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      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/AST/ExprCXX.h"
     16 #include "clang/AST/RecordLayout.h"
     17 #include "clang/AST/TypeLoc.h"
     18 #include "clang/Basic/TargetInfo.h"
     19 #include "clang/Lex/Preprocessor.h"
     20 #include "clang/Sema/Initialization.h"
     21 #include "clang/Sema/Lookup.h"
     22 #include "clang/Sema/Scope.h"
     23 #include "clang/Sema/ScopeInfo.h"
     24 #include "llvm/ADT/ArrayRef.h"
     25 #include "llvm/ADT/BitVector.h"
     26 #include "llvm/MC/MCParser/MCAsmParser.h"
     27 using namespace clang;
     28 using namespace sema;
     29 
     30 /// CheckAsmLValue - GNU C has an extremely ugly extension whereby they silently
     31 /// ignore "noop" casts in places where an lvalue is required by an inline asm.
     32 /// We emulate this behavior when -fheinous-gnu-extensions is specified, but
     33 /// provide a strong guidance to not use it.
     34 ///
     35 /// This method checks to see if the argument is an acceptable l-value and
     36 /// returns false if it is a case we can handle.
     37 static bool CheckAsmLValue(const Expr *E, Sema &S) {
     38   // Type dependent expressions will be checked during instantiation.
     39   if (E->isTypeDependent())
     40     return false;
     41 
     42   if (E->isLValue())
     43     return false;  // Cool, this is an lvalue.
     44 
     45   // Okay, this is not an lvalue, but perhaps it is the result of a cast that we
     46   // are supposed to allow.
     47   const Expr *E2 = E->IgnoreParenNoopCasts(S.Context);
     48   if (E != E2 && E2->isLValue()) {
     49     if (!S.getLangOpts().HeinousExtensions)
     50       S.Diag(E2->getLocStart(), diag::err_invalid_asm_cast_lvalue)
     51         << E->getSourceRange();
     52     else
     53       S.Diag(E2->getLocStart(), diag::warn_invalid_asm_cast_lvalue)
     54         << E->getSourceRange();
     55     // Accept, even if we emitted an error diagnostic.
     56     return false;
     57   }
     58 
     59   // None of the above, just randomly invalid non-lvalue.
     60   return true;
     61 }
     62 
     63 /// isOperandMentioned - Return true if the specified operand # is mentioned
     64 /// anywhere in the decomposed asm string.
     65 static bool isOperandMentioned(unsigned OpNo,
     66                          ArrayRef<GCCAsmStmt::AsmStringPiece> AsmStrPieces) {
     67   for (unsigned p = 0, e = AsmStrPieces.size(); p != e; ++p) {
     68     const GCCAsmStmt::AsmStringPiece &Piece = AsmStrPieces[p];
     69     if (!Piece.isOperand()) continue;
     70 
     71     // If this is a reference to the input and if the input was the smaller
     72     // one, then we have to reject this asm.
     73     if (Piece.getOperandNo() == OpNo)
     74       return true;
     75   }
     76   return false;
     77 }
     78 
     79 static bool CheckNakedParmReference(Expr *E, Sema &S) {
     80   FunctionDecl *Func = dyn_cast<FunctionDecl>(S.CurContext);
     81   if (!Func)
     82     return false;
     83   if (!Func->hasAttr<NakedAttr>())
     84     return false;
     85 
     86   SmallVector<Expr*, 4> WorkList;
     87   WorkList.push_back(E);
     88   while (WorkList.size()) {
     89     Expr *E = WorkList.pop_back_val();
     90     if (isa<CXXThisExpr>(E)) {
     91       S.Diag(E->getLocStart(), diag::err_asm_naked_this_ref);
     92       S.Diag(Func->getAttr<NakedAttr>()->getLocation(), diag::note_attribute);
     93       return true;
     94     }
     95     if (DeclRefExpr *DRE = dyn_cast<DeclRefExpr>(E)) {
     96       if (isa<ParmVarDecl>(DRE->getDecl())) {
     97         S.Diag(DRE->getLocStart(), diag::err_asm_naked_parm_ref);
     98         S.Diag(Func->getAttr<NakedAttr>()->getLocation(), diag::note_attribute);
     99         return true;
    100       }
    101     }
    102     for (Stmt *Child : E->children()) {
    103       if (Expr *E = dyn_cast_or_null<Expr>(Child))
    104         WorkList.push_back(E);
    105     }
    106   }
    107   return false;
    108 }
    109 
    110 /// \brief Returns true if given expression is not compatible with inline
    111 /// assembly's memory constraint; false otherwise.
