1210008Srdivacky//===--- ExprClassification.cpp - Expression AST Node Implementation ------===// 2210008Srdivacky// 3210008Srdivacky// The LLVM Compiler Infrastructure 4210008Srdivacky// 5210008Srdivacky// This file is distributed under the University of Illinois Open Source 6210008Srdivacky// License. See LICENSE.TXT for details. 7210008Srdivacky// 8210008Srdivacky//===----------------------------------------------------------------------===// 9210008Srdivacky// 10210008Srdivacky// This file implements Expr::classify. 11210008Srdivacky// 12210008Srdivacky//===----------------------------------------------------------------------===// 13210008Srdivacky 14210008Srdivacky#include "clang/AST/Expr.h" 15210008Srdivacky#include "clang/AST/ASTContext.h" 16249423Sdim#include "clang/AST/DeclCXX.h" 17210008Srdivacky#include "clang/AST/DeclObjC.h" 18210008Srdivacky#include "clang/AST/DeclTemplate.h" 19249423Sdim#include "clang/AST/ExprCXX.h" 20249423Sdim#include "clang/AST/ExprObjC.h" 21249423Sdim#include "llvm/Support/ErrorHandling.h" 22210008Srdivackyusing namespace clang; 23210008Srdivacky 24210008Srdivackytypedef Expr::Classification Cl; 25210008Srdivacky 26210008Srdivackystatic Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E); 27210008Srdivackystatic Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D); 28210008Srdivackystatic Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T); 29210008Srdivackystatic Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E); 30210008Srdivackystatic Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E); 31210008Srdivackystatic Cl::Kinds ClassifyConditional(ASTContext &Ctx, 32218893Sdim const Expr *trueExpr, 33218893Sdim const Expr *falseExpr); 34210008Srdivackystatic Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 35210008Srdivacky Cl::Kinds Kind, SourceLocation &Loc); 36210008Srdivacky 37210008SrdivackyCl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const { 38210008Srdivacky assert(!TR->isReferenceType() && "Expressions can't have reference type."); 39210008Srdivacky 40210008Srdivacky Cl::Kinds kind = ClassifyInternal(Ctx, this); 41210008Srdivacky // C99 6.3.2.1: An lvalue is an expression with an object type or an 42210008Srdivacky // incomplete type other than void. 43234353Sdim if (!Ctx.getLangOpts().CPlusPlus) { 44210008Srdivacky // Thus, no functions. 45210008Srdivacky if (TR->isFunctionType() || TR == Ctx.OverloadTy) 46210008Srdivacky kind = Cl::CL_Function; 47210008Srdivacky // No void either, but qualified void is OK because it is "other than void". 48221345Sdim // Void "lvalues" are classified as addressable void values, which are void 49221345Sdim // expressions whose address can be taken. 50221345Sdim else if (TR->isVoidType() && !TR.hasQualifiers()) 51221345Sdim kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void); 52210008Srdivacky } 53210008Srdivacky 54218893Sdim // Enable this assertion for testing. 55218893Sdim switch (kind) { 56218893Sdim case Cl::CL_LValue: assert(getValueKind() == VK_LValue); break; 57218893Sdim case Cl::CL_XValue: assert(getValueKind() == VK_XValue); break; 58218893Sdim case Cl::CL_Function: 59218893Sdim case Cl::CL_Void: 60221345Sdim case Cl::CL_AddressableVoid: 61218893Sdim case Cl::CL_DuplicateVectorComponents: 62218893Sdim case Cl::CL_MemberFunction: 63218893Sdim case Cl::CL_SubObjCPropertySetting: 64218893Sdim case Cl::CL_ClassTemporary: 65239462Sdim case Cl::CL_ArrayTemporary: 66221345Sdim case Cl::CL_ObjCMessageRValue: 67218893Sdim case Cl::CL_PRValue: assert(getValueKind() == VK_RValue); break; 68218893Sdim } 69218893Sdim 70210008Srdivacky Cl::ModifiableType modifiable = Cl::CM_Untested; 71210008Srdivacky if (Loc) 72210008Srdivacky modifiable = IsModifiable(Ctx, this, kind, *Loc); 73210008Srdivacky return Classification(kind, modifiable); 74210008Srdivacky} 75210008Srdivacky 76239462Sdim/// Classify an expression which creates a temporary, based on its type. 77239462Sdimstatic Cl::Kinds ClassifyTemporary(QualType T) { 78239462Sdim if (T->isRecordType()) 79239462Sdim return Cl::CL_ClassTemporary; 80239462Sdim if (T->isArrayType()) 81239462Sdim return Cl::CL_ArrayTemporary; 82239462Sdim 83239462Sdim // No special classification: these don't behave differently from normal 84239462Sdim // prvalues. 