1 //==- WebAssemblyAsmParser.cpp - Assembler for WebAssembly -*- C++ -*-==//
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 is part of the WebAssembly Assembler.
11 ///
12 /// It contains code to translate a parsed .s file into MCInsts.
13 ///
14 //===----------------------------------------------------------------------===//
15 
16 #include "MCTargetDesc/WebAssemblyMCTargetDesc.h"
17 #include "MCTargetDesc/WebAssemblyTargetStreamer.h"
18 #include "TargetInfo/WebAssemblyTargetInfo.h"
19 #include "WebAssembly.h"
20 #include "llvm/MC/MCContext.h"
21 #include "llvm/MC/MCExpr.h"
22 #include "llvm/MC/MCInst.h"
23 #include "llvm/MC/MCInstrInfo.h"
24 #include "llvm/MC/MCParser/MCParsedAsmOperand.h"
25 #include "llvm/MC/MCParser/MCTargetAsmParser.h"
26 #include "llvm/MC/MCSectionWasm.h"
27 #include "llvm/MC/MCStreamer.h"
28 #include "llvm/MC/MCSubtargetInfo.h"
29 #include "llvm/MC/MCSymbol.h"
30 #include "llvm/MC/MCSymbolWasm.h"
31 #include "llvm/Support/Endian.h"
32 #include "llvm/Support/TargetRegistry.h"
33 
34 using namespace llvm;
35 
36 #define DEBUG_TYPE "wasm-asm-parser"
37 
38 namespace {
39 
40 /// WebAssemblyOperand - Instances of this class represent the operands in a
41 /// parsed WASM machine instruction.
42 struct WebAssemblyOperand : public MCParsedAsmOperand {
43   enum KindTy { Token, Integer, Float, Symbol, BrList } Kind;
44 
45   SMLoc StartLoc, EndLoc;
46 
47   struct TokOp {
48     StringRef Tok;
49   };
50 
51   struct IntOp {
52     int64_t Val;
53   };
54 
55   struct FltOp {
56     double Val;
57   };
58 
59   struct SymOp {
60     const MCExpr *Exp;
61   };
62 
63   struct BrLOp {
64     std::vector<unsigned> List;
65   };
66 
67   union {
68     struct TokOp Tok;
69     struct IntOp Int;
70     struct FltOp Flt;
71     struct SymOp Sym;
72     struct BrLOp BrL;
73   };
74 
75   WebAssemblyOperand(KindTy K, SMLoc Start, SMLoc End, TokOp T)
76       : Kind(K), StartLoc(Start), EndLoc(End), Tok(T) {}
77   WebAssemblyOperand(KindTy K, SMLoc Start, SMLoc End, IntOp I)
78       : Kind(K), StartLoc(Start), EndLoc(End), Int(I) {}
79   WebAssemblyOperand(KindTy K, SMLoc Start, SMLoc End, FltOp F)
80       : Kind(K), StartLoc(Start), EndLoc(End), Flt(F) {}
81   WebAssemblyOperand(KindTy K, SMLoc Start, SMLoc End, SymOp S)
82       : Kind(K), StartLoc(Start), EndLoc(End), Sym(S) {}
83   WebAssemblyOperand(KindTy K, SMLoc Start, SMLoc End)
84       : Kind(K), StartLoc(Start), EndLoc(End), BrL() {}
85 
86   ~WebAssemblyOperand() {
87     if (isBrList())
88       BrL.~BrLOp();
89   }
90 
91   bool isToken() const override { return Kind == Token; }
92   bool isImm() const override { return Kind == Integer || Kind == Symbol; }
93   bool isFPImm() const { return Kind == Float; }
94   bool isMem() const override { return false; }
95   bool isReg() const override { return false; }
96   bool isBrList() const { return Kind == BrList; }
97 
98   unsigned getReg() const override {
99     llvm_unreachable("Assembly inspects a register operand");
100     return 0;
101   }
102 
103   StringRef getToken() const {
104     assert(isToken());
105     return Tok.Tok;
106   }
107 
108   SMLoc getStartLoc() const override { return StartLoc; }
109   SMLoc getEndLoc() const override { return EndLoc; }
110 
111   void addRegOperands(MCInst &, unsigned) const {
112     // Required by the assembly matcher.
