785 lines · cpp
1//===- ExprClassification.cpp - Expression AST Node Implementation --------===//2//3// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.4// See https://llvm.org/LICENSE.txt for license information.5// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception6//7//===----------------------------------------------------------------------===//8//9// This file implements Expr::classify.10//11//===----------------------------------------------------------------------===//12 13#include "clang/AST/Expr.h"14#include "clang/AST/ASTContext.h"15#include "clang/AST/DeclCXX.h"16#include "clang/AST/DeclObjC.h"17#include "clang/AST/DeclTemplate.h"18#include "clang/AST/ExprCXX.h"19#include "clang/AST/ExprObjC.h"20#include "llvm/Support/ErrorHandling.h"21 22using namespace clang;23 24using Cl = Expr::Classification;25 26static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E);27static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D);28static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T);29static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E);30static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E);31static Cl::Kinds ClassifyConditional(ASTContext &Ctx,32 const Expr *trueExpr,33 const Expr *falseExpr);34static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,35 Cl::Kinds Kind, SourceLocation &Loc);36 37Cl Expr::ClassifyImpl(ASTContext &Ctx, SourceLocation *Loc) const {38 assert(!TR->isReferenceType() && "Expressions can't have reference type.");39 40 Cl::Kinds kind = ClassifyInternal(Ctx, this);41 // C99 6.3.2.1: An lvalue is an expression with an object type or an42 // incomplete type other than void.43 if (!Ctx.getLangOpts().CPlusPlus) {44 // Thus, no functions.45 if (TR->isFunctionType() || TR == Ctx.OverloadTy)46 kind = Cl::CL_Function;47 // No void either, but qualified void is OK because it is "other than void".48 // Void "lvalues" are classified as addressable void values, which are void49 // expressions whose address can be taken.50 else if (TR->isVoidType() && !TR.hasQualifiers())51 kind = (kind == Cl::CL_LValue ? Cl::CL_AddressableVoid : Cl::CL_Void);52 }53 54 // Enable this assertion for testing.55 switch (kind) {56 case Cl::CL_LValue:57 assert(isLValue());58 break;59 case Cl::CL_XValue:60 assert(isXValue());61 break;62 case Cl::CL_Function:63 case Cl::CL_Void:64 case Cl::CL_AddressableVoid:65 case Cl::CL_DuplicateVectorComponents:66 case Cl::CL_MemberFunction:67 case Cl::CL_SubObjCPropertySetting:68 case Cl::CL_ClassTemporary:69 case Cl::CL_ArrayTemporary:70 case Cl::CL_ObjCMessageRValue:71 case Cl::CL_PRValue:72 assert(isPRValue());73 break;74 }75 76 Cl::ModifiableType modifiable = Cl::CM_Untested;77 if (Loc)78 modifiable = IsModifiable(Ctx, this, kind, *Loc);79 return Classification(kind, modifiable);80}81 82/// Classify an expression which creates a temporary, based on its type.83static Cl::Kinds ClassifyTemporary(QualType T) {84 if (T->isRecordType())85 return Cl::CL_ClassTemporary;86 if (T->isArrayType())87 return Cl::CL_ArrayTemporary;88 89 // No special classification: these don't behave differently from normal90 // prvalues.91 return Cl::CL_PRValue;92}93 94static Cl::Kinds ClassifyExprValueKind(const LangOptions &Lang,95 const Expr *E,96 ExprValueKind Kind) {97 switch (Kind) {98 case VK_PRValue:99 return Lang.CPlusPlus ? ClassifyTemporary(E->getType()) : Cl::CL_PRValue;100 case VK_LValue:101 return Cl::CL_LValue;102 case VK_XValue:103 return Cl::CL_XValue;104 }105 llvm_unreachable("Invalid value category of implicit cast.");106}107 108static Cl::Kinds ClassifyInternal(ASTContext &Ctx, const Expr *E) {109 // This function takes the first stab at classifying expressions.110 const LangOptions &Lang = Ctx.getLangOpts();111 112 switch (E->getStmtClass()) {113 case Stmt::NoStmtClass:114#define