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 "MCTargetDesc/WebAssemblyInstPrinter.h"
  18 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
  19 #include "MCTargetDesc/WebAssemblyTargetStreamer.h"
  20 #include "TargetInfo/WebAssemblyTargetInfo.h"
  21 #include "WebAssembly.h"
  22 #include "WebAssemblyMCInstLower.h"
  23 #include "WebAssemblyMachineFunctionInfo.h"
  24 #include "WebAssemblyRegisterInfo.h"
  25 #include "WebAssemblyTargetMachine.h"
  26 #include "llvm/ADT/SmallSet.h"
  27 #include "llvm/ADT/StringExtras.h"
  28 #include "llvm/BinaryFormat/Wasm.h"
  29 #include "llvm/CodeGen/Analysis.h"
  30 #include "llvm/CodeGen/AsmPrinter.h"
  31 #include "llvm/CodeGen/MachineConstantPool.h"
  32 #include "llvm/CodeGen/MachineInstr.h"
  33 #include "llvm/CodeGen/MachineModuleInfoImpls.h"
  34 #include "llvm/IR/DataLayout.h"
  35 #include "llvm/IR/DebugInfoMetadata.h"
  36 #include "llvm/IR/GlobalVariable.h"
  37 #include "llvm/IR/Metadata.h"
  38 #include "llvm/MC/MCContext.h"
  39 #include "llvm/MC/MCSectionWasm.h"
  40 #include "llvm/MC/MCStreamer.h"
  41 #include "llvm/MC/MCSymbol.h"
  42 #include "llvm/MC/MCSymbolWasm.h"
  43 #include "llvm/Support/Debug.h"
  44 #include "llvm/Support/TargetRegistry.h"
  45 #include "llvm/Support/raw_ostream.h"
  46
  47 using namespace llvm;
  48
  49 #define DEBUG_TYPE "asm-printer"
  50
  51 extern cl::opt<bool> WasmKeepRegisters;
  52
  53 //===----------------------------------------------------------------------===//
  54 // Helpers.
  55 //===----------------------------------------------------------------------===//
  56
  57 MVT WebAssemblyAsmPrinter::getRegType(unsigned RegNo) const {
  58   const TargetRegisterInfo *TRI = Subtarget->getRegisterInfo();
  59   const TargetRegisterClass *TRC = MRI->getRegClass(RegNo);
  60   for (MVT T : {MVT::i32, MVT::i64, MVT::f32, MVT::f64, MVT::v16i8, MVT::v8i16,
  61                 MVT::v4i32, MVT::v2i64, MVT::v4f32, MVT::v2f64})
  62     if (TRI->isTypeLegalForClass(*TRC, T))
  63       return T;
  64   LLVM_DEBUG(errs() << "Unknown type for register number: " << RegNo);
  65   llvm_unreachable("Unknown register type");
  66   return MVT::Other;
  67 }
  68
  69 std::string WebAssemblyAsmPrinter::regToString(const MachineOperand &MO) {
  70   Register RegNo = MO.getReg();
  71   assert(Register::isVirtualRegister(RegNo) &&
  72          "Unlowered physical register encountered during assembly printing");
  73   assert(!MFI->isVRegStackified(RegNo));
  74   unsigned WAReg = MFI->getWAReg(RegNo);
  75   assert(WAReg != WebAssemblyFunctionInfo::UnusedReg);
  76   return '$' + utostr(WAReg);
  77 }
  78
  79 WebAssemblyTargetStreamer *WebAssemblyAsmPrinter::getTargetStreamer() {
  80   MCTargetStreamer *TS = OutStreamer->getTargetStreamer();
  81   return static_cast<WebAssemblyTargetStreamer *>(TS);
  82 }
  83
  84 //===----------------------------------------------------------------------===//
  85 // WebAssemblyAsmPrinter Implementation.
  86 //===----------------------------------------------------------------------===//
  87
  88 void WebAssemblyAsmPrinter::EmitEndOfAsmFile(Module &M) {
  89   for (auto &It : OutContext.getSymbols()) {
  90     // Emit a .globaltype and .eventtype declaration.
