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");
352     if (IsLoadStore) {
353       // Parse load/store operands of the form: offset align
354       auto &Offset = Lexer.getTok();
355       if (Offset.is(AsmToken::Integer)) {
356         parseSingleInteger(false, Operands);
357       } else {
358         // Alignment not specified.
359         // FIXME: correctly derive a default from the instruction.
360         // We can't just call WebAssembly::GetDefaultP2Align since we don't have
361         // an opcode until after the assembly matcher.
362         Operands.push_back(make_unique<WebAssemblyOperand>(
363             WebAssemblyOperand::Integer, Offset.getLoc(), Offset.getEndLoc(),
364             WebAssemblyOperand::IntOp{0}));
365       }
366     }
367     return false;
368   }
369 
370   void addBlockTypeOperand(OperandVector &Operands, SMLoc NameLoc,
371                            WebAssembly::ExprType BT) {
372     Operands.push_back(make_unique<WebAssemblyOperand>(
373         WebAssemblyOperand::Integer, NameLoc, NameLoc,
374         WebAssemblyOperand::IntOp{static_cast<int64_t>(BT)}));
375   }
376 
377   bool ParseInstruction(ParseInstructionInfo & /*Info*/, StringRef Name,
378                         SMLoc NameLoc, OperandVector &Operands) override {
379     // Note: Name does NOT point into the sourcecode, but to a local, so
380     // use NameLoc instead.
381     Name = StringRef(NameLoc.getPointer(), Name.size());
382 
383     // WebAssembly has instructions with / in them, which AsmLexer parses
384     // as seperate tokens, so if we find such tokens immediately adjacent (no
385     // whitespace), expand the name to include them:
386     for (;;) {
387       auto &Sep = Lexer.getTok();
388       if (Sep.getLoc().getPointer() != Name.end() ||
389           Sep.getKind() != AsmToken::Slash)
390         break;
391       // Extend name with /
392       Name = StringRef(Name.begin(), Name.size() + Sep.getString().size());
393       Parser.Lex();
394       // We must now find another identifier, or error.
395       auto &Id = Lexer.getTok();
396       if (Id.getKind() != AsmToken::Identifier ||
397           Id.getLoc().getPointer() != Name.end())
398         return error("Incomplete instruction name: ", Id);
399       Name = StringRef(Name.begin(), Name.size() + Id.getString().size());
400       Parser.Lex();
401     }
402 
403     // Now construct the name as first operand.
404     Operands.push_back(make_unique<WebAssemblyOperand>(
405         WebAssemblyOperand::Token, NameLoc, SMLoc::getFromPointer(Name.end()),
406         WebAssemblyOperand::TokOp{Name}));
407     auto NamePair = Name.split('.');
408     // If no '.', there is no type prefix.
409     auto BaseName = NamePair.second.empty() ? NamePair.first : NamePair.second;
410 
411     // If this instruction is part of a control flow structure, ensure
412     // proper nesting.
413     bool ExpectBlockType = false;
414     if (BaseName == "block") {
415       push(Block);
416       ExpectBlockType = true;
417     } else if (BaseName == "loop") {
418       push(Loop);
419       ExpectBlockType = true;
420     } else if (BaseName == "try") {
421       push(Try);
422       ExpectBlockType = true;
423     } else if (BaseName == "if") {
424       push(If);
425       ExpectBlockType = true;
426     } else if (BaseName == "else") {
427       if (pop(BaseName, If))
428         return true;
429       push(Else);
430     } else if (BaseName == "catch") {
431       if (pop(BaseName, Try))
432         return true;
433       push(Try);
434     } else if (BaseName == "catch_all") {
435       if (pop(BaseName, Try))
436         return true;
437       push(Try);
438     } else if (BaseName == "end_if") {
439       if (pop(BaseName, If, Else))
440         return true;
441     } else if (BaseName == "end_try") {
442       if (pop(BaseName, Try))
443         return true;
444     } else if (BaseName == "end_loop") {
445       if (pop(BaseName, Loop))
446         return true;
447     } else if (BaseName == "end_block") {
448       if (pop(BaseName, Block))
449         return true;
450     } else if (BaseName == "end_function") {
451       CurrentState = EndFunction;
452       if (pop(BaseName, Function) || ensureEmptyNestingStack())
453         return true;
454     }
455 
456     while (Lexer.isNot(AsmToken::EndOfStatement)) {
457       auto &Tok = Lexer.getTok();
458       switch (Tok.getKind()) {
459       case AsmToken::Identifier: {
460         auto &Id = Lexer.getTok();
461         if (ExpectBlockType) {
462           // Assume this identifier is a block_type.
