1 //===- MILexer.cpp - Machine instructions lexer implementation ------------===//
2 //
3 //                     The LLVM Compiler Infrastructure
4 //
5 // This file is distributed under the University of Illinois Open Source
6 // License. See LICENSE.TXT for details.
7 //
8 //===----------------------------------------------------------------------===//
9 //
10 // This file implements the lexing of machine instructions.
11 //
12 //===----------------------------------------------------------------------===//
13 
14 #include "MILexer.h"
15 #include "llvm/ADT/APSInt.h"
16 #include "llvm/ADT/None.h"
17 #include "llvm/ADT/STLExtras.h"
18 #include "llvm/ADT/StringExtras.h"
19 #include "llvm/ADT/StringSwitch.h"
20 #include "llvm/ADT/StringRef.h"
21 #include "llvm/ADT/Twine.h"
22 #include <algorithm>
23 #include <cassert>
24 #include <cctype>
25 #include <string>
26 
27 using namespace llvm;
28 
29 namespace {
30 
31 using ErrorCallbackType =
32     function_ref<void(StringRef::iterator Loc, const Twine &)>;
33 
34 /// This class provides a way to iterate and get characters from the source
35 /// string.
36 class Cursor {
37   const char *Ptr = nullptr;
38   const char *End = nullptr;
39 
40 public:
41   Cursor(NoneType) {}
42 
43   explicit Cursor(StringRef Str) {
44     Ptr = Str.data();
45     End = Ptr + Str.size();
46   }
47 
48   bool isEOF() const { return Ptr == End; }
49 
50   char peek(int I = 0) const { return End - Ptr <= I ? 0 : Ptr[I]; }
51 
52   void advance(unsigned I = 1) { Ptr += I; }
53 
54   StringRef remaining() const { return StringRef(Ptr, End - Ptr); }
55 
56   StringRef upto(Cursor C) const {
57     assert(C.Ptr >= Ptr && C.Ptr <= End);
58     return StringRef(Ptr, C.Ptr - Ptr);
59   }
60 
61   StringRef::iterator location() const { return Ptr; }
62 
63   operator bool() const { return Ptr != nullptr; }
64 };
65 
66 } // end anonymous namespace
67 
68 MIToken &MIToken::reset(TokenKind Kind, StringRef Range) {
69   this->Kind = Kind;
70   this->Range = Range;
71   return *this;
72 }
73 
74 MIToken &MIToken::setStringValue(StringRef StrVal) {
75   StringValue = StrVal;
76   return *this;
77 }
78 
79 MIToken &MIToken::setOwnedStringValue(std::string StrVal) {
80   StringValueStorage = std::move(StrVal);
81   StringValue = StringValueStorage;
82   return *this;
83 }
84 
85 MIToken &MIToken::setIntegerValue(APSInt IntVal) {
86   this->IntVal = std::move(IntVal);
87   return *this;
88 }
89 
90 /// Skip the leading whitespace characters and return the updated cursor.
91 static Cursor skipWhitespace(Cursor C) {
92   while (isblank(C.peek()))
93     C.advance();
94   return C;
95 }
96 
97 static bool isNewlineChar(char C) { return C == '\n' || C == '\r'; }
98 
99 /// Skip a line comment and return the updated cursor.
100 static Cursor skipComment(Cursor C) {
101   if (C.peek() != ';')
102     return C;
103   while (!isNewlineChar(C.peek()) && !C.isEOF())
104     C.advance();
105   return C;
106 }
107 
108 /// Return true if the given character satisfies the following regular
109 /// expression: [-a-zA-Z$._0-9]
110 static bool isIdentifierChar(char C) {
111   return isalpha(C) || isdigit(C) || C == '_' || C == '-' || C == '.' ||
112          C == '$';
113 }
114 
115 /// Unescapes the given string value.
116 ///
117 /// Expects the string value to be quoted.
