C1X: implement generic selections

As an extension, generic selection support has been added for all supported languages. The syntax is the same as for C1X. git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@129554 91177308-0d34-0410-b5e6-96231b3b80d8
2011-04-15 00:35:48 +00:00 · 2011-04-15 00:35:48 +00:00 · f111d93572
--- a/docs/LanguageExtensions.html
+++ b/docs/LanguageExtensions.html
@ -52,6 +52,7 @@ td {
 <li><a href="#checking_type_traits">Checks for Type Traits</a></li>
 <li><a href="#blocks">Blocks</a></li>
 <li><a href="#overloading-in-c">Function Overloading in C</a></li>
+<li><a href="#generic-selections">Generic Selections</a></li>
 <li><a href="#builtins">Builtin Functions</a>
  <ul>
  <li><a href="#__builtin_shufflevector">__builtin_shufflevector</a></li>
@ -603,6 +604,20 @@ caveats to this use of name mangling:</p>
 <p>Query for this feature with __has_feature(attribute_overloadable).</p>


+<!-- ======================================================================= -->
+<h2 id="generic-selections">Generic Selections</h2>
+<!-- ======================================================================= -->
+
+<p>The C1X generic selection expression is available in all languages
+supported by Clang.  The syntax is the same as that given in the C1X draft
+standard.</p>
+
+<p>In C, type compatibility is decided according to the rules given in the
+appropriate standard, but in C++, which lacks the type compatibility rules
+used in C, types are considered compatible only if they are equivalent.</p>
+
+<p>Query for this feature with __has_feature(generic_selections).</p>
+
 <!-- ======================================================================= -->
 <h2 id="builtins">Builtin Functions</h2>
 <!-- ======================================================================= -->
--- a/include/clang/AST/Expr.h
+++ b/include/clang/AST/Expr.h
@ -3679,6 +3679,118 @@ public:
 };


+/// \brief Represents a C1X generic selection.
+///
+/// A generic selection (C1X 6.5.1.1) contains an unevaluated controlling
+/// expression, followed by one or more generic associations.  Each generic
+/// association specifies a type name and an expression, or "default" and an
+/// expression (in which case it is known as a default generic association).
+/// The type and value of the generic selection are identical to those of its
+/// result expression, which is defined as the expression in the generic
+/// association with a type name that is compatible with the type of the
+/// controlling expression, or the expression in the default generic association
+/// if no types are compatible.  For example:
+///
+/// @code
+/// _Generic(X, double: 1, float: 2, default: 3)
+/// @endcode
+///
+/// The above expression evaluates to 1 if 1.0 is substituted for X, 2 if 1.0f
+/// or 3 if "hello".
+///
+/// As an extension, generic selections are allowed in C++, where the following
+/// additional semantics apply:
+///
+/// Any generic selection whose controlling expression is type-dependent or
+/// which names a dependent type in its association list is result-dependent,
+/// which means that the choice of result expression is dependent.
+/// Result-dependent generic associations are both type- and value-dependent.
+class GenericSelectionExpr : public Expr {
+  enum { CONTROLLING, END_EXPR };
+  TypeSourceInfo **AssocTypes;
+  Stmt **SubExprs;
+  unsigned NumAssocs, ResultIndex;
+  SourceLocation GenericLoc, DefaultLoc, RParenLoc;
+
+public:
+  GenericSelectionExpr(ASTContext &Context,
+                       SourceLocation GenericLoc, Expr *ControllingExpr,
+                       TypeSourceInfo **AssocTypes, Expr **AssocExprs,
+                       unsigned NumAssocs, SourceLocation DefaultLoc,
+                       SourceLocation RParenLoc,
+                       bool ContainsUnexpandedParameterPack,
+                       unsigned ResultIndex);
+
+  /// This constructor is used in the result-dependent case.
+  GenericSelectionExpr(ASTContext &Context,
+                       SourceLocation GenericLoc, Expr *ControllingExpr,
+                       TypeSourceInfo **AssocTypes, Expr **AssocExprs,
+                       unsigned NumAssocs, SourceLocation DefaultLoc,
+                       SourceLocation RParenLoc,
+                       bool ContainsUnexpandedParameterPack);
+
+  explicit GenericSelectionExpr(EmptyShell Empty)
+    : Expr(GenericSelectionExprClass, Empty) { }
+
+  unsigned getNumAssocs() const { return NumAssocs; }
+
+  SourceLocation getGenericLoc() const { return GenericLoc; }
+  SourceLocation getDefaultLoc() const { return DefaultLoc; }
+  SourceLocation getRParenLoc() const { return RParenLoc; }
+
+  const Expr *getAssocExpr(unsigned i) const {
+    return cast<Expr>(SubExprs[END_EXPR+i]);
+  }
+  Expr *getAssocExpr(unsigned i) { return cast<Expr>(SubExprs[END_EXPR+i]); }
+
+  const TypeSourceInfo *getAssocTypeSourceInfo(unsigned i) const {
+    return AssocTypes[i];
+  }
+  TypeSourceInfo *getAssocTypeSourceInfo(unsigned i) { return AssocTypes[i]; }
+
+  QualType getAssocType(unsigned i) const {
+    if (const TypeSourceInfo *TS = getAssocTypeSourceInfo(i))
+      return TS->getType();
+    else
+      return QualType();
+  }
+
+  const Expr *getControllingExpr() const {
+    return cast<Expr>(SubExprs[CONTROLLING]);
+  }
+  Expr *getControllingExpr() { return cast<Expr>(SubExprs[CONTROLLING]); }
+
+  /// Whether this generic selection is result-dependent.
+  bool isResultDependent() const { return ResultIndex == -1U; }
+
+  /// The zero-based index of the result expression's generic association in
+  /// the generic selection's association list.  Defined only if the
+  /// generic selection is not result-dependent.
+  unsigned getResultIndex() const {
+    assert(!isResultDependent() && "Generic selection is result-dependent");
+    return ResultIndex;
+  }
+
+  /// The generic selection's result expression.  Defined only if the
+  /// generic selection is not result-dependent.
+  const Expr *getResultExpr() const { return getAssocExpr(getResultIndex()); }
+  Expr *getResultExpr() { return getAssocExpr(getResultIndex()); }
+
+  SourceRange getSourceRange() const {
+    return SourceRange(GenericLoc, RParenLoc);
+  }
+  static bool classof(const Stmt *T) {
+    return T->getStmtClass() == GenericSelectionExprClass;
+  }
+  static bool classof(const GenericSelectionExpr *) { return true; }
+
+  child_range children() {
+    return child_range(SubExprs, SubExprs+END_EXPR+NumAssocs);
+  }
+
+  friend class ASTStmtReader;
+};
+
 //===----------------------------------------------------------------------===//
 // Clang Extensions
 //===----------------------------------------------------------------------===//
--- a/include/clang/AST/RecursiveASTVisitor.h
+++ b/include/clang/AST/RecursiveASTVisitor.h
@ -1777,6 +1777,22 @@ bool RecursiveASTVisitor<Derived>::TraverseInitListExpr(InitListExpr *S) {
  return true;
 }

+// GenericSelectionExpr is a special case because the types and expressions
+// are interleaved.  We also need to watch out for null types (default
+// generic associations).
+template<typename Derived>
+bool RecursiveASTVisitor<Derived>::
+TraverseGenericSelectionExpr(GenericSelectionExpr *S) {
+  TRY_TO(WalkUpFromGenericSelectionExpr(S));
+  TRY_TO(TraverseStmt(S->getControllingExpr()));
+  for (unsigned i = 0; i != S->getNumAssocs(); ++i) {
+    if (TypeSourceInfo *TS = S->getAssocTypeSourceInfo(i))
+      TRY_TO(TraverseTypeLoc(TS->getTypeLoc()));
+    TRY_TO(TraverseStmt(S->getAssocExpr(i)));
+  }
+  return true;
+}
+
 DEF_TRAVERSE_STMT(CXXScalarValueInitExpr, {
    // This is called for code like 'return T()' where T is a built-in
    // (i.e. non-class) type.
--- a/include/clang/Basic/DiagnosticParseKinds.td
+++ b/include/clang/Basic/DiagnosticParseKinds.td
@ -67,6 +67,13 @@ def ext_ms_enum_fixed_underlying_type : Extension<
  "enumeration types with a fixed underlying type are a Microsoft extension">, 
  InGroup<Microsoft>;

+def ext_c1x_generic_selection : Extension<
+  "generic selections are a C1X-specific feature">;
+def err_duplicate_default_assoc : Error<
+  "duplicate default generic association">;
+def note_previous_default_assoc : Note<
+  "previous default generic association is here">;
+
 def ext_gnu_indirect_goto : Extension<
  "use of GNU indirect-goto extension">, InGroup<GNU>;
 def ext_gnu_address_of_label : Extension<
--- a/include/clang/Basic/DiagnosticSemaKinds.td
+++ b/include/clang/Basic/DiagnosticSemaKinds.td
@ -3646,6 +3646,21 @@ def warn_stringcompare : Warning<
  "result of comparison against %select{a string literal|@encode}0 is "
  "unspecified (use strncmp instead)">;