463           auto BT = parseBlockType(Id.getString());
464           if (BT == WebAssembly::ExprType::Invalid)
465             return error("Unknown block type: ", Id);
466           addBlockTypeOperand(Operands, NameLoc, BT);
467           Parser.Lex();
468         } else {
469           // Assume this identifier is a label.
470           const MCExpr *Val;
471           SMLoc End;
472           if (Parser.parsePrimaryExpr(Val, End))
473             return error("Cannot parse symbol: ", Lexer.getTok());
474           Operands.push_back(make_unique<WebAssemblyOperand>(
475               WebAssemblyOperand::Symbol, Id.getLoc(), Id.getEndLoc(),
476               WebAssemblyOperand::SymOp{Val}));
477         }
478         break;
479       }
480       case AsmToken::Minus:
481         Parser.Lex();
482         if (Lexer.isNot(AsmToken::Integer))
483           return error("Expected integer instead got: ", Lexer.getTok());
484         if (parseOperandStartingWithInteger(true, Operands, BaseName))
485           return true;
486         break;
487       case AsmToken::Integer:
488         if (parseOperandStartingWithInteger(false, Operands, BaseName))
489           return true;
490         break;
491       case AsmToken::Real: {
492         double Val;
493         if (Tok.getString().getAsDouble(Val, false))
494           return error("Cannot parse real: ", Tok);
495         Operands.push_back(make_unique<WebAssemblyOperand>(
496             WebAssemblyOperand::Float, Tok.getLoc(), Tok.getEndLoc(),
497             WebAssemblyOperand::FltOp{Val}));
498         Parser.Lex();
499         break;
500       }
501       case AsmToken::LCurly: {
502         Parser.Lex();
503         auto Op = make_unique<WebAssemblyOperand>(
504             WebAssemblyOperand::BrList, Tok.getLoc(), Tok.getEndLoc());
505         if (!Lexer.is(AsmToken::RCurly))
506           for (;;) {
507             Op->BrL.List.push_back(Lexer.getTok().getIntVal());
508             expect(AsmToken::Integer, "integer");
509             if (!isNext(AsmToken::Comma))
510               break;
511           }
512         expect(AsmToken::RCurly, "}");
513         Operands.push_back(std::move(Op));
514         break;
515       }
516       default:
517         return error("Unexpected token in operand: ", Tok);
518       }
519       if (Lexer.isNot(AsmToken::EndOfStatement)) {
520         if (expect(AsmToken::Comma, ","))
521           return true;
522       }
523     }
524     if (ExpectBlockType && Operands.size() == 1) {
525       // Support blocks with no operands as default to void.
526       addBlockTypeOperand(Operands, NameLoc, WebAssembly::ExprType::Void);
527     }
528     Parser.Lex();
529     return false;
530   }
531 
532   void onLabelParsed(MCSymbol *Symbol) override {
533     LastLabel = Symbol;
534     CurrentState = Label;
535   }
536 
537   bool parseSignature(wasm::WasmSignature *Signature) {
538     if (expect(AsmToken::LParen, "("))
539       return true;
540     if (parseRegTypeList(Signature->Params))
541       return true;
542     if (expect(AsmToken::RParen, ")"))
543       return true;
544     if (expect(AsmToken::MinusGreater, "->"))
545       return true;
546     if (expect(AsmToken::LParen, "("))
547       return true;
548     if (parseRegTypeList(Signature->Returns))
549       return true;
550     if (expect(AsmToken::RParen, ")"))
551       return true;
552     return false;
553   }
554 
555   // This function processes wasm-specific directives streamed to
556   // WebAssemblyTargetStreamer, all others go to the generic parser
557   // (see WasmAsmParser).
