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 == "exnref")
312       return wasm::ValType::EXNREF;
313     return Optional<wasm::ValType>();
314   }
315 
316   WebAssembly::BlockType parseBlockType(StringRef ID) {
317     // Multivalue block types are handled separately in parseSignature
318     return StringSwitch<WebAssembly::BlockType>(ID)
319         .Case("i32", WebAssembly::BlockType::I32)
320         .Case("i64", WebAssembly::BlockType::I64)
321         .Case("f32", WebAssembly::BlockType::F32)
322         .Case("f64", WebAssembly::BlockType::F64)
323         .Case("v128", WebAssembly::BlockType::V128)
324         .Case("exnref", WebAssembly::BlockType::Exnref)
325         .Case("void", WebAssembly::BlockType::Void)
326         .Default(WebAssembly::BlockType::Invalid);
327   }
328 
329   bool parseRegTypeList(SmallVectorImpl<wasm::ValType> &Types) {
330     while (Lexer.is(AsmToken::Identifier)) {
331       auto Type = parseType(Lexer.getTok().getString());
332       if (!Type)
333         return error("unknown type: ", Lexer.getTok());
334       Types.push_back(Type.getValue());
335       Parser.Lex();
336       if (!isNext(AsmToken::Comma))
337         break;
338     }
339     return false;
340   }
341 
342   void parseSingleInteger(bool IsNegative, OperandVector &Operands) {
343     auto &Int = Lexer.getTok();
344     int64_t Val = Int.getIntVal();
345     if (IsNegative)
346       Val = -Val;
347     Operands.push_back(std::make_unique<WebAssemblyOperand>(
348         WebAssemblyOperand::Integer, Int.getLoc(), Int.getEndLoc(),
349         WebAssemblyOperand::IntOp{Val}));
350     Parser.Lex();
351   }
352 
353   bool parseSingleFloat(bool IsNegative, OperandVector &Operands) {
354     auto &Flt = Lexer.getTok();
355     double Val;
356     if (Flt.getString().getAsDouble(Val, false))
357       return error("Cannot parse real: ", Flt);
358     if (IsNegative)
359       Val = -Val;
360     Operands.push_back(std::make_unique<WebAssemblyOperand>(
361         WebAssemblyOperand::Float, Flt.getLoc(), Flt.getEndLoc(),
362         WebAssemblyOperand::FltOp{Val}));
363     Parser.Lex();
364     return false;
365   }
366 
367   bool parseSpecialFloatMaybe(bool IsNegative, OperandVector &Operands) {
368     if (Lexer.isNot(AsmToken::Identifier))
369       return true;
370     auto &Flt = Lexer.getTok();
371     auto S = Flt.getString();
372     double Val;
373     if (S.compare_lower("infinity") == 0) {
374       Val = std::numeric_limits<double>::infinity();
375     } else if (S.compare_lower("nan") == 0) {
376       Val = std::numeric_limits<double>::quiet_NaN();
377     } else {
378       return true;
379     }
380     if (IsNegative)
381       Val = -Val;
382     Operands.push_back(std::make_unique<WebAssemblyOperand>(
383         WebAssemblyOperand::Float, Flt.getLoc(), Flt.getEndLoc(),
384         WebAssemblyOperand::FltOp{Val}));
385     Parser.Lex();
386     return false;
387   }
388 
389   bool checkForP2AlignIfLoadStore(OperandVector &Operands, StringRef InstName) {
390     // FIXME: there is probably a cleaner way to do this.
391     auto IsLoadStore = InstName.find(".load") != StringRef::npos ||
392                        InstName.find(".store") != StringRef::npos;
393     auto IsAtomic = InstName.find("atomic.") != StringRef::npos;
394     if (IsLoadStore || IsAtomic) {
395       // Parse load/store operands of the form: offset:p2align=align
396       if (IsLoadStore && isNext(AsmToken::Colon)) {
397         auto Id = expectIdent();
398         if (Id != "p2align")
399           return error("Expected p2align, instead got: " + Id);
400         if (expect(AsmToken::Equal, "="))
401           return true;
402         if (!Lexer.is(AsmToken::Integer))
403           return error("Expected integer constant");
404         parseSingleInteger(false, Operands);
405       } else {
406         // Alignment not specified (or atomics, must use default alignment).
