I don't see how the resolution of Core Issue 2140 changes the status of nullptr_t lvalue-to-rvalue conversion for constexpr evaluation. PR42440 has been opened concerning the change to constexpr evaluation.
-- HT On Fri, Jun 14, 2019 at 1:43 PM Richard Smith via cfe-commits < cfe-commits@lists.llvm.org> wrote: > Author: rsmith > Date: Fri Jun 14 10:46:38 2019 > New Revision: 363429 > > URL: http://llvm.org/viewvc/llvm-project?rev=363429&view=rev > Log: > PR23833, DR2140: an lvalue-to-rvalue conversion on a glvalue of type > nullptr_t does not access memory. > > We now reuse CK_NullToPointer to represent a conversion from a glvalue > of type nullptr_t to a prvalue of nullptr_t where necessary. > > This reinstates r363337, reverted in r363352. > > Modified: > cfe/trunk/lib/AST/Expr.cpp > cfe/trunk/lib/CodeGen/CGExprAgg.cpp > cfe/trunk/lib/CodeGen/CGExprScalar.cpp > cfe/trunk/lib/Sema/SemaExpr.cpp > cfe/trunk/lib/Sema/SemaInit.cpp > cfe/trunk/lib/StaticAnalyzer/Core/ExprEngineC.cpp > cfe/trunk/test/Analysis/nullptr.cpp > cfe/trunk/test/CXX/drs/dr21xx.cpp > cfe/trunk/test/CodeGenCXX/nullptr.cpp > cfe/trunk/www/cxx_dr_status.html > > Modified: cfe/trunk/lib/AST/Expr.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/AST/Expr.cpp?rev=363429&r1=363428&r2=363429&view=diff > > ============================================================================== > --- cfe/trunk/lib/AST/Expr.cpp (original) > +++ cfe/trunk/lib/AST/Expr.cpp Fri Jun 14 10:46:38 2019 > @@ -1885,6 +1885,11 @@ ImplicitCastExpr *ImplicitCastExpr::Crea > ExprValueKind VK) { > unsigned PathSize = (BasePath ? BasePath->size() : 0); > void *Buffer = C.Allocate(totalSizeToAlloc<CXXBaseSpecifier > *>(PathSize)); > + // Per C++ [conv.lval]p3, lvalue-to-rvalue conversions on class and > + // std::nullptr_t have special semantics not captured by > CK_LValueToRValue. > + assert((Kind != CK_LValueToRValue || > + !(T->isNullPtrType() || T->getAsCXXRecordDecl())) && > + "invalid type for lvalue-to-rvalue conversion"); > ImplicitCastExpr *E = > new (Buffer) ImplicitCastExpr(T, Kind, Operand, PathSize, VK); > if (PathSize) > > Modified: cfe/trunk/lib/CodeGen/CGExprAgg.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprAgg.cpp?rev=363429&r1=363428&r2=363429&view=diff > > ============================================================================== > --- cfe/trunk/lib/CodeGen/CGExprAgg.cpp (original) > +++ cfe/trunk/lib/CodeGen/CGExprAgg.cpp Fri Jun 14 10:46:38 2019 > @@ -1352,7 +1352,8 @@ static bool isSimpleZero(const Expr *E, > // (int*)0 - Null pointer expressions. > if (const CastExpr *ICE = dyn_cast<CastExpr>(E)) > return ICE->getCastKind() == CK_NullToPointer && > - CGF.getTypes().isPointerZeroInitializable(E->getType()); > + CGF.getTypes().isPointerZeroInitializable(E->getType()) && > + !E->HasSideEffects(CGF.getContext()); > // '\0' > if (const CharacterLiteral *CL = dyn_cast<CharacterLiteral>(E)) > return CL->getValue() == 0; > > Modified: cfe/trunk/lib/CodeGen/CGExprScalar.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/CodeGen/CGExprScalar.cpp?rev=363429&r1=363428&r2=363429&view=diff > > ============================================================================== > --- cfe/trunk/lib/CodeGen/CGExprScalar.cpp (original) > +++ cfe/trunk/lib/CodeGen/CGExprScalar.cpp Fri Jun 14 10:46:38 2019 > @@ -2148,14 +2148,14 @@ Value *ScalarExprEmitter::VisitCastExpr( > > case CK_NullToPointer: > if (MustVisitNullValue(E)) > - (void) Visit(E); > + CGF.EmitIgnoredExpr(E); > > return > CGF.CGM.getNullPointer(cast<llvm::PointerType>(ConvertType(DestTy)), > DestTy); > > case CK_NullToMemberPointer: { > if (MustVisitNullValue(E)) > - (void) Visit(E); > + CGF.EmitIgnoredExpr(E); > > const MemberPointerType *MPT = > CE->getType()->getAs<MemberPointerType>(); > return CGF.CGM.getCXXABI().EmitNullMemberPointer(MPT); > > Modified: cfe/trunk/lib/Sema/SemaExpr.