    112 static bool checkExprMemoryConstraintCompat(Sema &S, Expr *E,
    113                                             TargetInfo::ConstraintInfo &Info,
    114                                             bool is_input_expr) {
    115   enum {
    116     ExprBitfield = 0,
    117     ExprVectorElt,
    118     ExprGlobalRegVar,
    119     ExprSafeType
    120   } EType = ExprSafeType;
    121 
    122   // Bitfields, vector elements and global register variables are not
    123   // compatible.
    124   if (E->refersToBitField())
    125     EType = ExprBitfield;
    126   else if (E->refersToVectorElement())
    127     EType = ExprVectorElt;
    128   else if (E->refersToGlobalRegisterVar())
    129     EType = ExprGlobalRegVar;
    130 
    131   if (EType != ExprSafeType) {
    132     S.Diag(E->getLocStart(), diag::err_asm_non_addr_value_in_memory_constraint)
    133         << EType << is_input_expr << Info.getConstraintStr()
    134         << E->getSourceRange();
    135     return true;
    136   }
    137 
    138   return false;
    139 }
    140 
    141 StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
    142                                  bool IsVolatile, unsigned NumOutputs,
    143                                  unsigned NumInputs, IdentifierInfo **Names,
    144                                  MultiExprArg constraints, MultiExprArg Exprs,
    145                                  Expr *asmString, MultiExprArg clobbers,
    146                                  SourceLocation RParenLoc) {
    147   unsigned NumClobbers = clobbers.size();
    148   StringLiteral **Constraints =
    149     reinterpret_cast<StringLiteral**>(constraints.data());
    150   StringLiteral *AsmString = cast<StringLiteral>(asmString);
    151   StringLiteral **Clobbers = reinterpret_cast<StringLiteral**>(clobbers.data());
    152 
    153   SmallVector<TargetInfo::ConstraintInfo, 4> OutputConstraintInfos;
    154 
    155   // The parser verifies that there is a string literal here.
    156   assert(AsmString->isAscii());
    157 
    158   // If we're compiling CUDA file and function attributes indicate that it's not
    159   // for this compilation side, skip all the checks.
    160   if (!DeclAttrsMatchCUDAMode(getLangOpts(), getCurFunctionDecl())) {
    161     GCCAsmStmt *NS = new (Context) GCCAsmStmt(
    162         Context, AsmLoc, IsSimple, IsVolatile, NumOutputs, NumInputs, Names,
    163         Constraints, Exprs.data(), AsmString, NumClobbers, Clobbers, RParenLoc);
    164     return NS;
    165   }
    166 
    167   for (unsigned i = 0; i != NumOutputs; i++) {
    168     StringLiteral *Literal = Constraints[i];
    169     assert(Literal->isAscii());
    170 
    171     StringRef OutputName;
    172     if (Names[i])
    173       OutputName = Names[i]->getName();
    174 
    175     TargetInfo::ConstraintInfo Info(Literal->getString(), OutputName);
    176     if (!Context.getTargetInfo().validateOutputConstraint(Info))
    177       return StmtError(Diag(Literal->getLocStart(),
    178                             diag::err_asm_invalid_output_constraint)
    179                        << Info.getConstraintStr());
    180 
    181     ExprResult ER = CheckPlaceholderExpr(Exprs[i]);
    182     if (ER.isInvalid())
    183       return StmtError();
    184     Exprs[i] = ER.get();
    185 
    186     // Check that the output exprs are valid lvalues.
    187     Expr *OutputExpr = Exprs[i];
    188 
    189     // Referring to parameters is not allowed in naked functions.
    190     if (CheckNakedParmReference(OutputExpr, *this))
    191       return StmtError();
    192 
    193     // Check that the output expression is compatible with memory constraint.
    194     if (Info.allowsMemory() &&
    195         checkExprMemoryConstraintCompat(*this, OutputExpr, Info, false))
    196       return StmtError();
    197 
    198     OutputConstraintInfos.push_back(Info);
    199 
    200     // If this is dependent, just continue.
    201     if (OutputExpr->isTypeDependent())
    202       continue;
    203 
    204     Expr::isModifiableLvalueResult IsLV =
    205         OutputExpr->isModifiableLvalue(Context, /*Loc=*/nullptr);
    206     switch (IsLV) {
    207     case Expr::MLV_Valid:
    208       // Cool, this is an lvalue.
