1 //===- lib/MC/AArch64ELFStreamer.cpp - ELF Object Output for AArch64 ------===//
2 //
3 // The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file assembles .s files and emits AArch64 ELF .o object files. Different
11 // from generic ELF streamer in emitting mapping symbols ($x and $d) to delimit
12 // regions of data and code.
13 //
14 //===----------------------------------------------------------------------===//
15
16 #include "AArch64TargetStreamer.h"
17 #include "llvm/MC/MCELFStreamer.h"
18 #include "llvm/ADT/SmallPtrSet.h"
19 #include "llvm/ADT/StringExtras.h"
20 #include "llvm/ADT/Twine.h"
21 #include "llvm/MC/MCAsmBackend.h"
22 #include "llvm/MC/MCAsmInfo.h"
23 #include "llvm/MC/MCAssembler.h"
24 #include "llvm/MC/MCCodeEmitter.h"
25 #include "llvm/MC/MCContext.h"
26 #include "llvm/MC/MCELFStreamer.h"
27 #include "llvm/MC/MCExpr.h"
28 #include "llvm/MC/MCInst.h"
29 #include "llvm/MC/MCObjectStreamer.h"
30 #include "llvm/MC/MCSection.h"
31 #include "llvm/MC/MCSectionELF.h"
32 #include "llvm/MC/MCStreamer.h"
33 #include "llvm/MC/MCSymbolELF.h"
34 #include "llvm/MC/MCValue.h"
35 #include "llvm/Support/Debug.h"
36 #include "llvm/Support/ELF.h"
37 #include "llvm/Support/ErrorHandling.h"
38 #include "llvm/Support/FormattedStream.h"
39 #include "llvm/Support/raw_ostream.h"
40
41 using namespace llvm;
42
43 namespace {
44
45 class AArch64ELFStreamer;
46
47 class AArch64TargetAsmStreamer : public AArch64TargetStreamer {
48 formatted_raw_ostream &OS;
49
50 void emitInst(uint32_t Inst) override;
51
52 public:
53 AArch64TargetAsmStreamer(MCStreamer &S, formatted_raw_ostream &OS);
54 };
55
AArch64TargetAsmStreamer(MCStreamer & S,formatted_raw_ostream & OS)56 AArch64TargetAsmStreamer::AArch64TargetAsmStreamer(MCStreamer &S,
57 formatted_raw_ostream &OS)
58 : AArch64TargetStreamer(S), OS(OS) {}
59
emitInst(uint32_t Inst)60 void AArch64TargetAsmStreamer::emitInst(uint32_t Inst) {
61 OS << "\t.inst\t0x" << Twine::utohexstr(Inst) << "\n";
62 }
63
64 class AArch64TargetELFStreamer : public AArch64TargetStreamer {
65 private:
66 AArch64ELFStreamer &getStreamer();
67
68 void emitInst(uint32_t Inst) override;
69
70 public:
AArch64TargetELFStreamer(MCStreamer & S)71 AArch64TargetELFStreamer(MCStreamer &S) : AArch64TargetStreamer(S) {}
72 };
73
74 /// Extend the generic ELFStreamer class so that it can emit mapping symbols at
75 /// the appropriate points in the object files. These symbols are defined in the
76 /// AArch64 ELF ABI:
77 /// infocenter.arm.com/help/topic/com.arm.doc.ihi0056a/IHI0056A_aaelf64.pdf
78 ///
79 /// In brief: $x or $d should be emitted at the start of each contiguous region
80 /// of A64 code or data in a section. In practice, this emission does not rely
81 /// on explicit assembler directives but on inherent properties of the
82 /// directives doing the emission (e.g. ".byte" is data, "add x0, x0, x0" an
83 /// instruction).
84 ///
85 /// As a result this system is orthogonal to the DataRegion infrastructure used
86 /// by MachO. Beware!
87 class AArch64ELFStreamer : public MCELFStreamer {
88 public:
89 friend class AArch64TargetELFStreamer;
90
AArch64ELFStreamer(MCContext & Context,MCAsmBackend & TAB,raw_pwrite_stream & OS,MCCodeEmitter * Emitter)91 AArch64ELFStreamer(MCContext &Context, MCAsmBackend &TAB,
92 raw_pwrite_stream &OS, MCCodeEmitter *Emitter)
93 : MCELFStreamer(Context, TAB, OS, Emitter), MappingSymbolCounter(0),
94 LastEMS(EMS_None) {}
95
ChangeSection(MCSection * Section,const MCExpr * Subsection)96 void ChangeSection(MCSection *Section, const MCExpr *Subsection) override {
97 // We have to keep track of the mapping symbol state of any sections we
98 // use. Each one should start off as EMS_None, which is provided as the
99 // default constructor by DenseMap::lookup.