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaExpr.cpp?rev=363429&r1=363428&r2=363429&view=diff > > ============================================================================== > --- cfe/trunk/lib/Sema/SemaExpr.cpp (original) > +++ cfe/trunk/lib/Sema/SemaExpr.cpp Fri Jun 14 10:46:38 2019 > @@ -635,8 +635,10 @@ ExprResult Sema::DefaultLvalueConversion > if (E->getType().getObjCLifetime() == Qualifiers::OCL_Weak) > Cleanup.setExprNeedsCleanups(true); > > - Res = ImplicitCastExpr::Create(Context, T, CK_LValueToRValue, E, > nullptr, > - VK_RValue); > + // C++ [conv.lval]p3: > + // If T is cv std::nullptr_t, the result is a null pointer constant. > + CastKind CK = T->isNullPtrType() ? CK_NullToPointer : CK_LValueToRValue; > + Res = ImplicitCastExpr::Create(Context, T, CK, E, nullptr, VK_RValue); > > // C11 6.3.2.1p2: > // ... if the lvalue has atomic type, the value has the non-atomic > version > > Modified: cfe/trunk/lib/Sema/SemaInit.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/Sema/SemaInit.cpp?rev=363429&r1=363428&r2=363429&view=diff > > ============================================================================== > --- cfe/trunk/lib/Sema/SemaInit.cpp (original) > +++ cfe/trunk/lib/Sema/SemaInit.cpp Fri Jun 14 10:46:38 2019 > @@ -7779,9 +7779,13 @@ ExprResult InitializationSequence::Perfo > > case SK_LValueToRValue: { > assert(CurInit.get()->isGLValue() && "cannot load from a prvalue"); > - CurInit = ImplicitCastExpr::Create(S.Context, Step->Type, > - CK_LValueToRValue, CurInit.get(), > - /*BasePath=*/nullptr, VK_RValue); > + // C++ [conv.lval]p3: > + // If T is cv std::nullptr_t, the result is a null pointer > constant. > + CastKind CK = > + Step->Type->isNullPtrType() ? CK_NullToPointer : > CK_LValueToRValue; > + CurInit = > + ImplicitCastExpr::Create(S.Context, Step->Type, CK, > CurInit.get(), > + /*BasePath=*/nullptr, VK_RValue); > break; > } > > > Modified: cfe/trunk/lib/StaticAnalyzer/Core/ExprEngineC.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/lib/StaticAnalyzer/Core/ExprEngineC.cpp?rev=363429&r1=363428&r2=363429&view=diff > > ============================================================================== > --- cfe/trunk/lib/StaticAnalyzer/Core/ExprEngineC.cpp (original) > +++ cfe/trunk/lib/StaticAnalyzer/Core/ExprEngineC.cpp Fri Jun 14 10:46:38 > 2019 > @@ -378,7 +378,6 @@ void ExprEngine::VisitCast(const CastExp > case CK_BitCast: > case CK_AddressSpaceConversion: > case CK_BooleanToSignedIntegral: > - case CK_NullToPointer: > case CK_IntegralToPointer: > case CK_PointerToIntegral: { > SVal V = state->getSVal(Ex, LCtx); > @@ -503,6 +502,12 @@ void ExprEngine::VisitCast(const CastExp > Bldr.generateNode(CastE, Pred, state); > continue; > } > + case CK_NullToPointer: { > + SVal V = svalBuilder.makeNull(); > + state = state->BindExpr(CastE, LCtx, V); > + Bldr.generateNode(CastE, Pred, state); > + continue; > + } > case CK_NullToMemberPointer: { > SVal V = svalBuilder.getMemberPointer(nullptr); > state = state->BindExpr(CastE, LCtx, V); > > Modified: cfe/trunk/test/Analysis/nullptr.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/test/Analysis/nullptr.cpp?rev=363429&r1=363428&r2=363429&view=diff > > ============================================================================== > --- cfe/trunk/test/Analysis/nullptr.cpp (original) > +++ cfe/trunk/test/Analysis/nullptr.cpp Fri Jun 14 10:46:38 2019 > @@ -128,18 +128,10 @@ void shouldNotCrash() { > decltype(nullptr) p; // expected-note{{'p' declared without an initial > value}} > if (getSymbol()) // expected-note {{Assuming the condition is false}} > // expected-note@-1{{Taking false branch}} > - // expected-note@-2{{Assuming the condition is false}} > - // expected-note@-3{{Taking false branch}} > - // expected-note@-4{{Assuming the condition is true}} > - // expected-note@-5{{Taking true branch}} > - invokeF(p); // expected-warning{{1st function call argument is an > uninitialized value}} > - // expected-note@-1{{1st function call argument is an > uninitialized value}} > - if (getSymbol()) // expected-note {{Assuming the condition is