[Builtins] Overload __builtin_operator_new/delete to allow forwarding to usual allocation/deallocation functions.
Summary:
Libc++'s default allocator uses `__builtin_operator_new` and `__builtin_operator_delete` in order to allow the calls to new/delete to be ellided. However, libc++ now needs to support over-aligned types in the default allocator. In order to support this without disabling the existing optimization Clang needs to support calling the aligned new overloads from the builtins.
See llvm.org/PR22634 for more information about the libc++ bug.
This patch changes `__builtin_operator_new`/`__builtin_operator_delete` to call any usual `operator new`/`operator delete` function. It does this by performing overload resolution with the arguments passed to the builtin to determine which allocation function to call. If the selected function is not a usual allocation function a diagnostic is issued.
One open issue is if the `align_val_t` overloads should be considered "usual" when `LangOpts::AlignedAllocation` is disabled.
In order to allow libc++ to detect this new behavior the value for `__has_builtin(__builtin_operator_new)` has been updated to `201802`.
Reviewers: rsmith, majnemer, aaron.ballman, erik.pilkington, bogner, ahatanak
Reviewed By: rsmith
Subscribers: cfe-commits
Differential Revision: https://reviews.llvm.org/D43047
llvm-svn: 328134
diff --git a/clang/lib/Sema/SemaExprCXX.cpp b/clang/lib/Sema/SemaExprCXX.cpp
index a3cb462..5870c8b 100644
--- a/clang/lib/Sema/SemaExprCXX.cpp
+++ b/clang/lib/Sema/SemaExprCXX.cpp
@@ -1443,7 +1443,7 @@
CUDAPref = S.IdentifyCUDAPreference(Caller, FD);
}
- operator bool() const { return FD; }
+ explicit operator bool() const { return FD; }
bool isBetterThan(const UsualDeallocFnInfo &Other, bool WantSize,
bool WantAlign) const {
@@ -2271,7 +2271,6 @@
llvm_unreachable("Unreachable, bad result from BestViableFunction");
}
-
/// FindAllocationFunctions - Finds the overloads of operator new and delete
/// that are appropriate for the allocation.
bool Sema::FindAllocationFunctions(SourceLocation StartLoc, SourceRange Range,
@@ -3343,6 +3342,128 @@
return Result;
}
+static bool resolveBuiltinNewDeleteOverload(Sema &S, CallExpr *TheCall,
+ bool IsDelete,
+ FunctionDecl *&Operator) {
+
+ DeclarationName NewName = S.Context.DeclarationNames.getCXXOperatorName(
+ IsDelete ? OO_Delete : OO_New);
+
+ LookupResult R(S, NewName, TheCall->getLocStart(), Sema::LookupOrdinaryName);
+ S.LookupQualifiedName(R, S.Context.getTranslationUnitDecl());
+ assert(!R.empty() && "implicitly declared allocation functions not found");
+ assert(!R.isAmbiguous() && "global allocation functions are ambiguous");
+
+ // We do our own custom access checks below.
+ R.suppressDiagnostics();
+
+ SmallVector<Expr *, 8> Args(TheCall->arg_begin(), TheCall->arg_end());
+ OverloadCandidateSet Candidates(R.getNameLoc(),
+ OverloadCandidateSet::CSK_Normal);
+ for (LookupResult::iterator FnOvl = R.begin(), FnOvlEnd = R.end();
+ FnOvl != FnOvlEnd; ++FnOvl) {
+ // Even member operator new/delete are implicitly treated as
+ // static, so don't use AddMemberCandidate.
+ NamedDecl *D = (*FnOvl)->getUnderlyingDecl();
+
+ if (FunctionTemplateDecl *FnTemplate = dyn_cast<FunctionTemplateDecl>(D)) {
+ S.AddTemplateOverloadCandidate(FnTemplate, FnOvl.getPair(),
+ /*ExplicitTemplateArgs=*/nullptr, Args,
+ Candidates,
+ /*SuppressUserConversions=*/false);
+ continue;
+ }
+
+ FunctionDecl *Fn = cast<FunctionDecl>(D);
+ S.AddOverloadCandidate(Fn, FnOvl.getPair(), Args, Candidates,
+ /*SuppressUserConversions=*/false);
+ }
+
+ SourceRange Range = TheCall->getSourceRange();
+
+ // Do the resolution.