ABSTRACT_STMT(Kind)115#define STMT(Kind, Base) case Expr::Kind##Class:116#define EXPR(Kind, Base)117#include "clang/AST/StmtNodes.inc"118 llvm_unreachable("cannot classify a statement");119 120 // First come the expressions that are always lvalues, unconditionally.121 case Expr::ObjCIsaExprClass:122 // Property references are lvalues123 case Expr::ObjCSubscriptRefExprClass:124 case Expr::ObjCPropertyRefExprClass:125 // C++ [expr.typeid]p1: The result of a typeid expression is an lvalue of...126 case Expr::CXXTypeidExprClass:127 case Expr::CXXUuidofExprClass:128 // Unresolved lookups and uncorrected typos get classified as lvalues.129 // FIXME: Is this wise? Should they get their own kind?130 case Expr::UnresolvedLookupExprClass:131 case Expr::UnresolvedMemberExprClass:132 case Expr::DependentCoawaitExprClass:133 case Expr::CXXDependentScopeMemberExprClass:134 case Expr::DependentScopeDeclRefExprClass:135 // ObjC instance variables are lvalues136 // FIXME: ObjC++0x might have different rules137 case Expr::ObjCIvarRefExprClass:138 case Expr::FunctionParmPackExprClass:139 case Expr::MSPropertyRefExprClass:140 case Expr::MSPropertySubscriptExprClass:141 case Expr::ArraySectionExprClass:142 case Expr::OMPArrayShapingExprClass:143 case Expr::OMPIteratorExprClass:144 case Expr::HLSLOutArgExprClass:145 return Cl::CL_LValue;146 147 // C++ [expr.prim.general]p1: A string literal is an lvalue.148 case Expr::StringLiteralClass:149 // @encode is equivalent to its string150 case Expr::ObjCEncodeExprClass:151 // Except we special case them as prvalues when they are used to152 // initialize a char array.153 return E->isLValue() ? Cl::CL_LValue : Cl::CL_PRValue;154 155 // __func__ and friends are too.156 // The char array initialization special case also applies157 // when they are transparent.158 case Expr::PredefinedExprClass: {159 auto *PE = cast<PredefinedExpr>(E);160 const StringLiteral *SL = PE->getFunctionName();161 if (PE->isTransparent())162 return SL ? ClassifyInternal(Ctx, SL) : Cl::CL_LValue;163 assert(!SL || SL->isLValue());164 return Cl::CL_LValue;165 }166 167 // C99 6.5.2.5p5 says that compound literals are lvalues.168 // In C++, they're prvalue temporaries, except for file-scope arrays.169 case Expr::CompoundLiteralExprClass:170 return !E->isLValue() ? ClassifyTemporary(E->getType()) : Cl::CL_LValue;171 172 // Expressions that are prvalues.173 case Expr::CXXBoolLiteralExprClass:174 case Expr::CXXPseudoDestructorExprClass:175 case Expr::UnaryExprOrTypeTraitExprClass:176 case Expr::CXXNewExprClass:177 case Expr::CXXNullPtrLiteralExprClass:178 case Expr::ImaginaryLiteralClass:179 case Expr::GNUNullExprClass:180 case Expr::OffsetOfExprClass:181 case Expr::CXXThrowExprClass:182 case Expr::ShuffleVectorExprClass:183 case Expr::ConvertVectorExprClass:184 case Expr::IntegerLiteralClass:185 case Expr::FixedPointLiteralClass:186 case Expr::CharacterLiteralClass:187 case Expr::AddrLabelExprClass:188 case Expr::CXXDeleteExprClass:189 case Expr::ImplicitValueInitExprClass:190 case Expr::BlockExprClass:191 case Expr::FloatingLiteralClass:192 case Expr::CXXNoexceptExprClass:193 case Expr::CXXScalarValueInitExprClass:194 case Expr::TypeTraitExprClass:195 case Expr::ArrayTypeTraitExprClass:196 case Expr::ExpressionTraitExprClass:197 case Expr::ObjCSelectorExprClass:198 case Expr::ObjCProtocolExprClass:199 case Expr::ObjCStringLiteralClass:200 case Expr::ObjCBoxedExprClass:201 case Expr::ObjCArrayLiteralClass:202 case Expr::ObjCDictionaryLiteralClass:203 case Expr::ObjCBoolLiteralExprClass:204 case Expr::ObjCAvailabilityCheckExprClass:205 case Expr::ParenListExprClass:206 case Expr::SizeOfPackExprClass:207 case Expr::SubstNonTypeTemplateParmPackExprClass:208 case Expr::AsTypeExprClass:209 case Expr::ObjCIndirectCopyRestoreExprClass:210 case Expr::AtomicExprClass:211 case Expr::CXXFoldExprClass:212 