false}} > - // expected-note@-1{{Taking false branch}} > // expected-note@-2{{Assuming the condition is true}} > // expected-note@-3{{Taking true branch}} > - invokeF(nullptr); // expected-note {{Calling 'invokeF'}} > - // expected-note@-1{{Passing null pointer value > via 1st parameter 'x'}} > + invokeF(p); // expected-note {{Calling 'invokeF'}} > + // expected-note@-1{{Passing null pointer value via > 1st parameter 'x'}} > if (getSymbol()) { // expected-note {{Assuming the condition is true}} > // expected-note@-1{{Taking true branch}} > X *xx = Type().x; // expected-note {{Null pointer value stored to > field 'x'}} > > Modified: cfe/trunk/test/CXX/drs/dr21xx.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CXX/drs/dr21xx.cpp?rev=363429&r1=363428&r2=363429&view=diff > > ============================================================================== > --- cfe/trunk/test/CXX/drs/dr21xx.cpp (original) > +++ cfe/trunk/test/CXX/drs/dr21xx.cpp Fri Jun 14 10:46:38 2019 > @@ -32,6 +32,16 @@ namespace dr2120 { // dr2120: 7 > static_assert(!__is_standard_layout(E), ""); > } > > +namespace dr2140 { // dr2140: 9 > +#if __cplusplus >= 201103L > + union U { int a; decltype(nullptr) b; }; > + constexpr int *test(U u) { > + return u.b; > + } > + static_assert(!test({123}), "u.b should be valid even when b is > inactive"); > +#endif > +} > + > namespace dr2170 { // dr2170: 9 > #if __cplusplus >= 201103L > void f() { > > Modified: cfe/trunk/test/CodeGenCXX/nullptr.cpp > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/test/CodeGenCXX/nullptr.cpp?rev=363429&r1=363428&r2=363429&view=diff > > ============================================================================== > --- cfe/trunk/test/CodeGenCXX/nullptr.cpp (original) > +++ cfe/trunk/test/CodeGenCXX/nullptr.cpp Fri Jun 14 10:46:38 2019 > @@ -22,3 +22,50 @@ void g() { > const std::type_info& f2() { > return typeid(nullptr_t); > } > + > +union U { > + int n; > + nullptr_t b; > +}; > +// CHECK-LABEL: define {{.*}}pr23833_a > +// CHECK: store > +// CHECK: load > +// CHECK-NOT: load > +// CHECK: ret i1 false > +bool pr23833_a(U &u) { return u.b; } > + > +// CHECK-LABEL: define {{.*}}pr23833_b > +// CHECK: store > +// CHECK: load > +// CHECK-NOT: load > +// CHECK: ret i8* null > +nullptr_t pr23833_b(nullptr_t &n) { return n; } > + > +struct X1 { operator int*(); }; > +struct X2 { operator const nullptr_t&(); }; > + > +// CHECK-LABEL: define {{.*}}pr23833_c > +// CHECK: call {{.*}}X1 > +// CHECK: call {{.*}}X2 > +// CHECK-NOT: load > +// CHECK: ret i32 > +int pr23833_c() { > + return X1() != X2(); > +} > + > +// CHECK-LABEL: define {{.*}}pr23833_d > +// CHECK: call {{.*}}X2 > +// CHECK-NOT: load > +// CHECK: store > +// CHECK: load > +// CHECK: ret i32* > +int *pr23833_d() { > + int *p = X2(); > + return p; > +} > + > +namespace PR39528 { > + constexpr nullptr_t null = nullptr; > + void f(nullptr_t); > + void g() { f(null); } > +} > > Modified: cfe/trunk/www/cxx_dr_status.html > URL: > http://llvm.org/viewvc/llvm-project/cfe/trunk/www/cxx_dr_status.html?rev=363429&r1=363428&r2=363429&view=diff > > ============================================================================== > --- cfe/trunk/www/cxx_dr_status.html (original) > +++ cfe/trunk/www/cxx_dr_status.html Fri Jun 14 10:46:38 2019 > @@ -12655,7 +12655,7 @@ and <I>POD class</I></td> > <td><a href="http://wg21.link/cwg2140";>2140</a></td> > <td>CD4</td> > <td>Lvalue-to-rvalue conversion of <TT>std::nullptr_t</TT></td> > - <td class="none" align="center">Unknown</td> > + <td class="svn" align="center">SVN</td> > </tr> > <tr id="2141"> > <td><a href="http://wg21.link/cwg2141";>2141</a></td> > > > _______________________________________________ > cfe-commits mailing list > cfe-commits@lists.llvm.org > https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits >
_______________________________________________ cfe-commits mailing list cfe-commits@lists.llvm.org https://lists.llvm.org/cgi-bin/mailman/listinfo/cfe-commits
