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("addrspace", MIToken::kw_addrspace)
246       .Case("stack", MIToken::kw_stack)
247       .Case("got", MIToken::kw_got)
248       .Case("jump-table", MIToken::kw_jump_table)
249       .Case("constant-pool", MIToken::kw_constant_pool)
250       .Case("call-entry", MIToken::kw_call_entry)
251       .Case("liveout", MIToken::kw_liveout)
252       .Case("address-taken", MIToken::kw_address_taken)
253       .Case("landing-pad", MIToken::kw_landing_pad)
254       .Case("liveins", MIToken::kw_liveins)
255       .Case("successors", MIToken::kw_successors)
256       .Case("floatpred", MIToken::kw_floatpred)
257       .Case("intpred", MIToken::kw_intpred)
258       .Default(MIToken::Identifier);
259 }
260 
261 static Cursor maybeLexIdentifier(Cursor C, MIToken &Token) {
262   if (!isalpha(C.peek()) && C.peek() != '_')
263     return None;
264   auto Range = C;
265   while (isIdentifierChar(C.peek()))
266     C.advance();
267   auto Identifier = Range.upto(C);
268   Token.reset(getIdentifierKind(Identifier), Identifier)
269       .setStringValue(Identifier);
270   return C;
271 }
272 
273 static Cursor maybeLexMachineBasicBlock(Cursor C, MIToken &Token,
274                                         ErrorCallbackType ErrorCallback) {
275   bool IsReference = C.remaining().startswith("%bb.");
276   if (!IsReference && !C.remaining().startswith("bb."))
277     return None;
278   auto Range = C;
279   unsigned PrefixLength = IsReference ? 4 : 3;
280   C.advance(PrefixLength); // Skip '%bb.' or 'bb.'
281   if (!isdigit(C.peek())) {
282     Token.reset(MIToken::Error, C.remaining());
283     ErrorCallback(C.location(), "expected a number after '%bb.'");
284     return C;
285   }
286   auto NumberRange = C;
287   while (isdigit(C.peek()))
288     C.advance();
289   StringRef Number = NumberRange.upto(C);
290   unsigned StringOffset = PrefixLength + Number.size(); // Drop '%bb.<id>'
291   // TODO: The format bb.<id>.<irname> is supported only when it's not a
292   // reference. Once we deprecate the format where the irname shows up, we
293   // should only lex forward if it is a reference.
294   if (C.peek() == '.') {
295     C.advance(); // Skip '.'
296     ++StringOffset;
297     while (isIdentifierChar(C.peek()))
298       C.advance();
299   }
300   Token.reset(IsReference ? MIToken::MachineBasicBlock
301                           : MIToken::MachineBasicBlockLabel,
302               Range.upto(C))
303       .setIntegerValue(APSInt(Number))
304       .setStringValue(Range.upto(C).drop_front(StringOffset));
305   return C;
306 }
307 
308 static Cursor maybeLexIndex(Cursor C, MIToken &Token, StringRef Rule,
309                             MIToken::TokenKind Kind) {
310   if (!C.remaining().startswith(Rule) || !isdigit(C.peek(Rule.size())))
311     return None;
312   auto Range = C;
313   C.advance(Rule.size());
314   auto NumberRange = C;
315   while (isdigit(C.peek()))
316     C.advance();
317   Token.reset(Kind, Range.upto(C)).setIntegerValue(APSInt(NumberRange.upto(C)));
318   return C;
319 }
320 
321 static Cursor maybeLexIndexAndName(Cursor C, MIToken &Token, StringRef Rule,
322                                    MIToken::TokenKind Kind) {
323   if (!C.remaining().startswith(Rule) || !isdigit(C.peek(Rule.size())))
324     return None;
325   auto Range = C;
326   C.advance(Rule.size());
327   auto NumberRange = C;
328   while (isdigit(C.peek()))
329     C.advance();
330   StringRef Number = NumberRange.upto(C);
331   unsigned StringOffset = Rule.size() + Number.size();
332   if (C.peek() == '.') {
333     C.advance();
334     ++StringOffset;
335     while (isIdentifierChar(C.peek()))
336       C.advance();
337   }
338   Token.reset(Kind, Range.upto(C))
339       .setIntegerValue(APSInt(Number))
340       .setStringValue(Range.upto(C).drop_front(StringOffset));
341   return C;
342 }
343 
344 static Cursor maybeLexJumpTableIndex(Cursor C, MIToken &Token) {
345   return maybeLexIndex(C, Token, "%jump-table.", MIToken::JumpTableIndex);
346 }
347 
348 static Cursor maybeLexStackObject(Cursor C, MIToken &Token) {
