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("frame-destroy", MIToken::kw_frame_destroy)
215       .Case("debug-location", MIToken::kw_debug_location)
216       .Case("same_value", MIToken::kw_cfi_same_value)
217       .Case("offset", MIToken::kw_cfi_offset)
218       .Case("rel_offset", MIToken::kw_cfi_rel_offset)
219       .Case("def_cfa_register", MIToken::kw_cfi_def_cfa_register)
220       .Case("def_cfa_offset", MIToken::kw_cfi_def_cfa_offset)
221       .Case("adjust_cfa_offset", MIToken::kw_cfi_adjust_cfa_offset)
222       .Case("escape", MIToken::kw_cfi_escape)
223       .Case("def_cfa", MIToken::kw_cfi_def_cfa)
224       .Case("remember_state", MIToken::kw_cfi_remember_state)
225       .Case("restore", MIToken::kw_cfi_restore)
226       .Case("restore_state", MIToken::kw_cfi_restore_state)
227       .Case("undefined", MIToken::kw_cfi_undefined)
228       .Case("register", MIToken::kw_cfi_register)
229       .Case("window_save", MIToken::kw_cfi_window_save)
230       .Case("blockaddress", MIToken::kw_blockaddress)
231       .Case("intrinsic", MIToken::kw_intrinsic)
232       .Case("target-index", MIToken::kw_target_index)
233       .Case("half", MIToken::kw_half)
234       .Case("float", MIToken::kw_float)
235       .Case("double", MIToken::kw_double)
236       .Case("x86_fp80", MIToken::kw_x86_fp80)
237       .Case("fp128", MIToken::kw_fp128)
238       .Case("ppc_fp128", MIToken::kw_ppc_fp128)
239       .Case("target-flags", MIToken::kw_target_flags)
240       .Case("volatile", MIToken::kw_volatile)
241       .Case("non-temporal", MIToken::kw_non_temporal)
242       .Case("dereferenceable", MIToken::kw_dereferenceable)
243       .Case("invariant", MIToken::kw_invariant)
244       .Case("align", MIToken::kw_align)
245       .Case("stack", MIToken::kw_stack)
246       .Case("got", MIToken::kw_got)
247       .Case("jump-table", MIToken::kw_jump_table)
248       .Case("constant-pool", MIToken::kw_constant_pool)
249       .Case("call-entry", MIToken::kw_call_entry)
250       .Case("liveout", MIToken::kw_liveout)
251       .Case("address-taken", MIToken::kw_address_taken)
252       .Case("landing-pad", MIToken::kw_landing_pad)
253       .Case("liveins", MIToken::kw_liveins)
254       .Case("successors", MIToken::kw_successors)
255       .Case("floatpred", MIToken::kw_floatpred)
256       .Case("intpred", MIToken::kw_intpred)
257       .Default(MIToken::Identifier);
258 }
259 
260 static Cursor maybeLexIdentifier(Cursor C, MIToken &Token) {
261   if (!isalpha(C.peek()) && C.peek() != '_')
262     return None;
263   auto Range = C;
264   while (isIdentifierChar(C.peek()))
265     C.advance();
266   auto Identifier = Range.upto(C);
267   Token.reset(getIdentifierKind(Identifier), Identifier)
268       .setStringValue(Identifier);
269   return C;
270 }
271 
272 static Cursor maybeLexMachineBasicBlock(Cursor C, MIToken &Token,
273                                         ErrorCallbackType ErrorCallback) {
274   bool IsReference = C.remaining().startswith("%bb.");
275   if (!IsReference && !C.remaining().startswith("bb."))