113     llvm_unreachable("Assembly matcher creates register operands");
114   }
115 
116   void addImmOperands(MCInst &Inst, unsigned N) const {
117     assert(N == 1 && "Invalid number of operands!");
118     if (Kind == Integer)
119       Inst.addOperand(MCOperand::createImm(Int.Val));
120     else if (Kind == Symbol)
121       Inst.addOperand(MCOperand::createExpr(Sym.Exp));
122     else
123       llvm_unreachable("Should be integer immediate or symbol!");
124   }
125 
126   void addFPImmOperands(MCInst &Inst, unsigned N) const {
127     assert(N == 1 && "Invalid number of operands!");
128     if (Kind == Float)
129       Inst.addOperand(MCOperand::createFPImm(Flt.Val));
130     else
131       llvm_unreachable("Should be float immediate!");
132   }
133 
134   void addBrListOperands(MCInst &Inst, unsigned N) const {
135     assert(N == 1 && isBrList() && "Invalid BrList!");
136     for (auto Br : BrL.List)
137       Inst.addOperand(MCOperand::createImm(Br));
138   }
139 
140   void print(raw_ostream &OS) const override {
141     switch (Kind) {
142     case Token:
143       OS << "Tok:" << Tok.Tok;
144       break;
145     case Integer:
146       OS << "Int:" << Int.Val;
147       break;
148     case Float:
149       OS << "Flt:" << Flt.Val;
150       break;
151     case Symbol:
152       OS << "Sym:" << Sym.Exp;
153       break;
154     case BrList:
155       OS << "BrList:" << BrL.List.size();
156       break;
157     }
158   }
159 };
160 
161 class WebAssemblyAsmParser final : public MCTargetAsmParser {
162   MCAsmParser &Parser;
163   MCAsmLexer &Lexer;
164 
165   // Much like WebAssemblyAsmPrinter in the backend, we have to own these.
166   std::vector<std::unique_ptr<wasm::WasmSignature>> Signatures;
167 
168   // Order of labels, directives and instructions in a .s file have no
169   // syntactical enforcement. This class is a callback from the actual parser,
170   // and yet we have to be feeding data to the streamer in a very particular
171   // order to ensure a correct binary encoding that matches the regular backend
172   // (the streamer does not enforce this). This "state machine" enum helps
173   // guarantee that correct order.
174   enum ParserState {
175     FileStart,
176     Label,
177     FunctionStart,
178     FunctionLocals,
179     Instructions,
180     EndFunction,
181     DataSection,
182   } CurrentState = FileStart;
183 
184   // For ensuring blocks are properly nested.
185   enum NestingType {
186     Function,
187     Block,
188     Loop,
189     Try,
190     If,
191     Else,
192     Undefined,
193   };
194   std::vector<NestingType> NestingStack;
195 
196   // We track this to see if a .functype following a label is the same,
197   // as this is how we recognize the start of a function.
198   MCSymbol *LastLabel = nullptr;
199   MCSymbol *LastFunctionLabel = nullptr;
200 
201 public:
202   WebAssemblyAsmParser(const MCSubtargetInfo &STI, MCAsmParser &Parser,
203                        const MCInstrInfo &MII, const MCTargetOptions &Options)
204       : MCTargetAsmParser(Options, STI, MII), Parser(Parser),
205         Lexer(Parser.getLexer()) {
206     setAvailableFeatures(ComputeAvailableFeatures(STI.getFeatureBits()));
207   }
208 
209 #define GET_ASSEMBLER_HEADER
210 #include "WebAssemblyGenAsmMatcher.inc"
211 
212   // TODO: This is required to be implemented, but appears unused.
