rsmith created this revision.
rsmith added reviewers: aaron.ballman, rnk.
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rsmith requested review of this revision.
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We still require these functions to be declared before they can be used,
but don't instantiate their definitions unless their addresses are
taken. Instead, code generation, constant evaluation, and static
analysis are given direct knowledge of their effect.
This change aims to reduce various costs associated with these functions
- per-instantiation memory costs, compile time and memory costs due to
creating out-of-line copies and inlining them, code size at -O0, and so
on -- so that they are not substantially more expensive than a cast.
Most of these improvements are very small, but I measured a 3% decrease
in -O0 object file size for a simple C++ source file using the standard
library after this change.
We now automatically infer the `const` and `nothrow` attributes on these
now-builtin functions, in particular meaning that we get a warning for
an unused call to one of these functions.
In C++20 onwards, we disallow taking the addresses of these functions,
per the C++20 "addressable function" rule. In earlier language modes, a
compatibility warning is produced but the address can still be taken.
The same infrastructure is extended to the existing MSVC builtin
`__GetExceptionInfo`, which is now only recognized in namespace `std`
like it always should have been.
Repository:
rG LLVM Github Monorepo
https://reviews.llvm.org/D123345
Files:
clang/docs/ReleaseNotes.rst
clang/include/clang/Basic/Builtins.def
clang/include/clang/Basic/Builtins.h
clang/include/clang/Basic/DiagnosticSemaKinds.td
clang/lib/AST/ExprConstant.cpp
clang/lib/Analysis/BodyFarm.cpp
clang/lib/Basic/Builtins.cpp
clang/lib/CodeGen/CGBuiltin.cpp
clang/lib/Sema/SemaChecking.cpp
clang/lib/Sema/SemaDecl.cpp
clang/lib/Sema/SemaExpr.cpp
clang/lib/Sema/SemaExprCXX.cpp
clang/lib/Sema/SemaInit.cpp
clang/lib/Sema/SemaLookup.cpp
clang/lib/Sema/SemaOverload.cpp
clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
clang/test/Analysis/use-after-move.cpp
clang/test/CodeGenCXX/builtin-std-move.cpp
clang/test/CodeGenCXX/microsoft-abi-throw.cpp
clang/test/SemaCXX/builtin-std-move.cpp
clang/test/SemaCXX/unqualified-std-call-fixits.cpp
clang/test/SemaCXX/unqualified-std-call.cpp
clang/test/SemaCXX/warn-consumed-analysis.cpp
Index: clang/test/SemaCXX/warn-consumed-analysis.cpp
===================================================================
--- clang/test/SemaCXX/warn-consumed-analysis.cpp
+++ clang/test/SemaCXX/warn-consumed-analysis.cpp
@@ -953,12 +953,12 @@
namespace std {
void move();
template<class T>
- void move(T&&);
+ T &&move(T&);
namespace __1 {
void move();
template<class T>
- void move(T&&);
+ T &&move(T&);
}
}
@@ -971,7 +971,7 @@
void test() {
x.move();
std::move();
- std::move(x);
+ std::move(x); // expected-warning {{ignoring return value}}
std::__1::move();
std::__1::move(x);
}
Index: clang/test/SemaCXX/unqualified-std-call.cpp
===================================================================
--- clang/test/SemaCXX/unqualified-std-call.cpp
+++ clang/test/SemaCXX/unqualified-std-call.cpp
@@ -1,17 +1,17 @@
-// RUN: %clang_cc1 -fsyntax-only -verify -Wall -std=c++11 %s
+// RUN: %clang_cc1 -fsyntax-only -verify -Wall -std=c++11 %s -Wno-unused-value
namespace std {
template <typename T>
void dummy(T &&) {}
template <typename T>
-void move(T &&) {}
+T &&move(T &&x) { return x; }
template <typename T, typename U>
void move(T &&, U &&) {}
inline namespace __1 {
template <typename T>
-void forward(T &) {}
+T &forward(T &x) { return x; }
} // namespace __1
struct foo {};
Index: clang/test/SemaCXX/unqualified-std-call-fixits.cpp
===================================================================
--- clang/test/SemaCXX/unqualified-std-call-fixits.cpp
+++ clang/test/SemaCXX/unqualified-std-call-fixits.cpp
@@ -6,9 +6,9 @@
namespace std {
-void move(auto &&a) {}
+int &&move(auto &&a) { return a; }
-void forward(auto &a) {}
+int &&forward(auto &a) { return a; }
} // namespace std
@@ -16,8 +16,8 @@
void f() {
int i = 0;
- move(i); // expected-warning {{unqualified call to std::move}}
- // CHECK: {{^}} std::
- forward(i); // expected-warning {{unqualified call to std::forward}}
- // CHECK: {{^}} std::
+ (void)move(i); // expected-warning {{unqualified call to std::move}}
+ // CHECK: {{^}} (void)std::move
+ (void)forward(i); // expected-warning {{unqualified call to std::forward}}
+ // CHECK: {{^}} (void)std::forward
}
Index: clang/test/SemaCXX/builtin-std-move.cpp
===================================================================
--- /dev/null
+++ clang/test/SemaCXX/builtin-std-move.cpp
@@ -0,0 +1,90 @@
+// RUN: %clang_cc1 -std=c++17 -verify %s
+// RUN: %clang_cc1 -std=c++17 -verify %s -DNO_CONSTEXPR
+// RUN: %clang_cc1 -std=c++20 -verify %s
+
+namespace std {
+#ifndef NO_CONSTEXPR
+#define CONSTEXPR constexpr
+#else
+#define CONSTEXPR
+#endif
+
+ template<typename T> CONSTEXPR T &&move(T &x) {
+ static_assert(T::moveable, "instantiated move"); // expected-error {{no member named 'moveable' in 'B'}}
+ // expected-error@-1 {{no member named 'moveable' in 'C'}}
+ return static_cast<T&&>(x);
+ }
+
+ // Unrelated move functions are not the builtin.