  91     auto Sym = cast<MCSymbolWasm>(It.getValue());
  92     if (Sym->getType() == wasm::WASM_SYMBOL_TYPE_GLOBAL)
  93       getTargetStreamer()->emitGlobalType(Sym);
  94     else if (Sym->getType() == wasm::WASM_SYMBOL_TYPE_EVENT)
  95       getTargetStreamer()->emitEventType(Sym);
  96   }
  97
  98   for (const auto &F : M) {
  99     // Emit function type info for all undefined functions
 100     if (F.isDeclarationForLinker() && !F.isIntrinsic()) {
 101       SmallVector<MVT, 4> Results;
 102       SmallVector<MVT, 4> Params;
 103       computeSignatureVTs(F.getFunctionType(), F, TM, Params, Results);
 104       auto *Sym = cast<MCSymbolWasm>(getSymbol(&F));
 105       Sym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
 106       if (!Sym->getSignature()) {
 107         auto Signature = signatureFromMVTs(Results, Params);
 108         Sym->setSignature(Signature.get());
 109         addSignature(std::move(Signature));
 110       }
 111       // FIXME: this was originally intended for post-linking and was only used
 112       // for imports that were only called indirectly (i.e. s2wasm could not
 113       // infer the type from a call). With object files it applies to all
 114       // imports. so fix the names and the tests, or rethink how import
 115       // delcarations work in asm files.
 116       getTargetStreamer()->emitFunctionType(Sym);
 117
 118       if (TM.getTargetTriple().isOSBinFormatWasm() &&
 119           F.hasFnAttribute("wasm-import-module")) {
 120         StringRef Name =
 121             F.getFnAttribute("wasm-import-module").getValueAsString();
 122         Sym->setImportModule(Name);
 123         getTargetStreamer()->emitImportModule(Sym, Name);
 124       }
 125       if (TM.getTargetTriple().isOSBinFormatWasm() &&
 126           F.hasFnAttribute("wasm-import-name")) {
 127         StringRef Name =
 128             F.getFnAttribute("wasm-import-name").getValueAsString();
 129         Sym->setImportName(Name);
 130         getTargetStreamer()->emitImportName(Sym, Name);
 131       }
 132     }
 133   }
 134
 135   for (const auto &G : M.globals()) {
 136     if (!G.hasInitializer() && G.hasExternalLinkage()) {
 137       if (G.getValueType()->isSized()) {
 138         uint16_t Size = M.getDataLayout().getTypeAllocSize(G.getValueType());
 139         OutStreamer->emitELFSize(getSymbol(&G),
 140                                  MCConstantExpr::create(Size, OutContext));
 141       }
 142     }
 143   }
 144
 145   if (const NamedMDNode *Named = M.getNamedMetadata("wasm.custom_sections")) {
 146     for (const Metadata *MD : Named->operands()) {
 147       const auto *Tuple = dyn_cast<MDTuple>(MD);
 148       if (!Tuple || Tuple->getNumOperands() != 2)
 149         continue;
 150       const MDString *Name = dyn_cast<MDString>(Tuple->getOperand(0));
 151       const MDString *Contents = dyn_cast<MDString>(Tuple->getOperand(1));
 152       if (!Name || !Contents)
 153         continue;
 154
 155       OutStreamer->PushSection();
 156       std::string SectionName = (".custom_section." + Name->getString()).str();
 157       MCSectionWasm *MySection =
 158           OutContext.getWasmSection(SectionName, SectionKind::getMetadata());
 159       OutStreamer->SwitchSection(MySection);
 160       OutStreamer->EmitBytes(Contents->getString());
 161       OutStreamer->PopSection();
 162     }
 163   }
 164
 165   EmitProducerInfo(M);
 166   EmitTargetFeatures(M);
 167 }
 168
 169 void WebAssemblyAsmPrinter::EmitProducerInfo(Module &M) {
 170   llvm::SmallVector<std::pair<std::string, std::string>, 4> Languages;
 171   if (const NamedMDNode *Debug = M.getNamedMetadata("llvm.dbg.cu")) {
 172     llvm::SmallSet<StringRef, 4> SeenLanguages;
 173     for (size_t I = 0, E = Debug->getNumOperands(); I < E; ++I) {
 174       const auto *CU = cast<DICompileUnit>(Debug->getOperand(I));
 175       StringRef Language = dwarf::LanguageString(CU->getSourceLanguage());
 176       Language.consume_front("DW_LANG_");
 177       if (SeenLanguages.insert(Language).second)
