aboutsummaryrefslogtreecommitdiffstats
path: root/contrib/libs/llvm12/lib/CodeGen/AsmPrinter/AsmPrinterInlineAsm.cpp
blob: 4a67b0bc2c4d408ce1f7ca65aabdf1740ae4a535 (plain) (blame)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
255
256
257
258
259
260
261
262
263
264
265
266
267
268
269
270
271
272
273
274
275
276
277
278
279
280
281
282
283
284
285
286
287
288
289
290
291
292
293
294
295
296
297
298
299
300
301
302
303
304
305
306
307
308
309
310
311
312
313
314
315
316
317
318
319
320
321
322
323
324
325
326
327
328
329
330
331
332
333
334
335
336
337
338
339
340
341
342
343
344
345
346
347
348
349
350
351
352
353
354
355
356
357
358
359
360
361
362
363
364
365
366
367
368
369
370
371
372
373
374
375
376
377
378
379
380
381
382
383
384
385
386
387
388
389
390
391
392
393
394
395
396
397
398
399
400
401
402
403
404
405
406
407
408
409
410
411
412
413
414
415
416
417
418
419
420
421
422
423
424
425
426
427
428
429
430
431
432
433
434
435
436
437
438
439
440
441
442
443
444
445
446
447
448
449
450
451
452
453
454
455
456
457
458
459
460
461
462
463
464
465
466
467
468
469
470
471
472
473
474
475
476
477
478
479
480
481
482
483
484
485
486
487
488
489
490
491
492
493
494
495
496
497
498
499
500
501
502
503
504
505
506
507
508
509
510
511
512
513
514
515
516
517
518
519
520
521
522
523
524
525
526
527
528
529
530
531
532
533
534
535
536
537
538
539
540
541
542
543
544
545
546
547
548
549
550
551
552
553
554
555
556
557
558
559
560
561
562
563
564
565
566
567
568
569
570
571
572
573
574
575
576
577
578
579
580
581
582
583
584
585
586
587
588
589
590
591
592
593
594
595
596
597
598
599
600
601
602
603
604
605
606
607
608
609
610
611
612
613
614
615
616
617
618
619
620
621
622
623
624
625
626
627
628
629
630
631
632
633
634
635
636
637
638
639
640
641
642
643
644
645
646
647
648
649
650
651
652
653
654
655
656
657
658
659
660
661
662
663
664
665
666
667
668
669
670
671
672
673
674
675
676
677
678
679
680
681
682
683
684
685
686
687
688
689
690
691
692
693
694
695
//===-- AsmPrinterInlineAsm.cpp - AsmPrinter Inline Asm Handling ----------===//
//
// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
// See https://llvm.org/LICENSE.txt for license information.
// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
//
//===----------------------------------------------------------------------===//
//
// This file implements the inline assembler pieces of the AsmPrinter class.
//
//===----------------------------------------------------------------------===//

#include "llvm/ADT/SmallString.h"
#include "llvm/ADT/SmallVector.h"
#include "llvm/ADT/Twine.h"
#include "llvm/CodeGen/AsmPrinter.h"
#include "llvm/CodeGen/MachineBasicBlock.h"
#include "llvm/CodeGen/MachineFunction.h"
#include "llvm/CodeGen/MachineModuleInfo.h"
#include "llvm/CodeGen/TargetInstrInfo.h"
#include "llvm/CodeGen/TargetRegisterInfo.h"
#include "llvm/IR/Constants.h"
#include "llvm/IR/DataLayout.h"
#include "llvm/IR/InlineAsm.h"
#include "llvm/IR/LLVMContext.h"
#include "llvm/IR/Module.h"
#include "llvm/MC/MCAsmInfo.h"
#include "llvm/MC/MCParser/MCTargetAsmParser.h"
#include "llvm/MC/MCStreamer.h"
#include "llvm/MC/MCSubtargetInfo.h"
#include "llvm/MC/MCSymbol.h"
#include "llvm/Support/ErrorHandling.h"
#include "llvm/Support/MemoryBuffer.h"
#include "llvm/Support/SourceMgr.h"
#include "llvm/Support/TargetRegistry.h"
#include "llvm/Support/raw_ostream.h"
#include "llvm/Target/TargetMachine.h"
using namespace llvm;

