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/RecordLayout.h"
16#include "clang/AST/TypeLoc.h"
17#include "clang/Basic/TargetInfo.h"
18#include "clang/Sema/Initialization.h"
19#include "clang/Sema/Lookup.h"
20#include "clang/Sema/Scope.h"
21#include "clang/Sema/ScopeInfo.h"
22#include "llvm/ADT/ArrayRef.h"
23#include "llvm/ADT/BitVector.h"
24#include "llvm/MC/MCParser/MCAsmParser.h"
25using namespace clang;
26using namespace sema;
27
28/// CheckAsmLValue - GNU C has an extremely ugly extension whereby they silently
29/// ignore "noop" casts in places where an lvalue is required by an inline asm.
30/// We emulate this behavior when -fheinous-gnu-extensions is specified, but
31/// provide a strong guidance to not use it.
32///
33/// This method checks to see if the argument is an acceptable l-value and
34/// returns false if it is a case we can handle.
35static bool CheckAsmLValue(const Expr *E, Sema &S) {
36  // Type dependent expressions will be checked during instantiation.
37  if (E->isTypeDependent())
38    return false;
39
40  if (E->isLValue())
41    return false;  // Cool, this is an lvalue.
42
43  // Okay, this is not an lvalue, but perhaps it is the result of a cast that we
44  // are supposed to allow.
45  const Expr *E2 = E->IgnoreParenNoopCasts(S.Context);
46  if (E != E2 && E2->isLValue()) {
47    if (!S.getLangOpts().HeinousExtensions)
48      S.Diag(E2->getLocStart(), diag::err_invalid_asm_cast_lvalue)
49        << E->getSourceRange();
50    else
51      S.Diag(E2->getLocStart(), diag::warn_invalid_asm_cast_lvalue)
52        << E->getSourceRange();
53    // Accept, even if we emitted an error diagnostic.
54    return false;
55  }
56
57  // None of the above, just randomly invalid non-lvalue.
58  return true;
59}
60
61/// isOperandMentioned - Return true if the specified operand # is mentioned
62/// anywhere in the decomposed asm string.
63static bool isOperandMentioned(unsigned OpNo,
64                         ArrayRef<GCCAsmStmt::AsmStringPiece> AsmStrPieces) {
65  for (unsigned p = 0, e = AsmStrPieces.size(); p != e; ++p) {
66    const GCCAsmStmt::AsmStringPiece &Piece = AsmStrPieces[p];
67    if (!Piece.isOperand()) continue;
68
69    // If this is a reference to the input and if the input was the smaller
70    // one, then we have to reject this asm.
71    if (Piece.getOperandNo() == OpNo)
72      return true;
73  }
74  return false;
75}
76
77StmtResult Sema::ActOnGCCAsmStmt(SourceLocation AsmLoc, bool IsSimple,
78                                 bool IsVolatile, unsigned NumOutputs,
79                                 unsigned NumInputs, IdentifierInfo **Names,
80                                 MultiExprArg constraints, MultiExprArg Exprs,
81                                 Expr *asmString, MultiExprArg clobbers,
82                                 SourceLocation RParenLoc) {
83  unsigned NumClobbers = clobbers.size();
84  StringLiteral **Constraints =
85    reinterpret_cast<StringLiteral**>(constraints.data());
86  StringLiteral *AsmString = cast<StringLiteral>(asmString);
87  StringLiteral **Clobbers = reinterpret_cast<StringLiteral**>(clobbers.data());
88
89  SmallVector<TargetInfo::ConstraintInfo, 4> OutputConstraintInfos;
90
91  // The parser verifies that there is a string literal here.
92  if (!AsmString->isAscii())
93    return StmtError(Diag(AsmString->getLocStart(),diag::err_asm_wide_character)
94      << AsmString->getSourceRange());
95
96  for (unsigned i = 0; i != NumOutputs; i++) {
97    StringLiteral *Literal = Constraints[i];
98    if (!Literal->isAscii())
99      return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
100        << Literal->getSourceRange());
101
102    StringRef OutputName;
103    if (Names[i])
104      OutputName = Names[i]->getName();
105
106    TargetInfo::ConstraintInfo Info(Literal->getString(), OutputName);
107    if (!Context.getTargetInfo().validateOutputConstraint(Info))
108      return StmtError(Diag(Literal->getLocStart(),
109                            diag::err_asm_invalid_output_constraint)
110                       << Info.getConstraintStr());
111
112    // Check that the output exprs are valid lvalues.