 178         Languages.emplace_back(Language.str(), "");
 179     }
 180   }
 181
 182   llvm::SmallVector<std::pair<std::string, std::string>, 4> Tools;
 183   if (const NamedMDNode *Ident = M.getNamedMetadata("llvm.ident")) {
 184     llvm::SmallSet<StringRef, 4> SeenTools;
 185     for (size_t I = 0, E = Ident->getNumOperands(); I < E; ++I) {
 186       const auto *S = cast<MDString>(Ident->getOperand(I)->getOperand(0));
 187       std::pair<StringRef, StringRef> Field = S->getString().split("version");
 188       StringRef Name = Field.first.trim();
 189       StringRef Version = Field.second.trim();
 190       if (SeenTools.insert(Name).second)
 191         Tools.emplace_back(Name.str(), Version.str());
 192     }
 193   }
 194
 195   int FieldCount = int(!Languages.empty()) + int(!Tools.empty());
 196   if (FieldCount != 0) {
 197     MCSectionWasm *Producers = OutContext.getWasmSection(
 198         ".custom_section.producers", SectionKind::getMetadata());
 199     OutStreamer->PushSection();
 200     OutStreamer->SwitchSection(Producers);
 201     OutStreamer->EmitULEB128IntValue(FieldCount);
 202     for (auto &Producers : {std::make_pair("language", &Languages),
 203             std::make_pair("processed-by", &Tools)}) {
 204       if (Producers.second->empty())
 205         continue;
 206       OutStreamer->EmitULEB128IntValue(strlen(Producers.first));
 207       OutStreamer->EmitBytes(Producers.first);
 208       OutStreamer->EmitULEB128IntValue(Producers.second->size());
 209       for (auto &Producer : *Producers.second) {
 210         OutStreamer->EmitULEB128IntValue(Producer.first.size());
 211         OutStreamer->EmitBytes(Producer.first);
 212         OutStreamer->EmitULEB128IntValue(Producer.second.size());
 213         OutStreamer->EmitBytes(Producer.second);
 214       }
 215     }
 216     OutStreamer->PopSection();
 217   }
 218 }
 219
 220 void WebAssemblyAsmPrinter::EmitTargetFeatures(Module &M) {
 221   struct FeatureEntry {
 222     uint8_t Prefix;
 223     StringRef Name;
 224   };
 225
 226   // Read target features and linkage policies from module metadata
 227   SmallVector<FeatureEntry, 4> EmittedFeatures;
 228   for (const SubtargetFeatureKV &KV : WebAssemblyFeatureKV) {
 229     std::string MDKey = (StringRef("wasm-feature-") + KV.Key).str();
 230     Metadata *Policy = M.getModuleFlag(MDKey);
 231     if (Policy == nullptr)
 232       continue;
 233
 234     FeatureEntry Entry;
 235     Entry.Prefix = 0;
 236     Entry.Name = KV.Key;
 237
 238     if (auto *MD = cast<ConstantAsMetadata>(Policy))
 239       if (auto *I = cast<ConstantInt>(MD->getValue()))
 240         Entry.Prefix = I->getZExtValue();
 241
 242     // Silently ignore invalid metadata
 243     if (Entry.Prefix != wasm::WASM_FEATURE_PREFIX_USED &&
 244         Entry.Prefix != wasm::WASM_FEATURE_PREFIX_REQUIRED &&
 245         Entry.Prefix != wasm::WASM_FEATURE_PREFIX_DISALLOWED)
 246       continue;
 247
 248     EmittedFeatures.push_back(Entry);
 249   }
 250
 251   if (EmittedFeatures.size() == 0)
 252     return;
 253
 254   // Emit features and linkage policies into the "target_features" section
 255   MCSectionWasm *FeaturesSection = OutContext.getWasmSection(
 256       ".custom_section.target_features", SectionKind::getMetadata());
 257   OutStreamer->PushSection();
 258   OutStreamer->SwitchSection(FeaturesSection);
 259
 260   OutStreamer->EmitULEB128IntValue(EmittedFeatures.size());
 261   for (auto &F : EmittedFeatures) {
 262     OutStreamer->EmitIntValue(F.Prefix, 1);
 263     OutStreamer->EmitULEB128IntValue(F.Name.size());
 264     OutStreamer->EmitBytes(F.Name);
 265   }
 266
 267   OutStreamer->PopSection();
 268 }
 269
 270 void WebAssemblyAsmPrinter::EmitConstantPool() {
 271   assert(MF->getConstantPool()->getConstants().empty() &&
 272          "WebAssembly disables constant pools");
 273 }
 274
 275 void WebAssemblyAsmPrinter::EmitJumpTableInfo() {
 276   // Nothing to do; jump tables are incorporated into the instruction stream.
