1 //===- MILexer.cpp - Machine instructions lexer implementation ------------===//
2 //
3 // Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
4 // See https://llvm.org/LICENSE.txt for license information.
5 // SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
6 //
7 //===----------------------------------------------------------------------===//
8 //
9 // This file implements the lexing of machine instructions.
10 //
11 //===----------------------------------------------------------------------===//
12 
13 #include "MILexer.h"
14 #include "llvm/ADT/APSInt.h"
15 #include "llvm/ADT/None.h"
16 #include "llvm/ADT/STLExtras.h"
17 #include "llvm/ADT/StringExtras.h"
18 #include "llvm/ADT/StringSwitch.h"
19 #include "llvm/ADT/StringRef.h"
20 #include "llvm/ADT/Twine.h"
21 #include <algorithm>
22 #include <cassert>
23 #include <cctype>
24 #include <string>
25 
26 using namespace llvm;
27 
28 namespace {
29 
30 using ErrorCallbackType =
31     function_ref<void(StringRef::iterator Loc, const Twine &)>;
32 
33 /// This class provides a way to iterate and get characters from the source
34 /// string.
35 class Cursor {
36   const char *Ptr = nullptr;
37   const char *End = nullptr;
38 
39 public:
40   Cursor(NoneType) {}
41 
42   explicit Cursor(StringRef Str) {
43     Ptr = Str.data();
44     End = Ptr + Str.size();
45   }
46 
47   bool isEOF() const { return Ptr == End; }
48 
49   char peek(int I = 0) const { return End - Ptr <= I ? 0 : Ptr[I]; }
50 
51   void advance(unsigned I = 1) { Ptr += I; }
52 
53   StringRef remaining() const { return StringRef(Ptr, End - Ptr); }
54 
55   StringRef upto(Cursor C) const {
56     assert(C.Ptr >= Ptr && C.Ptr <= End);
57     return StringRef(Ptr, C.Ptr - Ptr);
58   }
59 
60   StringRef::iterator location() const { return Ptr; }
61 
62   operator bool() const { return Ptr != nullptr; }
63 };
64 
65 } // end anonymous namespace
66 
67 MIToken &MIToken::reset(TokenKind Kind, StringRef Range) {
68   this->Kind = Kind;
69   this->Range = Range;
70   return *this;
71 }
72 
73 MIToken &MIToken::setStringValue(StringRef StrVal) {
74   StringValue = StrVal;
75   return *this;
76 }
77 
78 MIToken &MIToken::setOwnedStringValue(std::string StrVal) {
79   StringValueStorage = std::move(StrVal);
80   StringValue = StringValueStorage;
81   return *this;
82 }
83 
84 MIToken &MIToken::setIntegerValue(APSInt IntVal) {
85   this->IntVal = std::move(IntVal);
86   return *this;
87 }
88 
89 /// Skip the leading whitespace characters and return the updated cursor.
90 static Cursor skipWhitespace(Cursor C) {
91   while (isblank(C.peek()))
92     C.advance();
93   return C;
94 }
95 
96 static bool isNewlineChar(char C) { return C == '\n' || C == '\r'; }
97 
98 /// Skip a line comment and return the updated cursor.
99 static Cursor skipComment(Cursor C) {
100   if (C.peek() != ';')
101     return C;
102   while (!isNewlineChar(C.peek()) && !C.isEOF())
103     C.advance();
104   return C;
105 }
106 
107 /// Return true if the given character satisfies the following regular
108 /// expression: [-a-zA-Z$._0-9]
109 static bool isIdentifierChar(char C) {
110   return isalpha(C) || isdigit(C) || C == '_' || C == '-' || C == '.' ||
111          C == '$';
112 }
113 
114 /// Unescapes the given string value.
115 ///
116 /// Expects the string value to be quoted.
