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("restore", MIToken::kw_cfi_restore)
220       .Case("blockaddress", MIToken::kw_blockaddress)
221       .Case("intrinsic", MIToken::kw_intrinsic)
222       .Case("target-index", MIToken::kw_target_index)
223       .Case("half", MIToken::kw_half)
224       .Case("float", MIToken::kw_float)
225       .Case("double", MIToken::kw_double)
226       .Case("x86_fp80", MIToken::kw_x86_fp80)
227       .Case("fp128", MIToken::kw_fp128)
228       .Case("ppc_fp128", MIToken::kw_ppc_fp128)
229       .Case("target-flags", MIToken::kw_target_flags)
230       .Case("volatile", MIToken::kw_volatile)
231       .Case("non-temporal", MIToken::kw_non_temporal)
232       .Case("dereferenceable", MIToken::kw_dereferenceable)
233       .Case("invariant", MIToken::kw_invariant)
234       .Case("align", MIToken::kw_align)
235       .Case("stack", MIToken::kw_stack)
236       .Case("got", MIToken::kw_got)
237       .Case("jump-table", MIToken::kw_jump_table)
238       .Case("constant-pool", MIToken::kw_constant_pool)
239       .Case("call-entry", MIToken::kw_call_entry)
240       .Case("liveout", MIToken::kw_liveout)
241       .Case("address-taken", MIToken::kw_address_taken)
242       .Case("landing-pad", MIToken::kw_landing_pad)
243       .Case("liveins", MIToken::kw_liveins)
244       .Case("successors", MIToken::kw_successors)
245       .Case("floatpred", MIToken::kw_floatpred)
246       .Case("intpred", MIToken::kw_intpred)
247       .Default(MIToken::Identifier);
248 }
249 
250 static Cursor maybeLexIdentifier(Cursor C, MIToken &Token) {
251   if (!isalpha(C.peek()) && C.peek() != '_')
252     return None;
253   auto Range = C;
254   while (isIdentifierChar(C.peek()))
255     C.advance();
256   auto Identifier = Range.upto(C);
257   Token.reset(getIdentifierKind(Identifier), Identifier)
258       .setStringValue(Identifier);
259   return C;
260 }
261 
262 static Cursor maybeLexMachineBasicBlock(Cursor C, MIToken &Token,
263                                         ErrorCallbackType ErrorCallback) {
264   bool IsReference = C.remaining().startswith("%bb.");
265   if (!IsReference && !C.remaining().startswith("bb."))
266     return None;
267   auto Range = C;
268   unsigned PrefixLength = IsReference ? 4 : 3;
269   C.advance(PrefixLength); // Skip '%bb.' or 'bb.'
270   if (!isdigit(C.peek())) {
271     Token.reset(MIToken::Error, C.remaining());
272     ErrorCallback(C.location(), "expected a number after '%bb.'");
273     return C;
274   }
275   auto NumberRange = C;
276   while (isdigit(C.peek()))
277     C.advance();
278   StringRef Number = NumberRange.upto(C);
279   unsigned StringOffset = PrefixLength + Number.size(); // Drop '%bb.<id>'
280   // TODO: The format bb.<id>.<irname> is supported only when it's not a
281   // reference. Once we deprecate the format where the irname shows up, we
282   // should only lex forward if it is a reference.
