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/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
  35 using namespace llvm;
  36
  37 MCWasmStreamer::~MCWasmStreamer() = default; // anchor.
  38
  39 void 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
  52 void 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
  60 void 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
  72 void 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
  80 bool 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->setExported();
 126     break;
 127
 128   default:
 129     // unrecognized directive
 130     llvm_unreachable("unexpected MCSymbolAttr");
 131     return false;
 132   }
 133
 134   return true;
 135 }
 136
 137 void MCWasmStreamer::EmitCommonSymbol(MCSymbol *S, uint64_t Size,
 138                                       unsigned ByteAlignment) {
 139   llvm_unreachable("Common symbols are not yet implemented for Wasm");
 140 }
 141
 142 void MCWasmStreamer::emitELFSize(MCSymbol *Symbol, const MCExpr *Value) {
 143   cast<MCSymbolWasm>(Symbol)->setSize(Value);
 144 }
 145
 146 void MCWasmStreamer::EmitLocalCommonSymbol(MCSymbol *S, uint64_t Size,
 147                                            unsigned ByteAlignment) {
 148   llvm_unreachable("Local common symbols are not yet implemented for Wasm");
 149 }
 150
 151 void MCWasmStreamer::EmitValueImpl(const MCExpr *Value, unsigned Size,
 152                                    SMLoc Loc) {
 153   MCObjectStreamer::EmitValueImpl(Value, Size, Loc);
 154 }
 155
 156 void MCWasmStreamer::EmitValueToAlignment(unsigned ByteAlignment, int64_t Value,
 157                                           unsigned ValueSize,
 158                                           unsigned MaxBytesToEmit) {
 159   MCObjectStreamer::EmitValueToAlignment(ByteAlignment, Value, ValueSize,
 160                                          MaxBytesToEmit);
 161 }
 162
 163 void MCWasmStreamer::EmitIdent(StringRef IdentString) {
 164   // TODO(sbc): Add the ident section once we support mergable strings
 165   // sections in the object format
 166 }
 167
 168 void MCWasmStreamer::EmitInstToFragment(const MCInst &Inst,
 169                                         const MCSubtargetInfo &STI) {
 170   this->MCObjectStreamer::EmitInstToFragment(Inst, STI);
 171 }
 172
 173 void 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
 194 void MCWasmStreamer::FinishImpl() {
 195   EmitFrames(nullptr);
 196
 197   this->MCObjectStreamer::FinishImpl();
 198 }
 199
 200 MCStreamer *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
 212 void MCWasmStreamer::EmitThumbFunc(MCSymbol *Func) {
 213   llvm_unreachable("Generic Wasm doesn't support this directive");
 214 }
 215
 216 void MCWasmStreamer::EmitSymbolDesc(MCSymbol *Symbol, unsigned DescValue) {
 217   llvm_unreachable("Wasm doesn't support this directive");
 218 }
 219
 220 void 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
 226 void MCWasmStreamer::EmitTBSSSymbol(MCSection *Section, MCSymbol *Symbol,
 227                                     uint64_t Size, unsigned ByteAlignment) {
 228   llvm_unreachable("Wasm doesn't support this directive");
 229 }