[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, 5 insertions, 4 deletions

diff --git a/clang/lib/CodeGen/CGBuiltin.cpp b/clang/lib/CodeGen/CGBuiltin.cpp
index 084bf50e1bc..996e5e7cd80 100644
--- a/clang/lib/CodeGen/CGBuiltin.cpp
+++ b/clang/lib/CodeGen/CGBuiltin.cpp
@@ -2611,11 +2611,12 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
   case Builtin::BI__builtin_addressof:
     return RValue::get(EmitLValue(E->getArg(0)).getPointer());
   case Builtin::BI__builtin_operator_new:
-    return EmitBuiltinNewDeleteCall(FD->getType()->castAs<FunctionProtoType>(),
-                                    E->getArg(0), false);
+    return EmitBuiltinNewDeleteCall(
+        E->getCallee()->getType()->castAs<FunctionProtoType>(), E, false);
   case Builtin::BI__builtin_operator_delete:
-    return EmitBuiltinNewDeleteCall(FD->getType()->castAs<FunctionProtoType>(),
-                                    E->getArg(0), true);
+    return EmitBuiltinNewDeleteCall(
+        E->getCallee()->getType()->castAs<FunctionProtoType>(), E, true);
+
   case Builtin::BI__noop:
     // __noop always evaluates to an integer literal zero.
     return RValue::get(ConstantInt::get(IntTy, 0));