 277 }
 278
 279 void WebAssemblyAsmPrinter::EmitFunctionBodyStart() {
 280   const Function &F = MF->getFunction();
 281   SmallVector<MVT, 1> ResultVTs;
 282   SmallVector<MVT, 4> ParamVTs;
 283   computeSignatureVTs(F.getFunctionType(), F, TM, ParamVTs, ResultVTs);
 284   auto Signature = signatureFromMVTs(ResultVTs, ParamVTs);
 285   auto *WasmSym = cast<MCSymbolWasm>(CurrentFnSym);
 286   WasmSym->setSignature(Signature.get());
 287   addSignature(std::move(Signature));
 288   WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
 289
 290   // FIXME: clean up how params and results are emitted (use signatures)
 291   getTargetStreamer()->emitFunctionType(WasmSym);
 292
 293   // Emit the function index.
 294   if (MDNode *Idx = F.getMetadata("wasm.index")) {
 295     assert(Idx->getNumOperands() == 1);
 296
 297     getTargetStreamer()->emitIndIdx(AsmPrinter::lowerConstant(
 298         cast<ConstantAsMetadata>(Idx->getOperand(0))->getValue()));
 299   }
 300
 301   SmallVector<wasm::ValType, 16> Locals;
 302   valTypesFromMVTs(MFI->getLocals(), Locals);
 303   getTargetStreamer()->emitLocal(Locals);
 304
 305   AsmPrinter::EmitFunctionBodyStart();
 306 }
 307
 308 void WebAssemblyAsmPrinter::EmitInstruction(const MachineInstr *MI) {
 309   LLVM_DEBUG(dbgs() << "EmitInstruction: " << *MI << '\n');
 310
 311   switch (MI->getOpcode()) {
 312   case WebAssembly::ARGUMENT_i32:
 313   case WebAssembly::ARGUMENT_i32_S:
 314   case WebAssembly::ARGUMENT_i64:
 315   case WebAssembly::ARGUMENT_i64_S:
 316   case WebAssembly::ARGUMENT_f32:
 317   case WebAssembly::ARGUMENT_f32_S:
 318   case WebAssembly::ARGUMENT_f64:
 319   case WebAssembly::ARGUMENT_f64_S:
 320   case WebAssembly::ARGUMENT_v16i8:
 321   case WebAssembly::ARGUMENT_v16i8_S:
 322   case WebAssembly::ARGUMENT_v8i16:
 323   case WebAssembly::ARGUMENT_v8i16_S:
 324   case WebAssembly::ARGUMENT_v4i32:
 325   case WebAssembly::ARGUMENT_v4i32_S:
 326   case WebAssembly::ARGUMENT_v2i64:
 327   case WebAssembly::ARGUMENT_v2i64_S:
 328   case WebAssembly::ARGUMENT_v4f32:
 329   case WebAssembly::ARGUMENT_v4f32_S:
 330   case WebAssembly::ARGUMENT_v2f64:
 331   case WebAssembly::ARGUMENT_v2f64_S:
 332     // These represent values which are live into the function entry, so there's
 333     // no instruction to emit.
