SemaStmtAsm.cpp revision b706d9027cd8bbbaffa8b359a501cba52ace4c09 
1//===--- SemaStmtAsm.cpp - Semantic Analysis for Asm Statements -----------===//
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 semantic analysis for inline asm statements.
11//
12//===----------------------------------------------------------------------===//
13
14#include "clang/Sema/SemaInternal.h"
15#include "clang/Sema/Scope.h"
16#include "clang/Sema/ScopeInfo.h"
17#include "clang/Sema/Initialization.h"
18#include "clang/Sema/Lookup.h"
19#include "clang/AST/TypeLoc.h"
20#include "clang/Lex/Preprocessor.h"
21#include "clang/Basic/TargetInfo.h"
22#include "llvm/ADT/ArrayRef.h"
23#include "llvm/ADT/BitVector.h"
24#include "llvm/ADT/SmallString.h"
25#include "llvm/MC/MCAsmInfo.h"
26#include "llvm/MC/MCContext.h"
27#include "llvm/MC/MCExpr.h"
28#include "llvm/MC/MCInst.h"
29#include "llvm/MC/MCInstPrinter.h"
30#include "llvm/MC/MCInstrInfo.h"
31#include "llvm/MC/MCObjectFileInfo.h"
32#include "llvm/MC/MCRegisterInfo.h"
33#include "llvm/MC/MCStreamer.h"
34#include "llvm/MC/MCSubtargetInfo.h"
35#include "llvm/MC/MCSymbol.h"
36#include "llvm/MC/MCTargetAsmParser.h"
37#include "llvm/MC/MCParser/MCAsmLexer.h"
38#include "llvm/MC/MCParser/MCAsmParser.h"
39#include "llvm/Support/SourceMgr.h"
40#include "llvm/Support/TargetRegistry.h"
41#include "llvm/Support/TargetSelect.h"
42using namespace clang;
43using namespace sema;
44
45/// CheckAsmLValue - GNU C has an extremely ugly extension whereby they silently
46/// ignore "noop" casts in places where an lvalue is required by an inline asm.
47/// We emulate this behavior when -fheinous-gnu-extensions is specified, but
48/// provide a strong guidance to not use it.
49///
50/// This method checks to see if the argument is an acceptable l-value and
51/// returns false if it is a case we can handle.
52static bool CheckAsmLValue(const Expr *E, Sema &S) {
53  // Type dependent expressions will be checked during instantiation.
54  if (E->isTypeDependent())
55    return false;
56
57  if (E->isLValue())
58    return false;  // Cool, this is an lvalue.
59
60  // Okay, this is not an lvalue, but perhaps it is the result of a cast that we
61  // are supposed to allow.
62  const Expr *E2 = E->IgnoreParenNoopCasts(S.Context);
63  if (E != E2 && E2->isLValue()) {
64    if (!S.getLangOpts().HeinousExtensions)
65      S.Diag(E2->getLocStart(), diag::err_invalid_asm_cast_lvalue)
66        << E->getSourceRange();
67    else
68      S.Diag(E2->getLocStart(), diag::warn_invalid_asm_cast_lvalue)
69        << E->getSourceRange();
70    // Accept, even if we emitted an error diagnostic.
71    return false;
72  }
73
74  // None of the above, just randomly invalid non-lvalue.
75  return true;
76}
77
78/// isOperandMentioned - Return true if the specified operand # is mentioned
79/// anywhere in the decomposed asm string.
80static bool isOperandMentioned(unsigned OpNo,
81                         ArrayRef<GCCAsmStmt::AsmStringPiece> AsmStrPieces) {
82  for (unsigned p = 0, e = AsmStrPieces.size(); p != e; ++p) {
83    const GCCAsmStmt::AsmStringPiece &Piece = AsmStrPieces[p];
84    if (!Piece.isOperand()) continue;
85
86    // If this is a reference to the input and if the input was the smaller
87    // one, then we have to reject this asm.