117 static std::string unescapeQuotedString(StringRef Value) {
118   assert(Value.front() == '"' && Value.back() == '"');
119   Cursor C = Cursor(Value.substr(1, Value.size() - 2));
120 
121   std::string Str;
122   Str.reserve(C.remaining().size());
123   while (!C.isEOF()) {
124     char Char = C.peek();
125     if (Char == '\\') {
126       if (C.peek(1) == '\\') {
127         // Two '\' become one
128         Str += '\\';
129         C.advance(2);
130         continue;
131       }
132       if (isxdigit(C.peek(1)) && isxdigit(C.peek(2))) {
133         Str += hexDigitValue(C.peek(1)) * 16 + hexDigitValue(C.peek(2));
134         C.advance(3);
135         continue;
136       }
137     }
138     Str += Char;
139     C.advance();
140   }
141   return Str;
142 }
143 
144 /// Lex a string constant using the following regular expression: \"[^\"]*\"
145 static Cursor lexStringConstant(Cursor C, ErrorCallbackType ErrorCallback) {
146   assert(C.peek() == '"');
147   for (C.advance(); C.peek() != '"'; C.advance()) {
148     if (C.isEOF() || isNewlineChar(C.peek())) {
149       ErrorCallback(
150           C.location(),
151           "end of machine instruction reached before the closing '\"'");
152       return None;
153     }
154   }
155   C.advance();
156   return C;
157 }
158 
159 static Cursor lexName(Cursor C, MIToken &Token, MIToken::TokenKind Type,
160                       unsigned PrefixLength, ErrorCallbackType ErrorCallback) {
161   auto Range = C;
162   C.advance(PrefixLength);
163   if (C.peek() == '"') {
164     if (Cursor R = lexStringConstant(C, ErrorCallback)) {
165       StringRef String = Range.upto(R);
166       Token.reset(Type, String)
167           .setOwnedStringValue(
168               unescapeQuotedString(String.drop_front(PrefixLength)));
169       return R;
170     }
171     Token.reset(MIToken::Error, Range.remaining());
172     return Range;
173   }
174   while (isIdentifierChar(C.peek()))
175     C.advance();
176   Token.reset(Type, Range.upto(C))
177       .setStringValue(Range.upto(C).drop_front(PrefixLength));
178   return C;
179 }
180 
181 static MIToken::TokenKind getIdentifierKind(StringRef Identifier) {
182   return StringSwitch<MIToken::TokenKind>(Identifier)
183       .Case("_", MIToken::underscore)
184       .Case("implicit", MIToken::kw_implicit)
185       .Case("implicit-def", MIToken::kw_implicit_define)
186       .Case("def", MIToken::kw_def)
187       .Case("dead", MIToken::kw_dead)
188       .Case("killed", MIToken::kw_killed)
189       .Case("undef", MIToken::kw_undef)
190       .Case("internal", MIToken::kw_internal)
191       .Case("early-clobber", MIToken::kw_early_clobber)
192       .Case("debug-use", MIToken::kw_debug_use)
193       .Case("renamable", MIToken::kw_renamable)
194       .Case("tied-def", MIToken::kw_tied_def)
195       .Case("frame-setup", MIToken::kw_frame_setup)
196       .Case("frame-destroy", MIToken::kw_frame_destroy)
197       .Case("nnan", MIToken::kw_nnan)
198       .Case("ninf", MIToken::kw_ninf)
199       .Case("nsz", MIToken::kw_nsz)
200       .Case("arcp", MIToken::kw_arcp)
201       .Case("contract", MIToken::kw_contract)
202       .Case("afn", MIToken::kw_afn)
203       .Case("reassoc", MIToken::kw_reassoc)
204       .Case("nuw" , MIToken::kw_nuw)
205       .Case("nsw" , MIToken::kw_nsw)
206       .Case("exact" , MIToken::kw_exact)