#define DEBUG_TYPE "asm-printer"

/// srcMgrDiagHandler - This callback is invoked when the SourceMgr for an
/// inline asm has an error in it.  diagInfo is a pointer to the SrcMgrDiagInfo
/// struct above.
static void srcMgrDiagHandler(const SMDiagnostic &Diag, void *diagInfo) {
  AsmPrinter::SrcMgrDiagInfo *DiagInfo =
      static_cast<AsmPrinter::SrcMgrDiagInfo *>(diagInfo);
  assert(DiagInfo && "Diagnostic context not passed down?");

  // Look up a LocInfo for the buffer this diagnostic is coming from.
  unsigned BufNum = DiagInfo->SrcMgr.FindBufferContainingLoc(Diag.getLoc());
  const MDNode *LocInfo = nullptr;
  if (BufNum > 0 && BufNum <= DiagInfo->LocInfos.size())
    LocInfo = DiagInfo->LocInfos[BufNum-1];

  // If the inline asm had metadata associated with it, pull out a location
  // cookie corresponding to which line the error occurred on.
  unsigned LocCookie = 0;
  if (LocInfo) {
    unsigned ErrorLine = Diag.getLineNo()-1;
    if (ErrorLine >= LocInfo->getNumOperands())
      ErrorLine = 0;

    if (LocInfo->getNumOperands() != 0)
      if (const ConstantInt *CI =
              mdconst::dyn_extract<ConstantInt>(LocInfo->getOperand(ErrorLine)))
        LocCookie = CI->getZExtValue();
  }

  DiagInfo->DiagHandler(Diag, DiagInfo->DiagContext, LocCookie);
}

unsigned AsmPrinter::addInlineAsmDiagBuffer(StringRef AsmStr,
                                            const MDNode *LocMDNode) const {
  if (!DiagInfo) {
    DiagInfo = std::make_unique<SrcMgrDiagInfo>();

    MCContext &Context = MMI->getContext();
    Context.setInlineSourceManager(&DiagInfo->SrcMgr);

    LLVMContext &LLVMCtx = MMI->getModule()->getContext();
    if (LLVMCtx.getInlineAsmDiagnosticHandler()) {
      DiagInfo->DiagHandler = LLVMCtx.getInlineAsmDiagnosticHandler();
      DiagInfo->DiagContext = LLVMCtx.getInlineAsmDiagnosticContext();
      DiagInfo->SrcMgr.setDiagHandler(srcMgrDiagHandler, DiagInfo.get());
    }
  }

  SourceMgr &SrcMgr = DiagInfo->SrcMgr;

  std::unique_ptr<MemoryBuffer> Buffer;
  // The inline asm source manager will outlive AsmStr, so make a copy of the
  // string for SourceMgr to own.
  Buffer = MemoryBuffer::getMemBufferCopy(AsmStr, "<inline asm>");

  // Tell SrcMgr about this buffer, it takes ownership of the buffer.
  unsigned BufNum = SrcMgr.AddNewSourceBuffer(std::move(Buffer), SMLoc());

  // Store LocMDNode in DiagInfo, using BufNum as an identifier.
  if (LocMDNode) {
    DiagInfo->LocInfos.resize(BufNum);
    DiagInfo->LocInfos[BufNum - 1] = LocMDNode;
  }

  return BufNum;
}


/// EmitInlineAsm - Emit a blob of inline asm to the output streamer.
void AsmPrinter::emitInlineAsm(StringRef Str, const MCSubtargetInfo &STI,
                               const MCTargetOptions &MCOptions,
                               const MDNode *LocMDNode,
                               InlineAsm::AsmDialect Dialect) const {
  assert(!Str.empty() && "Can't emit empty inline asm block");