+ template<typename T> CONSTEXPR int move(T, T) { return 5; }
+
+ template<typename T, bool Rref> struct ref { using type = T&; };
+ template<typename T> struct ref<T, true> { using type = T&&; };
+
+ template<typename T> CONSTEXPR auto move_if_noexcept(T &x) -> typename ref<T, noexcept(T(static_cast<T&&>(x)))>::type {
+ static_assert(T::moveable, "instantiated move_if_noexcept"); // expected-error {{no member named 'moveable' in 'B'}}
+ return static_cast<typename ref<T, noexcept(T(static_cast<T&&>(x)))>::type>(x);
+ }
+
+ template<typename T> struct remove_reference { using type = T; };
+ template<typename T> struct remove_reference<T&> { using type = T; };
+ template<typename T> struct remove_reference<T&&> { using type = T; };
+
+ template<typename T> CONSTEXPR T &&forward(typename remove_reference<T>::type &x) {
+ static_assert(T::moveable, "instantiated forward"); // expected-error {{no member named 'moveable' in 'B'}}
+ // expected-error@-1 {{no member named 'moveable' in 'C'}}
+ return static_cast<T&&>(x);
+ }
+}
+
+// Note: this doesn't have a 'moveable' member. Instantiation of the above
+// functions will fail if it's attempted.
+struct A {};
+constexpr bool f(A a) { // #f
+ A &&move = std::move(a); // #call
+ A &&move_if_noexcept = std::move_if_noexcept(a);
+ A &&forward1 = std::forward<A>(a);
+ A &forward2 = std::forward<A&>(a);
+ return &move == &a && &move_if_noexcept == &a &&
+ &forward1 == &a && &forward2 == &a &&
+ std::move(a, a) == 5;
+}
+
+#ifndef NO_CONSTEXPR
+static_assert(f({}), "should be constexpr");
+#else
+// expected-error@#f {{never produces a constant expression}}
+// expected-note@#call {{}}
+#endif
+
+struct B {};
+B &&(*pMove)(B&) = std::move; // #1 expected-note {{instantiation of}}
+B &&(*pMoveIfNoexcept)(B&) = &std::move_if_noexcept; // #2 expected-note {{instantiation of}}
+B &&(*pForward)(B&) = &std::forward<B>; // #3 expected-note {{instantiation of}}
+int (*pUnrelatedMove)(B, B) = std::move;
+
+struct C {};
+C &&(&rMove)(C&) = std::move; // #4 expected-note {{instantiation of}}
+C &&(&rForward)(C&) = std::forward<C>; // #5 expected-note {{instantiation of}}
+int (&rUnrelatedMove)(B, B) = std::move;
+
+#if __cplusplus <= 201703L
+// expected-warning@#1 {{non-addressable}}
+// expected-warning@#2 {{non-addressable}}
+// expected-warning@#3 {{non-addressable}}
+// expected-warning@#4 {{non-addressable}}
+// expected-warning@#5 {{non-addressable}}
+#else
+// expected-error@#1 {{non-addressable}}
+// expected-error@#2 {{non-addressable}}
+// expected-error@#3 {{non-addressable}}
+// expected-error@#4 {{non-addressable}}
+// expected-error@#5 {{non-addressable}}
+#endif
+
+void attribute_const() {
+ int n;
+ std::move(n); // expected-warning {{ignoring return value}}
+ std::move_if_noexcept(n); // expected-warning {{ignoring return value}}
+ std::forward<int>(n); // expected-warning {{ignoring return value}}
+}
Index: clang/test/CodeGenCXX/microsoft-abi-throw.cpp
===================================================================
--- clang/test/CodeGenCXX/microsoft-abi-throw.cpp
+++ clang/test/CodeGenCXX/microsoft-abi-throw.cpp
@@ -1,5 +1,4 @@
// RUN: %clang_cc1 -emit-llvm -o - -triple=i386-pc-win32 -std=c++11 %s -fcxx-exceptions -fms-extensions | FileCheck %s
-// RUN: %clang_cc1 -emit-llvm -o - -triple=i386-pc-win32 -std=c++11 %s -fcxx-exceptions -fms-extensions -DSTD | FileCheck %s
// CHECK-DAG: @"??_R0?AUY@@@8" = linkonce_odr global %rtti.TypeDescriptor7 { i8** @"??_7type_info@@6B@", i8* null, [8 x i8] c".?AUY@@\00" }, comdat