207       .Case("nofpexcept", MIToken::kw_nofpexcept)
208       .Case("debug-location", MIToken::kw_debug_location)
209       .Case("same_value", MIToken::kw_cfi_same_value)
210       .Case("offset", MIToken::kw_cfi_offset)
211       .Case("rel_offset", MIToken::kw_cfi_rel_offset)
212       .Case("def_cfa_register", MIToken::kw_cfi_def_cfa_register)
213       .Case("def_cfa_offset", MIToken::kw_cfi_def_cfa_offset)
214       .Case("adjust_cfa_offset", MIToken::kw_cfi_adjust_cfa_offset)
215       .Case("escape", MIToken::kw_cfi_escape)
216       .Case("def_cfa", MIToken::kw_cfi_def_cfa)
217       .Case("remember_state", MIToken::kw_cfi_remember_state)
218       .Case("restore", MIToken::kw_cfi_restore)
219       .Case("restore_state", MIToken::kw_cfi_restore_state)
220       .Case("undefined", MIToken::kw_cfi_undefined)
221       .Case("register", MIToken::kw_cfi_register)
222       .Case("window_save", MIToken::kw_cfi_window_save)
223       .Case("negate_ra_sign_state", MIToken::kw_cfi_aarch64_negate_ra_sign_state)
224       .Case("blockaddress", MIToken::kw_blockaddress)
225       .Case("intrinsic", MIToken::kw_intrinsic)
226       .Case("target-index", MIToken::kw_target_index)
227       .Case("half", MIToken::kw_half)
228       .Case("float", MIToken::kw_float)
229       .Case("double", MIToken::kw_double)
230       .Case("x86_fp80", MIToken::kw_x86_fp80)
231       .Case("fp128", MIToken::kw_fp128)
232       .Case("ppc_fp128", MIToken::kw_ppc_fp128)
233       .Case("target-flags", MIToken::kw_target_flags)
234       .Case("volatile", MIToken::kw_volatile)
235       .Case("non-temporal", MIToken::kw_non_temporal)
236       .Case("dereferenceable", MIToken::kw_dereferenceable)
237       .Case("invariant", MIToken::kw_invariant)
238       .Case("align", MIToken::kw_align)
239       .Case("addrspace", MIToken::kw_addrspace)
240       .Case("stack", MIToken::kw_stack)
241       .Case("got", MIToken::kw_got)
242       .Case("jump-table", MIToken::kw_jump_table)
243       .Case("constant-pool", MIToken::kw_constant_pool)
244       .Case("call-entry", MIToken::kw_call_entry)
245       .Case("custom", MIToken::kw_custom)
246       .Case("liveout", MIToken::kw_liveout)
247       .Case("address-taken", MIToken::kw_address_taken)
248       .Case("landing-pad", MIToken::kw_landing_pad)
249       .Case("liveins", MIToken::kw_liveins)
250       .Case("successors", MIToken::kw_successors)
251       .Case("floatpred", MIToken::kw_floatpred)
252       .Case("intpred", MIToken::kw_intpred)
253       .Case("shufflemask", MIToken::kw_shufflemask)
254       .Case("pre-instr-symbol", MIToken::kw_pre_instr_symbol)
255       .Case("post-instr-symbol", MIToken::kw_post_instr_symbol)
256       .Case("heap-alloc-marker", MIToken::kw_heap_alloc_marker)
257       .Case("unknown-size", MIToken::kw_unknown_size)
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 lexNamedVirtualRegister(Cursor C, MIToken &Token) {
414   Cursor Range = C;
415   C.advance(); // Skip '%'
416   while (isRegisterChar(C.peek()))
417     C.advance();
418   Token.reset(MIToken::NamedVirtualRegister, Range.upto(C))
419       .setStringValue(Range.upto(C).drop_front(1)); // Drop the '%'
420   return C;
421 }
422 
423 static Cursor maybeLexRegister(Cursor C, MIToken &Token,
424                                ErrorCallbackType ErrorCallback) {
425   if (C.peek() != '%' && C.peek() != '$')
426     return None;