  // Remember if the buffer is nul terminated or not so we can avoid a copy.
  bool isNullTerminated = Str.back() == 0;
  if (isNullTerminated)
    Str = Str.substr(0, Str.size()-1);

  // If the output streamer does not have mature MC support or the integrated
  // assembler has been disabled, just emit the blob textually.
  // Otherwise parse the asm and emit it via MC support.
  // This is useful in case the asm parser doesn't handle something but the
  // system assembler does.
  const MCAsmInfo *MCAI = TM.getMCAsmInfo();
  assert(MCAI && "No MCAsmInfo");
  if (!MCAI->useIntegratedAssembler() &&
      !OutStreamer->isIntegratedAssemblerRequired()) {
    emitInlineAsmStart();
    OutStreamer->emitRawText(Str);
    emitInlineAsmEnd(STI, nullptr);
    return;
  }

  unsigned BufNum = addInlineAsmDiagBuffer(Str, LocMDNode);
  DiagInfo->SrcMgr.setIncludeDirs(MCOptions.IASSearchPaths);

  std::unique_ptr<MCAsmParser> Parser(createMCAsmParser(
          DiagInfo->SrcMgr, OutContext, *OutStreamer, *MAI, BufNum));

  // Do not use assembler-level information for parsing inline assembly.
  OutStreamer->setUseAssemblerInfoForParsing(false);

  // We create a new MCInstrInfo here since we might be at the module level
  // and not have a MachineFunction to initialize the TargetInstrInfo from and
  // we only need MCInstrInfo for asm parsing. We create one unconditionally
  // because it's not subtarget dependent.
  std::unique_ptr<MCInstrInfo> MII(TM.getTarget().createMCInstrInfo());
  assert(MII && "Failed to create instruction info");
  std::unique_ptr<MCTargetAsmParser> TAP(TM.getTarget().createMCAsmParser(
      STI, *Parser, *MII, MCOptions));
  if (!TAP)
    report_fatal_error("Inline asm not supported by this streamer because"
                       " we don't have an asm parser for this target\n");
  Parser->setAssemblerDialect(Dialect);
  Parser->setTargetParser(*TAP.get());
  // Enable lexing Masm binary and hex integer literals in intel inline
  // assembly.
  if (Dialect == InlineAsm::AD_Intel)
    Parser->getLexer().setLexMasmIntegers(true);

  emitInlineAsmStart();
  // Don't implicitly switch to the text section before the asm.
  int Res = Parser->Run(/*NoInitialTextSection*/ true,
                        /*NoFinalize*/ true);
  emitInlineAsmEnd(STI, &TAP->getSTI());

  if (Res && !DiagInfo->DiagHandler)
    report_fatal_error("Error parsing inline asm\n");
}

static void EmitMSInlineAsmStr(const char *AsmStr, const MachineInstr *MI,
                               MachineModuleInfo *MMI, AsmPrinter *AP,
                               unsigned LocCookie, raw_ostream &OS) {
  // Switch to the inline assembly variant.
  OS << "\t.intel_syntax\n\t";

  const char *LastEmitted = AsmStr; // One past the last character emitted.
  unsigned NumOperands = MI->getNumOperands();

  while (*LastEmitted) {
    switch (*LastEmitted) {
    default: {
      // Not a special case, emit the string section literally.
      const char *LiteralEnd = LastEmitted+1;
      while (*LiteralEnd && *LiteralEnd != '{' && *LiteralEnd != '|' &&
             *LiteralEnd != '}' && *LiteralEnd != '$' && *LiteralEnd != '\n')
        ++LiteralEnd;

      OS.write(LastEmitted, LiteralEnd-LastEmitted);
      LastEmitted = LiteralEnd;
      break;
    }
    case '\n':
      ++LastEmitted;   // Consume newline character.
      OS << '\n';      // Indent code with newline.
      break;
    case '$': {
      ++LastEmitted;   // Consume '$' character.
      bool Done = true;