// CHECK-DAG: @"_CT??_R0?AUY@@@8??0Y@@QAE@ABU0@@Z8" = linkonce_odr unnamed_addr constant %eh.CatchableType { i32 4, i8* bitcast (%rtti.TypeDescriptor7* @"??_R0?AUY@@@8" to i8*), i32 0, i32 -1, i32 0, i32 8, i8* bitcast (%struct.Y* (%struct.Y*, %struct.Y*, i32)* @"??0Y@@QAE@ABU0@@Z" to i8*) }, section ".xdata", comdat
@@ -134,15 +133,10 @@
throw nullptr;
}
-#ifdef STD
namespace std {
template <typename T>
void *__GetExceptionInfo(T);
}
-#else
-template <typename T>
-void *__GetExceptionInfo(T);
-#endif
using namespace std;
void *GetExceptionInfo_test0() {
Index: clang/test/CodeGenCXX/builtin-std-move.cpp
===================================================================
--- /dev/null
+++ clang/test/CodeGenCXX/builtin-std-move.cpp
@@ -0,0 +1,52 @@
+// RUN: %clang_cc1 -triple=x86_64-linux-gnu -emit-llvm -o - -std=c++17 %s | FileCheck %s --implicit-check-not=@_ZSt4move
+
+namespace std {
+ template<typename T> constexpr T &&move(T &val) { return static_cast<T&&>(val); }
+ template<typename T> constexpr T &&move_if_noexcept(T &val);
+ template<typename T> constexpr T &&forward(T &val);
+
+ // Not the builtin.
+ template<typename T, typename U> T move(U source, U source_end, T dest);
+}
+
+class T {};
+extern "C" void take(T &&);
+
+T a;
+
+// Check emission of a constant-evaluated call.
+// CHECK-DAG: @move_a = constant %[[T:.*]]* @a
+T &&move_a = std::move(a);
+// CHECK-DAG: @move_if_noexcept_a = constant %[[T]]* @a
+T &&move_if_noexcept_a = std::move_if_noexcept(a);
+// CHECK-DAG: @forward_a = constant %[[T]]* @a
+T &forward_a = std::forward<T&>(a);
+
+// Check emission of a non-constant call.
+// CHECK-LABEL: define {{.*}} void @test
+extern "C" void test(T &t) {
+ // CHECK: store %[[T]]* %{{.*}}, %[[T]]** %[[T_REF:[^,]*]]
+ // CHECK: %0 = load %[[T]]*, %[[T]]** %[[T_REF]]
+ // CHECK: call void @take(%[[T]]* {{.*}} %0)
+ take(std::move(t));
+ // CHECK: %1 = load %[[T]]*, %[[T]]** %[[T_REF]]
+ // CHECK: call void @take(%[[T]]* {{.*}} %1)
+ take(std::move_if_noexcept(t));
+ // CHECK: %2 = load %[[T]]*, %[[T]]** %[[T_REF]]
+ // CHECK: call void @take(%[[T]]* {{.*}} %2)
+ take(std::forward<T&&>(t));
+
+ // CHECK: call {{.*}} @_ZSt4moveI1TS0_ET_T0_S2_S1_
+ std::move(t, t, t);
+}
+
+// CHECK: declare {{.*}} @_ZSt4moveI1TS0_ET_T0_S2_S1_
+
+// Check that we instantiate and emit if the address is taken.
+// CHECK-LABEL: define {{.*}} @use_address
+extern "C" void *use_address() {
+ // CHECK: ret {{.*}} @_ZSt4moveIiEOT_RS0_
+ return (void*)&std::move<int>;
+}
+
+// CHECK: define {{.*}} i32* @_ZSt4moveIiEOT_RS0_(i32*
Index: clang/test/Analysis/use-after-move.cpp
===================================================================
--- clang/test/Analysis/use-after-move.cpp
+++ clang/test/Analysis/use-after-move.cpp
@@ -244,7 +244,7 @@
A a;
if (i == 1) { // peaceful-note 2 {{'i' is not equal to 1}}
// peaceful-note@-1 2 {{Taking false branch}}
- std::move(a);
+ (void)std::move(a);
}
if (i == 2) { // peaceful-note 2 {{'i' is not equal to 2}}
// peaceful-note@-1 2 {{Taking false branch}}
@@ -494,7 +494,7 @@
// Moves of global variables are not reported.
A global_a;
void globalVariablesTest() {
- std::move(global_a);
+ (void)std::move(global_a);
global_a.foo(); // no-warning
}
Index: clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
===================================================================
--- clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
+++ clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
@@ -4769,6 +4769,12 @@
if (TSK == TSK_ExplicitSpecialization)
return;
+ // Never implicitly instantiate a builtin; we don't actually need a function
+ // body.
