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 /// Extend the generic ELFStreamer class so that it can emit mapping symbols at
64 /// the appropriate points in the object files. These symbols are defined in the
66 /// infocenter.arm.com/help/topic/com.arm.doc.ihi0056a/IHI0056A_aaelf64.pdf
68 /// In brief: $x or $d should be emitted at the start of each contiguous region
69 /// of A64 code or data in a section. In practice, this emission does not rely
70 /// on explicit assembler directives but on inherent properties of the
71 /// directives doing the emission (e.g. ".byte" is data, "add x0, x0, x0" an
74 /// As a result this system is orthogonal to the DataRegion infrastructure used
76 class AArch64ELFStreamer : public MCELFStreamer {
78 AArch64ELFStreamer(MCContext &Context, std::unique_ptr<MCAsmBackend> TAB,
79 std::unique_ptr<MCObjectWriter> OW,
80 std::unique_ptr<MCCodeEmitter> Emitter)
81 : MCELFStreamer(Context, std::move(TAB), std::move(OW),
83 MappingSymbolCounter(0), LastEMS(EMS_None) {}
85 void ChangeSection(MCSection *Section, const MCExpr *Subsection) override {
86 // We have to keep track of the mapping symbol state of any sections we
87 // use. Each one should start off as EMS_None, which is provided as the
88 // default constructor by DenseMap::lookup.
89 LastMappingSymbols[getPreviousSection().first] = LastEMS;
90 LastEMS = LastMappingSymbols.lookup(Section);
92 MCELFStreamer::ChangeSection(Section, Subsection);
95 // Reset state between object emissions
96 void reset() override {
97 MappingSymbolCounter = 0;
98 MCELFStreamer::reset();
99 LastMappingSymbols.clear();
103 /// This function is the one used to emit instruction data into the ELF
104 /// streamer. We override it to add the appropriate mapping symbol if
106 void EmitInstruction(const MCInst &Inst, const MCSubtargetInfo &STI,
108 EmitA64MappingSymbol();
109 MCELFStreamer::EmitInstruction(Inst, STI);
112 /// Emit a 32-bit value as an instruction. This is only used for the .inst
113 /// directive, EmitInstruction should be used in other cases.
114 void emitInst(uint32_t Inst) {
117 // We can't just use EmitIntValue here, as that will emit a data mapping
118 // symbol, and swap the endianness on big-endian systems (instructions are
119 // always little-endian).
120 for (unsigned I = 0; I < 4; ++I) {
121 Buffer[I] = uint8_t(Inst);
125 EmitA64MappingSymbol();
126 MCELFStreamer::EmitBytes(StringRef(Buffer, 4));
129 /// This is one of the functions used to emit data into an ELF section, so the
130 /// AArch64 streamer overrides it to add the appropriate mapping symbol ($d)
132 void EmitBytes(StringRef Data) override {
133 EmitDataMappingSymbol();
134 MCELFStreamer::EmitBytes(Data);
137 /// This is one of the functions used to emit data into an ELF section, so the
138 /// AArch64 streamer overrides it to add the appropriate mapping symbol ($d)
140 void EmitValueImpl(const MCExpr *Value, unsigned Size, SMLoc Loc) override {
141 EmitDataMappingSymbol();
142 MCELFStreamer::EmitValueImpl(Value, Size, Loc);
145 void emitFill(const MCExpr &NumBytes, uint64_t FillValue,
146 SMLoc Loc) override {
147 EmitDataMappingSymbol();
148 MCObjectStreamer::emitFill(NumBytes, FillValue, Loc);
151 enum ElfMappingSymbol {
157 void EmitDataMappingSymbol() {
158 if (LastEMS == EMS_Data)
160 EmitMappingSymbol("$d");
164 void EmitA64MappingSymbol() {
165 if (LastEMS == EMS_A64)
167 EmitMappingSymbol("$x");
171 void EmitMappingSymbol(StringRef Name) {
172 auto *Symbol = cast<MCSymbolELF>(getContext().getOrCreateSymbol(
173 Name + "." + Twine(MappingSymbolCounter++)));
175 Symbol->setType(ELF::STT_NOTYPE);
176 Symbol->setBinding(ELF::STB_LOCAL);
177 Symbol->setExternal(false);
180 int64_t MappingSymbolCounter;
182 DenseMap<const MCSection *, ElfMappingSymbol> LastMappingSymbols;
183 ElfMappingSymbol LastEMS;
186 } // end anonymous namespace
190 AArch64ELFStreamer &AArch64TargetELFStreamer::getStreamer() {
191 return static_cast<AArch64ELFStreamer &>(Streamer);
194 void AArch64TargetELFStreamer::emitInst(uint32_t Inst) {
195 getStreamer().emitInst(Inst);
198 MCTargetStreamer *createAArch64AsmTargetStreamer(MCStreamer &S,
199 formatted_raw_ostream &OS,
200 MCInstPrinter *InstPrint,
202 return new AArch64TargetAsmStreamer(S, OS);
205 MCELFStreamer *createAArch64ELFStreamer(MCContext &Context,
206 std::unique_ptr<MCAsmBackend> TAB,
207 std::unique_ptr<MCObjectWriter> OW,
208 std::unique_ptr<MCCodeEmitter> Emitter,
210 AArch64ELFStreamer *S = new AArch64ELFStreamer(
211 Context, std::move(TAB), std::move(OW), std::move(Emitter));
213 S->getAssembler().setRelaxAll(true);
217 } // end namespace llvm