    209       break;
    210     case Expr::MLV_ArrayType:
    211       // This is OK too.
    212       break;
    213     case Expr::MLV_LValueCast: {
    214       const Expr *LVal = OutputExpr->IgnoreParenNoopCasts(Context);
    215       if (!getLangOpts().HeinousExtensions) {
    216         Diag(LVal->getLocStart(), diag::err_invalid_asm_cast_lvalue)
    217             << OutputExpr->getSourceRange();
    218       } else {
    219         Diag(LVal->getLocStart(), diag::warn_invalid_asm_cast_lvalue)
    220             << OutputExpr->getSourceRange();
    221       }
    222       // Accept, even if we emitted an error diagnostic.
    223       break;
    224     }
    225     case Expr::MLV_IncompleteType:
    226     case Expr::MLV_IncompleteVoidType:
    227       if (RequireCompleteType(OutputExpr->getLocStart(), Exprs[i]->getType(),
    228                               diag::err_dereference_incomplete_type))
    229         return StmtError();
    230     default:
    231       return StmtError(Diag(OutputExpr->getLocStart(),
    232                             diag::err_asm_invalid_lvalue_in_output)
    233                        << OutputExpr->getSourceRange());
    234     }
    235 
    236     unsigned Size = Context.getTypeSize(OutputExpr->getType());
    237     if (!Context.getTargetInfo().validateOutputSize(Literal->getString(),
    238                                                     Size))
    239       return StmtError(Diag(OutputExpr->getLocStart(),
    240                             diag::err_asm_invalid_output_size)
    241                        << Info.getConstraintStr());
    242   }
    243 
    244   SmallVector<TargetInfo::ConstraintInfo, 4> InputConstraintInfos;
    245 
    246   for (unsigned i = NumOutputs, e = NumOutputs + NumInputs; i != e; i++) {
    247     StringLiteral *Literal = Constraints[i];
    248     assert(Literal->isAscii());
    249 
    250     StringRef InputName;
    251     if (Names[i])
    252       InputName = Names[i]->getName();
    253 
    254     TargetInfo::ConstraintInfo Info(Literal->getString(), InputName);
    255     if (!Context.getTargetInfo().validateInputConstraint(OutputConstraintInfos,
    256                                                          Info)) {
    257       return StmtError(Diag(Literal->getLocStart(),
    258                             diag::err_asm_invalid_input_constraint)
    259                        << Info.getConstraintStr());
    260     }
    261 
    262     ExprResult ER = CheckPlaceholderExpr(Exprs[i]);
    263     if (ER.isInvalid())
    264       return StmtError();
    265     Exprs[i] = ER.get();
    266 
    267     Expr *InputExpr = Exprs[i];
    268 
    269     // Referring to parameters is not allowed in naked functions.
    270     if (CheckNakedParmReference(InputExpr, *this))
    271       return StmtError();
    272 
    273     // Check that the input expression is compatible with memory constraint.
    274     if (Info.allowsMemory() &&
    275         checkExprMemoryConstraintCompat(*this, InputExpr, Info, true))
    276       return StmtError();
    277 
    278     // Only allow void types for memory constraints.