      // Handle escapes.
      switch (*LastEmitted) {
      default: Done = false; break;
      case '$':
        ++LastEmitted;  // Consume second '$' character.
        break;
      }
      if (Done) break;

      bool HasCurlyBraces = false;
      if (*LastEmitted == '{') {     // ${variable}
        ++LastEmitted;               // Consume '{' character.
        HasCurlyBraces = true;
      }

      // If we have ${:foo}, then this is not a real operand reference, it is a
      // "magic" string reference, just like in .td files.  Arrange to call
      // PrintSpecial.
      if (HasCurlyBraces && LastEmitted[0] == ':') {
        ++LastEmitted;
        const char *StrStart = LastEmitted;
        const char *StrEnd = strchr(StrStart, '}');
        if (!StrEnd)
          report_fatal_error("Unterminated ${:foo} operand in inline asm"
                             " string: '" + Twine(AsmStr) + "'");

        std::string Val(StrStart, StrEnd);
        AP->PrintSpecial(MI, OS, Val.c_str());
        LastEmitted = StrEnd+1;
        break;
      }

      const char *IDStart = LastEmitted;
      const char *IDEnd = IDStart;
      while (isDigit(*IDEnd))
        ++IDEnd;

      unsigned Val;
      if (StringRef(IDStart, IDEnd-IDStart).getAsInteger(10, Val))
        report_fatal_error("Bad $ operand number in inline asm string: '" +
                           Twine(AsmStr) + "'");
      LastEmitted = IDEnd;

      if (Val >= NumOperands-1)
        report_fatal_error("Invalid $ operand number in inline asm string: '" +
                           Twine(AsmStr) + "'");

      char Modifier[2] = { 0, 0 };

      if (HasCurlyBraces) {
        // If we have curly braces, check for a modifier character.  This
        // supports syntax like ${0:u}, which correspond to "%u0" in GCC asm.
        if (*LastEmitted == ':') {
          ++LastEmitted;    // Consume ':' character.
          if (*LastEmitted == 0)
            report_fatal_error("Bad ${:} expression in inline asm string: '" +
                               Twine(AsmStr) + "'");

          Modifier[0] = *LastEmitted;
          ++LastEmitted;    // Consume modifier character.
        }

        if (*LastEmitted != '}')
          report_fatal_error("Bad ${} expression in inline asm string: '" +
                             Twine(AsmStr) + "'");
        ++LastEmitted;    // Consume '}' character.
      }

      // Okay, we finally have a value number.  Ask the target to print this
      // operand!
      unsigned OpNo = InlineAsm::MIOp_FirstOperand;

      bool Error = false;

      // Scan to find the machine operand number for the operand.
      for (; Val; --Val) {
        if (OpNo >= MI->getNumOperands()) break;
        unsigned OpFlags = MI->getOperand(OpNo).getImm();
        OpNo += InlineAsm::getNumOperandRegisters(OpFlags) + 1;
      }

      // We may have a location metadata attached to the end of the
      // instruction, and at no point should see metadata at any
      // other point while processing. It's an error if so.
      if (OpNo >= MI->getNumOperands() ||
          MI->getOperand(OpNo).isMetadata()) {
        Error = true;
      } else {
        unsigned OpFlags = MI->getOperand(OpNo).getImm();
        ++OpNo;  // Skip over the ID number.

        if (InlineAsm::isMemKind(OpFlags)) {
          Error = AP->PrintAsmMemoryOperand(
              MI, OpNo, Modifier[0] ? Modifier : nullptr, OS);
        } else {
          Error = AP->PrintAsmOperand(MI, OpNo,
                                      Modifier[0] ? Modifier : nullptr, OS);
        }
      }
      if (Error) {
        std::string msg;
        raw_string_ostream Msg(msg);
        Msg << "invalid operand in inline asm: '" << AsmStr << "'";
        MMI->getModule()->getContext().emitError(LocCookie, Msg.str());
      }
      break;
    }
    }
  }
  OS << "\n\t.att_syntax\n" << (char)0;  // null terminate string.
}

static void EmitGCCInlineAsmStr(const char *AsmStr, const MachineInstr *MI,
                                MachineModuleInfo *MMI, int AsmPrinterVariant,
                                AsmPrinter *AP, unsigned LocCookie,
                                raw_ostream &OS) {
  int CurVariant = -1;            // The number of the {.|.|.} region we are in.
  const char *LastEmitted = AsmStr; // One past the last character emitted.
  unsigned NumOperands = MI->getNumOperands();

