SemaStmtAsm.cpp revision fd5e56e35404cb44130b17546b6b5c1b33709d23 
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/MCInst.h"
28#include "llvm/MC/MCInstPrinter.h"
29#include "llvm/MC/MCInstrInfo.h"
30#include "llvm/MC/MCObjectFileInfo.h"
31#include "llvm/MC/MCRegisterInfo.h"
32#include "llvm/MC/MCStreamer.h"
33#include "llvm/MC/MCSubtargetInfo.h"
34#include "llvm/MC/MCTargetAsmParser.h"
35#include "llvm/MC/MCParser/MCAsmLexer.h"
36#include "llvm/MC/MCParser/MCAsmParser.h"
37#include "llvm/Support/SourceMgr.h"
38#include "llvm/Support/TargetRegistry.h"
39#include "llvm/Support/TargetSelect.h"
40using namespace clang;
41using namespace sema;
42
43/// CheckAsmLValue - GNU C has an extremely ugly extension whereby they silently
44/// ignore "noop" casts in places where an lvalue is required by an inline asm.
45/// We emulate this behavior when -fheinous-gnu-extensions is specified, but
46/// provide a strong guidance to not use it.
47///
48/// This method checks to see if the argument is an acceptable l-value and
49/// returns false if it is a case we can handle.
50static bool CheckAsmLValue(const Expr *E, Sema &S) {
51  // Type dependent expressions will be checked during instantiation.
52  if (E->isTypeDependent())
53    return false;
54
55  if (E->isLValue())
56    return false;  // Cool, this is an lvalue.
57
58  // Okay, this is not an lvalue, but perhaps it is the result of a cast that we
59  // are supposed to allow.
60  const Expr *E2 = E->IgnoreParenNoopCasts(S.Context);
61  if (E != E2 && E2->isLValue()) {
62    if (!S.getLangOpts().HeinousExtensions)
63      S.Diag(E2->getLocStart(), diag::err_invalid_asm_cast_lvalue)
64        << E->getSourceRange();
65    else
66      S.Diag(E2->getLocStart(), diag::warn_invalid_asm_cast_lvalue)
67        << E->getSourceRange();
68    // Accept, even if we emitted an error diagnostic.
69    return false;
70  }
71
72  // None of the above, just randomly invalid non-lvalue.
73  return true;
74}
75
76/// isOperandMentioned - Return true if the specified operand # is mentioned
77/// anywhere in the decomposed asm string.
78static bool isOperandMentioned(unsigned OpNo,
79                         ArrayRef<AsmStmt::AsmStringPiece> AsmStrPieces) {
80  for (unsigned p = 0, e = AsmStrPieces.size(); p != e; ++p) {
81    const AsmStmt::AsmStringPiece &Piece = AsmStrPieces[p];
82    if (!Piece.isOperand()) continue;
83
84    // If this is a reference to the input and if the input was the smaller
85    // one, then we have to reject this asm.
86    if (Piece.getOperandNo() == OpNo)
87      return true;
88  }
89  return false;
90}
91
92StmtResult Sema::ActOnAsmStmt(SourceLocation AsmLoc, bool IsSimple,
93                              bool IsVolatile, unsigned NumOutputs,
94                              unsigned NumInputs, IdentifierInfo **Names,
95                              MultiExprArg constraints, MultiExprArg exprs,
96                              Expr *asmString, MultiExprArg clobbers,
97                              SourceLocation RParenLoc) {
98  unsigned NumClobbers = clobbers.size();
99  StringLiteral **Constraints =
100    reinterpret_cast<StringLiteral**>(constraints.get());
101  Expr **Exprs = exprs.get();
102  StringLiteral *AsmString = cast<StringLiteral>(asmString);
103  StringLiteral **Clobbers = reinterpret_cast<StringLiteral**>(clobbers.get());
104
105  SmallVector<TargetInfo::ConstraintInfo, 4> OutputConstraintInfos;
106
107  // The parser verifies that there is a string literal here.