558   bool ParseDirective(AsmToken DirectiveID) override {
559     // This function has a really weird return value behavior that is different
560     // from all the other parsing functions:
561     // - return true && no tokens consumed -> don't know this directive / let
562     //   the generic parser handle it.
563     // - return true && tokens consumed -> a parsing error occurred.
564     // - return false -> processed this directive successfully.
565     assert(DirectiveID.getKind() == AsmToken::Identifier);
566     auto &Out = getStreamer();
567     auto &TOut =
568         reinterpret_cast<WebAssemblyTargetStreamer &>(*Out.getTargetStreamer());
569     auto &Ctx = Out.getContext();
570 
571     // TODO: any time we return an error, at least one token must have been
572     // consumed, otherwise this will not signal an error to the caller.
573     if (DirectiveID.getString() == ".globaltype") {
574       auto SymName = expectIdent();
575       if (SymName.empty())
576         return true;
577       if (expect(AsmToken::Comma, ","))
578         return true;
579       auto TypeTok = Lexer.getTok();
580       auto TypeName = expectIdent();
581       if (TypeName.empty())
582         return true;
583       auto Type = parseType(TypeName);
584       if (!Type)
585         return error("Unknown type in .globaltype directive: ", TypeTok);
586       // Now set this symbol with the correct type.
587       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
588       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
589       WasmSym->setGlobalType(
590           wasm::WasmGlobalType{uint8_t(Type.getValue()), true});
591       // And emit the directive again.
592       TOut.emitGlobalType(WasmSym);
593       return expect(AsmToken::EndOfStatement, "EOL");
594     }
595 
596     if (DirectiveID.getString() == ".functype") {
597       // This code has to send things to the streamer similar to
598       // WebAssemblyAsmPrinter::EmitFunctionBodyStart.
599       // TODO: would be good to factor this into a common function, but the
600       // assembler and backend really don't share any common code, and this code
601       // parses the locals seperately.
602       auto SymName = expectIdent();
603       if (SymName.empty())
604         return true;
605       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
606       if (CurrentState == Label && WasmSym == LastLabel) {
607         // This .functype indicates a start of a function.
608         if (ensureEmptyNestingStack())
609           return true;
610         CurrentState = FunctionStart;
611         LastFunctionLabel = LastLabel;
612         push(Function);
613       }
614       auto Signature = make_unique<wasm::WasmSignature>();
615       if (parseSignature(Signature.get()))
616         return true;
617       WasmSym->setSignature(Signature.get());
618       addSignature(std::move(Signature));
619       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
620       TOut.emitFunctionType(WasmSym);
621       // TODO: backend also calls TOut.emitIndIdx, but that is not implemented.
622       return expect(AsmToken::EndOfStatement, "EOL");
623     }
624 
625     if (DirectiveID.getString() == ".eventtype") {
626       auto SymName = expectIdent();
627       if (SymName.empty())
628         return true;
629       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
630       auto Signature = make_unique<wasm::WasmSignature>();
631       if (parseRegTypeList(Signature->Params))
632         return true;
633       WasmSym->setSignature(Signature.get());
634       addSignature(std::move(Signature));
635       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_EVENT);
636       TOut.emitEventType(WasmSym);
637       // TODO: backend also calls TOut.emitIndIdx, but that is not implemented.
638       return expect(AsmToken::EndOfStatement, "EOL");
639     }
640 
641     if (DirectiveID.getString() == ".local") {
642       if (CurrentState != FunctionStart)
643         return error(".local directive should follow the start of a function",
644                      Lexer.getTok());
645       SmallVector<wasm::ValType, 4> Locals;
646       if (parseRegTypeList(Locals))
647         return true;
648       TOut.emitLocal(Locals);
649       CurrentState = FunctionLocals;
650       return expect(AsmToken::EndOfStatement, "EOL");
651     }
652 
653     return true; // We didn't process this directive.