+// Generic selections.
+def err_assoc_type_incomplete : Error<
+  "type %0 in generic association incomplete">;
+def err_assoc_type_nonobject : Error<
+  "type %0 in generic association not an object type">;
+def err_assoc_type_variably_modified : Error<
+  "type %0 in generic association is a variably modified type">;
+def err_assoc_compatible_types : Error<
+  "type %0 in generic association compatible with previously specified type %1">;
+def note_compat_assoc : Note<
+  "compatible type %0 specified here">;
+def err_generic_sel_no_match : Error<
+  "controlling expression type %0 not compatible with any generic association type">;
+def err_generic_sel_multi_match : Error<
+  "controlling expression type %0 compatible with %1 generic association types">;


 // Blocks
--- a/include/clang/Basic/StmtNodes.td
+++ b/include/clang/Basic/StmtNodes.td
@ -75,6 +75,7 @@ def DesignatedInitExpr : DStmt<Expr>;
 def ImplicitValueInitExpr : DStmt<Expr>;
 def ParenListExpr : DStmt<Expr>;
 def VAArgExpr : DStmt<Expr>;
+def GenericSelectionExpr : DStmt<Expr>;

 // GNU Extensions.
 def AddrLabelExpr : DStmt<Expr>;
--- a/include/clang/Basic/TokenKinds.def
+++ b/include/clang/Basic/TokenKinds.def
@ -238,6 +238,7 @@ KEYWORD(volatile                    , KEYALL)
 KEYWORD(while                       , KEYALL)
 KEYWORD(_Bool                       , KEYNOCXX)
 KEYWORD(_Complex                    , KEYALL)
+KEYWORD(_Generic                    , KEYALL)
 KEYWORD(_Imaginary                  , KEYALL)
 KEYWORD(__func__                    , KEYALL)

--- a/include/clang/Parse/Parser.h
+++ b/include/clang/Parse/Parser.h
@ -1101,6 +1101,8 @@ private:

  ExprResult ParseStringLiteralExpression();

+  ExprResult ParseGenericSelectionExpression();
+
  //===--------------------------------------------------------------------===//
  // C++ Expressions
  ExprResult ParseCXXIdExpression(bool isAddressOfOperand = false);
--- a/include/clang/Sema/Ownership.h
+++ b/include/clang/Sema/Ownership.h
@ -383,11 +383,18 @@ namespace clang {
    template<typename T> T **takeAs() { return reinterpret_cast<T**>(take()); }
  };

+  /// An opaque type for threading parsed type information through the
+  /// parser.
+  typedef OpaquePtr<QualType> ParsedType;
+  typedef UnionOpaquePtr<QualType> UnionParsedType;
+
  /// A SmallVector of statements, with stack size 32 (as that is the only one
  /// used.)
  typedef ASTOwningVector<Stmt*, 32> StmtVector;
  /// A SmallVector of expressions, with stack size 12 (the maximum used.)
  typedef ASTOwningVector<Expr*, 12> ExprVector;
+  /// A SmallVector of types.
+  typedef ASTOwningVector<ParsedType, 12> TypeVector;

  template <class T, unsigned N> inline
  ASTMultiPtr<T> move_arg(ASTOwningVector<T, N> &vec) {
@ -421,11 +428,6 @@ namespace clang {
    static const bool value = true;
  };

-  /// An opaque type for threading parsed type information through the
-  /// parser.
-  typedef OpaquePtr<QualType> ParsedType;
-  typedef UnionOpaquePtr<QualType> UnionParsedType;
-
  typedef ActionResult<Expr*> ExprResult;
  typedef ActionResult<Stmt*> StmtResult;
  typedef ActionResult<ParsedType> TypeResult;
@ -440,6 +442,7 @@ namespace clang {

  typedef ASTMultiPtr<Expr*> MultiExprArg;
  typedef ASTMultiPtr<Stmt*> MultiStmtArg;
+  typedef ASTMultiPtr<ParsedType> MultiTypeArg;
  typedef ASTMultiPtr<TemplateParameterList*> MultiTemplateParamsArg;

  inline ExprResult ExprError() { return ExprResult(true); }
--- a/include/clang/Sema/Sema.h
+++ b/include/clang/Sema/Sema.h
@ -2009,6 +2009,20 @@ public:
  /// fragments (e.g. "foo" "bar" L"baz").
  ExprResult ActOnStringLiteral(const Token *Toks, unsigned NumToks);

+  ExprResult ActOnGenericSelectionExpr(SourceLocation KeyLoc,
+                                       SourceLocation DefaultLoc,
+                                       SourceLocation RParenLoc,
+                                       Expr *ControllingExpr,
+                                       MultiTypeArg Types,
+                                       MultiExprArg Exprs);
+  ExprResult CreateGenericSelectionExpr(SourceLocation KeyLoc,
+                                        SourceLocation DefaultLoc,
+                                        SourceLocation RParenLoc,
+                                        Expr *ControllingExpr,
+                                        TypeSourceInfo **Types,
+                                        Expr **Exprs,
+                                        unsigned NumAssocs);
+
  // Binary/Unary Operators.  'Tok' is the token for the operator.
  ExprResult CreateBuiltinUnaryOp(SourceLocation OpLoc, UnaryOperatorKind Opc,
                                  Expr *InputArg);
--- a/include/clang/Serialization/ASTBitCodes.h
+++ b/include/clang/Serialization/ASTBitCodes.h
@ -878,6 +878,8 @@ namespace clang {
      EXPR_BLOCK,
      /// \brief A BlockDeclRef record.
      EXPR_BLOCK_DECL_REF,
+      /// \brief A GenericSelectionExpr record.
+      EXPR_GENERIC_SELECTION,
      
      // Objective-C

--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@ -35,18 +35,16 @@ using namespace clang;
 /// but also int expressions which are produced by things like comparisons in
 /// C.
 bool Expr::isKnownToHaveBooleanValue() const {
+  const Expr *E = IgnoreParens();
+
  // If this value has _Bool type, it is obvious 0/1.
-  if (getType()->isBooleanType()) return true;
+  if (E->getType()->isBooleanType()) return true;
  // If this is a non-scalar-integer type, we don't care enough to try. 
-  if (!getType()->isIntegralOrEnumerationType()) return false;
+  if (!E->getType()->isIntegralOrEnumerationType()) return false;
  
-  if (const ParenExpr *PE = dyn_cast<ParenExpr>(this))
-    return PE->getSubExpr()->isKnownToHaveBooleanValue();
-  
-  if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(this)) {
+  if (const UnaryOperator *UO = dyn_cast<UnaryOperator>(E)) {
    switch (UO->getOpcode()) {
    case UO_Plus:
-    case UO_Extension:
      return UO->getSubExpr()->isKnownToHaveBooleanValue();
    default:
      return false;
@ -55,10 +53,10 @@ bool Expr::isKnownToHaveBooleanValue() const {
  
  // Only look through implicit casts.  If the user writes
  // '(int) (a && b)' treat it as an arbitrary int.
-  if (const ImplicitCastExpr *CE = dyn_cast<ImplicitCastExpr>(this))
+  if (const ImplicitCastExpr *CE = dyn_cast<ImplicitCastExpr>(E))
    return CE->getSubExpr()->isKnownToHaveBooleanValue();
  
-  if (const BinaryOperator *BO = dyn_cast<BinaryOperator>(this)) {
+  if (const BinaryOperator *BO = dyn_cast<BinaryOperator>(E)) {
    switch (BO->getOpcode()) {
    default: return false;
    case BO_LT:   // Relational operators.
@ -84,7 +82,7 @@ bool Expr::isKnownToHaveBooleanValue() const {
    }
  }
  
-  if (const ConditionalOperator *CO = dyn_cast<ConditionalOperator>(this))
+  if (const ConditionalOperator *CO = dyn_cast<ConditionalOperator>(E))
    return CO->getTrueExpr()->isKnownToHaveBooleanValue() &&
           CO->getFalseExpr()->isKnownToHaveBooleanValue();
  
@ -1363,6 +1361,9 @@ bool Expr::isUnusedResultAWarning(SourceLocation &Loc, SourceRange &R1,
  case ParenExprClass:
    return cast<ParenExpr>(this)->getSubExpr()->
      isUnusedResultAWarning(Loc, R1, R2, Ctx);
+  case GenericSelectionExprClass:
+    return cast<GenericSelectionExpr>(this)->getResultExpr()->
+      isUnusedResultAWarning(Loc, R1, R2, Ctx);
  case UnaryOperatorClass: {
    const UnaryOperator *UO = cast<UnaryOperator>(this);

