MCWasmStreamer.cpp revision 360784 
1//===- lib/MC/MCWasmStreamer.cpp - Wasm Object Output ---------------------===//
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 Wasm .o object files.
10//
11//===----------------------------------------------------------------------===//
12
13#include "llvm/MC/MCWasmStreamer.h"
14#include "llvm/ADT/STLExtras.h"
15#include "llvm/ADT/SmallPtrSet.h"
16#include "llvm/MC/MCAsmBackend.h"
17#include "llvm/MC/MCAsmLayout.h"
18#include "llvm/MC/MCAssembler.h"
19#include "llvm/MC/MCCodeEmitter.h"
20#include "llvm/MC/MCContext.h"
21#include "llvm/MC/MCExpr.h"
22#include "llvm/MC/MCInst.h"
23#include "llvm/MC/MCObjectStreamer.h"
24#include "llvm/MC/MCSection.h"
25#include "llvm/MC/MCSectionWasm.h"
26#include "llvm/MC/MCSymbol.h"
27#include "llvm/MC/MCSymbolWasm.h"
28#include "llvm/MC/MCValue.h"
29#include "llvm/Support/Casting.h"
30#include "llvm/Support/Debug.h"
31#include "llvm/Support/ErrorHandling.h"
32#include "llvm/Support/TargetRegistry.h"
33#include "llvm/Support/raw_ostream.h"
34
35using namespace llvm;
36
37MCWasmStreamer::~MCWasmStreamer() = default; // anchor.
38
39void MCWasmStreamer::mergeFragment(MCDataFragment *DF, MCDataFragment *EF) {
40  flushPendingLabels(DF, DF->getContents().size());
41
42  for (unsigned I = 0, E = EF->getFixups().size(); I != E; ++I) {
43    EF->getFixups()[I].setOffset(EF->getFixups()[I].getOffset() +
44                                 DF->getContents().size());
45    DF->getFixups().push_back(EF->getFixups()[I]);
46  }
47  if (DF->getSubtargetInfo() == nullptr && EF->getSubtargetInfo())
48    DF->setHasInstructions(*EF->getSubtargetInfo());
49  DF->getContents().append(EF->getContents().begin(), EF->getContents().end());
50}
51
52void MCWasmStreamer::EmitAssemblerFlag(MCAssemblerFlag Flag) {
53  // Let the target do whatever target specific stuff it needs to do.
54  getAssembler().getBackend().handleAssemblerFlag(Flag);
55
56  // Do any generic stuff we need to do.
57  llvm_unreachable("invalid assembler flag!");
58}
59
60void MCWasmStreamer::ChangeSection(MCSection *Section,
61                                   const MCExpr *Subsection) {
62  MCAssembler &Asm = getAssembler();
63  auto *SectionWasm = cast<MCSectionWasm>(Section);
64  const MCSymbol *Grp = SectionWasm->getGroup();
65  if (Grp)
66    Asm.registerSymbol(*Grp);
67
68  this->MCObjectStreamer::ChangeSection(Section, Subsection);
69  Asm.registerSymbol(*Section->getBeginSymbol());
70}
71
72void MCWasmStreamer::EmitWeakReference(MCSymbol *Alias,
73                                       const MCSymbol *Symbol) {
74  getAssembler().registerSymbol(*Symbol);
75  const MCExpr *Value = MCSymbolRefExpr::create(
76      Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext());
77  Alias->setVariableValue(Value);
78}
79
80bool MCWasmStreamer::EmitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
81  assert(Attribute != MCSA_IndirectSymbol && "indirect symbols not supported");
82
83  auto *Symbol = cast<MCSymbolWasm>(S);
84
85  // Adding a symbol attribute always introduces the symbol; note that an
86  // important side effect of calling registerSymbol here is to register the
87  // symbol with the assembler.
