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/ADT/None.h"
11 #include "llvm/ADT/STLExtras.h"
12 #include "llvm/MC/MCCodePadder.h"
13 #include "llvm/MC/MCELFObjectWriter.h"
14 #include "llvm/MC/MCFixupKindInfo.h"
15 #include "llvm/MC/MCMachObjectWriter.h"
16 #include "llvm/MC/MCObjectWriter.h"
17 #include "llvm/MC/MCWasmObjectWriter.h"
18 #include "llvm/MC/MCWinCOFFObjectWriter.h"
19 #include <cassert>
20 #include <cstddef>
21 #include <cstdint>
22 
23 using namespace llvm;
24 
25 MCAsmBackend::MCAsmBackend(support::endianness Endian)
26     : CodePadder(new MCCodePadder()), Endian(Endian) {}
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::Wasm:
44     return createWasmObjectWriter(cast<MCWasmObjectTargetWriter>(std::move(TW)),
45                                   OS);
46   default:
47     llvm_unreachable("unexpected object format");
48   }
49 }
50 
51 std::unique_ptr<MCObjectWriter>
52 MCAsmBackend::createDwoObjectWriter(raw_pwrite_stream &OS,
53                                     raw_pwrite_stream &DwoOS) const {
54   auto TW = createObjectTargetWriter();
55   if (TW->getFormat() != Triple::ELF)
56     report_fatal_error("dwo only supported with ELF");
57   return createELFDwoObjectWriter(cast<MCELFObjectTargetWriter>(std::move(TW)),
58                                   OS, DwoOS, Endian == support::little);
59 }
60 
61 Optional<MCFixupKind> MCAsmBackend::getFixupKind(StringRef Name) const {
62   return None;
63 }
64 
65 const MCFixupKindInfo &MCAsmBackend::getFixupKindInfo(MCFixupKind Kind) const {
66   static const MCFixupKindInfo Builtins[] = {
67       {"FK_NONE", 0, 0, 0},
68       {"FK_Data_1", 0, 8, 0},
69       {"FK_Data_2", 0, 16, 0},
70       {"FK_Data_4", 0, 32, 0},
71       {"FK_Data_8", 0, 64, 0},
72       {"FK_PCRel_1", 0, 8, MCFixupKindInfo::FKF_IsPCRel},
73       {"FK_PCRel_2", 0, 16, MCFixupKindInfo::FKF_IsPCRel},
74       {"FK_PCRel_4", 0, 32, MCFixupKindInfo::FKF_IsPCRel},
75       {"FK_PCRel_8", 0, 64, MCFixupKindInfo::FKF_IsPCRel},
76       {"FK_GPRel_1", 0, 8, 0},
77       {"FK_GPRel_2", 0, 16, 0},
78       {"FK_GPRel_4", 0, 32, 0},
79       {"FK_GPRel_8", 0, 64, 0},
80       {"FK_DTPRel_4", 0, 32, 0},
81       {"FK_DTPRel_8", 0, 64, 0},
82       {"FK_TPRel_4", 0, 32, 0},
83       {"FK_TPRel_8", 0, 64, 0},
84       {"FK_SecRel_1", 0, 8, 0},
85       {"FK_SecRel_2", 0, 16, 0},
86       {"FK_SecRel_4", 0, 32, 0},
87       {"FK_SecRel_8", 0, 64, 0},
88       {"FK_Data_Add_1", 0, 8, 0},
89       {"FK_Data_Add_2", 0, 16, 0},
90       {"FK_Data_Add_4", 0, 32, 0},
91       {"FK_Data_Add_8", 0, 64, 0},
92       {"FK_Data_Sub_1", 0, 8, 0},
93       {"FK_Data_Sub_2", 0, 16, 0},
94       {"FK_Data_Sub_4", 0, 32, 0},
95       {"FK_Data_Sub_8", 0, 64, 0}};
96 
97   assert((size_t)Kind <= array_lengthof(Builtins) && "Unknown fixup kind");
98   return Builtins[Kind];
99 }
100 
101 bool MCAsmBackend::fixupNeedsRelaxationAdvanced(
102     const MCFixup &Fixup, bool Resolved, uint64_t Value,
103     const MCRelaxableFragment *DF, const MCAsmLayout &Layout,
104     const bool WasForced) const {
105   if (!Resolved)
106     return true;
107   return fixupNeedsRelaxation(Fixup, Value, DF, Layout);
108 }
109 
110 void MCAsmBackend::handleCodePaddingBasicBlockStart(
111     MCObjectStreamer *OS, const MCCodePaddingContext &Context) {
112   CodePadder->handleBasicBlockStart(OS, Context);
113 }
114 
115 void MCAsmBackend::handleCodePaddingBasicBlockEnd(
116     const MCCodePaddingContext &Context) {
117   CodePadder->handleBasicBlockEnd(Context);
118 }
119 
120 void MCAsmBackend::handleCodePaddingInstructionBegin(const MCInst &Inst) {
121   CodePadder->handleInstructionBegin(Inst);
122 }
123 
124 void MCAsmBackend::handleCodePaddingInstructionEnd(const MCInst &Inst) {
125   CodePadder->handleInstructionEnd(Inst);
126 }
127 
128 bool MCAsmBackend::relaxFragment(MCPaddingFragment *PF, MCAsmLayout &Layout) {
129   return CodePadder->relaxFragment(PF, Layout);
130 }
131