108  if (!AsmString->isAscii())
109    return StmtError(Diag(AsmString->getLocStart(),diag::err_asm_wide_character)
110      << AsmString->getSourceRange());
111
112  for (unsigned i = 0; i != NumOutputs; i++) {
113    StringLiteral *Literal = Constraints[i];
114    if (!Literal->isAscii())
115      return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
116        << Literal->getSourceRange());
117
118    StringRef OutputName;
119    if (Names[i])
120      OutputName = Names[i]->getName();
121
122    TargetInfo::ConstraintInfo Info(Literal->getString(), OutputName);
123    if (!Context.getTargetInfo().validateOutputConstraint(Info))
124      return StmtError(Diag(Literal->getLocStart(),
125                            diag::err_asm_invalid_output_constraint)
126                       << Info.getConstraintStr());
127
128    // Check that the output exprs are valid lvalues.
129    Expr *OutputExpr = Exprs[i];
130    if (CheckAsmLValue(OutputExpr, *this)) {
131      return StmtError(Diag(OutputExpr->getLocStart(),
132                  diag::err_asm_invalid_lvalue_in_output)
133        << OutputExpr->getSourceRange());
134    }
135
136    OutputConstraintInfos.push_back(Info);
137  }
138
139  SmallVector<TargetInfo::ConstraintInfo, 4> InputConstraintInfos;
140
141  for (unsigned i = NumOutputs, e = NumOutputs + NumInputs; i != e; i++) {
142    StringLiteral *Literal = Constraints[i];
143    if (!Literal->isAscii())
144      return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
145        << Literal->getSourceRange());
146
147    StringRef InputName;
148    if (Names[i])
149      InputName = Names[i]->getName();
150
151    TargetInfo::ConstraintInfo Info(Literal->getString(), InputName);
152    if (!Context.getTargetInfo().validateInputConstraint(OutputConstraintInfos.data(),
153                                                NumOutputs, Info)) {
154      return StmtError(Diag(Literal->getLocStart(),
155                            diag::err_asm_invalid_input_constraint)
156                       << Info.getConstraintStr());
157    }
158
159    Expr *InputExpr = Exprs[i];
160
161    // Only allow void types for memory constraints.
162    if (Info.allowsMemory() && !Info.allowsRegister()) {
163      if (CheckAsmLValue(InputExpr, *this))
164        return StmtError(Diag(InputExpr->getLocStart(),
165                              diag::err_asm_invalid_lvalue_in_input)
166                         << Info.getConstraintStr()
167                         << InputExpr->getSourceRange());
168    }
169
170    if (Info.allowsRegister()) {
171      if (InputExpr->getType()->isVoidType()) {
172        return StmtError(Diag(InputExpr->getLocStart(),
173                              diag::err_asm_invalid_type_in_input)
174          << InputExpr->getType() << Info.getConstraintStr()
175          << InputExpr->getSourceRange());
176      }
177    }
178
179    ExprResult Result = DefaultFunctionArrayLvalueConversion(Exprs[i]);
180    if (Result.isInvalid())
181      return StmtError();
182
183    Exprs[i] = Result.take();
184    InputConstraintInfos.push_back(Info);
185  }
186
187  // Check that the clobbers are valid.
188  for (unsigned i = 0; i != NumClobbers; i++) {
189    StringLiteral *Literal = Clobbers[i];
190    if (!Literal->isAscii())
191      return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
192        << Literal->getSourceRange());
193
194    StringRef Clobber = Literal->getString();
195
196    if (!Context.getTargetInfo().isValidClobber(Clobber))
197      return StmtError(Diag(Literal->getLocStart(),
198                  diag::err_asm_unknown_register_name) << Clobber);
199  }
200
201  AsmStmt *NS =
202    new (Context) AsmStmt(Context, AsmLoc, IsSimple, IsVolatile, NumOutputs,
203                          NumInputs, Names, Constraints, Exprs, AsmString,
204                          NumClobbers, Clobbers, RParenLoc);
205  // Validate the asm string, ensuring it makes sense given the operands we
206  // have.
207  SmallVector<AsmStmt::AsmStringPiece, 8> Pieces;
208  unsigned DiagOffs;
209  if (unsigned DiagID = NS->AnalyzeAsmString(Pieces, Context, DiagOffs)) {
210    Diag(getLocationOfStringLiteralByte(AsmString, DiagOffs), DiagID)
211           << AsmString->getSourceRange();
212    return StmtError();
213  }
214
215  // Validate tied input operands for type mismatches.