276     return None;
277   auto Range = C;
278   unsigned PrefixLength = IsReference ? 4 : 3;
279   C.advance(PrefixLength); // Skip '%bb.' or 'bb.'
280   if (!isdigit(C.peek())) {
281     Token.reset(MIToken::Error, C.remaining());
282     ErrorCallback(C.location(), "expected a number after '%bb.'");
283     return C;
284   }
285   auto NumberRange = C;
286   while (isdigit(C.peek()))
287     C.advance();
288   StringRef Number = NumberRange.upto(C);
289   unsigned StringOffset = PrefixLength + Number.size(); // Drop '%bb.<id>'
290   // TODO: The format bb.<id>.<irname> is supported only when it's not a
291   // reference. Once we deprecate the format where the irname shows up, we
292   // should only lex forward if it is a reference.
293   if (C.peek() == '.') {
294     C.advance(); // Skip '.'
295     ++StringOffset;
296     while (isIdentifierChar(C.peek()))
297       C.advance();
298   }
299   Token.reset(IsReference ? MIToken::MachineBasicBlock
300                           : MIToken::MachineBasicBlockLabel,
301               Range.upto(C))
302       .setIntegerValue(APSInt(Number))
303       .setStringValue(Range.upto(C).drop_front(StringOffset));
304   return C;
305 }
306 
307 static Cursor maybeLexIndex(Cursor C, MIToken &Token, StringRef Rule,
308                             MIToken::TokenKind Kind) {
309   if (!C.remaining().startswith(Rule) || !isdigit(C.peek(Rule.size())))
310     return None;
311   auto Range = C;
312   C.advance(Rule.size());
313   auto NumberRange = C;
314   while (isdigit(C.peek()))
315     C.advance();
316   Token.reset(Kind, Range.upto(C)).setIntegerValue(APSInt(NumberRange.upto(C)));
317   return C;
318 }
319 
320 static Cursor maybeLexIndexAndName(Cursor C, MIToken &Token, StringRef Rule,
321                                    MIToken::TokenKind Kind) {
322   if (!C.remaining().startswith(Rule) || !isdigit(C.peek(Rule.size())))
323     return None;
324   auto Range = C;
325   C.advance(Rule.size());
326   auto NumberRange = C;
327   while (isdigit(C.peek()))
328     C.advance();
329   StringRef Number = NumberRange.upto(C);
330   unsigned StringOffset = Rule.size() + Number.size();
331   if (C.peek() == '.') {
332     C.advance();
333     ++StringOffset;
334     while (isIdentifierChar(C.peek()))
335       C.advance();
336   }
337   Token.reset(Kind, Range.upto(C))
338       .setIntegerValue(APSInt(Number))
339       .setStringValue(Range.upto(C).drop_front(StringOffset));
340   return C;
341 }
342 
343 static Cursor maybeLexJumpTableIndex(Cursor C, MIToken &Token) {
344   return maybeLexIndex(C, Token, "%jump-table.", MIToken::JumpTableIndex);
345 }
346 
347 static Cursor maybeLexStackObject(Cursor C, MIToken &Token) {
348   return maybeLexIndexAndName(C, Token, "%stack.", MIToken::StackObject);
349 }
350 
351 static Cursor maybeLexFixedStackObject(Cursor C, MIToken &Token) {
352   return maybeLexIndex(C, Token, "%fixed-stack.", MIToken::FixedStackObject);
353 }
354 
355 static Cursor maybeLexConstantPoolItem(Cursor C, MIToken &Token) {
356   return maybeLexIndex(C, Token, "%const.", MIToken::ConstantPoolItem);
357 }
358 
359 static Cursor maybeLexSubRegisterIndex(Cursor C, MIToken &Token,
360                                        ErrorCallbackType ErrorCallback) {
361   const StringRef Rule = "%subreg.";
362   if (!C.remaining().startswith(Rule))
363     return None;
364   return lexName(C, Token, MIToken::SubRegisterIndex, Rule.size(),
