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("renamable", MIToken::kw_renamable)
212       .Case("tied-def", MIToken::kw_tied_def)
213       .Case("frame-setup", MIToken::kw_frame_setup)
214       .Case("debug-location", MIToken::kw_debug_location)
215       .Case("same_value", MIToken::kw_cfi_same_value)
216       .Case("offset", MIToken::kw_cfi_offset)
217       .Case("def_cfa_register", MIToken::kw_cfi_def_cfa_register)
218       .Case("def_cfa_offset", MIToken::kw_cfi_def_cfa_offset)
219       .Case("def_cfa", MIToken::kw_cfi_def_cfa)
220       .Case("restore", MIToken::kw_cfi_restore)
221       .Case("blockaddress", MIToken::kw_blockaddress)
222       .Case("intrinsic", MIToken::kw_intrinsic)
223       .Case("target-index", MIToken::kw_target_index)
224       .Case("half", MIToken::kw_half)
225       .Case("float", MIToken::kw_float)
226       .Case("double", MIToken::kw_double)
227       .Case("x86_fp80", MIToken::kw_x86_fp80)
228       .Case("fp128", MIToken::kw_fp128)
229       .Case("ppc_fp128", MIToken::kw_ppc_fp128)
230       .Case("target-flags", MIToken::kw_target_flags)
231       .Case("volatile", MIToken::kw_volatile)
232       .Case("non-temporal", MIToken::kw_non_temporal)
233       .Case("dereferenceable", MIToken::kw_dereferenceable)
234       .Case("invariant", MIToken::kw_invariant)
235       .Case("align", MIToken::kw_align)
236       .Case("stack", MIToken::kw_stack)
237       .Case("got", MIToken::kw_got)
238       .Case("jump-table", MIToken::kw_jump_table)
239       .Case("constant-pool", MIToken::kw_constant_pool)
240       .Case("call-entry", MIToken::kw_call_entry)
241       .Case("liveout", MIToken::kw_liveout)
242       .Case("address-taken", MIToken::kw_address_taken)
243       .Case("landing-pad", MIToken::kw_landing_pad)
244       .Case("liveins", MIToken::kw_liveins)
245       .Case("successors", MIToken::kw_successors)
246       .Case("floatpred", MIToken::kw_floatpred)
247       .Case("intpred", MIToken::kw_intpred)
248       .Default(MIToken::Identifier);
249 }
250 
251 static Cursor maybeLexIdentifier(Cursor C, MIToken &Token) {
252   if (!isalpha(C.peek()) && C.peek() != '_')
253     return None;
254   auto Range = C;
255   while (isIdentifierChar(C.peek()))
256     C.advance();
257   auto Identifier = Range.upto(C);
258   Token.reset(getIdentifierKind(Identifier), Identifier)
259       .setStringValue(Identifier);
260   return C;
261 }
262 
263 static Cursor maybeLexMachineBasicBlock(Cursor C, MIToken &Token,
264                                         ErrorCallbackType ErrorCallback) {
265   bool IsReference = C.remaining().startswith("%bb.");
266   if (!IsReference && !C.remaining().startswith("bb."))
267     return None;
268   auto Range = C;
269   unsigned PrefixLength = IsReference ? 4 : 3;
270   C.advance(PrefixLength); // Skip '%bb.' or 'bb.'
271   if (!isdigit(C.peek())) {
272     Token.reset(MIToken::Error, C.remaining());
273     ErrorCallback(C.location(), "expected a number after '%bb.'");
274     return C;
275   }
276   auto NumberRange = C;
277   while (isdigit(C.peek()))
278     C.advance();
279   StringRef Number = NumberRange.upto(C);
280   unsigned StringOffset = PrefixLength + Number.size(); // Drop '%bb.<id>'
281   // TODO: The format bb.<id>.<irname> is supported only when it's not a
282   // reference. Once we deprecate the format where the irname shows up, we
283   // should only lex forward if it is a reference.