213   bool ParseRegister(unsigned & /*RegNo*/, SMLoc & /*StartLoc*/,
214                      SMLoc & /*EndLoc*/) override {
215     llvm_unreachable("ParseRegister is not implemented.");
216   }
217 
218   bool error(const Twine &Msg, const AsmToken &Tok) {
219     return Parser.Error(Tok.getLoc(), Msg + Tok.getString());
220   }
221 
222   bool error(const Twine &Msg) {
223     return Parser.Error(Lexer.getTok().getLoc(), Msg);
224   }
225 
226   void addSignature(std::unique_ptr<wasm::WasmSignature> &&Sig) {
227     Signatures.push_back(std::move(Sig));
228   }
229 
230   std::pair<StringRef, StringRef> nestingString(NestingType NT) {
231     switch (NT) {
232     case Function:
233       return {"function", "end_function"};
234     case Block:
235       return {"block", "end_block"};
236     case Loop:
237       return {"loop", "end_loop"};
238     case Try:
239       return {"try", "end_try"};
240     case If:
241       return {"if", "end_if"};
242     case Else:
243       return {"else", "end_if"};
244     default:
245       llvm_unreachable("unknown NestingType");
246     }
247   }
248 
249   void push(NestingType NT) { NestingStack.push_back(NT); }
250 
251   bool pop(StringRef Ins, NestingType NT1, NestingType NT2 = Undefined) {
252     if (NestingStack.empty())
253       return error(Twine("End of block construct with no start: ") + Ins);
254     auto Top = NestingStack.back();
255     if (Top != NT1 && Top != NT2)
256       return error(Twine("Block construct type mismatch, expected: ") +
257                    nestingString(Top).second + ", instead got: " + Ins);
258     NestingStack.pop_back();
259     return false;
260   }
261 
262   bool ensureEmptyNestingStack() {
263     auto Err = !NestingStack.empty();
264     while (!NestingStack.empty()) {
265       error(Twine("Unmatched block construct(s) at function end: ") +
266             nestingString(NestingStack.back()).first);
267       NestingStack.pop_back();
268     }
269     return Err;
270   }
271 
272   bool isNext(AsmToken::TokenKind Kind) {
273     auto Ok = Lexer.is(Kind);
274     if (Ok)
275       Parser.Lex();
276     return Ok;
277   }
278 
279   bool expect(AsmToken::TokenKind Kind, const char *KindName) {
280     if (!isNext(Kind))
281       return error(std::string("Expected ") + KindName + ", instead got: ",
282                    Lexer.getTok());
283     return false;
284   }
285 
286   StringRef expectIdent() {
287     if (!Lexer.is(AsmToken::Identifier)) {
288       error("Expected identifier, got: ", Lexer.getTok());
289       return StringRef();
290     }
291     auto Name = Lexer.getTok().getString();
292     Parser.Lex();
293     return Name;
294   }
295 
296   Optional<wasm::ValType> parseType(const StringRef &Type) {
297     // FIXME: can't use StringSwitch because wasm::ValType doesn't have a
298     // "invalid" value.
