llvm/lib/MC/MCWasmStreamer.cpp

   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
  32 namespace llvm {
  33 class MCContext;
  34 class MCStreamer;
  35 class MCSubtargetInfo;
  36 } // namespace llvm
  37
  38 using namespace llvm;
  39
  40 MCWasmStreamer::~MCWasmStreamer() = default; // anchor.
  41
  42 void MCWasmStreamer::emitLabel(MCSymbol *S, SMLoc Loc) {
  43   auto *Symbol = cast<MCSymbolWasm>(S);
  44   MCObjectStreamer::emitLabel(Symbol, Loc);
  45
  46   const MCSectionWasm &Section =
  47       static_cast<const MCSectionWasm &>(*getCurrentSectionOnly());
  48   if (Section.getSegmentFlags() & wasm::WASM_SEG_FLAG_TLS)
  49     Symbol->setTLS();
  50 }
  51
  52 void MCWasmStreamer::emitLabelAtPos(MCSymbol *S, SMLoc Loc, MCDataFragment &F,
  53                                     uint64_t Offset) {
  54   auto *Symbol = cast<MCSymbolWasm>(S);
  55   MCObjectStreamer::emitLabelAtPos(Symbol, Loc, F, Offset);
  56
  57   const MCSectionWasm &Section =
  58       static_cast<const MCSectionWasm &>(*getCurrentSectionOnly());
  59   if (Section.getSegmentFlags() & wasm::WASM_SEG_FLAG_TLS)
  60     Symbol->setTLS();
  61 }
  62
  63 void MCWasmStreamer::emitAssemblerFlag(MCAssemblerFlag Flag) {
  64   // Let the target do whatever target specific stuff it needs to do.
  65   getAssembler().getBackend().handleAssemblerFlag(Flag);
  66
  67   // Do any generic stuff we need to do.
  68   llvm_unreachable("invalid assembler flag!");
  69 }
  70
  71 void MCWasmStreamer::changeSection(MCSection *Section, uint32_t Subsection) {
  72   MCAssembler &Asm = getAssembler();
  73   auto *SectionWasm = cast<MCSectionWasm>(Section);
  74   const MCSymbol *Grp = SectionWasm->getGroup();
  75   if (Grp)
  76     Asm.registerSymbol(*Grp);
  77
  78   this->MCObjectStreamer::changeSection(Section, Subsection);
  79   Asm.registerSymbol(*Section->getBeginSymbol());
  80 }
  81
  82 void MCWasmStreamer::emitWeakReference(MCSymbol *Alias,
  83                                        const MCSymbol *Symbol) {
  84   getAssembler().registerSymbol(*Symbol);
  85   const MCExpr *Value = MCSymbolRefExpr::create(
  86       Symbol, MCSymbolRefExpr::VK_WEAKREF, getContext());
  87   Alias->setVariableValue(Value);
  88 }
  89
  90 bool MCWasmStreamer::emitSymbolAttribute(MCSymbol *S, MCSymbolAttr Attribute) {
  91   assert(Attribute != MCSA_IndirectSymbol && "indirect symbols not supported");
  92
  93   auto *Symbol = cast<MCSymbolWasm>(S);
  94
  95   // Adding a symbol attribute always introduces the symbol; note that an
  96   // important side effect of calling registerSymbol here is to register the
  97   // symbol with the assembler.
  98   getAssembler().registerSymbol(*Symbol);
  99
 100   switch (Attribute) {
 101   case MCSA_LazyReference:
 102   case MCSA_Reference:
 103   case MCSA_SymbolResolver:
 104   case MCSA_PrivateExtern:
 105   case MCSA_WeakDefinition:
 106   case MCSA_WeakDefAutoPrivate:
 107   case MCSA_Invalid:
 108   case MCSA_IndirectSymbol:
 109   case MCSA_Protected:
 110   case MCSA_Exported:
 111     return false;
 112
 113   case MCSA_Hidden:
 114     Symbol->setHidden(true);
 115     break;
 116
 117   case MCSA_Weak:
 118   case MCSA_WeakReference:
 119     Symbol->setWeak(true);
 120     Symbol->setExternal(true);
 121     break;
 122
 123   case MCSA_Global:
 124     Symbol->setExternal(true);
 125     break;
 126
 127   case MCSA_ELF_TypeFunction:
 128     Symbol->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
 129     break;
 130
 131   case MCSA_ELF_TypeTLS:
 132     Symbol->setTLS();
 133     break;
 134
 135   case MCSA_ELF_TypeObject:
 136   case MCSA_Cold:
 137     break;
 138
 139   case MCSA_NoDeadStrip:
 140     Symbol->setNoStrip();
 141     break;
 142
 143   default:
 144     // unrecognized directive
 145     llvm_unreachable("unexpected MCSymbolAttr");
 146     return false;
 147   }
 148
 149   return true;
 150 }
 151
 152 void MCWasmStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
 153                                       Align ByteAlignment) {
 154   llvm_unreachable("Common symbols are not yet implemented for Wasm");
 155 }
 156
 157 void MCWasmStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