+ if (Function->getBuiltinID() && TSK == TSK_ImplicitInstantiation &&
+ !DefinitionRequired)
+ return;
+
// Don't instantiate a definition if we already have one.
const FunctionDecl *ExistingDefn = nullptr;
if (Function->isDefined(ExistingDefn,
Index: clang/lib/Sema/SemaOverload.cpp
===================================================================
--- clang/lib/Sema/SemaOverload.cpp
+++ clang/lib/Sema/SemaOverload.cpp
@@ -1747,13 +1747,6 @@
"Non-address-of operator for overloaded function expression");
FromType = S.Context.getPointerType(FromType);
}
-
- // Check that we've computed the proper type after overload resolution.
- // FIXME: FixOverloadedFunctionReference has side-effects; we shouldn't
- // be calling it from within an NDEBUG block.
- assert(S.Context.hasSameType(
- FromType,
- S.FixOverloadedFunctionReference(From, AccessPair, Fn)->getType()));
} else {
return false;
}
@@ -15188,10 +15181,9 @@
if (SubExpr == UnOp->getSubExpr())
return UnOp;
- return UnaryOperator::Create(
- Context, SubExpr, UO_AddrOf, Context.getPointerType(SubExpr->getType()),
- VK_PRValue, OK_Ordinary, UnOp->getOperatorLoc(), false,
- CurFPFeatureOverrides());
+ // FIXME: This can't currently fail, but in principle it could.
+ return CreateBuiltinUnaryOp(UnOp->getOperatorLoc(), UO_AddrOf, SubExpr)
+ .get();
}
if (UnresolvedLookupExpr *ULE = dyn_cast<UnresolvedLookupExpr>(E)) {
@@ -15202,10 +15194,20 @@
TemplateArgs = &TemplateArgsBuffer;
}
- DeclRefExpr *DRE =
- BuildDeclRefExpr(Fn, Fn->getType(), VK_LValue, ULE->getNameInfo(),
- ULE->getQualifierLoc(), Found.getDecl(),
- ULE->getTemplateKeywordLoc(), TemplateArgs);
+ QualType Type = Fn->getType();
+ ExprValueKind ValueKind = getLangOpts().CPlusPlus ? VK_LValue : VK_PRValue;
+
+ // FIXME: Duplicated from BuildDeclarationNameExpr.
+ if (unsigned BID = Fn->getBuiltinID()) {
+ if (!Context.BuiltinInfo.isPredefinedLibFunction(BID)) {
+ Type = Context.BuiltinFnTy;
+ ValueKind = VK_PRValue;
+ }
+ }
+
+ DeclRefExpr *DRE = BuildDeclRefExpr(
+ Fn, Type, ValueKind, ULE->getNameInfo(), ULE->getQualifierLoc(),
+ Found.getDecl(), ULE->getTemplateKeywordLoc(), TemplateArgs);
DRE->setHadMultipleCandidates(ULE->getNumDecls() > 1);
return DRE;
}
Index: clang/lib/Sema/SemaLookup.cpp
===================================================================
--- clang/lib/Sema/SemaLookup.cpp
+++ clang/lib/Sema/SemaLookup.cpp
@@ -933,7 +933,8 @@
// In C++ and OpenCL (spec v1.2 s6.9.f), we don't have any predefined
// library functions like 'malloc'. Instead, we'll just error.
if ((getLangOpts().CPlusPlus || getLangOpts().OpenCL) &&
- Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID))
+ (Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID) ||
+ Context.BuiltinInfo.isInStdNamespace(BuiltinID)))
return false;
if (NamedDecl *D =
Index: clang/lib/Sema/SemaInit.cpp
===================================================================
--- clang/lib/Sema/SemaInit.cpp
+++ clang/lib/Sema/SemaInit.cpp
@@ -8189,6 +8189,10 @@
CurInit = S.FixOverloadedFunctionReference(CurInit,
Step->Function.FoundDecl,
Step->Function.Function);
+ // We might get back another placeholder expression if we resolved to a
+ // builtin.
+ if (!CurInit.isInvalid())
+ CurInit = S.CheckPlaceholderExpr(CurInit.get());
break;
case SK_CastDerivedToBasePRValue:
Index: clang/lib/Sema/SemaExprCXX.cpp
===================================================================
--- clang/lib/Sema/SemaExprCXX.cpp
+++ clang/lib/Sema/SemaExprCXX.cpp
@@ -4236,6 +4236,14 @@
return ExprError();
From = FixOverloadedFunctionReference(From, Found, Fn);
+
+ // We might get back another placeholder expression if we resolved to a
+ // builtin.
