[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

1 files changed, 8 insertions, 14 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index a575def..9c0a16c 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -1097,20 +1097,14 @@ Sema::CheckBuiltinFunctionCall(FunctionDecl *FDecl, unsigned BuiltinID,
       return ExprError();
     break;
   case Builtin::BI__builtin_operator_new:
-  case Builtin::BI__builtin_operator_delete:
-    if (!getLangOpts().CPlusPlus) {
-      Diag(TheCall->getExprLoc(), diag::err_builtin_requires_language)
-        << (BuiltinID == Builtin::BI__builtin_operator_new
-                ? "__builtin_operator_new"
-                : "__builtin_operator_delete")
-        << "C++";
-      return ExprError();
-    }
-    // CodeGen assumes it can find the global new and delete to call,
-    // so ensure that they are declared.
-    DeclareGlobalNewDelete();
-    break;
-
+  case Builtin::BI__builtin_operator_delete: {
+    bool IsDelete = BuiltinID == Builtin::BI__builtin_operator_delete;
+    ExprResult Res =
+        SemaBuiltinOperatorNewDeleteOverloaded(TheCallResult, IsDelete);
+    if (Res.isInvalid())
+      CorrectDelayedTyposInExpr(TheCallResult.get());
+    return Res;
+  }
   // check secure string manipulation functions where overflows
   // are detectable at compile time
   case Builtin::BI__builtin___memcpy_chk: