lib/Target/WebAssembly/WebAssemblyAsmPrinter.cpp

   1 //===-- WebAssemblyAsmPrinter.cpp - WebAssembly LLVM assembly writer ------===//
   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 /// \file
  10 /// This file contains a printer that converts from our internal
  11 /// representation of machine-dependent LLVM code to the WebAssembly assembly
  12 /// language.
  13 ///
  14 //===----------------------------------------------------------------------===//
  15
  16 #include "WebAssemblyAsmPrinter.h"
  17 #include "InstPrinter/WebAssemblyInstPrinter.h"
  18 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
  19 #include "MCTargetDesc/WebAssemblyTargetStreamer.h"
  20 #include "WebAssembly.h"
  21 #include "WebAssemblyMCInstLower.h"
  22 #include "WebAssemblyMachineFunctionInfo.h"
  23 #include "WebAssemblyRegisterInfo.h"
  24 #include "llvm/ADT/SmallSet.h"
  25 #include "llvm/ADT/StringExtras.h"
  26 #include "llvm/CodeGen/Analysis.h"
  27 #include "llvm/CodeGen/AsmPrinter.h"
  28 #include "llvm/CodeGen/MachineConstantPool.h"
  29 #include "llvm/CodeGen/MachineInstr.h"
  30 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
  31 #include "llvm/IR/DataLayout.h"
  32 #include "llvm/IR/DebugInfoMetadata.h"
  33 #include "llvm/IR/GlobalVariable.h"
  34 #include "llvm/MC/MCContext.h"
  35 #include "llvm/MC/MCSectionWasm.h"
  36 #include "llvm/MC/MCStreamer.h"
  37 #include "llvm/MC/MCSymbol.h"
  38 #include "llvm/MC/MCSymbolWasm.h"
  39 #include "llvm/Support/Debug.h"
  40 #include "llvm/Support/TargetRegistry.h"
  41 #include "llvm/Support/raw_ostream.h"
  42 using namespace llvm;
  43
  44 #define DEBUG_TYPE "asm-printer"
  45
  46 extern cl::opt<bool> WasmKeepRegisters;
  47
  48 //===----------------------------------------------------------------------===//
  49 // Helpers.
  50 //===----------------------------------------------------------------------===//
  51
  52 MVT WebAssemblyAsmPrinter::getRegType(unsigned RegNo) const {
  53   const TargetRegisterInfo *TRI = Subtarget->getRegisterInfo();
  54   const TargetRegisterClass *TRC = MRI->getRegClass(RegNo);
  55   for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64, MVT::v16i8, MVT::v8i16,
  56                 MVT::v4i32, MVT::v2i64, MVT::v4f32, MVT::v2f64})
  57     if (TRI->isTypeLegalForClass(*TRC, T))
  58       return T;
  59   LLVM_DEBUG(errs() << "Unknown type for register number: " << RegNo);
  60   llvm_unreachable("Unknown register type");
  61   return MVT::Other;
  62 }
  63
  64 std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
  65   unsigned RegNo = MO.getReg();
  66   assert(TargetRegisterInfo::isVirtualRegister(RegNo) &&
  67          "Unlowered physical register encountered during assembly printing");
  68   assert(!MFI->isVRegStackified(RegNo));
  69   unsigned WAReg = MFI->getWAReg(RegNo);
  70   assert(WAReg != WebAssemblyFunctionInfo::UnusedReg);
  71   return '$' + utostr(WAReg);
  72 }
  73
  74 WebAssemblyTargetStreamer *WebAssemblyAsmPrinter::getTargetStreamer() {
  75   MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
  76   return static_cast<WebAssemblyTargetStreamer *>(TS);
  77 }
  78
  79 //===----------------------------------------------------------------------===//
  80 // WebAssemblyAsmPrinter Implementation.
  81 //===----------------------------------------------------------------------===//
  82
  83 void WebAssemblyAsmPrinter::EmitEndOfAsmFile(Module &M) {
  84   for (auto &It : OutContext.getSymbols()) {
  85     // Emit a .globaltype and .eventtype declaration.