349   return maybeLexIndexAndName(C, Token, "%stack.", MIToken::StackObject);
350 }
351 
352 static Cursor maybeLexFixedStackObject(Cursor C, MIToken &Token) {
353   return maybeLexIndex(C, Token, "%fixed-stack.", MIToken::FixedStackObject);
354 }
355 
356 static Cursor maybeLexConstantPoolItem(Cursor C, MIToken &Token) {
357   return maybeLexIndex(C, Token, "%const.", MIToken::ConstantPoolItem);
358 }
359 
360 static Cursor maybeLexSubRegisterIndex(Cursor C, MIToken &Token,
361                                        ErrorCallbackType ErrorCallback) {
362   const StringRef Rule = "%subreg.";
363   if (!C.remaining().startswith(Rule))
364     return None;
365   return lexName(C, Token, MIToken::SubRegisterIndex, Rule.size(),
366                  ErrorCallback);
367 }
368 
369 static Cursor maybeLexIRBlock(Cursor C, MIToken &Token,
370                               ErrorCallbackType ErrorCallback) {
371   const StringRef Rule = "%ir-block.";
372   if (!C.remaining().startswith(Rule))
373     return None;
374   if (isdigit(C.peek(Rule.size())))
375     return maybeLexIndex(C, Token, Rule, MIToken::IRBlock);
376   return lexName(C, Token, MIToken::NamedIRBlock, Rule.size(), ErrorCallback);
377 }
378 
379 static Cursor maybeLexIRValue(Cursor C, MIToken &Token,
380                               ErrorCallbackType ErrorCallback) {
381   const StringRef Rule = "%ir.";
382   if (!C.remaining().startswith(Rule))
383     return None;
384   if (isdigit(C.peek(Rule.size())))
385     return maybeLexIndex(C, Token, Rule, MIToken::IRValue);
386   return lexName(C, Token, MIToken::NamedIRValue, Rule.size(), ErrorCallback);
387 }
388 
389 static Cursor maybeLexStringConstant(Cursor C, MIToken &Token,
390                                      ErrorCallbackType ErrorCallback) {
391   if (C.peek() != '"')
392     return None;
393   return lexName(C, Token, MIToken::StringConstant, /*PrefixLength=*/0,
394                  ErrorCallback);
395 }
396 
397 static Cursor lexVirtualRegister(Cursor C, MIToken &Token) {
398   auto Range = C;
399   C.advance(); // Skip '%'
400   auto NumberRange = C;
401   while (isdigit(C.peek()))
402     C.advance();
403   Token.reset(MIToken::VirtualRegister, Range.upto(C))
404       .setIntegerValue(APSInt(NumberRange.upto(C)));
405   return C;
406 }
407 
408 /// Returns true for a character allowed in a register name.
409 static bool isRegisterChar(char C) {
410   return isIdentifierChar(C) && C != '.';
411 }
412 
413 static Cursor maybeLexRegister(Cursor C, MIToken &Token) {
414   if (C.peek() != '%')
415     return None;
416   if (isdigit(C.peek(1)))
417     return lexVirtualRegister(C, Token);
418   auto Range = C;
419   C.advance(); // Skip '%'
420   while (isRegisterChar(C.peek()))
421     C.advance();
422   Token.reset(MIToken::NamedRegister, Range.upto(C))
423       .setStringValue(Range.upto(C).drop_front(1)); // Drop the '%'
424   return C;
425 }
426 
427 static Cursor maybeLexGlobalValue(Cursor C, MIToken &Token,
428                                   ErrorCallbackType ErrorCallback) {
429   if (C.peek() != '@')
430     return None;
431   if (!isdigit(C.peek(1)))
432     return lexName(C, Token, MIToken::NamedGlobalValue, /*PrefixLength=*/1,
433                    ErrorCallback);
434   auto Range = C;
435   C.advance(1); // Skip the '@'
436   auto NumberRange = C;
437   while (isdigit(C.peek()))
438     C.advance();
439   Token.reset(MIToken::GlobalValue, Range.upto(C))
440       .setIntegerValue(APSInt(NumberRange.upto(C)));
441   return C;
442 }
443 
444 static Cursor maybeLexExternalSymbol(Cursor C, MIToken &Token,
445                                      ErrorCallbackType ErrorCallback) {
446   if (C.peek() != '&')
447     return None;
448   return lexName(C, Token, MIToken::ExternalSymbol, /*PrefixLength=*/1,
449                  ErrorCallback);
450 }
451 
452 static bool isValidHexFloatingPointPrefix(char C) {
453   return C == 'H' || C == 'K' || C == 'L' || C == 'M';
454 }
455 
456 static Cursor lexFloatingPointLiteral(Cursor Range, Cursor C, MIToken &Token) {
457   C.advance();
458   // Skip over [0-9]*([eE][-+]?[0-9]+)?