88    if (Piece.getOperandNo() == OpNo)
89      return true;
90  }
91  return false;
92}
93
94StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
95                                 bool IsVolatile, unsigned NumOutputs,
96                                 unsigned NumInputs, IdentifierInfo **Names,
97                                 MultiExprArg constraints, MultiExprArg exprs,
98                                 Expr *asmString, MultiExprArg clobbers,
99                                 SourceLocation RParenLoc) {
100  unsigned NumClobbers = clobbers.size();
101  StringLiteral **Constraints =
102    reinterpret_cast<StringLiteral**>(constraints.data());
103  Expr **Exprs = exprs.data();
104  StringLiteral *AsmString = cast<StringLiteral>(asmString);
105  StringLiteral **Clobbers = reinterpret_cast<StringLiteral**>(clobbers.data());
106
107  SmallVector<TargetInfo::ConstraintInfo, 4> OutputConstraintInfos;
108
109  // The parser verifies that there is a string literal here.
110  if (!AsmString->isAscii())
111    return StmtError(Diag(AsmString->getLocStart(),diag::err_asm_wide_character)
112      << AsmString->getSourceRange());
113
114  for (unsigned i = 0; i != NumOutputs; i++) {
115    StringLiteral *Literal = Constraints[i];
116    if (!Literal->isAscii())
117      return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
118        << Literal->getSourceRange());
119
120    StringRef OutputName;
121    if (Names[i])
122      OutputName = Names[i]->getName();
123
124    TargetInfo::ConstraintInfo Info(Literal->getString(), OutputName);
125    if (!Context.getTargetInfo().validateOutputConstraint(Info))
126      return StmtError(Diag(Literal->getLocStart(),
127                            diag::err_asm_invalid_output_constraint)
128                       << Info.getConstraintStr());
129
130    // Check that the output exprs are valid lvalues.
131    Expr *OutputExpr = Exprs[i];
132    if (CheckAsmLValue(OutputExpr, *this)) {
133      return StmtError(Diag(OutputExpr->getLocStart(),
134                  diag::err_asm_invalid_lvalue_in_output)
135        << OutputExpr->getSourceRange());
136    }
137
138    OutputConstraintInfos.push_back(Info);
139  }
140
141  SmallVector<TargetInfo::ConstraintInfo, 4> InputConstraintInfos;
142
143  for (unsigned i = NumOutputs, e = NumOutputs + NumInputs; i != e; i++) {
144    StringLiteral *Literal = Constraints[i];
145    if (!Literal->isAscii())
146      return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
147        << Literal->getSourceRange());
148
149    StringRef InputName;
150    if (Names[i])
151      InputName = Names[i]->getName();
152
153    TargetInfo::ConstraintInfo Info(Literal->getString(), InputName);
154    if (!Context.getTargetInfo().validateInputConstraint(OutputConstraintInfos.data(),
155                                                NumOutputs, Info)) {
156      return StmtError(Diag(Literal->getLocStart(),
157                            diag::err_asm_invalid_input_constraint)
158                       << Info.getConstraintStr());
159    }
160
161    Expr *InputExpr = Exprs[i];
162
163    // Only allow void types for memory constraints.
164    if (Info.allowsMemory() && !Info.allowsRegister()) {
165      if (CheckAsmLValue(InputExpr, *this))
166        return StmtError(Diag(InputExpr->getLocStart(),
167                              diag::err_asm_invalid_lvalue_in_input)
168                         << Info.getConstraintStr()
169                         << InputExpr->getSourceRange());
170    }
171
172    if (Info.allowsRegister()) {
173      if (InputExpr->getType()->isVoidType()) {
174        return StmtError(Diag(InputExpr->getLocStart(),
175                              diag::err_asm_invalid_type_in_input)
176          << InputExpr->getType() << Info.getConstraintStr()
177          << InputExpr->getSourceRange());
178      }
179    }
180
181    ExprResult Result = DefaultFunctionArrayLvalueConversion(Exprs[i]);
182    if (Result.isInvalid())
183      return StmtError();
184
185    Exprs[i] = Result.take();
186    InputConstraintInfos.push_back(Info);
187  }
188
189  // Check that the clobbers are valid.