 334     break;
 335   case WebAssembly::FALLTHROUGH_RETURN: {
 336     // These instructions represent the implicit return at the end of a
 337     // function body.
 338     if (isVerbose()) {
 339       OutStreamer->AddComment("fallthrough-return");
 340       OutStreamer->AddBlankLine();
 341     }
 342     break;
 343   }
 344   case WebAssembly::COMPILER_FENCE:
 345     // This is a compiler barrier that prevents instruction reordering during
 346     // backend compilation, and should not be emitted.
 347     break;
 348   case WebAssembly::EXTRACT_EXCEPTION_I32:
 349   case WebAssembly::EXTRACT_EXCEPTION_I32_S:
 350     // These are pseudo instructions that simulates popping values from stack.
 351     // We print these only when we have -wasm-keep-registers on for assembly
 352     // readability.
 353     if (!WasmKeepRegisters)
 354       break;
 355     LLVM_FALLTHROUGH;
 356   default: {
 357     WebAssemblyMCInstLower MCInstLowering(OutContext, *this);
 358     MCInst TmpInst;
 359     MCInstLowering.lower(MI, TmpInst);
 360     EmitToStreamer(*OutStreamer, TmpInst);
 361     break;
 362   }
 363   }
 364 }
 365
 366 bool WebAssemblyAsmPrinter::PrintAsmOperand(const MachineInstr *MI,
 367                                             unsigned OpNo,
 368                                             const char *ExtraCode,
 369                                             raw_ostream &OS) {
 370   // First try the generic code, which knows about modifiers like 'c' and 'n'.
 371   if (!AsmPrinter::PrintAsmOperand(MI, OpNo, ExtraCode, OS))
 372     return false;
 373
 374   if (!ExtraCode) {
 375     const MachineOperand &MO = MI->getOperand(OpNo);
 376     switch (MO.getType()) {
 377     case MachineOperand::MO_Immediate:
 378       OS << MO.getImm();
 379       return false;
 380     case MachineOperand::MO_Register:
 381       // FIXME: only opcode that still contains registers, as required by
 382       // MachineInstr::getDebugVariable().
 383       assert(MI->getOpcode() == WebAssembly::INLINEASM);
 384       OS << regToString(MO);
 385       return false;
 386     case MachineOperand::MO_GlobalAddress:
 387       PrintSymbolOperand(MO, OS);
 388       return false;
 389     case MachineOperand::MO_ExternalSymbol:
 390       GetExternalSymbolSymbol(MO.getSymbolName())->print(OS, MAI);
 391       printOffset(MO.getOffset(), OS);
 392       return false;
 393     case MachineOperand::MO_MachineBasicBlock:
 394       MO.getMBB()->getSymbol()->print(OS, MAI);
 395       return false;
 396     default:
 397       break;
 398     }
 399   }
 400
 401   return true;
 402 }
 403
 404 bool WebAssemblyAsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI,
 405                                                   unsigned OpNo,
 406                                                   const char *ExtraCode,
 407                                                   raw_ostream &OS) {
 408   // The current approach to inline asm is that "r" constraints are expressed
 409   // as local indices, rather than values on the operand stack. This simplifies
 410   // using "r" as it eliminates the need to push and pop the values in a
 411   // particular order, however it also makes it impossible to have an "m"
 412   // constraint. So we don't support it.
 413
 414   return AsmPrinter::PrintAsmMemoryOperand(MI, OpNo, ExtraCode, OS);
 415 }
 416
 417 // Force static initialization.
 418 extern "C" void LLVMInitializeWebAssemblyAsmPrinter() {
 419   RegisterAsmPrinter<WebAssemblyAsmPrinter> X(getTheWebAssemblyTarget32());
 420   RegisterAsmPrinter<WebAssemblyAsmPrinter> Y(getTheWebAssemblyTarget64());
 421 }