AST representation for user-defined literals, plus just enough of semantic

analysis to make the AST representation testable. They are represented by a
new UserDefinedLiteral AST node, which is a sugared CallExpr. All semantic
properties, including full CodeGen support, are achieved for free by this
representation.

UserDefinedLiterals can never be dependent, so no custom instantiation
behavior is required. They are mangled as if they were direct calls to the
underlying literal operator. This matches g++'s apparent behavior (but not its
actual mangling, which is broken for literal-operator-ids).

User-defined *string* literals are now fully-operational, but the semantic
analysis is quite hacky and needs more work. No other forms of user-defined
literal are created yet, but the AST support for them is present.

This patch committed after midnight because we had already hit the quota for
new kinds of literal yesterday.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@152211 91177308-0d34-0410-b5e6-96231b3b80d8

29 files changed, 385 insertions, 23 deletions

diff --git a/include/clang/AST/ExprCXX.h b/include/clang/AST/ExprCXX.h
index 9631f54975..a9699f1ce8 100644
--- a/include/clang/AST/ExprCXX.h
+++ b/include/clang/AST/ExprCXX.h
@@ -324,6 +324,67 @@ public:
   static bool classof(const CXXConstCastExpr *) { return true; }
 };
 
+/// UserDefinedLiteral - A call to a literal operator (C++11 [over.literal])
+/// written as a user-defined literal (C++11 [lit.ext]).
+///
+/// Represents a user-defined literal, e.g. "foo"_bar or 1.23_xyz. While this
+/// is semantically equivalent to a normal call, this AST node provides better
+/// information about the syntactic representation of the literal.
+///
+/// Since literal operators are never found by ADL and can only be declared at
+/// namespace scope, a user-defined literal is never dependent.
+class UserDefinedLiteral : public CallExpr {
+  /// \brief The location of a ud-suffix within the literal.
+  SourceLocation UDSuffixLoc;
+
+public:
+  UserDefinedLiteral(ASTContext &C, Expr *Fn, Expr **Args, unsigned NumArgs,
+                     QualType T, ExprValueKind VK, SourceLocation LitEndLoc,
+                     SourceLocation SuffixLoc)
+    : CallExpr(C, UserDefinedLiteralClass, Fn, 0, Args, NumArgs, T, VK,
+               LitEndLoc), UDSuffixLoc(SuffixLoc) {}
+  explicit UserDefinedLiteral(ASTContext &C, EmptyShell Empty)
+    : CallExpr(C, UserDefinedLiteralClass, Empty) {}
+
+  /// The kind of literal operator which is invoked.
+  enum LiteralOperatorKind {
+    LOK_Raw,      ///< Raw form: operator "" X (const char *)
+    LOK_Template, ///< Raw form: operator "" X<cs...> ()
+    LOK_Integer,  ///< operator "" X (unsigned long long)
+    LOK_Floating, ///< operator "" X (long double)
+    LOK_String,   ///< operator "" X (const CharT *, size_t)
+    LOK_Character ///< operator "" X (CharT)
+  };
+
+  /// getLiteralOperatorKind - Returns the kind of literal operator invocation
+  /// which this expression represents.
+  LiteralOperatorKind getLiteralOperatorKind() const;
+
+  /// getCookedLiteral - If this is not a raw user-defined literal, get the
+  /// underlying cooked literal (representing the literal with the suffix
+  /// removed).
+  Expr *getCookedLiteral();
+  const Expr *getCookedLiteral() const {
+    return const_cast<UserDefinedLiteral*>(this)->getCookedLiteral();
+  }
+
+  /// getUDSuffixLoc - Returns the location of a ud-suffix in the expression.
+  /// For a string literal, there may be multiple identical suffixes. This
+  /// returns the first.
+  SourceLocation getUDSuffixLoc() const { return getRParenLoc(); }
+
+  /// getUDSuffix - Returns the ud-suffix specified for this literal.
+  const IdentifierInfo *getUDSuffix() const;
+
+  static bool classof(const Stmt *S) {
+    return S->getStmtClass() == UserDefinedLiteralClass;
+  }
+  static bool classof(const UserDefinedLiteral *) { return true; }
+
+  friend class ASTStmtReader;
+  friend class ASTStmtWriter;
+};
+
 /// CXXBoolLiteralExpr - [C++ 2.13.5] C++ Boolean Literal.
 ///
 class CXXBoolLiteralExpr : public Expr {
diff --git a/include/clang/AST/RecursiveASTVisitor.h b/include/clang/AST/RecursiveASTVisitor.h
index aeb9d0508f..38a6a8515a 100644
--- a/include/clang/AST/RecursiveASTVisitor.h
+++ b/include/clang/AST/RecursiveASTVisitor.h
@@ -2037,6 +2037,7 @@ DEF_TRAVERSE_STMT(CXXPseudoDestructorExpr, {
 })
 DEF_TRAVERSE_STMT(CXXThisExpr, { })
 DEF_TRAVERSE_STMT(CXXThrowExpr, { })
+DEF_TRAVERSE_STMT(UserDefinedLiteral, { })
 DEF_TRAVERSE_STMT(DesignatedInitExpr, { })
 DEF_TRAVERSE_STMT(ExtVectorElementExpr, { })
 DEF_TRAVERSE_STMT(GNUNullExpr, { })
diff --git a/include/clang/Basic/StmtNodes.td b/include/clang/Basic/StmtNodes.td
index 5018ac1901..8d2e8f53a6 100644
--- a/include/clang/Basic/StmtNodes.td
+++ b/include/clang/Basic/StmtNodes.td
@@ -98,6 +98,7 @@ def CXXReinterpretCastExpr : DStmt<CXXNamedCastExpr>;
 def CXXConstCastExpr : DStmt<CXXNamedCastExpr>;
 def CXXFunctionalCastExpr : DStmt<ExplicitCastExpr>;
 def CXXTypeidExpr : DStmt<Expr>;
+def UserDefinedLiteral : DStmt<CallExpr>;
 def CXXBoolLiteralExpr : DStmt<Expr>;
 def CXXNullPtrLiteralExpr : DStmt<Expr>;
 def CXXThisExpr : DStmt<Expr>;
diff --git a/include/clang/Sema/Sema.h b/include/clang/Sema/Sema.h
index bc7ecf5edd..ae4485c856 100644
--- a/include/clang/Sema/Sema.h
+++ b/include/clang/Sema/Sema.h
@@ -2545,6 +2545,11 @@ public:
                                       const DeclarationNameInfo &NameInfo,
                                       NamedDecl *D);
 