+ ExprResult Checked = CheckPlaceholderExpr(From);
+ if (Checked.isInvalid())
+ return ExprError();
+
+ From = Checked.get();
FromType = From->getType();
}
Index: clang/lib/Sema/SemaExpr.cpp
===================================================================
--- clang/lib/Sema/SemaExpr.cpp
+++ clang/lib/Sema/SemaExpr.cpp
@@ -20268,7 +20268,8 @@
auto *DRE = dyn_cast<DeclRefExpr>(E->IgnoreParenImpCasts());
if (DRE) {
auto *FD = cast<FunctionDecl>(DRE->getDecl());
- if (FD->getBuiltinID() == Builtin::BI__noop) {
+ unsigned BuiltinID = FD->getBuiltinID();
+ if (BuiltinID == Builtin::BI__noop) {
E = ImpCastExprToType(E, Context.getPointerType(FD->getType()),
CK_BuiltinFnToFnPtr)
.get();
@@ -20276,6 +20277,35 @@
VK_PRValue, SourceLocation(),
FPOptionsOverride());
}
+
+ if (Context.BuiltinInfo.isInStdNamespace(BuiltinID)) {
+ // Any use of these other than a direct call is ill-formed as of C++20,
+ // because they are not addressable functions. In earlier language
+ // modes, warn and force an instantiation of the real body.
+ Diag(E->getBeginLoc(), getLangOpts().CPlusPlus20
+ ? diag::err_use_of_unaddressable_function
+ : diag::warn_use_of_unaddressable_function);
+ if (FD->isImplicitlyInstantiable()) {
+ // Require a definition here because a normal attempt at
+ // instantiation for a builtin will be ignored, and we won't try
+ // again later. We assume that the definition of the template
+ // precedes this use.
+ InstantiateFunctionDefinition(E->getBeginLoc(), FD,
+ /*Recursive=*/false,
+ /*DefinitionRequired=*/true,
+ /*AtEndOfTU=*/false);
+ }
+ // Produce a properly-typed reference to the function.
+ CXXScopeSpec SS;
+ SS.Adopt(DRE->getQualifierLoc());
+ TemplateArgumentListInfo TemplateArgs;
+ DRE->copyTemplateArgumentsInto(TemplateArgs);
+ return BuildDeclRefExpr(
+ FD, FD->getType(), VK_LValue, DRE->getNameInfo(),
+ DRE->hasQualifier() ? &SS : nullptr, DRE->getFoundDecl(),
+ DRE->getTemplateKeywordLoc(),
+ DRE->hasExplicitTemplateArgs() ? &TemplateArgs : nullptr);
+ }
}
Diag(E->getBeginLoc(), diag::err_builtin_fn_use);
Index: clang/lib/Sema/SemaDecl.cpp
===================================================================
--- clang/lib/Sema/SemaDecl.cpp
+++ clang/lib/Sema/SemaDecl.cpp
@@ -9128,6 +9128,29 @@
return S;
}
+/// Determine whether a declaration matches a known function in namespace std.
+static bool isStdBuiltin(ASTContext &Ctx, FunctionDecl *FD,
+ unsigned BuiltinID) {
+ switch (BuiltinID) {
+ case Builtin::BI__GetExceptionInfo:
+ // No type checking whatsoever.
+ return Ctx.getTargetInfo().getCXXABI().isMicrosoft();
+
+ case Builtin::BImove:
+ case Builtin::BImove_if_noexcept:
+ case Builtin::BIforward: {
+ // Ensure that we don't treat the algorithm
+ // OutputIt std::move(InputIt, InputIt, OutputIt)
+ // as the builtin std::move.
+ const auto *FPT = FD->getType()->castAs<FunctionProtoType>();
+ return FPT->getNumParams() == 1 && !FPT->isVariadic();
+ }
+
+ default:
+ return false;
+ }
+}
+
NamedDecl*
Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
TypeSourceInfo *TInfo, LookupResult &Previous,
@@ -9978,28 +10001,30 @@
// If this is the first declaration of a library builtin function, add
// attributes as appropriate.
- if (!D.isRedeclaration() &&
- NewFD->getDeclContext()->getRedeclContext()->isFileContext()) {
+ if (!D.isRedeclaration()) {
if (IdentifierInfo *II = Previous.getLookupName().getAsIdentifierInfo()) {
if (unsigned BuiltinID = II->getBuiltinID()) {
- if (NewFD->getLanguageLinkage() == CLanguageLinkage) {
- // Validate the type matches unless this builtin is specified as
- // matching regardless of its declared type.
- if (Context.BuiltinInfo.allowTypeMismatch(BuiltinID)) {
- NewFD->addAttr(BuiltinAttr::CreateImplicit(Context, BuiltinID));
- } else {
- ASTContext::GetBuiltinTypeError Error;
- LookupNecessaryTypesForBuiltin(S, BuiltinID);
- QualType BuiltinType = Context.GetBuiltinType(BuiltinID, Error);
-
- if (!Error && !BuiltinType.isNull() &&
- Context.hasSameFunctionTypeIgnoringExceptionSpec(
- NewFD->getType(), BuiltinType))
+ bool InStdNamespace = Context.BuiltinInfo.isInStdNamespace(BuiltinID);
+ if (!InStdNamespace &&
+ NewFD->getDeclContext()->getRedeclContext()->isFileContext()) {
+ if (NewFD->getLanguageLinkage() == CLanguageLinkage) {
+ // Validate the type matches unless this builtin is specified as
+ // matching regardless of its declared type.