+ OverloadCandidateSet::iterator Best;
+ switch (Candidates.BestViableFunction(S, R.getNameLoc(), Best)) {
+ case OR_Success: {
+ // Got one!
+ FunctionDecl *FnDecl = Best->Function;
+ assert(R.getNamingClass() == nullptr &&
+ "class members should not be considered");
+
+ if (!FnDecl->isReplaceableGlobalAllocationFunction()) {
+ S.Diag(R.getNameLoc(), diag::err_builtin_operator_new_delete_not_usual)
+ << (IsDelete ? 1 : 0) << Range;
+ S.Diag(FnDecl->getLocation(), diag::note_non_usual_function_declared_here)
+ << R.getLookupName() << FnDecl->getSourceRange();
+ return true;
+ }
+
+ Operator = FnDecl;
+ return false;
+ }
+
+ case OR_No_Viable_Function:
+ S.Diag(R.getNameLoc(), diag::err_ovl_no_viable_function_in_call)
+ << R.getLookupName() << Range;
+ Candidates.NoteCandidates(S, OCD_AllCandidates, Args);
+ return true;
+
+ case OR_Ambiguous:
+ S.Diag(R.getNameLoc(), diag::err_ovl_ambiguous_call)
+ << R.getLookupName() << Range;
+ Candidates.NoteCandidates(S, OCD_ViableCandidates, Args);
+ return true;
+
+ case OR_Deleted: {
+ S.Diag(R.getNameLoc(), diag::err_ovl_deleted_call)
+ << Best->Function->isDeleted() << R.getLookupName()
+ << S.getDeletedOrUnavailableSuffix(Best->Function) << Range;
+ Candidates.NoteCandidates(S, OCD_AllCandidates, Args);
+ return true;
+ }
+ }
+ llvm_unreachable("Unreachable, bad result from BestViableFunction");
+}
+
+ExprResult
+Sema::SemaBuiltinOperatorNewDeleteOverloaded(ExprResult TheCallResult,
+ bool IsDelete) {
+ CallExpr *TheCall = cast<CallExpr>(TheCallResult.get());
+ if (!getLangOpts().CPlusPlus) {
+ Diag(TheCall->getExprLoc(), diag::err_builtin_requires_language)
+ << (IsDelete ? "__builtin_operator_delete" : "__builtin_operator_new")
+ << "C++";
+ return ExprError();
+ }
+ // CodeGen assumes it can find the global new and delete to call,
+ // so ensure that they are declared.
+ DeclareGlobalNewDelete();
+
+ FunctionDecl *OperatorNewOrDelete = nullptr;
+ if (resolveBuiltinNewDeleteOverload(*this, TheCall, IsDelete,
+ OperatorNewOrDelete))
+ return ExprError();
+ assert(OperatorNewOrDelete && "should be found");
+
+ TheCall->setType(OperatorNewOrDelete->getReturnType());
+ for (unsigned i = 0; i != TheCall->getNumArgs(); ++i) {
+ QualType ParamTy = OperatorNewOrDelete->getParamDecl(i)->getType();
+ InitializedEntity Entity =
+ InitializedEntity::InitializeParameter(Context, ParamTy, false);
+ ExprResult Arg = PerformCopyInitialization(
+ Entity, TheCall->getArg(i)->getLocStart(), TheCall->getArg(i));
+ if (Arg.isInvalid())
+ return ExprError();
+ TheCall->setArg(i, Arg.get());
+ }
+ auto Callee = dyn_cast<ImplicitCastExpr>(TheCall->getCallee());
+ assert(Callee && Callee->getCastKind() == CK_BuiltinFnToFnPtr &&
+ "Callee expected to be implicit cast to a builtin function pointer");
+ Callee->setType(OperatorNewOrDelete->getType());
+
+ return TheCallResult;
+}
+
void Sema::CheckVirtualDtorCall(CXXDestructorDecl *dtor, SourceLocation Loc,
bool IsDelete, bool CallCanBeVirtual,
bool WarnOnNonAbstractTypes,