@ -1573,21 +1574,20 @@ bool Expr::isUnusedResultAWarning(SourceLocation &Loc, SourceRange &R1,
 /// isOBJCGCCandidate - Check if an expression is objc gc'able.
 /// returns true, if it is; false otherwise.
 bool Expr::isOBJCGCCandidate(ASTContext &Ctx) const {
-  switch (getStmtClass()) {
+  const Expr *E = IgnoreParens();
+  switch (E->getStmtClass()) {
  default:
    return false;
  case ObjCIvarRefExprClass:
    return true;
  case Expr::UnaryOperatorClass:
-    return cast<UnaryOperator>(this)->getSubExpr()->isOBJCGCCandidate(Ctx);
-  case ParenExprClass:
-    return cast<ParenExpr>(this)->getSubExpr()->isOBJCGCCandidate(Ctx);
+    return cast<UnaryOperator>(E)->getSubExpr()->isOBJCGCCandidate(Ctx);
  case ImplicitCastExprClass:
-    return cast<ImplicitCastExpr>(this)->getSubExpr()->isOBJCGCCandidate(Ctx);
+    return cast<ImplicitCastExpr>(E)->getSubExpr()->isOBJCGCCandidate(Ctx);
  case CStyleCastExprClass:
-    return cast<CStyleCastExpr>(this)->getSubExpr()->isOBJCGCCandidate(Ctx);
+    return cast<CStyleCastExpr>(E)->getSubExpr()->isOBJCGCCandidate(Ctx);
  case DeclRefExprClass: {
-    const Decl *D = cast<DeclRefExpr>(this)->getDecl();
+    const Decl *D = cast<DeclRefExpr>(E)->getDecl();
    if (const VarDecl *VD = dyn_cast<VarDecl>(D)) {
      if (VD->hasGlobalStorage())
        return true;
@ -1600,11 +1600,11 @@ bool Expr::isOBJCGCCandidate(ASTContext &Ctx) const {
    return false;
  }
  case MemberExprClass: {
-    const MemberExpr *M = cast<MemberExpr>(this);
+    const MemberExpr *M = cast<MemberExpr>(E);
    return M->getBase()->isOBJCGCCandidate(Ctx);
  }
  case ArraySubscriptExprClass:
-    return cast<ArraySubscriptExpr>(this)->getBase()->isOBJCGCCandidate(Ctx);
+    return cast<ArraySubscriptExpr>(E)->getBase()->isOBJCGCCandidate(Ctx);
  }
 }

@ -1827,6 +1827,11 @@ Expr::CanThrowResult Expr::CanThrow(ASTContext &C) const {
      return CT_Dependent;
    return cast<ChooseExpr>(this)->getChosenSubExpr(C)->CanThrow(C);

+  case GenericSelectionExprClass:
+    if (cast<GenericSelectionExpr>(this)->isResultDependent())
+      return CT_Dependent;
+    return cast<GenericSelectionExpr>(this)->getResultExpr()->CanThrow(C);
+
    // Some expressions are always dependent.
  case DependentScopeDeclRefExprClass:
  case CXXUnresolvedConstructExprClass:
@ -1853,6 +1858,12 @@ Expr* Expr::IgnoreParens() {
        continue;
      }
    }
+    if (GenericSelectionExpr* P = dyn_cast<GenericSelectionExpr>(E)) {
+      if (!P->isResultDependent()) {
+        E = P->getResultExpr();
+        continue;
+      }
+    }
    return E;
  }
 }
@ -1876,6 +1887,12 @@ Expr *Expr::IgnoreParenCasts() {
        continue;
      }
    }
+    if (GenericSelectionExpr* P = dyn_cast<GenericSelectionExpr>(E)) {
+      if (!P->isResultDependent()) {
+        E = P->getResultExpr();
+        continue;
+      }
+    }
    return E;
  }
 }
@ -1900,6 +1917,11 @@ Expr *Expr::IgnoreParenLValueCasts() {
        E = P->getSubExpr();
        continue;
      }
+    } else if (GenericSelectionExpr* P = dyn_cast<GenericSelectionExpr>(E)) {
+      if (!P->isResultDependent()) {
+        E = P->getResultExpr();
+        continue;
+      }
    }
    break;
  }
@ -1923,6 +1945,12 @@ Expr *Expr::IgnoreParenImpCasts() {
        continue;
      }
    }
+    if (GenericSelectionExpr* P = dyn_cast<GenericSelectionExpr>(E)) {
+      if (!P->isResultDependent()) {
+        E = P->getResultExpr();
+        continue;
+      }
+    }
    return E;
  }
 }
@ -1965,6 +1993,13 @@ Expr *Expr::IgnoreParenNoopCasts(ASTContext &Ctx) {
      }
    }

+    if (GenericSelectionExpr* P = dyn_cast<GenericSelectionExpr>(E)) {
+      if (!P->isResultDependent()) {
+        E = P->getResultExpr();
+        continue;
+      }
+    }
+
    return E;
  }
 }
@ -2156,6 +2191,11 @@ bool Expr::isConstantInitializer(ASTContext &Ctx, bool IsForRef) const {
  case ParenExprClass:
    return cast<ParenExpr>(this)->getSubExpr()
      ->isConstantInitializer(Ctx, IsForRef);
+  case GenericSelectionExprClass:
+    if (cast<GenericSelectionExpr>(this)->isResultDependent())
+      return false;
+    return cast<GenericSelectionExpr>(this)->getResultExpr()
+      ->isConstantInitializer(Ctx, IsForRef);
  case ChooseExprClass:
    return cast<ChooseExpr>(this)->getChosenSubExpr(Ctx)
      ->isConstantInitializer(Ctx, IsForRef);
@ -2242,6 +2282,9 @@ Expr::isNullPointerConstant(ASTContext &Ctx,
    // Accept ((void*)0) as a null pointer constant, as many other
    // implementations do.
    return PE->getSubExpr()->isNullPointerConstant(Ctx, NPC);
+  } else if (const GenericSelectionExpr *GE =
+               dyn_cast<GenericSelectionExpr>(this)) {
+    return GE->getResultExpr()->isNullPointerConstant(Ctx, NPC);
  } else if (const CXXDefaultArgExpr *DefaultArg
               = dyn_cast<CXXDefaultArgExpr>(this)) {
    // See through default argument expressions
@ -2640,6 +2683,51 @@ void ShuffleVectorExpr::setExprs(ASTContext &C, Expr ** Exprs,
  memcpy(SubExprs, Exprs, sizeof(Expr *) * NumExprs);
 }

+GenericSelectionExpr::GenericSelectionExpr(ASTContext &Context,
+                               SourceLocation GenericLoc, Expr *ControllingExpr,
+                               TypeSourceInfo **AssocTypes, Expr **AssocExprs,
+                               unsigned NumAssocs, SourceLocation DefaultLoc,
+                               SourceLocation RParenLoc,
+                               bool ContainsUnexpandedParameterPack,
+                               unsigned ResultIndex)
+  : Expr(GenericSelectionExprClass,
+         AssocExprs[ResultIndex]->getType(),
+         AssocExprs[ResultIndex]->getValueKind(),
+         AssocExprs[ResultIndex]->getObjectKind(),
+         AssocExprs[ResultIndex]->isTypeDependent(),
+         AssocExprs[ResultIndex]->isValueDependent(),
+         ContainsUnexpandedParameterPack),
+    AssocTypes(new (Context) TypeSourceInfo*[NumAssocs]),
+    SubExprs(new (Context) Stmt*[END_EXPR+NumAssocs]), NumAssocs(NumAssocs),
+    ResultIndex(ResultIndex), GenericLoc(GenericLoc), DefaultLoc(DefaultLoc),
+    RParenLoc(RParenLoc) {
+  SubExprs[CONTROLLING] = ControllingExpr;
+  std::copy(AssocTypes, AssocTypes+NumAssocs, this->AssocTypes);
+  std::copy(AssocExprs, AssocExprs+NumAssocs, SubExprs+END_EXPR);
+}
+
+GenericSelectionExpr::GenericSelectionExpr(ASTContext &Context,
+                               SourceLocation GenericLoc, Expr *ControllingExpr,
+                               TypeSourceInfo **AssocTypes, Expr **AssocExprs,
+                               unsigned NumAssocs, SourceLocation DefaultLoc,
+                               SourceLocation RParenLoc,
+                               bool ContainsUnexpandedParameterPack)
+  : Expr(GenericSelectionExprClass,
+         Context.DependentTy,
+         VK_RValue,
+         OK_Ordinary,
+         /*isTypeDependent=*/  true,
+         /*isValueDependent=*/ true,
+         ContainsUnexpandedParameterPack),
+    AssocTypes(new (Context) TypeSourceInfo*[NumAssocs]),
+    SubExprs(new (Context) Stmt*[END_EXPR+NumAssocs]), NumAssocs(NumAssocs),
+    ResultIndex(-1U), GenericLoc(GenericLoc), DefaultLoc(DefaultLoc),
+    RParenLoc(RParenLoc) {
+  SubExprs[CONTROLLING] = ControllingExpr;
+  std::copy(AssocTypes, AssocTypes+NumAssocs, this->AssocTypes);
+  std::copy(AssocExprs, AssocExprs+NumAssocs, SubExprs+END_EXPR);
+}
+
 //===----------------------------------------------------------------------===//
 //  DesignatedInitExpr
 //===----------------------------------------------------------------------===//
--- a/lib/AST/ExprClassification.cpp
+++ b/lib/AST/ExprClassification.cpp
@ -233,6 +233,14 @@ static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
  case Expr::ParenExprClass:
    return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());

+    // C1X 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,
+    // or a void expression if its result expression is, respectively, an
+    // lvalue, a function designator, or a void expression.
+  case Expr::GenericSelectionExprClass:
+    if (cast<GenericSelectionExpr>(E)->isResultDependent())
+      return Cl::CL_PRValue;
+    return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());
+
  case Expr::BinaryOperatorClass:
  case Expr::CompoundAssignOperatorClass:
    // C doesn't have any binary expressions that are lvalues.
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@ -274,6 +274,9 @@ public:
  }

  bool VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }
+  bool VisitGenericSelectionExpr(GenericSelectionExpr *E) {
+    return Visit(E->getResultExpr());
+  }
  bool VisitDeclRefExpr(DeclRefExpr *E) {
    if (Info.Ctx.getCanonicalType(E->getType()).isVolatileQualified())
      return true;
@ -372,6 +375,9 @@ public:
  }
  
  bool VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }
+  bool VisitGenericSelectionExpr(GenericSelectionExpr *E) {
+    return Visit(E->getResultExpr());
+  }
  bool VisitDeclRefExpr(DeclRefExpr *E);
  bool VisitPredefinedExpr(PredefinedExpr *E) { return Success(E); }
  bool VisitCompoundLiteralExpr(CompoundLiteralExpr *E);
@ -501,6 +507,9 @@ public:
  }

  bool VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }
+  bool VisitGenericSelectionExpr(GenericSelectionExpr *E) {
+    return Visit(E->getResultExpr());
+  }

  bool VisitBinaryOperator(const BinaryOperator *E);
  bool VisitCastExpr(CastExpr* E);
@ -717,6 +726,8 @@ namespace {

    APValue VisitParenExpr(ParenExpr *E)
        { return Visit(E->getSubExpr()); }
+    APValue VisitGenericSelectionExpr(GenericSelectionExpr *E)
+        { return Visit(E->getResultExpr()); }
    APValue VisitUnaryExtension(const UnaryOperator *E)
      { return Visit(E->getSubExpr()); }
    APValue VisitUnaryPlus(const UnaryOperator *E)
@ -975,6 +986,9 @@ public:
  }

  bool VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }
+  bool VisitGenericSelectionExpr(GenericSelectionExpr *E) {
+    return Visit(E->getResultExpr());
+  }

  bool VisitIntegerLiteral(const IntegerLiteral *E) {
    return Success(E->getValue(), E);
@ -1918,6 +1932,9 @@ public:
  }

  bool VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }
+  bool VisitGenericSelectionExpr(GenericSelectionExpr *E) {
+    return Visit(E->getResultExpr());
+  }
  bool VisitCallExpr(const CallExpr *E);

  bool VisitUnaryOperator(const UnaryOperator *E);
@ -2251,6 +2268,9 @@ public:
  }

  bool VisitParenExpr(ParenExpr *E) { return Visit(E->getSubExpr()); }
+  bool VisitGenericSelectionExpr(GenericSelectionExpr *E) {
+    return Visit(E->getResultExpr());
+  }

  bool VisitImaginaryLiteral(ImaginaryLiteral *E);

@ -2839,6 +2859,8 @@ static ICEDiag CheckICE(const Expr* E, ASTContext &Ctx) {

  case Expr::ParenExprClass:
    return CheckICE(cast<ParenExpr>(E)->getSubExpr(), Ctx);
+  case Expr::GenericSelectionExprClass:
+    return CheckICE(cast<GenericSelectionExpr>(E)->getResultExpr(), Ctx);
  case Expr::IntegerLiteralClass:
  case Expr::CharacterLiteralClass:
  case Expr::CXXBoolLiteralExprClass:
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@ -1750,6 +1750,7 @@ void CXXNameMangler::mangleExpression(const Expr *E, unsigned Arity) {
  case Expr::ChooseExprClass:
  case Expr::CompoundLiteralExprClass:
  case Expr::ExtVectorElementExprClass:
+  case Expr::GenericSelectionExprClass:
  case Expr::ObjCEncodeExprClass:
  case Expr::ObjCIsaExprClass:
  case Expr::ObjCIvarRefExprClass:
--- a/lib/AST/StmtPrinter.cpp
+++ b/lib/AST/StmtPrinter.cpp
@ -737,6 +737,23 @@ void StmtPrinter::VisitUnaryExprOrTypeTraitExpr(UnaryExprOrTypeTraitExpr *Node){
    PrintExpr(Node->getArgumentExpr());
  }
 }
+
+void StmtPrinter::VisitGenericSelectionExpr(GenericSelectionExpr *Node) {
+  OS << "_Generic(";
+  PrintExpr(Node->getControllingExpr());
+  for (unsigned i = 0; i != Node->getNumAssocs(); ++i) {
+    OS << ", ";
+    QualType T = Node->getAssocType(i);
+    if (T.isNull())
+      OS << "default";
+    else
+      OS << T.getAsString(Policy);
+    OS << ": ";
+    PrintExpr(Node->getAssocExpr(i));
+  }
+  OS << ")";
+}
+
 void StmtPrinter::VisitArraySubscriptExpr(ArraySubscriptExpr *Node) {
  PrintExpr(Node->getLHS());
  OS << "[";
--- a/lib/AST/StmtProfile.cpp
+++ b/lib/AST/StmtProfile.cpp
@ -434,6 +434,18 @@ void StmtProfiler::VisitBlockDeclRefExpr(BlockDeclRefExpr *S) {
  ID.AddBoolean(S->isConstQualAdded());
 }

+void StmtProfiler::VisitGenericSelectionExpr(GenericSelectionExpr *S) {
+  VisitExpr(S);
+  for (unsigned i = 0; i != S->getNumAssocs(); ++i) {
+    QualType T = S->getAssocType(i);
+    if (T.isNull())
+      ID.AddPointer(0);
+    else
+      VisitType(T);
+    VisitExpr(S->getAssocExpr(i));
+  }
+}
+
 static Stmt::StmtClass DecodeOperatorCall(CXXOperatorCallExpr *S,
                                          UnaryOperatorKind &UnaryOp,
                                          BinaryOperatorKind &BinaryOp) {
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@ -239,10 +239,7 @@ EmitExprForReferenceBinding(CodeGenFunction &CGF, const Expr *E,

    llvm::SmallVector<SubobjectAdjustment, 2> Adjustments;
    while (true) {
-      if (const ParenExpr *PE = dyn_cast<ParenExpr>(E)) {
-        E = PE->getSubExpr();
-        continue;
-      } 
+      E = E->IgnoreParens();

      if (const CastExpr *CE = dyn_cast<CastExpr>(E)) {
        if ((CE->getCastKind() == CK_DerivedToBase ||
@ -545,6 +542,8 @@ LValue CodeGenFunction::EmitLValue(const Expr *E) {
  case Expr::DeclRefExprClass:
    return EmitDeclRefLValue(cast<DeclRefExpr>(E));
  case Expr::ParenExprClass:return EmitLValue(cast<ParenExpr>(E)->getSubExpr());
+  case Expr::GenericSelectionExprClass:
+    return EmitLValue(cast<GenericSelectionExpr>(E)->getResultExpr());
  case Expr::PredefinedExprClass:
    return EmitPredefinedLValue(cast<PredefinedExpr>(E));
  case Expr::StringLiteralClass:
@ -1099,6 +1098,12 @@ static void setObjCGCLValueClass(const ASTContext &Ctx, const Expr *E,
    }
    return;
  }
+
+  if (const GenericSelectionExpr *Exp = dyn_cast<GenericSelectionExpr>(E)) {
+    setObjCGCLValueClass(Ctx, Exp->getResultExpr(), LV);
+    return;
+  }
+
  if (const ImplicitCastExpr *Exp = dyn_cast<ImplicitCastExpr>(E)) {
    setObjCGCLValueClass(Ctx, Exp->getSubExpr(), LV);
    return;
--- a/lib/CodeGen/CGExprAgg.cpp
+++ b/lib/CodeGen/CGExprAgg.cpp
@ -81,6 +81,9 @@ public:
    CGF.ErrorUnsupported(S, "aggregate expression");
  }
  void VisitParenExpr(ParenExpr *PE) { Visit(PE->getSubExpr()); }
+  void VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
+    Visit(GE->getResultExpr());
+  }
  void VisitUnaryExtension(UnaryOperator *E) { Visit(E->getSubExpr()); }

  // l-values.
@ -518,9 +521,8 @@ void AggExprEmitter::VisitImplicitValueInitExpr(ImplicitValueInitExpr *E) {
 /// zero to memory, return true.  This can return false if uncertain, so it just
 /// handles simple cases.
 static bool isSimpleZero(const Expr *E, CodeGenFunction &CGF) {
-  // (0)
-  if (const ParenExpr *PE = dyn_cast<ParenExpr>(E))
-    return isSimpleZero(PE->getSubExpr(), CGF);
+  E = E->IgnoreParens();
+
  // 0
  if (const IntegerLiteral *IL = dyn_cast<IntegerLiteral>(E))
    return IL->getValue() == 0;
@ -743,8 +745,7 @@ void AggExprEmitter::VisitInitListExpr(InitListExpr *E) {
 /// non-zero bytes that will be stored when outputting the initializer for the
 /// specified initializer expression.
 static uint64_t GetNumNonZeroBytesInInit(const Expr *E, CodeGenFunction &CGF) {
-  if (const ParenExpr *PE = dyn_cast<ParenExpr>(E))
-    return GetNumNonZeroBytesInInit(PE->getSubExpr(), CGF);
+  E = E->IgnoreParens();

  // 0 and 0.0 won't require any non-zero stores!
  if (isSimpleZero(E, CGF)) return 0;
--- a/lib/CodeGen/CGExprComplex.cpp
+++ b/lib/CodeGen/CGExprComplex.cpp
@ -108,6 +108,9 @@ public:
  }
  ComplexPairTy VisitExpr(Expr *S);
  ComplexPairTy VisitParenExpr(ParenExpr *PE) { return Visit(PE->getSubExpr());}
+  ComplexPairTy VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
+    return Visit(GE->getResultExpr());
+  }
  ComplexPairTy VisitImaginaryLiteral(const ImaginaryLiteral *IL);

  // l-values.
--- a/lib/CodeGen/CGExprConstant.cpp
+++ b/lib/CodeGen/CGExprConstant.cpp
@ -457,6 +457,10 @@ public:
    return Visit(PE->getSubExpr());
  }

+  llvm::Constant *VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
+    return Visit(GE->getResultExpr());
+  }
+
  llvm::Constant *VisitCompoundLiteralExpr(CompoundLiteralExpr *E) {
    return Visit(E->getInitializer());
  }
--- a/lib/CodeGen/CGExprScalar.cpp
+++ b/lib/CodeGen/CGExprScalar.cpp
@ -163,6 +163,9 @@ public:
  Value *VisitParenExpr(ParenExpr *PE) {
    return Visit(PE->getSubExpr()); 
  }
+  Value *VisitGenericSelectionExpr(GenericSelectionExpr *GE) {
+    return Visit(GE->getResultExpr());
+  }

  // Leaves.
  Value *VisitIntegerLiteral(const IntegerLiteral *E) {
@ -2396,8 +2399,7 @@ Value *ScalarExprEmitter::VisitBinComma(const BinaryOperator *E) {
 /// flow into selects in some cases.
 static bool isCheapEnoughToEvaluateUnconditionally(const Expr *E,
                                                   CodeGenFunction &CGF) {
-  if (const ParenExpr *PE = dyn_cast<ParenExpr>(E))
-    return isCheapEnoughToEvaluateUnconditionally(PE->getSubExpr(), CGF);
+  E = E->IgnoreParens();

  // TODO: Allow anything we can constant fold to an integer or fp constant.
  if (isa<IntegerLiteral>(E) || isa<CharacterLiteral>(E) ||
--- a/lib/CodeGen/CodeGenFunction.cpp
+++ b/lib/CodeGen/CodeGenFunction.cpp
@ -469,8 +469,7 @@ ConstantFoldsToSimpleInteger(const Expr *Cond, llvm::APInt &ResultInt) {
 void CodeGenFunction::EmitBranchOnBoolExpr(const Expr *Cond,
                                           llvm::BasicBlock *TrueBlock,
                                           llvm::BasicBlock *FalseBlock) {
-  if (const ParenExpr *PE = dyn_cast<ParenExpr>(Cond))
-    return EmitBranchOnBoolExpr(PE->getSubExpr(), TrueBlock, FalseBlock);
+  Cond = Cond->IgnoreParens();

  if (const BinaryOperator *CondBOp = dyn_cast<BinaryOperator>(Cond)) {
    // Handle X && Y in a condition.
--- a/lib/Lex/PPMacroExpansion.cpp
+++ b/lib/Lex/PPMacroExpansion.cpp
@ -548,6 +548,7 @@ static bool HasFeature(const Preprocessor &PP, const IdentifierInfo *II) {
           .Case("cxx_exceptions", LangOpts.Exceptions)
           .Case("cxx_rtti", LangOpts.RTTI)
           .Case("enumerator_attributes", true)
+           .Case("generic_selections", true)
           .Case("objc_nonfragile_abi", LangOpts.ObjCNonFragileABI)
           .Case("objc_weak_class", LangOpts.ObjCNonFragileABI)
           .Case("ownership_holds", true)
--- a/lib/Parse/ParseExpr.cpp
+++ b/lib/Parse/ParseExpr.cpp
@ -465,6 +465,7 @@ ExprResult Parser::ParseCastExpression(bool isUnaryExpression,
 /// [C++]   boolean-literal  [C++ 2.13.5]
 /// [C++0x] 'nullptr'        [C++0x 2.14.7]
 ///         '(' expression ')'
+/// [C1X]   generic-selection
 ///         '__func__'        [C99 6.4.2.2]
 /// [GNU]   '__FUNCTION__'
 /// [GNU]   '__PRETTY_FUNCTION__'
@ -731,6 +732,9 @@ ExprResult Parser::ParseCastExpression(bool isUnaryExpression,
  case tok::wide_string_literal:
    Res = ParseStringLiteralExpression();
    break;
+  case tok::kw__Generic:   // primary-expression: generic-selection [C1X 6.5.1]
+    Res = ParseGenericSelectionExpression();
+    break;
  case tok::kw___builtin_va_arg:
  case tok::kw___builtin_offsetof:
  case tok::kw___builtin_choose_expr:
@ -1802,6 +1806,100 @@ ExprResult Parser::ParseStringLiteralExpression() {
  return Actions.ActOnStringLiteral(&StringToks[0], StringToks.size());
 }

+/// ParseGenericSelectionExpression - Parse a C1X generic-selection
+/// [C1X 6.5.1.1].
+///
+///    generic-selection:
+///           _Generic ( assignment-expression , generic-assoc-list )
+///    generic-assoc-list:
+///           generic-association
+///           generic-assoc-list , generic-association
+///    generic-association:
+///           type-name : assignment-expression
+///           default : assignment-expression
+ExprResult Parser::ParseGenericSelectionExpression() {
+  assert(Tok.is(tok::kw__Generic) && "_Generic keyword expected");
+  SourceLocation KeyLoc = ConsumeToken();
+
+  if (!getLang().C1X)
+    Diag(KeyLoc, diag::ext_c1x_generic_selection);
+
+  SourceLocation LParenLoc = Tok.getLocation();
+  if (ExpectAndConsume(tok::l_paren, diag::err_expected_lparen, ""))
+    return ExprError();
+
+  ExprResult ControllingExpr;
+  {
+    // C1X 6.5.1.1p3 "The controlling expression of a generic selection is
+    // not evaluated."
+    EnterExpressionEvaluationContext Unevaluated(Actions, Sema::Unevaluated);
+    ControllingExpr = ParseAssignmentExpression();
+    if (ControllingExpr.isInvalid()) {
+      SkipUntil(tok::r_paren);
+      return ExprError();
+    }
+  }
+
+  if (ExpectAndConsume(tok::comma, diag::err_expected_comma, "")) {
+    SkipUntil(tok::r_paren);
+    return ExprError();
+  }
+
+  SourceLocation DefaultLoc;
+  TypeVector Types(Actions);
+  ExprVector Exprs(Actions);
+  while (1) {
+    ParsedType Ty;
+    if (Tok.is(tok::kw_default)) {
+      // C1X 6.5.1.1p2 "A generic selection shall have no more than one default
+      // generic association."
+      if (!DefaultLoc.isInvalid()) {
+        Diag(Tok, diag::err_duplicate_default_assoc);
+        Diag(DefaultLoc, diag::note_previous_default_assoc);
+        SkipUntil(tok::r_paren);
+        return ExprError();
+      }
+      DefaultLoc = ConsumeToken();
+      Ty = ParsedType();
+    } else {
+      ColonProtectionRAIIObject X(*this);
+      TypeResult TR = ParseTypeName();
+      if (TR.isInvalid()) {
+        SkipUntil(tok::r_paren);
+        return ExprError();
+      }
+      Ty = TR.release();
+    }
+    Types.push_back(Ty);
+
+    if (ExpectAndConsume(tok::colon, diag::err_expected_colon, "")) {
+      SkipUntil(tok::r_paren);
+      return ExprError();
+    }
+
+    // FIXME: These expressions should be parsed in a potentially potentially
+    // evaluated context.
+    ExprResult ER(ParseAssignmentExpression());
+    if (ER.isInvalid()) {
+      SkipUntil(tok::r_paren);
+      return ExprError();
+    }
+    Exprs.push_back(ER.release());
+
+    if (Tok.isNot(tok::comma))
+      break;
+    ConsumeToken();
+  }
+
+  SourceLocation RParenLoc = MatchRHSPunctuation(tok::r_paren, LParenLoc);
+  if (RParenLoc.isInvalid())
+    return ExprError();
+
+  return Actions.ActOnGenericSelectionExpr(KeyLoc, DefaultLoc, RParenLoc,
+                                           ControllingExpr.release(),
+                                           move_arg(Types), move_arg(Exprs));
+}
+
 /// ParseExpressionList - Used for C/C++ (argument-)expression-list.
 ///
 ///       argument-expression-list:
--- a/lib/Sema/SemaChecking.cpp
+++ b/lib/Sema/SemaChecking.cpp
@ -905,6 +905,8 @@ bool Sema::SemaCheckStringLiteral(const Expr *E, const CallExpr *TheCall,
  if (E->isTypeDependent() || E->isValueDependent())
    return false;

+  E = E->IgnoreParens();
+
  switch (E->getStmtClass()) {
  case Stmt::BinaryConditionalOperatorClass:
  case Stmt::ConditionalOperatorClass: {
@ -927,11 +929,6 @@ bool Sema::SemaCheckStringLiteral(const Expr *E, const CallExpr *TheCall,
    goto tryAgain;
  }

-  case Stmt::ParenExprClass: {
-    E = cast<ParenExpr>(E)->getSubExpr();
-    goto tryAgain;
-  }
-
  case Stmt::OpaqueValueExprClass:
    if (const Expr *src = cast<OpaqueValueExpr>(E)->getSourceExpr()) {
      E = src;
@ -1897,14 +1894,12 @@ static Expr *EvalAddr(Expr *E, llvm::SmallVectorImpl<DeclRefExpr *> &refVars) {
          E->getType()->isObjCQualifiedIdType()) &&
         "EvalAddr only works on pointers");

+  E = E->IgnoreParens();
+
  // Our "symbolic interpreter" is just a dispatch off the currently
  // viewed AST node.  We then recursively traverse the AST by calling
  // EvalAddr and EvalVal appropriately.
  switch (E->getStmtClass()) {
-  case Stmt::ParenExprClass:
-    // Ignore parentheses.
-    return EvalAddr(cast<ParenExpr>(E)->getSubExpr(), refVars);
-
  case Stmt::DeclRefExprClass: {
    DeclRefExpr *DR = cast<DeclRefExpr>(E);

@ -2034,6 +2029,8 @@ do {
  // Our "symbolic interpreter" is just a dispatch off the currently
  // viewed AST node.  We then recursively traverse the AST by calling
  // EvalAddr and EvalVal appropriately.
+
+  E = E->IgnoreParens();
  switch (E->getStmtClass()) {
  case Stmt::ImplicitCastExprClass: {
    ImplicitCastExpr *IE = cast<ImplicitCastExpr>(E);
@ -2067,12 +2064,6 @@ do {
    return NULL;
  }

-  case Stmt::ParenExprClass: {
-    // Ignore parentheses.
-    E = cast<ParenExpr>(E)->getSubExpr();
-    continue;
-  }
-
  case Stmt::UnaryOperatorClass: {
    // The only unary operator that make sense to handle here
    // is Deref.  All others don't resolve to a "name."  This includes
@ -3272,11 +3263,9 @@ static void CheckArrayAccess_Check(Sema &S,
 }

 void Sema::CheckArrayAccess(const Expr *expr) {
-  while (true)
+  while (true) {
+    expr = expr->IgnoreParens();
    switch (expr->getStmtClass()) {
-      case Stmt::ParenExprClass:
-        expr = cast<ParenExpr>(expr)->getSubExpr();
-        continue;
      case Stmt::ArraySubscriptExprClass:
        CheckArrayAccess_Check(*this, cast<ArraySubscriptExpr>(expr));
        return;
@ -3291,4 +3280,5 @@ void Sema::CheckArrayAccess(const Expr *expr) {
      default:
        return;
    }
+  }
 }
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@ -748,6 +748,163 @@ QualType Sema::UsualArithmeticConversions(ExprResult &lhsExpr, ExprResult &rhsEx
 //===----------------------------------------------------------------------===//


+ExprResult
+Sema::ActOnGenericSelectionExpr(SourceLocation KeyLoc,
+                                SourceLocation DefaultLoc,
+                                SourceLocation RParenLoc,
+                                Expr *ControllingExpr,
+                                MultiTypeArg types,
+                                MultiExprArg exprs) {
+  unsigned NumAssocs = types.size();
+  assert(NumAssocs == exprs.size());
+
+  ParsedType *ParsedTypes = types.release();
+  Expr **Exprs = exprs.release();
+
+  TypeSourceInfo **Types = new TypeSourceInfo*[NumAssocs];
+  for (unsigned i = 0; i < NumAssocs; ++i) {
+    if (ParsedTypes[i])
+      (void) GetTypeFromParser(ParsedTypes[i], &Types[i]);
+    else
+      Types[i] = 0;
+  }
+
+  ExprResult ER = CreateGenericSelectionExpr(KeyLoc, DefaultLoc, RParenLoc,
+                                             ControllingExpr, Types, Exprs,
+                                             NumAssocs);
+  delete Types;
+  return ER;
+}
+
+ExprResult
+Sema::CreateGenericSelectionExpr(SourceLocation KeyLoc,
+                                 SourceLocation DefaultLoc,
+                                 SourceLocation RParenLoc,
+                                 Expr *ControllingExpr,
+                                 TypeSourceInfo **Types,
+                                 Expr **Exprs,
+                                 unsigned NumAssocs) {
+  bool TypeErrorFound = false,
+       IsResultDependent = ControllingExpr->isTypeDependent(),
+       ContainsUnexpandedParameterPack
+         = ControllingExpr->containsUnexpandedParameterPack();
+
+  for (unsigned i = 0; i < NumAssocs; ++i) {
+    if (Exprs[i]->containsUnexpandedParameterPack())
+      ContainsUnexpandedParameterPack = true;
+
+    if (Types[i]) {
+      if (Types[i]->getType()->containsUnexpandedParameterPack())
+        ContainsUnexpandedParameterPack = true;
+
+      if (Types[i]->getType()->isDependentType()) {
+        IsResultDependent = true;
+      } else {
+        // C1X 6.5.1.1p2 "The type name in a generic association shall specify a
+        // complete object type other than a variably modified type."
+        unsigned D = 0;
+        if (Types[i]->getType()->isIncompleteType())
+          D = diag::err_assoc_type_incomplete;
+        else if (!Types[i]->getType()->isObjectType())
+          D = diag::err_assoc_type_nonobject;
+        else if (Types[i]->getType()->isVariablyModifiedType())
+          D = diag::err_assoc_type_variably_modified;
+
+        if (D != 0) {
+          Diag(Types[i]->getTypeLoc().getBeginLoc(), D)
+            << Types[i]->getTypeLoc().getSourceRange()
+            << Types[i]->getType();
+          TypeErrorFound = true;
+        }
+
+        // C1X 6.5.1.1p2 "No two generic associations in the same generic
+        // selection shall specify compatible types."
+        for (unsigned j = i+1; j < NumAssocs; ++j)
+          if (Types[j] && !Types[j]->getType()->isDependentType() &&
+              Context.typesAreCompatible(Types[i]->getType(),
+                                         Types[j]->getType())) {
+            Diag(Types[j]->getTypeLoc().getBeginLoc(),
+                 diag::err_assoc_compatible_types)
+              << Types[j]->getTypeLoc().getSourceRange()
+              << Types[j]->getType()
+              << Types[i]->getType();
+            Diag(Types[i]->getTypeLoc().getBeginLoc(),
+                 diag::note_compat_assoc)
+              << Types[i]->getTypeLoc().getSourceRange()
+              << Types[i]->getType();
+            TypeErrorFound = true;
+          }
+      }
+    }
+  }
+  if (TypeErrorFound)
+    return ExprError();
+
+  // If we determined that the generic selection is result-dependent, don't
+  // try to compute the result expression.
+  if (IsResultDependent)
+    return Owned(new (Context) GenericSelectionExpr(
+                   Context, KeyLoc, ControllingExpr,
+                   Types, Exprs, NumAssocs, DefaultLoc,
+                   RParenLoc, ContainsUnexpandedParameterPack));
+
+  llvm::SmallVector<unsigned, 1> CompatIndices;
+  unsigned DefaultIndex = -1U;
+  for (unsigned i = 0; i < NumAssocs; ++i) {
+    if (!Types[i])
+      DefaultIndex = i;
+    else if (Context.typesAreCompatible(ControllingExpr->getType(),
+                                        Types[i]->getType()))
+      CompatIndices.push_back(i);
+  }
+
+  // C1X 6.5.1.1p2 "The controlling expression of a generic selection shall have
+  // type compatible with at most one of the types named in its generic
+  // association list."
+  if (CompatIndices.size() > 1) {
+    // We strip parens here because the controlling expression is typically
+    // parenthesized in macro definitions.
+    ControllingExpr = ControllingExpr->IgnoreParens();
+    Diag(ControllingExpr->getLocStart(), diag::err_generic_sel_multi_match)
+      << ControllingExpr->getSourceRange() << ControllingExpr->getType()
+      << (unsigned) CompatIndices.size();
+    for (llvm::SmallVector<unsigned, 1>::iterator I = CompatIndices.begin(),
+         E = CompatIndices.end(); I != E; ++I) {
+      Diag(Types[*I]->getTypeLoc().getBeginLoc(),
+           diag::note_compat_assoc)
+        << Types[*I]->getTypeLoc().getSourceRange()
+        << Types[*I]->getType();
+    }
+    return ExprError();
+  }
+
+  // C1X 6.5.1.1p2 "If a generic selection has no default generic association,
+  // its controlling expression shall have type compatible with exactly one of
+  // the types named in its generic association list."
+  if (DefaultIndex == -1U && CompatIndices.size() == 0) {
+    // We strip parens here because the controlling expression is typically
+    // parenthesized in macro definitions.
+    ControllingExpr = ControllingExpr->IgnoreParens();
+    Diag(ControllingExpr->getLocStart(), diag::err_generic_sel_no_match)
+      << ControllingExpr->getSourceRange() << ControllingExpr->getType();
+    return ExprError();
+  }
+
+  // C1X 6.5.1.1p3 "If a generic selection has a generic association with a
+  // type name that is compatible with the type of the controlling expression,
+  // then the result expression of the generic selection is the expression
+  // in that generic association. Otherwise, the result expression of the
+  // generic selection is the expression in the default generic association."
+  unsigned ResultIndex =
+    CompatIndices.size() ? CompatIndices[0] : DefaultIndex;
+
+  return Owned(new (Context) GenericSelectionExpr(
+                 Context, KeyLoc, ControllingExpr,
+                 Types, Exprs, NumAssocs, DefaultLoc,
+                 RParenLoc, ContainsUnexpandedParameterPack,
+                 ResultIndex));
+}
+
 /// ActOnStringLiteral - The specified tokens were lexed as pasted string
 /// fragments (e.g. "foo" "bar" L"baz").  The result string has to handle string
 /// concatenation ([C99 5.1.1.2, translation phase #6]), so it may come from
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@ -1602,6 +1602,22 @@ public:
                                   RParenLoc);
  }