118 static std::string unescapeQuotedString(StringRef Value) {
119   assert(Value.front() == '"' && Value.back() == '"');
120   Cursor C = Cursor(Value.substr(1, Value.size() - 2));
121 
122   std::string Str;
123   Str.reserve(C.remaining().size());
124   while (!C.isEOF()) {
125     char Char = C.peek();
126     if (Char == '\\') {
127       if (C.peek(1) == '\\') {
128         // Two '\' become one
129         Str += '\\';
130         C.advance(2);
131         continue;
132       }
133       if (isxdigit(C.peek(1)) && isxdigit(C.peek(2))) {
134         Str += hexDigitValue(C.peek(1)) * 16 + hexDigitValue(C.peek(2));
135         C.advance(3);
136         continue;
137       }
138     }
139     Str += Char;
140     C.advance();
141   }
142   return Str;
143 }
144 
145 /// Lex a string constant using the following regular expression: \"[^\"]*\"
146 static Cursor lexStringConstant(Cursor C, ErrorCallbackType ErrorCallback) {
147   assert(C.peek() == '"');
148   for (C.advance(); C.peek() != '"'; C.advance()) {
149     if (C.isEOF() || isNewlineChar(C.peek())) {
150       ErrorCallback(
151           C.location(),
152           "end of machine instruction reached before the closing '\"'");
153       return None;
154     }
155   }
156   C.advance();
157   return C;
158 }
159 
160 static Cursor lexName(Cursor C, MIToken &Token, MIToken::TokenKind Type,
161                       unsigned PrefixLength, ErrorCallbackType ErrorCallback) {
162   auto Range = C;
163   C.advance(PrefixLength);
164   if (C.peek() == '"') {
165     if (Cursor R = lexStringConstant(C, ErrorCallback)) {
166       StringRef String = Range.upto(R);
167       Token.reset(Type, String)
168           .setOwnedStringValue(
169               unescapeQuotedString(String.drop_front(PrefixLength)));
170       return R;
171     }
172     Token.reset(MIToken::Error, Range.remaining());
173     return Range;
174   }
175   while (isIdentifierChar(C.peek()))
176     C.advance();
177   Token.reset(Type, Range.upto(C))
178       .setStringValue(Range.upto(C).drop_front(PrefixLength));
179   return C;
180 }
181 
182 static Cursor maybeLexIntegerOrScalarType(Cursor C, MIToken &Token) {
183   if ((C.peek() != 'i' && C.peek() != 's' && C.peek() != 'p') ||
184       !isdigit(C.peek(1)))
185     return None;
186   char Kind = C.peek();
187   auto Range = C;
188   C.advance(); // Skip 'i', 's', or 'p'
189   while (isdigit(C.peek()))
190     C.advance();
191 
192   Token.reset(Kind == 'i'
193                   ? MIToken::IntegerType
194                   : (Kind == 's' ? MIToken::ScalarType : MIToken::PointerType),
195               Range.upto(C));
196   return C;
197 }
198 
199 static MIToken::TokenKind getIdentifierKind(StringRef Identifier) {
200   return StringSwitch<MIToken::TokenKind>(Identifier)
201       .Case("_", MIToken::underscore)
202       .Case("implicit", MIToken::kw_implicit)
203       .Case("implicit-def", MIToken::kw_implicit_define)
204       .Case("def", MIToken::kw_def)
205       .Case("dead", MIToken::kw_dead)
206       .Case("killed", MIToken::kw_killed)
207       .Case("undef", MIToken::kw_undef)
208       .Case("internal", MIToken::kw_internal)
209       .Case("early-clobber", MIToken::kw_early_clobber)
210       .Case("debug-use", MIToken::kw_debug_use)
211       .Case("tied-def", MIToken::kw_tied_def)
212       .Case("frame-setup", MIToken::kw_frame_setup)
213       .Case("debug-location", MIToken::kw_debug_location)
214       .Case("same_value", MIToken::kw_cfi_same_value)
215       .Case("offset", MIToken::kw_cfi_offset)
216       .Case("def_cfa_register", MIToken::kw_cfi_def_cfa_register)
217       .Case("def_cfa_offset", MIToken::kw_cfi_def_cfa_offset)
218       .Case("def_cfa", MIToken::kw_cfi_def_cfa)
219       .Case("blockaddress", MIToken::kw_blockaddress)
220       .Case("intrinsic", MIToken::kw_intrinsic)
221       .Case("target-index", MIToken::kw_target_index)
222       .Case("half", MIToken::kw_half)
223       .Case("float", MIToken::kw_float)
224       .Case("double", MIToken::kw_double)
225       .Case("x86_fp80", MIToken::kw_x86_fp80)
226       .Case("fp128", MIToken::kw_fp128)