283   if (C.peek() == '.') {
284     C.advance(); // Skip '.'
285     ++StringOffset;
286     while (isIdentifierChar(C.peek()))
287       C.advance();
288   }
289   Token.reset(IsReference ? MIToken::MachineBasicBlock
290                           : MIToken::MachineBasicBlockLabel,
291               Range.upto(C))
292       .setIntegerValue(APSInt(Number))
293       .setStringValue(Range.upto(C).drop_front(StringOffset));
294   return C;
295 }
296 
297 static Cursor maybeLexIndex(Cursor C, MIToken &Token, StringRef Rule,
298                             MIToken::TokenKind Kind) {
299   if (!C.remaining().startswith(Rule) || !isdigit(C.peek(Rule.size())))
300     return None;
301   auto Range = C;
302   C.advance(Rule.size());
303   auto NumberRange = C;
304   while (isdigit(C.peek()))
305     C.advance();
306   Token.reset(Kind, Range.upto(C)).setIntegerValue(APSInt(NumberRange.upto(C)));
307   return C;
308 }
309 
310 static Cursor maybeLexIndexAndName(Cursor C, MIToken &Token, StringRef Rule,
311                                    MIToken::TokenKind Kind) {
312   if (!C.remaining().startswith(Rule) || !isdigit(C.peek(Rule.size())))
313     return None;
314   auto Range = C;
315   C.advance(Rule.size());
316   auto NumberRange = C;
317   while (isdigit(C.peek()))
318     C.advance();
319   StringRef Number = NumberRange.upto(C);
320   unsigned StringOffset = Rule.size() + Number.size();
321   if (C.peek() == '.') {
322     C.advance();
323     ++StringOffset;
324     while (isIdentifierChar(C.peek()))
325       C.advance();
326   }
327   Token.reset(Kind, Range.upto(C))
328       .setIntegerValue(APSInt(Number))
329       .setStringValue(Range.upto(C).drop_front(StringOffset));
330   return C;
331 }
332 
333 static Cursor maybeLexJumpTableIndex(Cursor C, MIToken &Token) {
334   return maybeLexIndex(C, Token, "%jump-table.", MIToken::JumpTableIndex);
335 }
336 
337 static Cursor maybeLexStackObject(Cursor C, MIToken &Token) {
338   return maybeLexIndexAndName(C, Token, "%stack.", MIToken::StackObject);
339 }
340 
341 static Cursor maybeLexFixedStackObject(Cursor C, MIToken &Token) {
342   return maybeLexIndex(C, Token, "%fixed-stack.", MIToken::FixedStackObject);
343 }
344 
345 static Cursor maybeLexConstantPoolItem(Cursor C, MIToken &Token) {
346   return maybeLexIndex(C, Token, "%const.", MIToken::ConstantPoolItem);
347 }
348 
349 static Cursor maybeLexSubRegisterIndex(Cursor C, MIToken &Token,
350                                        ErrorCallbackType ErrorCallback) {
351   const StringRef Rule = "%subreg.";
352   if (!C.remaining().startswith(Rule))
353     return None;
354   return lexName(C, Token, MIToken::SubRegisterIndex, Rule.size(),
355                  ErrorCallback);
356 }
357 
358 static Cursor maybeLexIRBlock(Cursor C, MIToken &Token,
359                               ErrorCallbackType ErrorCallback) {
360   const StringRef Rule = "%ir-block.";
361   if (!C.remaining().startswith(Rule))
362     return None;
363   if (isdigit(C.peek(Rule.size())))
364     return maybeLexIndex(C, Token, Rule, MIToken::IRBlock);
365   return lexName(C, Token, MIToken::NamedIRBlock, Rule.size(), ErrorCallback);
366 }
367 
368 static Cursor maybeLexIRValue(Cursor C, MIToken &Token,
369                               ErrorCallbackType ErrorCallback) {
370   const StringRef Rule = "%ir.";
371   if (!C.remaining().startswith(Rule))
372     return None;
373   if (isdigit(C.peek(Rule.size())))
374     return maybeLexIndex(C, Token, Rule, MIToken::IRValue);
375   return lexName(C, Token, MIToken::NamedIRValue, Rule.size(), ErrorCallback);
376 }
377 
378 static Cursor maybeLexStringConstant(Cursor C, MIToken &Token,
379                                      ErrorCallbackType ErrorCallback) {
380   if (C.peek() != '"')
381     return None;
382   return lexName(C, Token, MIToken::StringConstant, /*PrefixLength=*/0,
383                  ErrorCallback);
384 }
385 
386 static Cursor lexVirtualRegister(Cursor C, MIToken &Token) {
387   auto Range = C;
388   C.advance(); // Skip '%'
389   auto NumberRange = C;
390   while (isdigit(C.peek()))
391     C.advance();
392   Token.reset(MIToken::VirtualRegister, Range.upto(C))
393       .setIntegerValue(APSInt(NumberRange.upto(C)));
394   return C;
395 }
396 
397 /// Returns true for a character allowed in a register name.