    279     if (Info.allowsMemory() && !Info.allowsRegister()) {
    280       if (CheckAsmLValue(InputExpr, *this))
    281         return StmtError(Diag(InputExpr->getLocStart(),
    282                               diag::err_asm_invalid_lvalue_in_input)
    283                          << Info.getConstraintStr()
    284                          << InputExpr->getSourceRange());
    285     } else if (Info.requiresImmediateConstant() && !Info.allowsRegister()) {
    286       if (!InputExpr->isValueDependent()) {
    287         llvm::APSInt Result;
    288         if (!InputExpr->EvaluateAsInt(Result, Context))
    289            return StmtError(
    290                Diag(InputExpr->getLocStart(), diag::err_asm_immediate_expected)
    291                 << Info.getConstraintStr() << InputExpr->getSourceRange());
    292          if (!Info.isValidAsmImmediate(Result))
    293            return StmtError(Diag(InputExpr->getLocStart(),
    294                                  diag::err_invalid_asm_value_for_constraint)
    295                             << Result.toString(10) << Info.getConstraintStr()
    296                             << InputExpr->getSourceRange());
    297       }
    298 
    299     } else {
    300       ExprResult Result = DefaultFunctionArrayLvalueConversion(Exprs[i]);
    301       if (Result.isInvalid())
    302         return StmtError();
    303 
    304       Exprs[i] = Result.get();
    305     }
    306 
    307     if (Info.allowsRegister()) {
    308       if (InputExpr->getType()->isVoidType()) {
    309         return StmtError(Diag(InputExpr->getLocStart(),
    310                               diag::err_asm_invalid_type_in_input)
    311           << InputExpr->getType() << Info.getConstraintStr()
    312           << InputExpr->getSourceRange());
    313       }
    314     }
    315 
    316     InputConstraintInfos.push_back(Info);
    317 
    318     const Type *Ty = Exprs[i]->getType().getTypePtr();
    319     if (Ty->isDependentType())
    320       continue;
    321 
    322     if (!Ty->isVoidType() || !Info.allowsMemory())
    323       if (RequireCompleteType(InputExpr->getLocStart(), Exprs[i]->getType(),
    324                               diag::err_dereference_incomplete_type))
    325         return StmtError();
    326 
    327     unsigned Size = Context.getTypeSize(Ty);
    328     if (!Context.getTargetInfo().validateInputSize(Literal->getString(),
    329                                                    Size))
    330       return StmtError(Diag(InputExpr->getLocStart(),
    331                             diag::err_asm_invalid_input_size)
    332                        << Info.getConstraintStr());
    333   }
    334 
    335   // Check that the clobbers are valid.
    336   for (unsigned i = 0; i != NumClobbers; i++) {
    337     StringLiteral *Literal = Clobbers[i];
    338     assert(Literal->isAscii());
    339 
    340     StringRef Clobber = Literal->getString();
    341 
    342     if (!Context.getTargetInfo().isValidClobber(Clobber))
    343       return StmtError(Diag(Literal->getLocStart(),
    344                   diag::err_asm_unknown_register_name) << Clobber);
    345   }
    346 
    347   GCCAsmStmt *NS =
    348     new (Context) GCCAsmStmt(Context, AsmLoc, IsSimple, IsVolatile, NumOutputs,
    349                              NumInputs, Names, Constraints, Exprs.data(),
    350                              AsmString, NumClobbers, Clobbers, RParenLoc);
    351   // Validate the asm string, ensuring it makes sense given the operands we
    352   // have.
    353   SmallVector<GCCAsmStmt::AsmStringPiece, 8> Pieces;
    354   unsigned DiagOffs;
    355   if (unsigned DiagID = NS->AnalyzeAsmString(Pieces, Context, DiagOffs)) {
    356     Diag(getLocationOfStringLiteralByte(AsmString, DiagOffs), DiagID)
    357            << AsmString->getSourceRange();
    358     return StmtError();
    359   }
    360 
    361   // Validate constraints and modifiers.
    362   for (unsigned i = 0, e = Pieces.size(); i != e; ++i) {
    363     GCCAsmStmt::AsmStringPiece &Piece = Pieces[i];
    364     if (!Piece.isOperand()) continue;
    365 
    366     // Look for the correct constraint index.
    367     unsigned ConstraintIdx = Piece.getOperandNo();
    368     unsigned NumOperands = NS->getNumOutputs() + NS->getNumInputs();
    369 
    370     // Look for the (ConstraintIdx - NumOperands + 1)th constraint with
    371     // modifier '+'.
    372     if (ConstraintIdx >= NumOperands) {
    373       unsigned I = 0, E = NS->getNumOutputs();
    374 
    375       for (unsigned Cnt = ConstraintIdx - NumOperands; I != E; ++I)
    376         if (OutputConstraintInfos[I].isReadWrite() && Cnt-- == 0) {
    377           ConstraintIdx = I;
    378           break;
    379         }
    380 
    381       assert(I != E && "Invalid operand number should have been caught in "
    382                        " AnalyzeAsmString");
    383     }
    384 
    385     // Now that we have the right indexes go ahead and check.
