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/SmallString.h"
15#include "llvm/ADT/SmallVector.h"
16#include "llvm/MC/MCAsmBackend.h"
17#include "llvm/MC/MCAssembler.h"
18#include "llvm/MC/MCCodeEmitter.h"
19#include "llvm/MC/MCExpr.h"
20#include "llvm/MC/MCFixup.h"
21#include "llvm/MC/MCFragment.h"
22#include "llvm/MC/MCObjectStreamer.h"
23#include "llvm/MC/MCSection.h"
24#include "llvm/MC/MCSectionWasm.h"
25#include "llvm/MC/MCSymbol.h"
26#include "llvm/MC/MCSymbolWasm.h"
27#include "llvm/MC/TargetRegistry.h"
28#include "llvm/Support/Casting.h"
29#include "llvm/Support/ErrorHandling.h"
30#include "llvm/Support/raw_ostream.h"
31
32namespace llvm {
33class MCContext;
34class MCStreamer;
35class MCSubtargetInfo;
36} // namespace llvm
37
38using namespace llvm;
39
40MCWasmStreamer::~MCWasmStreamer() = default; // anchor.
41
42void MCWasmStreamer::mergeFragment(MCDataFragment *DF, MCDataFragment *EF) {
43  flushPendingLabels(DF, DF->getContents().size());
44
45  for (unsigned I = 0, E = EF->getFixups().size(); I != E; ++I) {
46    EF->getFixups()[I].setOffset(EF->getFixups()[I].getOffset() +
47                                 DF->getContents().size());
48    DF->getFixups().push_back(EF->getFixups()[I]);
49  }
50  if (DF->getSubtargetInfo() == nullptr && EF->getSubtargetInfo())
51    DF->setHasInstructions(*EF->getSubtargetInfo());
52  DF->getContents().append(EF->getContents().begin(), EF->getContents().end());
53}
54
55void MCWasmStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
56  auto *Symbol = cast<MCSymbolWasm>(S);
57  MCObjectStreamer::emitLabel(Symbol, Loc);
58
59  const MCSectionWasm &Section =
60      static_cast<const MCSectionWasm &>(*getCurrentSectionOnly());
61  if (Section.getSegmentFlags() & wasm::WASM_SEG_FLAG_TLS)
62    Symbol->setTLS();
63}
64
65void MCWasmStreamer::emitLabelAtPos(MCSymbol *S, SMLoc Loc, MCFragment *F,
66                                    uint64_t Offset) {
67  auto *Symbol = cast<MCSymbolWasm>(S);
68  MCObjectStreamer::emitLabelAtPos(Symbol, Loc, F, Offset);
69
70  const MCSectionWasm &Section =
71      static_cast<const MCSectionWasm &>(*getCurrentSectionOnly());
72  if (Section.getSegmentFlags() & wasm::WASM_SEG_FLAG_TLS)
73    Symbol->setTLS();
74}
75
76void MCWasmStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
77  // Let the target do whatever target specific stuff it needs to do.
78  getAssembler().getBackend().handleAssemblerFlag(Flag);
79
80  // Do any generic stuff we need to do.
81  llvm_unreachable("invalid assembler flag!");
82}
83
84void MCWasmStreamer::changeSection(MCSection *Section,
85                                   const MCExpr *Subsection) {
86  MCAssembler &Asm = getAssembler();
87  auto *SectionWasm = cast<MCSectionWasm>(Section);
88  const MCSymbol *Grp = SectionWasm->getGroup();
89  if (Grp)
90    Asm.registerSymbol(*Grp);
91
92  this->MCObjectStreamer::changeSection(Section, Subsection);
93  Asm.registerSymbol(*Section->getBeginSymbol());
94}
95
96void MCWasmStreamer::emitWeakReference(MCSymbol *Alias,
97                                       const MCSymbol *Symbol) {
98  getAssembler().registerSymbol(*Symbol);
99  const MCExpr *Value = MCSymbolRefExpr::create(
100      Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext());
101  Alias->setVariableValue(Value);
102}
103
104bool MCWasmStreamer::emitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
105  assert(Attribute != MCSA_IndirectSymbol && "indirect symbols not supported");
106
107  auto *Symbol = cast<MCSymbolWasm>(S);
108
109  // Adding a symbol attribute always introduces the symbol; note that an
110  // important side effect of calling registerSymbol here is to register the
111  // symbol with the assembler.