216  for (unsigned i = 0, e = InputConstraintInfos.size(); i != e; ++i) {
217    TargetInfo::ConstraintInfo &Info = InputConstraintInfos[i];
218
219    // If this is a tied constraint, verify that the output and input have
220    // either exactly the same type, or that they are int/ptr operands with the
221    // same size (int/long, int*/long, are ok etc).
222    if (!Info.hasTiedOperand()) continue;
223
224    unsigned TiedTo = Info.getTiedOperand();
225    unsigned InputOpNo = i+NumOutputs;
226    Expr *OutputExpr = Exprs[TiedTo];
227    Expr *InputExpr = Exprs[InputOpNo];
228
229    if (OutputExpr->isTypeDependent() || InputExpr->isTypeDependent())
230      continue;
231
232    QualType InTy = InputExpr->getType();
233    QualType OutTy = OutputExpr->getType();
234    if (Context.hasSameType(InTy, OutTy))
235      continue;  // All types can be tied to themselves.
236
237    // Decide if the input and output are in the same domain (integer/ptr or
238    // floating point.
239    enum AsmDomain {
240      AD_Int, AD_FP, AD_Other
241    } InputDomain, OutputDomain;
242
243    if (InTy->isIntegerType() || InTy->isPointerType())
244      InputDomain = AD_Int;
245    else if (InTy->isRealFloatingType())
246      InputDomain = AD_FP;
247    else
248      InputDomain = AD_Other;
249
250    if (OutTy->isIntegerType() || OutTy->isPointerType())
251      OutputDomain = AD_Int;
252    else if (OutTy->isRealFloatingType())
253      OutputDomain = AD_FP;
254    else
255      OutputDomain = AD_Other;
256
257    // They are ok if they are the same size and in the same domain.  This
258    // allows tying things like:
259    //   void* to int*
260    //   void* to int            if they are the same size.
261    //   double to long double   if they are the same size.
262    //
263    uint64_t OutSize = Context.getTypeSize(OutTy);
264    uint64_t InSize = Context.getTypeSize(InTy);
265    if (OutSize == InSize && InputDomain == OutputDomain &&
266        InputDomain != AD_Other)
267      continue;
268
269    // If the smaller input/output operand is not mentioned in the asm string,
270    // then we can promote the smaller one to a larger input and the asm string
271    // won't notice.
272    bool SmallerValueMentioned = false;
273
274    // If this is a reference to the input and if the input was the smaller
275    // one, then we have to reject this asm.
276    if (isOperandMentioned(InputOpNo, Pieces)) {
277      // This is a use in the asm string of the smaller operand.  Since we
278      // codegen this by promoting to a wider value, the asm will get printed
279      // "wrong".
280      SmallerValueMentioned |= InSize < OutSize;
281    }
282    if (isOperandMentioned(TiedTo, Pieces)) {
283      // If this is a reference to the output, and if the output is the larger
284      // value, then it's ok because we'll promote the input to the larger type.
285      SmallerValueMentioned |= OutSize < InSize;
286    }
287
288    // If the smaller value wasn't mentioned in the asm string, and if the
289    // output was a register, just extend the shorter one to the size of the
290    // larger one.
291    if (!SmallerValueMentioned && InputDomain != AD_Other &&
292        OutputConstraintInfos[TiedTo].allowsRegister())
293      continue;
294
295    // Either both of the operands were mentioned or the smaller one was
296    // mentioned.  One more special case that we'll allow: if the tied input is
297    // integer, unmentioned, and is a constant, then we'll allow truncating it
298    // down to the size of the destination.
299    if (InputDomain == AD_Int && OutputDomain == AD_Int &&
300        !isOperandMentioned(InputOpNo, Pieces) &&
301        InputExpr->isEvaluatable(Context)) {
302      CastKind castKind =
303        (OutTy->isBooleanType() ? CK_IntegralToBoolean : CK_IntegralCast);
304      InputExpr = ImpCastExprToType(InputExpr, OutTy, castKind).take();
305      Exprs[InputOpNo] = InputExpr;
306      NS->setInputExpr(i, InputExpr);
307      continue;
308    }
309
310    Diag(InputExpr->getLocStart(),
311         diag::err_asm_tying_incompatible_types)
312      << InTy << OutTy << OutputExpr->getSourceRange()
313      << InputExpr->getSourceRange();
314    return StmtError();
315  }
316
317  return Owned(NS);
318}
319
320// isMSAsmKeyword - Return true if this is an MS-style inline asm keyword. These
321// require special handling.