case Expr::ArrayInitLoopExprClass:213 case Expr::ArrayInitIndexExprClass:214 case Expr::NoInitExprClass:215 case Expr::DesignatedInitUpdateExprClass:216 case Expr::SourceLocExprClass:217 case Expr::ConceptSpecializationExprClass:218 case Expr::RequiresExprClass:219 return Cl::CL_PRValue;220 221 case Expr::EmbedExprClass:222 // Nominally, this just goes through as a PRValue until we actually expand223 // it and check it.224 return Cl::CL_PRValue;225 226 // Make HLSL this reference-like227 case Expr::CXXThisExprClass:228 return Lang.HLSL ? Cl::CL_LValue : Cl::CL_PRValue;229 230 case Expr::ConstantExprClass:231 return ClassifyInternal(Ctx, cast<ConstantExpr>(E)->getSubExpr());232 233 // Next come the complicated cases.234 case Expr::SubstNonTypeTemplateParmExprClass:235 return ClassifyInternal(Ctx,236 cast<SubstNonTypeTemplateParmExpr>(E)->getReplacement());237 238 case Expr::PackIndexingExprClass: {239 // A pack-index-expression always expands to an id-expression.240 // Consider it as an LValue expression.241 if (cast<PackIndexingExpr>(E)->isInstantiationDependent())242 return Cl::CL_LValue;243 return ClassifyInternal(Ctx, cast<PackIndexingExpr>(E)->getSelectedExpr());244 }245 246 // C, C++98 [expr.sub]p1: The result is an lvalue of type "T".247 // C++11 (DR1213): in the case of an array operand, the result is an lvalue248 // if that operand is an lvalue and an xvalue otherwise.249 // Subscripting vector types is more like member access.250 case Expr::ArraySubscriptExprClass:251 if (cast<ArraySubscriptExpr>(E)->getBase()->getType()->isVectorType())252 return ClassifyInternal(Ctx, cast<ArraySubscriptExpr>(E)->getBase());253 if (Lang.CPlusPlus11) {254 // Step over the array-to-pointer decay if present, but not over the255 // temporary materialization.256 auto *Base = cast<ArraySubscriptExpr>(E)->getBase()->IgnoreImpCasts();257 if (Base->getType()->isArrayType())258 return ClassifyInternal(Ctx, Base);259 }260 return Cl::CL_LValue;261 262 // Subscripting matrix types behaves like member accesses.263 case Expr::MatrixSubscriptExprClass:264 return ClassifyInternal(Ctx, cast<MatrixSubscriptExpr>(E)->getBase());265 266 // C++ [expr.prim.general]p3: The result is an lvalue if the entity is a267 // function or variable and a prvalue otherwise.268 case Expr::DeclRefExprClass:269 if (E->getType() == Ctx.UnknownAnyTy)270 return isa<FunctionDecl>(cast<DeclRefExpr>(E)->getDecl())271 ? Cl::CL_PRValue : Cl::CL_LValue;272 return ClassifyDecl(Ctx, cast<DeclRefExpr>(E)->getDecl());273 274 // Member access is complex.275 case Expr::MemberExprClass:276 return ClassifyMemberExpr(Ctx, cast<MemberExpr>(E));277 278 case Expr::UnaryOperatorClass:279 switch (cast<UnaryOperator>(E)->getOpcode()) {280 // C++ [expr.unary.op]p1: The unary * operator performs indirection:281 // [...] the result is an lvalue referring to the object or function282 // to which the expression points.283 case UO_Deref:284 return Cl::CL_LValue;285 286 // GNU extensions, simply look through them.287 case UO_Extension:288 return ClassifyInternal(Ctx, cast<UnaryOperator>(E)->getSubExpr());289 290 // Treat _Real and _Imag basically as if they were member291 // expressions: l-value only if the operand is a true l-value.292 case UO_Real:293 case UO_Imag: {294 const Expr *Op = cast<UnaryOperator>(E)->getSubExpr()->IgnoreParens();295 Cl::Kinds K = ClassifyInternal(Ctx, Op);296 if (K != Cl::CL_LValue) return K;297 298 if (isa<ObjCPropertyRefExpr>(Op))299 return Cl::CL_SubObjCPropertySetting;300 return Cl::CL_LValue;301 }302 303 // C++ [expr.pre.incr]p1: The result is the updated operand; it is an304 // lvalue, [...]305 // Not so in C.306 case UO_PreInc:307 case UO_PreDec:308 return Lang.CPlusPlus ? Cl::CL_LValue : Cl::CL_PRValue;309 310 default:311 return Cl::CL_PRValue;312 }313 314 case Expr::RecoveryExprClass:315 case