407         // We can't just call WebAssembly::GetDefaultP2Align since we don't have
408         // an opcode until after the assembly matcher, so set a default to fix
409         // up later.
410         auto Tok = Lexer.getTok();
411         Operands.push_back(std::make_unique<WebAssemblyOperand>(
412             WebAssemblyOperand::Integer, Tok.getLoc(), Tok.getEndLoc(),
413             WebAssemblyOperand::IntOp{-1}));
414       }
415     }
416     return false;
417   }
418 
419   void addBlockTypeOperand(OperandVector &Operands, SMLoc NameLoc,
420                            WebAssembly::BlockType BT) {
421     Operands.push_back(std::make_unique<WebAssemblyOperand>(
422         WebAssemblyOperand::Integer, NameLoc, NameLoc,
423         WebAssemblyOperand::IntOp{static_cast<int64_t>(BT)}));
424   }
425 
426   bool ParseInstruction(ParseInstructionInfo & /*Info*/, StringRef Name,
427                         SMLoc NameLoc, OperandVector &Operands) override {
428     // Note: Name does NOT point into the sourcecode, but to a local, so
429     // use NameLoc instead.
430     Name = StringRef(NameLoc.getPointer(), Name.size());
431 
432     // WebAssembly has instructions with / in them, which AsmLexer parses
433     // as seperate tokens, so if we find such tokens immediately adjacent (no
434     // whitespace), expand the name to include them:
435     for (;;) {
436       auto &Sep = Lexer.getTok();
437       if (Sep.getLoc().getPointer() != Name.end() ||
438           Sep.getKind() != AsmToken::Slash)
439         break;
440       // Extend name with /
441       Name = StringRef(Name.begin(), Name.size() + Sep.getString().size());
442       Parser.Lex();
443       // We must now find another identifier, or error.
444       auto &Id = Lexer.getTok();
445       if (Id.getKind() != AsmToken::Identifier ||
446           Id.getLoc().getPointer() != Name.end())
447         return error("Incomplete instruction name: ", Id);
448       Name = StringRef(Name.begin(), Name.size() + Id.getString().size());
449       Parser.Lex();
450     }
451 
452     // Now construct the name as first operand.
453     Operands.push_back(std::make_unique<WebAssemblyOperand>(
454         WebAssemblyOperand::Token, NameLoc, SMLoc::getFromPointer(Name.end()),
455         WebAssemblyOperand::TokOp{Name}));
456 
457     // If this instruction is part of a control flow structure, ensure
458     // proper nesting.
459     bool ExpectBlockType = false;
460     bool ExpectFuncType = false;
461     if (Name == "block") {
462       push(Block);
463       ExpectBlockType = true;
464     } else if (Name == "loop") {
465       push(Loop);
466       ExpectBlockType = true;
467     } else if (Name == "try") {
468       push(Try);
469       ExpectBlockType = true;
470     } else if (Name == "if") {
471       push(If);
472       ExpectBlockType = true;
473     } else if (Name == "else") {
474       if (pop(Name, If))
475         return true;
476       push(Else);
477     } else if (Name == "catch") {
478       if (pop(Name, Try))
479         return true;
480       push(Try);
481     } else if (Name == "end_if") {
482       if (pop(Name, If, Else))
483         return true;
484     } else if (Name == "end_try") {
485       if (pop(Name, Try))
486         return true;
487     } else if (Name == "end_loop") {
488       if (pop(Name, Loop))
489         return true;
490     } else if (Name == "end_block") {
491       if (pop(Name, Block))
492         return true;
493     } else if (Name == "end_function") {
494       ensureLocals(getStreamer());
495       CurrentState = EndFunction;
496       if (pop(Name, Function) || ensureEmptyNestingStack())
497         return true;
498     } else if (Name == "call_indirect" || Name == "return_call_indirect") {
499       ExpectFuncType = true;
500     }
501 
502     if (ExpectFuncType || (ExpectBlockType && Lexer.is(AsmToken::LParen))) {
503       // This has a special TYPEINDEX operand which in text we
504       // represent as a signature, such that we can re-build this signature,
505       // attach it to an anonymous symbol, which is what WasmObjectWriter
506       // expects to be able to recreate the actual unique-ified type indices.