+  ExprResult BuildLiteralOperatorCall(IdentifierInfo *UDSuffix,
+                                      SourceLocation UDSuffixLoc,
+                                      ArrayRef<Expr*> Args,
+                                      SourceLocation LitEndLoc);
+
   ExprResult ActOnPredefinedExpr(SourceLocation Loc, tok::TokenKind Kind);
   ExprResult ActOnIntegerConstant(SourceLocation Loc, uint64_t Val);
   ExprResult ActOnNumericConstant(const Token &Tok);
diff --git a/include/clang/Serialization/ASTBitCodes.h b/include/clang/Serialization/ASTBitCodes.h
index 0af1d3b0d1..a25851e0d5 100644
--- a/include/clang/Serialization/ASTBitCodes.h
+++ b/include/clang/Serialization/ASTBitCodes.h
@@ -1136,6 +1136,8 @@ namespace clang {
       EXPR_CXX_CONST_CAST,
       /// \brief A CXXFunctionalCastExpr record.
       EXPR_CXX_FUNCTIONAL_CAST,
+      /// \brief A UserDefinedLiteral record.
+      EXPR_USER_DEFINED_LITERAL,
       /// \brief A CXXBoolLiteralExpr record.
       EXPR_CXX_BOOL_LITERAL,
       EXPR_CXX_NULL_PTR_LITERAL,  // CXXNullPtrLiteralExpr
diff --git a/lib/AST/Expr.cpp b/lib/AST/Expr.cpp
index e35091a101..0fdca5a33b 100644
--- a/lib/AST/Expr.cpp
+++ b/lib/AST/Expr.cpp
@@ -1681,7 +1681,8 @@ bool Expr::isUnusedResultAWarning(SourceLocation &Loc, SourceRange &R1,
     // Fallthrough for generic call handling.
   }
   case CallExprClass:
-  case CXXMemberCallExprClass: {
+  case CXXMemberCallExprClass:
+  case UserDefinedLiteralClass: {
     // If this is a direct call, get the callee.
     const CallExpr *CE = cast<CallExpr>(this);
     if (const Decl *FD = CE->getCalleeDecl()) {
@@ -2014,7 +2015,8 @@ Expr::CanThrowResult Expr::CanThrow(ASTContext &C) const {
     //     exception-specification
   case CallExprClass:
   case CXXMemberCallExprClass:
-  case CXXOperatorCallExprClass: {
+  case CXXOperatorCallExprClass:
+  case UserDefinedLiteralClass: {
     const CallExpr *CE = cast<CallExpr>(this);
     CanThrowResult CT;
     if (isTypeDependent())
diff --git a/lib/AST/ExprCXX.cpp b/lib/AST/ExprCXX.cpp
index dc559f0940..039d70cfc5 100644
--- a/lib/AST/ExprCXX.cpp
+++ b/lib/AST/ExprCXX.cpp
@@ -624,6 +624,39 @@ CXXFunctionalCastExpr::CreateEmpty(ASTContext &C, unsigned PathSize) {
   return new (Buffer) CXXFunctionalCastExpr(EmptyShell(), PathSize);
 }
 