398 static bool isRegisterChar(char C) {
399   return isIdentifierChar(C) && C != '.';
400 }
401 
402 static Cursor maybeLexRegister(Cursor C, MIToken &Token) {
403   if (C.peek() != '%')
404     return None;
405   if (isdigit(C.peek(1)))
406     return lexVirtualRegister(C, Token);
407   auto Range = C;
408   C.advance(); // Skip '%'
409   while (isRegisterChar(C.peek()))
410     C.advance();
411   Token.reset(MIToken::NamedRegister, Range.upto(C))
412       .setStringValue(Range.upto(C).drop_front(1)); // Drop the '%'
413   return C;
414 }
415 
416 static Cursor maybeLexGlobalValue(Cursor C, MIToken &Token,
417                                   ErrorCallbackType ErrorCallback) {
418   if (C.peek() != '@')
419     return None;
420   if (!isdigit(C.peek(1)))
421     return lexName(C, Token, MIToken::NamedGlobalValue, /*PrefixLength=*/1,
422                    ErrorCallback);
423   auto Range = C;
424   C.advance(1); // Skip the '@'
425   auto NumberRange = C;
426   while (isdigit(C.peek()))
427     C.advance();
428   Token.reset(MIToken::GlobalValue, Range.upto(C))
429       .setIntegerValue(APSInt(NumberRange.upto(C)));
430   return C;
431 }
432 
433 static Cursor maybeLexExternalSymbol(Cursor C, MIToken &Token,
434                                      ErrorCallbackType ErrorCallback) {
435   if (C.peek() != '$')
436     return None;
437   return lexName(C, Token, MIToken::ExternalSymbol, /*PrefixLength=*/1,
438                  ErrorCallback);
439 }
440 
441 static bool isValidHexFloatingPointPrefix(char C) {
442   return C == 'H' || C == 'K' || C == 'L' || C == 'M';
443 }
444 
445 static Cursor lexFloatingPointLiteral(Cursor Range, Cursor C, MIToken &Token) {
446   C.advance();
447   // Skip over [0-9]*([eE][-+]?[0-9]+)?
448   while (isdigit(C.peek()))
449     C.advance();
450   if ((C.peek() == 'e' || C.peek() == 'E') &&
451       (isdigit(C.peek(1)) ||
452        ((C.peek(1) == '-' || C.peek(1) == '+') && isdigit(C.peek(2))))) {
453     C.advance(2);
454     while (isdigit(C.peek()))
455       C.advance();
456   }
457   Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
458   return C;
459 }
460 
461 static Cursor maybeLexHexadecimalLiteral(Cursor C, MIToken &Token) {
462   if (C.peek() != '0' || (C.peek(1) != 'x' && C.peek(1) != 'X'))
463     return None;
464   Cursor Range = C;
465   C.advance(2);
466   unsigned PrefLen = 2;
467   if (isValidHexFloatingPointPrefix(C.peek())) {
468     C.advance();
469     PrefLen++;
470   }
471   while (isxdigit(C.peek()))
472     C.advance();
473   StringRef StrVal = Range.upto(C);
474   if (StrVal.size() <= PrefLen)
475     return None;
476   if (PrefLen == 2)
477     Token.reset(MIToken::HexLiteral, Range.upto(C));
478   else // It must be 3, which means that there was a floating-point prefix.
479     Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
480   return C;
481 }
482 
483 static Cursor maybeLexNumericalLiteral(Cursor C, MIToken &Token) {
484   if (!isdigit(C.peek()) && (C.peek() != '-' || !isdigit(C.peek(1))))
485     return None;
486   auto Range = C;
487   C.advance();
488   while (isdigit(C.peek()))
489     C.advance();
490   if (C.peek() == '.')
491     return lexFloatingPointLiteral(Range, C, Token);
492   StringRef StrVal = Range.upto(C);
493   Token.reset(MIToken::IntegerLiteral, StrVal).setIntegerValue(APSInt(StrVal));
494   return C;
495 }
496 
497 static MIToken::TokenKind getMetadataKeywordKind(StringRef Identifier) {
498   return StringSwitch<MIToken::TokenKind>(Identifier)
499       .Case("!tbaa", MIToken::md_tbaa)
500       .Case("!alias.scope", MIToken::md_alias_scope)
501       .Case("!noalias", MIToken::md_noalias)
502       .Case("!range", MIToken::md_range)
503       .Case("!DIExpression", MIToken::md_diexpr)
504       .Default(MIToken::Error);
505 }
506 
507 static Cursor maybeLexExlaim(Cursor C, MIToken &Token,
508                              ErrorCallbackType ErrorCallback) {
509   if (C.peek() != '!')