507       auto Loc = Parser.getTok();
508       auto Signature = std::make_unique<wasm::WasmSignature>();
509       if (parseSignature(Signature.get()))
510         return true;
511       // Got signature as block type, don't need more
512       ExpectBlockType = false;
513       auto &Ctx = getStreamer().getContext();
514       // The "true" here will cause this to be a nameless symbol.
515       MCSymbol *Sym = Ctx.createTempSymbol("typeindex", true);
516       auto *WasmSym = cast<MCSymbolWasm>(Sym);
517       WasmSym->setSignature(Signature.get());
518       addSignature(std::move(Signature));
519       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
520       const MCExpr *Expr = MCSymbolRefExpr::create(
521           WasmSym, MCSymbolRefExpr::VK_WASM_TYPEINDEX, Ctx);
522       Operands.push_back(std::make_unique<WebAssemblyOperand>(
523           WebAssemblyOperand::Symbol, Loc.getLoc(), Loc.getEndLoc(),
524           WebAssemblyOperand::SymOp{Expr}));
525     }
526 
527     while (Lexer.isNot(AsmToken::EndOfStatement)) {
528       auto &Tok = Lexer.getTok();
529       switch (Tok.getKind()) {
530       case AsmToken::Identifier: {
531         if (!parseSpecialFloatMaybe(false, Operands))
532           break;
533         auto &Id = Lexer.getTok();
534         if (ExpectBlockType) {
535           // Assume this identifier is a block_type.
536           auto BT = parseBlockType(Id.getString());
537           if (BT == WebAssembly::BlockType::Invalid)
538             return error("Unknown block type: ", Id);
539           addBlockTypeOperand(Operands, NameLoc, BT);
540           Parser.Lex();
541         } else {
542           // Assume this identifier is a label.
543           const MCExpr *Val;
544           SMLoc End;
545           if (Parser.parseExpression(Val, End))
546             return error("Cannot parse symbol: ", Lexer.getTok());
547           Operands.push_back(std::make_unique<WebAssemblyOperand>(
548               WebAssemblyOperand::Symbol, Id.getLoc(), Id.getEndLoc(),
549               WebAssemblyOperand::SymOp{Val}));
550           if (checkForP2AlignIfLoadStore(Operands, Name))
551             return true;
552         }
553         break;
554       }
555       case AsmToken::Minus:
556         Parser.Lex();
557         if (Lexer.is(AsmToken::Integer)) {
558           parseSingleInteger(true, Operands);
559           if (checkForP2AlignIfLoadStore(Operands, Name))
560             return true;
561         } else if(Lexer.is(AsmToken::Real)) {
562           if (parseSingleFloat(true, Operands))
563             return true;
564         } else if (!parseSpecialFloatMaybe(true, Operands)) {
565         } else {
566           return error("Expected numeric constant instead got: ",
567                        Lexer.getTok());
568         }
569         break;
570       case AsmToken::Integer:
571         parseSingleInteger(false, Operands);
572         if (checkForP2AlignIfLoadStore(Operands, Name))
573           return true;
574         break;
575       case AsmToken::Real: {
576         if (parseSingleFloat(false, Operands))
577           return true;
578         break;
579       }
580       case AsmToken::LCurly: {
581         Parser.Lex();
582         auto Op = std::make_unique<WebAssemblyOperand>(
583             WebAssemblyOperand::BrList, Tok.getLoc(), Tok.getEndLoc());
584         if (!Lexer.is(AsmToken::RCurly))
585           for (;;) {
586             Op->BrL.List.push_back(Lexer.getTok().getIntVal());
587             expect(AsmToken::Integer, "integer");
588             if (!isNext(AsmToken::Comma))
589               break;
590           }
591         expect(AsmToken::RCurly, "}");
592         Operands.push_back(std::move(Op));
593         break;
594       }
595       default:
596         return error("Unexpected token in operand: ", Tok);
597       }
598       if (Lexer.isNot(AsmToken::EndOfStatement)) {
599         if (expect(AsmToken::Comma, ","))
600           return true;
601       }
602     }
603     if (ExpectBlockType && Operands.size() == 1) {
604       // Support blocks with no operands as default to void.