654   }
655 
656   bool MatchAndEmitInstruction(SMLoc IDLoc, unsigned & /*Opcode*/,
657                                OperandVector &Operands, MCStreamer &Out,
658                                uint64_t &ErrorInfo,
659                                bool MatchingInlineAsm) override {
660     MCInst Inst;
661     unsigned MatchResult =
662         MatchInstructionImpl(Operands, Inst, ErrorInfo, MatchingInlineAsm);
663     switch (MatchResult) {
664     case Match_Success: {
665       if (CurrentState == FunctionStart) {
666         // This is the first instruction in a function, but we haven't seen
667         // a .local directive yet. The streamer requires locals to be encoded
668         // as a prelude to the instructions, so emit an empty list of locals
669         // here.
670         auto &TOut = reinterpret_cast<WebAssemblyTargetStreamer &>(
671             *Out.getTargetStreamer());
672         TOut.emitLocal(SmallVector<wasm::ValType, 0>());
673       }
674       Out.EmitInstruction(Inst, getSTI());
675       if (CurrentState == EndFunction) {
676         onEndOfFunction();
677       } else {
678         CurrentState = Instructions;
679       }
680       return false;
681     }
682     case Match_MissingFeature:
683       return Parser.Error(
684           IDLoc, "instruction requires a WASM feature not currently enabled");
685     case Match_MnemonicFail:
686       return Parser.Error(IDLoc, "invalid instruction");
687     case Match_NearMisses:
688       return Parser.Error(IDLoc, "ambiguous instruction");
689     case Match_InvalidTiedOperand:
690     case Match_InvalidOperand: {
691       SMLoc ErrorLoc = IDLoc;
692       if (ErrorInfo != ~0ULL) {
693         if (ErrorInfo >= Operands.size())
694           return Parser.Error(IDLoc, "too few operands for instruction");
695         ErrorLoc = Operands[ErrorInfo]->getStartLoc();
696         if (ErrorLoc == SMLoc())
697           ErrorLoc = IDLoc;
698       }
699       return Parser.Error(ErrorLoc, "invalid operand for instruction");
700     }
701     }
702     llvm_unreachable("Implement any new match types added!");
703   }
704 
705   void doBeforeLabelEmit(MCSymbol *Symbol) override {
706     // Start a new section for the next function automatically, since our
707     // object writer expects each function to have its own section. This way
708     // The user can't forget this "convention".
709     auto SymName = Symbol->getName();
710     if (SymName.startswith(".L"))
711       return; // Local Symbol.
712     auto SecName = ".text." + SymName;
713     auto WS = getContext().getWasmSection(SecName, SectionKind::getText());
714     getStreamer().SwitchSection(WS);
715   }
716 
717   void onEndOfFunction() {
718     // Automatically output a .size directive, so it becomes optional for the
719     // user.
720     auto TempSym = getContext().createLinkerPrivateTempSymbol();
721     getStreamer().EmitLabel(TempSym);
722     auto Start = MCSymbolRefExpr::create(LastLabel, getContext());
723     auto End = MCSymbolRefExpr::create(TempSym, getContext());
724     auto Expr =
725         MCBinaryExpr::create(MCBinaryExpr::Sub, End, Start, getContext());
726     getStreamer().emitELFSize(LastFunctionLabel, Expr);
727   }
728 
729   void onEndOfFile() override { ensureEmptyNestingStack(); }
730 };
731 } // end anonymous namespace
732 
733 // Force static initialization.
734 extern "C" void LLVMInitializeWebAssemblyAsmParser() {
735   RegisterMCAsmParser<WebAssemblyAsmParser> X(getTheWebAssemblyTarget32());
736   RegisterMCAsmParser<WebAssemblyAsmParser> Y(getTheWebAssemblyTarget64());
737 }
738 
739 #define GET_REGISTER_MATCHER
740 #define GET_MATCHER_IMPLEMENTATION
741 #include "WebAssemblyGenAsmMatcher.inc"
742