1 //===- lib/MC/AArch64ELFStreamer.cpp - ELF Object Output for AArch64 ------===//
3 // The LLVM Compiler Infrastructure
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
8 //===----------------------------------------------------------------------===//
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.
14 //===----------------------------------------------------------------------===//
16 #include "AArch64TargetStreamer.h"
17 #include "AArch64WinCOFFStreamer.h"
18 #include "llvm/ADT/DenseMap.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/ADT/Triple.h"
21 #include "llvm/ADT/Twine.h"
22 #include "llvm/BinaryFormat/ELF.h"
23 #include "llvm/MC/MCAsmBackend.h"
24 #include "llvm/MC/MCAssembler.h"
25 #include "llvm/MC/MCCodeEmitter.h"
26 #include "llvm/MC/MCContext.h"
27 #include "llvm/MC/MCELFStreamer.h"
28 #include "llvm/MC/MCExpr.h"
29 #include "llvm/MC/MCInst.h"
30 #include "llvm/MC/MCObjectWriter.h"
31 #include "llvm/MC/MCSection.h"
32 #include "llvm/MC/MCStreamer.h"
33 #include "llvm/MC/MCSubtargetInfo.h"
34 #include "llvm/MC/MCSymbolELF.h"
35 #include "llvm/MC/MCWinCOFFStreamer.h"
36 #include "llvm/Support/Casting.h"
37 #include "llvm/Support/FormattedStream.h"
38 #include "llvm/Support/raw_ostream.h"
44 class AArch64ELFStreamer;
46 class AArch64TargetAsmStreamer : public AArch64TargetStreamer {
47 formatted_raw_ostream &OS;
49 void emitInst(uint32_t Inst) override;
52 AArch64TargetAsmStreamer(MCStreamer &S, formatted_raw_ostream &OS);
55 AArch64TargetAsmStreamer::AArch64TargetAsmStreamer(MCStreamer &S,
56 formatted_raw_ostream &OS)
57 : AArch64TargetStreamer(S), OS(OS) {}
59 void AArch64TargetAsmStreamer::emitInst(uint32_t Inst) {
60 OS << "\t.inst\t0x" << Twine::utohexstr(Inst) << "\n";
63 class AArch64TargetELFStreamer : public AArch64TargetStreamer {
65 AArch64ELFStreamer &getStreamer();
67 void emitInst(uint32_t Inst) override;
70 AArch64TargetELFStreamer(MCStreamer &S) : AArch64TargetStreamer(S) {}
73 /// Extend the generic ELFStreamer class so that it can emit mapping symbols at
74 /// the appropriate points in the object files. These symbols are defined in the
76 /// infocenter.arm.com/help/topic/com.arm.doc.ihi0056a/IHI0056A_aaelf64.pdf
78 /// In brief: $x or $d should be emitted at the start of each contiguous region
79 /// of A64 code or data in a section. In practice, this emission does not rely
80 /// on explicit assembler directives but on inherent properties of the
81 /// directives doing the emission (e.g. ".byte" is data, "add x0, x0, x0" an
84 /// As a result this system is orthogonal to the DataRegion infrastructure used
86 class AArch64ELFStreamer : public MCELFStreamer {
88 friend class AArch64TargetELFStreamer;
90 AArch64ELFStreamer(MCContext &Context, std::unique_ptr<MCAsmBackend> TAB,
91 std::unique_ptr<MCObjectWriter> OW,
92 std::unique_ptr<MCCodeEmitter> Emitter)
93 : MCELFStreamer(Context, std::move(TAB), std::move(OW),
95 MappingSymbolCounter(0), LastEMS(EMS_None) {}
97 void ChangeSection(MCSection *Section, const MCExpr *Subsection) override {
98 // We have to keep track of the mapping symbol state of any sections we
99 // use. Each one should start off as EMS_None, which is provided as the
100 // default constructor by DenseMap::lookup.