427 
428   if (C.peek() == '%') {
429     if (isdigit(C.peek(1)))
430       return lexVirtualRegister(C, Token);
431 
432     if (isRegisterChar(C.peek(1)))
433       return lexNamedVirtualRegister(C, Token);
434 
435     return None;
436   }
437 
438   assert(C.peek() == '$');
439   auto Range = C;
440   C.advance(); // Skip '$'
441   while (isRegisterChar(C.peek()))
442     C.advance();
443   Token.reset(MIToken::NamedRegister, Range.upto(C))
444       .setStringValue(Range.upto(C).drop_front(1)); // Drop the '$'
445   return C;
446 }
447 
448 static Cursor maybeLexGlobalValue(Cursor C, MIToken &Token,
449                                   ErrorCallbackType ErrorCallback) {
450   if (C.peek() != '@')
451     return None;
452   if (!isdigit(C.peek(1)))
453     return lexName(C, Token, MIToken::NamedGlobalValue, /*PrefixLength=*/1,
454                    ErrorCallback);
455   auto Range = C;
456   C.advance(1); // Skip the '@'
457   auto NumberRange = C;
458   while (isdigit(C.peek()))
459     C.advance();
460   Token.reset(MIToken::GlobalValue, Range.upto(C))
461       .setIntegerValue(APSInt(NumberRange.upto(C)));
462   return C;
463 }
464 
465 static Cursor maybeLexExternalSymbol(Cursor C, MIToken &Token,
466                                      ErrorCallbackType ErrorCallback) {
467   if (C.peek() != '&')
468     return None;
469   return lexName(C, Token, MIToken::ExternalSymbol, /*PrefixLength=*/1,
470                  ErrorCallback);
471 }
472 
473 static Cursor maybeLexMCSymbol(Cursor C, MIToken &Token,
474                                ErrorCallbackType ErrorCallback) {
475   const StringRef Rule = "<mcsymbol ";
476   if (!C.remaining().startswith(Rule))
477     return None;
478   auto Start = C;
479   C.advance(Rule.size());
480 
481   // Try a simple unquoted name.
482   if (C.peek() != '"') {
483     while (isIdentifierChar(C.peek()))
484       C.advance();
485     StringRef String = Start.upto(C).drop_front(Rule.size());
486     if (C.peek() != '>') {
487       ErrorCallback(C.location(),
488                     "expected the '<mcsymbol ...' to be closed by a '>'");
489       Token.reset(MIToken::Error, Start.remaining());
490       return Start;
491     }
492     C.advance();
493 
494     Token.reset(MIToken::MCSymbol, Start.upto(C)).setStringValue(String);
495     return C;
496   }
497 
498   // Otherwise lex out a quoted name.
499   Cursor R = lexStringConstant(C, ErrorCallback);
500   if (!R) {
501     ErrorCallback(C.location(),
502                   "unable to parse quoted string from opening quote");
503     Token.reset(MIToken::Error, Start.remaining());
504     return Start;
505   }
506   StringRef String = Start.upto(R).drop_front(Rule.size());
507   if (R.peek() != '>') {
508     ErrorCallback(R.location(),
509                   "expected the '<mcsymbol ...' to be closed by a '>'");
510     Token.reset(MIToken::Error, Start.remaining());
511     return Start;
512   }
513   R.advance();
514 
515   Token.reset(MIToken::MCSymbol, Start.upto(R))
516       .setOwnedStringValue(unescapeQuotedString(String));
517   return R;
518 }
519 
520 static bool isValidHexFloatingPointPrefix(char C) {
521   return C == 'H' || C == 'K' || C == 'L' || C == 'M';
522 }
523 
524 static Cursor lexFloatingPointLiteral(Cursor Range, Cursor C, MIToken &Token) {
525   C.advance();
526   // Skip over [0-9]*([eE][-+]?[0-9]+)?
