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::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
  55 void 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
  65 void 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
  76 void 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
  84 void 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
  96 void 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
 104 bool 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
 166 void MCWasmStreamer::emitCommonSymbol(MCSymbol *S, uint64_t Size,
 167                                       Align ByteAlignment) {
 168   llvm_unreachable("Common symbols are not yet implemented for Wasm");
 169 }
 170
 171 void MCWasmStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
 172   cast<MCSymbolWasm>(Symbol)->setSize(Value);
 173 }
 174
 175 void MCWasmStreamer::emitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
 176                                            Align ByteAlignment) {
 177   llvm_unreachable("Local common symbols are not yet implemented for Wasm");
 178 }
 179
 180 void MCWasmStreamer::emitIdent(StringRef IdentString) {
 181   // TODO(sbc): Add the ident section once we support mergable strings
 182   // sections in the object format
 183 }
 184
 185 void 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
 194 void 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
 217 void MCWasmStreamer::finishImpl() {
 218   emitFrames(nullptr);
 219
 220   this->MCObjectStreamer::finishImpl();
 221 }
 222
 223 void 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
 256 void MCWasmStreamer::emitThumbFunc(MCSymbol *Func) {
 257   llvm_unreachable("Generic Wasm doesn't support this directive");
 258 }
 259
 260 void MCWasmStreamer::emitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 261   llvm_unreachable("Wasm doesn't support this directive");
 262 }
 263
 264 void 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
 270 void MCWasmStreamer::emitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
 271                                     uint64_t Size, Align ByteAlignment) {
 272   llvm_unreachable("Wasm doesn't support this directive");
 273 }
 274
 275 MCStreamer *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 }