299     if (Type == "i32")
300       return wasm::ValType::I32;
301     if (Type == "i64")
302       return wasm::ValType::I64;
303     if (Type == "f32")
304       return wasm::ValType::F32;
305     if (Type == "f64")
306       return wasm::ValType::F64;
307     if (Type == "v128" || Type == "i8x16" || Type == "i16x8" ||
308         Type == "i32x4" || Type == "i64x2" || Type == "f32x4" ||
309         Type == "f64x2")
310       return wasm::ValType::V128;
311     if (Type == "except_ref")
312       return wasm::ValType::EXCEPT_REF;
313     return Optional<wasm::ValType>();
314   }
315 
316   WebAssembly::ExprType parseBlockType(StringRef ID) {
317     return StringSwitch<WebAssembly::ExprType>(ID)
318         .Case("i32", WebAssembly::ExprType::I32)
319         .Case("i64", WebAssembly::ExprType::I64)
320         .Case("f32", WebAssembly::ExprType::F32)
321         .Case("f64", WebAssembly::ExprType::F64)
322         .Case("v128", WebAssembly::ExprType::V128)
323         .Case("except_ref", WebAssembly::ExprType::ExceptRef)
324         .Case("void", WebAssembly::ExprType::Void)
325         .Default(WebAssembly::ExprType::Invalid);
326   }
327 
328   bool parseRegTypeList(SmallVectorImpl<wasm::ValType> &Types) {
329     while (Lexer.is(AsmToken::Identifier)) {
330       auto Type = parseType(Lexer.getTok().getString());
331       if (!Type)
332         return error("unknown type: ", Lexer.getTok());
333       Types.push_back(Type.getValue());
334       Parser.Lex();
335       if (!isNext(AsmToken::Comma))
336         break;
337     }
338     return false;
339   }
340 
341   void parseSingleInteger(bool IsNegative, OperandVector &Operands) {
342     auto &Int = Lexer.getTok();
343     int64_t Val = Int.getIntVal();
344     if (IsNegative)
345       Val = -Val;
346     Operands.push_back(make_unique<WebAssemblyOperand>(
347         WebAssemblyOperand::Integer, Int.getLoc(), Int.getEndLoc(),
348         WebAssemblyOperand::IntOp{Val}));
349     Parser.Lex();
350   }
351 
352   bool checkForP2AlignIfLoadStore(OperandVector &Operands, StringRef InstName) {
353     // FIXME: there is probably a cleaner way to do this.
354     auto IsLoadStore = InstName.find(".load") != StringRef::npos ||
355                        InstName.find(".store") != StringRef::npos;
356     auto IsAtomic = InstName.find("atomic.") != StringRef::npos;
357     if (IsLoadStore || IsAtomic) {
358       // Parse load/store operands of the form: offset:p2align=align
359       if (IsLoadStore && isNext(AsmToken::Colon)) {
360         auto Id = expectIdent();
361         if (Id != "p2align")
362           return error("Expected p2align, instead got: " + Id);
363         if (expect(AsmToken::Equal, "="))
364           return true;
365         if (!Lexer.is(AsmToken::Integer))
366           return error("Expected integer constant");
367         parseSingleInteger(false, Operands);
368       } else {
369         // Alignment not specified (or atomics, must use default alignment).
370         // We can't just call WebAssembly::GetDefaultP2Align since we don't have
371         // an opcode until after the assembly matcher, so set a default to fix
372         // up later.
373         auto Tok = Lexer.getTok();
374         Operands.push_back(make_unique<WebAssemblyOperand>(
375             WebAssemblyOperand::Integer, Tok.getLoc(), Tok.getEndLoc(),
376             WebAssemblyOperand::IntOp{-1}));
377       }
378     }
379     return false;
380   }
381 
382   void addBlockTypeOperand(OperandVector &Operands, SMLoc NameLoc,
383                            WebAssembly::ExprType BT) {
384     Operands.push_back(make_unique<WebAssemblyOperand>(
385         WebAssemblyOperand::Integer, NameLoc, NameLoc,
386         WebAssemblyOperand::IntOp{static_cast<int64_t>(BT)}));
387   }
388 
389   bool ParseInstruction(ParseInstructionInfo & /*Info*/, StringRef Name,
390                         SMLoc NameLoc, OperandVector &Operands) override {
391     // Note: Name does NOT point into the sourcecode, but to a local, so
392     // use NameLoc instead.
393     Name = StringRef(NameLoc.getPointer(), Name.size());
394 
395     // WebAssembly has instructions with / in them, which AsmLexer parses
396     // as seperate tokens, so if we find such tokens immediately adjacent (no
397     // whitespace), expand the name to include them:
398     for (;;) {
399       auto &Sep = Lexer.getTok();
400       if (Sep.getLoc().getPointer() != Name.end() ||
401           Sep.getKind() != AsmToken::Slash)
402         break;
403       // Extend name with /
404       Name = StringRef(Name.begin(), Name.size() + Sep.getString().size());
405       Parser.Lex();
406       // We must now find another identifier, or error.
