unsigned Size, bool isPCRel) {
100 default: llvm_unreachable("Invalid generic fixup size!");
101 case 1: return isPCRel ? FK_PCRel_1 : FK_Data_1;
102 case 2: return isPCRel ? FK_PCRel_2 : FK_Data_2;
103 case 4: return isPCRel ? FK_PCRel_4 : FK_Data_4;
104 case 8: return isPCRel ? FK_PCRel_8 : FK_Data_8;
108 SMLoc getLoc() const { return Loc; }
111 } // End llvm namespace