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