    386     StringLiteral *Literal = Constraints[ConstraintIdx];
    387     const Type *Ty = Exprs[ConstraintIdx]->getType().getTypePtr();
    388     if (Ty->isDependentType() || Ty->isIncompleteType())
    389       continue;
    390 
    391     unsigned Size = Context.getTypeSize(Ty);
    392     std::string SuggestedModifier;
    393     if (!Context.getTargetInfo().validateConstraintModifier(
    394             Literal->getString(), Piece.getModifier(), Size,
    395             SuggestedModifier)) {
    396       Diag(Exprs[ConstraintIdx]->getLocStart(),
    397            diag::warn_asm_mismatched_size_modifier);
    398 
    399       if (!SuggestedModifier.empty()) {
    400         auto B = Diag(Piece.getRange().getBegin(),
    401                       diag::note_asm_missing_constraint_modifier)
    402                  << SuggestedModifier;
    403         SuggestedModifier = "%" + SuggestedModifier + Piece.getString();
    404         B.AddFixItHint(FixItHint::CreateReplacement(Piece.getRange(),
    405                                                     SuggestedModifier));
    406       }
    407     }
    408   }
    409 
    410   // Validate tied input operands for type mismatches.
    411   unsigned NumAlternatives = ~0U;
    412   for (unsigned i = 0, e = OutputConstraintInfos.size(); i != e; ++i) {
    413     TargetInfo::ConstraintInfo &Info = OutputConstraintInfos[i];
    414     StringRef ConstraintStr = Info.getConstraintStr();
    415     unsigned AltCount = ConstraintStr.count(',') + 1;
    416     if (NumAlternatives == ~0U)
    417       NumAlternatives = AltCount;
    418     else if (NumAlternatives != AltCount)
    419       return StmtError(Diag(NS->getOutputExpr(i)->getLocStart(),
    420                             diag::err_asm_unexpected_constraint_alternatives)
    421                        << NumAlternatives << AltCount);
    422   }
    423   SmallVector<size_t, 4> InputMatchedToOutput(OutputConstraintInfos.size(),
    424                                               ~0U);
    425   for (unsigned i = 0, e = InputConstraintInfos.size(); i != e; ++i) {
    426     TargetInfo::ConstraintInfo &Info = InputConstraintInfos[i];
    427     StringRef ConstraintStr = Info.getConstraintStr();
    428     unsigned AltCount = ConstraintStr.count(',') + 1;
    429     if (NumAlternatives == ~0U)
    430       NumAlternatives = AltCount;
    431     else if (NumAlternatives != AltCount)
    432       return StmtError(Diag(NS->getInputExpr(i)->getLocStart(),
    433                             diag::err_asm_unexpected_constraint_alternatives)
    434                        << NumAlternatives << AltCount);
    435 
    436     // If this is a tied constraint, verify that the output and input have
    437     // either exactly the same type, or that they are int/ptr operands with the
    438     // same size (int/long, int*/long, are ok etc).
    439     if (!Info.hasTiedOperand()) continue;
    440 
    441     unsigned TiedTo = Info.getTiedOperand();
    442     unsigned InputOpNo = i+NumOutputs;
    443     Expr *OutputExpr = Exprs[TiedTo];
    444     Expr *InputExpr = Exprs[InputOpNo];
    445 
    446     // Make sure no more than one input constraint matches each output.
    447     assert(TiedTo < InputMatchedToOutput.size() && "TiedTo value out of range");
    448     if (InputMatchedToOutput[TiedTo] != ~0U) {
    449       Diag(NS->getInputExpr(i)->getLocStart(),
    450            diag::err_asm_input_duplicate_match)
    451           << TiedTo;
    452       Diag(NS->getInputExpr(InputMatchedToOutput[TiedTo])->getLocStart(),
    453            diag::note_asm_input_duplicate_first)
    454           << TiedTo;
    455       return StmtError();
    456     }
    457     InputMatchedToOutput[TiedTo] = i;
    458 
    459     if (OutputExpr->isTypeDependent() || InputExpr->isTypeDependent())
    460       continue;
    461 
    462     QualType InTy = InputExpr->getType();
    463     QualType OutTy = OutputExpr->getType();
    464     if (Context.hasSameType(InTy, OutTy))
    465       continue;  // All types can be tied to themselves.
    466 
    467     // Decide if the input and output are in the same domain (integer/ptr or
    468     // floating point.
    469     enum AsmDomain {
    470       AD_Int, AD_FP, AD_Other
    471     } InputDomain, OutputDomain;
    472 
    473     if (InTy->isIntegerType() || InTy->isPointerType())
    474       InputDomain = AD_Int;
    475     else if (InTy->isRealFloatingType())
    476       InputDomain = AD_FP;
    477     else
    478       InputDomain = AD_Other;
    479 
    480     if (OutTy->isIntegerType() || OutTy->isPointerType())
    481       OutputDomain = AD_Int;
    482     else if (OutTy->isRealFloatingType())
    483       OutputDomain = AD_FP;
    484     else
    485       OutputDomain = AD_Other;
    486 
    487     // They are ok if they are the same size and in the same domain.  This
    488     // allows tying things like:
    489     //   void* to int*
    490     //   void* to int            if they are the same size.