407       auto &Id = Lexer.getTok();
408       if (Id.getKind() != AsmToken::Identifier ||
409           Id.getLoc().getPointer() != Name.end())
410         return error("Incomplete instruction name: ", Id);
411       Name = StringRef(Name.begin(), Name.size() + Id.getString().size());
412       Parser.Lex();
413     }
414 
415     // Now construct the name as first operand.
416     Operands.push_back(make_unique<WebAssemblyOperand>(
417         WebAssemblyOperand::Token, NameLoc, SMLoc::getFromPointer(Name.end()),
418         WebAssemblyOperand::TokOp{Name}));
419 
420     // If this instruction is part of a control flow structure, ensure
421     // proper nesting.
422     bool ExpectBlockType = false;
423     if (Name == "block") {
424       push(Block);
425       ExpectBlockType = true;
426     } else if (Name == "loop") {
427       push(Loop);
428       ExpectBlockType = true;
429     } else if (Name == "try") {
430       push(Try);
431       ExpectBlockType = true;
432     } else if (Name == "if") {
433       push(If);
434       ExpectBlockType = true;
435     } else if (Name == "else") {
436       if (pop(Name, If))
437         return true;
438       push(Else);
439     } else if (Name == "catch") {
440       if (pop(Name, Try))
441         return true;
442       push(Try);
443     } else if (Name == "end_if") {
444       if (pop(Name, If, Else))
445         return true;
446     } else if (Name == "end_try") {
447       if (pop(Name, Try))
448         return true;
449     } else if (Name == "end_loop") {
450       if (pop(Name, Loop))
451         return true;
452     } else if (Name == "end_block") {
453       if (pop(Name, Block))
454         return true;
455     } else if (Name == "end_function") {
456       CurrentState = EndFunction;
457       if (pop(Name, Function) || ensureEmptyNestingStack())
458         return true;
459     }
460 
461     while (Lexer.isNot(AsmToken::EndOfStatement)) {
462       auto &Tok = Lexer.getTok();
463       switch (Tok.getKind()) {
464       case AsmToken::Identifier: {
465         auto &Id = Lexer.getTok();
466         if (ExpectBlockType) {
467           // Assume this identifier is a block_type.
468           auto BT = parseBlockType(Id.getString());
469           if (BT == WebAssembly::ExprType::Invalid)
470             return error("Unknown block type: ", Id);
471           addBlockTypeOperand(Operands, NameLoc, BT);
472           Parser.Lex();
473         } else {
474           // Assume this identifier is a label.
475           const MCExpr *Val;
476           SMLoc End;
477           if (Parser.parseExpression(Val, End))
478             return error("Cannot parse symbol: ", Lexer.getTok());
479           Operands.push_back(make_unique<WebAssemblyOperand>(
480               WebAssemblyOperand::Symbol, Id.getLoc(), Id.getEndLoc(),
481               WebAssemblyOperand::SymOp{Val}));
482           if (checkForP2AlignIfLoadStore(Operands, Name))
483             return true;
484         }
485         break;
486       }
487       case AsmToken::Minus:
488         Parser.Lex();
489         if (Lexer.isNot(AsmToken::Integer))
490           return error("Expected integer instead got: ", Lexer.getTok());
491         parseSingleInteger(true, Operands);
492         if (checkForP2AlignIfLoadStore(Operands, Name))
493           return true;
494         break;
495       case AsmToken::Integer:
496         parseSingleInteger(false, Operands);
497         if (checkForP2AlignIfLoadStore(Operands, Name))
498           return true;
499         break;
500       case AsmToken::Real: {
501         double Val;
502         if (Tok.getString().getAsDouble(Val, false))
503           return error("Cannot parse real: ", Tok);
504         Operands.push_back(make_unique<WebAssemblyOperand>(
505             WebAssemblyOperand::Float, Tok.getLoc(), Tok.getEndLoc(),
506             WebAssemblyOperand::FltOp{Val}));
507         Parser.Lex();
508         break;
509       }
510       case AsmToken::LCurly: {
511         Parser.Lex();
512         auto Op = make_unique<WebAssemblyOperand>(
513             WebAssemblyOperand::BrList, Tok.getLoc(), Tok.getEndLoc());
514         if (!Lexer.is(AsmToken::RCurly))
515           for (;;) {
516             Op->BrL.List.push_back(Lexer.getTok().getIntVal());
517             expect(AsmToken::Integer, "integer");
518             if (!isNext(AsmToken::Comma))
519               break;
520           }
521         expect(AsmToken::RCurly, "}");
522         Operands.push_back(std::move(Op));
523         break;
524       }
525       default:
526         return error("Unexpected token in operand: ", Tok);
527       }
528       if (Lexer.isNot(AsmToken::EndOfStatement)) {
529         if (expect(AsmToken::Comma, ","))
530           return true;
531       }
532     }
533     if (ExpectBlockType && Operands.size() == 1) {
534       // Support blocks with no operands as default to void.