190  for (unsigned i = 0; i != NumClobbers; i++) {
191    StringLiteral *Literal = Clobbers[i];
192    if (!Literal->isAscii())
193      return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
194        << Literal->getSourceRange());
195
196    StringRef Clobber = Literal->getString();
197
198    if (!Context.getTargetInfo().isValidClobber(Clobber))
199      return StmtError(Diag(Literal->getLocStart(),
200                  diag::err_asm_unknown_register_name) << Clobber);
201  }
202
203  GCCAsmStmt *NS =
204    new (Context) GCCAsmStmt(Context, AsmLoc, IsSimple, IsVolatile, NumOutputs,
205                             NumInputs, Names, Constraints, Exprs, AsmString,
206                             NumClobbers, Clobbers, RParenLoc);
207  // Validate the asm string, ensuring it makes sense given the operands we
208  // have.
209  SmallVector<GCCAsmStmt::AsmStringPiece, 8> Pieces;
210  unsigned DiagOffs;
211  if (unsigned DiagID = NS->AnalyzeAsmString(Pieces, Context, DiagOffs)) {
212    Diag(getLocationOfStringLiteralByte(AsmString, DiagOffs), DiagID)
213           << AsmString->getSourceRange();
214    return StmtError();
215  }
216
217  // Validate tied input operands for type mismatches.
218  for (unsigned i = 0, e = InputConstraintInfos.size(); i != e; ++i) {
219    TargetInfo::ConstraintInfo &Info = InputConstraintInfos[i];
220
221    // If this is a tied constraint, verify that the output and input have
222    // either exactly the same type, or that they are int/ptr operands with the
223    // same size (int/long, int*/long, are ok etc).
224    if (!Info.hasTiedOperand()) continue;
225
226    unsigned TiedTo = Info.getTiedOperand();
227    unsigned InputOpNo = i+NumOutputs;
228    Expr *OutputExpr = Exprs[TiedTo];
229    Expr *InputExpr = Exprs[InputOpNo];
230
231    if (OutputExpr->isTypeDependent() || InputExpr->isTypeDependent())
232      continue;
233
234    QualType InTy = InputExpr->getType();
235    QualType OutTy = OutputExpr->getType();
236    if (Context.hasSameType(InTy, OutTy))
237      continue;  // All types can be tied to themselves.
238
239    // Decide if the input and output are in the same domain (integer/ptr or
240    // floating point.
241    enum AsmDomain {
242      AD_Int, AD_FP, AD_Other
243    } InputDomain, OutputDomain;
244
245    if (InTy->isIntegerType() || InTy->isPointerType())
246      InputDomain = AD_Int;
247    else if (InTy->isRealFloatingType())
248      InputDomain = AD_FP;
249    else
250      InputDomain = AD_Other;
251
252    if (OutTy->isIntegerType() || OutTy->isPointerType())
253      OutputDomain = AD_Int;
254    else if (OutTy->isRealFloatingType())
255      OutputDomain = AD_FP;
256    else
257      OutputDomain = AD_Other;
258
259    // They are ok if they are the same size and in the same domain.  This
260    // allows tying things like:
261    //   void* to int*
262    //   void* to int            if they are the same size.
263    //   double to long double   if they are the same size.
264    //
265    uint64_t OutSize = Context.getTypeSize(OutTy);
266    uint64_t InSize = Context.getTypeSize(InTy);
267    if (OutSize == InSize && InputDomain == OutputDomain &&
268        InputDomain != AD_Other)
269      continue;
270
271    // If the smaller input/output operand is not mentioned in the asm string,
272    // then we can promote the smaller one to a larger input and the asm string
273    // won't notice.
274    bool SmallerValueMentioned = false;
275
276    // If this is a reference to the input and if the input was the smaller
277    // one, then we have to reject this asm.
278    if (isOperandMentioned(InputOpNo, Pieces)) {
279      // This is a use in the asm string of the smaller operand.  Since we
280      // codegen this by promoting to a wider value, the asm will get printed
281      // "wrong".