85239462Sdim return Cl::CL_PRValue; 86239462Sdim} 87239462Sdim 88249423Sdimstatic Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang, 89249423Sdim const Expr *E, 90249423Sdim ExprValueKind Kind) { 91249423Sdim switch (Kind) { 92249423Sdim case VK_RValue: 93249423Sdim return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue; 94249423Sdim case VK_LValue: 95249423Sdim return Cl::CL_LValue; 96249423Sdim case VK_XValue: 97249423Sdim return Cl::CL_XValue; 98249423Sdim } 99249423Sdim llvm_unreachable("Invalid value category of implicit cast."); 100249423Sdim} 101249423Sdim 102210008Srdivackystatic Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) { 103210008Srdivacky // This function takes the first stab at classifying expressions. 104234353Sdim const LangOptions &Lang = Ctx.getLangOpts(); 105210008Srdivacky 106210008Srdivacky switch (E->getStmtClass()) { 107218893Sdim case Stmt::NoStmtClass: 108218893Sdim#define ABSTRACT_STMT(Kind) 109218893Sdim#define STMT(Kind, Base) case Expr::Kind##Class: 110218893Sdim#define EXPR(Kind, Base) 111218893Sdim#include "clang/AST/StmtNodes.inc" 112218893Sdim llvm_unreachable("cannot classify a statement"); 113234353Sdim 114234353Sdim // First come the expressions that are always lvalues, unconditionally. 115210008Srdivacky case Expr::ObjCIsaExprClass: 116210008Srdivacky // C++ [expr.prim.general]p1: A string literal is an lvalue. 117210008Srdivacky case Expr::StringLiteralClass: 118210008Srdivacky // @encode is equivalent to its string 119210008Srdivacky case Expr::ObjCEncodeExprClass: 120210008Srdivacky // __func__ and friends are too. 121210008Srdivacky case Expr::PredefinedExprClass: 122210008Srdivacky // Property references are lvalues 123234353Sdim case Expr::ObjCSubscriptRefExprClass: 124210008Srdivacky case Expr::ObjCPropertyRefExprClass: 125210008Srdivacky // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of... 126210008Srdivacky case Expr::CXXTypeidExprClass: 127210008Srdivacky // Unresolved lookups get classified as lvalues. 128210008Srdivacky // FIXME: Is this wise? Should they get their own kind? 129210008Srdivacky case Expr::UnresolvedLookupExprClass: 130210008Srdivacky case Expr::UnresolvedMemberExprClass: 131218893Sdim case Expr::CXXDependentScopeMemberExprClass: 132218893Sdim case Expr::DependentScopeDeclRefExprClass: 133210008Srdivacky // ObjC instance variables are lvalues 134210008Srdivacky // FIXME: ObjC++0x might have different rules 135210008Srdivacky case Expr::ObjCIvarRefExprClass: 136243830Sdim case Expr::FunctionParmPackExprClass: 137251662Sdim case Expr::MSPropertyRefExprClass: 138218893Sdim return Cl::CL_LValue; 139234353Sdim 140210008Srdivacky // C99 6.5.2.5p5 says that compound literals are lvalues. 141239462Sdim // In C++, they're prvalue temporaries. 142210008Srdivacky case Expr::CompoundLiteralExprClass: 143239462Sdim return Ctx.getLangOpts().CPlusPlus ? ClassifyTemporary(E->getType()) 144239462Sdim : Cl::CL_LValue; 145210008Srdivacky 146218893Sdim // Expressions that are prvalues. 147218893Sdim case Expr::CXXBoolLiteralExprClass: 148218893Sdim case Expr::CXXPseudoDestructorExprClass: 149221345Sdim case Expr::UnaryExprOrTypeTraitExprClass: 150218893Sdim case Expr::CXXNewExprClass: 151218893Sdim case Expr::CXXThisExprClass: 152218893Sdim case Expr::CXXNullPtrLiteralExprClass: 153218893Sdim case Expr::ImaginaryLiteralClass: 154218893Sdim case Expr::GNUNullExprClass: 155218893Sdim case Expr::OffsetOfExprClass: 156218893Sdim case Expr::CXXThrowExprClass: 157218893Sdim case Expr::ShuffleVectorExprClass: 158263508Sdim case Expr::ConvertVectorExprClass: 159218893Sdim case Expr::IntegerLiteralClass: 160218893Sdim case Expr::CharacterLiteralClass: 161218893Sdim case Expr::AddrLabelExprClass: 162218893Sdim case Expr::CXXDeleteExprClass: 163218893Sdim case Expr::ImplicitValueInitExprClass: 164218893Sdim case Expr::BlockExprClass: 165218893Sdim case Expr::FloatingLiteralClass: 166218893Sdim case Expr::CXXNoexceptExprClass: 167218893Sdim case Expr::CXXScalarValueInitExprClass: 168218893Sdim case Expr::UnaryTypeTraitExprClass: 169218893Sdim case Expr::BinaryTypeTraitExprClass: 170234353Sdim case Expr::TypeTraitExprClass: 171221345Sdim case Expr::ArrayTypeTraitExprClass: 172221345Sdim case Expr::ExpressionTraitExprClass: 173218893Sdim case Expr::ObjCSelectorExprClass: 174218893Sdim case Expr::ObjCProtocolExprClass: 175218893Sdim case Expr::ObjCStringLiteralClass: 176239462Sdim case Expr::ObjCBoxedExprClass: 177234353Sdim case Expr::ObjCArrayLiteralClass: 178234353Sdim case Expr::ObjCDictionaryLiteralClass: 179234353Sdim case Expr::ObjCBoolLiteralExprClass: 180218893Sdim case Expr::ParenListExprClass: 181218893Sdim case Expr::SizeOfPackExprClass: 182218893Sdim case Expr::SubstNonTypeTemplateParmPackExprClass: 183223017Sdim case Expr::AsTypeExprClass: 184224145Sdim case Expr::ObjCIndirectCopyRestoreExprClass: 185226633Sdim case Expr::AtomicExprClass: 186218893Sdim return Cl::CL_PRValue; 187218893Sdim 188210008Srdivacky // Next come the complicated cases. 