    491     //   double to long double   if they are the same size.
    492     //
    493     uint64_t OutSize = Context.getTypeSize(OutTy);
    494     uint64_t InSize = Context.getTypeSize(InTy);
    495     if (OutSize == InSize && InputDomain == OutputDomain &&
    496         InputDomain != AD_Other)
    497       continue;
    498 
    499     // If the smaller input/output operand is not mentioned in the asm string,
    500     // then we can promote the smaller one to a larger input and the asm string
    501     // won't notice.
    502     bool SmallerValueMentioned = false;
    503 
    504     // If this is a reference to the input and if the input was the smaller
    505     // one, then we have to reject this asm.
    506     if (isOperandMentioned(InputOpNo, Pieces)) {
    507       // This is a use in the asm string of the smaller operand.  Since we
    508       // codegen this by promoting to a wider value, the asm will get printed
    509       // "wrong".
    510       SmallerValueMentioned |= InSize < OutSize;
    511     }
    512     if (isOperandMentioned(TiedTo, Pieces)) {
    513       // If this is a reference to the output, and if the output is the larger
    514       // value, then it's ok because we'll promote the input to the larger type.
    515       SmallerValueMentioned |= OutSize < InSize;
    516     }
    517 
    518     // If the smaller value wasn't mentioned in the asm string, and if the
    519     // output was a register, just extend the shorter one to the size of the
    520     // larger one.
    521     if (!SmallerValueMentioned && InputDomain != AD_Other &&
    522         OutputConstraintInfos[TiedTo].allowsRegister())
    523       continue;
    524 
    525     // Either both of the operands were mentioned or the smaller one was
    526     // mentioned.  One more special case that we'll allow: if the tied input is
    527     // integer, unmentioned, and is a constant, then we'll allow truncating it
    528     // down to the size of the destination.
    529     if (InputDomain == AD_Int && OutputDomain == AD_Int &&
    530         !isOperandMentioned(InputOpNo, Pieces) &&
    531         InputExpr->isEvaluatable(Context)) {
    532       CastKind castKind =
    533         (OutTy->isBooleanType() ? CK_IntegralToBoolean : CK_IntegralCast);
    534       InputExpr = ImpCastExprToType(InputExpr, OutTy, castKind).get();
    535       Exprs[InputOpNo] = InputExpr;
    536       NS->setInputExpr(i, InputExpr);
    537       continue;
    538     }
    539 
    540     Diag(InputExpr->getLocStart(),
    541          diag::err_asm_tying_incompatible_types)
    542       << InTy << OutTy << OutputExpr->getSourceRange()
    543       << InputExpr->getSourceRange();
    544     return StmtError();
    545   }
    546 
    547   return NS;
    548 }
    549 
    550 static void fillInlineAsmTypeInfo(const ASTContext &Context, QualType T,
    551                                   llvm::InlineAsmIdentifierInfo &Info) {
    552   // Compute the type size (and array length if applicable?).
    553   Info.Type = Info.Size = Context.getTypeSizeInChars(T).getQuantity();
    554   if (T->isArrayType()) {
    555     const ArrayType *ATy = Context.getAsArrayType(T);
    556     Info.Type = Context.getTypeSizeInChars(ATy->getElementType()).getQuantity();
    557     Info.Length = Info.Size / Info.Type;
    558   }
    559 }
    560 
    561 ExprResult Sema::LookupInlineAsmIdentifier(CXXScopeSpec &SS,
    562                                            SourceLocation TemplateKWLoc,
    563                                            UnqualifiedId &Id,
    564                                            llvm::InlineAsmIdentifierInfo &Info,
    565                                            bool IsUnevaluatedContext) {
    566   Info.clear();
    567 
    568   if (IsUnevaluatedContext)
    569     PushExpressionEvaluationContext(UnevaluatedAbstract,
    570                                     ReuseLambdaContextDecl);
    571 
    572   ExprResult Result = ActOnIdExpression(getCurScope(), SS, TemplateKWLoc, Id,
    573                                         /*trailing lparen*/ false,
    574                                         /*is & operand*/ false,
    575                                         /*CorrectionCandidateCallback=*/nullptr,
    576                                         /*IsInlineAsmIdentifier=*/ true);
    577 
    578   if (IsUnevaluatedContext)
    579     PopExpressionEvaluationContext();
    580 
    581   if (!Result.isUsable()) return Result;
    582 
    583   Result = CheckPlaceholderExpr(Result.get());
    584   if (!Result.isUsable()) return Result;
    585 
    586   // Referring to parameters is not allowed in naked functions.