  OS << '\t';

  while (*LastEmitted) {
    switch (*LastEmitted) {
    default: {
      // Not a special case, emit the string section literally.
      const char *LiteralEnd = LastEmitted+1;
      while (*LiteralEnd && *LiteralEnd != '{' && *LiteralEnd != '|' &&
             *LiteralEnd != '}' && *LiteralEnd != '$' && *LiteralEnd != '\n')
        ++LiteralEnd;
      if (CurVariant == -1 || CurVariant == AsmPrinterVariant)
        OS.write(LastEmitted, LiteralEnd-LastEmitted);
      LastEmitted = LiteralEnd;
      break;
    }
    case '\n':
      ++LastEmitted;   // Consume newline character.
      OS << '\n';      // Indent code with newline.
      break;
    case '$': {
      ++LastEmitted;   // Consume '$' character.
      bool Done = true;

      // Handle escapes.
      switch (*LastEmitted) {
      default: Done = false; break;
      case '$':     // $$ -> $
        if (CurVariant == -1 || CurVariant == AsmPrinterVariant)
          OS << '$';
        ++LastEmitted;  // Consume second '$' character.
        break;
      case '(':             // $( -> same as GCC's { character.
        ++LastEmitted;      // Consume '(' character.
        if (CurVariant != -1)
          report_fatal_error("Nested variants found in inline asm string: '" +
                             Twine(AsmStr) + "'");
        CurVariant = 0;     // We're in the first variant now.
        break;
      case '|':
        ++LastEmitted;  // consume '|' character.
        if (CurVariant == -1)
          OS << '|';       // this is gcc's behavior for | outside a variant
        else
          ++CurVariant;   // We're in the next variant.
        break;
      case ')':         // $) -> same as GCC's } char.
        ++LastEmitted;  // consume ')' character.
        if (CurVariant == -1)
          OS << '}';     // this is gcc's behavior for } outside a variant
        else
          CurVariant = -1;
        break;
      }
      if (Done) break;

      bool HasCurlyBraces = false;
      if (*LastEmitted == '{') {     // ${variable}
        ++LastEmitted;               // Consume '{' character.
        HasCurlyBraces = true;
      }

      // If we have ${:foo}, then this is not a real operand reference, it is a
      // "magic" string reference, just like in .td files.  Arrange to call
      // PrintSpecial.
      if (HasCurlyBraces && *LastEmitted == ':') {
        ++LastEmitted;
        const char *StrStart = LastEmitted;
        const char *StrEnd = strchr(StrStart, '}');
        if (!StrEnd)
          report_fatal_error("Unterminated ${:foo} operand in inline asm"
                             " string: '" + Twine(AsmStr) + "'");

        std::string Val(StrStart, StrEnd);
        AP->PrintSpecial(MI, OS, Val.c_str());
        LastEmitted = StrEnd+1;
        break;
      }

      const char *IDStart = LastEmitted;
      const char *IDEnd = IDStart;
      while (isDigit(*IDEnd))
        ++IDEnd;

      unsigned Val;
      if (StringRef(IDStart, IDEnd-IDStart).getAsInteger(10, Val))
        report_fatal_error("Bad $ operand number in inline asm string: '" +
                           Twine(AsmStr) + "'");
      LastEmitted = IDEnd;

      char Modifier[2] = { 0, 0 };

      if (HasCurlyBraces) {
        // If we have curly braces, check for a modifier character.  This
        // supports syntax like ${0:u}, which correspond to "%u0" in GCC asm.
        if (*LastEmitted == ':') {
          ++LastEmitted;    // Consume ':' character.
          if (*LastEmitted == 0)
            report_fatal_error("Bad ${:} expression in inline asm string: '" +
                               Twine(AsmStr) + "'");