189224145Sdim case Expr::SubstNonTypeTemplateParmExprClass: 190224145Sdim return ClassifyInternal(Ctx, 191224145Sdim cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement()); 192210008Srdivacky 193210008Srdivacky // C++ [expr.sub]p1: The result is an lvalue of type "T". 194210008Srdivacky // However, subscripting vector types is more like member access. 195210008Srdivacky case Expr::ArraySubscriptExprClass: 196210008Srdivacky if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType()) 197210008Srdivacky return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase()); 198210008Srdivacky return Cl::CL_LValue; 199210008Srdivacky 200210008Srdivacky // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a 201210008Srdivacky // function or variable and a prvalue otherwise. 202210008Srdivacky case Expr::DeclRefExprClass: 203221345Sdim if (E->getType() == Ctx.UnknownAnyTy) 204221345Sdim return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl()) 205221345Sdim ? Cl::CL_PRValue : Cl::CL_LValue; 206210008Srdivacky return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl()); 207210008Srdivacky 208210008Srdivacky // Member access is complex. 209210008Srdivacky case Expr::MemberExprClass: 210210008Srdivacky return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E)); 211210008Srdivacky 212210008Srdivacky case Expr::UnaryOperatorClass: 213210008Srdivacky switch (cast<UnaryOperator>(E)->getOpcode()) { 214210008Srdivacky // C++ [expr.unary.op]p1: The unary * operator performs indirection: 215210008Srdivacky // [...] the result is an lvalue referring to the object or function 216210008Srdivacky // to which the expression points. 217212904Sdim case UO_Deref: 218210008Srdivacky return Cl::CL_LValue; 219210008Srdivacky 220210008Srdivacky // GNU extensions, simply look through them. 221212904Sdim case UO_Extension: 222210008Srdivacky return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr()); 223210008Srdivacky 224218893Sdim // Treat _Real and _Imag basically as if they were member 225218893Sdim // expressions: l-value only if the operand is a true l-value. 226218893Sdim case UO_Real: 227218893Sdim case UO_Imag: { 228218893Sdim const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens(); 229218893Sdim Cl::Kinds K = ClassifyInternal(Ctx, Op); 230218893Sdim if (K != Cl::CL_LValue) return K; 231218893Sdim 232218893Sdim if (isa<ObjCPropertyRefExpr>(Op)) 233218893Sdim return Cl::CL_SubObjCPropertySetting; 234218893Sdim return Cl::CL_LValue; 235218893Sdim } 236218893Sdim 237210008Srdivacky // C++ [expr.pre.incr]p1: The result is the updated operand; it is an 238210008Srdivacky // lvalue, [...] 239210008Srdivacky // Not so in C. 240212904Sdim case UO_PreInc: 241212904Sdim case UO_PreDec: 242210008Srdivacky return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue; 243210008Srdivacky 244210008Srdivacky default: 245210008Srdivacky return Cl::CL_PRValue; 246210008Srdivacky } 247210008Srdivacky 248218893Sdim case Expr::OpaqueValueExprClass: 249234353Sdim return ClassifyExprValueKind(Lang, E, E->getValueKind()); 250234353Sdim 251234353Sdim // Pseudo-object expressions can produce l-values with reference magic. 252234353Sdim case Expr::PseudoObjectExprClass: 253218893Sdim return ClassifyExprValueKind(Lang, E, 254234353Sdim cast<PseudoObjectExpr>(E)->getValueKind()); 255218893Sdim 256210008Srdivacky // Implicit casts are lvalues if they're lvalue casts. Other than that, we 257210008Srdivacky // only specifically record class temporaries. 258210008Srdivacky case Expr::ImplicitCastExprClass: 259234353Sdim return ClassifyExprValueKind(Lang, E, E->getValueKind()); 260210008Srdivacky 261210008Srdivacky // C++ [expr.prim.general]p4: The presence of parentheses does not affect 262210008Srdivacky // whether the expression is an lvalue. 