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/MCMachObjectWriter.h"
14 #include "llvm/MC/MCObjectWriter.h"
15 #include "llvm/MC/MCSPIRVObjectWriter.h"
16 #include "llvm/MC/MCWasmObjectWriter.h"
17 #include "llvm/MC/MCWinCOFFObjectWriter.h"
18 #include "llvm/MC/MCXCOFFObjectWriter.h"
19 #include <cassert>
20 #include <cstddef>
21 #include <cstdint>
22 
23 using namespace llvm;
24 
25 MCAsmBackend::MCAsmBackend(support::endianness Endian, unsigned RelaxFixupKind)
26     : Endian(Endian), RelaxFixupKind(RelaxFixupKind) {}
27 
28 MCAsmBackend::~MCAsmBackend() = default;
29 
30 std::unique_ptr<MCObjectWriter>
31 MCAsmBackend::createObjectWriter(raw_pwrite_stream &OS) const {
32   auto TW = createObjectTargetWriter();
33   switch (TW->getFormat()) {
34   case Triple::ELF:
35     return createELFObjectWriter(cast<MCELFObjectTargetWriter>(std::move(TW)), OS,
36                                  Endian == support::little);
37   case Triple::MachO:
38     return createMachObjectWriter(cast<MCMachObjectTargetWriter>(std::move(TW)),
39                                   OS, Endian == support::little);
40   case Triple::COFF:
41     return createWinCOFFObjectWriter(
42         cast<MCWinCOFFObjectTargetWriter>(std::move(TW)), OS);
43   case Triple::SPIRV:
44     return createSPIRVObjectWriter(
45         cast<MCSPIRVObjectTargetWriter>(std::move(TW)), OS);
46   case Triple::Wasm:
47     return createWasmObjectWriter(cast<MCWasmObjectTargetWriter>(std::move(TW)),
48                                   OS);
49   case Triple::XCOFF:
50     return createXCOFFObjectWriter(
51         cast<MCXCOFFObjectTargetWriter>(std::move(TW)), OS);
52   case Triple::DXContainer:
53     return createDXContainerObjectWriter(
54         cast<MCDXContainerTargetWriter>(std::move(TW)), OS);
55   default:
56     llvm_unreachable("unexpected object format");
57   }
58 }
59 
60 std::unique_ptr<MCObjectWriter>
61 MCAsmBackend::createDwoObjectWriter(raw_pwrite_stream &OS,
62                                     raw_pwrite_stream &DwoOS) const {
63   auto TW = createObjectTargetWriter();
64   switch (TW->getFormat()) {
65   case Triple::COFF:
66     return createWinCOFFDwoObjectWriter(
67         cast<MCWinCOFFObjectTargetWriter>(std::move(TW)), OS, DwoOS);
68   case Triple::ELF:
69     return createELFDwoObjectWriter(
70         cast<MCELFObjectTargetWriter>(std::move(TW)), OS, DwoOS,
71         Endian == support::little);
72   case Triple::Wasm:
73     return createWasmDwoObjectWriter(
74         cast<MCWasmObjectTargetWriter>(std::move(TW)), OS, DwoOS);
75   default:
76     report_fatal_error("dwo only supported with COFF, ELF, and Wasm");
77   }
78 }
79 
80 std::optional<MCFixupKind> MCAsmBackend::getFixupKind(StringRef Name) const {
81   return std::nullopt;
82 }
83 
84 const MCFixupKindInfo &MCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
85   static const MCFixupKindInfo Builtins[] = {
86       {"FK_NONE", 0, 0, 0},
87       {"FK_Data_1", 0, 8, 0},
88       {"FK_Data_2", 0, 16, 0},
89       {"FK_Data_4", 0, 32, 0},
90       {"FK_Data_8", 0, 64, 0},
91       {"FK_Data_6b", 0, 6, 0},
92       {"FK_PCRel_1", 0, 8, MCFixupKindInfo::FKF_IsPCRel},
93       {"FK_PCRel_2", 0, 16, MCFixupKindInfo::FKF_IsPCRel},
94       {"FK_PCRel_4", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
95       {"FK_PCRel_8", 0, 64, MCFixupKindInfo::FKF_IsPCRel},
96       {"FK_GPRel_1", 0, 8, 0},
97       {"FK_GPRel_2", 0, 16, 0},
98       {"FK_GPRel_4", 0, 32, 0},
99       {"FK_GPRel_8", 0, 64, 0},
100       {"FK_DTPRel_4", 0, 32, 0},
101       {"FK_DTPRel_8", 0, 64, 0},
102       {"FK_TPRel_4", 0, 32, 0},
103       {"FK_TPRel_8", 0, 64, 0},
104       {"FK_SecRel_1", 0, 8, 0},
105       {"FK_SecRel_2", 0, 16, 0},
106       {"FK_SecRel_4", 0, 32, 0},
107       {"FK_SecRel_8", 0, 64, 0},
108   };
109 
110   assert((size_t)Kind <= std::size(Builtins) && "Unknown fixup kind");
111   return Builtins[Kind];
112 }
113 
114 bool MCAsmBackend::fixupNeedsRelaxationAdvanced(
115     const MCFixup &Fixup, bool Resolved, uint64_t Value,
116     const MCRelaxableFragment *DF, const MCAsmLayout &Layout,
117     const bool WasForced) const {
118   if (!Resolved)
119     return true;
120   return fixupNeedsRelaxation(Fixup, Value, DF, Layout);
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