365                  ErrorCallback);
366 }
367 
368 static Cursor maybeLexIRBlock(Cursor C, MIToken &Token,
369                               ErrorCallbackType ErrorCallback) {
370   const StringRef Rule = "%ir-block.";
371   if (!C.remaining().startswith(Rule))
372     return None;
373   if (isdigit(C.peek(Rule.size())))
374     return maybeLexIndex(C, Token, Rule, MIToken::IRBlock);
375   return lexName(C, Token, MIToken::NamedIRBlock, Rule.size(), ErrorCallback);
376 }
377 
378 static Cursor maybeLexIRValue(Cursor C, MIToken &Token,
379                               ErrorCallbackType ErrorCallback) {
380   const StringRef Rule = "%ir.";
381   if (!C.remaining().startswith(Rule))
382     return None;
383   if (isdigit(C.peek(Rule.size())))
384     return maybeLexIndex(C, Token, Rule, MIToken::IRValue);
385   return lexName(C, Token, MIToken::NamedIRValue, Rule.size(), ErrorCallback);
386 }
387 
388 static Cursor maybeLexStringConstant(Cursor C, MIToken &Token,
389                                      ErrorCallbackType ErrorCallback) {
390   if (C.peek() != '"')
391     return None;
392   return lexName(C, Token, MIToken::StringConstant, /*PrefixLength=*/0,
393                  ErrorCallback);
394 }
395 
396 static Cursor lexVirtualRegister(Cursor C, MIToken &Token) {
397   auto Range = C;
398   C.advance(); // Skip '%'
399   auto NumberRange = C;
400   while (isdigit(C.peek()))
401     C.advance();
402   Token.reset(MIToken::VirtualRegister, Range.upto(C))
403       .setIntegerValue(APSInt(NumberRange.upto(C)));
404   return C;
405 }
406 
407 /// Returns true for a character allowed in a register name.
408 static bool isRegisterChar(char C) {
409   return isIdentifierChar(C) && C != '.';
410 }
411 
412 static Cursor maybeLexRegister(Cursor C, MIToken &Token) {
413   if (C.peek() != '%')
414     return None;
415   if (isdigit(C.peek(1)))
416     return lexVirtualRegister(C, Token);
417   auto Range = C;
418   C.advance(); // Skip '%'
419   while (isRegisterChar(C.peek()))
420     C.advance();
421   Token.reset(MIToken::NamedRegister, Range.upto(C))
422       .setStringValue(Range.upto(C).drop_front(1)); // Drop the '%'
423   return C;
424 }
425 
426 static Cursor maybeLexGlobalValue(Cursor C, MIToken &Token,
427                                   ErrorCallbackType ErrorCallback) {
428   if (C.peek() != '@')
429     return None;
430   if (!isdigit(C.peek(1)))
431     return lexName(C, Token, MIToken::NamedGlobalValue, /*PrefixLength=*/1,
432                    ErrorCallback);
433   auto Range = C;
434   C.advance(1); // Skip the '@'
435   auto NumberRange = C;
436   while (isdigit(C.peek()))
437     C.advance();
438   Token.reset(MIToken::GlobalValue, Range.upto(C))
439       .setIntegerValue(APSInt(NumberRange.upto(C)));
440   return C;
441 }
442 
443 static Cursor maybeLexExternalSymbol(Cursor C, MIToken &Token,
444                                      ErrorCallbackType ErrorCallback) {
445   if (C.peek() != '&')
446     return None;
447   return lexName(C, Token, MIToken::ExternalSymbol, /*PrefixLength=*/1,
448                  ErrorCallback);
449 }
450 
451 static bool isValidHexFloatingPointPrefix(char C) {
452   return C == 'H' || C == 'K' || C == 'L' || C == 'M';
453 }
454 
455 static Cursor lexFloatingPointLiteral(Cursor Range, Cursor C, MIToken &Token) {
456   C.advance();
457   // Skip over [0-9]*([eE][-+]?[0-9]+)?