+UserDefinedLiteral::LiteralOperatorKind
+UserDefinedLiteral::getLiteralOperatorKind() const {
+  if (getNumArgs() == 0)
+    return LOK_Template;
+  if (getNumArgs() == 2)
+    return LOK_String;
+
+  assert(getNumArgs() == 1 && "unexpected #args in literal operator call");
+  QualType ParamTy =
+    cast<FunctionDecl>(getCalleeDecl())->getParamDecl(0)->getType();
+  if (ParamTy->isPointerType())
+    return LOK_Raw;
+  if (ParamTy->isAnyCharacterType())
+    return LOK_Character;
+  if (ParamTy->isIntegerType())
+    return LOK_Integer;
+  if (ParamTy->isFloatingType())
+    return LOK_Floating;
+
+  llvm_unreachable("unknown kind of literal operator");
+}
+
+Expr *UserDefinedLiteral::getCookedLiteral() {
+#ifndef NDEBUG
+  LiteralOperatorKind LOK = getLiteralOperatorKind();
+  assert(LOK != LOK_Template && LOK != LOK_Raw && "not a cooked literal");
+#endif
+  return getArg(0);
+}
+
+const IdentifierInfo *UserDefinedLiteral::getUDSuffix() const {
+  return cast<FunctionDecl>(getCalleeDecl())->getLiteralIdentifier();
+}
 
 CXXDefaultArgExpr *
 CXXDefaultArgExpr::Create(ASTContext &C, SourceLocation Loc, 
diff --git a/lib/AST/ExprClassification.cpp b/lib/AST/ExprClassification.cpp
index 693e28c8a4..00160a0073 100644
--- a/lib/AST/ExprClassification.cpp
+++ b/lib/AST/ExprClassification.cpp
@@ -269,6 +269,7 @@ static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {
   case Expr::CallExprClass:
   case Expr::CXXOperatorCallExprClass:
   case Expr::CXXMemberCallExprClass:
+  case Expr::UserDefinedLiteralClass:
   case Expr::CUDAKernelCallExprClass:
     return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType());
 
diff --git a/lib/AST/ExprConstant.cpp b/lib/AST/ExprConstant.cpp
index 08794f355f..947f661c2c 100644
--- a/lib/AST/ExprConstant.cpp
+++ b/lib/AST/ExprConstant.cpp
@@ -6243,6 +6243,7 @@ static ICEDiag CheckICE(const Expr* E, ASTContext &Ctx) {
   case Expr::CXXTypeidExprClass:
   case Expr::CXXUuidofExprClass:
   case Expr::CXXNullPtrLiteralExprClass:
+  case Expr::UserDefinedLiteralClass:
   case Expr::CXXThisExprClass:
   case Expr::CXXThrowExprClass:
   case Expr::CXXNewExprClass:
diff --git a/lib/AST/ItaniumMangle.cpp b/lib/AST/ItaniumMangle.cpp
index ea6e8b2e23..c4eed7c34d 100644
--- a/lib/AST/ItaniumMangle.cpp
+++ b/lib/AST/ItaniumMangle.cpp
@@ -2439,6 +2439,9 @@ recurse:
                      Arity);
     break;
 
+  case Expr::UserDefinedLiteralClass:
+    // We follow g++'s approach of mangling a UDL as a call to the literal
+    // operator.
   case Expr::CXXMemberCallExprClass: // fallthrough
   case Expr::CallExprClass: {
     const CallExpr *CE = cast<CallExpr>(E);
diff --git a/lib/AST/StmtPrinter.cpp b/lib/AST/StmtPrinter.cpp
index cd8b6bb5c2..b8e68d8574 100644
--- a/lib/AST/StmtPrinter.cpp
+++ b/lib/AST/StmtPrinter.cpp
@@ -1222,6 +1222,31 @@ void StmtPrinter::VisitCXXUuidofExpr(CXXUuidofExpr *Node) {
   OS << ")";
 }
 