535       addBlockTypeOperand(Operands, NameLoc, WebAssembly::ExprType::Void);
536     }
537     Parser.Lex();
538     return false;
539   }
540 
541   void onLabelParsed(MCSymbol *Symbol) override {
542     LastLabel = Symbol;
543     CurrentState = Label;
544   }
545 
546   bool parseSignature(wasm::WasmSignature *Signature) {
547     if (expect(AsmToken::LParen, "("))
548       return true;
549     if (parseRegTypeList(Signature->Params))
550       return true;
551     if (expect(AsmToken::RParen, ")"))
552       return true;
553     if (expect(AsmToken::MinusGreater, "->"))
554       return true;
555     if (expect(AsmToken::LParen, "("))
556       return true;
557     if (parseRegTypeList(Signature->Returns))
558       return true;
559     if (expect(AsmToken::RParen, ")"))
560       return true;
561     return false;
562   }
563 
564   bool CheckDataSection() {
565     if (CurrentState != DataSection) {
566       auto WS = cast<MCSectionWasm>(getStreamer().getCurrentSection().first);
567       if (WS && WS->getKind().isText())
568         return error("data directive must occur in a data segment: ",
569                      Lexer.getTok());
570     }
571     CurrentState = DataSection;
572     return false;
573   }
574 
575   // This function processes wasm-specific directives streamed to
576   // WebAssemblyTargetStreamer, all others go to the generic parser
577   // (see WasmAsmParser).
578   bool ParseDirective(AsmToken DirectiveID) override {
579     // This function has a really weird return value behavior that is different
580     // from all the other parsing functions:
581     // - return true && no tokens consumed -> don't know this directive / let
582     //   the generic parser handle it.
583     // - return true && tokens consumed -> a parsing error occurred.
584     // - return false -> processed this directive successfully.
585     assert(DirectiveID.getKind() == AsmToken::Identifier);
586     auto &Out = getStreamer();
587     auto &TOut =
588         reinterpret_cast<WebAssemblyTargetStreamer &>(*Out.getTargetStreamer());
589     auto &Ctx = Out.getContext();
590 
591     // TODO: any time we return an error, at least one token must have been
592     // consumed, otherwise this will not signal an error to the caller.
593     if (DirectiveID.getString() == ".globaltype") {
594       auto SymName = expectIdent();
595       if (SymName.empty())
596         return true;
597       if (expect(AsmToken::Comma, ","))
598         return true;
599       auto TypeTok = Lexer.getTok();
600       auto TypeName = expectIdent();
601       if (TypeName.empty())
602         return true;
603       auto Type = parseType(TypeName);
604       if (!Type)
605         return error("Unknown type in .globaltype directive: ", TypeTok);
606       // Now set this symbol with the correct type.
607       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
608       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
609       WasmSym->setGlobalType(
610           wasm::WasmGlobalType{uint8_t(Type.getValue()), true});
611       // And emit the directive again.