458   while (isdigit(C.peek()))
459     C.advance();
460   if ((C.peek() == 'e' || C.peek() == 'E') &&
461       (isdigit(C.peek(1)) ||
462        ((C.peek(1) == '-' || C.peek(1) == '+') && isdigit(C.peek(2))))) {
463     C.advance(2);
464     while (isdigit(C.peek()))
465       C.advance();
466   }
467   Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
468   return C;
469 }
470 
471 static Cursor maybeLexHexadecimalLiteral(Cursor C, MIToken &Token) {
472   if (C.peek() != '0' || (C.peek(1) != 'x' && C.peek(1) != 'X'))
473     return None;
474   Cursor Range = C;
475   C.advance(2);
476   unsigned PrefLen = 2;
477   if (isValidHexFloatingPointPrefix(C.peek())) {
478     C.advance();
479     PrefLen++;
480   }
481   while (isxdigit(C.peek()))
482     C.advance();
483   StringRef StrVal = Range.upto(C);
484   if (StrVal.size() <= PrefLen)
485     return None;
486   if (PrefLen == 2)
487     Token.reset(MIToken::HexLiteral, Range.upto(C));
488   else // It must be 3, which means that there was a floating-point prefix.
489     Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
490   return C;
491 }
492 
493 static Cursor maybeLexNumericalLiteral(Cursor C, MIToken &Token) {
494   if (!isdigit(C.peek()) && (C.peek() != '-' || !isdigit(C.peek(1))))
495     return None;
496   auto Range = C;
497   C.advance();
498   while (isdigit(C.peek()))
499     C.advance();
500   if (C.peek() == '.')
501     return lexFloatingPointLiteral(Range, C, Token);
502   StringRef StrVal = Range.upto(C);
503   Token.reset(MIToken::IntegerLiteral, StrVal).setIntegerValue(APSInt(StrVal));
504   return C;
505 }
506 
507 static MIToken::TokenKind getMetadataKeywordKind(StringRef Identifier) {
508   return StringSwitch<MIToken::TokenKind>(Identifier)
509       .Case("!tbaa", MIToken::md_tbaa)
510       .Case("!alias.scope", MIToken::md_alias_scope)
511       .Case("!noalias", MIToken::md_noalias)
512       .Case("!range", MIToken::md_range)
513       .Case("!DIExpression", MIToken::md_diexpr)
514       .Default(MIToken::Error);
515 }
516 
517 static Cursor maybeLexExlaim(Cursor C, MIToken &Token,
518                              ErrorCallbackType ErrorCallback) {
519   if (C.peek() != '!')
520     return None;
521   auto Range = C;
522   C.advance(1);
523   if (isdigit(C.peek()) || !isIdentifierChar(C.peek())) {
524     Token.reset(MIToken::exclaim, Range.upto(C));
525     return C;
526   }
527   while (isIdentifierChar(C.peek()))
528     C.advance();
529   StringRef StrVal = Range.upto(C);
530   Token.reset(getMetadataKeywordKind(StrVal), StrVal);
531   if (Token.isError())
532     ErrorCallback(Token.location(),
533                   "use of unknown metadata keyword '" + StrVal + "'");
534   return C;
535 }
536 
537 static MIToken::TokenKind symbolToken(char C) {
538   switch (C) {
539   case ',':
540     return MIToken::comma;
541   case '.':
542     return MIToken::dot;
543   case '=':
544     return MIToken::equal;
545   case ':':
546     return MIToken::colon;
547   case '(':
548     return MIToken::lparen;
549   case ')':
550     return MIToken::rparen;
551   case '{':
552     return MIToken::lbrace;
553   case '}':
554     return MIToken::rbrace;
555   case '+':
556     return MIToken::plus;
557   case '-':
558     return MIToken::minus;
559   case '<':
560     return MIToken::less;
561   case '>':
562     return MIToken::greater;
563   default:
564     return MIToken::Error;
565   }
566 }
567 
568 static Cursor maybeLexSymbol(Cursor C, MIToken &Token) {
569   MIToken::TokenKind Kind;
570   unsigned Length = 1;
571   if (C.peek() == ':' && C.peek(1) == ':') {