282      SmallerValueMentioned |= InSize < OutSize;
283    }
284    if (isOperandMentioned(TiedTo, Pieces)) {
285      // If this is a reference to the output, and if the output is the larger
286      // value, then it's ok because we'll promote the input to the larger type.
287      SmallerValueMentioned |= OutSize < InSize;
288    }
289
290    // If the smaller value wasn't mentioned in the asm string, and if the
291    // output was a register, just extend the shorter one to the size of the
292    // larger one.
293    if (!SmallerValueMentioned && InputDomain != AD_Other &&
294        OutputConstraintInfos[TiedTo].allowsRegister())
295      continue;
296
297    // Either both of the operands were mentioned or the smaller one was
298    // mentioned.  One more special case that we'll allow: if the tied input is
299    // integer, unmentioned, and is a constant, then we'll allow truncating it
300    // down to the size of the destination.
301    if (InputDomain == AD_Int && OutputDomain == AD_Int &&
302        !isOperandMentioned(InputOpNo, Pieces) &&
303        InputExpr->isEvaluatable(Context)) {
304      CastKind castKind =
305        (OutTy->isBooleanType() ? CK_IntegralToBoolean : CK_IntegralCast);
306      InputExpr = ImpCastExprToType(InputExpr, OutTy, castKind).take();
307      Exprs[InputOpNo] = InputExpr;
308      NS->setInputExpr(i, InputExpr);
309      continue;
310    }
311
312    Diag(InputExpr->getLocStart(),
313         diag::err_asm_tying_incompatible_types)
314      << InTy << OutTy << OutputExpr->getSourceRange()
315      << InputExpr->getSourceRange();
316    return StmtError();
317  }
318
319  return Owned(NS);
320}
321
322// isMSAsmKeyword - Return true if this is an MS-style inline asm keyword. These
323// require special handling.
324static bool isMSAsmKeyword(StringRef Name) {
325  bool Ret = llvm::StringSwitch<bool>(Name)
326    .Cases("EVEN", "ALIGN", true) // Alignment directives.
327    .Cases("LENGTH", "SIZE", "TYPE", true) // Type and variable sizes.
328    .Case("_emit", true) // _emit Pseudoinstruction.
329    .Default(false);
330  return Ret;
331}
332
333// getIdentifierInfo - Given a Name and a range of tokens, find the associated
334// IdentifierInfo*.
335static IdentifierInfo *getIdentifierInfo(StringRef Name,
336                                         ArrayRef<Token> AsmToks,
337                                         unsigned Begin, unsigned End) {
338  for (unsigned i = Begin; i <= End; ++i) {
339    IdentifierInfo *II = AsmToks[i].getIdentifierInfo();
340    if (II && II->getName() == Name)
341      return II;
342  }
343  return 0;
344}
345
346// getSpelling - Get the spelling of the AsmTok token.
347static StringRef getSpelling(Sema &SemaRef, Token AsmTok) {
348  StringRef Asm;
349  SmallString<512> TokenBuf;
350  TokenBuf.resize(512);
351  bool StringInvalid = false;
352  Asm = SemaRef.PP.getSpelling(AsmTok, TokenBuf, &StringInvalid);
353  assert (!StringInvalid && "Expected valid string!");
354  return Asm;
355}
356
357// Determine if we should bail on this MSAsm instruction.
358static bool bailOnMSAsm(std::vector<StringRef> Piece) {
359  for (unsigned i = 0, e = Piece.size(); i != e; ++i)
360    if (isMSAsmKeyword(Piece[i]))
361      return true;
362  return false;
363}
364
365// Determine if we should bail on this MSAsm block.
366static bool bailOnMSAsm(std::vector<std::vector<StringRef> > Pieces) {
367  for (unsigned i = 0, e = Pieces.size(); i != e; ++i)
368    if (bailOnMSAsm(Pieces[i]))
369      return true;
370  return false;
371}
372
373// Determine if this is a simple MSAsm instruction.
374static bool isSimpleMSAsm(std::vector<StringRef> &Pieces,
375                          const TargetInfo &TI) {
376  if (isMSAsmKeyword(Pieces[0]))
377      return false;
378
379  for (unsigned i = 1, e = Pieces.size(); i != e; ++i)
380    if (!TI.isValidGCCRegisterName(Pieces[i]))
381      return false;
382  return true;
383}
384
385// Determine if this is a simple MSAsm block.