113    Expr *OutputExpr = Exprs[i];
114    if (CheckAsmLValue(OutputExpr, *this))
115      return StmtError(Diag(OutputExpr->getLocStart(),
116                            diag::err_asm_invalid_lvalue_in_output)
117                       << OutputExpr->getSourceRange());
118
119    if (RequireCompleteType(OutputExpr->getLocStart(), Exprs[i]->getType(),
120                            diag::err_dereference_incomplete_type))
121      return StmtError();
122
123    OutputConstraintInfos.push_back(Info);
124  }
125
126  SmallVector<TargetInfo::ConstraintInfo, 4> InputConstraintInfos;
127
128  for (unsigned i = NumOutputs, e = NumOutputs + NumInputs; i != e; i++) {
129    StringLiteral *Literal = Constraints[i];
130    if (!Literal->isAscii())
131      return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
132        << Literal->getSourceRange());
133
134    StringRef InputName;
135    if (Names[i])
136      InputName = Names[i]->getName();
137
138    TargetInfo::ConstraintInfo Info(Literal->getString(), InputName);
139    if (!Context.getTargetInfo().validateInputConstraint(OutputConstraintInfos.data(),
140                                                NumOutputs, Info)) {
141      return StmtError(Diag(Literal->getLocStart(),
142                            diag::err_asm_invalid_input_constraint)
143                       << Info.getConstraintStr());
144    }
145
146    Expr *InputExpr = Exprs[i];
147
148    // Only allow void types for memory constraints.
149    if (Info.allowsMemory() && !Info.allowsRegister()) {
150      if (CheckAsmLValue(InputExpr, *this))
151        return StmtError(Diag(InputExpr->getLocStart(),
152                              diag::err_asm_invalid_lvalue_in_input)
153                         << Info.getConstraintStr()
154                         << InputExpr->getSourceRange());
155    }
156
157    if (Info.allowsRegister()) {
158      if (InputExpr->getType()->isVoidType()) {
159        return StmtError(Diag(InputExpr->getLocStart(),
160                              diag::err_asm_invalid_type_in_input)
161          << InputExpr->getType() << Info.getConstraintStr()
162          << InputExpr->getSourceRange());
163      }
164    }
165
166    ExprResult Result = DefaultFunctionArrayLvalueConversion(Exprs[i]);
167    if (Result.isInvalid())
168      return StmtError();
169
170    Exprs[i] = Result.get();
171    InputConstraintInfos.push_back(Info);
172
173    const Type *Ty = Exprs[i]->getType().getTypePtr();
174    if (Ty->isDependentType())
175      continue;
176
177    if (!Ty->isVoidType() || !Info.allowsMemory())
178      if (RequireCompleteType(InputExpr->getLocStart(), Exprs[i]->getType(),
179                              diag::err_dereference_incomplete_type))
180        return StmtError();
181
182    unsigned Size = Context.getTypeSize(Ty);
183    if (!Context.getTargetInfo().validateInputSize(Literal->getString(),
184                                                   Size))
185      return StmtError(Diag(InputExpr->getLocStart(),
186                            diag::err_asm_invalid_input_size)
187                       << Info.getConstraintStr());
188  }
189
190  // Check that the clobbers are valid.
191  for (unsigned i = 0; i != NumClobbers; i++) {
192    StringLiteral *Literal = Clobbers[i];
193    if (!Literal->isAscii())
194      return StmtError(Diag(Literal->getLocStart(),diag::err_asm_wide_character)
195        << Literal->getSourceRange());
196
197    StringRef Clobber = Literal->getString();
198
199    if (!Context.getTargetInfo().isValidClobber(Clobber))
200      return StmtError(Diag(Literal->getLocStart(),
201                  diag::err_asm_unknown_register_name) << Clobber);
202  }
203
204  GCCAsmStmt *NS =
205    new (Context) GCCAsmStmt(Context, AsmLoc, IsSimple, IsVolatile, NumOutputs,
206                             NumInputs, Names, Constraints, Exprs.data(),
207                             AsmString, NumClobbers, Clobbers, RParenLoc);
208  // Validate the asm string, ensuring it makes sense given the operands we
209  // have.