    587   if (CheckNakedParmReference(Result.get(), *this))
    588     return ExprError();
    589 
    590   QualType T = Result.get()->getType();
    591 
    592   if (T->isDependentType()) {
    593     return Result;
    594   }
    595 
    596   // Any sort of function type is fine.
    597   if (T->isFunctionType()) {
    598     return Result;
    599   }
    600 
    601   // Otherwise, it needs to be a complete type.
    602   if (RequireCompleteExprType(Result.get(), diag::err_asm_incomplete_type)) {
    603     return ExprError();
    604   }
    605 
    606   fillInlineAsmTypeInfo(Context, T, Info);
    607 
    608   // We can work with the expression as long as it's not an r-value.
    609   if (!Result.get()->isRValue())
    610     Info.IsVarDecl = true;
    611 
    612   return Result;
    613 }
    614 
    615 bool Sema::LookupInlineAsmField(StringRef Base, StringRef Member,
    616                                 unsigned &Offset, SourceLocation AsmLoc) {
    617   Offset = 0;
    618   SmallVector<StringRef, 2> Members;
    619   Member.split(Members, ".");
    620 
    621   LookupResult BaseResult(*this, &Context.Idents.get(Base), SourceLocation(),
    622                           LookupOrdinaryName);
    623 
    624   if (!LookupName(BaseResult, getCurScope()))
    625     return true;
    626 
    627   if(!BaseResult.isSingleResult())
    628     return true;
    629   NamedDecl *FoundDecl = BaseResult.getFoundDecl();
    630   for (StringRef NextMember : Members) {
    631     const RecordType *RT = nullptr;
    632     if (VarDecl *VD = dyn_cast<VarDecl>(FoundDecl))
    633       RT = VD->getType()->getAs<RecordType>();
    634     else if (TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(FoundDecl)) {
    635       MarkAnyDeclReferenced(TD->getLocation(), TD, /*OdrUse=*/false);
    636       RT = TD->getUnderlyingType()->getAs<RecordType>();
    637     } else if (TypeDecl *TD = dyn_cast<TypeDecl>(FoundDecl))
    638       RT = TD->getTypeForDecl()->getAs<RecordType>();
    639     else if (FieldDecl *TD = dyn_cast<FieldDecl>(FoundDecl))
    640       RT = TD->getType()->getAs<RecordType>();
    641     if (!RT)
    642       return true;
    643 
    644     if (RequireCompleteType(AsmLoc, QualType(RT, 0),
    645                             diag::err_asm_incomplete_type))
    646       return true;
    647 
    648     LookupResult FieldResult(*this, &Context.Idents.get(NextMember),
    649                              SourceLocation(), LookupMemberName);
    650 
    651     if (!LookupQualifiedName(FieldResult, RT->getDecl()))
    652       return true;
    653 
    654     if (!FieldResult.isSingleResult())
    655       return true;
    656     FoundDecl = FieldResult.getFoundDecl();
    657 
    658     // FIXME: Handle IndirectFieldDecl?
    659     FieldDecl *FD = dyn_cast<FieldDecl>(FoundDecl);
    660     if (!FD)
    661       return true;
    662 
    663     const ASTRecordLayout &RL = Context.getASTRecordLayout(RT->getDecl());
    664     unsigned i = FD->getFieldIndex();
    665     CharUnits Result = Context.toCharUnitsFromBits(RL.getFieldOffset(i));
    666     Offset += (unsigned)Result.getQuantity();
    667   }
    668 
    669   return false;
    670 }
    671 
    672 ExprResult
    673 Sema::LookupInlineAsmVarDeclField(Expr *E, StringRef Member,
    674                                   llvm::InlineAsmIdentifierInfo &Info,
    675                                   SourceLocation AsmLoc) {
    676   Info.clear();
    677 
    678   QualType T = E->getType();
    679   if (T->isDependentType()) {
    680     DeclarationNameInfo NameInfo;
    681     NameInfo.setLoc(AsmLoc);
    682     NameInfo.setName(&Context.Idents.get(Member));
    683     return CXXDependentScopeMemberExpr::Create(
    684         Context, E, T, /*IsArrow=*/false, AsmLoc, NestedNameSpecifierLoc(),
    685         SourceLocation(),
    686         /*FirstQualifierInScope=*/nullptr, NameInfo, /*TemplateArgs=*/nullptr);
    687   }
    688 
    689   const RecordType *RT = T->getAs<RecordType>();
    690   // FIXME: Diagnose this as field access into a scalar type.