112  getAssembler().registerSymbol(*Symbol);
113
114  switch (Attribute) {
115  case MCSA_LazyReference:
116  case MCSA_Reference:
117  case MCSA_SymbolResolver:
118  case MCSA_PrivateExtern:
119  case MCSA_WeakDefinition:
120  case MCSA_WeakDefAutoPrivate:
121  case MCSA_Invalid:
122  case MCSA_IndirectSymbol:
123  case MCSA_Protected:
124  case MCSA_Exported:
125    return false;
126
127  case MCSA_Hidden:
128    Symbol->setHidden(true);
129    break;
130
131  case MCSA_Weak:
132  case MCSA_WeakReference:
133    Symbol->setWeak(true);
134    Symbol->setExternal(true);
135    break;
136
137  case MCSA_Global:
138    Symbol->setExternal(true);
139    break;
140
141  case MCSA_ELF_TypeFunction:
142    Symbol->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
143    break;
144
145  case MCSA_ELF_TypeTLS:
146    Symbol->setTLS();
147    break;
148
149  case MCSA_ELF_TypeObject:
150  case MCSA_Cold:
151    break;
152
153  case MCSA_NoDeadStrip:
154    Symbol->setNoStrip();
155    break;
156
157  default:
158    // unrecognized directive
159    llvm_unreachable("unexpected MCSymbolAttr");
160    return false;
161  }
162
163  return true;
164}
165
166void MCWasmStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
167                                      Align ByteAlignment) {
168  llvm_unreachable("Common symbols are not yet implemented for Wasm");
169}
170
171void MCWasmStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
172  cast<MCSymbolWasm>(Symbol)->setSize(Value);
173}
174
175void MCWasmStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
176                                           Align ByteAlignment) {
177  llvm_unreachable("Local common symbols are not yet implemented for Wasm");
178}
179
180void MCWasmStreamer::emitIdent(StringRef IdentString) {
181  // TODO(sbc): Add the ident section once we support mergable strings
182  // sections in the object format
183}
184
185void MCWasmStreamer::emitInstToFragment(const MCInst &Inst,
186                                        const MCSubtargetInfo &STI) {
187  this->MCObjectStreamer::emitInstToFragment(Inst, STI);
188  MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
189
190  for (auto &Fixup : F.getFixups())
191    fixSymbolsInTLSFixups(Fixup.getValue());
192}
193
194void MCWasmStreamer::emitInstToData(const MCInst &Inst,
195                                    const MCSubtargetInfo &STI) {
196  MCAssembler &Assembler = getAssembler();
197  SmallVector<MCFixup, 4> Fixups;
198  SmallString<256> Code;
199  Assembler.getEmitter().encodeInstruction(Inst, Code, Fixups, STI);
200
201  for (auto &Fixup : Fixups)
202    fixSymbolsInTLSFixups(Fixup.getValue());
203
204  // Append the encoded instruction to the current data fragment (or create a
205  // new such fragment if the current fragment is not a data fragment).
206  MCDataFragment *DF = getOrCreateDataFragment();
207
208  // Add the fixups and data.
209  for (unsigned I = 0, E = Fixups.size(); I != E; ++I) {
210    Fixups[I].setOffset(Fixups[I].getOffset() + DF->getContents().size());
211    DF->getFixups().push_back(Fixups[I]);
212  }
213  DF->setHasInstructions(STI);
214  DF->getContents().append(Code.begin(), Code.end());
215}
216
217void MCWasmStreamer::finishImpl() {
218  emitFrames(nullptr);
219
220  this->MCObjectStreamer::finishImpl();
221}
222
223void MCWasmStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
224  switch (expr->getKind()) {
225  case MCExpr::Target:
226  case MCExpr::Constant:
227    break;
228
229  case MCExpr::Binary: {
230    const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
231    fixSymbolsInTLSFixups(be->getLHS());
232    fixSymbolsInTLSFixups(be->getRHS());
233    break;
234  }
235
236  case MCExpr::SymbolRef: {
237    const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
238    switch (symRef.getKind()) {
239    case MCSymbolRefExpr::VK_WASM_TLSREL:
240    case MCSymbolRefExpr::VK_WASM_GOT_TLS:
241      getAssembler().registerSymbol(symRef.getSymbol());
242      cast<MCSymbolWasm>(symRef.getSymbol()).setTLS();
243      break;
244    default:
245      break;
246    }
247    break;
248  }
249
250  case MCExpr::Unary:
251    fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
252    break;
253  }
254}
255
256void MCWasmStreamer::emitThumbFunc(MCSymbol *Func) {
257  llvm_unreachable("Generic Wasm doesn't support this directive");
258}
259
260void MCWasmStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
261  llvm_unreachable("Wasm doesn't support this directive");
262}
263
264void MCWasmStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
265                                  uint64_t Size, Align ByteAlignment,
266                                  SMLoc Loc) {
267  llvm_unreachable("Wasm doesn't support this directive");
268}
269
270void MCWasmStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
271                                    uint64_t Size, Align ByteAlignment) {
272  llvm_unreachable("Wasm doesn't support this directive");
273}
274
275MCStreamer *llvm::createWasmStreamer(MCContext &Context,
276                                     std::unique_ptr<MCAsmBackend> &&MAB,
277                                     std::unique_ptr<MCObjectWriter> &&OW,
278                                     std::unique_ptr<MCCodeEmitter> &&CE,
279                                     bool RelaxAll) {
280  MCWasmStreamer *S =
281      new MCWasmStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
282  if (RelaxAll)
283    S->getAssembler().setRelaxAll(true);
284  return S;
285}
286