LLVM  10.0.0svn
AArch64ELFStreamer.cpp
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1 //===- lib/MC/AArch64ELFStreamer.cpp - ELF Object Output for AArch64 ------===//
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 // This file assembles .s files and emits AArch64 ELF .o object files. Different
10 // from generic ELF streamer in emitting mapping symbols ($x and $d) to delimit
11 // regions of data and code.
12 //
13 //===----------------------------------------------------------------------===//
14 
15 #include "AArch64TargetStreamer.h"
16 #include "AArch64WinCOFFStreamer.h"
17 #include "llvm/ADT/DenseMap.h"
18 #include "llvm/ADT/StringRef.h"
19 #include "llvm/ADT/Triple.h"
20 #include "llvm/ADT/Twine.h"
21 #include "llvm/BinaryFormat/ELF.h"
22 #include "llvm/MC/MCAsmBackend.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/MCObjectWriter.h"
30 #include "llvm/MC/MCSection.h"
31 #include "llvm/MC/MCStreamer.h"
33 #include "llvm/MC/MCSymbolELF.h"
35 #include "llvm/Support/Casting.h"
38 
39 using namespace llvm;
40 
41 namespace {
42 
43 class AArch64ELFStreamer;
44 
45 class AArch64TargetAsmStreamer : public AArch64TargetStreamer {
47 
48  void emitInst(uint32_t Inst) override;
49 
50 public:
51  AArch64TargetAsmStreamer(MCStreamer &S, formatted_raw_ostream &OS);
52 };
53 
54 AArch64TargetAsmStreamer::AArch64TargetAsmStreamer(MCStreamer &S,
56  : AArch64TargetStreamer(S), OS(OS) {}
57 
58 void AArch64TargetAsmStreamer::emitInst(uint32_t Inst) {
59  OS << "\t.inst\t0x" << Twine::utohexstr(Inst) << "\n";
60 }
61 
62 /// Extend the generic ELFStreamer class so that it can emit mapping symbols at
63 /// the appropriate points in the object files. These symbols are defined in the
64 /// AArch64 ELF ABI:
65 /// infocenter.arm.com/help/topic/com.arm.doc.ihi0056a/IHI0056A_aaelf64.pdf
66 ///
67 /// In brief: $x or $d should be emitted at the start of each contiguous region
68 /// of A64 code or data in a section. In practice, this emission does not rely
69 /// on explicit assembler directives but on inherent properties of the
70 /// directives doing the emission (e.g. ".byte" is data, "add x0, x0, x0" an
71 /// instruction).
72 ///
73 /// As a result this system is orthogonal to the DataRegion infrastructure used
74 /// by MachO. Beware!
75 class AArch64ELFStreamer : public MCELFStreamer {
76 public:
77  AArch64ELFStreamer(MCContext &Context, std::unique_ptr<MCAsmBackend> TAB,
78  std::unique_ptr<MCObjectWriter> OW,
79  std::unique_ptr<MCCodeEmitter> Emitter)
80  : MCELFStreamer(Context, std::move(TAB), std::move(OW),
81  std::move(Emitter)),
82  MappingSymbolCounter(0), LastEMS(EMS_None) {}
83 
84  void ChangeSection(MCSection *Section, const MCExpr *Subsection) override {
85  // We have to keep track of the mapping symbol state of any sections we
86  // use. Each one should start off as EMS_None, which is provided as the
87  // default constructor by DenseMap::lookup.
88  LastMappingSymbols[getPreviousSection().first] = LastEMS;
89  LastEMS = LastMappingSymbols.lookup(Section);
90 
91  MCELFStreamer::ChangeSection(Section, Subsection);
92  }
93 
94  // Reset state between object emissions
95  void reset() override {
96  MappingSymbolCounter = 0;
98  LastMappingSymbols.clear();
99  LastEMS = EMS_None;
100  }
101 
102  /// This function is the one used to emit instruction data into the ELF
103  /// streamer. We override it to add the appropriate mapping symbol if
104  /// necessary.
105  void EmitInstruction(const MCInst &Inst,
106  const MCSubtargetInfo &STI) override {
107  EmitA64MappingSymbol();
109  }
110 
111  /// Emit a 32-bit value as an instruction. This is only used for the .inst
112  /// directive, EmitInstruction should be used in other cases.
113  void emitInst(uint32_t Inst) {
114  char Buffer[4];
115 
116  // We can't just use EmitIntValue here, as that will emit a data mapping
117  // symbol, and swap the endianness on big-endian systems (instructions are
118  // always little-endian).
119  for (unsigned I = 0; I < 4; ++I) {
120  Buffer[I] = uint8_t(Inst);
121  Inst >>= 8;
122  }
123 
124  EmitA64MappingSymbol();
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.
131  void EmitBytes(StringRef Data) override {
132  EmitDataMappingSymbol();
134  }
135 
136  /// This is one of the functions used to emit data into an ELF section, so the
137  /// AArch64 streamer overrides it to add the appropriate mapping symbol ($d)
138  /// if necessary.