+void StmtPrinter::VisitUserDefinedLiteral(UserDefinedLiteral *Node) {
+  switch (Node->getLiteralOperatorKind()) {
+  case UserDefinedLiteral::LOK_Raw:
+    OS << cast<StringLiteral>(Node->getArg(0))->getString();
+    break;
+  case UserDefinedLiteral::LOK_Template: {
+    DeclRefExpr *DRE = cast<DeclRefExpr>(Node->getCallee());
+    assert(DRE->hasExplicitTemplateArgs());
+    const TemplateArgumentLoc *Args = DRE->getTemplateArgs();
+    for (unsigned i = 0, e = DRE->getNumTemplateArgs(); i != e; ++i) {
+      char C = (char)Args[i].getArgument().getAsIntegral()->getZExtValue();
+      OS << C;
+    }
+    break;
+  }
+  case UserDefinedLiteral::LOK_Integer:
+  case UserDefinedLiteral::LOK_Floating:
+  case UserDefinedLiteral::LOK_String:
+  case UserDefinedLiteral::LOK_Character:
+    PrintExpr(Node->getCookedLiteral());
+    break;
+  }
+  OS << Node->getUDSuffix()->getName();
+}
+
 void StmtPrinter::VisitCXXBoolLiteralExpr(CXXBoolLiteralExpr *Node) {
   OS << (Node->getValue() ? "true" : "false");
 }
diff --git a/lib/AST/StmtProfile.cpp b/lib/AST/StmtProfile.cpp
index 7935d6d44d..db27f821f5 100644
--- a/lib/AST/StmtProfile.cpp
+++ b/lib/AST/StmtProfile.cpp
@@ -738,6 +738,10 @@ void StmtProfiler::VisitCXXConstCastExpr(const CXXConstCastExpr *S) {
   VisitCXXNamedCastExpr(S);
 }
 
+void StmtProfiler::VisitUserDefinedLiteral(const UserDefinedLiteral *S) {
+  VisitCallExpr(S);
+}
+
 void StmtProfiler::VisitCXXBoolLiteralExpr(const CXXBoolLiteralExpr *S) {
   VisitExpr(S);
   ID.AddBoolean(S->getValue());
diff --git a/lib/Analysis/CFG.cpp b/lib/Analysis/CFG.cpp
index b06cf44344..f50cc31e9d 100644
--- a/lib/Analysis/CFG.cpp
+++ b/lib/Analysis/CFG.cpp
@@ -935,6 +935,7 @@ CFGBlock *CFGBuilder::Visit(Stmt * S, AddStmtChoice asc) {
     case Stmt::CallExprClass:
     case Stmt::CXXOperatorCallExprClass:
     case Stmt::CXXMemberCallExprClass:
+    case Stmt::UserDefinedLiteralClass:
       return VisitCallExpr(cast<CallExpr>(S), asc);
 
     case Stmt::CaseStmtClass:
diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 18aa0fc431..9def5543a8 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -656,6 +656,7 @@ LValue CodeGenFunction::EmitLValue(const Expr *E) {
   case Expr::CallExprClass:
   case Expr::CXXMemberCallExprClass:
   case Expr::CXXOperatorCallExprClass:
+  case Expr::UserDefinedLiteralClass:
     return EmitCallExprLValue(cast<CallExpr>(E));
   case Expr::VAArgExprClass:
     return EmitVAArgExprLValue(cast<VAArgExpr>(E));
diff --git a/lib/Sema/SemaExpr.cpp b/lib/Sema/SemaExpr.cpp
index 6b753a1342..7d99732e68 100644
--- a/lib/Sema/SemaExpr.cpp
+++ b/lib/Sema/SemaExpr.cpp
@@ -1172,10 +1172,27 @@ Sema::ActOnStringLiteral(const Token *StringToks, unsigned NumStringToks) {
                                        ArrayType::Normal, 0);
 
   // Pass &StringTokLocs[0], StringTokLocs.size() to factory!
-  return Owned(StringLiteral::Create(Context, Literal.GetString(),
-                                     Kind, Literal.Pascal, StrTy,
-                                     &StringTokLocs[0],
-                                     StringTokLocs.size()));
+  StringLiteral *Lit = StringLiteral::Create(Context, Literal.GetString(),
+                                             Kind, Literal.Pascal, StrTy,
+                                             &StringTokLocs[0],
+                                             StringTokLocs.size());
+  if (Literal.getUDSuffix().empty())
+    return Owned(Lit);
+
+  // We're building a user-defined literal.
+  IdentifierInfo *UDSuffix = &Context.Idents.get(Literal.getUDSuffix());
+  SourceLocation UDSuffixLoc = StringTokLocs[0];
+  // FIXME: = Literal.getUDSuffixLoc(getSourceManager());
+
+  // C++11 [lex.ext]p5: The literal L is treated as a call of the form
+  //   operator "" X (str, len)
+  QualType SizeType = Context.getSizeType();
+  llvm::APInt Len(Context.getIntWidth(SizeType), Literal.GetNumStringChars());
+  IntegerLiteral *LenArg = IntegerLiteral::Create(Context, Len, SizeType,
+                                                  StringTokLocs[0]);
+  Expr *Args[] = { Lit, LenArg };
+  return BuildLiteralOperatorCall(UDSuffix, UDSuffixLoc, Args,
+                                  StringTokLocs.back());
 }
 