  86     auto Sym = cast<MCSymbolWasm>(It.getValue());
  87     if (Sym->getType() == wasm::WASM_SYMBOL_TYPE_GLOBAL)
  88       getTargetStreamer()->emitGlobalType(Sym);
  89     else if (Sym->getType() == wasm::WASM_SYMBOL_TYPE_EVENT)
  90       getTargetStreamer()->emitEventType(Sym);
  91   }
  92
  93   for (const auto &F : M) {
  94     // Emit function type info for all undefined functions
  95     if (F.isDeclarationForLinker() && !F.isIntrinsic()) {
  96       SmallVector<MVT, 4> Results;
  97       SmallVector<MVT, 4> Params;
  98       computeSignatureVTs(F.getFunctionType(), F, TM, Params, Results);
  99       auto *Sym = cast<MCSymbolWasm>(getSymbol(&F));
 100       Sym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
 101       if (!Sym->getSignature()) {
 102         auto Signature = signatureFromMVTs(Results, Params);
 103         Sym->setSignature(Signature.get());
 104         addSignature(std::move(Signature));
 105       }
 106       // FIXME: this was originally intended for post-linking and was only used
 107       // for imports that were only called indirectly (i.e. s2wasm could not
 108       // infer the type from a call). With object files it applies to all
 109       // imports. so fix the names and the tests, or rethink how import
 110       // delcarations work in asm files.
 111       getTargetStreamer()->emitFunctionType(Sym);
 112
 113       if (TM.getTargetTriple().isOSBinFormatWasm() &&
 114           F.hasFnAttribute("wasm-import-module")) {
 115         StringRef Name =
 116             F.getFnAttribute("wasm-import-module").getValueAsString();
 117         Sym->setImportModule(Name);
 118         getTargetStreamer()->emitImportModule(Sym, Name);
 119       }
 120       if (TM.getTargetTriple().isOSBinFormatWasm() &&
 121           F.hasFnAttribute("wasm-import-name")) {
 122         StringRef Name =
 123             F.getFnAttribute("wasm-import-name").getValueAsString();
 124         Sym->setImportName(Name);
 125         getTargetStreamer()->emitImportName(Sym, Name);
 126       }
 127     }
 128   }
 129
 130   for (const auto &G : M.globals()) {
 131     if (!G.hasInitializer() && G.hasExternalLinkage()) {
 132       if (G.getValueType()->isSized()) {
 133         uint16_t Size = M.getDataLayout().getTypeAllocSize(G.getValueType());
 134         OutStreamer->emitELFSize(getSymbol(&G),
 135                                  MCConstantExpr::create(Size, OutContext));
 136       }
 137     }
 138   }
 139
 140   if (const NamedMDNode *Named = M.getNamedMetadata("wasm.custom_sections")) {
 141     for (const Metadata *MD : Named->operands()) {
 142       const auto *Tuple = dyn_cast<MDTuple>(MD);
 143       if (!Tuple || Tuple->getNumOperands() != 2)
 144         continue;
 145       const MDString *Name = dyn_cast<MDString>(Tuple->getOperand(0));
 146       const MDString *Contents = dyn_cast<MDString>(Tuple->getOperand(1));
 147       if (!Name || !Contents)
 148         continue;
 149
 150       OutStreamer->PushSection();
 151       std::string SectionName = (".custom_section." + Name->getString()).str();
 152       MCSectionWasm *MySection =
 153           OutContext.getWasmSection(SectionName, SectionKind::getMetadata());
 154       OutStreamer->SwitchSection(MySection);
 155       OutStreamer->EmitBytes(Contents->getString());
 156       OutStreamer->PopSection();
 157     }
 158   }
 159
 160   EmitProducerInfo(M);
 161 }
 162
 163 void WebAssemblyAsmPrinter::EmitProducerInfo(Module &M) {