572     Kind = MIToken::coloncolon;
573     Length = 2;
574   } else
575     Kind = symbolToken(C.peek());
576   if (Kind == MIToken::Error)
577     return None;
578   auto Range = C;
579   C.advance(Length);
580   Token.reset(Kind, Range.upto(C));
581   return C;
582 }
583 
584 static Cursor maybeLexNewline(Cursor C, MIToken &Token) {
585   if (!isNewlineChar(C.peek()))
586     return None;
587   auto Range = C;
588   C.advance();
589   Token.reset(MIToken::Newline, Range.upto(C));
590   return C;
591 }
592 
593 static Cursor maybeLexEscapedIRValue(Cursor C, MIToken &Token,
594                                      ErrorCallbackType ErrorCallback) {
595   if (C.peek() != '`')
596     return None;
597   auto Range = C;
598   C.advance();
599   auto StrRange = C;
600   while (C.peek() != '`') {
601     if (C.isEOF() || isNewlineChar(C.peek())) {
602       ErrorCallback(
603           C.location(),
604           "end of machine instruction reached before the closing '`'");
605       Token.reset(MIToken::Error, Range.remaining());
606       return C;
607     }
608     C.advance();
609   }
610   StringRef Value = StrRange.upto(C);
611   C.advance();
612   Token.reset(MIToken::QuotedIRValue, Range.upto(C)).setStringValue(Value);
613   return C;
614 }
615 
616 StringRef llvm::lexMIToken(StringRef Source, MIToken &Token,
617                            ErrorCallbackType ErrorCallback) {
618   auto C = skipComment(skipWhitespace(Cursor(Source)));
619   if (C.isEOF()) {
620     Token.reset(MIToken::Eof, C.remaining());
621     return C.remaining();
622   }
623 
624   if (Cursor R = maybeLexIntegerOrScalarType(C, Token))
625     return R.remaining();
626   if (Cursor R = maybeLexMachineBasicBlock(C, Token, ErrorCallback))
627     return R.remaining();
628   if (Cursor R = maybeLexIdentifier(C, Token))
629     return R.remaining();
630   if (Cursor R = maybeLexJumpTableIndex(C, Token))
631     return R.remaining();
632   if (Cursor R = maybeLexStackObject(C, Token))
633     return R.remaining();
634   if (Cursor R = maybeLexFixedStackObject(C, Token))
635     return R.remaining();
636   if (Cursor R = maybeLexConstantPoolItem(C, Token))
637     return R.remaining();
638   if (Cursor R = maybeLexSubRegisterIndex(C, Token, ErrorCallback))
639     return R.remaining();
640   if (Cursor R = maybeLexIRBlock(C, Token, ErrorCallback))
641     return R.remaining();
642   if (Cursor R = maybeLexIRValue(C, Token, ErrorCallback))
643     return R.remaining();
644   if (Cursor R = maybeLexRegister(C, Token))
645     return R.remaining();
646   if (Cursor R = maybeLexGlobalValue(C, Token, ErrorCallback))
647     return R.remaining();
648   if (Cursor R = maybeLexExternalSymbol(C, Token, ErrorCallback))
649     return R.remaining();
650   if (Cursor R = maybeLexHexadecimalLiteral(C, Token))
651     return R.remaining();
652   if (Cursor R = maybeLexNumericalLiteral(C, Token))
653     return R.remaining();
654   if (Cursor R = maybeLexExlaim(C, Token, ErrorCallback))
655     return R.remaining();
656   if (Cursor R = maybeLexSymbol(C, Token))
657     return R.remaining();
658   if (Cursor R = maybeLexNewline(C, Token))
659     return R.remaining();
660   if (Cursor R = maybeLexEscapedIRValue(C, Token, ErrorCallback))
661     return R.remaining();
662   if (Cursor R = maybeLexStringConstant(C, Token, ErrorCallback))
663     return R.remaining();
664 
665   Token.reset(MIToken::Error, C.remaining());
666   ErrorCallback(C.location(),
667                 Twine("unexpected character '") + Twine(C.peek()) + "'");
668   return C.remaining();
669 }
670