263210008Srdivacky case Expr::ParenExprClass: 264210008Srdivacky return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr()); 265210008Srdivacky 266234353Sdim // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator, 267221345Sdim // or a void expression if its result expression is, respectively, an 268221345Sdim // lvalue, a function designator, or a void expression. 269221345Sdim case Expr::GenericSelectionExprClass: 270221345Sdim if (cast<GenericSelectionExpr>(E)->isResultDependent()) 271221345Sdim return Cl::CL_PRValue; 272221345Sdim return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr()); 273221345Sdim 274210008Srdivacky case Expr::BinaryOperatorClass: 275210008Srdivacky case Expr::CompoundAssignOperatorClass: 276210008Srdivacky // C doesn't have any binary expressions that are lvalues. 277210008Srdivacky if (Lang.CPlusPlus) 278210008Srdivacky return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E)); 279210008Srdivacky return Cl::CL_PRValue; 280210008Srdivacky 281210008Srdivacky case Expr::CallExprClass: 282210008Srdivacky case Expr::CXXOperatorCallExprClass: 283210008Srdivacky case Expr::CXXMemberCallExprClass: 284234353Sdim case Expr::UserDefinedLiteralClass: 285218893Sdim case Expr::CUDAKernelCallExprClass: 286210008Srdivacky return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType()); 287210008Srdivacky 288210008Srdivacky // __builtin_choose_expr is equivalent to the chosen expression. 289210008Srdivacky case Expr::ChooseExprClass: 290263508Sdim return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr()); 291210008Srdivacky 292210008Srdivacky // Extended vector element access is an lvalue unless there are duplicates 293210008Srdivacky // in the shuffle expression. 294210008Srdivacky case Expr::ExtVectorElementExprClass: 295263508Sdim if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements()) 296263508Sdim return Cl::CL_DuplicateVectorComponents; 297263508Sdim if (cast<ExtVectorElementExpr>(E)->isArrow()) 298263508Sdim return Cl::CL_LValue; 299263508Sdim return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase()); 300210008Srdivacky 301210008Srdivacky // Simply look at the actual default argument. 302210008Srdivacky case Expr::CXXDefaultArgExprClass: 303210008Srdivacky return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr()); 304210008Srdivacky 305251662Sdim // Same idea for default initializers. 306251662Sdim case Expr::CXXDefaultInitExprClass: 307251662Sdim return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr()); 308251662Sdim 309210008Srdivacky // Same idea for temporary binding. 310210008Srdivacky case Expr::CXXBindTemporaryExprClass: 311210008Srdivacky return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr()); 312210008Srdivacky 313218893Sdim // And the cleanups guard. 314218893Sdim case Expr::ExprWithCleanupsClass: 315218893Sdim return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr()); 316210008Srdivacky 317210008Srdivacky // Casts depend completely on the target type. All casts work the same. 318210008Srdivacky case Expr::CStyleCastExprClass: 319210008Srdivacky case Expr::CXXFunctionalCastExprClass: 320210008Srdivacky case Expr::CXXStaticCastExprClass: 321210008Srdivacky case Expr::CXXDynamicCastExprClass: 322210008Srdivacky case Expr::CXXReinterpretCastExprClass: 323210008Srdivacky case Expr::CXXConstCastExprClass: 324224145Sdim case Expr::ObjCBridgedCastExprClass: 325210008Srdivacky // Only in C++ can casts be interesting at all. 326210008Srdivacky if (!Lang.CPlusPlus) return Cl::CL_PRValue; 327210008Srdivacky return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten()); 328210008Srdivacky 329224145Sdim case Expr::CXXUnresolvedConstructExprClass: 330224145Sdim return ClassifyUnnamed(Ctx, 331224145Sdim cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten()); 332224145Sdim 333218893Sdim case Expr::BinaryConditionalOperatorClass: { 334218893Sdim if (!Lang.CPlusPlus) return Cl::CL_PRValue; 335218893Sdim const BinaryConditionalOperator *co = cast<BinaryConditionalOperator>(E); 336218893Sdim return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 337218893Sdim } 338218893Sdim 339218893Sdim case Expr::ConditionalOperatorClass: { 340210008Srdivacky // Once again, only C++ is interesting. 341210008Srdivacky if (!Lang.CPlusPlus) return Cl::CL_PRValue; 342218893Sdim const ConditionalOperator *co = cast<ConditionalOperator>(E); 343218893Sdim return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr()); 344218893Sdim } 345210008Srdivacky 346210008Srdivacky // ObjC message sends are effectively function calls, if the target function 347210008Srdivacky // is known. 