 ExprResult
diff --git a/lib/Sema/SemaOverload.cpp b/lib/Sema/SemaOverload.cpp
index 91e8defcd4..14c773fdb4 100644
--- a/lib/Sema/SemaOverload.cpp
+++ b/lib/Sema/SemaOverload.cpp
@@ -10895,6 +10895,109 @@ Sema::BuildOverloadedArrowExpr(Scope *S, Expr *Base, SourceLocation OpLoc) {
   return MaybeBindToTemporary(TheCall);
 }
 
+static void FilterLookupForLiteralOperator(Sema &S, LookupResult &R,
+                                           ArrayRef<Expr*> Args) {
+  LookupResult::Filter F = R.makeFilter();
+
+  while (F.hasNext()) {
+    FunctionDecl *D = dyn_cast<FunctionDecl>(F.next());
+    // FIXME: using-decls?
+
+    if (!D || D->getNumParams() != Args.size()) {
+      F.erase();
+    } else {
+      // The literal operator's parameter types must exactly match the decayed
+      // argument types.
+      for (unsigned ArgIdx = 0; ArgIdx != Args.size(); ++ArgIdx) {
+        QualType ArgTy = Args[ArgIdx]->getType();
+        QualType ParamTy = D->getParamDecl(ArgIdx)->getType();
+        if (ArgTy->isArrayType())
+          ArgTy = S.Context.getArrayDecayedType(ArgTy);
+        if (!S.Context.hasSameUnqualifiedType(ArgTy, ParamTy)) {
+          F.erase();
+          break;
+        }
+      }
+    }
+  }
+
+  F.done();
+}
+
+/// BuildLiteralOperatorCall - A user-defined literal was found. Look up the
+/// corresponding literal operator, and build a call to it.
+/// FIXME: Support for raw literal operators and literal operator templates.
+ExprResult
+Sema::BuildLiteralOperatorCall(IdentifierInfo *UDSuffix,
+                               SourceLocation UDSuffixLoc,
+                               ArrayRef<Expr*> Args, SourceLocation LitEndLoc) {
+  DeclarationName OpName =
+    Context.DeclarationNames.getCXXLiteralOperatorName(UDSuffix);
+  DeclarationNameInfo OpNameInfo(OpName, UDSuffixLoc);
+  OpNameInfo.setCXXLiteralOperatorNameLoc(UDSuffixLoc);
+
+  LookupResult R(*this, OpName, UDSuffixLoc, LookupOrdinaryName);
+  LookupName(R, /*FIXME*/CurScope);
+  assert(R.getResultKind() != LookupResult::Ambiguous &&
+         "literal operator lookup can't be ambiguous");
+
+  // Filter the lookup results appropriately.
+  FilterLookupForLiteralOperator(*this, R, Args);
+
+  // FIXME: For literal operator templates, we need to perform overload
+  // resolution to deal with SFINAE.
+  FunctionDecl *FD = R.getAsSingle<FunctionDecl>();
+  if (!FD || FD->getNumParams() != Args.size())
+    return ExprError(
+        Diag(UDSuffixLoc, diag::err_ovl_no_viable_oper) << UDSuffix->getName());
+  bool HadMultipleCandidates = false;
+
+  // Check the argument types. This should almost always be a no-op, except
+  // that array-to-pointer decay is applied to string literals.
+  assert(Args.size() <= 2 && "too many arguments for literal operator");
+  Expr *ConvArgs[2];
+  for (unsigned ArgIdx = 0; ArgIdx != Args.size(); ++ArgIdx) {
+    ExprResult InputInit = PerformCopyInitialization(
+      InitializedEntity::InitializeParameter(Context, FD->getParamDecl(ArgIdx)),
+      SourceLocation(), Args[ArgIdx]);
+    if (InputInit.isInvalid())
+      return true;
+    ConvArgs[ArgIdx] = InputInit.take();
+  }
+
+  MarkFunctionReferenced(UDSuffixLoc, FD);
+  DiagnoseUseOfDecl(FD, UDSuffixLoc);
+
+  ExprResult Fn = CreateFunctionRefExpr(*this, FD, HadMultipleCandidates,
+                                        OpNameInfo.getLoc(),
+                                        OpNameInfo.getInfo());
+  if (Fn.isInvalid())
+    return true;
+
+  QualType ResultTy = FD->getResultType();
+  ExprValueKind VK = Expr::getValueKindForType(ResultTy);
+  ResultTy = ResultTy.getNonLValueExprType(Context);
+
+  // FIXME: A literal operator call never uses default arguments.
+  // But is this ambiguous?
+  //   void operator"" _x(const char *p);
+  //   void operator"" _x(const char *p, size_t n = 0);
+  //   123_x
+  // g++ says no, but bizarrely rejects it if the default argument is omitted.
+
+  UserDefinedLiteral *UDL =
+    new (Context) UserDefinedLiteral(Context, Fn.take(), ConvArgs, Args.size(),
+                                     ResultTy, VK, LitEndLoc, UDSuffixLoc);
+
+  if (CheckCallReturnType(FD->getResultType(), UDSuffixLoc, UDL, FD))
+    return ExprError();
+
+  if (CheckFunctionCall(FD, UDL))
+    return ExprError();
+
+  return MaybeBindToTemporary(UDL);
+}
+
 /// FixOverloadedFunctionReference - E is an expression that refers to
 /// a C++ overloaded function (possibly with some parentheses and
 /// perhaps a '&' around it). We have resolved the overloaded function
diff --git a/lib/Sema/TreeTransform.h b/lib/Sema/TreeTransform.h
index 0a0f5c7c32..8d4d934402 100644
--- a/lib/Sema/TreeTransform.h
+++ b/lib/Sema/TreeTransform.h
@@ -6088,6 +6088,12 @@ TreeTransform<Derived>::TransformCharacterLiteral(CharacterLiteral *E) {
 