101 LastMappingSymbols[getPreviousSection().first] = LastEMS;
102 LastEMS = LastMappingSymbols.lookup(Section);
104 MCELFStreamer::ChangeSection(Section, Subsection);
107 // Reset state between object emissions
108 void reset() override {
109 MappingSymbolCounter = 0;
110 MCELFStreamer::reset();
111 LastMappingSymbols.clear();
115 /// This function is the one used to emit instruction data into the ELF
116 /// streamer. We override it to add the appropriate mapping symbol if
118 void EmitInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
120 EmitA64MappingSymbol();
121 MCELFStreamer::EmitInstruction(Inst, STI);
124 /// Emit a 32-bit value as an instruction. This is only used for the .inst
125 /// directive, EmitInstruction should be used in other cases.
126 void emitInst(uint32_t Inst) {
129 // We can't just use EmitIntValue here, as that will emit a data mapping
130 // symbol, and swap the endianness on big-endian systems (instructions are
131 // always little-endian).
132 for (unsigned I = 0; I < 4; ++I) {
133 Buffer[I] = uint8_t(Inst);
137 EmitA64MappingSymbol();
138 MCELFStreamer::EmitBytes(StringRef(Buffer, 4));
141 /// This is one of the functions used to emit data into an ELF section, so the
142 /// AArch64 streamer overrides it to add the appropriate mapping symbol ($d)
144 void EmitBytes(StringRef Data) override {
145 EmitDataMappingSymbol();
146 MCELFStreamer::EmitBytes(Data);
149 /// This is one of the functions used to emit data into an ELF section, so the
150 /// AArch64 streamer overrides it to add the appropriate mapping symbol ($d)
152 void EmitValueImpl(const MCExpr *Value, unsigned Size, SMLoc Loc) override {
153 EmitDataMappingSymbol();
154 MCELFStreamer::EmitValueImpl(Value, Size, Loc);
158 enum ElfMappingSymbol {
164 void EmitDataMappingSymbol() {
165 if (LastEMS == EMS_Data)
167 EmitMappingSymbol("$d");
171 void EmitA64MappingSymbol() {
172 if (LastEMS == EMS_A64)
174 EmitMappingSymbol("$x");
178 void EmitMappingSymbol(StringRef Name) {
179 auto *Symbol = cast<MCSymbolELF>(getContext().getOrCreateSymbol(
180 Name + "." + Twine(MappingSymbolCounter++)));
182 Symbol->setType(ELF::STT_NOTYPE);
183 Symbol->setBinding(ELF::STB_LOCAL);
184 Symbol->setExternal(false);
187 int64_t MappingSymbolCounter;
189 DenseMap<const MCSection *, ElfMappingSymbol> LastMappingSymbols;
190 ElfMappingSymbol LastEMS;
193 } // end anonymous namespace
195 AArch64ELFStreamer &AArch64TargetELFStreamer::getStreamer() {
196 return static_cast<AArch64ELFStreamer &>(Streamer);
199 void AArch64TargetELFStreamer::emitInst(uint32_t Inst) {
200 getStreamer().emitInst(Inst);
205 MCTargetStreamer *createAArch64AsmTargetStreamer(MCStreamer &S,
206 formatted_raw_ostream &OS,
207 MCInstPrinter *InstPrint,
209 return new AArch64TargetAsmStreamer(S, OS);
212 MCELFStreamer *createAArch64ELFStreamer(MCContext &Context,
213 std::unique_ptr<MCAsmBackend> TAB,
214 std::unique_ptr<MCObjectWriter> OW,
215 std::unique_ptr<MCCodeEmitter> Emitter,
217 AArch64ELFStreamer *S = new AArch64ELFStreamer(
218 Context, std::move(TAB), std::move(OW), std::move(Emitter));
220 S->getAssembler().setRelaxAll(true);
225 createAArch64ObjectTargetStreamer(MCStreamer &S, const MCSubtargetInfo &STI) {
226 const Triple &TT = STI.getTargetTriple();
227 if (TT.isOSBinFormatELF())
228 return new AArch64TargetELFStreamer(S);
229 if (TT.isOSBinFormatCOFF())
230 return new AArch64TargetWinCOFFStreamer(S);
234 } // end namespace llvm