210  SmallVector<GCCAsmStmt::AsmStringPiece, 8> Pieces;
211  unsigned DiagOffs;
212  if (unsigned DiagID = NS->AnalyzeAsmString(Pieces, Context, DiagOffs)) {
213    Diag(getLocationOfStringLiteralByte(AsmString, DiagOffs), DiagID)
214           << AsmString->getSourceRange();
215    return StmtError();
216  }
217
218  // Validate constraints and modifiers.
219  for (unsigned i = 0, e = Pieces.size(); i != e; ++i) {
220    GCCAsmStmt::AsmStringPiece &Piece = Pieces[i];
221    if (!Piece.isOperand()) continue;
222
223    // Look for the correct constraint index.
224    unsigned Idx = 0;
225    unsigned ConstraintIdx = 0;
226    for (unsigned i = 0, e = NS->getNumOutputs(); i != e; ++i, ++ConstraintIdx) {
227      TargetInfo::ConstraintInfo &Info = OutputConstraintInfos[i];
228      if (Idx == Piece.getOperandNo())
229        break;
230      ++Idx;
231
232      if (Info.isReadWrite()) {
233        if (Idx == Piece.getOperandNo())
234          break;
235        ++Idx;
236      }
237    }
238
239    for (unsigned i = 0, e = NS->getNumInputs(); i != e; ++i, ++ConstraintIdx) {
240      TargetInfo::ConstraintInfo &Info = InputConstraintInfos[i];
241      if (Idx == Piece.getOperandNo())
242        break;
243      ++Idx;
244
245      if (Info.isReadWrite()) {
246        if (Idx == Piece.getOperandNo())
247          break;
248        ++Idx;
249      }
250    }
251
252    // Now that we have the right indexes go ahead and check.
253    StringLiteral *Literal = Constraints[ConstraintIdx];
254    const Type *Ty = Exprs[ConstraintIdx]->getType().getTypePtr();
255    if (Ty->isDependentType() || Ty->isIncompleteType())
256      continue;
257
258    unsigned Size = Context.getTypeSize(Ty);
259    if (!Context.getTargetInfo()
260          .validateConstraintModifier(Literal->getString(), Piece.getModifier(),
261                                      Size))
262      Diag(Exprs[ConstraintIdx]->getLocStart(),
263           diag::warn_asm_mismatched_size_modifier);
264  }
265
266  // Validate tied input operands for type mismatches.
267  for (unsigned i = 0, e = InputConstraintInfos.size(); i != e; ++i) {
268    TargetInfo::ConstraintInfo &Info = InputConstraintInfos[i];
269
270    // If this is a tied constraint, verify that the output and input have
271    // either exactly the same type, or that they are int/ptr operands with the
272    // same size (int/long, int*/long, are ok etc).
273    if (!Info.hasTiedOperand()) continue;
274
275    unsigned TiedTo = Info.getTiedOperand();
276    unsigned InputOpNo = i+NumOutputs;
277    Expr *OutputExpr = Exprs[TiedTo];
278    Expr *InputExpr = Exprs[InputOpNo];
279
280    if (OutputExpr->isTypeDependent() || InputExpr->isTypeDependent())
281      continue;
282
283    QualType InTy = InputExpr->getType();
284    QualType OutTy = OutputExpr->getType();
285    if (Context.hasSameType(InTy, OutTy))
286      continue;  // All types can be tied to themselves.
287
288    // Decide if the input and output are in the same domain (integer/ptr or
289    // floating point.