+ if (Context.BuiltinInfo.allowTypeMismatch(BuiltinID)) {
NewFD->addAttr(BuiltinAttr::CreateImplicit(Context, BuiltinID));
+ } else {
+ ASTContext::GetBuiltinTypeError Error;
+ LookupNecessaryTypesForBuiltin(S, BuiltinID);
+ QualType BuiltinType = Context.GetBuiltinType(BuiltinID, Error);
+
+ if (!Error && !BuiltinType.isNull() &&
+ Context.hasSameFunctionTypeIgnoringExceptionSpec(
+ NewFD->getType(), BuiltinType))
+ NewFD->addAttr(BuiltinAttr::CreateImplicit(Context, BuiltinID));
+ }
}
- } else if (BuiltinID == Builtin::BI__GetExceptionInfo &&
- Context.getTargetInfo().getCXXABI().isMicrosoft()) {
- // FIXME: We should consider this a builtin only in the std namespace.
+ } else if (InStdNamespace && NewFD->isInStdNamespace() &&
+ isStdBuiltin(Context, NewFD, BuiltinID)) {
NewFD->addAttr(BuiltinAttr::CreateImplicit(Context, BuiltinID));
}
}
@@ -14447,7 +14472,8 @@
// Builtin functions cannot be defined.
if (unsigned BuiltinID = FD->getBuiltinID()) {
if (!Context.BuiltinInfo.isPredefinedLibFunction(BuiltinID) &&
- !Context.BuiltinInfo.isPredefinedRuntimeFunction(BuiltinID)) {
+ !Context.BuiltinInfo.isPredefinedRuntimeFunction(BuiltinID) &&
+ !Context.BuiltinInfo.isInStdNamespace(BuiltinID)) {
Diag(FD->getLocation(), diag::err_builtin_definition) << FD;
FD->setInvalidDecl();
}
Index: clang/lib/Sema/SemaChecking.cpp
===================================================================
--- clang/lib/Sema/SemaChecking.cpp
+++ clang/lib/Sema/SemaChecking.cpp
@@ -2130,6 +2130,18 @@
TheCall->setType(Context.VoidPtrTy);
break;
+ case Builtin::BImove:
+ case Builtin::BImove_if_noexcept:
+ case Builtin::BIforward:
+ if (checkArgCount(*this, TheCall, 1))
+ return ExprError();
+ if (!Context.hasSameUnqualifiedType(TheCall->getType(),
+ TheCall->getArg(0)->getType())) {
+ Diag(TheCall->getBeginLoc(), diag::err_builtin_move_forward_unsupported)
+ << (BuiltinID == Builtin::BIforward);
+ return ExprError();
+ }
+ break;
// OpenCL v2.0, s6.13.16 - Pipe functions
case Builtin::BIread_pipe:
case Builtin::BIwrite_pipe:
Index: clang/lib/CodeGen/CGBuiltin.cpp
===================================================================
--- clang/lib/CodeGen/CGBuiltin.cpp
+++ clang/lib/CodeGen/CGBuiltin.cpp
@@ -4725,6 +4725,11 @@
}
break;
+ // C++ std:: builtins.
+ case Builtin::BImove:
+ case Builtin::BImove_if_noexcept:
+ case Builtin::BIforward:
+ return RValue::get(EmitLValue(E->getArg(0)).getPointer(*this));
case Builtin::BI__GetExceptionInfo: {
if (llvm::GlobalVariable *GV =
CGM.getCXXABI().getThrowInfo(FD->getParamDecl(0)->getType()))
Index: clang/lib/Basic/Builtins.cpp
===================================================================
--- clang/lib/Basic/Builtins.cpp
+++ clang/lib/Basic/Builtins.cpp
@@ -190,8 +190,7 @@
}
bool Builtin::Context::canBeRedeclared(unsigned ID) const {
- return ID == Builtin::NotBuiltin ||
- ID == Builtin::BI__va_start ||
- (!hasReferenceArgsOrResult(ID) &&
- !hasCustomTypechecking(ID));
+ return ID == Builtin::NotBuiltin || ID == Builtin::BI__va_start ||
+ (!hasReferenceArgsOrResult(ID) && !hasCustomTypechecking(ID)) ||
+ isInStdNamespace(ID);
}
Index: clang/lib/Analysis/BodyFarm.cpp
===================================================================
--- clang/lib/Analysis/BodyFarm.cpp
+++ clang/lib/Analysis/BodyFarm.cpp
@@ -20,6 +20,7 @@
#include "clang/AST/ExprObjC.h"
#include "clang/AST/NestedNameSpecifier.h"
#include "clang/Analysis/CodeInjector.h"
+#include "clang/Basic/Builtins.h"
#include "clang/Basic/OperatorKinds.h"
#include "llvm/ADT/StringSwitch.h"
#include "llvm/Support/Debug.h"
@@ -86,6 +87,9 @@
ImplicitCastExpr *makeImplicitCast(const Expr *Arg, QualType Ty,
CastKind CK = CK_LValueToRValue);
+ /// Create a cast to reference type.