605       addBlockTypeOperand(Operands, NameLoc, WebAssembly::BlockType::Void);
606     }
607     Parser.Lex();
608     return false;
609   }
610 
611   void onLabelParsed(MCSymbol *Symbol) override {
612     LastLabel = Symbol;
613     CurrentState = Label;
614   }
615 
616   bool parseSignature(wasm::WasmSignature *Signature) {
617     if (expect(AsmToken::LParen, "("))
618       return true;
619     if (parseRegTypeList(Signature->Params))
620       return true;
621     if (expect(AsmToken::RParen, ")"))
622       return true;
623     if (expect(AsmToken::MinusGreater, "->"))
624       return true;
625     if (expect(AsmToken::LParen, "("))
626       return true;
627     if (parseRegTypeList(Signature->Returns))
628       return true;
629     if (expect(AsmToken::RParen, ")"))
630       return true;
631     return false;
632   }
633 
634   bool CheckDataSection() {
635     if (CurrentState != DataSection) {
636       auto WS = cast<MCSectionWasm>(getStreamer().getCurrentSection().first);
637       if (WS && WS->getKind().isText())
638         return error("data directive must occur in a data segment: ",
639                      Lexer.getTok());
640     }
641     CurrentState = DataSection;
642     return false;
643   }
644 
645   // This function processes wasm-specific directives streamed to
646   // WebAssemblyTargetStreamer, all others go to the generic parser
647   // (see WasmAsmParser).
648   bool ParseDirective(AsmToken DirectiveID) override {
649     // This function has a really weird return value behavior that is different
650     // from all the other parsing functions:
651     // - return true && no tokens consumed -> don't know this directive / let
652     //   the generic parser handle it.
653     // - return true && tokens consumed -> a parsing error occurred.
654     // - return false -> processed this directive successfully.
655     assert(DirectiveID.getKind() == AsmToken::Identifier);
656     auto &Out = getStreamer();
657     auto &TOut =
658         reinterpret_cast<WebAssemblyTargetStreamer &>(*Out.getTargetStreamer());
659     auto &Ctx = Out.getContext();
660 
661     // TODO: any time we return an error, at least one token must have been
662     // consumed, otherwise this will not signal an error to the caller.
663     if (DirectiveID.getString() == ".globaltype") {
664       auto SymName = expectIdent();
665       if (SymName.empty())
666         return true;
667       if (expect(AsmToken::Comma, ","))
668         return true;
669       auto TypeTok = Lexer.getTok();
670       auto TypeName = expectIdent();
671       if (TypeName.empty())
672         return true;
673       auto Type = parseType(TypeName);
674       if (!Type)
675         return error("Unknown type in .globaltype directive: ", TypeTok);
676       // Now set this symbol with the correct type.
677       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
678       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_GLOBAL);
679       WasmSym->setGlobalType(
680           wasm::WasmGlobalType{uint8_t(Type.getValue()), true});
681       // And emit the directive again.
682       TOut.emitGlobalType(WasmSym);
683       return expect(AsmToken::EndOfStatement, "EOL");
684     }
685 
686     if (DirectiveID.getString() == ".functype") {
687       // This code has to send things to the streamer similar to
688       // WebAssemblyAsmPrinter::EmitFunctionBodyStart.
689       // TODO: would be good to factor this into a common function, but the
690       // assembler and backend really don't share any common code, and this code
691       // parses the locals seperately.
692       auto SymName = expectIdent();
693       if (SymName.empty())
694         return true;
695       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
696       if (CurrentState == Label && WasmSym == LastLabel) {
697         // This .functype indicates a start of a function.
698         if (ensureEmptyNestingStack())
699           return true;
700         CurrentState = FunctionStart;
701         LastFunctionLabel = LastLabel;
702         push(Function);
703       }
704       auto Signature = std::make_unique<wasm::WasmSignature>();
705       if (parseSignature(Signature.get()))
706         return true;
707       WasmSym->setSignature(Signature.get());
708       addSignature(std::move(Signature));
709       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_FUNCTION);
710       TOut.emitFunctionType(WasmSym);
711       // TODO: backend also calls TOut.emitIndIdx, but that is not implemented.