348210008Srdivacky case Expr::ObjCMessageExprClass: 349210008Srdivacky if (const ObjCMethodDecl *Method = 350210008Srdivacky cast<ObjCMessageExpr>(E)->getMethodDecl()) { 351221345Sdim Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getResultType()); 352221345Sdim return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind; 353210008Srdivacky } 354218893Sdim return Cl::CL_PRValue; 355218893Sdim 356210008Srdivacky // Some C++ expressions are always class temporaries. 357210008Srdivacky case Expr::CXXConstructExprClass: 358210008Srdivacky case Expr::CXXTemporaryObjectExprClass: 359234353Sdim case Expr::LambdaExprClass: 360263508Sdim case Expr::CXXStdInitializerListExprClass: 361210008Srdivacky return Cl::CL_ClassTemporary; 362210008Srdivacky 363218893Sdim case Expr::VAArgExprClass: 364218893Sdim return ClassifyUnnamed(Ctx, E->getType()); 365234353Sdim 366218893Sdim case Expr::DesignatedInitExprClass: 367218893Sdim return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit()); 368234353Sdim 369218893Sdim case Expr::StmtExprClass: { 370218893Sdim const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt(); 371218893Sdim if (const Expr *LastExpr = dyn_cast_or_null<Expr>(S->body_back())) 372218893Sdim return ClassifyUnnamed(Ctx, LastExpr->getType()); 373210008Srdivacky return Cl::CL_PRValue; 374210008Srdivacky } 375234353Sdim 376218893Sdim case Expr::CXXUuidofExprClass: 377218893Sdim return Cl::CL_LValue; 378234353Sdim 379218893Sdim case Expr::PackExpansionExprClass: 380218893Sdim return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern()); 381234353Sdim 382224145Sdim case Expr::MaterializeTemporaryExprClass: 383224145Sdim return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference() 384224145Sdim ? Cl::CL_LValue 385224145Sdim : Cl::CL_XValue; 386234353Sdim 387234353Sdim case Expr::InitListExprClass: 388234353Sdim // An init list can be an lvalue if it is bound to a reference and 389234353Sdim // contains only one element. In that case, we look at that element 390234353Sdim // for an exact classification. Init list creation takes care of the 391234353Sdim // value kind for us, so we only need to fine-tune. 392234353Sdim if (E->isRValue()) 393234353Sdim return ClassifyExprValueKind(Lang, E, E->getValueKind()); 394234353Sdim assert(cast<InitListExpr>(E)->getNumInits() == 1 && 395234353Sdim "Only 1-element init lists can be glvalues."); 396234353Sdim return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0)); 397218893Sdim } 398234353Sdim 399218893Sdim llvm_unreachable("unhandled expression kind in classification"); 400210008Srdivacky} 401210008Srdivacky 402210008Srdivacky/// ClassifyDecl - Return the classification of an expression referencing the 403210008Srdivacky/// given declaration. 404210008Srdivackystatic Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) { 405210008Srdivacky // C++ [expr.prim.general]p6: The result is an lvalue if the entity is a 406210008Srdivacky // function, variable, or data member and a prvalue otherwise. 407210008Srdivacky // In C, functions are not lvalues. 408210008Srdivacky // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an 409210008Srdivacky // lvalue unless it's a reference type (C++ [temp.param]p6), so we need to 410210008Srdivacky // special-case this. 411212904Sdim 412212904Sdim if (isa<CXXMethodDecl>(D) && cast<CXXMethodDecl>(D)->isInstance()) 413212904Sdim return Cl::CL_MemberFunction; 414212904Sdim 415210008Srdivacky bool islvalue; 416210008Srdivacky if (const NonTypeTemplateParmDecl *NTTParm = 417210008Srdivacky dyn_cast<NonTypeTemplateParmDecl>(D)) 418210008Srdivacky islvalue = NTTParm->getType()->isReferenceType(); 419210008Srdivacky else 420210008Srdivacky islvalue = isa<VarDecl>(D) || isa<FieldDecl>(D) || 421218893Sdim isa<IndirectFieldDecl>(D) || 422234353Sdim (Ctx.getLangOpts().CPlusPlus && 423210008Srdivacky (isa<FunctionDecl>(D) || isa<FunctionTemplateDecl>(D))); 424210008Srdivacky 425210008Srdivacky return islvalue ? Cl::CL_LValue : Cl::CL_PRValue; 426210008Srdivacky} 427210008Srdivacky 428210008Srdivacky/// ClassifyUnnamed - Return the classification of an expression yielding an 429210008Srdivacky/// unnamed value of the given type. This applies in particular to function 430210008Srdivacky/// calls and casts. 431210008Srdivackystatic Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) { 432210008Srdivacky // In C, function calls are always rvalues. 