88  getAssembler().registerSymbol(*Symbol);
89
90  switch (Attribute) {
91  case MCSA_LazyReference:
92  case MCSA_Reference:
93  case MCSA_SymbolResolver:
94  case MCSA_PrivateExtern:
95  case MCSA_WeakDefinition:
96  case MCSA_WeakDefAutoPrivate:
97  case MCSA_Invalid:
98  case MCSA_IndirectSymbol:
99  case MCSA_Protected:
100    return false;
101
102  case MCSA_Hidden:
103    Symbol->setHidden(true);
104    break;
105
106  case MCSA_Weak:
107  case MCSA_WeakReference:
108    Symbol->setWeak(true);
109    Symbol->setExternal(true);
110    break;
111
112  case MCSA_Global:
113    Symbol->setExternal(true);
114    break;
115
116  case MCSA_ELF_TypeFunction:
117    Symbol->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
118    break;
119
120  case MCSA_ELF_TypeObject:
121  case MCSA_Cold:
122    break;
123
124  case MCSA_NoDeadStrip:
125    Symbol->setNoStrip();
126    break;
127
128  default:
129    // unrecognized directive
130    llvm_unreachable("unexpected MCSymbolAttr");
131    return false;
132  }
133
134  return true;
135}
136
137void MCWasmStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
138                                      unsigned ByteAlignment) {
139  llvm_unreachable("Common symbols are not yet implemented for Wasm");
140}
141
142void MCWasmStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
143  cast<MCSymbolWasm>(Symbol)->setSize(Value);
144}
145
146void MCWasmStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
147                                           unsigned ByteAlignment) {
148  llvm_unreachable("Local common symbols are not yet implemented for Wasm");
149}
150
151void MCWasmStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
152                                   SMLoc Loc) {
153  MCObjectStreamer::EmitValueImpl(Value, Size, Loc);
154}
155
156void MCWasmStreamer::EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
157                                          unsigned ValueSize,
158                                          unsigned MaxBytesToEmit) {
159  MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value, ValueSize,
160                                         MaxBytesToEmit);
161}
162
163void MCWasmStreamer::EmitIdent(StringRef IdentString) {
164  // TODO(sbc): Add the ident section once we support mergable strings
165  // sections in the object format
166}
167
168void MCWasmStreamer::EmitInstToFragment(const MCInst &Inst,
169                                        const MCSubtargetInfo &STI) {
170  this->MCObjectStreamer::EmitInstToFragment(Inst, STI);
171}
172
173void MCWasmStreamer::EmitInstToData(const MCInst &Inst,
174                                    const MCSubtargetInfo &STI) {
175  MCAssembler &Assembler = getAssembler();
176  SmallVector<MCFixup, 4> Fixups;
177  SmallString<256> Code;
178  raw_svector_ostream VecOS(Code);
179  Assembler.getEmitter().encodeInstruction(Inst, VecOS, Fixups, STI);
180
181  // Append the encoded instruction to the current data fragment (or create a
182  // new such fragment if the current fragment is not a data fragment).
183  MCDataFragment *DF = getOrCreateDataFragment();
184
185  // Add the fixups and data.
186  for (unsigned I = 0, E = Fixups.size(); I != E; ++I) {
187    Fixups[I].setOffset(Fixups[I].getOffset() + DF->getContents().size());
188    DF->getFixups().push_back(Fixups[I]);
189  }
190  DF->setHasInstructions(STI);
191  DF->getContents().append(Code.begin(), Code.end());
192}
193
194void MCWasmStreamer::FinishImpl() {
195  EmitFrames(nullptr);
196
197  this->MCObjectStreamer::FinishImpl();
198}
199
200MCStreamer *llvm::createWasmStreamer(MCContext &Context,
201                                     std::unique_ptr<MCAsmBackend> &&MAB,
202                                     std::unique_ptr<MCObjectWriter> &&OW,
203                                     std::unique_ptr<MCCodeEmitter> &&CE,
204                                     bool RelaxAll) {
205  MCWasmStreamer *S =
206      new MCWasmStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
207  if (RelaxAll)
208    S->getAssembler().setRelaxAll(true);
209  return S;
210}
211
212void MCWasmStreamer::EmitThumbFunc(MCSymbol *Func) {
213  llvm_unreachable("Generic Wasm doesn't support this directive");
214}
215
216void MCWasmStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
217  llvm_unreachable("Wasm doesn't support this directive");
218}
219
220void MCWasmStreamer::EmitZerofill(MCSection *Section, MCSymbol *Symbol,
221                                  uint64_t Size, unsigned ByteAlignment,
222                                  SMLoc Loc) {
223  llvm_unreachable("Wasm doesn't support this directive");
224}
225
226void MCWasmStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
227                                    uint64_t Size, unsigned ByteAlignment) {
228  llvm_unreachable("Wasm doesn't support this directive");
229}
230