+ CastExpr *makeReferenceCast(const Expr *Arg, QualType Ty);
+
/// Create an Objective-C bool literal.
ObjCBoolLiteralExpr *makeObjCBool(bool Val);
@@ -173,6 +177,16 @@
/* FPFeatures */ FPOptionsOverride());
}
+CastExpr *ASTMaker::makeReferenceCast(const Expr *Arg, QualType Ty) {
+ assert(Ty->isReferenceType());
+ return CXXStaticCastExpr::Create(
+ C, Ty.getNonReferenceType(),
+ Ty->isLValueReferenceType() ? VK_LValue : VK_XValue, CK_NoOp,
+ const_cast<Expr *>(Arg), /*CXXCastPath=*/nullptr,
+ /*Written=*/C.getTrivialTypeSourceInfo(Ty), FPOptionsOverride(),
+ SourceLocation(), SourceLocation(), SourceRange());
+}
+
Expr *ASTMaker::makeIntegralCast(const Expr *Arg, QualType Ty) {
if (Arg->getType() == Ty)
return const_cast<Expr*>(Arg);
@@ -296,6 +310,22 @@
/*FPFeatures=*/FPOptionsOverride());
}
+/// Create a fake body for 'std::move' or 'std::forward'. This is just:
+///
+/// \code
+/// return static_cast<return_type>(param);
+/// \endcode
+static Stmt *create_std_move_forward(ASTContext &C, const FunctionDecl *D) {
+ LLVM_DEBUG(llvm::dbgs() << "Generating body for std::move / std::forward\n");
+
+ ASTMaker M(C);
+
+ QualType ReturnType = D->getType()->castAs<FunctionType>()->getReturnType();
+ Expr *Param = M.makeDeclRefExpr(D->getParamDecl(0));
+ Expr *Cast = M.makeReferenceCast(Param, ReturnType);
+ return M.makeReturn(Cast);
+}
+
/// Create a fake body for std::call_once.
/// Emulates the following function body:
///
@@ -681,8 +711,19 @@
FunctionFarmer FF;
- if (Name.startswith("OSAtomicCompareAndSwap") ||
- Name.startswith("objc_atomicCompareAndSwap")) {
+ if (unsigned BuiltinID = D->getBuiltinID()) {
+ switch (BuiltinID) {
+ case Builtin::BImove:
+ case Builtin::BImove_if_noexcept:
+ case Builtin::BIforward:
+ FF = create_std_move_forward;
+ break;
+ default:
+ FF = nullptr;
+ break;
+ }
+ } else if (Name.startswith("OSAtomicCompareAndSwap") ||
+ Name.startswith("objc_atomicCompareAndSwap")) {
FF = create_OSAtomicCompareAndSwap;
} else if (Name == "call_once" && D->getDeclContext()->isStdNamespace()) {
FF = create_call_once;
Index: clang/lib/AST/ExprConstant.cpp
===================================================================
--- clang/lib/AST/ExprConstant.cpp
+++ clang/lib/AST/ExprConstant.cpp
@@ -8127,6 +8127,7 @@
bool VisitVarDecl(const Expr *E, const VarDecl *VD);
bool VisitUnaryPreIncDec(const UnaryOperator *UO);
+ bool VisitCallExpr(const CallExpr *E);
bool VisitDeclRefExpr(const DeclRefExpr *E);
bool VisitPredefinedExpr(const PredefinedExpr *E) { return Success(E); }
bool VisitMaterializeTemporaryExpr(const MaterializeTemporaryExpr *E);
@@ -8292,6 +8293,19 @@
return Success(*V, E);
}
+bool LValueExprEvaluator::VisitCallExpr(const CallExpr *E) {
+ switch (unsigned BuiltinOp = E->getBuiltinCallee()) {
+ case Builtin::BImove:
+ case Builtin::BImove_if_noexcept:
+ case Builtin::BIforward:
+ if (cast<FunctionDecl>(E->getCalleeDecl())->isConstexpr())
+ return Visit(E->getArg(0));
+ break;
+ }
+
+ return ExprEvaluatorBaseTy::VisitCallExpr(E);
+}
+
bool LValueExprEvaluator::VisitMaterializeTemporaryExpr(
const MaterializeTemporaryExpr *E) {
// Walk through the expression to find the materialized temporary itself.