712       return expect(AsmToken::EndOfStatement, "EOL");
713     }
714 
715     if (DirectiveID.getString() == ".export_name") {
716       auto SymName = expectIdent();
717       if (SymName.empty())
718         return true;
719       if (expect(AsmToken::Comma, ","))
720         return true;
721       auto ExportName = expectIdent();
722       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
723       WasmSym->setExportName(ExportName);
724       TOut.emitExportName(WasmSym, ExportName);
725     }
726 
727     if (DirectiveID.getString() == ".import_module") {
728       auto SymName = expectIdent();
729       if (SymName.empty())
730         return true;
731       if (expect(AsmToken::Comma, ","))
732         return true;
733       auto ImportModule = expectIdent();
734       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
735       WasmSym->setImportModule(ImportModule);
736       TOut.emitImportModule(WasmSym, ImportModule);
737     }
738 
739     if (DirectiveID.getString() == ".import_name") {
740       auto SymName = expectIdent();
741       if (SymName.empty())
742         return true;
743       if (expect(AsmToken::Comma, ","))
744         return true;
745       auto ImportName = expectIdent();
746       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
747       WasmSym->setImportName(ImportName);
748       TOut.emitImportName(WasmSym, ImportName);
749     }
750 
751     if (DirectiveID.getString() == ".eventtype") {
752       auto SymName = expectIdent();
753       if (SymName.empty())
754         return true;
755       auto WasmSym = cast<MCSymbolWasm>(Ctx.getOrCreateSymbol(SymName));
756       auto Signature = std::make_unique<wasm::WasmSignature>();
757       if (parseRegTypeList(Signature->Params))
758         return true;
759       WasmSym->setSignature(Signature.get());
760       addSignature(std::move(Signature));
761       WasmSym->setType(wasm::WASM_SYMBOL_TYPE_EVENT);
762       TOut.emitEventType(WasmSym);
763       // TODO: backend also calls TOut.emitIndIdx, but that is not implemented.
764       return expect(AsmToken::EndOfStatement, "EOL");
765     }
766 
767     if (DirectiveID.getString() == ".local") {
768       if (CurrentState != FunctionStart)
769         return error(".local directive should follow the start of a function",
770                      Lexer.getTok());
771       SmallVector<wasm::ValType, 4> Locals;
772       if (parseRegTypeList(Locals))
773         return true;
774       TOut.emitLocal(Locals);
775       CurrentState = FunctionLocals;
776       return expect(AsmToken::EndOfStatement, "EOL");
777     }
778 
779     if (DirectiveID.getString() == ".int8" ||
780         DirectiveID.getString() == ".int16" ||
781         DirectiveID.getString() == ".int32" ||
782         DirectiveID.getString() == ".int64") {
783       if (CheckDataSection()) return true;
784       const MCExpr *Val;
785       SMLoc End;
786       if (Parser.parseExpression(Val, End))
787         return error("Cannot parse .int expression: ", Lexer.getTok());
788       size_t NumBits = 0;
789       DirectiveID.getString().drop_front(4).getAsInteger(10, NumBits);
790       Out.EmitValue(Val, NumBits / 8, End);
791       return expect(AsmToken::EndOfStatement, "EOL");
792     }
793 
794     if (DirectiveID.getString() == ".asciz") {
795       if (CheckDataSection()) return true;
796       std::string S;
797       if (Parser.parseEscapedString(S))
798         return error("Cannot parse string constant: ", Lexer.getTok());
799       Out.EmitBytes(StringRef(S.c_str(), S.length() + 1));
800       return expect(AsmToken::EndOfStatement, "EOL");
801     }
802 
803     return true; // We didn't process this directive.
804   }
805 
806   // Called either when the first instruction is parsed of the function ends.
807   void ensureLocals(MCStreamer &Out) {
808     if (CurrentState == FunctionStart) {
809       // We haven't seen a .local directive yet. The streamer requires locals to
810       // be encoded as a prelude to the instructions, so emit an empty list of
811       // locals here.
