[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

3 files changed, 10 insertions, 9 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));
diff --git a/clang/lib/CodeGen/CGExprCXX.cpp b/clang/lib/CodeGen/CGExprCXX.cpp
index b874959de90..56c5e681177 100644
--- a/clang/lib/CodeGen/CGExprCXX.cpp
+++ b/clang/lib/CodeGen/CGExprCXX.cpp
@@ -1307,19 +1307,19 @@ static RValue EmitNewDeleteCall(CodeGenFunction &CGF,
 }
 
 RValue CodeGenFunction::EmitBuiltinNewDeleteCall(const FunctionProtoType *Type,
-                                                 const Expr *Arg,
+                                                 const CallExpr *TheCall,
                                                  bool IsDelete) {
   CallArgList Args;
-  const Stmt *ArgS = Arg;
-  EmitCallArgs(Args, *Type->param_type_begin(), llvm::makeArrayRef(ArgS));
+  EmitCallArgs(Args, Type->getParamTypes(), TheCall->arguments());
   // Find the allocation or deallocation function that we're calling.
   ASTContext &Ctx = getContext();
   DeclarationName Name = Ctx.DeclarationNames
       .getCXXOperatorName(IsDelete ? OO_Delete : OO_New);
+
   for (auto *Decl : Ctx.getTranslationUnitDecl()->lookup(Name))
     if (auto *FD = dyn_cast<FunctionDecl>(Decl))
       if (Ctx.hasSameType(FD->getType(), QualType(Type, 0)))
-        return EmitNewDeleteCall(*this, cast<FunctionDecl>(Decl), Type, Args);
+        return EmitNewDeleteCall(*this, FD, Type, Args);
   llvm_unreachable("predeclared global operator new/delete is missing");
 }
 
diff --git a/clang/lib/CodeGen/CodeGenFunction.h b/clang/lib/CodeGen/CodeGenFunction.h
index 709e7f4ad8d..7cdec6e72b6 100644
--- a/clang/lib/CodeGen/CodeGenFunction.h
+++ b/clang/lib/CodeGen/CodeGenFunction.h
@@ -2356,7 +2356,7 @@ public:
                       CharUnits CookieSize = CharUnits());
 
   RValue EmitBuiltinNewDeleteCall(const FunctionProtoType *Type,
-                                  const Expr *Arg, bool IsDelete);
+                                  const CallExpr *TheCallExpr, bool IsDelete);
 
   llvm::Value *EmitCXXTypeidExpr(const CXXTypeidExpr *E);
   llvm::Value *EmitDynamicCast(Address V, const CXXDynamicCastExpr *DCE);