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Treat `std::move`, `forward`, and `move_if_noexcept` as builtins. 

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.

Reviewed By: aaron.ballman

Differential Revision: https://reviews.llvm.org/D123345
This commit is contained in:
Richard Smith 2022-03-31 18:40:40 -07:00
parent 73f5d7d0d6
commit 64c045e25b
25 changed files with 456 additions and 76 deletions
Show Stats Download Patch File Download Diff File Expand all files Collapse all files

20
clang/docs/CommandGuide/clang.rst
View File

@ -252,8 +252,24 @@ Language Selection and Mode Options
.. option:: -fno-builtin
Disable special handling and optimizations of builtin functions like
:c:func:`strlen` and :c:func:`malloc`.
Disable special handling and optimizations of well-known library functions,
like :c:func:`strlen` and :c:func:`malloc`.
.. option:: -fno-builtin-<function>
Disable special handling and optimizations for the specific library function.
For example, ``-fno-builtin-strlen`` removes any special handling for the
:c:func:`strlen` library function.
.. option:: -fno-builtin-std-<function>
Disable special handling and optimizations for the specific C++ standard
library function in namespace ``std``. For example,
``-fno-builtin-std-move_if_noexcept`` removes any special handling for the
:cpp:func:`std::move_if_noexcept` library function.
For C standard library functions that the C++ standard library also provides
in namespace ``std``, use :option:`-fno-builtin-\<function\>` instead.
.. option:: -fmath-errno

5
clang/docs/ReleaseNotes.rst
View File

@ -230,7 +230,10 @@ C2x Feature Support
C++ Language Changes in Clang
-----------------------------
- ...
- 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.
C++20 Feature Support
^^^^^^^^^^^^^^^^^^^^^

17
clang/include/clang/Basic/Builtins.def
View File

@ -81,7 +81,9 @@
// builtin even if type doesn't match signature, and don't warn if we
// can't be sure the type is right
// F -> this is a libc/libm function with a '__builtin_' prefix added.
// f -> this is a libc/libm function without the '__builtin_' prefix.
// f -> this is a libc/libm function without a '__builtin_' prefix, or with
// 'z', a C++ standard library function in namespace std::. This builtin
// is disableable by '-fno-builtin-foo' / '-fno-builtin-std-foo'.
// h -> this function requires a specific header or an explicit declaration.
// i -> this is a runtime library implemented function without the
// '__builtin_' prefix. It will be implemented in compiler-rt or libgcc.
@ -101,6 +103,8 @@
// 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 +115,10 @@
# 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, "zf" ATTRS, HEADER, CXX_LANG)
#endif
// Standard libc/libm functions:
BUILTIN(__builtin_atan2 , "ddd" , "Fne")
BUILTIN(__builtin_atan2f, "fff" , "Fne")
@ -919,7 +927,7 @@ LANGBUILTIN(__exception_info, "v*", "n", ALL_MS_LANGUAGES)
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 +1551,11 @@ LIBBUILTIN(_Block_object_assign, "vv*vC*iC", "f", "Blocks.h", ALL_LANGUAGES)
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")

25
clang/include/clang/Basic/Builtins.h
View File

@ -138,6 +138,10 @@ public:
/// Determines whether this builtin is a predefined libc/libm
/// function, such as "malloc", where we know the signature a
/// priori.
/// In C, such functions behave as if they are predeclared,
/// possibly with a warning on first use. In Objective-C and C++,
/// they do not, but they are recognized as builtins once we see
/// a declaration.
bool isPredefinedLibFunction(unsigned ID) const {
return strchr(getRecord(ID).Attributes, 'f') != nullptr;
}
@ -156,6 +160,23 @@ public:
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 can have its address taken with no
/// special action required.
bool isDirectlyAddressable(unsigned ID) const {
// Most standard library functions can have their addresses taken. C++
// standard library functions formally cannot in C++20 onwards, and when
// we allow it, we need to ensure we instantiate a definition.
return isPredefinedLibFunction(ID) && !isInStdNamespace(ID);
}
/// Determines whether this builtin has custom typechecking.
bool hasCustomTypechecking(unsigned ID) const {
return strchr(getRecord(ID).Attributes, 't') != nullptr;
@ -237,10 +258,6 @@ public:
private:
const Info &getRecord(unsigned ID) const;
/// Is this builtin supported according to the given language options?
bool builtinIsSupported(const Builtin::Info &BuiltinInfo,
const LangOptions &LangOpts);
/// Helper function for isPrintfLike and isScanfLike.
bool isLike(unsigned ID, unsigned &FormatIdx, bool &HasVAListArg,
const char *Fmt) const;

9
clang/include/clang/Basic/DiagnosticSemaKinds.td
View File

@ -6586,6 +6586,15 @@ def warn_self_move : Warning<
"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_cxx20_compat_use_of_unaddressable_function : Warning<
"taking address of non-addressable standard library function "
"is incompatible with C++20">, InGroup<CXX20Compat>;
def warn_redundant_move_on_return : Warning<
"redundant move in return statement">,
InGroup<RedundantMove>, DefaultIgnore;

14
clang/lib/AST/ExprConstant.cpp
View File

@ -8127,6 +8127,7 @@ public:
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 @@ bool LValueExprEvaluator::VisitVarDecl(const Expr *E, const VarDecl *VD) {
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.