          Modifier[0] = *LastEmitted;
          ++LastEmitted;    // Consume modifier character.
        }

        if (*LastEmitted != '}')
          report_fatal_error("Bad ${} expression in inline asm string: '" +
                             Twine(AsmStr) + "'");
        ++LastEmitted;    // Consume '}' character.
      }

      if (Val >= NumOperands-1)
        report_fatal_error("Invalid $ operand number in inline asm string: '" +
                           Twine(AsmStr) + "'");

      // Okay, we finally have a value number.  Ask the target to print this
      // operand!
      if (CurVariant == -1 || CurVariant == AsmPrinterVariant) {
        unsigned OpNo = InlineAsm::MIOp_FirstOperand;

        bool Error = false;

        // Scan to find the machine operand number for the operand.
        for (; Val; --Val) {
          if (OpNo >= MI->getNumOperands()) break;
          unsigned OpFlags = MI->getOperand(OpNo).getImm();
          OpNo += InlineAsm::getNumOperandRegisters(OpFlags) + 1;
        }

        // We may have a location metadata attached to the end of the
        // instruction, and at no point should see metadata at any
        // other point while processing. It's an error if so.
        if (OpNo >= MI->getNumOperands() ||
            MI->getOperand(OpNo).isMetadata()) {
          Error = true;
        } else {
          unsigned OpFlags = MI->getOperand(OpNo).getImm();
          ++OpNo;  // Skip over the ID number.

          // FIXME: Shouldn't arch-independent output template handling go into
          // PrintAsmOperand?
          // Labels are target independent.
          if (MI->getOperand(OpNo).isBlockAddress()) {
            const BlockAddress *BA = MI->getOperand(OpNo).getBlockAddress();
            MCSymbol *Sym = AP->GetBlockAddressSymbol(BA);
            Sym->print(OS, AP->MAI);
            MMI->getContext().registerInlineAsmLabel(Sym);
          } else if (MI->getOperand(OpNo).isMBB()) {
            const MCSymbol *Sym = MI->getOperand(OpNo).getMBB()->getSymbol();
            Sym->print(OS, AP->MAI);
          } else if (Modifier[0] == 'l') {
            Error = true;
          } else if (InlineAsm::isMemKind(OpFlags)) {
            Error = AP->PrintAsmMemoryOperand(
                MI, OpNo, Modifier[0] ? Modifier : nullptr, OS);
          } else {
            Error = AP->PrintAsmOperand(MI, OpNo,
                                        Modifier[0] ? Modifier : nullptr, OS);
          }
        }
        if (Error) {
          std::string msg;
          raw_string_ostream Msg(msg);
          Msg << "invalid operand in inline asm: '" << AsmStr << "'";
          MMI->getModule()->getContext().emitError(LocCookie, Msg.str());
        }
      }
      break;
    }
    }
  }
  OS << '\n' << (char)0;  // null terminate string.
}

/// This method formats and emits the specified machine instruction that is an
/// inline asm.
void AsmPrinter::emitInlineAsm(const MachineInstr *MI) const {
  assert(MI->isInlineAsm() && "printInlineAsm only works on inline asms");

  // Count the number of register definitions to find the asm string.
  unsigned NumDefs = 0;
  for (; MI->getOperand(NumDefs).isReg() && MI->getOperand(NumDefs).isDef();
       ++NumDefs)
    assert(NumDefs != MI->getNumOperands()-2 && "No asm string?");

  assert(MI->getOperand(NumDefs).isSymbol() && "No asm string?");

  // Disassemble the AsmStr, printing out the literal pieces, the operands, etc.
  const char *AsmStr = MI->getOperand(NumDefs).getSymbolName();