290    enum AsmDomain {
291      AD_Int, AD_FP, AD_Other
292    } InputDomain, OutputDomain;
293
294    if (InTy->isIntegerType() || InTy->isPointerType())
295      InputDomain = AD_Int;
296    else if (InTy->isRealFloatingType())
297      InputDomain = AD_FP;
298    else
299      InputDomain = AD_Other;
300
301    if (OutTy->isIntegerType() || OutTy->isPointerType())
302      OutputDomain = AD_Int;
303    else if (OutTy->isRealFloatingType())
304      OutputDomain = AD_FP;
305    else
306      OutputDomain = AD_Other;
307
308    // They are ok if they are the same size and in the same domain.  This
309    // allows tying things like:
310    //   void* to int*
311    //   void* to int            if they are the same size.
312    //   double to long double   if they are the same size.
313    //
314    uint64_t OutSize = Context.getTypeSize(OutTy);
315    uint64_t InSize = Context.getTypeSize(InTy);
316    if (OutSize == InSize && InputDomain == OutputDomain &&
317        InputDomain != AD_Other)
318      continue;
319
320    // If the smaller input/output operand is not mentioned in the asm string,
321    // then we can promote the smaller one to a larger input and the asm string
322    // won't notice.
323    bool SmallerValueMentioned = false;
324
325    // If this is a reference to the input and if the input was the smaller
326    // one, then we have to reject this asm.
327    if (isOperandMentioned(InputOpNo, Pieces)) {
328      // This is a use in the asm string of the smaller operand.  Since we
329      // codegen this by promoting to a wider value, the asm will get printed
330      // "wrong".
331      SmallerValueMentioned |= InSize < OutSize;
332    }
333    if (isOperandMentioned(TiedTo, Pieces)) {
334      // If this is a reference to the output, and if the output is the larger
335      // value, then it's ok because we'll promote the input to the larger type.
336      SmallerValueMentioned |= OutSize < InSize;
337    }
338
339    // If the smaller value wasn't mentioned in the asm string, and if the
340    // output was a register, just extend the shorter one to the size of the
341    // larger one.
342    if (!SmallerValueMentioned && InputDomain != AD_Other &&
343        OutputConstraintInfos[TiedTo].allowsRegister())
344      continue;
345
346    // Either both of the operands were mentioned or the smaller one was
347    // mentioned.  One more special case that we'll allow: if the tied input is
348    // integer, unmentioned, and is a constant, then we'll allow truncating it
349    // down to the size of the destination.
350    if (InputDomain == AD_Int && OutputDomain == AD_Int &&
351        !isOperandMentioned(InputOpNo, Pieces) &&
352        InputExpr->isEvaluatable(Context)) {
353      CastKind castKind =
354        (OutTy->isBooleanType() ? CK_IntegralToBoolean : CK_IntegralCast);
355      InputExpr = ImpCastExprToType(InputExpr, OutTy, castKind).get();
356      Exprs[InputOpNo] = InputExpr;
357      NS->setInputExpr(i, InputExpr);
358      continue;
359    }
360
361    Diag(InputExpr->getLocStart(),
362         diag::err_asm_tying_incompatible_types)
363      << InTy << OutTy << OutputExpr->getSourceRange()
364      << InputExpr->getSourceRange();
365    return StmtError();
366  }
367
368  return NS;
369}
370
371ExprResult Sema::LookupInlineAsmIdentifier(CXXScopeSpec &SS,
372                                           SourceLocation TemplateKWLoc,
373                                           UnqualifiedId &Id,
374                                           llvm::InlineAsmIdentifierInfo &Info,
375                                           bool IsUnevaluatedContext) {
376  Info.clear();
377
378  if (IsUnevaluatedContext)
379    PushExpressionEvaluationContext(UnevaluatedAbstract,
380                                    ReuseLambdaContextDecl);
381
382  ExprResult Result = ActOnIdExpression(getCurScope(), SS, TemplateKWLoc, Id,
383                                        /*trailing lparen*/ false,
384                                        /*is & operand*/ false,
385                                        /*CorrectionCandidateCallback=*/nullptr,
386                                        /*IsInlineAsmIdentifier=*/ true);
387
388  if (IsUnevaluatedContext)
389    PopExpressionEvaluationContext();
390
391  if (!Result.isUsable()) return Result;
392
393  Result = CheckPlaceholderExpr(Result.get());
394  if (!Result.isUsable()) return Result;
395
396  QualType T = Result.get()->getType();
397
398  // For now, reject dependent types.