45
clang/lib/Analysis/BodyFarm.cpp
View File

@ -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 @@ public:
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 @@ ImplicitCastExpr *ASTMaker::makeImplicitCast(const Expr *Arg, QualType Ty,
/* 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 @@ static CallExpr *create_call_once_lambda_call(ASTContext &C, ASTMaker M,
/*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 @@ Stmt *BodyFarm::getBody(const FunctionDecl *D) {
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;

36
clang/lib/Basic/Builtins.cpp
View File

@ -48,18 +48,22 @@ void Builtin::Context::InitializeTarget(const TargetInfo &Target,
}
bool Builtin::Context::isBuiltinFunc(llvm::StringRef FuncName) {
for (unsigned i = Builtin::NotBuiltin + 1; i != Builtin::FirstTSBuiltin; ++i)
if (FuncName.equals(BuiltinInfo[i].Name))
bool InStdNamespace = FuncName.consume_front("std-");
for (unsigned i = Builtin::NotBuiltin + 1; i != Builtin::FirstTSBuiltin;
++i) {
if (FuncName.equals(BuiltinInfo[i].Name) &&
(bool)strchr(BuiltinInfo[i].Attributes, 'z') == InStdNamespace)
return strchr(BuiltinInfo[i].Attributes, 'f') != nullptr;
}
return false;
}
bool Builtin::Context::builtinIsSupported(const Builtin::Info &BuiltinInfo,
const LangOptions &LangOpts) {
/// Is this builtin supported according to the given language options?
static bool builtinIsSupported(const Builtin::Info &BuiltinInfo,
const LangOptions &LangOpts) {
bool BuiltinsUnsupported =
(LangOpts.NoBuiltin || LangOpts.isNoBuiltinFunc(BuiltinInfo.Name)) &&
strchr(BuiltinInfo.Attributes, 'f');
LangOpts.NoBuiltin && strchr(BuiltinInfo.Attributes, 'f') != nullptr;
bool CorBuiltinsUnsupported =
!LangOpts.Coroutines && (BuiltinInfo.Langs & COR_LANG);
bool MathBuiltinsUnsupported =
@ -111,6 +115,19 @@ void Builtin::Context::initializeBuiltins(IdentifierTable &Table,
for (unsigned i = 0, e = AuxTSRecords.size(); i != e; ++i)
Table.get(AuxTSRecords[i].Name)
.setBuiltinID(i + Builtin::FirstTSBuiltin + TSRecords.size());
// Step #4: Unregister any builtins specified by -fno-builtin-foo.
for (llvm::StringRef Name : LangOpts.NoBuiltinFuncs) {
bool InStdNamespace = Name.consume_front("std-");
auto NameIt = Table.find(Name);
if (NameIt != Table.end()) {
unsigned ID = NameIt->second->getBuiltinID();
if (ID != Builtin::NotBuiltin && isPredefinedLibFunction(ID) &&
isInStdNamespace(ID) == InStdNamespace) {
Table.get(Name).setBuiltinID(Builtin::NotBuiltin);
}
}
}
}
unsigned Builtin::Context::getRequiredVectorWidth(unsigned ID) const {
@ -190,8 +207,7 @@ bool Builtin::Context::performsCallback(unsigned ID,
}
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);
}

5
clang/lib/CodeGen/CGBuiltin.cpp
View File

@ -4725,6 +4725,11 @@ RValue CodeGenFunction::EmitBuiltinExpr(const GlobalDecl GD, unsigned BuiltinID,
}
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()))

2
clang/lib/CodeGen/CGCall.cpp
View File

@ -1805,6 +1805,8 @@ void CodeGenModule::getDefaultFunctionAttributes(StringRef Name,
if (AttrOnCallSite) {
// Attributes that should go on the call site only.
// FIXME: Look for 'BuiltinAttr' on the function rather than re-checking
// the -fno-builtin-foo list.
if (!CodeGenOpts.SimplifyLibCalls || LangOpts.isNoBuiltinFunc(Name))
FuncAttrs.addAttribute(llvm::Attribute::NoBuiltin);
if (!CodeGenOpts.TrapFuncName.empty())

12
clang/lib/Sema/SemaChecking.cpp
View File

@ -2130,6 +2130,18 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
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:

61
clang/lib/Sema/SemaDecl.cpp
View File

@ -9269,6 +9269,29 @@ static Scope *getTagInjectionScope(Scope *S, const LangOptions &LangOpts) {
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,
@ -10121,28 +10144,30 @@ Sema::ActOnFunctionDeclarator(Scope *S, Declarator &D, DeclContext *DC,
// 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));
}
}

35
clang/lib/Sema/SemaExpr.cpp
View File

@ -3395,7 +3395,7 @@ ExprResult Sema::BuildDeclarationNameExpr(
case Decl::Function: {
if (unsigned BID = cast<FunctionDecl>(VD)->getBuiltinID()) {
if (!Context.BuiltinInfo.isPredefinedLibFunction(BID)) {
if (!Context.BuiltinInfo.isDirectlyAddressable(BID)) {
type = Context.BuiltinFnTy;
valueKind = VK_PRValue;
break;
@ -20528,7 +20528,8 @@ ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
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();
@ -20536,6 +20537,36 @@ ExprResult Sema::CheckPlaceholderExpr(Expr *E) {
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_cxx20_compat_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);

8
clang/lib/Sema/SemaExprCXX.cpp
View File

@ -4236,6 +4236,14 @@ Sema::PerformImplicitConversion(Expr *From, QualType ToType,
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();
}

4
clang/lib/Sema/SemaInit.cpp
View File

@ -8215,6 +8215,10 @@ ExprResult InitializationSequence::Perform(Sema &S,
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:

32
clang/lib/Sema/SemaOverload.cpp
View File

@ -1747,13 +1747,6 @@ static bool IsStandardConversion(Sema &S, Expr* From, QualType ToType,
"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 @@ Expr *Sema::FixOverloadedFunctionReference(Expr *E, DeclAccessPair Found,
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 @@ Expr *Sema::FixOverloadedFunctionReference(Expr *E, DeclAccessPair Found,
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.isDirectlyAddressable(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;
}

6
clang/lib/Sema/SemaTemplateInstantiateDecl.cpp
View File

@ -4771,6 +4771,12 @@ void Sema::InstantiateFunctionDefinition(SourceLocation PointOfInstantiation,
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,

4
clang/test/Analysis/use-after-move.cpp
View File

@ -244,7 +244,7 @@ void reinitializationTest(int i) {
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 @@ void templateArgIsNotUseTest() {
// 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
}

52
clang/test/CodeGenCXX/builtin-std-move.cpp Normal file
View File

@ -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*

6
clang/test/CodeGenCXX/microsoft-abi-throw.cpp
View File

@ -1,5 +1,4 @@
// RUN: %clang_cc1 -no-opaque-pointers -emit-llvm -o - -triple=i386-pc-win32 -std=c++11 %s -fcxx-exceptions -fms-extensions | FileCheck %s
// RUN: %clang_cc1 -no-opaque-pointers -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 @@ void h() {
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() {

20
clang/test/SemaCXX/builtin-std-move-nobuiltin.cpp Normal file
View File

@ -0,0 +1,20 @@
// RUN: %clang_cc1 -std=c++20 -verify %s -DBUILTIN=builtin
// RUN: %clang_cc1 -std=c++20 -verify %s -DBUILTIN=nobuiltin -fno-builtin
// RUN: %clang_cc1 -std=c++20 -verify %s -DBUILTIN=nobuiltin -fno-builtin-std-move -fno-builtin-std-move_if_noexcept -fno-builtin-std-forward
// RUN: %clang_cc1 -std=c++20 -verify %s -DBUILTIN=nobuiltin -ffreestanding
// expected-no-diagnostics
int nobuiltin;
namespace std {
template<typename T> constexpr T &&move(T &x) { return (T&&)nobuiltin; }
template<typename T> constexpr T &&move_if_noexcept(T &x) { return (T&&)nobuiltin; }
template<typename T> constexpr T &&forward(T &x) { return (T&&)nobuiltin; }
}
template<typename T> constexpr T *addr(T &&r) { return &r; }
int builtin;
static_assert(addr(std::move(builtin)) == &BUILTIN);
static_assert(addr(std::move_if_noexcept(builtin)) == &BUILTIN);
static_assert(addr(std::forward(builtin)) == &BUILTIN);

90
clang/test/SemaCXX/builtin-std-move.cpp Normal file
View File

@ -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}}
}

12
clang/test/SemaCXX/unqualified-std-call-fixits.cpp
View File

@ -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 @@ using namespace std;
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
}

6
clang/test/SemaCXX/unqualified-std-call.cpp
View File

@ -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 {};

6
clang/test/SemaCXX/warn-consumed-analysis.cpp
View File

@ -953,12 +953,12 @@ void test6() {
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 @@ namespace PR18260 {
void test() {
x.move();
std::move();
std::move(x);
std::move(x); // expected-warning {{ignoring return value}}
std::__1::move();
std::__1::move(x);
}