322static bool isMSAsmKeyword(StringRef Name) {
323  bool Ret = llvm::StringSwitch<bool>(Name)
324    .Cases("EVEN", "ALIGN", true) // Alignment directives.
325    .Cases("LENGTH", "SIZE", "TYPE", true) // Type and variable sizes.
326    .Case("_emit", true) // _emit Pseudoinstruction.
327    .Default(false);
328  return Ret;
329}
330
331// getSpelling - Get the spelling of the AsmTok token.
332static StringRef getSpelling(Sema &SemaRef, Token AsmTok) {
333  StringRef Asm;
334  SmallString<512> TokenBuf;
335  TokenBuf.resize(512);
336  bool StringInvalid = false;
337  Asm = SemaRef.PP.getSpelling(AsmTok, TokenBuf, &StringInvalid);
338  assert (!StringInvalid && "Expected valid string!");
339  return Asm;
340}
341
342// Determine if we should bail on this MSAsm instruction.
343static bool bailOnMSAsm(std::vector<StringRef> Piece) {
344  for (unsigned i = 0, e = Piece.size(); i != e; ++i)
345    if (isMSAsmKeyword(Piece[i]))
346      return true;
347  return false;
348}
349
350// Determine if we should bail on this MSAsm block.
351static bool bailOnMSAsm(std::vector<std::vector<StringRef> > Pieces) {
352  for (unsigned i = 0, e = Pieces.size(); i != e; ++i)
353    if (bailOnMSAsm(Pieces[i]))
354      return true;
355  return false;
356}
357
358// Determine if this is a simple MSAsm instruction.
359static bool isSimpleMSAsm(std::vector<StringRef> &Pieces,
360                          const TargetInfo &TI) {
361  if (isMSAsmKeyword(Pieces[0]))
362      return false;
363
364  for (unsigned i = 1, e = Pieces.size(); i != e; ++i)
365    if (!TI.isValidGCCRegisterName(Pieces[i]))
366      return false;
367  return true;
368}
369
370// Determine if this is a simple MSAsm block.
371static bool isSimpleMSAsm(std::vector<std::vector<StringRef> > Pieces,
372                          const TargetInfo &TI) {
373  for (unsigned i = 0, e = Pieces.size(); i != e; ++i)
374    if (!isSimpleMSAsm(Pieces[i], TI))
375      return false;
376  return true;
377}
378
379// Break the AsmSting into pieces (i.e., mnemonic and operands).
380static void buildMSAsmPieces(StringRef Asm, std::vector<StringRef> &Pieces) {
381  std::pair<StringRef,StringRef> Split = Asm.split(' ');
382
383  // Mnemonic
384  Pieces.push_back(Split.first);
385  Asm = Split.second;
386
387  // Operands
388  while (!Asm.empty()) {
389    Split = Asm.split(", ");
390    Pieces.push_back(Split.first);
391    Asm = Split.second;
392  }
393}
394
395static void buildMSAsmPieces(std::vector<std::string> &AsmStrings,
396                             std::vector<std::vector<StringRef> > &Pieces) {
397  for (unsigned i = 0, e = AsmStrings.size(); i != e; ++i)
398    buildMSAsmPieces(AsmStrings[i], Pieces[i]);
399}
400
401// Build the unmodified AsmString used by the IR.  Also build the individual
402// asm instruction(s) and place them in the AsmStrings vector; these are fed
403// to the AsmParser.
