| //===-- llvm/MC/MCFixup.h - Instruction Relocation and Patching -*- C++ -*-===// |
| // |
| // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions. |
| // See https://llvm.org/LICENSE.txt for license information. |
| // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception |
| // |
| //===----------------------------------------------------------------------===// |
| |
| #ifndef LLVM_MC_MCFIXUP_H |
| #define LLVM_MC_MCFIXUP_H |
| |
| #include "llvm/MC/MCExpr.h" |
| #include "llvm/Support/DataTypes.h" |
| #include "llvm/Support/ErrorHandling.h" |
| #include "llvm/Support/SMLoc.h" |
| #include <cassert> |
| |
| namespace llvm { |
| class MCExpr; |
| |
| /// Extensible enumeration to represent the type of a fixup. |
| enum MCFixupKind { |
| FK_NONE = 0, ///< A no-op fixup. |
| FK_Data_1, ///< A one-byte fixup. |
| FK_Data_2, ///< A two-byte fixup. |
| FK_Data_4, ///< A four-byte fixup. |
| FK_Data_8, ///< A eight-byte fixup. |
| FK_Data_6b, ///< A six-bits fixup. |
| FK_PCRel_1, ///< A one-byte pc relative fixup. |
| FK_PCRel_2, ///< A two-byte pc relative fixup. |
| FK_PCRel_4, ///< A four-byte pc relative fixup. |
| FK_PCRel_8, ///< A eight-byte pc relative fixup. |
| FK_GPRel_1, ///< A one-byte gp relative fixup. |
| FK_GPRel_2, ///< A two-byte gp relative fixup. |
| FK_GPRel_4, ///< A four-byte gp relative fixup. |
| FK_GPRel_8, ///< A eight-byte gp relative fixup. |
| FK_DTPRel_4, ///< A four-byte dtp relative fixup. |
| FK_DTPRel_8, ///< A eight-byte dtp relative fixup. |
| FK_TPRel_4, ///< A four-byte tp relative fixup. |
| FK_TPRel_8, ///< A eight-byte tp relative fixup. |
| FK_SecRel_1, ///< A one-byte section relative fixup. |
| FK_SecRel_2, ///< A two-byte section relative fixup. |
| FK_SecRel_4, ///< A four-byte section relative fixup. |
| FK_SecRel_8, ///< A eight-byte section relative fixup. |
| FK_Data_Add_1, ///< A one-byte add fixup. |
| FK_Data_Add_2, ///< A two-byte add fixup. |
| FK_Data_Add_4, ///< A four-byte add fixup. |
| FK_Data_Add_8, ///< A eight-byte add fixup. |
| FK_Data_Add_6b, ///< A six-bits add fixup. |
| FK_Data_Sub_1, ///< A one-byte sub fixup. |
| FK_Data_Sub_2, ///< A two-byte sub fixup. |
| FK_Data_Sub_4, ///< A four-byte sub fixup. |
| FK_Data_Sub_8, ///< A eight-byte sub fixup. |
| FK_Data_Sub_6b, ///< A six-bits sub fixup. |
| |
| FirstTargetFixupKind = 128, |
| |
| // Limit range of target fixups, in case we want to pack more efficiently |
| // later. |
| MaxTargetFixupKind = (1 << 8) |
| }; |
| |
| /// Encode information on a single operation to perform on a byte |
| /// sequence (e.g., an encoded instruction) which requires assemble- or run- |
| /// time patching. |
| /// |
| /// Fixups are used any time the target instruction encoder needs to represent |
| /// some value in an instruction which is not yet concrete. The encoder will |
| /// encode the instruction assuming the value is 0, and emit a fixup which |
| /// communicates to the assembler backend how it should rewrite the encoded |
| /// value. |
| /// |
| /// During the process of relaxation, the assembler will apply fixups as |
| /// symbolic values become concrete. When relaxation is complete, any remaining |
| /// fixups become relocations in the object file (or errors, if the fixup cannot |
| /// be encoded on the target). |
| class MCFixup { |
| /// The value to put into the fixup location. The exact interpretation of the |
| /// expression is target dependent, usually it will be one of the operands to |
| /// an instruction or an assembler directive. |
| const MCExpr *Value = nullptr; |
| |
| /// The byte index of start of the relocation inside the MCFragment. |
| uint32_t Offset = 0; |
| |
| /// The target dependent kind of fixup item this is. The kind is used to |