812       auto &TOut = reinterpret_cast<WebAssemblyTargetStreamer &>(
813           *Out.getTargetStreamer());
814       TOut.emitLocal(SmallVector<wasm::ValType, 0>());
815       CurrentState = FunctionLocals;
816     }
817   }
818 
819   bool MatchAndEmitInstruction(SMLoc IDLoc, unsigned & /*Opcode*/,
820                                OperandVector &Operands, MCStreamer &Out,
821                                uint64_t &ErrorInfo,
822                                bool MatchingInlineAsm) override {
823     MCInst Inst;
824     Inst.setLoc(IDLoc);
825     unsigned MatchResult =
826         MatchInstructionImpl(Operands, Inst, ErrorInfo, MatchingInlineAsm);
827     switch (MatchResult) {
828     case Match_Success: {
829       ensureLocals(Out);
830       // Fix unknown p2align operands.
831       auto Align = WebAssembly::GetDefaultP2AlignAny(Inst.getOpcode());
832       if (Align != -1U) {
833         auto &Op0 = Inst.getOperand(0);
834         if (Op0.getImm() == -1)
835           Op0.setImm(Align);
836       }
837       Out.EmitInstruction(Inst, getSTI());
838       if (CurrentState == EndFunction) {
839         onEndOfFunction();
840       } else {
841         CurrentState = Instructions;
842       }
843       return false;
844     }
845     case Match_MissingFeature:
846       return Parser.Error(
847           IDLoc, "instruction requires a WASM feature not currently enabled");
848     case Match_MnemonicFail:
849       return Parser.Error(IDLoc, "invalid instruction");
850     case Match_NearMisses:
851       return Parser.Error(IDLoc, "ambiguous instruction");
852     case Match_InvalidTiedOperand:
853     case Match_InvalidOperand: {
854       SMLoc ErrorLoc = IDLoc;
855       if (ErrorInfo != ~0ULL) {
856         if (ErrorInfo >= Operands.size())
857           return Parser.Error(IDLoc, "too few operands for instruction");
858         ErrorLoc = Operands[ErrorInfo]->getStartLoc();
859         if (ErrorLoc == SMLoc())
860           ErrorLoc = IDLoc;
861       }
862       return Parser.Error(ErrorLoc, "invalid operand for instruction");
863     }
864     }
865     llvm_unreachable("Implement any new match types added!");
866   }
867 
868   void doBeforeLabelEmit(MCSymbol *Symbol) override {
869     // Start a new section for the next function automatically, since our
870     // object writer expects each function to have its own section. This way
871     // The user can't forget this "convention".
872     auto SymName = Symbol->getName();
873     if (SymName.startswith(".L"))
874       return; // Local Symbol.
875     // Only create a new text section if we're already in one.
876     auto CWS = cast<MCSectionWasm>(getStreamer().getCurrentSection().first);
877     if (!CWS || !CWS->getKind().isText())
878       return;
879     auto SecName = ".text." + SymName;
880     auto WS = getContext().getWasmSection(SecName, SectionKind::getText());
881     getStreamer().SwitchSection(WS);
882   }
883 
884   void onEndOfFunction() {
885     // Automatically output a .size directive, so it becomes optional for the
886     // user.
887     if (!LastFunctionLabel) return;
888     auto TempSym = getContext().createLinkerPrivateTempSymbol();
889     getStreamer().EmitLabel(TempSym);
890     auto Start = MCSymbolRefExpr::create(LastFunctionLabel, getContext());
891     auto End = MCSymbolRefExpr::create(TempSym, getContext());
892     auto Expr =
893         MCBinaryExpr::create(MCBinaryExpr::Sub, End, Start, getContext());
894     getStreamer().emitELFSize(LastFunctionLabel, Expr);
895   }
896 
897   void onEndOfFile() override { ensureEmptyNestingStack(); }
898 };
899 } // end anonymous namespace
900 
901 // Force static initialization.
902 extern "C" LLVM_EXTERNAL_VISIBILITY void LLVMInitializeWebAssemblyAsmParser() {
903   RegisterMCAsmParser<WebAssemblyAsmParser> X(getTheWebAssemblyTarget32());
904   RegisterMCAsmParser<WebAssemblyAsmParser> Y(getTheWebAssemblyTarget64());
905 }
906 
907 #define GET_REGISTER_MATCHER
908 #define GET_MATCHER_IMPLEMENTATION
909 #include "WebAssemblyGenAsmMatcher.inc"
910