139  void EmitValueImpl(const MCExpr *Value, unsigned Size, SMLoc Loc) override {
140  EmitDataMappingSymbol();
141  MCELFStreamer::EmitValueImpl(Value, Size, Loc);
142  }
143 
144  void emitFill(const MCExpr &NumBytes, uint64_t FillValue,
145  SMLoc Loc) override {
146  EmitDataMappingSymbol();
147  MCObjectStreamer::emitFill(NumBytes, FillValue, Loc);
148  }
149 private:
150  enum ElfMappingSymbol {
151  EMS_None,
152  EMS_A64,
153  EMS_Data
154  };
155 
156  void EmitDataMappingSymbol() {
157  if (LastEMS == EMS_Data)
158  return;
159  EmitMappingSymbol("$d");
160  LastEMS = EMS_Data;
161  }
162 
163  void EmitA64MappingSymbol() {
164  if (LastEMS == EMS_A64)
165  return;
166  EmitMappingSymbol("$x");
167  LastEMS = EMS_A64;
168  }
169 
170  void EmitMappingSymbol(StringRef Name) {
171  auto *Symbol = cast<MCSymbolELF>(getContext().getOrCreateSymbol(
172  Name + "." + Twine(MappingSymbolCounter++)));
173  EmitLabel(Symbol);
174  Symbol->setType(ELF::STT_NOTYPE);
175  Symbol->setBinding(ELF::STB_LOCAL);
176  Symbol->setExternal(false);
177  }
178 
179  int64_t MappingSymbolCounter;
180 
182  ElfMappingSymbol LastEMS;
183 };
184 
185 } // end anonymous namespace
186 
187 namespace llvm {
188 
189 AArch64ELFStreamer &AArch64TargetELFStreamer::getStreamer() {
190  return static_cast<AArch64ELFStreamer &>(Streamer);
191 }
192 
193 void AArch64TargetELFStreamer::emitInst(uint32_t Inst) {
194  getStreamer().emitInst(Inst);
195 }
196 
199  MCInstPrinter *InstPrint,
200  bool isVerboseAsm) {
201  return new AArch64TargetAsmStreamer(S, OS);
202 }
203 
205  std::unique_ptr<MCAsmBackend> TAB,
206  std::unique_ptr<MCObjectWriter> OW,
207  std::unique_ptr<MCCodeEmitter> Emitter,
208  bool RelaxAll) {
209  AArch64ELFStreamer *S = new AArch64ELFStreamer(
210  Context, std::move(TAB), std::move(OW), std::move(Emitter));
211  if (RelaxAll)
212  S->getAssembler().setRelaxAll(true);
213  return S;
214 }
215 
216 } // end namespace llvm
Instances of this class represent a uniqued identifier for a section in the current translation unit...
Definition: MCSection.h:39
void EmitBytes(StringRef Data) override
Emit the bytes in Data into the output.
LLVMContext & Context
This class represents lattice values for constants.
Definition: AllocatorList.h:23
void reset() override
state management
Definition: MCELFStreamer.h:32
amdgpu Simplify well known AMD library false FunctionCallee Value const Twine & Name
formatted_raw_ostream - A raw_ostream that wraps another one and keeps track of line and column posit...
Target specific streamer interface.
Definition: MCStreamer.h:85
Definition: BitVector.h:937
Twine - A lightweight data structure for efficiently representing the concatenation of temporary valu...
Definition: Twine.h:80
Base class for the full range of assembler expressions which are needed for parsing.
Definition: MCExpr.h:35
Context object for machine code objects.
Definition: MCContext.h:65
void emitFill(const MCExpr &NumBytes, uint64_t FillValue, SMLoc Loc=SMLoc()) override
Emit Size bytes worth of the value specified by FillValue.
void EmitValueImpl(const MCExpr *Value, unsigned Size, SMLoc Loc=SMLoc()) override
Emit the expression Value into the output as a native integer of the given Size bytes.
MCELFStreamer * createAArch64ELFStreamer(MCContext &Context, std::unique_ptr< MCAsmBackend > TAB, std::unique_ptr< MCObjectWriter > OW, std::unique_ptr< MCCodeEmitter > Emitter, bool RelaxAll)
Instances of this class represent a single low-level machine instruction.
Definition: MCInst.h:158
void ChangeSection(MCSection *Section, const MCExpr *Subsection) override
Update streamer for a new active section.
Streaming machine code generation interface.
Definition: MCStreamer.h:190
void EmitInstruction(const MCInst &Inst, const MCSubtargetInfo &STI) override
Emit the given Instruction into the current section.
static Twine utohexstr(const uint64_t &Val)
Definition: Twine.h:387
This is an instance of a target assembly language printer that converts an MCInst to valid target ass...
Definition: MCInstPrinter.h:39
MCTargetStreamer * createAArch64AsmTargetStreamer(MCStreamer &S, formatted_raw_ostream &OS, MCInstPrinter *InstPrint, bool isVerboseAsm)
#define I(x, y, z)
Definition: MD5.cpp:58
Generic base class for all target subtargets.
uint32_t Size
Definition: Profile.cpp:46
LLVM Value Representation.
Definition: Value.h:73
StringRef - Represent a constant reference to a string, i.e.
Definition: StringRef.h:48
Represents a location in source code.
Definition: SMLoc.h:23