284   if (C.peek() == '.') {
285     C.advance(); // Skip '.'
286     ++StringOffset;
287     while (isIdentifierChar(C.peek()))
288       C.advance();
289   }
290   Token.reset(IsReference ? MIToken::MachineBasicBlock
291                           : MIToken::MachineBasicBlockLabel,
292               Range.upto(C))
293       .setIntegerValue(APSInt(Number))
294       .setStringValue(Range.upto(C).drop_front(StringOffset));
295   return C;
296 }
297 
298 static Cursor maybeLexIndex(Cursor C, MIToken &Token, StringRef Rule,
299                             MIToken::TokenKind Kind) {
300   if (!C.remaining().startswith(Rule) || !isdigit(C.peek(Rule.size())))
301     return None;
302   auto Range = C;
303   C.advance(Rule.size());
304   auto NumberRange = C;
305   while (isdigit(C.peek()))
306     C.advance();
307   Token.reset(Kind, Range.upto(C)).setIntegerValue(APSInt(NumberRange.upto(C)));
308   return C;
309 }
310 
311 static Cursor maybeLexIndexAndName(Cursor C, MIToken &Token, StringRef Rule,
312                                    MIToken::TokenKind Kind) {
313   if (!C.remaining().startswith(Rule) || !isdigit(C.peek(Rule.size())))
314     return None;
315   auto Range = C;
316   C.advance(Rule.size());
317   auto NumberRange = C;
318   while (isdigit(C.peek()))
319     C.advance();
320   StringRef Number = NumberRange.upto(C);
321   unsigned StringOffset = Rule.size() + Number.size();
322   if (C.peek() == '.') {
323     C.advance();
324     ++StringOffset;
325     while (isIdentifierChar(C.peek()))
326       C.advance();
327   }
328   Token.reset(Kind, Range.upto(C))
329       .setIntegerValue(APSInt(Number))
330       .setStringValue(Range.upto(C).drop_front(StringOffset));
331   return C;
332 }
333 
334 static Cursor maybeLexJumpTableIndex(Cursor C, MIToken &Token) {
335   return maybeLexIndex(C, Token, "%jump-table.", MIToken::JumpTableIndex);
336 }
337 
338 static Cursor maybeLexStackObject(Cursor C, MIToken &Token) {
339   return maybeLexIndexAndName(C, Token, "%stack.", MIToken::StackObject);
340 }
341 
342 static Cursor maybeLexFixedStackObject(Cursor C, MIToken &Token) {
343   return maybeLexIndex(C, Token, "%fixed-stack.", MIToken::FixedStackObject);
344 }
345 
346 static Cursor maybeLexConstantPoolItem(Cursor C, MIToken &Token) {
347   return maybeLexIndex(C, Token, "%const.", MIToken::ConstantPoolItem);
348 }
349 
350 static Cursor maybeLexSubRegisterIndex(Cursor C, MIToken &Token,
351                                        ErrorCallbackType ErrorCallback) {
352   const StringRef Rule = "%subreg.";
353   if (!C.remaining().startswith(Rule))
354     return None;
355   return lexName(C, Token, MIToken::SubRegisterIndex, Rule.size(),
356                  ErrorCallback);
357 }
358 
359 static Cursor maybeLexIRBlock(Cursor C, MIToken &Token,
360                               ErrorCallbackType ErrorCallback) {
361   const StringRef Rule = "%ir-block.";
362   if (!C.remaining().startswith(Rule))
363     return None;
364   if (isdigit(C.peek(Rule.size())))
365     return maybeLexIndex(C, Token, Rule, MIToken::IRBlock);
366   return lexName(C, Token, MIToken::NamedIRBlock, Rule.size(), ErrorCallback);
367 }
368 
369 static Cursor maybeLexIRValue(Cursor C, MIToken &Token,
370                               ErrorCallbackType ErrorCallback) {
371   const StringRef Rule = "%ir.";
372   if (!C.remaining().startswith(Rule))
373     return None;
374   if (isdigit(C.peek(Rule.size())))
375     return maybeLexIndex(C, Token, Rule, MIToken::IRValue);
376   return lexName(C, Token, MIToken::NamedIRValue, Rule.size(), ErrorCallback);
377 }
378 
379 static Cursor maybeLexStringConstant(Cursor C, MIToken &Token,
380                                      ErrorCallbackType ErrorCallback) {
381   if (C.peek() != '"')
382     return None;
383   return lexName(C, Token, MIToken::StringConstant, /*PrefixLength=*/0,
384                  ErrorCallback);
385 }
386 
387 static Cursor lexVirtualRegister(Cursor C, MIToken &Token) {
388   auto Range = C;
389   C.advance(); // Skip '%'
390   auto NumberRange = C;
391   while (isdigit(C.peek()))
392     C.advance();
393   Token.reset(MIToken::VirtualRegister, Range.upto(C))
394       .setIntegerValue(APSInt(NumberRange.upto(C)));
395   return C;
396 }
397 
398 /// Returns true for a character allowed in a register name.