433234353Sdim if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue; 434210008Srdivacky 435210008Srdivacky // C++ [expr.call]p10: A function call is an lvalue if the result type is an 436210008Srdivacky // lvalue reference type or an rvalue reference to function type, an xvalue 437226633Sdim // if the result type is an rvalue reference to object type, and a prvalue 438210008Srdivacky // otherwise. 439210008Srdivacky if (T->isLValueReferenceType()) 440210008Srdivacky return Cl::CL_LValue; 441210008Srdivacky const RValueReferenceType *RV = T->getAs<RValueReferenceType>(); 442210008Srdivacky if (!RV) // Could still be a class temporary, though. 443239462Sdim return ClassifyTemporary(T); 444210008Srdivacky 445210008Srdivacky return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue; 446210008Srdivacky} 447210008Srdivacky 448210008Srdivackystatic Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) { 449221345Sdim if (E->getType() == Ctx.UnknownAnyTy) 450221345Sdim return (isa<FunctionDecl>(E->getMemberDecl()) 451221345Sdim ? Cl::CL_PRValue : Cl::CL_LValue); 452221345Sdim 453210008Srdivacky // Handle C first, it's easier. 454234353Sdim if (!Ctx.getLangOpts().CPlusPlus) { 455210008Srdivacky // C99 6.5.2.3p3 456210008Srdivacky // For dot access, the expression is an lvalue if the first part is. For 457210008Srdivacky // arrow access, it always is an lvalue. 458210008Srdivacky if (E->isArrow()) 459210008Srdivacky return Cl::CL_LValue; 460210008Srdivacky // ObjC property accesses are not lvalues, but get special treatment. 461218893Sdim Expr *Base = E->getBase()->IgnoreParens(); 462218893Sdim if (isa<ObjCPropertyRefExpr>(Base)) 463210008Srdivacky return Cl::CL_SubObjCPropertySetting; 464210008Srdivacky return ClassifyInternal(Ctx, Base); 465210008Srdivacky } 466210008Srdivacky 467210008Srdivacky NamedDecl *Member = E->getMemberDecl(); 468210008Srdivacky // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2. 469210008Srdivacky // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then 470210008Srdivacky // E1.E2 is an lvalue. 471210008Srdivacky if (ValueDecl *Value = dyn_cast<ValueDecl>(Member)) 472210008Srdivacky if (Value->getType()->isReferenceType()) 473210008Srdivacky return Cl::CL_LValue; 474210008Srdivacky 475210008Srdivacky // Otherwise, one of the following rules applies. 476210008Srdivacky // -- If E2 is a static member [...] then E1.E2 is an lvalue. 477210008Srdivacky if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord()) 478210008Srdivacky return Cl::CL_LValue; 479210008Srdivacky 480210008Srdivacky // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then 481210008Srdivacky // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue; 482210008Srdivacky // otherwise, it is a prvalue. 483210008Srdivacky if (isa<FieldDecl>(Member)) { 484210008Srdivacky // *E1 is an lvalue 485210008Srdivacky if (E->isArrow()) 486210008Srdivacky return Cl::CL_LValue; 487218893Sdim Expr *Base = E->getBase()->IgnoreParenImpCasts(); 488218893Sdim if (isa<ObjCPropertyRefExpr>(Base)) 489218893Sdim return Cl::CL_SubObjCPropertySetting; 490210008Srdivacky return ClassifyInternal(Ctx, E->getBase()); 491210008Srdivacky } 492210008Srdivacky 493210008Srdivacky // -- If E2 is a [...] member function, [...] 494210008Srdivacky // -- If it refers to a static member function [...], then E1.E2 is an 495210008Srdivacky // lvalue; [...] 496210008Srdivacky // -- Otherwise [...] E1.E2 is a prvalue. 497210008Srdivacky if (CXXMethodDecl *Method = dyn_cast<CXXMethodDecl>(Member)) 498210008Srdivacky return Method->isStatic() ? Cl::CL_LValue : Cl::CL_MemberFunction; 499210008Srdivacky 500210008Srdivacky // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue. 501210008Srdivacky // So is everything else we haven't handled yet. 502210008Srdivacky return Cl::CL_PRValue; 503210008Srdivacky} 504210008Srdivacky 505210008Srdivackystatic Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) { 506234353Sdim assert(Ctx.getLangOpts().CPlusPlus && 507210008Srdivacky "This is only relevant for C++."); 508210008Srdivacky // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand. 509218893Sdim // Except we override this for writes to ObjC properties. 