+  /// \brief Build a new generic selection expression.
+  ///
+  /// By default, performs semantic analysis to build the new expression.
+  /// Subclasses may override this routine to provide different behavior.
+  ExprResult RebuildGenericSelectionExpr(SourceLocation KeyLoc,
+                                         SourceLocation DefaultLoc,
+                                         SourceLocation RParenLoc,
+                                         Expr *ControllingExpr,
+                                         TypeSourceInfo **Types,
+                                         Expr **Exprs,
+                                         unsigned NumAssocs) {
+    return getSema().CreateGenericSelectionExpr(KeyLoc, DefaultLoc, RParenLoc,
+                                                ControllingExpr, Types, Exprs,
+                                                NumAssocs);
+  }
+
  /// \brief Build a new overloaded operator call expression.
  ///
  /// By default, performs semantic analysis to build the new expression.
@ -5523,6 +5539,42 @@ TreeTransform<Derived>::TransformCharacterLiteral(CharacterLiteral *E) {
  return SemaRef.Owned(E);
 }

+template<typename Derived>
+ExprResult
+TreeTransform<Derived>::TransformGenericSelectionExpr(GenericSelectionExpr *E) {
+  ExprResult ControllingExpr =
+    getDerived().TransformExpr(E->getControllingExpr());
+  if (ControllingExpr.isInvalid())
+    return ExprError();
+
+  llvm::SmallVector<Expr *, 4> AssocExprs;
+  llvm::SmallVector<TypeSourceInfo *, 4> AssocTypes;
+  for (unsigned i = 0; i != E->getNumAssocs(); ++i) {
+    TypeSourceInfo *TS = E->getAssocTypeSourceInfo(i);
+    if (TS) {
+      TypeSourceInfo *AssocType = getDerived().TransformType(TS);
+      if (!AssocType)
+        return ExprError();
+      AssocTypes.push_back(AssocType);
+    } else {
+      AssocTypes.push_back(0);
+    }
+
+    ExprResult AssocExpr = getDerived().TransformExpr(E->getAssocExpr(i));
+    if (AssocExpr.isInvalid())
+      return ExprError();
+    AssocExprs.push_back(AssocExpr.release());
+  }
+
+  return getDerived().RebuildGenericSelectionExpr(E->getGenericLoc(),
+                                                  E->getDefaultLoc(),
+                                                  E->getRParenLoc(),
+                                                  ControllingExpr.release(),
+                                                  AssocTypes.data(),
+                                                  AssocExprs.data(),
+                                                  E->getNumAssocs());
+}
+
 template<typename Derived>
 ExprResult
 TreeTransform<Derived>::TransformParenExpr(ParenExpr *E) {
--- a/lib/Serialization/ASTReaderStmt.cpp
+++ b/lib/Serialization/ASTReaderStmt.cpp
@ -122,6 +122,7 @@ namespace clang {
    void VisitShuffleVectorExpr(ShuffleVectorExpr *E);
    void VisitBlockExpr(BlockExpr *E);
    void VisitBlockDeclRefExpr(BlockDeclRefExpr *E);
+    void VisitGenericSelectionExpr(GenericSelectionExpr *E);
    void VisitObjCStringLiteral(ObjCStringLiteral *E);
    void VisitObjCEncodeExpr(ObjCEncodeExpr *E);
    void VisitObjCSelectorExpr(ObjCSelectorExpr *E);
@ -822,6 +823,25 @@ void ASTStmtReader::VisitBlockDeclRefExpr(BlockDeclRefExpr *E) {
  E->setConstQualAdded(Record[Idx++]);
 }

+void ASTStmtReader::VisitGenericSelectionExpr(GenericSelectionExpr *E) {
+  VisitExpr(E);
+  E->NumAssocs = Record[Idx++];
+  E->AssocTypes = new (*Reader.getContext()) TypeSourceInfo*[E->NumAssocs];
+  E->SubExprs =
+   new(*Reader.getContext()) Stmt*[GenericSelectionExpr::END_EXPR+E->NumAssocs];
+
+  E->SubExprs[GenericSelectionExpr::CONTROLLING] = Reader.ReadSubExpr();
+  for (unsigned I = 0, N = E->getNumAssocs(); I != N; ++I) {
+    E->AssocTypes[I] = GetTypeSourceInfo(Record, Idx);
+    E->SubExprs[GenericSelectionExpr::END_EXPR+I] = Reader.ReadSubExpr();
+  }
+  E->ResultIndex = Record[Idx++];
+
+  E->GenericLoc = ReadSourceLocation(Record, Idx);
+  E->DefaultLoc = ReadSourceLocation(Record, Idx);
+  E->RParenLoc = ReadSourceLocation(Record, Idx);
+}
+
 //===----------------------------------------------------------------------===//
 // Objective-C Expressions and Statements

@ -1696,6 +1716,10 @@ Stmt *ASTReader::ReadStmtFromStream(PerFileData &F) {
      S = new (Context) BlockDeclRefExpr(Empty);
      break;

+    case EXPR_GENERIC_SELECTION:
+      S = new (Context) GenericSelectionExpr(Empty);
+      break;
+
    case EXPR_OBJC_STRING_LITERAL:
      S = new (Context) ObjCStringLiteral(Empty);
      break;
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@ -659,6 +659,7 @@ static void AddStmtsExprs(llvm::BitstreamWriter &Stream,
  RECORD(EXPR_SHUFFLE_VECTOR);
  RECORD(EXPR_BLOCK);
  RECORD(EXPR_BLOCK_DECL_REF);
+  RECORD(EXPR_GENERIC_SELECTION);
  RECORD(EXPR_OBJC_STRING_LITERAL);
  RECORD(EXPR_OBJC_ENCODE);
  RECORD(EXPR_OBJC_SELECTOR_EXPR);
--- a/lib/Serialization/ASTWriterStmt.cpp
+++ b/lib/Serialization/ASTWriterStmt.cpp
@ -93,6 +93,7 @@ namespace clang {
    void VisitShuffleVectorExpr(ShuffleVectorExpr *E);
    void VisitBlockExpr(BlockExpr *E);
    void VisitBlockDeclRefExpr(BlockDeclRefExpr *E);
+    void VisitGenericSelectionExpr(GenericSelectionExpr *E);

    // Objective-C Expressions
    void VisitObjCStringLiteral(ObjCStringLiteral *E);
@ -785,6 +786,23 @@ void ASTStmtWriter::VisitBlockDeclRefExpr(BlockDeclRefExpr *E) {
  Code = serialization::EXPR_BLOCK_DECL_REF;
 }