612       TOut.emitGlobalType(WasmSym);
613       return expect(AsmToken::EndOfStatement, "EOL");
614     }
615 
616     if (DirectiveID.getString() == ".functype") {
617       // This code has to send things to the streamer similar to
618       // WebAssemblyAsmPrinter::EmitFunctionBodyStart.
619       // TODO: would be good to factor this into a common function, but the
620       // assembler and backend really don't share any common code, and this code
621       // parses the locals seperately.
622       auto SymName = expectIdent();
623       if (SymName.empty())
624         return true;
625       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
626       if (CurrentState == Label && WasmSym == LastLabel) {
627         // This .functype indicates a start of a function.
628         if (ensureEmptyNestingStack())
629           return true;
630         CurrentState = FunctionStart;
631         LastFunctionLabel = LastLabel;
632         push(Function);
633       }
634       auto Signature = make_unique<wasm::WasmSignature>();
635       if (parseSignature(Signature.get()))
636         return true;
637       WasmSym->setSignature(Signature.get());
638       addSignature(std::move(Signature));
639       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
640       TOut.emitFunctionType(WasmSym);
641       // TODO: backend also calls TOut.emitIndIdx, but that is not implemented.
642       return expect(AsmToken::EndOfStatement, "EOL");
643     }
644 
645     if (DirectiveID.getString() == ".eventtype") {
646       auto SymName = expectIdent();
647       if (SymName.empty())
648         return true;
649       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
650       auto Signature = make_unique<wasm::WasmSignature>();
651       if (parseRegTypeList(Signature->Params))
652         return true;
653       WasmSym->setSignature(Signature.get());
654       addSignature(std::move(Signature));
655       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_EVENT);
656       TOut.emitEventType(WasmSym);
657       // TODO: backend also calls TOut.emitIndIdx, but that is not implemented.
658       return expect(AsmToken::EndOfStatement, "EOL");
659     }
660 
661     if (DirectiveID.getString() == ".local") {
662       if (CurrentState != FunctionStart)
663         return error(".local directive should follow the start of a function",
664                      Lexer.getTok());
665       SmallVector<wasm::ValType, 4> Locals;
666       if (parseRegTypeList(Locals))
667         return true;
668       TOut.emitLocal(Locals);
669       CurrentState = FunctionLocals;
670       return expect(AsmToken::EndOfStatement, "EOL");
671     }
672 
673     if (DirectiveID.getString() == ".int8" ||
674         DirectiveID.getString() == ".int16" ||
675         DirectiveID.getString() == ".int32" ||
676         DirectiveID.getString() == ".int64") {
677       if (CheckDataSection()) return true;
678       const MCExpr *Val;
679       SMLoc End;
680       if (Parser.parseExpression(Val, End))
681         return error("Cannot parse .int expression: ", Lexer.getTok());
682       size_t NumBits = 0;
683       DirectiveID.getString().drop_front(4).getAsInteger(10, NumBits);
684       Out.EmitValue(Val, NumBits / 8, End);
685       return expect(AsmToken::EndOfStatement, "EOL");
686     }
687 
688     if (DirectiveID.getString() == ".asciz") {
689       if (CheckDataSection()) return true;
690       std::string S;
691       if (Parser.parseEscapedString(S))
692         return error("Cannot parse string constant: ", Lexer.getTok());
693       Out.EmitBytes(StringRef(S.c_str(), S.length() + 1));
694       return expect(AsmToken::EndOfStatement, "EOL");
695     }
696 
697     return true; // We didn't process this directive.
698   }
699 
700   bool MatchAndEmitInstruction(SMLoc IDLoc, unsigned & /*Opcode*/,
701                                OperandVector &Operands, MCStreamer &Out,
702                                uint64_t &ErrorInfo,
703                                bool MatchingInlineAsm) override {
704     MCInst Inst;
705     unsigned MatchResult =
706         MatchInstructionImpl(Operands, Inst, ErrorInfo, MatchingInlineAsm);
707     switch (MatchResult) {
708     case Match_Success: {
709       if (CurrentState == FunctionStart) {
710         // This is the first instruction in a function, but we haven't seen
711         // a .local directive yet. The streamer requires locals to be encoded
712         // as a prelude to the instructions, so emit an empty list of locals
713         // here.