Expr::OpaqueValueExprClass:316 return ClassifyExprValueKind(Lang, E, E->getValueKind());317 318 // Pseudo-object expressions can produce l-values with reference magic.319 case Expr::PseudoObjectExprClass:320 return ClassifyExprValueKind(Lang, E,321 cast<PseudoObjectExpr>(E)->getValueKind());322 323 // Implicit casts are lvalues if they're lvalue casts. Other than that, we324 // only specifically record class temporaries.325 case Expr::ImplicitCastExprClass:326 return ClassifyExprValueKind(Lang, E, E->getValueKind());327 328 // C++ [expr.prim.general]p4: The presence of parentheses does not affect329 // whether the expression is an lvalue.330 case Expr::ParenExprClass:331 return ClassifyInternal(Ctx, cast<ParenExpr>(E)->getSubExpr());332 333 // C11 6.5.1.1p4: [A generic selection] is an lvalue, a function designator,334 // or a void expression if its result expression is, respectively, an335 // lvalue, a function designator, or a void expression.336 case Expr::GenericSelectionExprClass:337 if (cast<GenericSelectionExpr>(E)->isResultDependent())338 return Cl::CL_PRValue;339 return ClassifyInternal(Ctx,cast<GenericSelectionExpr>(E)->getResultExpr());340 341 case Expr::BinaryOperatorClass:342 case Expr::CompoundAssignOperatorClass:343 // C doesn't have any binary expressions that are lvalues.344 if (Lang.CPlusPlus)345 return ClassifyBinaryOp(Ctx, cast<BinaryOperator>(E));346 return Cl::CL_PRValue;347 348 case Expr::CallExprClass:349 case Expr::CXXOperatorCallExprClass:350 case Expr::CXXMemberCallExprClass:351 case Expr::UserDefinedLiteralClass:352 case Expr::CUDAKernelCallExprClass:353 return ClassifyUnnamed(Ctx, cast<CallExpr>(E)->getCallReturnType(Ctx));354 355 case Expr::CXXRewrittenBinaryOperatorClass:356 return ClassifyInternal(357 Ctx, cast<CXXRewrittenBinaryOperator>(E)->getSemanticForm());358 359 // __builtin_choose_expr is equivalent to the chosen expression.360 case Expr::ChooseExprClass:361 return ClassifyInternal(Ctx, cast<ChooseExpr>(E)->getChosenSubExpr());362 363 // Extended vector element access is an lvalue unless there are duplicates364 // in the shuffle expression.365 case Expr::ExtVectorElementExprClass:366 if (cast<ExtVectorElementExpr>(E)->containsDuplicateElements())367 return Cl::CL_DuplicateVectorComponents;368 if (cast<ExtVectorElementExpr>(E)->isArrow())369 return Cl::CL_LValue;370 return ClassifyInternal(Ctx, cast<ExtVectorElementExpr>(E)->getBase());371 372 // Simply look at the actual default argument.373 case Expr::CXXDefaultArgExprClass:374 return ClassifyInternal(Ctx, cast<CXXDefaultArgExpr>(E)->getExpr());375 376 // Same idea for default initializers.377 case Expr::CXXDefaultInitExprClass:378 return ClassifyInternal(Ctx, cast<CXXDefaultInitExpr>(E)->getExpr());379 380 // Same idea for temporary binding.381 case Expr::CXXBindTemporaryExprClass:382 return ClassifyInternal(Ctx, cast<CXXBindTemporaryExpr>(E)->getSubExpr());383 384 // And the cleanups guard.385 case Expr::ExprWithCleanupsClass:386 return ClassifyInternal(Ctx, cast<ExprWithCleanups>(E)->getSubExpr());387 388 // Casts depend completely on the target type. All casts work the same.389 case Expr::CStyleCastExprClass:390 case Expr::CXXFunctionalCastExprClass:391 case Expr::CXXStaticCastExprClass:392 case Expr::CXXDynamicCastExprClass:393 case Expr::CXXReinterpretCastExprClass:394 case Expr::CXXConstCastExprClass:395 case Expr::CXXAddrspaceCastExprClass:396 case Expr::ObjCBridgedCastExprClass:397 case Expr::BuiltinBitCastExprClass:398 // Only in C++ can casts be interesting at all.399 if (!Lang.CPlusPlus) return Cl::CL_PRValue;400 return ClassifyUnnamed(Ctx, cast<ExplicitCastExpr>(E)->getTypeAsWritten());401 402 case Expr::CXXUnresolvedConstructExprClass:403 return ClassifyUnnamed(Ctx,404 cast<CXXUnresolvedConstructExpr>(E)->getTypeAsWritten());405 406 case Expr::BinaryConditionalOperatorClass: {407 if (!Lang.CPlusPlus) return Cl::CL_PRValue;408 const auto *co = cast<BinaryConditionalOperator>(E);409 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());410 }411 412 case Expr::ConditionalOperatorClass: {413 // Once again, only C++ is interesting.414 if (!Lang.CPlusPlus) return Cl::CL_PRValue;415 const auto *co = cast<ConditionalOperator>(E);416 return ClassifyConditional(Ctx, co->getTrueExpr(), co->getFalseExpr());417 }418 419 // ObjC message sends are effectively function calls, if the target function420 // is known.421 case Expr::ObjCMessageExprClass:422 if (const ObjCMethodDecl *Method =423 cast<ObjCMessageExpr>(E)->getMethodDecl()) {424 Cl::Kinds kind = ClassifyUnnamed(Ctx, Method->getReturnType());425 return (kind == Cl::CL_PRValue) ? Cl::CL_ObjCMessageRValue : kind;426 }427 return Cl::CL_PRValue;428 429 // Some C++ expressions are always class temporaries.430 case Expr::CXXConstructExprClass:431 case Expr::CXXInheritedCtorInitExprClass:432 case Expr::CXXTemporaryObjectExprClass:433 case Expr::LambdaExprClass:434 case Expr::CXXStdInitializerListExprClass:435 return Cl::CL_ClassTemporary;436 437 case Expr::VAArgExprClass:438 return ClassifyUnnamed(Ctx, E->getType());439 440 case Expr::DesignatedInitExprClass:441 return ClassifyInternal(Ctx, cast<DesignatedInitExpr>(E)->getInit());442 443 case Expr::StmtExprClass: {444 const CompoundStmt *S = cast<StmtExpr>(E)->getSubStmt();445 if (const auto *LastExpr = dyn_cast_or_null<Expr>(S->body_back()))446 return ClassifyUnnamed(Ctx, LastExpr->getType());447 return Cl::CL_PRValue;448 }449 450 case Expr::PackExpansionExprClass:451 return ClassifyInternal(Ctx, cast<PackExpansionExpr>(E)->getPattern());452 453 case Expr::MaterializeTemporaryExprClass:454 return cast<MaterializeTemporaryExpr>(E)->isBoundToLvalueReference()455 ? Cl::CL_LValue456 : Cl::CL_XValue;457 458 case Expr::InitListExprClass:459 // An init list can be an lvalue if it is bound to a reference and460 // contains only one element. In that case, we look at that element461 // for an exact classification. Init list creation takes care of the462 // value kind for us, so we only need to fine-tune.463 if (E->isPRValue())464 return ClassifyExprValueKind(Lang, E, E->getValueKind());465 assert(cast<InitListExpr>(E)->getNumInits() == 1 &&466 "Only 1-element init lists can be glvalues.");467 return ClassifyInternal(Ctx, cast<InitListExpr>(E)->getInit(0));468 469 case Expr::CoawaitExprClass:470 case Expr::CoyieldExprClass:471 return ClassifyInternal(Ctx, cast<CoroutineSuspendExpr>(E)->getResumeExpr());472 case Expr::SYCLUniqueStableNameExprClass:473 case Expr::OpenACCAsteriskSizeExprClass:474 return Cl::CL_PRValue;475 break;476 477 case Expr::CXXParenListInitExprClass:478 if (isa<ArrayType>(E->getType()))479 return Cl::CL_ArrayTemporary;480 return Cl::CL_ClassTemporary;481 }482 483 llvm_unreachable("unhandled expression kind in classification");484}485 486/// ClassifyDecl - Return the classification of an expression referencing the487/// given declaration.488static Cl::Kinds ClassifyDecl(ASTContext &Ctx, const Decl *D) {489 // C++ [expr.prim.id.unqual]p3: The result is an lvalue if the entity is a490 // function, variable, or data member, or a template parameter object and a491 // prvalue otherwise.492 // In C, functions are not lvalues.493 // In addition, NonTypeTemplateParmDecl derives from VarDecl but isn't an494 // lvalue unless it's a reference type or a class type (C++ [temp.param]p8),495 // so we need to special-case this.496 497 if (const auto *M = dyn_cast<CXXMethodDecl>(D)) {498 if (M->isImplicitObjectMemberFunction())499 return Cl::CL_MemberFunction;500 if (M->isStatic())501 return Cl::CL_LValue;502 return Cl::CL_PRValue;503 }504 505 bool islvalue;506 if (const auto *NTTParm = dyn_cast<NonTypeTemplateParmDecl>(D))507 islvalue = NTTParm->getType()->isReferenceType() ||508 NTTParm->getType()->isRecordType();509 else510 islvalue =511 isa<VarDecl, FieldDecl, IndirectFieldDecl, BindingDecl, MSGuidDecl,512 UnnamedGlobalConstantDecl, TemplateParamObjectDecl>(D) ||513 (Ctx.getLangOpts().CPlusPlus &&514 (isa<FunctionDecl, MSPropertyDecl, FunctionTemplateDecl>(D)));515 516 return islvalue ? Cl::CL_LValue : Cl::CL_PRValue;517}518 519/// ClassifyUnnamed - Return the classification of an expression yielding an520/// unnamed value of the given type. This applies in particular to function521/// calls and casts.522static Cl::Kinds ClassifyUnnamed(ASTContext &Ctx, QualType T) {523 // In C, function calls are always rvalues.524 if (!Ctx.getLangOpts().CPlusPlus) return Cl::CL_PRValue;525 526 // C++ [expr.call]p10: A function call is an lvalue if the result type is an527 // lvalue reference type or an rvalue reference to function type, an xvalue528 // if the result type is an rvalue reference to object type, and a prvalue529 // otherwise.530 if (T->isLValueReferenceType())531 return Cl::CL_LValue;532 const auto *RV = T->getAs<RValueReferenceType>();533 if (!RV) // Could still be a class temporary, though.534 return ClassifyTemporary(T);535 536 return RV->getPointeeType()->isFunctionType() ? Cl::CL_LValue : Cl::CL_XValue;537}538 539static Cl::Kinds ClassifyMemberExpr(ASTContext &Ctx, const MemberExpr *E) {540 if (E->getType() == Ctx.UnknownAnyTy)541 return (isa<FunctionDecl>(E->getMemberDecl())542 ? Cl::CL_PRValue : Cl::CL_LValue);543 544 // Handle C first, it's easier.545 if (!Ctx.getLangOpts().CPlusPlus) {546 // C99 6.5.2.3p3547 // For dot access, the expression is an lvalue if the first part is. For548 // arrow access, it always is an lvalue.549 if (E->isArrow())550 return Cl::CL_LValue;551 // ObjC property accesses are not lvalues, but get special treatment.552 Expr *Base = E->getBase()->IgnoreParens();553 if (isa<ObjCPropertyRefExpr>(Base))554 return Cl::CL_SubObjCPropertySetting;555 return ClassifyInternal(Ctx, Base);556 }557 558 NamedDecl *Member = E->getMemberDecl();559 // C++ [expr.ref]p3: E1->E2 is converted to the equivalent form (*(E1)).E2.560 // C++ [expr.ref]p4: If E2 is declared to have type "reference to T", then561 // E1.E2 is an lvalue.562 if (const auto *Value = dyn_cast<ValueDecl>(Member))563 if (Value->getType()->isReferenceType())564 return Cl::CL_LValue;565 566 // Otherwise, one of the following rules applies.567 // -- If E2 is a static member [...] then E1.E2 is an lvalue.568 if (isa<VarDecl>(Member) && Member->getDeclContext()->isRecord())569 return Cl::CL_LValue;570 571 // -- If E2 is a non-static data member [...]. If E1 is an lvalue, then572 // E1.E2 is an lvalue; if E1 is an xvalue, then E1.E2 is an xvalue;573 // otherwise, it is a prvalue.574 if (isa<FieldDecl>(Member)) {575 // *E1 is an lvalue576 if (E->isArrow())577 return Cl::CL_LValue;578 Expr *Base = E->getBase()->IgnoreParenImpCasts();579 if (isa<ObjCPropertyRefExpr>(Base))580 return Cl::CL_SubObjCPropertySetting;581 return ClassifyInternal(Ctx, E->getBase());582 }583 584 // -- If E2 is a [...] member function, [...]585 // -- If it refers to a static member function [...], then E1.E2 is an586 // lvalue; [...]587 // -- Otherwise [...] E1.E2 is a prvalue.588 if (const auto *Method = dyn_cast<CXXMethodDecl>(Member)) {589 if (Method->isStatic())590 return Cl::CL_LValue;591 if (Method->isImplicitObjectMemberFunction())592 return Cl::CL_MemberFunction;593 return Cl::CL_PRValue;594 }595 596 // -- If E2 is a member enumerator [...], the expression E1.E2 is a prvalue.597 // So is everything else we haven't handled yet.598 return Cl::CL_PRValue;599}600 601static Cl::Kinds ClassifyBinaryOp(ASTContext &Ctx, const BinaryOperator *E) {602 assert(Ctx.getLangOpts().CPlusPlus &&603 "This is only relevant for C++.");604 605 // For binary operators which are unknown due to type dependence, the606 // convention is to classify them as a prvalue. This does not matter much, but607 // it needs to agree with how they are created.608 if (E->getType() == Ctx.DependentTy)609 return Cl::CL_PRValue;610 611 // C++ [expr.ass]p1: All [...] return an lvalue referring to the left operand.612 // Except we override this for writes to ObjC properties.613 if (E->isAssignmentOp())614 return (E->getLHS()->getObjectKind() == OK_ObjCProperty615 ? Cl::CL_PRValue : Cl::CL_LValue);616 617 // C++ [expr.comma]p1: the result is of the same value category as its right618 // operand, [...].619 if (E->getOpcode() == BO_Comma)620 return ClassifyInternal(Ctx, E->getRHS());621 622 // C++ [expr.mptr.oper]p6: The result of a .* expression whose second operand623 // is a pointer to a data member is of the same value category as its first624 // operand.625 if (E->getOpcode() == BO_PtrMemD)626 return (E->getType()->isFunctionType() ||627 E->hasPlaceholderType(BuiltinType::BoundMember))628 ? Cl::CL_MemberFunction629 : ClassifyInternal(Ctx, E->getLHS());630 631 // C++ [expr.mptr.oper]p6: The result of an ->* expression is an lvalue if its632 // second operand is a pointer to data member and a prvalue otherwise.633 if (E->getOpcode() == BO_PtrMemI)634 return (E->getType()->isFunctionType() ||635 E->hasPlaceholderType(BuiltinType::BoundMember))636 ? Cl::CL_MemberFunction637 : Cl::CL_LValue;638 639 // All other binary operations are prvalues.640 return Cl::CL_PRValue;641}642 643static Cl::Kinds ClassifyConditional(ASTContext &Ctx, const Expr *True,644 const Expr *False) {645 assert(Ctx.getLangOpts().CPlusPlus &&646 "This is only relevant for C++.");647 648 // C++ [expr.cond]p2649 // If either the second or the third operand has type (cv) void,650 // one of the following shall hold:651 if (True->getType()->isVoidType() || False->getType()->isVoidType()) {652 // The second or the third operand (but not both) is a (possibly653 // parenthesized) throw-expression; the result is of the [...] value654 // category of the other.655 bool TrueIsThrow = isa<CXXThrowExpr>(True->IgnoreParenImpCasts());656 bool FalseIsThrow = isa<CXXThrowExpr>(False->IgnoreParenImpCasts());657 if (const Expr *NonThrow = TrueIsThrow ? (FalseIsThrow ? nullptr : False)658 : (FalseIsThrow ? True : nullptr))659 return ClassifyInternal(Ctx, NonThrow);660 661 // [Otherwise] the result [...] is a prvalue.662 return Cl::CL_PRValue;663 }664 665 // Note that at this point, we have already performed all conversions666 // according to [expr.cond]p3.667 // C++ [expr.cond]p4: If the second and third operands are glvalues of the668 // same value category [...], the result is of that [...] value category.669 // C++ [expr.cond]p5: Otherwise, the result is a prvalue.670 Cl::Kinds LCl = ClassifyInternal(Ctx, True),671 RCl = ClassifyInternal(Ctx, False);672 return LCl == RCl ? LCl : Cl::CL_PRValue;673}674 675static Cl::ModifiableType IsModifiable(ASTContext &Ctx, const Expr *E,676 Cl::Kinds Kind, SourceLocation &Loc) {677 // As a general rule, we only care about lvalues. But there are some rvalues678 // for which we want to generate special results.679 if (Kind == Cl::CL_PRValue) {680 // For the sake of better diagnostics, we want to specifically recognize681 // use of the GCC cast-as-lvalue extension.682 if (const auto *CE = dyn_cast<ExplicitCastExpr>(E->IgnoreParens())) {683 if (CE->getSubExpr()->IgnoreParenImpCasts()->isLValue()) {684 Loc = CE->getExprLoc();685 return Cl::CM_LValueCast;686 }687 }688 }689 if (Kind != Cl::CL_LValue)690 return Cl::CM_RValue;691 692 // This is the lvalue case.693 // Functions are lvalues in C++, but not modifiable. (C++ [basic.lval]p6)694 if (Ctx.getLangOpts().CPlusPlus && E->getType()->isFunctionType())695 return Cl::CM_Function;696 697 // Assignment to a