xref: /llvm-project/llvm/lib/MC/MCAsmBackend.cpp (revision 22c7317f1e954b34a46640db5d509bae1c633348)
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/MCFixupKindInfo.h"
14 #include "llvm/MC/MCGOFFObjectWriter.h"
15 #include "llvm/MC/MCMachObjectWriter.h"
16 #include "llvm/MC/MCObjectWriter.h"
17 #include "llvm/MC/MCSPIRVObjectWriter.h"
18 #include "llvm/MC/MCWasmObjectWriter.h"
19 #include "llvm/MC/MCWinCOFFObjectWriter.h"
20 #include "llvm/MC/MCXCOFFObjectWriter.h"
21 #include <cassert>
22 #include <cstddef>
23 #include <cstdint>
24 
25 using namespace llvm;
26 
27 MCAsmBackend::MCAsmBackend(llvm::endianness Endian, unsigned RelaxFixupKind)
28     : Endian(Endian), RelaxFixupKind(RelaxFixupKind) {}
29 
30 MCAsmBackend::~MCAsmBackend() = default;
31 
32 std::unique_ptr<MCObjectWriter>
33 MCAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const {
34   auto TW = createObjectTargetWriter();
35   switch (TW->getFormat()) {
36   case Triple::ELF:
37     return createELFObjectWriter(cast<MCELFObjectTargetWriter>(std::move(TW)),
38                                  OS, Endian == llvm::endianness::little);
39   case Triple::MachO:
40     return createMachObjectWriter(cast<MCMachObjectTargetWriter>(std::move(TW)),
41                                   OS, Endian == llvm::endianness::little);
42   case Triple::COFF:
43     return createWinCOFFObjectWriter(
44         cast<MCWinCOFFObjectTargetWriter>(std::move(TW)), OS);
45   case Triple::SPIRV:
46     return createSPIRVObjectWriter(
47         cast<MCSPIRVObjectTargetWriter>(std::move(TW)), OS);
48   case Triple::Wasm:
49     return createWasmObjectWriter(cast<MCWasmObjectTargetWriter>(std::move(TW)),
50                                   OS);
51   case Triple::GOFF:
52     return createGOFFObjectWriter(cast<MCGOFFObjectTargetWriter>(std::move(TW)),
53                                   OS);
54   case Triple::XCOFF:
55     return createXCOFFObjectWriter(
56         cast<MCXCOFFObjectTargetWriter>(std::move(TW)), OS);
57   case Triple::DXContainer:
58     return createDXContainerObjectWriter(
59         cast<MCDXContainerTargetWriter>(std::move(TW)), OS);
60   default:
61     llvm_unreachable("unexpected object format");
62   }
63 }
64 
65 std::unique_ptr<MCObjectWriter>
66 MCAsmBackend::createDwoObjectWriter(raw_pwrite_stream &OS,
67                                     raw_pwrite_stream &DwoOS) const {
68   auto TW = createObjectTargetWriter();
69   switch (TW->getFormat()) {
70   case Triple::COFF:
71     return createWinCOFFDwoObjectWriter(
72         cast<MCWinCOFFObjectTargetWriter>(std::move(TW)), OS, DwoOS);
73   case Triple::ELF:
74     return createELFDwoObjectWriter(
75         cast<MCELFObjectTargetWriter>(std::move(TW)), OS, DwoOS,
76         Endian == llvm::endianness::little);
77   case Triple::Wasm:
78     return createWasmDwoObjectWriter(
79         cast<MCWasmObjectTargetWriter>(std::move(TW)), OS, DwoOS);
80   default:
81     report_fatal_error("dwo only supported with COFF, ELF, and Wasm");
82   }
83 }
84 
85 std::optional<MCFixupKind> MCAsmBackend::getFixupKind(StringRef Name) const {
86   return std::nullopt;
87 }
88 
89 const MCFixupKindInfo &MCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
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_PCRel_1", 0, 8, MCFixupKindInfo::FKF_IsPCRel},
98       {"FK_PCRel_2", 0, 16, MCFixupKindInfo::FKF_IsPCRel},
99       {"FK_PCRel_4", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
100       {"FK_PCRel_8", 0, 64, MCFixupKindInfo::FKF_IsPCRel},
101       {"FK_GPRel_1", 0, 8, 0},
102       {"FK_GPRel_2", 0, 16, 0},
103       {"FK_GPRel_4", 0, 32, 0},
104       {"FK_GPRel_8", 0, 64, 0},
105       {"FK_DTPRel_4", 0, 32, 0},
106       {"FK_DTPRel_8", 0, 64, 0},
107       {"FK_TPRel_4", 0, 32, 0},
108       {"FK_TPRel_8", 0, 64, 0},
109       {"FK_SecRel_1", 0, 8, 0},
110       {"FK_SecRel_2", 0, 16, 0},
111       {"FK_SecRel_4", 0, 32, 0},
112       {"FK_SecRel_8", 0, 64, 0},
113   };
114 
115   assert((size_t)Kind <= std::size(Builtins) && "Unknown fixup kind");
116   return Builtins[Kind];
117 }
118 
119 bool MCAsmBackend::fixupNeedsRelaxationAdvanced(const MCAssembler &Asm,
120                                                 const MCFixup &Fixup,
121                                                 bool Resolved, uint64_t Value,
122                                                 const MCRelaxableFragment *DF,
123                                                 const bool WasForced) const {
124   if (!Resolved)
125     return true;
126   return fixupNeedsRelaxation(Fixup, Value, DF, *Asm.getLayout());
127 }
128 
129 bool MCAsmBackend::isDarwinCanonicalPersonality(const MCSymbol *Sym) const {
130   // Consider a NULL personality (ie., no personality encoding) to be canonical
131   // because it's always at 0.
132   if (!Sym)
133     return true;
134 
135   if (!Sym->isMachO())
136     llvm_unreachable("Expected MachO symbols only");
137 
138   StringRef name = Sym->getName();
139   // XXX: We intentionally leave out "___gcc_personality_v0" because, despite
140   // being system-defined like these two, it is not very commonly-used.
141   // Reserving an empty slot for it seems silly.
142   return name == "___gxx_personality_v0" || name == "___objc_personality_v0";
143 }
144