527   while (isdigit(C.peek()))
528     C.advance();
529   if ((C.peek() == 'e' || C.peek() == 'E') &&
530       (isdigit(C.peek(1)) ||
531        ((C.peek(1) == '-' || C.peek(1) == '+') && isdigit(C.peek(2))))) {
532     C.advance(2);
533     while (isdigit(C.peek()))
534       C.advance();
535   }
536   Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
537   return C;
538 }
539 
540 static Cursor maybeLexHexadecimalLiteral(Cursor C, MIToken &Token) {
541   if (C.peek() != '0' || (C.peek(1) != 'x' && C.peek(1) != 'X'))
542     return None;
543   Cursor Range = C;
544   C.advance(2);
545   unsigned PrefLen = 2;
546   if (isValidHexFloatingPointPrefix(C.peek())) {
547     C.advance();
548     PrefLen++;
549   }
550   while (isxdigit(C.peek()))
551     C.advance();
552   StringRef StrVal = Range.upto(C);
553   if (StrVal.size() <= PrefLen)
554     return None;
555   if (PrefLen == 2)
556     Token.reset(MIToken::HexLiteral, Range.upto(C));
557   else // It must be 3, which means that there was a floating-point prefix.
558     Token.reset(MIToken::FloatingPointLiteral, Range.upto(C));
559   return C;
560 }
561 
562 static Cursor maybeLexNumericalLiteral(Cursor C, MIToken &Token) {
563   if (!isdigit(C.peek()) && (C.peek() != '-' || !isdigit(C.peek(1))))
564     return None;
565   auto Range = C;
566   C.advance();
567   while (isdigit(C.peek()))
568     C.advance();
569   if (C.peek() == '.')
570     return lexFloatingPointLiteral(Range, C, Token);
571   StringRef StrVal = Range.upto(C);
572   Token.reset(MIToken::IntegerLiteral, StrVal).setIntegerValue(APSInt(StrVal));
573   return C;
574 }
575 
576 static MIToken::TokenKind getMetadataKeywordKind(StringRef Identifier) {
577   return StringSwitch<MIToken::TokenKind>(Identifier)
578       .Case("!tbaa", MIToken::md_tbaa)
579       .Case("!alias.scope", MIToken::md_alias_scope)
580       .Case("!noalias", MIToken::md_noalias)
581       .Case("!range", MIToken::md_range)
582       .Case("!DIExpression", MIToken::md_diexpr)
583       .Case("!DILocation", MIToken::md_dilocation)
584       .Default(MIToken::Error);
585 }
586 
587 static Cursor maybeLexExclaim(Cursor C, MIToken &Token,
588                               ErrorCallbackType ErrorCallback) {
589   if (C.peek() != '!')
590     return None;
591   auto Range = C;
592   C.advance(1);
593   if (isdigit(C.peek()) || !isIdentifierChar(C.peek())) {
594     Token.reset(MIToken::exclaim, Range.upto(C));
595     return C;
596   }
597   while (isIdentifierChar(C.peek()))
598     C.advance();
599   StringRef StrVal = Range.upto(C);
600   Token.reset(getMetadataKeywordKind(StrVal), StrVal);
601   if (Token.isError())
602     ErrorCallback(Token.location(),
603                   "use of unknown metadata keyword '" + StrVal + "'");
604   return C;
605 }
606 
607 static MIToken::TokenKind symbolToken(char C) {
608   switch (C) {
609   case ',':
610     return MIToken::comma;
611   case '.':
612     return MIToken::dot;
613   case '=':
614     return MIToken::equal;
615   case ':':
616     return MIToken::colon;
617   case '(':
618     return MIToken::lparen;
619   case ')':
620     return MIToken::rparen;
621   case '{':
622     return MIToken::lbrace;
623   case '}':
624     return MIToken::rbrace;
625   case '+':
626     return MIToken::plus;
627   case '-':
628     return MIToken::minus;
629   case '<':
630     return MIToken::less;
631   case '>':
632     return MIToken::greater;
633   default:
634     return MIToken::Error;
635   }
636 }
637 
638 static Cursor maybeLexSymbol(Cursor C, MIToken &Token) {
639   MIToken::TokenKind Kind;
640   unsigned Length = 1;