    691   if (!RT)
    692     return ExprResult();
    693 
    694   LookupResult FieldResult(*this, &Context.Idents.get(Member), AsmLoc,
    695                            LookupMemberName);
    696 
    697   if (!LookupQualifiedName(FieldResult, RT->getDecl()))
    698     return ExprResult();
    699 
    700   // Only normal and indirect field results will work.
    701   ValueDecl *FD = dyn_cast<FieldDecl>(FieldResult.getFoundDecl());
    702   if (!FD)
    703     FD = dyn_cast<IndirectFieldDecl>(FieldResult.getFoundDecl());
    704   if (!FD)
    705     return ExprResult();
    706 
    707   // Make an Expr to thread through OpDecl.
    708   ExprResult Result = BuildMemberReferenceExpr(
    709       E, E->getType(), AsmLoc, /*IsArrow=*/false, CXXScopeSpec(),
    710       SourceLocation(), nullptr, FieldResult, nullptr, nullptr);
    711   if (Result.isInvalid())
    712     return Result;
    713   Info.OpDecl = Result.get();
    714 
    715   fillInlineAsmTypeInfo(Context, Result.get()->getType(), Info);
    716 
    717   // Fields are "variables" as far as inline assembly is concerned.
    718   Info.IsVarDecl = true;
    719 
    720   return Result;
    721 }
    722 
    723 StmtResult Sema::ActOnMSAsmStmt(SourceLocation AsmLoc, SourceLocation LBraceLoc,
    724                                 ArrayRef<Token> AsmToks,
    725                                 StringRef AsmString,
    726                                 unsigned NumOutputs, unsigned NumInputs,
    727                                 ArrayRef<StringRef> Constraints,
    728                                 ArrayRef<StringRef> Clobbers,
    729                                 ArrayRef<Expr*> Exprs,
    730                                 SourceLocation EndLoc) {
    731   bool IsSimple = (NumOutputs != 0 || NumInputs != 0);
    732   getCurFunction()->setHasBranchProtectedScope();
    733   MSAsmStmt *NS =
    734     new (Context) MSAsmStmt(Context, AsmLoc, LBraceLoc, IsSimple,
    735                             /*IsVolatile*/ true, AsmToks, NumOutputs, NumInputs,
    736                             Constraints, Exprs, AsmString,
    737                             Clobbers, EndLoc);
    738   return NS;
    739 }
    740 
    741 LabelDecl *Sema::GetOrCreateMSAsmLabel(StringRef ExternalLabelName,
    742                                        SourceLocation Location,
    743                                        bool AlwaysCreate) {
    744   LabelDecl* Label = LookupOrCreateLabel(PP.getIdentifierInfo(ExternalLabelName),
    745                                          Location);
    746 
    747   if (Label->isMSAsmLabel()) {
    748     // If we have previously created this label implicitly, mark it as used.
    749     Label->markUsed(Context);
    750   } else {
    751     // Otherwise, insert it, but only resolve it if we have seen the label itself.
    752     std::string InternalName;
    753     llvm::raw_string_ostream OS(InternalName);
    754     // Create an internal name for the label.  The name should not be a valid mangled
    755     // name, and should be unique.  We use a dot to make the name an invalid mangled
    756     // name.
    757     OS << "__MSASMLABEL_." << MSAsmLabelNameCounter++ << "__";
    758     for (auto it = ExternalLabelName.begin(); it != ExternalLabelName.end();
    759          ++it) {
    760       OS << *it;
    761       if (*it == '$') {
    762         // We escape '$' in asm strings by replacing it with "$$"
    763         OS << '$';
    764       }
    765     }
    766     Label->setMSAsmLabel(OS.str());
    767   }
    768   if (AlwaysCreate) {
    769     // The label might have been created implicitly from a previously encountered
    770     // goto statement.  So, for both newly created and looked up labels, we mark
    771     // them as resolved.
    772     Label->setMSAsmLabelResolved();
    773   }
    774   // Adjust their location for being able to generate accurate diagnostics.
    775   Label->setLocation(Location);
    776 
    777   return Label;
    778 }
    779