Add __builtin_operator_new and __builtin_operator_delete, which act like calls

to the normal non-placement ::operator new and ::operator delete, but allow
optimizations like new-expressions and delete-expressions do.

llvm-svn: 210137

clang/docs/LanguageExtensions.rst

@@ -1446,6 +1446,24 @@ object that overloads ``operator&``.
     return __builtin_addressof(value);
   }
 
+``__builtin_operator_new`` and ``__builtin_operator_delete``
+------------------------------------------------------------
+
+``__builtin_operator_new`` allocates memory just like a non-placement non-class
+*new-expression*. This is exactly like directly calling the normal
+non-placement ``::operator new``, except that it allows certain optimizations
+that the C++ standard does not permit for a direct function call to
+``::operator new`` (in particular, removing ``new`` / ``delete`` pairs and
+merging allocations).
+
+Likewise, ``__builtin_operator_delete`` deallocates memory just like a
+non-class *delete-expression*, and is exactly like directly calling the normal
+``::operator delete``, except that it permits optimizations. Only the unsized
+form of ``__builtin_operator_delete`` is currently available.
+
+These builtins are intended for use in the implementation of ``std::allocator``
+and other similar allocation libraries, and are only available in C++.
+
 Multiprecision Arithmetic Builtins
 ----------------------------------
 

clang/include/clang/Basic/Builtins.def

@@ -73,7 +73,7 @@
 //       be followed by ':headername:' to state which header this function
 //       comes from.
 //  i -> this is a runtime library implemented function without the
-//       '__builtin_' prefix. It will be implemented in compiter-rt or libgcc.
+//       '__builtin_' prefix. It will be implemented in compiler-rt or libgcc.
 //  p:N: -> this is a printf-like function whose Nth argument is the format
 //          string.
 //  P:N: -> similar to the p:N: attribute, but the function is like vprintf
@@ -1204,6 +1204,8 @@ BUILTIN(__builtin_smulll_overflow, "bSLLiCSLLiCSLLi*", "n")
 
 // Clang builtins (not available in GCC).
 BUILTIN(__builtin_addressof, "v*v&", "nct")
+BUILTIN(__builtin_operator_new, "v*z", "c")
+BUILTIN(__builtin_operator_delete, "vv*", "n")
 
 #undef BUILTIN
 #undef LIBBUILTIN

clang/include/clang/Basic/DiagnosticSemaKinds.td

@@ -6682,6 +6682,7 @@ def err_argument_invalid_range : Error<
 
 def err_builtin_longjmp_invalid_val : Error<
   "argument to __builtin_longjmp must be a constant 1">;
+def err_builtin_requires_language : Error<"'%0' is only available in %1">;
 
 def err_constant_integer_arg_type : Error<
   "argument to %0 must be a constant integer">;

clang/lib/CodeGen/CGBuiltin.cpp

@@ -1508,6 +1508,12 @@ RValue CodeGenFunction::EmitBuiltinExpr(const FunctionDecl *FD,
   }
   case Builtin::BI__builtin_addressof:
     return RValue::get(EmitLValue(E->getArg(0)).getAddress());
+  case Builtin::BI__builtin_operator_new:
+    return EmitBuiltinNewDeleteCall(FD->getType()->castAs<FunctionProtoType>(),
+                                    E->getArg(0), false);
+  case Builtin::BI__builtin_operator_delete:
+    return EmitBuiltinNewDeleteCall(FD->getType()->castAs<FunctionProtoType>(),
+                                    E->getArg(0), true);
   case Builtin::BI__noop:
     return RValue::get(nullptr);
   case Builtin::BI_InterlockedCompareExchange: {

clang/lib/CodeGen/CGExprCXX.cpp

@@ -1029,6 +1029,23 @@ static RValue EmitNewDeleteCall(CodeGenFunction &CGF,
   return RV;
 }
 
+RValue CodeGenFunction::EmitBuiltinNewDeleteCall(const FunctionProtoType *Type,
+                                                 const Expr *Arg,
+                                                 bool IsDelete) {
+  CallArgList Args;
+  const Stmt *ArgS = Arg;
+  EmitCallArgs(Args, *Type->param_type_begin(),
+               ConstExprIterator(&ArgS), ConstExprIterator(&ArgS + 1));
+  // 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 (Ctx.hasSameType(cast<FunctionDecl>(Decl)->getType(), QualType(Type, 0)))
+      return EmitNewDeleteCall(*this, cast<FunctionDecl>(Decl), Type, Args);
+  llvm_unreachable("predeclared global operator new/delete is missing");
+}
+
 namespace {
   /// A cleanup to call the given 'operator delete' function upon
   /// abnormal exit from a new expression.

clang/lib/CodeGen/CodeGenFunction.h

@@ -1659,6 +1659,9 @@ public:
   void EmitDeleteCall(const FunctionDecl *DeleteFD, llvm::Value *Ptr,
                       QualType DeleteTy);
 
+  RValue EmitBuiltinNewDeleteCall(const FunctionProtoType *Type,
+                                  const Expr *Arg, bool IsDelete);
+
   llvm::Value* EmitCXXTypeidExpr(const CXXTypeidExpr *E);
   llvm::Value *EmitDynamicCast(llvm::Value *V, const CXXDynamicCastExpr *DCE);
   llvm::Value* EmitCXXUuidofExpr(const CXXUuidofExpr *E);
@@ -2641,7 +2644,8 @@ public:
 
   void EmitCallArgs(CallArgList &Args, ArrayRef<QualType> ArgTypes,
                     CallExpr::const_arg_iterator ArgBeg,
-                    CallExpr::const_arg_iterator ArgEnd, bool ForceColumnInfo);
+                    CallExpr::const_arg_iterator ArgEnd,
+                    bool ForceColumnInfo = false);
 
 private:
   const TargetCodeGenInfo &getTargetHooks() const {

clang/lib/Sema/SemaChecking.cpp

@@ -296,8 +296,22 @@ Sema::CheckBuiltinFunctionCall(unsigned BuiltinID, CallExpr *TheCall) {
     if (SemaBuiltinAddressof(*this, TheCall))
       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;
   }
-  
+
   // Since the target specific builtins for each arch overlap, only check those
   // of the arch we are compiling for.
   if (BuiltinID >= Builtin::FirstTSBuiltin) {

clang/test/CodeGenCXX/new.cpp

@@ -326,6 +326,15 @@ namespace N3664 {
   }
 }
 
+namespace builtins {
+  // CHECK-LABEL: define void @_ZN8builtins1fEv
+  void f() {
+    // CHECK: call noalias i8* @_Znwm(i64 4) [[ATTR_BUILTIN_NEW]]
+    // CHECK: call void @_ZdlPv({{.*}}) [[ATTR_BUILTIN_DELETE]]
+    __builtin_operator_delete(__builtin_operator_new(4));
+  }
+}
+
 // CHECK-DAG: attributes [[ATTR_NOBUILTIN]] = {{[{].*}} nobuiltin {{.*[}]}}
 // CHECK-DAG: attributes [[ATTR_NOBUILTIN_NOUNWIND]] = {{[{].*}} nobuiltin nounwind {{.*[}]}}
 

clang/test/Sema/builtins.c

@@ -197,3 +197,8 @@ void no_ms_builtins() {
   __noop(1); // expected-warning {{implicit declaration}}
   __debugbreak(); // expected-warning {{implicit declaration}}
 }
+
+void unavailable() {
+  __builtin_operator_new(0); // expected-error {{'__builtin_operator_new' is only available in C++}}
+  __builtin_operator_delete(0); // expected-error {{'__builtin_operator_delete' is only available in C++}}
+}