510     return None;
511   auto Range = C;
512   C.advance(1);
513   if (isdigit(C.peek()) || !isIdentifierChar(C.peek())) {
514     Token.reset(MIToken::exclaim, Range.upto(C));
515     return C;
516   }
517   while (isIdentifierChar(C.peek()))
518     C.advance();
519   StringRef StrVal = Range.upto(C);
520   Token.reset(getMetadataKeywordKind(StrVal), StrVal);
521   if (Token.isError())
522     ErrorCallback(Token.location(),
523                   "use of unknown metadata keyword '" + StrVal + "'");
524   return C;
525 }
526 
527 static MIToken::TokenKind symbolToken(char C) {
528   switch (C) {
529   case ',':
530     return MIToken::comma;
531   case '.':
532     return MIToken::dot;
533   case '=':
534     return MIToken::equal;
535   case ':':
536     return MIToken::colon;
537   case '(':
538     return MIToken::lparen;
539   case ')':
540     return MIToken::rparen;
541   case '{':
542     return MIToken::lbrace;
543   case '}':
544     return MIToken::rbrace;
545   case '+':
546     return MIToken::plus;
547   case '-':
548     return MIToken::minus;
549   case '<':
550     return MIToken::less;
551   case '>':
552     return MIToken::greater;
553   default:
554     return MIToken::Error;
555   }
556 }
557 
558 static Cursor maybeLexSymbol(Cursor C, MIToken &Token) {
559   MIToken::TokenKind Kind;
560   unsigned Length = 1;
561   if (C.peek() == ':' && C.peek(1) == ':') {
562     Kind = MIToken::coloncolon;
563     Length = 2;
564   } else
565     Kind = symbolToken(C.peek());
566   if (Kind == MIToken::Error)
567     return None;
568   auto Range = C;
569   C.advance(Length);
570   Token.reset(Kind, Range.upto(C));
571   return C;
572 }
573 
574 static Cursor maybeLexNewline(Cursor C, MIToken &Token) {
575   if (!isNewlineChar(C.peek()))
576     return None;
577   auto Range = C;
578   C.advance();
579   Token.reset(MIToken::Newline, Range.upto(C));
580   return C;
581 }
582 
583 static Cursor maybeLexEscapedIRValue(Cursor C, MIToken &Token,
584                                      ErrorCallbackType ErrorCallback) {
585   if (C.peek() != '`')
586     return None;
587   auto Range = C;
588   C.advance();
589   auto StrRange = C;
590   while (C.peek() != '`') {
591     if (C.isEOF() || isNewlineChar(C.peek())) {
592       ErrorCallback(
593           C.location(),
594           "end of machine instruction reached before the closing '`'");
595       Token.reset(MIToken::Error, Range.remaining());
596       return C;
597     }
598     C.advance();
599   }
600   StringRef Value = StrRange.upto(C);
601   C.advance();
602   Token.reset(MIToken::QuotedIRValue, Range.upto(C)).setStringValue(Value);
603   return C;
604 }
605 
606 StringRef llvm::lexMIToken(StringRef Source, MIToken &Token,
607                            ErrorCallbackType ErrorCallback) {
608   auto C = skipComment(skipWhitespace(Cursor(Source)));
609   if (C.isEOF()) {
610     Token.reset(MIToken::Eof, C.remaining());
611     return C.remaining();
612   }
613 
614   if (Cursor R = maybeLexIntegerOrScalarType(C, Token))
615     return R.remaining();
616   if (Cursor R = maybeLexMachineBasicBlock(C, Token, ErrorCallback))
617     return R.remaining();
618   if (Cursor R = maybeLexIdentifier(C, Token))
619     return R.remaining();
620   if (Cursor R = maybeLexJumpTableIndex(C, Token))
621     return R.remaining();
622   if (Cursor R = maybeLexStackObject(C, Token))
623     return R.remaining();
624   if (Cursor R = maybeLexFixedStackObject(C, Token))
625     return R.remaining();
626   if (Cursor R = maybeLexConstantPoolItem(C, Token))
627     return R.remaining();
628   if (Cursor R = maybeLexSubRegisterIndex(C, Token, ErrorCallback))
629     return R.remaining();
630   if (Cursor R = maybeLexIRBlock(C, Token, ErrorCallback))
631     return R.remaining();
632   if (Cursor R = maybeLexIRValue(C, Token, ErrorCallback))
633     return R.remaining();
634   if (Cursor R = maybeLexRegister(C, Token))
635     return R.remaining();
636   if (Cursor R = maybeLexGlobalValue(C, Token, ErrorCallback))
637     return R.remaining();
638   if (Cursor R = maybeLexExternalSymbol(C, Token, ErrorCallback))
639     return R.remaining();
640   if (Cursor R = maybeLexHexadecimalLiteral(C, Token))
641     return R.remaining();
642   if (Cursor R = maybeLexNumericalLiteral(C, Token))
643     return R.remaining();
644   if (Cursor R = maybeLexExlaim(C, Token, ErrorCallback))
645     return R.remaining();
646   if (Cursor R = maybeLexSymbol(C, Token))
647     return R.remaining();
648   if (Cursor R = maybeLexNewline(C, Token))
649     return R.remaining();
650   if (Cursor R = maybeLexEscapedIRValue(C, Token, ErrorCallback))
651     return R.remaining();
652   if (Cursor R = maybeLexStringConstant(C, Token, ErrorCallback))
653     return R.remaining();
654 
655   Token.reset(MIToken::Error, C.remaining());
656   ErrorCallback(C.location(),
657                 Twine("unexpected character '") + Twine(C.peek()) + "'");
658   return C.remaining();
659 }
660