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