459   while (isdigit(C.peek()))
460     C.advance();
461   if ((C.peek() == 'e' || C.peek() == 'E') &&
462       (isdigit(C.peek(1)) ||
463        ((C.peek(1) == '-' || C.peek(1) == '+') && isdigit(C.peek(2))))) {
464     C.advance(2);
465     while (isdigit(C.peek()))
466       C.advance();
467   }
468   Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
469   return C;
470 }
471 
472 static Cursor maybeLexHexadecimalLiteral(Cursor C, MIToken &Token) {
473   if (C.peek() != '0' || (C.peek(1) != 'x' && C.peek(1) != 'X'))
474     return None;
475   Cursor Range = C;
476   C.advance(2);
477   unsigned PrefLen = 2;
478   if (isValidHexFloatingPointPrefix(C.peek())) {
479     C.advance();
480     PrefLen++;
481   }
482   while (isxdigit(C.peek()))
483     C.advance();
484   StringRef StrVal = Range.upto(C);
485   if (StrVal.size() <= PrefLen)
486     return None;
487   if (PrefLen == 2)
488     Token.reset(MIToken::HexLiteral, Range.upto(C));
489   else // It must be 3, which means that there was a floating-point prefix.
490     Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
491   return C;
492 }
493 
494 static Cursor maybeLexNumericalLiteral(Cursor C, MIToken &Token) {
495   if (!isdigit(C.peek()) && (C.peek() != '-' || !isdigit(C.peek(1))))
496     return None;
497   auto Range = C;
498   C.advance();
499   while (isdigit(C.peek()))
500     C.advance();
501   if (C.peek() == '.')
502     return lexFloatingPointLiteral(Range, C, Token);
503   StringRef StrVal = Range.upto(C);
504   Token.reset(MIToken::IntegerLiteral, StrVal).setIntegerValue(APSInt(StrVal));
505   return C;
506 }
507 
508 static MIToken::TokenKind getMetadataKeywordKind(StringRef Identifier) {
509   return StringSwitch<MIToken::TokenKind>(Identifier)
510       .Case("!tbaa", MIToken::md_tbaa)
511       .Case("!alias.scope", MIToken::md_alias_scope)
512       .Case("!noalias", MIToken::md_noalias)
513       .Case("!range", MIToken::md_range)
514       .Case("!DIExpression", MIToken::md_diexpr)
515       .Default(MIToken::Error);
516 }
517 
518 static Cursor maybeLexExlaim(Cursor C, MIToken &Token,
519                              ErrorCallbackType ErrorCallback) {
520   if (C.peek() != '!')
