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/MCDXContainerWriter.h"
11 #include "llvm/MC/MCELFObjectWriter.h"
12 #include "llvm/MC/MCFixupKindInfo.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(llvm::endianness Endian, unsigned RelaxFixupKind)
27     : Endian(Endian), RelaxFixupKind(RelaxFixupKind) {}
28 
29 MCAsmBackend::~MCAsmBackend() = default;
30 
31 std::unique_ptr<MCObjectWriter>
32 MCAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const {
33   auto TW = createObjectTargetWriter();
34   switch (TW->getFormat()) {
35   case Triple::ELF:
36     return createELFObjectWriter(cast<MCELFObjectTargetWriter>(std::move(TW)),
37                                  OS, Endian == llvm::endianness::little);
38   case Triple::MachO:
39     return createMachObjectWriter(cast<MCMachObjectTargetWriter>(std::move(TW)),
40                                   OS, Endian == llvm::endianness::little);
41   case Triple::COFF:
42     return createWinCOFFObjectWriter(
43         cast<MCWinCOFFObjectTargetWriter>(std::move(TW)), OS);
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 createDXContainerObjectWriter(
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 createELFDwoObjectWriter(
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 const MCFixupKindInfo &MCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
89   static const MCFixupKindInfo Builtins[] = {
90       {"FK_NONE", 0, 0, 0},
91       {"FK_Data_1", 0, 8, 0},
92       {"FK_Data_2", 0, 16, 0},
93       {"FK_Data_4", 0, 32, 0},
94       {"FK_Data_8", 0, 64, 0},
95       {"FK_Data_leb128", 0, 0, 0},
96       {"FK_PCRel_1", 0, 8, MCFixupKindInfo::FKF_IsPCRel},
97       {"FK_PCRel_2", 0, 16, MCFixupKindInfo::FKF_IsPCRel},
98       {"FK_PCRel_4", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
99       {"FK_PCRel_8", 0, 64, MCFixupKindInfo::FKF_IsPCRel},
100       {"FK_GPRel_1", 0, 8, 0},
101       {"FK_GPRel_2", 0, 16, 0},
102       {"FK_GPRel_4", 0, 32, 0},
103       {"FK_GPRel_8", 0, 64, 0},
104       {"FK_DTPRel_4", 0, 32, 0},
105       {"FK_DTPRel_8", 0, 64, 0},
106       {"FK_TPRel_4", 0, 32, 0},
107       {"FK_TPRel_8", 0, 64, 0},
108       {"FK_SecRel_1", 0, 8, 0},
109       {"FK_SecRel_2", 0, 16, 0},
110       {"FK_SecRel_4", 0, 32, 0},
111       {"FK_SecRel_8", 0, 64, 0},
112   };
113 
114   assert((size_t)Kind <= std::size(Builtins) && "Unknown fixup kind");
115   return Builtins[Kind];
116 }
117 
118 bool MCAsmBackend::fixupNeedsRelaxationAdvanced(
119     const MCFixup &Fixup, bool Resolved, uint64_t Value,
120     const MCRelaxableFragment *DF, const MCAsmLayout &Layout,
121     const bool WasForced) const {
122   if (!Resolved)
123     return true;
124   return fixupNeedsRelaxation(Fixup, Value, DF, Layout);
125 }
126 
127 bool MCAsmBackend::isDarwinCanonicalPersonality(const MCSymbol *Sym) const {
128   // Consider a NULL personality (ie., no personality encoding) to be canonical
129   // because it's always at 0.
130   if (!Sym)
131     return true;
132 
133   if (!Sym->isMachO())
134     llvm_unreachable("Expected MachO symbols only");
135 
136   StringRef name = Sym->getName();
137   // XXX: We intentionally leave out "___gcc_personality_v0" because, despite
138   // being system-defined like these two, it is not very commonly-used.
139   // Reserving an empty slot for it seems silly.
140   return name == "___gxx_personality_v0" || name == "___objc_personality_v0";
141 }
142