510210008Srdivacky if (E->isAssignmentOp()) 511218893Sdim return (E->getLHS()->getObjectKind() == OK_ObjCProperty 512218893Sdim ? Cl::CL_PRValue : Cl::CL_LValue); 513210008Srdivacky 514210008Srdivacky // C++ [expr.comma]p1: the result is of the same value category as its right 515210008Srdivacky // operand, [...]. 516212904Sdim if (E->getOpcode() == BO_Comma) 517210008Srdivacky return ClassifyInternal(Ctx, E->getRHS()); 518210008Srdivacky 519210008Srdivacky // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand 520210008Srdivacky // is a pointer to a data member is of the same value category as its first 521210008Srdivacky // operand. 522212904Sdim if (E->getOpcode() == BO_PtrMemD) 523234353Sdim return (E->getType()->isFunctionType() || 524234353Sdim E->hasPlaceholderType(BuiltinType::BoundMember)) 525223017Sdim ? Cl::CL_MemberFunction 526223017Sdim : ClassifyInternal(Ctx, E->getLHS()); 527210008Srdivacky 528210008Srdivacky // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its 529210008Srdivacky // second operand is a pointer to data member and a prvalue otherwise. 530212904Sdim if (E->getOpcode() == BO_PtrMemI) 531234353Sdim return (E->getType()->isFunctionType() || 532234353Sdim E->hasPlaceholderType(BuiltinType::BoundMember)) 533223017Sdim ? Cl::CL_MemberFunction 534223017Sdim : Cl::CL_LValue; 535210008Srdivacky 536210008Srdivacky // All other binary operations are prvalues. 537210008Srdivacky return Cl::CL_PRValue; 538210008Srdivacky} 539210008Srdivacky 540218893Sdimstatic Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True, 541218893Sdim const Expr *False) { 542234353Sdim assert(Ctx.getLangOpts().CPlusPlus && 543210008Srdivacky "This is only relevant for C++."); 544210008Srdivacky 545210008Srdivacky // C++ [expr.cond]p2 546210008Srdivacky // If either the second or the third operand has type (cv) void, [...] 547210008Srdivacky // the result [...] is a prvalue. 548210008Srdivacky if (True->getType()->isVoidType() || False->getType()->isVoidType()) 549210008Srdivacky return Cl::CL_PRValue; 550210008Srdivacky 551210008Srdivacky // Note that at this point, we have already performed all conversions 552210008Srdivacky // according to [expr.cond]p3. 553210008Srdivacky // C++ [expr.cond]p4: If the second and third operands are glvalues of the 554210008Srdivacky // same value category [...], the result is of that [...] value category. 555210008Srdivacky // C++ [expr.cond]p5: Otherwise, the result is a prvalue. 556210008Srdivacky Cl::Kinds LCl = ClassifyInternal(Ctx, True), 557210008Srdivacky RCl = ClassifyInternal(Ctx, False); 558210008Srdivacky return LCl == RCl ? LCl : Cl::CL_PRValue; 559210008Srdivacky} 560210008Srdivacky 561210008Srdivackystatic Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E, 562210008Srdivacky Cl::Kinds Kind, SourceLocation &Loc) { 563210008Srdivacky // As a general rule, we only care about lvalues. But there are some rvalues 564210008Srdivacky // for which we want to generate special results. 565210008Srdivacky if (Kind == Cl::CL_PRValue) { 566210008Srdivacky // For the sake of better diagnostics, we want to specifically recognize 567210008Srdivacky // use of the GCC cast-as-lvalue extension. 568218893Sdim if (const ExplicitCastExpr *CE = 569218893Sdim dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) { 570218893Sdim if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) { 571218893Sdim Loc = CE->getExprLoc(); 572210008Srdivacky return Cl::CM_LValueCast; 573210008Srdivacky } 574210008Srdivacky } 575210008Srdivacky } 576210008Srdivacky if (Kind != Cl::CL_LValue) 577210008Srdivacky return Cl::CM_RValue; 578210008Srdivacky 579210008Srdivacky // This is the lvalue case. 580210008Srdivacky // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6) 581234353Sdim if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType()) 582210008Srdivacky return Cl::CM_Function; 583210008Srdivacky 584210008Srdivacky // Assignment to a property in ObjC is an implicit setter access. But a 585210008Srdivacky // setter might not exist. 586218893Sdim if (const ObjCPropertyRefExpr *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) { 587218893Sdim if (Expr->isImplicitProperty() && Expr->getImplicitPropertySetter() == 0) 588210008Srdivacky return Cl::CM_NoSetterProperty; 589210008Srdivacky } 590210008Srdivacky 591210008Srdivacky CanQualType CT = Ctx.getCanonicalType(E->getType()); 592210008Srdivacky // Const stuff is obviously not modifiable. 