 template<typename Derived>
 ExprResult
+TreeTransform<Derived>::TransformUserDefinedLiteral(UserDefinedLiteral *E) {
+  return SemaRef.MaybeBindToTemporary(E);
+}
+
+template<typename Derived>
+ExprResult
 TreeTransform<Derived>::TransformGenericSelectionExpr(GenericSelectionExpr *E) {
   ExprResult ControllingExpr =
     getDerived().TransformExpr(E->getControllingExpr());
diff --git a/lib/Serialization/ASTReaderStmt.cpp b/lib/Serialization/ASTReaderStmt.cpp
index 479805e7e5..a0d7e457e0 100644
--- a/lib/Serialization/ASTReaderStmt.cpp
+++ b/lib/Serialization/ASTReaderStmt.cpp
@@ -1161,6 +1161,11 @@ void ASTStmtReader::VisitCXXFunctionalCastExpr(CXXFunctionalCastExpr *E) {
   E->setRParenLoc(ReadSourceLocation(Record, Idx));
 }
 
+void ASTStmtReader::VisitUserDefinedLiteral(UserDefinedLiteral *E) {
+  VisitCallExpr(E);
+  E->UDSuffixLoc = ReadSourceLocation(Record, Idx);
+}
+
 void ASTStmtReader::VisitCXXBoolLiteralExpr(CXXBoolLiteralExpr *E) {
   VisitExpr(E);
   E->setValue(Record[Idx++]);
@@ -2029,6 +2034,10 @@ Stmt *ASTReader::ReadStmtFromStream(ModuleFile &F) {
                        /*PathSize*/ Record[ASTStmtReader::NumExprFields]);
       break;
 
+    case EXPR_USER_DEFINED_LITERAL:
+      S = new (Context) UserDefinedLiteral(Context, Empty);
+      break;
+
     case EXPR_CXX_BOOL_LITERAL:
       S = new (Context) CXXBoolLiteralExpr(Empty);
       break;
diff --git a/lib/Serialization/ASTWriter.cpp b/lib/Serialization/ASTWriter.cpp
index 4edfbff288..8b6859cd42 100644
--- a/lib/Serialization/ASTWriter.cpp
+++ b/lib/Serialization/ASTWriter.cpp
@@ -720,6 +720,7 @@ static void AddStmtsExprs(llvm::BitstreamWriter &Stream,
   RECORD(EXPR_CXX_REINTERPRET_CAST);
   RECORD(EXPR_CXX_CONST_CAST);
   RECORD(EXPR_CXX_FUNCTIONAL_CAST);
+  RECORD(EXPR_USER_DEFINED_LITERAL);
   RECORD(EXPR_CXX_BOOL_LITERAL);
   RECORD(EXPR_CXX_NULL_PTR_LITERAL);
   RECORD(EXPR_CXX_TYPEID_EXPR);
diff --git a/lib/Serialization/ASTWriterStmt.cpp b/lib/Serialization/ASTWriterStmt.cpp
index 76bbc850c2..a59f2b6a77 100644
--- a/lib/Serialization/ASTWriterStmt.cpp
+++ b/lib/Serialization/ASTWriterStmt.cpp
@@ -1144,6 +1144,12 @@ void ASTStmtWriter::VisitCXXFunctionalCastExpr(CXXFunctionalCastExpr *E) {
   Code = serialization::EXPR_CXX_FUNCTIONAL_CAST;
 }
 