 164   llvm::SmallVector<std::pair<std::string, std::string>, 4> Languages;
 165   if (const NamedMDNode *Debug = M.getNamedMetadata("llvm.dbg.cu")) {
 166     llvm::SmallSet<StringRef, 4> SeenLanguages;
 167     for (size_t I = 0, E = Debug->getNumOperands(); I < E; ++I) {
 168       const auto *CU = cast<DICompileUnit>(Debug->getOperand(I));
 169       StringRef Language = dwarf::LanguageString(CU->getSourceLanguage());
 170       Language.consume_front("DW_LANG_");
 171       if (SeenLanguages.insert(Language).second)
 172         Languages.emplace_back(Language.str(), "");
 173     }
 174   }
 175
 176   llvm::SmallVector<std::pair<std::string, std::string>, 4> Tools;
 177   if (const NamedMDNode *Ident = M.getNamedMetadata("llvm.ident")) {
 178     llvm::SmallSet<StringRef, 4> SeenTools;
 179     for (size_t I = 0, E = Ident->getNumOperands(); I < E; ++I) {
 180       const auto *S = cast<MDString>(Ident->getOperand(I)->getOperand(0));
 181       std::pair<StringRef, StringRef> Field = S->getString().split("version");
 182       StringRef Name = Field.first.trim();
 183       StringRef Version = Field.second.trim();
 184       if (SeenTools.insert(Name).second)
 185         Tools.emplace_back(Name.str(), Version.str());
 186     }
 187   }
 188
 189   int FieldCount = int(!Languages.empty()) + int(!Tools.empty());
 190   if (FieldCount != 0) {
 191     MCSectionWasm *Producers = OutContext.getWasmSection(
 192         ".custom_section.producers", SectionKind::getMetadata());
 193     OutStreamer->PushSection();
 194     OutStreamer->SwitchSection(Producers);
 195     OutStreamer->EmitULEB128IntValue(FieldCount);
 196     for (auto &Producers : {std::make_pair("language", &Languages),
 197             std::make_pair("processed-by", &Tools)}) {
 198       if (Producers.second->empty())
 199         continue;
 200       OutStreamer->EmitULEB128IntValue(strlen(Producers.first));
 201       OutStreamer->EmitBytes(Producers.first);
 202       OutStreamer->EmitULEB128IntValue(Producers.second->size());
 203       for (auto &Producer : *Producers.second) {
 204         OutStreamer->EmitULEB128IntValue(Producer.first.size());
 205         OutStreamer->EmitBytes(Producer.first);
 206         OutStreamer->EmitULEB128IntValue(Producer.second.size());
 207         OutStreamer->EmitBytes(Producer.second);
 208       }
 209     }
 210     OutStreamer->PopSection();
 211   }
 212 }
 213
 214 void WebAssemblyAsmPrinter::EmitConstantPool() {
 215   assert(MF->getConstantPool()->getConstants().empty() &&
 216          "WebAssembly disables constant pools");
 217 }
 218
 219 void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
 220   // Nothing to do; jump tables are incorporated into the instruction stream.
 221 }
 222
 223 void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
 224   const Function &F = MF->getFunction();
 225   SmallVector<MVT, 1> ResultVTs;
 226   SmallVector<MVT, 4> ParamVTs;
 227   computeSignatureVTs(F.getFunctionType(), F, TM, ParamVTs, ResultVTs);
 228   auto Signature = signatureFromMVTs(ResultVTs, ParamVTs);
 229   auto *WasmSym = cast<MCSymbolWasm>(CurrentFnSym);
 230   WasmSym->setSignature(Signature.get());
 231   addSignature(std::move(Signature));
 232   WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
 233
 234   // FIXME: clean up how params and results are emitted (use signatures)
 235   getTargetStreamer()->emitFunctionType(WasmSym);
 236
 237   // Emit the function index.