  // If this asmstr is empty, just print the #APP/#NOAPP markers.
  // These are useful to see where empty asm's wound up.
  if (AsmStr[0] == 0) {
    OutStreamer->emitRawComment(MAI->getInlineAsmStart());
    OutStreamer->emitRawComment(MAI->getInlineAsmEnd());
    return;
  }

  // Emit the #APP start marker.  This has to happen even if verbose-asm isn't
  // enabled, so we use emitRawComment.
  OutStreamer->emitRawComment(MAI->getInlineAsmStart());

  // Get the !srcloc metadata node if we have it, and decode the loc cookie from
  // it.
  unsigned LocCookie = 0;
  const MDNode *LocMD = nullptr;
  for (unsigned i = MI->getNumOperands(); i != 0; --i) {
    if (MI->getOperand(i-1).isMetadata() &&
        (LocMD = MI->getOperand(i-1).getMetadata()) &&
        LocMD->getNumOperands() != 0) {
      if (const ConstantInt *CI =
              mdconst::dyn_extract<ConstantInt>(LocMD->getOperand(0))) {
        LocCookie = CI->getZExtValue();
        break;
      }
    }
  }

  // Emit the inline asm to a temporary string so we can emit it through
  // EmitInlineAsm.
  SmallString<256> StringData;
  raw_svector_ostream OS(StringData);

  // The variant of the current asmprinter.
  int AsmPrinterVariant = MAI->getAssemblerDialect();
  AsmPrinter *AP = const_cast<AsmPrinter*>(this);
  if (MI->getInlineAsmDialect() == InlineAsm::AD_ATT)
    EmitGCCInlineAsmStr(AsmStr, MI, MMI, AsmPrinterVariant, AP, LocCookie, OS);
  else
    EmitMSInlineAsmStr(AsmStr, MI, MMI, AP, LocCookie, OS);

  // Emit warnings if we use reserved registers on the clobber list, as
  // that might lead to undefined behaviour.
  SmallVector<Register, 8> RestrRegs;
  const TargetRegisterInfo *TRI = MF->getSubtarget().getRegisterInfo();
  // Start with the first operand descriptor, and iterate over them.
  for (unsigned I = InlineAsm::MIOp_FirstOperand, NumOps = MI->getNumOperands();
       I < NumOps; ++I) {
    const MachineOperand &MO = MI->getOperand(I);
    if (!MO.isImm())
      continue;
    unsigned Flags = MO.getImm();
    if (InlineAsm::getKind(Flags) == InlineAsm::Kind_Clobber) {
      Register Reg = MI->getOperand(I + 1).getReg();
      if (!TRI->isAsmClobberable(*MF, Reg))
        RestrRegs.push_back(Reg);
    }
    // Skip to one before the next operand descriptor, if it exists.
    I += InlineAsm::getNumOperandRegisters(Flags);
  }

  if (!RestrRegs.empty()) {
    unsigned BufNum = addInlineAsmDiagBuffer(OS.str(), LocMD);
    auto &SrcMgr = DiagInfo->SrcMgr;
    SMLoc Loc = SMLoc::getFromPointer(
        SrcMgr.getMemoryBuffer(BufNum)->getBuffer().begin());

    std::string Msg = "inline asm clobber list contains reserved registers: ";
    for (auto I = RestrRegs.begin(), E = RestrRegs.end(); I != E; ++I) {
      if(I != RestrRegs.begin())
        Msg += ", ";
      Msg += TRI->getName(*I);
    }
    const char *Note =
        "Reserved registers on the clobber list may not be "
        "preserved across the asm statement, and clobbering them may "
        "lead to undefined behaviour.";
    SrcMgr.PrintMessage(Loc, SourceMgr::DK_Warning, Msg);
    SrcMgr.PrintMessage(Loc, SourceMgr::DK_Note, Note);
  }

  emitInlineAsm(OS.str(), getSubtargetInfo(), TM.Options.MCOptions, LocMD,
                MI->getInlineAsmDialect());