| /// determine how the operand value should be encoded into the instruction. |
| MCFixupKind Kind = FK_NONE; |
| |
| /// The source location which gave rise to the fixup, if any. |
| SMLoc Loc; |
| public: |
| static MCFixup create(uint32_t Offset, const MCExpr *Value, |
| MCFixupKind Kind, SMLoc Loc = SMLoc()) { |
| assert(Kind < MaxTargetFixupKind && "Kind out of range!"); |
| MCFixup FI; |
| FI.Value = Value; |
| FI.Offset = Offset; |
| FI.Kind = Kind; |
| FI.Loc = Loc; |
| return FI; |
| } |
| |
| /// Return a fixup corresponding to the add half of a add/sub fixup pair for |
| /// the given Fixup. |
| static MCFixup createAddFor(const MCFixup &Fixup) { |
| MCFixup FI; |
| FI.Value = Fixup.getValue(); |
| FI.Offset = Fixup.getOffset(); |
| FI.Kind = getAddKindForKind(Fixup.getKind()); |
| FI.Loc = Fixup.getLoc(); |
| return FI; |
| } |
| |
| /// Return a fixup corresponding to the sub half of a add/sub fixup pair for |
| /// the given Fixup. |
| static MCFixup createSubFor(const MCFixup &Fixup) { |
| MCFixup FI; |
| FI.Value = Fixup.getValue(); |
| FI.Offset = Fixup.getOffset(); |
| FI.Kind = getSubKindForKind(Fixup.getKind()); |
| FI.Loc = Fixup.getLoc(); |
| return FI; |
| } |
| |
| MCFixupKind getKind() const { return Kind; } |
| |
| unsigned getTargetKind() const { return Kind; } |
| |
| uint32_t getOffset() const { return Offset; } |
| void setOffset(uint32_t Value) { Offset = Value; } |
| |
| const MCExpr *getValue() const { return Value; } |
| |
| /// Return the generic fixup kind for a value with the given size. It |
| /// is an error to pass an unsupported size. |
| static MCFixupKind getKindForSize(unsigned Size, bool IsPCRel) { |
| switch (Size) { |
| default: llvm_unreachable("Invalid generic fixup size!"); |
| case 1: |
| return IsPCRel ? FK_PCRel_1 : FK_Data_1; |
| case 2: |
| return IsPCRel ? FK_PCRel_2 : FK_Data_2; |
| case 4: |
| return IsPCRel ? FK_PCRel_4 : FK_Data_4; |
| case 8: |
| return IsPCRel ? FK_PCRel_8 : FK_Data_8; |
| } |
| } |
| |
| /// Return the generic fixup kind for a value with the given size in bits. |
| /// It is an error to pass an unsupported size. |
| static MCFixupKind getKindForSizeInBits(unsigned Size, bool IsPCRel) { |
| switch (Size) { |
| default: |
| llvm_unreachable("Invalid generic fixup size!"); |
| case 6: |
| assert(!IsPCRel && "Invalid pc-relative fixup size!"); |
| return FK_Data_6b; |
| case 8: |
| return IsPCRel ? FK_PCRel_1 : FK_Data_1; |
| case 16: |
| return IsPCRel ? FK_PCRel_2 : FK_Data_2; |
| case 32: |
| return IsPCRel ? FK_PCRel_4 : FK_Data_4; |
| case 64: |
| return IsPCRel ? FK_PCRel_8 : FK_Data_8; |
| } |
| } |
| |
| /// Return the generic fixup kind for an addition with a given size. It |
| /// is an error to pass an unsupported size. |
| static MCFixupKind getAddKindForKind(MCFixupKind Kind) { |
| switch (Kind) { |
| default: llvm_unreachable("Unknown type to convert!"); |
| case FK_Data_1: return FK_Data_Add_1; |
| case FK_Data_2: return FK_Data_Add_2; |
| case FK_Data_4: return FK_Data_Add_4; |
| case FK_Data_8: return FK_Data_Add_8; |
| case FK_Data_6b: return FK_Data_Add_6b; |
| } |
| } |
| |
| /// Return the generic fixup kind for an subtraction with a given size. It |
| /// is an error to pass an unsupported size. |
| static MCFixupKind getSubKindForKind(MCFixupKind Kind) { |
| switch (Kind) { |
| default: llvm_unreachable("Unknown type to convert!"); |
| case FK_Data_1: return FK_Data_Sub_1; |
| case FK_Data_2: return FK_Data_Sub_2; |
| case FK_Data_4: return FK_Data_Sub_4; |
| case FK_Data_8: return FK_Data_Sub_8; |
| case FK_Data_6b: return FK_Data_Sub_6b; |
| } |
| } |
| |
| SMLoc getLoc() const { return Loc; } |
| }; |
| |
| } // End llvm namespace |
| |
| #endif |