386static bool isSimpleMSAsm(std::vector<std::vector<StringRef> > Pieces,
387                          const TargetInfo &TI) {
388  for (unsigned i = 0, e = Pieces.size(); i != e; ++i)
389    if (!isSimpleMSAsm(Pieces[i], TI))
390      return false;
391  return true;
392}
393
394// Break the AsmSting into pieces (i.e., mnemonic and operands).
395static void buildMSAsmPieces(StringRef Asm, std::vector<StringRef> &Pieces) {
396  std::pair<StringRef,StringRef> Split = Asm.split(' ');
397
398  // Mnemonic
399  Pieces.push_back(Split.first);
400  Asm = Split.second;
401
402  // Operands
403  while (!Asm.empty()) {
404    Split = Asm.split(", ");
405    Pieces.push_back(Split.first);
406    Asm = Split.second;
407  }
408}
409
410static void buildMSAsmPieces(std::vector<std::string> &AsmStrings,
411                             std::vector<std::vector<StringRef> > &Pieces) {
412  for (unsigned i = 0, e = AsmStrings.size(); i != e; ++i)
413    buildMSAsmPieces(AsmStrings[i], Pieces[i]);
414}
415
416// Build the unmodified AsmString used by the IR.  Also build the individual
417// asm instruction(s) and place them in the AsmStrings vector; these are fed
418// to the AsmParser.
419static std::string buildMSAsmString(Sema &SemaRef, ArrayRef<Token> AsmToks,
420                                    std::vector<std::string> &AsmStrings,
421                     std::vector<std::pair<unsigned,unsigned> > &AsmTokRanges) {
422  assert (!AsmToks.empty() && "Didn't expect an empty AsmToks!");
423
424  SmallString<512> Res;
425  SmallString<512> Asm;
426  unsigned startTok = 0;
427  for (unsigned i = 0, e = AsmToks.size(); i < e; ++i) {
428    bool isNewAsm = i == 0 || AsmToks[i].isAtStartOfLine() ||
429      AsmToks[i].is(tok::kw_asm);
430
431    if (isNewAsm) {
432      if (i) {
433        AsmStrings.push_back(Asm.str());
434        AsmTokRanges.push_back(std::make_pair(startTok, i-1));
435        startTok = i;
436        Res += Asm;
437        Asm.clear();
438        Res += '\n';
439      }
440      if (AsmToks[i].is(tok::kw_asm)) {
441        i++; // Skip __asm
442        assert (i != e && "Expected another token");
443      }
444    }
445
446    if (i && AsmToks[i].hasLeadingSpace() && !isNewAsm)
447      Asm += ' ';
448
449    Asm += getSpelling(SemaRef, AsmToks[i]);
450  }
451  AsmStrings.push_back(Asm.str());
452  AsmTokRanges.push_back(std::make_pair(startTok, AsmToks.size()-1));
453  Res += Asm;
454  return Res.str();
455}
456
457#define DEF_SIMPLE_MSASM                                                     \
458  MSAsmStmt *NS =                                                            \
459    new (Context) MSAsmStmt(Context, AsmLoc, LBraceLoc, /*IsSimple*/ true,   \
460                            /*IsVolatile*/ true, AsmToks, Inputs, Outputs,   \
461                            InputExprs, OutputExprs, AsmString, Constraints, \
462                            Clobbers, EndLoc);
463
464StmtResult Sema::ActOnMSAsmStmt(SourceLocation AsmLoc,
465                                SourceLocation LBraceLoc,
466                                ArrayRef<Token> AsmToks,
467                                SourceLocation EndLoc) {
468  SmallVector<StringRef, 4> Constraints;
469  std::vector<std::string> InputConstraints;
470  std::vector<std::string> OutputConstraints;
471  SmallVector<StringRef, 4> Clobbers;
472  std::set<std::string> ClobberRegs;
473  SmallVector<IdentifierInfo*, 4> Inputs;
474  SmallVector<IdentifierInfo*, 4> Outputs;
475  SmallVector<Expr*, 4> InputExprs;
476  SmallVector<Expr*, 4> OutputExprs;
477
478  // Empty asm statements don't need to instantiate the AsmParser, etc.