404static std::string buildMSAsmString(Sema &SemaRef, ArrayRef<Token> AsmToks,
405                                    std::vector<std::string> &AsmStrings,
406                     std::vector<std::pair<unsigned,unsigned> > &AsmTokRanges) {
407  assert (!AsmToks.empty() && "Didn't expect an empty AsmToks!");
408
409  SmallString<512> Res;
410  SmallString<512> Asm;
411  unsigned startTok = 0;
412  for (unsigned i = 0, e = AsmToks.size(); i < e; ++i) {
413    bool isNewAsm = i == 0 || AsmToks[i].isAtStartOfLine() ||
414      AsmToks[i].is(tok::kw_asm);
415
416    if (isNewAsm) {
417      if (i) {
418        AsmStrings.push_back(Asm.c_str());
419        AsmTokRanges.push_back(std::make_pair(startTok, i-1));
420        startTok = i;
421        Res += Asm;
422        Asm.clear();
423        Res += '\n';
424      }
425      if (AsmToks[i].is(tok::kw_asm)) {
426        i++; // Skip __asm
427        assert (i != e && "Expected another token");
428      }
429    }
430
431    if (i && AsmToks[i].hasLeadingSpace() && !isNewAsm)
432      Asm += ' ';
433
434    Asm += getSpelling(SemaRef, AsmToks[i]);
435  }
436  AsmStrings.push_back(Asm.c_str());
437  AsmTokRanges.push_back(std::make_pair(startTok, AsmToks.size()-1));
438  Res += Asm;
439  return Res.c_str();
440}
441
442#define DEF_SIMPLE_MSASM                                                   \
443  MSAsmStmt *NS =                                                          \
444    new (Context) MSAsmStmt(Context, AsmLoc, LBraceLoc, /*IsSimple*/ true, \
445                            /*IsVolatile*/ true, AsmToks, Inputs, Outputs, \
446                            AsmString, Clobbers, EndLoc);
447
448StmtResult Sema::ActOnMSAsmStmt(SourceLocation AsmLoc,
449                                SourceLocation LBraceLoc,
450                                ArrayRef<Token> AsmToks,
451                                SourceLocation EndLoc) {
452  // MS-style inline assembly is not fully supported, so emit a warning.
453  Diag(AsmLoc, diag::warn_unsupported_msasm);
454  SmallVector<StringRef,4> Clobbers;
455  std::set<std::string> ClobberRegs;
456  SmallVector<IdentifierInfo*, 4> Inputs;
457  SmallVector<IdentifierInfo*, 4> Outputs;
458
459  // Empty asm statements don't need to instantiate the AsmParser, etc.
460  if (AsmToks.empty()) {
461    StringRef AsmString;
462    DEF_SIMPLE_MSASM;
463    return Owned(NS);
464  }
465
466  std::vector<std::string> AsmStrings;
467  std::vector<std::pair<unsigned,unsigned> > AsmTokRanges;
468  std::string AsmString = buildMSAsmString(*this, AsmToks, AsmStrings, AsmTokRanges);
469
470  std::vector<std::vector<StringRef> > Pieces(AsmStrings.size());
471  buildMSAsmPieces(AsmStrings, Pieces);
472
473  bool IsSimple = isSimpleMSAsm(Pieces, Context.getTargetInfo());
474
475  // AsmParser doesn't fully support these asm statements.
476  if (bailOnMSAsm(Pieces)) { DEF_SIMPLE_MSASM; return Owned(NS); }
477
478  // Initialize targets and assembly printers/parsers.
479  llvm::InitializeAllTargetInfos();
480  llvm::InitializeAllTargetMCs();
481  llvm::InitializeAllAsmParsers();
482
483  // Get the target specific parser.
484  std::string Error;
485  const std::string &TT = Context.getTargetInfo().getTriple().getTriple();
486  const llvm::Target *TheTarget(llvm::TargetRegistry::lookupTarget(TT, Error));
487
488  OwningPtr<llvm::MCAsmInfo> MAI(TheTarget->createMCAsmInfo(TT));
489  OwningPtr<llvm::MCRegisterInfo> MRI(TheTarget->createMCRegInfo(TT));
490  OwningPtr<llvm::MCObjectFileInfo> MOFI(new llvm::MCObjectFileInfo());
491  OwningPtr<llvm::MCSubtargetInfo>
492    STI(TheTarget->createMCSubtargetInfo(TT, "", ""));
493
494  for (unsigned i = 0, e = AsmStrings.size(); i != e; ++i) {
495    llvm::SourceMgr SrcMgr;
496    llvm::MCContext Ctx(*MAI, *MRI, MOFI.get(), &SrcMgr);
497    llvm::MemoryBuffer *Buffer =
498      llvm::MemoryBuffer::getMemBuffer(AsmStrings[i], "<inline asm>");
499
500    // Tell SrcMgr about this buffer, which is what the parser will pick up.