714         auto &TOut = reinterpret_cast<WebAssemblyTargetStreamer &>(
715             *Out.getTargetStreamer());
716         TOut.emitLocal(SmallVector<wasm::ValType, 0>());
717       }
718       // Fix unknown p2align operands.
719       auto Align = WebAssembly::GetDefaultP2AlignAny(Inst.getOpcode());
720       if (Align != -1U) {
721         auto &Op0 = Inst.getOperand(0);
722         if (Op0.getImm() == -1)
723           Op0.setImm(Align);
724       }
725       Out.EmitInstruction(Inst, getSTI());
726       if (CurrentState == EndFunction) {
727         onEndOfFunction();
728       } else {
729         CurrentState = Instructions;
730       }
731       return false;
732     }
733     case Match_MissingFeature:
734       return Parser.Error(
735           IDLoc, "instruction requires a WASM feature not currently enabled");
736     case Match_MnemonicFail:
737       return Parser.Error(IDLoc, "invalid instruction");
738     case Match_NearMisses:
739       return Parser.Error(IDLoc, "ambiguous instruction");
740     case Match_InvalidTiedOperand:
741     case Match_InvalidOperand: {
742       SMLoc ErrorLoc = IDLoc;
743       if (ErrorInfo != ~0ULL) {
744         if (ErrorInfo >= Operands.size())
745           return Parser.Error(IDLoc, "too few operands for instruction");
746         ErrorLoc = Operands[ErrorInfo]->getStartLoc();
747         if (ErrorLoc == SMLoc())
748           ErrorLoc = IDLoc;
749       }
750       return Parser.Error(ErrorLoc, "invalid operand for instruction");
751     }
752     }
753     llvm_unreachable("Implement any new match types added!");
754   }
755 
756   void doBeforeLabelEmit(MCSymbol *Symbol) override {
757     // Start a new section for the next function automatically, since our
758     // object writer expects each function to have its own section. This way
759     // The user can't forget this "convention".
760     auto SymName = Symbol->getName();
761     if (SymName.startswith(".L"))
762       return; // Local Symbol.
763     // Only create a new text section if we're already in one.
764     auto CWS = cast<MCSectionWasm>(getStreamer().getCurrentSection().first);
765     if (!CWS || !CWS->getKind().isText())
766       return;
767     auto SecName = ".text." + SymName;
768     auto WS = getContext().getWasmSection(SecName, SectionKind::getText());
769     getStreamer().SwitchSection(WS);
770   }
771 
772   void onEndOfFunction() {
773     // Automatically output a .size directive, so it becomes optional for the
774     // user.
775     if (!LastFunctionLabel) return;
776     auto TempSym = getContext().createLinkerPrivateTempSymbol();
777     getStreamer().EmitLabel(TempSym);
778     auto Start = MCSymbolRefExpr::create(LastFunctionLabel, getContext());
779     auto End = MCSymbolRefExpr::create(TempSym, getContext());
780     auto Expr =
781         MCBinaryExpr::create(MCBinaryExpr::Sub, End, Start, getContext());
782     getStreamer().emitELFSize(LastFunctionLabel, Expr);
783   }
784 
785   void onEndOfFile() override { ensureEmptyNestingStack(); }
786 };
787 } // end anonymous namespace
788 
789 // Force static initialization.
790 extern "C" void LLVMInitializeWebAssemblyAsmParser() {
791   RegisterMCAsmParser<WebAssemblyAsmParser> X(getTheWebAssemblyTarget32());
792   RegisterMCAsmParser<WebAssemblyAsmParser> Y(getTheWebAssemblyTarget64());
793 }
794 
795 #define GET_REGISTER_MATCHER
796 #define GET_MATCHER_IMPLEMENTATION
797 #include "WebAssemblyGenAsmMatcher.inc"
798