+void ASTStmtWriter::VisitUserDefinedLiteral(UserDefinedLiteral *E) {
+  VisitCallExpr(E);
+  Writer.AddSourceLocation(E->UDSuffixLoc, Record);
+  Code = serialization::EXPR_USER_DEFINED_LITERAL;
+}
+
 void ASTStmtWriter::VisitCXXBoolLiteralExpr(CXXBoolLiteralExpr *E) {
   VisitExpr(E);
   Record.push_back(E->getValue());
diff --git a/lib/StaticAnalyzer/Core/ExprEngine.cpp b/lib/StaticAnalyzer/Core/ExprEngine.cpp
index 408bcd3528..d19cc9c7d3 100644
--- a/lib/StaticAnalyzer/Core/ExprEngine.cpp
+++ b/lib/StaticAnalyzer/Core/ExprEngine.cpp
@@ -712,7 +712,8 @@ void ExprEngine::Visit(const Stmt *S, ExplodedNode *Pred,
 
     case Stmt::CallExprClass:
     case Stmt::CXXOperatorCallExprClass:
-    case Stmt::CXXMemberCallExprClass: {
+    case Stmt::CXXMemberCallExprClass:
+    case Stmt::UserDefinedLiteralClass: {
       Bldr.takeNodes(Pred);
       VisitCallExpr(cast<CallExpr>(S), Pred, Dst);
       Bldr.addNodes(Dst);
diff --git a/test/CXX/lex/lex.literal/lex.ext/p10.cpp b/test/CXX/lex/lex.literal/lex.ext/p10.cpp
index 7fbd9f8e4b..6652c9a890 100644
--- a/test/CXX/lex/lex.literal/lex.ext/p10.cpp
+++ b/test/CXX/lex/lex.literal/lex.ext/p10.cpp
@@ -10,6 +10,6 @@ void f() {
   // FIXME: Reject these for the right reason.
   123wibble; // expected-error {{suffix 'wibble'}}
   123.0wibble; // expected-error {{suffix 'wibble'}}
-  ""wibble; // expected-warning {{unused}}
-  R"x("hello")x"wibble; // expected-warning {{unused}}
+  ""wibble;
+  R"x("hello")x"wibble;
 }
diff --git a/test/CXX/lex/lex.literal/lex.ext/p8.cpp b/test/CXX/lex/lex.literal/lex.ext/p8.cpp
index 2833769d73..d9078221ff 100644
--- a/test/CXX/lex/lex.literal/lex.ext/p8.cpp
+++ b/test/CXX/lex/lex.literal/lex.ext/p8.cpp
@@ -1,6 +1,7 @@
 // RUN: %clang_cc1 -std=c++11 -verify %s
 
-constexpr const char *operator "" _id(const char *p) { return p; }
+using size_t = decltype(sizeof(int));
+constexpr const char *operator "" _id(const char *p, size_t) { return p; }
 constexpr const char *s = "foo"_id "bar" "baz"_id "quux";
 
 constexpr bool streq(const char *p, const char *q) {
@@ -8,12 +9,10 @@ constexpr bool streq(const char *p, const char *q) {
 }
 static_assert(streq(s, "foobarbazquux"), "");
 
-constexpr const char *operator "" _trim(const char *p) {
-  return *p == ' ' ? operator "" _trim(p + 1) : p;
+constexpr const char *operator "" _trim(const char *p, size_t n) {
+  return *p == ' ' ? operator "" _trim(p + 1, n - 1) : p;
 }
 constexpr const char *t = "   " " "_trim "  foo";
-// FIXME: once we implement the semantics of user-defined literals, this should
-// pass.
-static_assert(streq(s, "foo"), ""); // expected-error {{static_assert}}
+static_assert(streq(t, "foo"), "");
 
 const char *u = "foo" "bar"_id "baz" "quux"_di "corge"; // expected-error {{differing user-defined suffixes ('_id' and '_di') in string literal concatenation}}
diff --git a/test/CXX/lex/lex.literal/lex.ext/p9.cpp b/test/CXX/lex/lex.literal/lex.ext/p9.cpp
index e3de34df9e..65e27b41b0 100644
--- a/test/CXX/lex/lex.literal/lex.ext/p9.cpp
+++ b/test/CXX/lex/lex.literal/lex.ext/p9.cpp
@@ -6,9 +6,7 @@ void operator "" _x(const wchar_t *, size_t);
 namespace std_example {
 
 int main() {
-  // FIXME: once we implement the semantics of literal operators, this warning
-  // should vanish.
-  L"A" "B" "C"_x; // expected-warning {{expression result unused}}
+  L"A" "B" "C"_x;
   "P"_x "Q" "R"_y; // expected-error {{differing user-defined suffixes ('_x' and '_y') in string literal concatenation}}
 }
 
diff --git a/test/CodeGenCXX/cxx11-user-defined-literal.cpp b/test/CodeGenCXX/cxx11-user-defined-literal.cpp
new file mode 100644
index 0000000000..fbd3621014
--- /dev/null
+++ b/test/CodeGenCXX/cxx11-user-defined-literal.cpp
@@ -0,0 +1,35 @@
+// RUN: %clang_cc1 -std=c++11 -triple x86_64-linux-gnu -emit-llvm %s -o - | FileCheck %s
+
+struct S { S(); ~S(); S(const S &); void operator()(int); };
+using size_t = decltype(sizeof(int));
+S operator"" _x(const char *, size_t);
+
+void f() {
+  // CHECK: call void @_Zli2_xPKcm({{.*}}, i8* getelementptr inbounds ([4 x i8]* @{{.*}}, i32 0, i32 0), i64 3)
+  // CHECK: call void @_Zli2_xPKcm({{.*}}, i8* getelementptr inbounds ([4 x i8]* @{{.*}}, i32 0, i32 0), i64 3)
+  // CHECK: call void @_ZN1SD1Ev({{.*}}) nounwind
+  // CHECK: call void @_ZN1SD1Ev({{.*}}) nounwind
+  "foo"_x, "bar"_x;
+}
+
+template<typename T> auto g(T t) -> decltype("foo"_x(t)) { return "foo"_x(t); }
+template<typename T> auto i(T t) -> decltype(operator"" _x("foo", 3)(t)) { return operator"" _x("foo", 3)(t); }
+
+void h() {
+  g(42);
+  i(42);
+}
+
+// CHECK: define {{.*}} @_Z1hv()
+// CHECK:   call void @_Z1gIiEDTclclL_Zli2_xPKcmELA4_S0_ELm3EEfp_EET_(i32 42)
+// CHECK:   call void @_Z1iIiEDTclclL_Zli2_xPKcmELA4_S0_ELi3EEfp_EET_(i32 42)
+
+// CHECK: define {{.*}} @_Z1gIiEDTclclL_Zli2_xPKcmELA4_S0_ELm3EEfp_EET_(i32
+// CHECK:   call void @_Zli2_xPKcm({{.*}}, i8* getelementptr inbounds ([4 x i8]* @{{.*}}, i32 0, i32 0), i64 3)
+// CHECK:   call void @_ZN1SclEi
+// CHECK:   call void @_ZN1SD1Ev
+
+// CHECK: define {{.*}} @_Z1iIiEDTclclL_Zli2_xPKcmELA4_S0_ELi3EEfp_EET_(i32
+// CHECK:   call void @_Zli2_xPKcm({{.*}}, i8* getelementptr inbounds ([4 x i8]* @{{.*}}, i32 0, i32 0), i64 3)
+// CHECK:   call void @_ZN1SclEi
+// CHECK:   call void @_ZN1SD1Ev
diff --git a/test/PCH/cxx11-user-defined-literals.cpp b/test/PCH/cxx11-user-defined-literals.cpp
new file mode 100644
index 0000000000..4a7c24b994
--- /dev/null
+++ b/test/PCH/cxx11-user-defined-literals.cpp
@@ -0,0 +1,21 @@
+// RUN: %clang_cc1 -pedantic-errors -std=c++11 -emit-pch %s -o %t
+// RUN: %clang_cc1 -pedantic-errors -std=c++11 -include-pch %t -verify %s
+
+#ifndef HEADER_INCLUDED
+
+#define HEADER_INCLUDED
+
+using size_t = decltype(sizeof(int));
+int operator"" _foo(const char *p, size_t);
+
+template<typename T> auto f(T t) -> decltype(t + ""_foo) { return 0;