227       .Case("ppc_fp128", MIToken::kw_ppc_fp128)
228       .Case("target-flags", MIToken::kw_target_flags)
229       .Case("volatile", MIToken::kw_volatile)
230       .Case("non-temporal", MIToken::kw_non_temporal)
231       .Case("dereferenceable", MIToken::kw_dereferenceable)
232       .Case("invariant", MIToken::kw_invariant)
233       .Case("align", MIToken::kw_align)
234       .Case("stack", MIToken::kw_stack)
235       .Case("got", MIToken::kw_got)
236       .Case("jump-table", MIToken::kw_jump_table)
237       .Case("constant-pool", MIToken::kw_constant_pool)
238       .Case("call-entry", MIToken::kw_call_entry)
239       .Case("liveout", MIToken::kw_liveout)
240       .Case("address-taken", MIToken::kw_address_taken)
241       .Case("landing-pad", MIToken::kw_landing_pad)
242       .Case("liveins", MIToken::kw_liveins)
243       .Case("successors", MIToken::kw_successors)
244       .Case("floatpred", MIToken::kw_floatpred)
245       .Case("intpred", MIToken::kw_intpred)
246       .Default(MIToken::Identifier);
247 }
248 
249 static Cursor maybeLexIdentifier(Cursor C, MIToken &Token) {
250   if (!isalpha(C.peek()) && C.peek() != '_')
251     return None;
252   auto Range = C;
253   while (isIdentifierChar(C.peek()))
254     C.advance();
255   auto Identifier = Range.upto(C);
256   Token.reset(getIdentifierKind(Identifier), Identifier)
257       .setStringValue(Identifier);
258   return C;
259 }
260 
261 static Cursor maybeLexMachineBasicBlock(Cursor C, MIToken &Token,
262                                         ErrorCallbackType ErrorCallback) {
263   bool IsReference = C.remaining().startswith("%bb.");
264   if (!IsReference && !C.remaining().startswith("bb."))
265     return None;
266   auto Range = C;
267   unsigned PrefixLength = IsReference ? 4 : 3;
268   C.advance(PrefixLength); // Skip '%bb.' or 'bb.'
269   if (!isdigit(C.peek())) {
270     Token.reset(MIToken::Error, C.remaining());
271     ErrorCallback(C.location(), "expected a number after '%bb.'");
272     return C;
273   }
274   auto NumberRange = C;
275   while (isdigit(C.peek()))
276     C.advance();
277   StringRef Number = NumberRange.upto(C);
278   unsigned StringOffset = PrefixLength + Number.size(); // Drop '%bb.<id>'
279   if (C.peek() == '.') {
280     C.advance(); // Skip '.'
281     ++StringOffset;
282     while (isIdentifierChar(C.peek()))
283       C.advance();
284   }
285   Token.reset(IsReference ? MIToken::MachineBasicBlock
286                           : MIToken::MachineBasicBlockLabel,
287               Range.upto(C))
288       .setIntegerValue(APSInt(Number))
289       .setStringValue(Range.upto(C).drop_front(StringOffset));
290   return C;
291 }
292 
293 static Cursor maybeLexIndex(Cursor C, MIToken &Token, StringRef Rule,
294                             MIToken::TokenKind Kind) {
295   if (!C.remaining().startswith(Rule) || !isdigit(C.peek(Rule.size())))
296     return None;
297   auto Range = C;
298   C.advance(Rule.size());
299   auto NumberRange = C;
300   while (isdigit(C.peek()))
301     C.advance();
302   Token.reset(Kind, Range.upto(C)).setIntegerValue(APSInt(NumberRange.upto(C)));
303   return C;
304 }
305 
306 static Cursor maybeLexIndexAndName(Cursor C, MIToken &Token, StringRef Rule,
307                                    MIToken::TokenKind Kind) {
308   if (!C.remaining().startswith(Rule) || !isdigit(C.peek(Rule.size())))
309     return None;
310   auto Range = C;
311   C.advance(Rule.size());
312   auto NumberRange = C;
313   while (isdigit(C.peek()))
314     C.advance();
315   StringRef Number = NumberRange.upto(C);
316   unsigned StringOffset = Rule.size() + Number.size();
317   if (C.peek() == '.') {
318     C.advance();
319     ++StringOffset;
320     while (isIdentifierChar(C.peek()))
321       C.advance();
322   }
323   Token.reset(Kind, Range.upto(C))
324       .setIntegerValue(APSInt(Number))
325       .setStringValue(Range.upto(C).drop_front(StringOffset));
326   return C;
327 }
328 
329 static Cursor maybeLexJumpTableIndex(Cursor C, MIToken &Token) {
330   return maybeLexIndex(C, Token, "%jump-table.", MIToken::JumpTableIndex);
331 }
332 