+void ASTStmtWriter::VisitGenericSelectionExpr(GenericSelectionExpr *E) {
+  VisitExpr(E);
+  Record.push_back(E->getNumAssocs());
+
+  Writer.AddStmt(E->getControllingExpr());
+  for (unsigned I = 0, N = E->getNumAssocs(); I != N; ++I) {
+    Writer.AddTypeSourceInfo(E->getAssocTypeSourceInfo(I), Record);
+    Writer.AddStmt(E->getAssocExpr(I));
+  }
+  Record.push_back(E->isResultDependent() ? -1U : E->getResultIndex());
+
+  Writer.AddSourceLocation(E->getGenericLoc(), Record);
+  Writer.AddSourceLocation(E->getDefaultLoc(), Record);
+  Writer.AddSourceLocation(E->getRParenLoc(), Record);
+  Code = serialization::EXPR_GENERIC_SELECTION;
+}
+
 //===----------------------------------------------------------------------===//
 // Objective-C Expressions and Statements.
 //===----------------------------------------------------------------------===//
--- a/lib/StaticAnalyzer/Core/BugReporter.cpp
+++ b/lib/StaticAnalyzer/Core/BugReporter.cpp
@ -859,7 +859,8 @@ class EdgeBuilder {
          default:
            break;
          case Stmt::ParenExprClass:
-            S = cast<ParenExpr>(S)->IgnoreParens();
+          case Stmt::GenericSelectionExprClass:
+            S = cast<Expr>(S)->IgnoreParens();
            firstCharOnly = true;
            continue;
          case Stmt::BinaryConditionalOperatorClass:
--- a/lib/StaticAnalyzer/Core/Environment.cpp
+++ b/lib/StaticAnalyzer/Core/Environment.cpp
@ -41,6 +41,10 @@ SVal Environment::getSVal(const Stmt *E, SValBuilder& svalBuilder) const {
        // ParenExprs are no-ops.
        E = cast<ParenExpr>(E)->getSubExpr();
        continue;
+      case Stmt::GenericSelectionExprClass:
+        // GenericSelectionExprs are no-ops.
+        E = cast<GenericSelectionExpr>(E)->getResultExpr();
+        continue;
      case Stmt::CharacterLiteralClass: {
        const CharacterLiteral* C = cast<CharacterLiteral>(E);
        return svalBuilder.makeIntVal(C->getValue(), C->getType());
--- a/lib/StaticAnalyzer/Core/ExprEngine.cpp
+++ b/lib/StaticAnalyzer/Core/ExprEngine.cpp
@ -458,6 +458,8 @@ void ExprEngine::Visit(const Stmt* S, ExplodedNode* Pred,

    case Stmt::ParenExprClass:
      llvm_unreachable("ParenExprs already handled.");
+    case Stmt::GenericSelectionExprClass:
+      llvm_unreachable("GenericSelectionExprs already handled.");
    // Cases that should never be evaluated simply because they shouldn't
    // appear in the CFG.
    case Stmt::BreakStmtClass:
--- a/test/PCH/exprs.c
+++ b/test/PCH/exprs.c
@ -93,3 +93,6 @@ choose_expr *int_ptr8 = &integer;

 // ShuffleVectorExpr
 shuffle_expr *vec_ptr = &vec2;
+
+// GenericSelectionExpr
+generic_selection_expr *double_ptr6 = &floating;
--- a/test/PCH/exprs.h
+++ b/test/PCH/exprs.h
@ -99,3 +99,7 @@ typedef typeof(__builtin_choose_expr(17 > 19, d0, 1)) choose_expr;

 // ShuffleVectorExpr
 typedef typeof(__builtin_shufflevector(vec2, vec2b, 2, 1)) shuffle_expr;
+
+// GenericSelectionExpr
+typedef typeof(_Generic(i, char*: 0, int: 0., default: hello))
+  generic_selection_expr;
--- a/test/Parser/c1x-generic-selection.c
+++ b/test/Parser/c1x-generic-selection.c
@ -0,0 +1,10 @@
+// RUN: %clang_cc1 -std=c1x -fsyntax-only -verify %s
+
+void foo(void) {
+  _Generic; // expected-error {{expected '('}}
+  (void) _Generic(0); // expected-error {{expected ','}}
+  (void) _Generic(0, void); // expected-error {{expected ':'}}
+  (void) _Generic(0,
+      default: 0,  // expected-note {{previous default generic association is here}}
+      default: 0); // expected-error {{duplicate default generic association}}
+}
--- a/test/Sema/generic-selection.c
+++ b/test/Sema/generic-selection.c
@ -0,0 +1,26 @@
+// RUN: %clang_cc1 -std=c1x -fsyntax-only -verify %s
+
+void foo(int n) {
+  (void) _Generic(0,
+      struct A: 0, // expected-error {{type 'struct A' in generic association incomplete}}
+      void(): 0,   // expected-error {{type 'void ()' in generic association not an object type}}
+      int[n]: 0);  // expected-error {{type 'int [n]' in generic association is a variably modified type}}
+
+  (void) _Generic(0,
+      void (*)():     0,  // expected-note {{compatible type 'void (*)()' specified here}}
+      void (*)(void): 0); // expected-error {{type 'void (*)(void)' in generic association compatible with previously specified type 'void (*)()'}}
+
+  (void) _Generic((void (*)()) 0, // expected-error {{controlling expression type 'void (*)()' compatible with 2 generic association types}}
+      void (*)(int):  0,  // expected-note {{compatible type 'void (*)(int)' specified here}}
+      void (*)(void): 0); // expected-note {{compatible type 'void (*)(void)' specified here}}
+
+  (void) _Generic(0, // expected-error {{controlling expression type 'int' not compatible with any generic association type}}
+      char: 0, short: 0, long: 0);
+
+  int a1[_Generic(0, int: 1, short: 2, float: 3, default: 4) == 1 ? 1 : -1];
+  int a2[_Generic(0, default: 1, short: 2, float: 3, int: 4) == 4 ? 1 : -1];
+  int a3[_Generic(0L, int: 1, short: 2, float: 3, default: 4) == 4 ? 1 : -1];
+  int a4[_Generic(0L, default: 1, short: 2, float: 3, int: 4) == 1 ? 1 : -1];
+  int a5[_Generic(0, int: 1, short: 2, float: 3) == 1 ? 1 : -1];
+  int a6[_Generic(0, short: 1, float: 2, int: 3) == 3 ? 1 : -1];
+}
--- a/test/SemaCXX/generic-selection.cpp
+++ b/test/SemaCXX/generic-selection.cpp
@ -0,0 +1,46 @@
+// RUN: %clang_cc1 -std=c++0x -fsyntax-only -verify %s
+
+template <typename T, typename U = void*>
+struct A {
+  enum {
+    id = _Generic(T(), // expected-error {{controlling expression type 'char' not compatible with any generic association type}}
+        int: 1, // expected-note {{compatible type 'int' specified here}}
+        float: 2,
+        U: 3) // expected-error {{type 'int' in generic association compatible with previously specified type 'int'}}
+  };
+};
+
+static_assert(A<int>::id == 1, "fail");
+static_assert(A<float>::id == 2, "fail");
+static_assert(A<double, double>::id == 3, "fail");
+
+A<char> a1; // expected-note {{in instantiation of template class 'A<char, void *>' requested here}}
+A<short, int> a2; // expected-note {{in instantiation of template class 'A<short, int>' requested here}}
+
+template <typename T, typename U>
+struct B {
+  enum {
+    id = _Generic(T(),
+        int: 1, // expected-note {{compatible type 'int' specified here}}
+        int: 2, // expected-error {{type 'int' in generic association compatible with previously specified type 'int'}}
+        U: 3)
+  };
+};
+
+template <unsigned Arg, unsigned... Args> struct Or {
+  enum { result = Arg | Or<Args...>::result };
+};
+
+template <unsigned Arg> struct Or<Arg> {
+  enum { result = Arg };
+};
+
+template <class... Args> struct TypeMask {
+  enum {
+   result = Or<_Generic(Args(), int: 1, long: 2, short: 4, float: 8)...>::result
+  };
+};
+
+static_assert(TypeMask<int, long, short>::result == 7, "fail");
+static_assert(TypeMask<float, short>::result == 12, "fail");
+static_assert(TypeMask<int, float, float>::result == 9, "fail");
--- a/tools/libclang/CXCursor.cpp
+++ b/tools/libclang/CXCursor.cpp
@ -130,6 +130,7 @@ CXCursor cxcursor::MakeCXCursor(Stmt *S, Decl *Parent,
  case Stmt::AddrLabelExprClass:        
  case Stmt::StmtExprClass:             
  case Stmt::ChooseExprClass:           
+  case Stmt::GenericSelectionExprClass:
  case Stmt::GNUNullExprClass:          
  case Stmt::CXXStaticCastExprClass:      
  case Stmt::CXXDynamicCastExprClass: