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 "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"
45 class AArch64ELFStreamer;
47 class AArch64TargetAsmStreamer : public AArch64TargetStreamer {
48 formatted_raw_ostream &OS;
50 void emitInst(uint32_t Inst) override;
53 AArch64TargetAsmStreamer(MCStreamer &S, formatted_raw_ostream &OS);
56 AArch64TargetAsmStreamer::AArch64TargetAsmStreamer(MCStreamer &S,
57 formatted_raw_ostream &OS)
58 : AArch64TargetStreamer(S), OS(OS) {}
60 void AArch64TargetAsmStreamer::emitInst(uint32_t Inst) {
61 OS << "\t.inst\t0x" << Twine::utohexstr(Inst) << "\n";
64 class AArch64TargetELFStreamer : public AArch64TargetStreamer {
66 AArch64ELFStreamer &getStreamer();
68 void emitInst(uint32_t Inst) override;
71 AArch64TargetELFStreamer(MCStreamer &S) : AArch64TargetStreamer(S) {}
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
77 /// infocenter.arm.com/help/topic/com.arm.doc.ihi0056a/IHI0056A_aaelf64.pdf
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
85 /// As a result this system is orthogonal to the DataRegion infrastructure used
87 class AArch64ELFStreamer : public MCELFStreamer {
89 friend class AArch64TargetELFStreamer;
91 AArch64ELFStreamer(MCContext &Context, MCAsmBackend &TAB,
92 raw_pwrite_stream &OS, MCCodeEmitter *Emitter)
93 : MCELFStreamer(Context, TAB, OS, Emitter), MappingSymbolCounter(0),
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);
103 MCELFStreamer::ChangeSection(Section, Subsection);
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
109 void EmitInstruction(const MCInst &Inst,
110 const MCSubtargetInfo &STI) override {
111 EmitA64MappingSymbol();
112 MCELFStreamer::EmitInstruction(Inst, STI);
115 /// Emit a 32-bit value as an instruction. This is only used for the .inst
116 /// directive, EmitInstruction should be used in other cases.
117 void emitInst(uint32_t Inst) {
120 // We can't just use EmitIntValue here, as that will emit a data mapping
121 // symbol, and swap the endianness on big-endian systems (instructions are
122 // always little-endian).
123 for (unsigned I = 0; I < 4; ++I) {
124 Buffer[I] = uint8_t(Inst);
128 EmitA64MappingSymbol();
129 MCELFStreamer::EmitBytes(StringRef(Buffer, 4));
132 /// This is one of the functions used to emit data into an ELF section, so the
133 /// AArch64 streamer overrides it to add the appropriate mapping symbol ($d)
135 void EmitBytes(StringRef Data) override {
136 EmitDataMappingSymbol();
137 MCELFStreamer::EmitBytes(Data);
140 /// This is one of the functions used to emit data into an ELF section, so the
141 /// AArch64 streamer overrides it to add the appropriate mapping symbol ($d)
143 void EmitValueImpl(const MCExpr *Value, unsigned Size, SMLoc Loc) override {
144 EmitDataMappingSymbol();
145 MCELFStreamer::EmitValueImpl(Value, Size, Loc);
149 enum ElfMappingSymbol {
155 void EmitDataMappingSymbol() {
156 if (LastEMS == EMS_Data)
158 EmitMappingSymbol("$d");
162 void EmitA64MappingSymbol() {
163 if (LastEMS == EMS_A64)
165 EmitMappingSymbol("$x");
169 void EmitMappingSymbol(StringRef Name) {
170 auto *Symbol = cast<MCSymbolELF>(getContext().getOrCreateSymbol(
171 Name + "." + Twine(MappingSymbolCounter++)));
173 Symbol->setType(ELF::STT_NOTYPE);
174 Symbol->setBinding(ELF::STB_LOCAL);
175 Symbol->setExternal(false);
178 int64_t MappingSymbolCounter;
180 DenseMap<const MCSection *, ElfMappingSymbol> LastMappingSymbols;
181 ElfMappingSymbol LastEMS;
183 } // end anonymous namespace
185 AArch64ELFStreamer &AArch64TargetELFStreamer::getStreamer() {
186 return static_cast<AArch64ELFStreamer &>(Streamer);
189 void AArch64TargetELFStreamer::emitInst(uint32_t Inst) {
190 getStreamer().emitInst(Inst);
194 MCTargetStreamer *createAArch64AsmTargetStreamer(MCStreamer &S,
195 formatted_raw_ostream &OS,
196 MCInstPrinter *InstPrint,
198 return new AArch64TargetAsmStreamer(S, OS);
201 MCELFStreamer *createAArch64ELFStreamer(MCContext &Context, MCAsmBackend &TAB,
202 raw_pwrite_stream &OS,
203 MCCodeEmitter *Emitter, bool RelaxAll) {
204 AArch64ELFStreamer *S = new AArch64ELFStreamer(Context, TAB, OS, Emitter);
206 S->getAssembler().setRelaxAll(true);
211 createAArch64ObjectTargetStreamer(MCStreamer &S, const MCSubtargetInfo &STI) {
212 const Triple &TT = STI.getTargetTriple();
213 if (TT.isOSBinFormatELF())
214 return new AArch64TargetELFStreamer(S);