399 static bool isRegisterChar(char C) {
400   return isIdentifierChar(C) && C != '.';
401 }
402 
403 static Cursor maybeLexRegister(Cursor C, MIToken &Token) {
404   if (C.peek() != '%')
405     return None;
406   if (isdigit(C.peek(1)))
407     return lexVirtualRegister(C, Token);
408   auto Range = C;
409   C.advance(); // Skip '%'
410   while (isRegisterChar(C.peek()))
411     C.advance();
412   Token.reset(MIToken::NamedRegister, Range.upto(C))
413       .setStringValue(Range.upto(C).drop_front(1)); // Drop the '%'
414   return C;
415 }
416 
417 static Cursor maybeLexGlobalValue(Cursor C, MIToken &Token,
418                                   ErrorCallbackType ErrorCallback) {
419   if (C.peek() != '@')
420     return None;
421   if (!isdigit(C.peek(1)))
422     return lexName(C, Token, MIToken::NamedGlobalValue, /*PrefixLength=*/1,
423                    ErrorCallback);
424   auto Range = C;
425   C.advance(1); // Skip the '@'
426   auto NumberRange = C;
427   while (isdigit(C.peek()))
428     C.advance();
429   Token.reset(MIToken::GlobalValue, Range.upto(C))
430       .setIntegerValue(APSInt(NumberRange.upto(C)));
431   return C;
432 }
433 
434 static Cursor maybeLexExternalSymbol(Cursor C, MIToken &Token,
435                                      ErrorCallbackType ErrorCallback) {
436   if (C.peek() != '$')
437     return None;
438   return lexName(C, Token, MIToken::ExternalSymbol, /*PrefixLength=*/1,
439                  ErrorCallback);
440 }
441 
442 static bool isValidHexFloatingPointPrefix(char C) {
443   return C == 'H' || C == 'K' || C == 'L' || C == 'M';
444 }
445 
446 static Cursor lexFloatingPointLiteral(Cursor Range, Cursor C, MIToken &Token) {
447   C.advance();
448   // Skip over [0-9]*([eE][-+]?[0-9]+)?
449   while (isdigit(C.peek()))
450     C.advance();
451   if ((C.peek() == 'e' || C.peek() == 'E') &&
452       (isdigit(C.peek(1)) ||
453        ((C.peek(1) == '-' || C.peek(1) == '+') && isdigit(C.peek(2))))) {
454     C.advance(2);
455     while (isdigit(C.peek()))
456       C.advance();
457   }
458   Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
459   return C;
460 }
461 
462 static Cursor maybeLexHexadecimalLiteral(Cursor C, MIToken &Token) {
463   if (C.peek() != '0' || (C.peek(1) != 'x' && C.peek(1) != 'X'))
464     return None;
465   Cursor Range = C;
466   C.advance(2);
467   unsigned PrefLen = 2;
468   if (isValidHexFloatingPointPrefix(C.peek())) {
469     C.advance();
470     PrefLen++;
471   }
472   while (isxdigit(C.peek()))
473     C.advance();
474   StringRef StrVal = Range.upto(C);
475   if (StrVal.size() <= PrefLen)
476     return None;
477   if (PrefLen == 2)
478     Token.reset(MIToken::HexLiteral, Range.upto(C));
479   else // It must be 3, which means that there was a floating-point prefix.
480     Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
481   return C;
482 }
483 
484 static Cursor maybeLexNumericalLiteral(Cursor C, MIToken &Token) {
485   if (!isdigit(C.peek()) && (C.peek() != '-' || !isdigit(C.peek(1))))
486     return None;
487   auto Range = C;
488   C.advance();
489   while (isdigit(C.peek()))
490     C.advance();
491   if (C.peek() == '.')
492     return lexFloatingPointLiteral(Range, C, Token);
493   StringRef StrVal = Range.upto(C);
494   Token.reset(MIToken::IntegerLiteral, StrVal).setIntegerValue(APSInt(StrVal));
495   return C;
496 }
497 
498 static MIToken::TokenKind getMetadataKeywordKind(StringRef Identifier) {
499   return StringSwitch<MIToken::TokenKind>(Identifier)
500       .Case("!tbaa", MIToken::md_tbaa)
501       .Case("!alias.scope", MIToken::md_alias_scope)
502       .Case("!noalias", MIToken::md_noalias)
503       .Case("!range", MIToken::md_range)
504       .Case("!DIExpression", MIToken::md_diexpr)
505       .Default(MIToken::Error);
506 }
507 
508 static Cursor maybeLexExlaim(Cursor C, MIToken &Token,
509                              ErrorCallbackType ErrorCallback) {
510   if (C.peek() != '!')