Index: clang/include/clang/Basic/DiagnosticSemaKinds.td
===================================================================
--- clang/include/clang/Basic/DiagnosticSemaKinds.td
+++ clang/include/clang/Basic/DiagnosticSemaKinds.td
@@ -6569,6 +6569,15 @@
"explicitly moving variable of type %0 to itself">,
InGroup<SelfMove>, DefaultIgnore;
+def err_builtin_move_forward_unsupported : Error<
+ "unsupported signature for '%select{std::move|std::forward}0'">;
+def err_use_of_unaddressable_function : Error<
+ "taking address of non-addressable standard library function">;
+// FIXME: This should also be in -Wc++23-compat once we have it.
+def warn_use_of_unaddressable_function : Warning<
+ "taking address of non-addressable standard library function">,
+ InGroup<CXX20Compat>;
+
def warn_redundant_move_on_return : Warning<
"redundant move in return statement">,
InGroup<RedundantMove>, DefaultIgnore;
Index: clang/include/clang/Basic/Builtins.h
===================================================================
--- clang/include/clang/Basic/Builtins.h
+++ clang/include/clang/Basic/Builtins.h
@@ -156,6 +156,14 @@
return strchr(getRecord(ID).Attributes, 'i') != nullptr;
}
+ /// Determines whether this builtin is a C++ standard library function
+ /// that lives in (possibly-versioned) namespace std, possibly a template
+ /// specialization, where the signature is determined by the standard library
+ /// declaration.
+ bool isInStdNamespace(unsigned ID) const {
+ return strchr(getRecord(ID).Attributes, 'z') != nullptr;
+ }
+
/// Determines whether this builtin has custom typechecking.
bool hasCustomTypechecking(unsigned ID) const {
return strchr(getRecord(ID).Attributes, 't') != nullptr;
Index: clang/include/clang/Basic/Builtins.def
===================================================================
--- clang/include/clang/Basic/Builtins.def
+++ clang/include/clang/Basic/Builtins.def
@@ -101,6 +101,8 @@
// V:N: -> requires vectors of at least N bits to be legal
// C<N,M_0,...,M_k> -> callback behavior: argument N is called with argument
// M_0, ..., M_k as payload
+// z -> this is a C++ standard library function in (possibly-versioned)
+// namespace std; implied by STDBUILTIN
// FIXME: gcc has nonnull
#if defined(BUILTIN) && !defined(LIBBUILTIN)
@@ -111,6 +113,10 @@
# define LANGBUILTIN(ID, TYPE, ATTRS, BUILTIN_LANG) BUILTIN(ID, TYPE, ATTRS)
#endif
+#if defined(BUILTIN) && !defined(STDBUILTIN)
+# define STDBUILTIN(ID, TYPE, ATTRS, HEADER) LIBBUILTIN(ID, TYPE, "z" ATTRS, HEADER, CXX_LANG)
+#endif
+
// Standard libc/libm functions:
BUILTIN(__builtin_atan2 , "ddd" , "Fne")
BUILTIN(__builtin_atan2f, "fff" , "Fne")
@@ -919,7 +925,7 @@
LANGBUILTIN(_exception_info, "v*", "n", ALL_MS_LANGUAGES)
LANGBUILTIN(__abnormal_termination, "i", "n", ALL_MS_LANGUAGES)
LANGBUILTIN(_abnormal_termination, "i", "n", ALL_MS_LANGUAGES)
-LANGBUILTIN(__GetExceptionInfo, "v*.", "ntu", ALL_MS_LANGUAGES)
+LANGBUILTIN(__GetExceptionInfo, "v*.", "zntu", ALL_MS_LANGUAGES)
LANGBUILTIN(_InterlockedAnd8, "ccD*c", "n", ALL_MS_LANGUAGES)
LANGBUILTIN(_InterlockedAnd16, "ssD*s", "n", ALL_MS_LANGUAGES)
LANGBUILTIN(_InterlockedAnd, "NiNiD*Ni", "n", ALL_MS_LANGUAGES)
@@ -1543,6 +1549,11 @@
LIBBUILTIN(_Block_object_dispose, "vvC*iC", "f", "Blocks.h", ALL_LANGUAGES)
// FIXME: Also declare NSConcreteGlobalBlock and NSConcreteStackBlock.
+// C++11
+STDBUILTIN(move, "v&v&", "ncTh", "utility")
+STDBUILTIN(move_if_noexcept, "v&v&", "ncTh", "utility")
+STDBUILTIN(forward, "v&v&", "ncTh", "utility")
+
// Annotation function
BUILTIN(__builtin_annotation, "v.", "tn")
Index: clang/docs/ReleaseNotes.rst
===================================================================
--- clang/docs/ReleaseNotes.rst
+++ clang/docs/ReleaseNotes.rst
@@ -118,6 +118,10 @@
- Improve the dump format, dump both bitwidth(if its a bitfield) and field value.
- Remove anonymous tag locations.
- Beautify dump format, add indent for nested struct and struct members.
+- Improved ``-O0`` code generation for calls to ``std::move``, ``std::forward``,
+ and ``std::move_if_noexcept``. These are now treated as compiler builtins and
+ implemented directly, rather than instantiating the definition from the
+ standard library.
New Compiler Flags
------------------
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