399  if (T->isDependentType()) {
400    Diag(Id.getLocStart(), diag::err_asm_incomplete_type) << T;
401    return ExprError();
402  }
403
404  // Any sort of function type is fine.
405  if (T->isFunctionType()) {
406    return Result;
407  }
408
409  // Otherwise, it needs to be a complete type.
410  if (RequireCompleteExprType(Result.get(), diag::err_asm_incomplete_type)) {
411    return ExprError();
412  }
413
414  // Compute the type size (and array length if applicable?).
415  Info.Type = Info.Size = Context.getTypeSizeInChars(T).getQuantity();
416  if (T->isArrayType()) {
417    const ArrayType *ATy = Context.getAsArrayType(T);
418    Info.Type = Context.getTypeSizeInChars(ATy->getElementType()).getQuantity();
419    Info.Length = Info.Size / Info.Type;
420  }
421
422  // We can work with the expression as long as it's not an r-value.
423  if (!Result.get()->isRValue())
424    Info.IsVarDecl = true;
425
426  return Result;
427}
428
429bool Sema::LookupInlineAsmField(StringRef Base, StringRef Member,
430                                unsigned &Offset, SourceLocation AsmLoc) {
431  Offset = 0;
432  LookupResult BaseResult(*this, &Context.Idents.get(Base), SourceLocation(),
433                          LookupOrdinaryName);
434
435  if (!LookupName(BaseResult, getCurScope()))
436    return true;
437
438  if (!BaseResult.isSingleResult())
439    return true;
440
441  const RecordType *RT = nullptr;
442  NamedDecl *FoundDecl = BaseResult.getFoundDecl();
443  if (VarDecl *VD = dyn_cast<VarDecl>(FoundDecl))
444    RT = VD->getType()->getAs<RecordType>();
445  else if (TypedefNameDecl *TD = dyn_cast<TypedefNameDecl>(FoundDecl))
446    RT = TD->getUnderlyingType()->getAs<RecordType>();
447  else if (TypeDecl *TD = dyn_cast<TypeDecl>(FoundDecl))
448    RT = TD->getTypeForDecl()->getAs<RecordType>();
449  if (!RT)
450    return true;
451
452  if (RequireCompleteType(AsmLoc, QualType(RT, 0), 0))
453    return true;
454
455  LookupResult FieldResult(*this, &Context.Idents.get(Member), SourceLocation(),
456                           LookupMemberName);
457
458  if (!LookupQualifiedName(FieldResult, RT->getDecl()))
459    return true;
460
461  // FIXME: Handle IndirectFieldDecl?
462  FieldDecl *FD = dyn_cast<FieldDecl>(FieldResult.getFoundDecl());
463  if (!FD)
464    return true;
465
466  const ASTRecordLayout &RL = Context.getASTRecordLayout(RT->getDecl());
467  unsigned i = FD->getFieldIndex();
468  CharUnits Result = Context.toCharUnitsFromBits(RL.getFieldOffset(i));
469  Offset = (unsigned)Result.getQuantity();
470
471  return false;
472}
473
474StmtResult Sema::ActOnMSAsmStmt(SourceLocation AsmLoc, SourceLocation LBraceLoc,
475                                ArrayRef<Token> AsmToks,
476                                StringRef AsmString,
477                                unsigned NumOutputs, unsigned NumInputs,
478                                ArrayRef<StringRef> Constraints,
479                                ArrayRef<StringRef> Clobbers,
480                                ArrayRef<Expr*> Exprs,
481                                SourceLocation EndLoc) {
482  bool IsSimple = (NumOutputs != 0 || NumInputs != 0);
483  MSAsmStmt *NS =
484    new (Context) MSAsmStmt(Context, AsmLoc, LBraceLoc, IsSimple,
485                            /*IsVolatile*/ true, AsmToks, NumOutputs, NumInputs,
486                            Constraints, Exprs, AsmString,
487                            Clobbers, EndLoc);
488  return NS;
489}
490