479  if (AsmToks.empty()) {
480    StringRef AsmString;
481    DEF_SIMPLE_MSASM;
482    return Owned(NS);
483  }
484
485  std::vector<std::string> AsmStrings;
486  std::vector<std::pair<unsigned,unsigned> > AsmTokRanges;
487  std::string AsmString = buildMSAsmString(*this, AsmToks, AsmStrings,
488                                           AsmTokRanges);
489
490  std::vector<std::vector<StringRef> > Pieces(AsmStrings.size());
491  buildMSAsmPieces(AsmStrings, Pieces);
492
493  bool IsSimple = isSimpleMSAsm(Pieces, Context.getTargetInfo());
494
495  // AsmParser doesn't fully support these asm statements.
496  if (bailOnMSAsm(Pieces)) { DEF_SIMPLE_MSASM; return Owned(NS); }
497
498  // Initialize targets and assembly printers/parsers.
499  llvm::InitializeAllTargetInfos();
500  llvm::InitializeAllTargetMCs();
501  llvm::InitializeAllAsmParsers();
502
503  // Get the target specific parser.
504  std::string Error;
505  const std::string &TT = Context.getTargetInfo().getTriple().getTriple();
506  const llvm::Target *TheTarget(llvm::TargetRegistry::lookupTarget(TT, Error));
507
508  OwningPtr<llvm::MCAsmInfo> MAI(TheTarget->createMCAsmInfo(TT));
509  OwningPtr<llvm::MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TT));
510  OwningPtr<llvm::MCObjectFileInfo> MOFI(new llvm::MCObjectFileInfo());
511  OwningPtr<llvm::MCSubtargetInfo>
512    STI(TheTarget->createMCSubtargetInfo(TT, "", ""));
513
514  for (unsigned StrIdx = 0, e = AsmStrings.size(); StrIdx != e; ++StrIdx) {
515    llvm::SourceMgr SrcMgr;
516    llvm::MCContext Ctx(*MAI, *MRI, MOFI.get(), &SrcMgr);
517    llvm::MemoryBuffer *Buffer =
518      llvm::MemoryBuffer::getMemBuffer(AsmStrings[StrIdx], "<inline asm>");
519
520    // Tell SrcMgr about this buffer, which is what the parser will pick up.
521    SrcMgr.AddNewSourceBuffer(Buffer, llvm::SMLoc());
522
523    OwningPtr<llvm::MCStreamer> Str(createNullStreamer(Ctx));
524    OwningPtr<llvm::MCAsmParser>
525      Parser(createMCAsmParser(SrcMgr, Ctx, *Str.get(), *MAI));
526    OwningPtr<llvm::MCTargetAsmParser>
527      TargetParser(TheTarget->createMCAsmParser(*STI, *Parser));
528    // Change to the Intel dialect.
529    Parser->setAssemblerDialect(1);
530    Parser->setTargetParser(*TargetParser.get());
531
532    // Prime the lexer.
533    Parser->Lex();
534
535    // Parse the opcode.
536    StringRef IDVal;
537    Parser->ParseIdentifier(IDVal);
538
539    // Canonicalize the opcode to lower case.
540    SmallString<128> Opcode;
541    for (unsigned i = 0, e = IDVal.size(); i != e; ++i)
542      Opcode.push_back(tolower(IDVal[i]));
543
544    // Parse the operands.
545    llvm::SMLoc IDLoc;
546    SmallVector<llvm::MCParsedAsmOperand*, 8> Operands;
547    bool HadError = TargetParser->ParseInstruction(Opcode.str(), IDLoc,
548                                                   Operands);
549    // If we had an error parsing the operands, fail gracefully.
550    if (HadError) { DEF_SIMPLE_MSASM; return Owned(NS); }
551
552    // Match the MCInstr.