property in ObjC is an implicit setter access. But a698 // setter might not exist.699 if (const auto *Expr = dyn_cast<ObjCPropertyRefExpr>(E)) {700 if (Expr->isImplicitProperty() &&701 Expr->getImplicitPropertySetter() == nullptr)702 return Cl::CM_NoSetterProperty;703 }704 705 CanQualType CT = Ctx.getCanonicalType(E->getType());706 // Const stuff is obviously not modifiable.707 if (CT.isConstQualified())708 return Cl::CM_ConstQualified;709 if (Ctx.getLangOpts().OpenCL &&710 CT.getQualifiers().getAddressSpace() == LangAS::opencl_constant)711 return Cl::CM_ConstAddrSpace;712 713 // Arrays are not modifiable, only their elements are.714 if (CT->isArrayType() &&715 !(Ctx.getLangOpts().HLSL && CT->isConstantArrayType()))716 return Cl::CM_ArrayType;717 // Incomplete types are not modifiable.718 if (CT->isIncompleteType())719 return Cl::CM_IncompleteType;720 721 // Records with any const fields (recursively) are not modifiable.722 if (const RecordType *R = CT->getAs<RecordType>())723 if (R->hasConstFields())724 return Cl::CM_ConstQualifiedField;725 726 return Cl::CM_Modifiable;727}728 729Expr::LValueClassification Expr::ClassifyLValue(ASTContext &Ctx) const {730 Classification VC = Classify(Ctx);731 switch (VC.getKind()) {732 case Cl::CL_LValue: return LV_Valid;733 case Cl::CL_XValue: return LV_InvalidExpression;734 case Cl::CL_Function: return LV_NotObjectType;735 case Cl::CL_Void: return LV_InvalidExpression;736 case Cl::CL_AddressableVoid: return LV_IncompleteVoidType;737 case Cl::CL_DuplicateVectorComponents: return LV_DuplicateVectorComponents;738 case Cl::CL_MemberFunction: return LV_MemberFunction;739 case Cl::CL_SubObjCPropertySetting: return LV_SubObjCPropertySetting;740 case Cl::CL_ClassTemporary: return LV_ClassTemporary;741 case Cl::CL_ArrayTemporary: return LV_ArrayTemporary;742 case Cl::CL_ObjCMessageRValue: return LV_InvalidMessageExpression;743 case Cl::CL_PRValue: return LV_InvalidExpression;744 }745 llvm_unreachable("Unhandled kind");746}747 748Expr::isModifiableLvalueResult749Expr::isModifiableLvalue(ASTContext &Ctx, SourceLocation *Loc) const {750 SourceLocation dummy;751 Classification VC = ClassifyModifiable(Ctx, Loc ? *Loc : dummy);752 switch (VC.getKind()) {753 case Cl::CL_LValue: break;754 case Cl::CL_XValue: return MLV_InvalidExpression;755 case Cl::CL_Function: return MLV_NotObjectType;756 case Cl::CL_Void: return MLV_InvalidExpression;757 case Cl::CL_AddressableVoid: return MLV_IncompleteVoidType;758 case Cl::CL_DuplicateVectorComponents: return MLV_DuplicateVectorComponents;759 case Cl::CL_MemberFunction: return MLV_MemberFunction;760 case Cl::CL_SubObjCPropertySetting: return MLV_SubObjCPropertySetting;761 case Cl::CL_ClassTemporary: return MLV_ClassTemporary;762 case Cl::CL_ArrayTemporary: return MLV_ArrayTemporary;763 case Cl::CL_ObjCMessageRValue: return MLV_InvalidMessageExpression;764 case Cl::CL_PRValue:765 return VC.getModifiable() == Cl::CM_LValueCast ?766 MLV_LValueCast : MLV_InvalidExpression;767 }768 assert(VC.getKind() == Cl::CL_LValue && "Unhandled kind");769 switch (VC.getModifiable()) {770 case Cl::CM_Untested: llvm_unreachable("Did not test modifiability");771 case Cl::CM_Modifiable: return MLV_Valid;772 case Cl::CM_RValue: llvm_unreachable("CM_RValue and CL_LValue don't match");773 case Cl::CM_Function: return MLV_NotObjectType;774 case Cl::CM_LValueCast:775 llvm_unreachable("CM_LValueCast and CL_LValue don't match");776 case Cl::CM_NoSetterProperty: return MLV_NoSetterProperty;777 case Cl::CM_ConstQualified: return MLV_ConstQualified;778 case Cl::CM_ConstQualifiedField: return MLV_ConstQualifiedField;779 case Cl::CM_ConstAddrSpace: return MLV_ConstAddrSpace;780 case Cl::CM_ArrayType: return MLV_ArrayType;781 case Cl::CM_IncompleteType: return MLV_IncompleteType;782 }783 llvm_unreachable("Unhandled modifiable type");784}785