 238   if (MDNode *Idx = F.getMetadata("wasm.index")) {
 239     assert(Idx->getNumOperands() == 1);
 240
 241     getTargetStreamer()->emitIndIdx(AsmPrinter::lowerConstant(
 242         cast<ConstantAsMetadata>(Idx->getOperand(0))->getValue()));
 243   }
 244
 245   SmallVector<wasm::ValType, 16> Locals;
 246   valTypesFromMVTs(MFI->getLocals(), Locals);
 247   getTargetStreamer()->emitLocal(Locals);
 248
 249   AsmPrinter::EmitFunctionBodyStart();
 250 }
 251
 252 void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
 253   LLVM_DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
 254
 255   switch (MI->getOpcode()) {
 256   case WebAssembly::ARGUMENT_i32:
 257   case WebAssembly::ARGUMENT_i32_S:
 258   case WebAssembly::ARGUMENT_i64:
 259   case WebAssembly::ARGUMENT_i64_S:
 260   case WebAssembly::ARGUMENT_f32:
 261   case WebAssembly::ARGUMENT_f32_S:
 262   case WebAssembly::ARGUMENT_f64:
 263   case WebAssembly::ARGUMENT_f64_S:
 264   case WebAssembly::ARGUMENT_v16i8:
 265   case WebAssembly::ARGUMENT_v16i8_S:
 266   case WebAssembly::ARGUMENT_v8i16:
 267   case WebAssembly::ARGUMENT_v8i16_S:
 268   case WebAssembly::ARGUMENT_v4i32:
 269   case WebAssembly::ARGUMENT_v4i32_S:
 270   case WebAssembly::ARGUMENT_v2i64:
 271   case WebAssembly::ARGUMENT_v2i64_S:
 272   case WebAssembly::ARGUMENT_v4f32:
 273   case WebAssembly::ARGUMENT_v4f32_S:
 274   case WebAssembly::ARGUMENT_v2f64:
 275   case WebAssembly::ARGUMENT_v2f64_S:
 276     // These represent values which are live into the function entry, so there's
 277     // no instruction to emit.
 278     break;
 279   case WebAssembly::FALLTHROUGH_RETURN_I32:
 280   case WebAssembly::FALLTHROUGH_RETURN_I32_S:
 281   case WebAssembly::FALLTHROUGH_RETURN_I64:
 282   case WebAssembly::FALLTHROUGH_RETURN_I64_S:
 283   case WebAssembly::FALLTHROUGH_RETURN_F32:
 284   case WebAssembly::FALLTHROUGH_RETURN_F32_S:
 285   case WebAssembly::FALLTHROUGH_RETURN_F64:
 286   case WebAssembly::FALLTHROUGH_RETURN_F64_S:
 287   case WebAssembly::FALLTHROUGH_RETURN_v16i8:
 288   case WebAssembly::FALLTHROUGH_RETURN_v16i8_S:
 289   case WebAssembly::FALLTHROUGH_RETURN_v8i16:
 290   case WebAssembly::FALLTHROUGH_RETURN_v8i16_S:
 291   case WebAssembly::FALLTHROUGH_RETURN_v4i32:
 292   case WebAssembly::FALLTHROUGH_RETURN_v4i32_S:
 293   case WebAssembly::FALLTHROUGH_RETURN_v2i64:
 294   case WebAssembly::FALLTHROUGH_RETURN_v2i64_S:
 295   case WebAssembly::FALLTHROUGH_RETURN_v4f32:
 296   case WebAssembly::FALLTHROUGH_RETURN_v4f32_S:
 297   case WebAssembly::FALLTHROUGH_RETURN_v2f64:
 298   case WebAssembly::FALLTHROUGH_RETURN_v2f64_S: {
 299     // These instructions represent the implicit return at the end of a
 300     // function body. Always pops one value off the stack.
 301     if (isVerbose()) {
 302       OutStreamer->AddComment("fallthrough-return-value");
 303       OutStreamer->AddBlankLine();
 304     }
 305     break;
 306   }
 307   case WebAssembly::FALLTHROUGH_RETURN_VOID:
 308   case WebAssembly::FALLTHROUGH_RETURN_VOID_S:
 309     // This instruction represents the implicit return at the end of a
 310     // function body with no return value.