 158   cast<MCSymbolWasm>(Symbol)->setSize(Value);
 159 }
 160
 161 void MCWasmStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
 162                                            Align ByteAlignment) {
 163   llvm_unreachable("Local common symbols are not yet implemented for Wasm");
 164 }
 165
 166 void MCWasmStreamer::emitIdent(StringRef IdentString) {
 167   // TODO(sbc): Add the ident section once we support mergable strings
 168   // sections in the object format
 169 }
 170
 171 void MCWasmStreamer::emitInstToFragment(const MCInst &Inst,
 172                                         const MCSubtargetInfo &STI) {
 173   this->MCObjectStreamer::emitInstToFragment(Inst, STI);
 174   MCRelaxableFragment &F = *cast<MCRelaxableFragment>(getCurrentFragment());
 175
 176   for (auto &Fixup : F.getFixups())
 177     fixSymbolsInTLSFixups(Fixup.getValue());
 178 }
 179
 180 void MCWasmStreamer::emitInstToData(const MCInst &Inst,
 181                                     const MCSubtargetInfo &STI) {
 182   MCAssembler &Assembler = getAssembler();
 183   SmallVector<MCFixup, 4> Fixups;
 184   SmallString<256> Code;
 185   Assembler.getEmitter().encodeInstruction(Inst, Code, Fixups, STI);
 186
 187   for (auto &Fixup : Fixups)
 188     fixSymbolsInTLSFixups(Fixup.getValue());
 189
 190   // Append the encoded instruction to the current data fragment (or create a
 191   // new such fragment if the current fragment is not a data fragment).
 192   MCDataFragment *DF = getOrCreateDataFragment();
 193
 194   // Add the fixups and data.
 195   for (unsigned I = 0, E = Fixups.size(); I != E; ++I) {
 196     Fixups[I].setOffset(Fixups[I].getOffset() + DF->getContents().size());
 197     DF->getFixups().push_back(Fixups[I]);
 198   }
 199   DF->setHasInstructions(STI);
 200   DF->getContents().append(Code.begin(), Code.end());
 201 }
 202
 203 void MCWasmStreamer::finishImpl() {
 204   emitFrames(nullptr);
 205
 206   this->MCObjectStreamer::finishImpl();
 207 }
 208
 209 void MCWasmStreamer::fixSymbolsInTLSFixups(const MCExpr *expr) {
 210   switch (expr->getKind()) {
 211   case MCExpr::Target:
 212   case MCExpr::Constant:
 213     break;
 214
 215   case MCExpr::Binary: {
 216     const MCBinaryExpr *be = cast<MCBinaryExpr>(expr);
 217     fixSymbolsInTLSFixups(be->getLHS());
 218     fixSymbolsInTLSFixups(be->getRHS());
 219     break;
 220   }
 221
 222   case MCExpr::SymbolRef: {
 223     const MCSymbolRefExpr &symRef = *cast<MCSymbolRefExpr>(expr);
 224     switch (symRef.getKind()) {
 225     case MCSymbolRefExpr::VK_WASM_TLSREL:
 226     case MCSymbolRefExpr::VK_WASM_GOT_TLS:
 227       getAssembler().registerSymbol(symRef.getSymbol());
 228       cast<MCSymbolWasm>(symRef.getSymbol()).setTLS();
 229       break;
 230     default:
 231       break;
 232     }
 233     break;
 234   }
 235
 236   case MCExpr::Unary:
 237     fixSymbolsInTLSFixups(cast<MCUnaryExpr>(expr)->getSubExpr());
 238     break;
 239   }
 240 }
 241
 242 void MCWasmStreamer::emitThumbFunc(MCSymbol *Func) {
 243   llvm_unreachable("Generic Wasm doesn't support this directive");
 244 }
 245
 246 void MCWasmStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 247   llvm_unreachable("Wasm doesn't support this directive");
 248 }
 249
 250 void MCWasmStreamer::emitZerofill(MCSection *Section, MCSymbol *Symbol,
 251                                   uint64_t Size, Align ByteAlignment,
 252                                   SMLoc Loc) {
 253   llvm_unreachable("Wasm doesn't support this directive");
 254 }
 255
 256 void MCWasmStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
 257                                     uint64_t Size, Align ByteAlignment) {
 258   llvm_unreachable("Wasm doesn't support this directive");
 259 }
 260
 261 MCStreamer *llvm::createWasmStreamer(MCContext &Context,
 262                                      std::unique_ptr<MCAsmBackend> &&MAB,
 263                                      std::unique_ptr<MCObjectWriter> &&OW,
 264                                      std::unique_ptr<MCCodeEmitter> &&CE) {
 265   MCWasmStreamer *S =
 266       new MCWasmStreamer(Context, std::move(MAB), std::move(OW), std::move(CE));
 267   return S;
 268 }