333 static Cursor maybeLexStackObject(Cursor C, MIToken &Token) {
334   return maybeLexIndexAndName(C, Token, "%stack.", MIToken::StackObject);
335 }
336 
337 static Cursor maybeLexFixedStackObject(Cursor C, MIToken &Token) {
338   return maybeLexIndex(C, Token, "%fixed-stack.", MIToken::FixedStackObject);
339 }
340 
341 static Cursor maybeLexConstantPoolItem(Cursor C, MIToken &Token) {
342   return maybeLexIndex(C, Token, "%const.", MIToken::ConstantPoolItem);
343 }
344 
345 static Cursor maybeLexSubRegisterIndex(Cursor C, MIToken &Token,
346                                        ErrorCallbackType ErrorCallback) {
347   const StringRef Rule = "%subreg.";
348   if (!C.remaining().startswith(Rule))
349     return None;
350   return lexName(C, Token, MIToken::SubRegisterIndex, Rule.size(),
351                  ErrorCallback);
352 }
353 
354 static Cursor maybeLexIRBlock(Cursor C, MIToken &Token,
355                               ErrorCallbackType ErrorCallback) {
356   const StringRef Rule = "%ir-block.";
357   if (!C.remaining().startswith(Rule))
358     return None;
359   if (isdigit(C.peek(Rule.size())))
360     return maybeLexIndex(C, Token, Rule, MIToken::IRBlock);
361   return lexName(C, Token, MIToken::NamedIRBlock, Rule.size(), ErrorCallback);
362 }
363 
364 static Cursor maybeLexIRValue(Cursor C, MIToken &Token,
365                               ErrorCallbackType ErrorCallback) {
366   const StringRef Rule = "%ir.";
367   if (!C.remaining().startswith(Rule))
368     return None;
369   if (isdigit(C.peek(Rule.size())))
370     return maybeLexIndex(C, Token, Rule, MIToken::IRValue);
371   return lexName(C, Token, MIToken::NamedIRValue, Rule.size(), ErrorCallback);
372 }
373 
374 static Cursor maybeLexStringConstant(Cursor C, MIToken &Token,
375                                      ErrorCallbackType ErrorCallback) {
376   if (C.peek() != '"')
377     return None;
378   return lexName(C, Token, MIToken::StringConstant, /*PrefixLength=*/0,
379                  ErrorCallback);
380 }
381 
382 static Cursor lexVirtualRegister(Cursor C, MIToken &Token) {
383   auto Range = C;
384   C.advance(); // Skip '%'
385   auto NumberRange = C;
386   while (isdigit(C.peek()))
387     C.advance();
388   Token.reset(MIToken::VirtualRegister, Range.upto(C))
389       .setIntegerValue(APSInt(NumberRange.upto(C)));
390   return C;
391 }
392 
393 /// Returns true for a character allowed in a register name.
394 static bool isRegisterChar(char C) {
395   return isIdentifierChar(C) && C != '.';
396 }
397 
398 static Cursor maybeLexRegister(Cursor C, MIToken &Token) {
399   if (C.peek() != '%')
400     return None;
401   if (isdigit(C.peek(1)))
402     return lexVirtualRegister(C, Token);
403   auto Range = C;
404   C.advance(); // Skip '%'
405   while (isRegisterChar(C.peek()))
406     C.advance();
407   Token.reset(MIToken::NamedRegister, Range.upto(C))
408       .setStringValue(Range.upto(C).drop_front(1)); // Drop the '%'
409   return C;
410 }
411 
412 static Cursor maybeLexGlobalValue(Cursor C, MIToken &Token,
413                                   ErrorCallbackType ErrorCallback) {
414   if (C.peek() != '@')
415     return None;
416   if (!isdigit(C.peek(1)))
417     return lexName(C, Token, MIToken::NamedGlobalValue, /*PrefixLength=*/1,
418                    ErrorCallback);
419   auto Range = C;
420   C.advance(1); // Skip the '@'
421   auto NumberRange = C;
422   while (isdigit(C.peek()))
423     C.advance();
424   Token.reset(MIToken::GlobalValue, Range.upto(C))
425       .setIntegerValue(APSInt(NumberRange.upto(C)));
426   return C;
427 }
428 
429 static Cursor maybeLexExternalSymbol(Cursor C, MIToken &Token,
430                                      ErrorCallbackType ErrorCallback) {
431   if (C.peek() != '$')
432     return None;
433   return lexName(C, Token, MIToken::ExternalSymbol, /*PrefixLength=*/1,
434                  ErrorCallback);
435 }
436 
437 static bool isValidHexFloatingPointPrefix(char C) {
438   return C == 'H' || C == 'K' || C == 'L' || C == 'M';
439 }
440 
441 static Cursor lexFloatingPointLiteral(Cursor Range, Cursor C, MIToken &Token) {
442   C.advance();
443   // Skip over [0-9]*([eE][-+]?[0-9]+)?