 311     if (isVerbose()) {
 312       OutStreamer->AddComment("fallthrough-return-void");
 313       OutStreamer->AddBlankLine();
 314     }
 315     break;
 316   case WebAssembly::EXTRACT_EXCEPTION_I32:
 317   case WebAssembly::EXTRACT_EXCEPTION_I32_S:
 318     // These are pseudo instructions that simulates popping values from stack.
 319     // We print these only when we have -wasm-keep-registers on for assembly
 320     // readability.
 321     if (!WasmKeepRegisters)
 322       break;
 323     LLVM_FALLTHROUGH;
 324   default: {
 325     WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
 326     MCInst TmpInst;
 327     MCInstLowering.lower(MI, TmpInst);
 328     EmitToStreamer(*OutStreamer, TmpInst);
 329     break;
 330   }
 331   }
 332 }
 333
 334 const MCExpr *WebAssemblyAsmPrinter::lowerConstant(const Constant *CV) {
 335   if (const auto *GV = dyn_cast<GlobalValue>(CV))
 336     if (GV->getValueType()->isFunctionTy()) {
 337       return MCSymbolRefExpr::create(
 338           getSymbol(GV), MCSymbolRefExpr::VK_WebAssembly_FUNCTION, OutContext);
 339     }
 340   return AsmPrinter::lowerConstant(CV);
 341 }
 342
 343 bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
 344                                             unsigned OpNo, unsigned AsmVariant,
 345                                             const char *ExtraCode,
 346                                             raw_ostream &OS) {
 347   if (AsmVariant != 0)
 348     report_fatal_error("There are no defined alternate asm variants");
 349
 350   // First try the generic code, which knows about modifiers like 'c' and 'n'.
 351   if (!AsmPrinter::PrintAsmOperand(MI, OpNo, AsmVariant, ExtraCode, OS))
 352     return false;
 353
 354   if (!ExtraCode) {
 355     const MachineOperand &MO = MI->getOperand(OpNo);
 356     switch (MO.getType()) {
 357     case MachineOperand::MO_Immediate:
 358       OS << MO.getImm();
 359       return false;
 360     case MachineOperand::MO_Register:
 361       // FIXME: only opcode that still contains registers, as required by
 362       // MachineInstr::getDebugVariable().
 363       assert(MI->getOpcode() == WebAssembly::INLINEASM);
 364       OS << regToString(MO);
 365       return false;
 366     case MachineOperand::MO_GlobalAddress:
 367       getSymbol(MO.getGlobal())->print(OS, MAI);
 368       printOffset(MO.getOffset(), OS);
 369       return false;
 370     case MachineOperand::MO_ExternalSymbol:
 371       GetExternalSymbolSymbol(MO.getSymbolName())->print(OS, MAI);
 372       printOffset(MO.getOffset(), OS);
 373       return false;
 374     case MachineOperand::MO_MachineBasicBlock:
 375       MO.getMBB()->getSymbol()->print(OS, MAI);
 376       return false;
 377     default:
 378       break;
 379     }
 380   }
 381
 382   return true;
 383 }
 384
 385 bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
 386                                                   unsigned OpNo,
 387                                                   unsigned AsmVariant,
 388                                                   const char *ExtraCode,
 389                                                   raw_ostream &OS) {
 390   if (AsmVariant != 0)
 391     report_fatal_error("There are no defined alternate asm variants");
 392
 393   // The current approach to inline asm is that "r" constraints are expressed
 394   // as local indices, rather than values on the operand stack. This simplifies
 395   // using "r" as it eliminates the need to push and pop the values in a
 396   // particular order, however it also makes it impossible to have an "m"
 397   // constraint. So we don't support it.
 398
 399   return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, AsmVariant, ExtraCode, OS);
 400 }
 401
 402 // Force static initialization.
 403 extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
 404   RegisterAsmPrinter<WebAssemblyAsmPrinter> X(getTheWebAssemblyTarget32());
 405   RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(getTheWebAssemblyTarget64());
 406 }