593210008Srdivacky if (CT.isConstQualified()) 594210008Srdivacky return Cl::CM_ConstQualified; 595263508Sdim if (CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant) 596263508Sdim return Cl::CM_ConstQualified; 597234353Sdim 598210008Srdivacky // Arrays are not modifiable, only their elements are. 599210008Srdivacky if (CT->isArrayType()) 600210008Srdivacky return Cl::CM_ArrayType; 601210008Srdivacky // Incomplete types are not modifiable. 602210008Srdivacky if (CT->isIncompleteType()) 603210008Srdivacky return Cl::CM_IncompleteType; 604210008Srdivacky 605210008Srdivacky // Records with any const fields (recursively) are not modifiable. 606210008Srdivacky if (const RecordType *R = CT->getAs<RecordType>()) { 607218893Sdim assert((E->getObjectKind() == OK_ObjCProperty || 608234353Sdim !Ctx.getLangOpts().CPlusPlus) && 609210008Srdivacky "C++ struct assignment should be resolved by the " 610210008Srdivacky "copy assignment operator."); 611210008Srdivacky if (R->hasConstFields()) 612210008Srdivacky return Cl::CM_ConstQualified; 613210008Srdivacky } 614210008Srdivacky 615210008Srdivacky return Cl::CM_Modifiable; 616210008Srdivacky} 617210008Srdivacky 618218893SdimExpr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const { 619210008Srdivacky Classification VC = Classify(Ctx); 620210008Srdivacky switch (VC.getKind()) { 621210008Srdivacky case Cl::CL_LValue: return LV_Valid; 622210008Srdivacky case Cl::CL_XValue: return LV_InvalidExpression; 623210008Srdivacky case Cl::CL_Function: return LV_NotObjectType; 624221345Sdim case Cl::CL_Void: return LV_InvalidExpression; 625221345Sdim case Cl::CL_AddressableVoid: return LV_IncompleteVoidType; 626210008Srdivacky case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents; 627210008Srdivacky case Cl::CL_MemberFunction: return LV_MemberFunction; 628210008Srdivacky case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting; 629210008Srdivacky case Cl::CL_ClassTemporary: return LV_ClassTemporary; 630239462Sdim case Cl::CL_ArrayTemporary: return LV_ArrayTemporary; 631221345Sdim case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression; 632210008Srdivacky case Cl::CL_PRValue: return LV_InvalidExpression; 633210008Srdivacky } 634210008Srdivacky llvm_unreachable("Unhandled kind"); 635210008Srdivacky} 636210008Srdivacky 637210008SrdivackyExpr::isModifiableLvalueResult 638210008SrdivackyExpr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const { 639210008Srdivacky SourceLocation dummy; 640210008Srdivacky Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy); 641210008Srdivacky switch (VC.getKind()) { 642210008Srdivacky case Cl::CL_LValue: break; 643210008Srdivacky case Cl::CL_XValue: return MLV_InvalidExpression; 644210008Srdivacky case Cl::CL_Function: return MLV_NotObjectType; 645221345Sdim case Cl::CL_Void: return MLV_InvalidExpression; 646221345Sdim case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType; 647210008Srdivacky case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents; 648210008Srdivacky case Cl::CL_MemberFunction: return MLV_MemberFunction; 649210008Srdivacky case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting; 650210008Srdivacky case Cl::CL_ClassTemporary: return MLV_ClassTemporary; 651239462Sdim case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary; 652221345Sdim case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression; 653210008Srdivacky case Cl::CL_PRValue: 654210008Srdivacky return VC.getModifiable() == Cl::CM_LValueCast ? 655210008Srdivacky MLV_LValueCast : MLV_InvalidExpression; 656210008Srdivacky } 657210008Srdivacky assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind"); 658210008Srdivacky switch (VC.getModifiable()) { 659210008Srdivacky case Cl::CM_Untested: llvm_unreachable("Did not test modifiability"); 660210008Srdivacky case Cl::CM_Modifiable: return MLV_Valid; 661210008Srdivacky case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match"); 662210008Srdivacky case Cl::CM_Function: return MLV_NotObjectType; 663210008Srdivacky case Cl::CM_LValueCast: 664210008Srdivacky llvm_unreachable("CM_LValueCast and CL_LValue don't match"); 665210008Srdivacky case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty; 666210008Srdivacky case Cl::CM_ConstQualified: return MLV_ConstQualified; 667210008Srdivacky case Cl::CM_ArrayType: return MLV_ArrayType; 668210008Srdivacky case Cl::CM_IncompleteType: return MLV_IncompleteType; 669210008Srdivacky } 670210008Srdivacky llvm_unreachable("Unhandled modifiable type"); 671210008Srdivacky} 672