1 //===- MCAsmBackend.cpp - Target MC Assembly Backend ----------------------===// 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 #include "llvm/MC/MCAsmBackend.h" 10 #include "llvm/MC/MCAssembler.h" 11 #include "llvm/MC/MCDXContainerWriter.h" 12 #include "llvm/MC/MCELFObjectWriter.h" 13 #include "llvm/MC/MCGOFFObjectWriter.h" 14 #include "llvm/MC/MCMachObjectWriter.h" 15 #include "llvm/MC/MCObjectWriter.h" 16 #include "llvm/MC/MCSPIRVObjectWriter.h" 17 #include "llvm/MC/MCWasmObjectWriter.h" 18 #include "llvm/MC/MCWinCOFFObjectWriter.h" 19 #include "llvm/MC/MCXCOFFObjectWriter.h" 20 #include <cassert> 21 #include <cstddef> 22 #include <cstdint> 23 24 using namespace llvm; 25 26 MCAsmBackend::~MCAsmBackend() = default; 27 28 MCContext &MCAsmBackend::getContext() const { return Asm->getContext(); } 29 30 std::unique_ptr<MCObjectWriter> 31 MCAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const { 32 auto TW = createObjectTargetWriter(); 33 bool IsLE = Endian == llvm::endianness::little; 34 switch (TW->getFormat()) { 35 case Triple::MachO: 36 return std::make_unique<MachObjectWriter>( 37 cast<MCMachObjectTargetWriter>(std::move(TW)), OS, IsLE); 38 case Triple::COFF: 39 return createWinCOFFObjectWriter( 40 cast<MCWinCOFFObjectTargetWriter>(std::move(TW)), OS); 41 case Triple::ELF: 42 return std::make_unique<ELFObjectWriter>( 43 cast<MCELFObjectTargetWriter>(std::move(TW)), OS, IsLE); 44 case Triple::SPIRV: 45 return createSPIRVObjectWriter( 46 cast<MCSPIRVObjectTargetWriter>(std::move(TW)), OS); 47 case Triple::Wasm: 48 return createWasmObjectWriter(cast<MCWasmObjectTargetWriter>(std::move(TW)), 49 OS); 50 case Triple::GOFF: 51 return createGOFFObjectWriter(cast<MCGOFFObjectTargetWriter>(std::move(TW)), 52 OS); 53 case Triple::XCOFF: 54 return createXCOFFObjectWriter( 55 cast<MCXCOFFObjectTargetWriter>(std::move(TW)), OS); 56 case Triple::DXContainer: 57 return std::make_unique<DXContainerObjectWriter>( 58 cast<MCDXContainerTargetWriter>(std::move(TW)), OS); 59 default: 60 llvm_unreachable("unexpected object format"); 61 } 62 } 63 64 std::unique_ptr<MCObjectWriter> 65 MCAsmBackend::createDwoObjectWriter(raw_pwrite_stream &OS, 66 raw_pwrite_stream &DwoOS) const { 67 auto TW = createObjectTargetWriter(); 68 switch (TW->getFormat()) { 69 case Triple::COFF: 70 return createWinCOFFDwoObjectWriter( 71 cast<MCWinCOFFObjectTargetWriter>(std::move(TW)), OS, DwoOS); 72 case Triple::ELF: 73 return std::make_unique<ELFObjectWriter>( 74 cast<MCELFObjectTargetWriter>(std::move(TW)), OS, DwoOS, 75 Endian == llvm::endianness::little); 76 case Triple::Wasm: 77 return createWasmDwoObjectWriter( 78 cast<MCWasmObjectTargetWriter>(std::move(TW)), OS, DwoOS); 79 default: 80 report_fatal_error("dwo only supported with COFF, ELF, and Wasm"); 81 } 82 } 83 84 std::optional<MCFixupKind> MCAsmBackend::getFixupKind(StringRef Name) const { 85 return std::nullopt; 86 } 87 88 MCFixupKindInfo MCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const { 89 // clang-format off 90 static const MCFixupKindInfo Builtins[] = { 91 {"FK_NONE", 0, 0, 0}, 92 {"FK_Data_1", 0, 8, 0}, 93 {"FK_Data_2", 0, 16, 0}, 94 {"FK_Data_4", 0, 32, 0}, 95 {"FK_Data_8", 0, 64, 0}, 96 {"FK_Data_leb128", 0, 0, 0}, 97 {"FK_SecRel_1", 0, 8, 0}, 98 {"FK_SecRel_2", 0, 16, 0}, 99 {"FK_SecRel_4", 0, 32, 0}, 100 {"FK_SecRel_8", 0, 64, 0}, 101 }; 102 // clang-format on 103 104 assert(size_t(Kind - FK_NONE) < std::size(Builtins) && "Unknown fixup kind"); 105 return Builtins[Kind - FK_NONE]; 106 } 107 108 bool MCAsmBackend::fixupNeedsRelaxationAdvanced(const MCFixup &Fixup, 109 const MCValue &, uint64_t Value, 110 bool Resolved) const { 111 if (!Resolved) 112 return true; 113 return fixupNeedsRelaxation(Fixup, Value); 114 } 115 116 void MCAsmBackend::maybeAddReloc(const MCFragment &F, const MCFixup &Fixup, 117 const MCValue &Target, uint64_t &Value, 118 bool IsResolved) { 119 if (!IsResolved) 120 Asm->getWriter().recordRelocation(F, Fixup, Target, Value); 121 } 122 123 bool MCAsmBackend::isDarwinCanonicalPersonality(const MCSymbol *Sym) const { 124 // Consider a NULL personality (ie., no personality encoding) to be canonical 125 // because it's always at 0. 126 if (!Sym) 127 return true; 128 129 if (!Sym->isMachO()) 130 llvm_unreachable("Expected MachO symbols only"); 131 132 StringRef name = Sym->getName(); 133 // XXX: We intentionally leave out "___gcc_personality_v0" because, despite 134 // being system-defined like these two, it is not very commonly-used. 135 // Reserving an empty slot for it seems silly. 136 return name == "___gxx_personality_v0" || name == "___objc_personality_v0"; 137 } 138 139 const MCSubtargetInfo *MCAsmBackend::getSubtargetInfo(const MCFragment &F) { 140 const MCSubtargetInfo *STI = nullptr; 141 if (auto *DF = dyn_cast<MCEncodedFragment>(&F)) { 142 STI = DF->getSubtargetInfo(); 143 assert(!DF->hasInstructions() || STI != nullptr); 144 } 145 return STI; 146 } 147