444   while (isdigit(C.peek()))
445     C.advance();
446   if ((C.peek() == 'e' || C.peek() == 'E') &&
447       (isdigit(C.peek(1)) ||
448        ((C.peek(1) == '-' || C.peek(1) == '+') && isdigit(C.peek(2))))) {
449     C.advance(2);
450     while (isdigit(C.peek()))
451       C.advance();
452   }
453   Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
454   return C;
455 }
456 
457 static Cursor maybeLexHexadecimalLiteral(Cursor C, MIToken &Token) {
458   if (C.peek() != '0' || (C.peek(1) != 'x' && C.peek(1) != 'X'))
459     return None;
460   Cursor Range = C;
461   C.advance(2);
462   unsigned PrefLen = 2;
463   if (isValidHexFloatingPointPrefix(C.peek())) {
464     C.advance();
465     PrefLen++;
466   }
467   while (isxdigit(C.peek()))
468     C.advance();
469   StringRef StrVal = Range.upto(C);
470   if (StrVal.size() <= PrefLen)
471     return None;
472   if (PrefLen == 2)
473     Token.reset(MIToken::HexLiteral, Range.upto(C));
474   else // It must be 3, which means that there was a floating-point prefix.
475     Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
476   return C;
477 }
478 
479 static Cursor maybeLexNumericalLiteral(Cursor C, MIToken &Token) {
480   if (!isdigit(C.peek()) && (C.peek() != '-' || !isdigit(C.peek(1))))
481     return None;
482   auto Range = C;
483   C.advance();
484   while (isdigit(C.peek()))
485     C.advance();
486   if (C.peek() == '.')
487     return lexFloatingPointLiteral(Range, C, Token);
488   StringRef StrVal = Range.upto(C);
489   Token.reset(MIToken::IntegerLiteral, StrVal).setIntegerValue(APSInt(StrVal));
490   return C;
491 }
492 
493 static MIToken::TokenKind getMetadataKeywordKind(StringRef Identifier) {
494   return StringSwitch<MIToken::TokenKind>(Identifier)
495       .Case("!tbaa", MIToken::md_tbaa)
496       .Case("!alias.scope", MIToken::md_alias_scope)
497       .Case("!noalias", MIToken::md_noalias)
498       .Case("!range", MIToken::md_range)
499       .Case("!DIExpression", MIToken::md_diexpr)
500       .Default(MIToken::Error);
501 }
502 
503 static Cursor maybeLexExlaim(Cursor C, MIToken &Token,
504                              ErrorCallbackType ErrorCallback) {
505   if (C.peek() != '!')