553    unsigned ErrorInfo;
554    SmallVector<llvm::MCInst, 2> Instrs;
555    HadError = TargetParser->MatchInstruction(IDLoc, Operands, Instrs,
556                                              ErrorInfo,
557                                              /*matchingInlineAsm*/ true);
558    // If we had an error parsing the operands, fail gracefully.
559    if (HadError) { DEF_SIMPLE_MSASM; return Owned(NS); }
560
561    // Get the instruction descriptor.
562    llvm::MCInst Inst = Instrs[0];
563    const llvm::MCInstrInfo *MII = TheTarget->createMCInstrInfo();
564    const llvm::MCInstrDesc &Desc = MII->get(Inst.getOpcode());
565    llvm::MCInstPrinter *IP =
566      TheTarget->createMCInstPrinter(1, *MAI, *MII, *MRI, *STI);
567
568    // Build the list of clobbers, outputs and inputs.
569    unsigned NumDefs = Desc.getNumDefs();
570    for (unsigned i = 0, e = Inst.getNumOperands(); i != e; ++i) {
571      const llvm::MCOperand &Op = Inst.getOperand(i);
572
573      // Immediate.
574      if (Op.isImm() || Op.isFPImm())
575        continue;
576
577      bool isDef = NumDefs && (i < NumDefs);
578
579      // Register/Clobber.
580      if (Op.isReg() && isDef) {
581        std::string Reg;
582        llvm::raw_string_ostream OS(Reg);
583        IP->printRegName(OS, Op.getReg());
584
585        StringRef Clobber(OS.str());
586        if (!Context.getTargetInfo().isValidClobber(Clobber))
587          return StmtError(Diag(AsmLoc, diag::err_asm_unknown_register_name) <<
588                           Clobber);
589        ClobberRegs.insert(Reg);
590        continue;
591      }
592      // Expr/Input or Output.
593      if (Op.isExpr()) {
594        const llvm::MCExpr *Expr = Op.getExpr();
595        const llvm::MCSymbolRefExpr *SymRef;
596        if ((SymRef = dyn_cast<llvm::MCSymbolRefExpr>(Expr))) {
597          StringRef Name = SymRef->getSymbol().getName();
598          IdentifierInfo *II = getIdentifierInfo(Name, AsmToks,
599                                                 AsmTokRanges[StrIdx].first,
600                                                 AsmTokRanges[StrIdx].second);
601          if (II) {
602            CXXScopeSpec SS;
603            UnqualifiedId Id;
604            SourceLocation Loc;
605            Id.setIdentifier(II, AsmLoc);
606            ExprResult Result = ActOnIdExpression(getCurScope(), SS, Loc, Id,
607                                                  false, false);
608            if (!Result.isInvalid()) {
609              if (isDef) {
610                Outputs.push_back(II);
611                OutputExprs.push_back(Result.take());
612                OutputConstraints.push_back("=r");
613              } else {
614                Inputs.push_back(II);
615                InputExprs.push_back(Result.take());
616                InputConstraints.push_back("r");
617              }
618            }
619          }
620        }
621      }
622    }
623  }
624  for (std::set<std::string>::iterator I = ClobberRegs.begin(),
625         E = ClobberRegs.end(); I != E; ++I)
626    Clobbers.push_back(*I);
627
628  // Merge the output and input constraints.  Output constraints are expected
629  // first.
630  for (std::vector<std::string>::iterator I = OutputConstraints.begin(),
631         E = OutputConstraints.end(); I != E; ++I)
632    Constraints.push_back(*I);
633
634  for (std::vector<std::string>::iterator I = InputConstraints.begin(),
635         E = InputConstraints.end(); I != E; ++I)
636    Constraints.push_back(*I);
637
638  MSAsmStmt *NS =
639    new (Context) MSAsmStmt(Context, AsmLoc, LBraceLoc, IsSimple,
640                            /*IsVolatile*/ true, AsmToks, Inputs, Outputs,
641                            InputExprs, OutputExprs, AsmString, Constraints,
642                            Clobbers, EndLoc);
643  return Owned(NS);
644}
645