521     return None;
522   auto Range = C;
523   C.advance(1);
524   if (isdigit(C.peek()) || !isIdentifierChar(C.peek())) {
525     Token.reset(MIToken::exclaim, Range.upto(C));
526     return C;
527   }
528   while (isIdentifierChar(C.peek()))
529     C.advance();
530   StringRef StrVal = Range.upto(C);
531   Token.reset(getMetadataKeywordKind(StrVal), StrVal);
532   if (Token.isError())
533     ErrorCallback(Token.location(),
534                   "use of unknown metadata keyword '" + StrVal + "'");
535   return C;
536 }
537 
538 static MIToken::TokenKind symbolToken(char C) {
539   switch (C) {
540   case ',':
541     return MIToken::comma;
542   case '.':
543     return MIToken::dot;
544   case '=':
545     return MIToken::equal;
546   case ':':
547     return MIToken::colon;
548   case '(':
549     return MIToken::lparen;
550   case ')':
551     return MIToken::rparen;
552   case '{':
553     return MIToken::lbrace;
554   case '}':
555     return MIToken::rbrace;
556   case '+':
557     return MIToken::plus;
558   case '-':
559     return MIToken::minus;
560   case '<':
561     return MIToken::less;
562   case '>':
563     return MIToken::greater;
564   default:
565     return MIToken::Error;
566   }
567 }
568 
569 static Cursor maybeLexSymbol(Cursor C, MIToken &Token) {
570   MIToken::TokenKind Kind;
571   unsigned Length = 1;
572   if (C.peek() == ':' && C.peek(1) == ':') {
573     Kind = MIToken::coloncolon;
574     Length = 2;
575   } else
576     Kind = symbolToken(C.peek());
577   if (Kind == MIToken::Error)
578     return None;
579   auto Range = C;
580   C.advance(Length);
581   Token.reset(Kind, Range.upto(C));
582   return C;
583 }
584 
585 static Cursor maybeLexNewline(Cursor C, MIToken &Token) {
586   if (!isNewlineChar(C.peek()))
587     return None;
588   auto Range = C;
589   C.advance();
590   Token.reset(MIToken::Newline, Range.upto(C));
591   return C;
592 }
593 
594 static Cursor maybeLexEscapedIRValue(Cursor C, MIToken &Token,
595                                      ErrorCallbackType ErrorCallback) {
596   if (C.peek() != '`')
597     return None;
598   auto Range = C;
599   C.advance();
600   auto StrRange = C;
601   while (C.peek() != '`') {
602     if (C.isEOF() || isNewlineChar(C.peek())) {
603       ErrorCallback(
604           C.location(),
605           "end of machine instruction reached before the closing '`'");
606       Token.reset(MIToken::Error, Range.remaining());
607       return C;
608     }
609     C.advance();
610   }
611   StringRef Value = StrRange.upto(C);
612   C.advance();
613   Token.reset(MIToken::QuotedIRValue, Range.upto(C)).setStringValue(Value);
614   return C;
615 }
616 
617 StringRef llvm::lexMIToken(StringRef Source, MIToken &Token,
618                            ErrorCallbackType ErrorCallback) {
619   auto C = skipComment(skipWhitespace(Cursor(Source)));
620   if (C.isEOF()) {
621     Token.reset(MIToken::Eof, C.remaining());
622     return C.remaining();
623   }
624 
625   if (Cursor R = maybeLexIntegerOrScalarType(C, Token))
626     return R.remaining();
627   if (Cursor R = maybeLexMachineBasicBlock(C, Token, ErrorCallback))
628     return R.remaining();
629   if (Cursor R = maybeLexIdentifier(C, Token))
630     return R.remaining();
631   if (Cursor R = maybeLexJumpTableIndex(C, Token))
632     return R.remaining();
633   if (Cursor R = maybeLexStackObject(C, Token))
634     return R.remaining();
635   if (Cursor R = maybeLexFixedStackObject(C, Token))
636     return R.remaining();
637   if (Cursor R = maybeLexConstantPoolItem(C, Token))
638     return R.remaining();
639   if (Cursor R = maybeLexSubRegisterIndex(C, Token, ErrorCallback))
640     return R.remaining();
641   if (Cursor R = maybeLexIRBlock(C, Token, ErrorCallback))
642     return R.remaining();
643   if (Cursor R = maybeLexIRValue(C, Token, ErrorCallback))
644     return R.remaining();
645   if (Cursor R = maybeLexRegister(C, Token))
646     return R.remaining();
647   if (Cursor R = maybeLexGlobalValue(C, Token, ErrorCallback))
648     return R.remaining();
649   if (Cursor R = maybeLexExternalSymbol(C, Token, ErrorCallback))
650     return R.remaining();
651   if (Cursor R = maybeLexHexadecimalLiteral(C, Token))
652     return R.remaining();
653   if (Cursor R = maybeLexNumericalLiteral(C, Token))
654     return R.remaining();
655   if (Cursor R = maybeLexExlaim(C, Token, ErrorCallback))
656     return R.remaining();
657   if (Cursor R = maybeLexSymbol(C, Token))
658     return R.remaining();
659   if (Cursor R = maybeLexNewline(C, Token))
660     return R.remaining();
661   if (Cursor R = maybeLexEscapedIRValue(C, Token, ErrorCallback))
662     return R.remaining();
663   if (Cursor R = maybeLexStringConstant(C, Token, ErrorCallback))
664     return R.remaining();
665 
666   Token.reset(MIToken::Error, C.remaining());
667   ErrorCallback(C.location(),
668                 Twine("unexpected character '") + Twine(C.peek()) + "'");
669   return C.remaining();
670 }
671