506     return None;
507   auto Range = C;
508   C.advance(1);
509   if (isdigit(C.peek()) || !isIdentifierChar(C.peek())) {
510     Token.reset(MIToken::exclaim, Range.upto(C));
511     return C;
512   }
513   while (isIdentifierChar(C.peek()))
514     C.advance();
515   StringRef StrVal = Range.upto(C);
516   Token.reset(getMetadataKeywordKind(StrVal), StrVal);
517   if (Token.isError())
518     ErrorCallback(Token.location(),
519                   "use of unknown metadata keyword '" + StrVal + "'");
520   return C;
521 }
522 
523 static MIToken::TokenKind symbolToken(char C) {
524   switch (C) {
525   case ',':
526     return MIToken::comma;
527   case '.':
528     return MIToken::dot;
529   case '=':
530     return MIToken::equal;
531   case ':':
532     return MIToken::colon;
533   case '(':
534     return MIToken::lparen;
535   case ')':
536     return MIToken::rparen;
537   case '{':
538     return MIToken::lbrace;
539   case '}':
540     return MIToken::rbrace;
541   case '+':
542     return MIToken::plus;
543   case '-':
544     return MIToken::minus;
545   case '<':
546     return MIToken::less;
547   case '>':
548     return MIToken::greater;
549   default:
550     return MIToken::Error;
551   }
552 }
553 
554 static Cursor maybeLexSymbol(Cursor C, MIToken &Token) {
555   MIToken::TokenKind Kind;
556   unsigned Length = 1;
557   if (C.peek() == ':' && C.peek(1) == ':') {
558     Kind = MIToken::coloncolon;
559     Length = 2;
560   } else
561     Kind = symbolToken(C.peek());
562   if (Kind == MIToken::Error)
563     return None;
564   auto Range = C;
565   C.advance(Length);
566   Token.reset(Kind, Range.upto(C));
567   return C;
568 }
569 
570 static Cursor maybeLexNewline(Cursor C, MIToken &Token) {
571   if (!isNewlineChar(C.peek()))
572     return None;
573   auto Range = C;
574   C.advance();
575   Token.reset(MIToken::Newline, Range.upto(C));
576   return C;
577 }
578 
579 static Cursor maybeLexEscapedIRValue(Cursor C, MIToken &Token,
580                                      ErrorCallbackType ErrorCallback) {
581   if (C.peek() != '`')
582     return None;
583   auto Range = C;
584   C.advance();
585   auto StrRange = C;
586   while (C.peek() != '`') {
587     if (C.isEOF() || isNewlineChar(C.peek())) {
588       ErrorCallback(
589           C.location(),
590           "end of machine instruction reached before the closing '`'");
591       Token.reset(MIToken::Error, Range.remaining());
592       return C;
593     }
594     C.advance();
595   }
596   StringRef Value = StrRange.upto(C);
597   C.advance();
598   Token.reset(MIToken::QuotedIRValue, Range.upto(C)).setStringValue(Value);
599   return C;
600 }
601 
602 StringRef llvm::lexMIToken(StringRef Source, MIToken &Token,
603                            ErrorCallbackType ErrorCallback) {
604   auto C = skipComment(skipWhitespace(Cursor(Source)));
605   if (C.isEOF()) {
606     Token.reset(MIToken::Eof, C.remaining());
607     return C.remaining();
608   }
609 
610   if (Cursor R = maybeLexIntegerOrScalarType(C, Token))
611     return R.remaining();
612   if (Cursor R = maybeLexMachineBasicBlock(C, Token, ErrorCallback))
613     return R.remaining();
614   if (Cursor R = maybeLexIdentifier(C, Token))
615     return R.remaining();
616   if (Cursor R = maybeLexJumpTableIndex(C, Token))
617     return R.remaining();
618   if (Cursor R = maybeLexStackObject(C, Token))
619     return R.remaining();
620   if (Cursor R = maybeLexFixedStackObject(C, Token))
621     return R.remaining();
622   if (Cursor R = maybeLexConstantPoolItem(C, Token))
623     return R.remaining();
624   if (Cursor R = maybeLexSubRegisterIndex(C, Token, ErrorCallback))
625     return R.remaining();
626   if (Cursor R = maybeLexIRBlock(C, Token, ErrorCallback))
627     return R.remaining();
628   if (Cursor R = maybeLexIRValue(C, Token, ErrorCallback))
629     return R.remaining();
630   if (Cursor R = maybeLexRegister(C, Token))
631     return R.remaining();
632   if (Cursor R = maybeLexGlobalValue(C, Token, ErrorCallback))
633     return R.remaining();
634   if (Cursor R = maybeLexExternalSymbol(C, Token, ErrorCallback))
635     return R.remaining();
636   if (Cursor R = maybeLexHexadecimalLiteral(C, Token))
637     return R.remaining();
638   if (Cursor R = maybeLexNumericalLiteral(C, Token))
639     return R.remaining();
640   if (Cursor R = maybeLexExlaim(C, Token, ErrorCallback))
641     return R.remaining();
642   if (Cursor R = maybeLexSymbol(C, Token))
643     return R.remaining();
644   if (Cursor R = maybeLexNewline(C, Token))
645     return R.remaining();
646   if (Cursor R = maybeLexEscapedIRValue(C, Token, ErrorCallback))
647     return R.remaining();
648   if (Cursor R = maybeLexStringConstant(C, Token, ErrorCallback))
649     return R.remaining();
650 
651   Token.reset(MIToken::Error, C.remaining());
652   ErrorCallback(C.location(),
653                 Twine("unexpected character '") + Twine(C.peek()) + "'");
654   return C.remaining();
655 }
656