100 LastMappingSymbols[getPreviousSection().first] = LastEMS;
101 LastEMS = LastMappingSymbols.lookup(Section);
102
103 MCELFStreamer::ChangeSection(Section, Subsection);
104 }
105
106 /// This function is the one used to emit instruction data into the ELF
107 /// streamer. We override it to add the appropriate mapping symbol if
108 /// necessary.
EmitInstruction(const MCInst & Inst,const MCSubtargetInfo & STI)109 void EmitInstruction(const MCInst &Inst,
110 const MCSubtargetInfo &STI) override {
111 EmitA64MappingSymbol();
112 MCELFStreamer::EmitInstruction(Inst, STI);
113 }
114
emitInst(uint32_t Inst)115 void emitInst(uint32_t Inst) {
116 EmitA64MappingSymbol();
117 MCELFStreamer::EmitIntValue(Inst, 4);
118 }
119
120 /// This is one of the functions used to emit data into an ELF section, so the
121 /// AArch64 streamer overrides it to add the appropriate mapping symbol ($d)
122 /// if necessary.
EmitBytes(StringRef Data)123 void EmitBytes(StringRef Data) override {
124 EmitDataMappingSymbol();
125 MCELFStreamer::EmitBytes(Data);
126 }
127
128 /// This is one of the functions used to emit data into an ELF section, so the
129 /// AArch64 streamer overrides it to add the appropriate mapping symbol ($d)
130 /// if necessary.
EmitValueImpl(const MCExpr * Value,unsigned Size,SMLoc Loc)131 void EmitValueImpl(const MCExpr *Value, unsigned Size, SMLoc Loc) override {
132 EmitDataMappingSymbol();
133 MCELFStreamer::EmitValueImpl(Value, Size, Loc);
134 }
135
136 private:
137 enum ElfMappingSymbol {
138 EMS_None,
139 EMS_A64,
140 EMS_Data
141 };
142
EmitDataMappingSymbol()143 void EmitDataMappingSymbol() {
144 if (LastEMS == EMS_Data)
145 return;
146 EmitMappingSymbol("$d");
147 LastEMS = EMS_Data;
148 }
149
EmitA64MappingSymbol()150 void EmitA64MappingSymbol() {
151 if (LastEMS == EMS_A64)
152 return;
153 EmitMappingSymbol("$x");
154 LastEMS = EMS_A64;
155 }
156
EmitMappingSymbol(StringRef Name)157 void EmitMappingSymbol(StringRef Name) {
158 auto *Symbol = cast<MCSymbolELF>(getContext().getOrCreateSymbol(
159 Name + "." + Twine(MappingSymbolCounter++)));
160 EmitLabel(Symbol);
161 Symbol->setType(ELF::STT_NOTYPE);
162 Symbol->setBinding(ELF::STB_LOCAL);
163 Symbol->setExternal(false);
164 }
165
166 int64_t MappingSymbolCounter;
167
168 DenseMap<const MCSection *, ElfMappingSymbol> LastMappingSymbols;
169 ElfMappingSymbol LastEMS;
170 };
171 } // end anonymous namespace
172
getStreamer()173 AArch64ELFStreamer &AArch64TargetELFStreamer::getStreamer() {
174 return static_cast<AArch64ELFStreamer &>(Streamer);
175 }
176
emitInst(uint32_t Inst)177 void AArch64TargetELFStreamer::emitInst(uint32_t Inst) {
178 getStreamer().emitInst(Inst);
179 }
180
181 namespace llvm {
createAArch64AsmTargetStreamer(MCStreamer & S,formatted_raw_ostream & OS,MCInstPrinter * InstPrint,bool isVerboseAsm)182 MCTargetStreamer *createAArch64AsmTargetStreamer(MCStreamer &S,
183 formatted_raw_ostream &OS,
184 MCInstPrinter *InstPrint,
185 bool isVerboseAsm) {
186 return new AArch64TargetAsmStreamer(S, OS);
187 }
188
createAArch64ELFStreamer(MCContext & Context,MCAsmBackend & TAB,raw_pwrite_stream & OS,MCCodeEmitter * Emitter,bool RelaxAll)189 MCELFStreamer *createAArch64ELFStreamer(MCContext &Context, MCAsmBackend &TAB,
190 raw_pwrite_stream &OS,
191 MCCodeEmitter *Emitter, bool RelaxAll) {
192 AArch64ELFStreamer *S = new AArch64ELFStreamer(Context, TAB, OS, Emitter);
193 if (RelaxAll)
194 S->getAssembler().setRelaxAll(true);
195 return S;
196 }
197
198 MCTargetStreamer *
createAArch64ObjectTargetStreamer(MCStreamer & S,const MCSubtargetInfo & STI)199 createAArch64ObjectTargetStreamer(MCStreamer &S, const MCSubtargetInfo &STI) {
200 const Triple &TT = STI.getTargetTriple();
201 if (TT.isOSBinFormatELF())
202 return new AArch64TargetELFStreamer(S);
203 return nullptr;
204 }
205 }
206