  // Emit the #NOAPP end marker.  This has to happen even if verbose-asm isn't
  // enabled, so we use emitRawComment.
  OutStreamer->emitRawComment(MAI->getInlineAsmEnd());
}

/// PrintSpecial - Print information related to the specified machine instr
/// that is independent of the operand, and may be independent of the instr
/// itself.  This can be useful for portably encoding the comment character
/// or other bits of target-specific knowledge into the asmstrings.  The
/// syntax used is ${:comment}.  Targets can override this to add support
/// for their own strange codes.
void AsmPrinter::PrintSpecial(const MachineInstr *MI, raw_ostream &OS,
                              const char *Code) const {
  if (!strcmp(Code, "private")) {
    const DataLayout &DL = MF->getDataLayout();
    OS << DL.getPrivateGlobalPrefix();
  } else if (!strcmp(Code, "comment")) {
    OS << MAI->getCommentString();
  } else if (!strcmp(Code, "uid")) {
    // Comparing the address of MI isn't sufficient, because machineinstrs may
    // be allocated to the same address across functions.

    // If this is a new LastFn instruction, bump the counter.
    if (LastMI != MI || LastFn != getFunctionNumber()) {
      ++Counter;
      LastMI = MI;
      LastFn = getFunctionNumber();
    }
    OS << Counter;
  } else {
    std::string msg;
    raw_string_ostream Msg(msg);
    Msg << "Unknown special formatter '" << Code
         << "' for machine instr: " << *MI;
    report_fatal_error(Msg.str());
  }
}

void AsmPrinter::PrintSymbolOperand(const MachineOperand &MO, raw_ostream &OS) {
  assert(MO.isGlobal() && "caller should check MO.isGlobal");
  getSymbol(MO.getGlobal())->print(OS, MAI);
  printOffset(MO.getOffset(), OS);
}

/// PrintAsmOperand - Print the specified operand of MI, an INLINEASM
/// instruction, using the specified assembler variant.  Targets should
/// override this to format as appropriate for machine specific ExtraCodes
/// or when the arch-independent handling would be too complex otherwise.
bool AsmPrinter::PrintAsmOperand(const MachineInstr *MI, unsigned OpNo,
                                 const char *ExtraCode, raw_ostream &O) {
  // Does this asm operand have a single letter operand modifier?
  if (ExtraCode && ExtraCode[0]) {
    if (ExtraCode[1] != 0) return true; // Unknown modifier.

    // https://gcc.gnu.org/onlinedocs/gccint/Output-Template.html
    const MachineOperand &MO = MI->getOperand(OpNo);
    switch (ExtraCode[0]) {
    default:
      return true;  // Unknown modifier.
    case 'a': // Print as memory address.
      if (MO.isReg()) {
        PrintAsmMemoryOperand(MI, OpNo, nullptr, O);
        return false;
      }
      LLVM_FALLTHROUGH; // GCC allows '%a' to behave like '%c' with immediates.
    case 'c': // Substitute immediate value without immediate syntax
      if (MO.isImm()) {
        O << MO.getImm();
        return false;
      }
      if (MO.isGlobal()) {
        PrintSymbolOperand(MO, O);
        return false;
      }
      return true;
    case 'n':  // Negate the immediate constant.
      if (!MO.isImm())
        return true;
      O << -MO.getImm();
      return false;
    case 's':  // The GCC deprecated s modifier
      if (!MO.isImm())
        return true;
      O << ((32 - MO.getImm()) & 31);
      return false;
    }
  }
  return true;
}

bool AsmPrinter::PrintAsmMemoryOperand(const MachineInstr *MI, unsigned OpNo,
                                       const char *ExtraCode, raw_ostream &O) {
  // Target doesn't support this yet!
  return true;
}

void AsmPrinter::emitInlineAsmStart() const {}

void AsmPrinter::emitInlineAsmEnd(const MCSubtargetInfo &StartInfo,
                                  const MCSubtargetInfo *EndInfo) const {}