641   if (C.peek() == ':' && C.peek(1) == ':') {
642     Kind = MIToken::coloncolon;
643     Length = 2;
644   } else
645     Kind = symbolToken(C.peek());
646   if (Kind == MIToken::Error)
647     return None;
648   auto Range = C;
649   C.advance(Length);
650   Token.reset(Kind, Range.upto(C));
651   return C;
652 }
653 
654 static Cursor maybeLexNewline(Cursor C, MIToken &Token) {
655   if (!isNewlineChar(C.peek()))
656     return None;
657   auto Range = C;
658   C.advance();
659   Token.reset(MIToken::Newline, Range.upto(C));
660   return C;
661 }
662 
663 static Cursor maybeLexEscapedIRValue(Cursor C, MIToken &Token,
664                                      ErrorCallbackType ErrorCallback) {
665   if (C.peek() != '`')
666     return None;
667   auto Range = C;
668   C.advance();
669   auto StrRange = C;
670   while (C.peek() != '`') {
671     if (C.isEOF() || isNewlineChar(C.peek())) {
672       ErrorCallback(
673           C.location(),
674           "end of machine instruction reached before the closing '`'");
675       Token.reset(MIToken::Error, Range.remaining());
676       return C;
677     }
678     C.advance();
679   }
680   StringRef Value = StrRange.upto(C);
681   C.advance();
682   Token.reset(MIToken::QuotedIRValue, Range.upto(C)).setStringValue(Value);
683   return C;
684 }
685 
686 StringRef llvm::lexMIToken(StringRef Source, MIToken &Token,
687                            ErrorCallbackType ErrorCallback) {
688   auto C = skipComment(skipWhitespace(Cursor(Source)));
689   if (C.isEOF()) {
690     Token.reset(MIToken::Eof, C.remaining());
691     return C.remaining();
692   }
693 
694   if (Cursor R = maybeLexMachineBasicBlock(C, Token, ErrorCallback))
695     return R.remaining();
696   if (Cursor R = maybeLexIdentifier(C, Token))
697     return R.remaining();
698   if (Cursor R = maybeLexJumpTableIndex(C, Token))
699     return R.remaining();
700   if (Cursor R = maybeLexStackObject(C, Token))
701     return R.remaining();
702   if (Cursor R = maybeLexFixedStackObject(C, Token))
703     return R.remaining();
704   if (Cursor R = maybeLexConstantPoolItem(C, Token))
705     return R.remaining();
706   if (Cursor R = maybeLexSubRegisterIndex(C, Token, ErrorCallback))
707     return R.remaining();
708   if (Cursor R = maybeLexIRBlock(C, Token, ErrorCallback))
709     return R.remaining();
710   if (Cursor R = maybeLexIRValue(C, Token, ErrorCallback))
711     return R.remaining();
712   if (Cursor R = maybeLexRegister(C, Token, ErrorCallback))
713     return R.remaining();
714   if (Cursor R = maybeLexGlobalValue(C, Token, ErrorCallback))
715     return R.remaining();
716   if (Cursor R = maybeLexExternalSymbol(C, Token, ErrorCallback))
717     return R.remaining();
718   if (Cursor R = maybeLexMCSymbol(C, Token, ErrorCallback))
719     return R.remaining();
720   if (Cursor R = maybeLexHexadecimalLiteral(C, Token))
721     return R.remaining();
722   if (Cursor R = maybeLexNumericalLiteral(C, Token))
723     return R.remaining();
724   if (Cursor R = maybeLexExclaim(C, Token, ErrorCallback))
725     return R.remaining();
726   if (Cursor R = maybeLexSymbol(C, Token))
727     return R.remaining();
728   if (Cursor R = maybeLexNewline(C, Token))
729     return R.remaining();
730   if (Cursor R = maybeLexEscapedIRValue(C, Token, ErrorCallback))
731     return R.remaining();
732   if (Cursor R = maybeLexStringConstant(C, Token, ErrorCallback))
733     return R.remaining();
734 
735   Token.reset(MIToken::Error, C.remaining());
736   ErrorCallback(C.location(),
737                 Twine("unexpected character '") + Twine(C.peek()) + "'");
738   return C.remaining();
739 }
740