511     return None;
512   auto Range = C;
513   C.advance(1);
514   if (isdigit(C.peek()) || !isIdentifierChar(C.peek())) {
515     Token.reset(MIToken::exclaim, Range.upto(C));
516     return C;
517   }
518   while (isIdentifierChar(C.peek()))
519     C.advance();
520   StringRef StrVal = Range.upto(C);
521   Token.reset(getMetadataKeywordKind(StrVal), StrVal);
522   if (Token.isError())
523     ErrorCallback(Token.location(),
524                   "use of unknown metadata keyword '" + StrVal + "'");
525   return C;
526 }
527 
528 static MIToken::TokenKind symbolToken(char C) {
529   switch (C) {
530   case ',':
531     return MIToken::comma;
532   case '.':
533     return MIToken::dot;
534   case '=':
535     return MIToken::equal;
536   case ':':
537     return MIToken::colon;
538   case '(':
539     return MIToken::lparen;
540   case ')':
541     return MIToken::rparen;
542   case '{':
543     return MIToken::lbrace;
544   case '}':
545     return MIToken::rbrace;
546   case '+':
547     return MIToken::plus;
548   case '-':
549     return MIToken::minus;
550   case '<':
551     return MIToken::less;
552   case '>':
553     return MIToken::greater;
554   default:
555     return MIToken::Error;
556   }
557 }
558 
559 static Cursor maybeLexSymbol(Cursor C, MIToken &Token) {
560   MIToken::TokenKind Kind;
561   unsigned Length = 1;
562   if (C.peek() == ':' && C.peek(1) == ':') {
563     Kind = MIToken::coloncolon;
564     Length = 2;
565   } else
566     Kind = symbolToken(C.peek());
567   if (Kind == MIToken::Error)
568     return None;
569   auto Range = C;
570   C.advance(Length);
571   Token.reset(Kind, Range.upto(C));
572   return C;
573 }
574 
575 static Cursor maybeLexNewline(Cursor C, MIToken &Token) {
576   if (!isNewlineChar(C.peek()))
577     return None;
578   auto Range = C;
579   C.advance();
580   Token.reset(MIToken::Newline, Range.upto(C));
581   return C;
582 }
583 
584 static Cursor maybeLexEscapedIRValue(Cursor C, MIToken &Token,
585                                      ErrorCallbackType ErrorCallback) {
586   if (C.peek() != '`')
587     return None;
588   auto Range = C;
589   C.advance();
590   auto StrRange = C;
591   while (C.peek() != '`') {
592     if (C.isEOF() || isNewlineChar(C.peek())) {
593       ErrorCallback(
594           C.location(),
595           "end of machine instruction reached before the closing '`'");
596       Token.reset(MIToken::Error, Range.remaining());
597       return C;
598     }
599     C.advance();
600   }
601   StringRef Value = StrRange.upto(C);
602   C.advance();
603   Token.reset(MIToken::QuotedIRValue, Range.upto(C)).setStringValue(Value);
604   return C;
605 }
606 
607 StringRef llvm::lexMIToken(StringRef Source, MIToken &Token,
608                            ErrorCallbackType ErrorCallback) {
609   auto C = skipComment(skipWhitespace(Cursor(Source)));
610   if (C.isEOF()) {
611     Token.reset(MIToken::Eof, C.remaining());
612     return C.remaining();
613   }
614 
615   if (Cursor R = maybeLexIntegerOrScalarType(C, Token))
616     return R.remaining();
617   if (Cursor R = maybeLexMachineBasicBlock(C, Token, ErrorCallback))
618     return R.remaining();
619   if (Cursor R = maybeLexIdentifier(C, Token))
620     return R.remaining();
621   if (Cursor R = maybeLexJumpTableIndex(C, Token))
622     return R.remaining();
623   if (Cursor R = maybeLexStackObject(C, Token))
624     return R.remaining();
625   if (Cursor R = maybeLexFixedStackObject(C, Token))
626     return R.remaining();
627   if (Cursor R = maybeLexConstantPoolItem(C, Token))
628     return R.remaining();
629   if (Cursor R = maybeLexSubRegisterIndex(C, Token, ErrorCallback))
630     return R.remaining();
631   if (Cursor R = maybeLexIRBlock(C, Token, ErrorCallback))
632     return R.remaining();
633   if (Cursor R = maybeLexIRValue(C, Token, ErrorCallback))
634     return R.remaining();
635   if (Cursor R = maybeLexRegister(C, Token))
636     return R.remaining();
637   if (Cursor R = maybeLexGlobalValue(C, Token, ErrorCallback))
638     return R.remaining();
639   if (Cursor R = maybeLexExternalSymbol(C, Token, ErrorCallback))
640     return R.remaining();
641   if (Cursor R = maybeLexHexadecimalLiteral(C, Token))
642     return R.remaining();
643   if (Cursor R = maybeLexNumericalLiteral(C, Token))
644     return R.remaining();
645   if (Cursor R = maybeLexExlaim(C, Token, ErrorCallback))
646     return R.remaining();
647   if (Cursor R = maybeLexSymbol(C, Token))
648     return R.remaining();
649   if (Cursor R = maybeLexNewline(C, Token))
650     return R.remaining();
651   if (Cursor R = maybeLexEscapedIRValue(C, Token, ErrorCallback))
652     return R.remaining();
653   if (Cursor R = maybeLexStringConstant(C, Token, ErrorCallback))
654     return R.remaining();
655 
656   Token.reset(MIToken::Error, C.remaining());
657   ErrorCallback(C.location(),
658                 Twine("unexpected character '") + Twine(C.peek()) + "'");
659   return C.remaining();
660 }
661