501    SrcMgr.AddNewSourceBuffer(Buffer, llvm::SMLoc());
502
503    OwningPtr<llvm::MCStreamer> Str(createNullStreamer(Ctx));
504    OwningPtr<llvm::MCAsmParser>
505      Parser(createMCAsmParser(SrcMgr, Ctx, *Str.get(), *MAI));
506    OwningPtr<llvm::MCTargetAsmParser>
507      TargetParser(TheTarget->createMCAsmParser(*STI, *Parser));
508    // Change to the Intel dialect.
509    Parser->setAssemblerDialect(1);
510    Parser->setTargetParser(*TargetParser.get());
511
512    // Prime the lexer.
513    Parser->Lex();
514
515    // Parse the opcode.
516    StringRef IDVal;
517    Parser->ParseIdentifier(IDVal);
518
519    // Canonicalize the opcode to lower case.
520    SmallString<128> Opcode;
521    for (unsigned i = 0, e = IDVal.size(); i != e; ++i)
522      Opcode.push_back(tolower(IDVal[i]));
523
524    // Parse the operands.
525    llvm::SMLoc IDLoc;
526    SmallVector<llvm::MCParsedAsmOperand*, 8> Operands;
527    bool HadError = TargetParser->ParseInstruction(Opcode.str(), IDLoc,
528                                                   Operands);
529    // If we had an error parsing the operands, fail gracefully.
530    if (HadError) { DEF_SIMPLE_MSASM; return Owned(NS); }
531
532    // Match the MCInstr.
533    unsigned ErrorInfo;
534    SmallVector<llvm::MCInst, 2> Instrs;
535    HadError = TargetParser->MatchInstruction(IDLoc, Operands, Instrs,
536                                              ErrorInfo,
537                                              /*matchingInlineAsm*/ true);
538    // If we had an error parsing the operands, fail gracefully.
539    if (HadError) { DEF_SIMPLE_MSASM; return Owned(NS); }
540
541    // Get the instruction descriptor.
542    llvm::MCInst Inst = Instrs[0];
543    const llvm::MCInstrInfo *MII = TheTarget->createMCInstrInfo();
544    const llvm::MCInstrDesc &Desc = MII->get(Inst.getOpcode());
545    llvm::MCInstPrinter *IP =
546      TheTarget->createMCInstPrinter(1, *MAI, *MII, *MRI, *STI);
547
548    // Build the list of clobbers.
549    unsigned NumDefs = Desc.getNumDefs();
550    for (unsigned j = 0, e = Inst.getNumOperands(); j != e; ++j) {
551      const llvm::MCOperand &Op = Inst.getOperand(j);
552
553      // Immediate.
554      if (Op.isImm() || Op.isFPImm())
555        continue;
556
557      bool isDef = NumDefs && (j < NumDefs);
558
559      // Register/Clobber.
560      if (Op.isReg() && isDef) {
561        std::string Reg;
562        llvm::raw_string_ostream OS(Reg);
563        IP->printRegName(OS, Op.getReg());
564
565        StringRef Clobber(OS.str());
566        if (!Context.getTargetInfo().isValidClobber(Clobber))
567          return StmtError(Diag(AsmLoc, diag::err_asm_unknown_register_name) <<
568                           Clobber);
569        ClobberRegs.insert(Reg);
570      }
571    }
572  }
573  for (std::set<std::string>::iterator I = ClobberRegs.begin(),
574         E = ClobberRegs.end(); I != E; ++I)
575    Clobbers.push_back(*I);
576
577  MSAsmStmt *NS =
578    new (Context) MSAsmStmt(Context, AsmLoc, LBraceLoc, IsSimple,
579                            /*IsVolatile*/ true, AsmToks, Inputs, Outputs,
580                            AsmString, Clobbers, EndLoc);
581  return Owned(NS);
582}
583