Add support for attribute 'trivial_abi'.

The 'trivial_abi' attribute can be applied to a C++ class, struct, or
union. It makes special functions of the annotated class (the destructor
and copy/move constructors) to be trivial for the purpose of calls and,
as a result, enables the annotated class or containing classes to be
passed or returned using the C ABI for the underlying type.

When a type that is considered trivial for the purpose of calls despite
having a non-trivial destructor (which happens only when the class type
or one of its subobjects is a 'trivial_abi' class) is passed to a
function, the callee is responsible for destroying the object.

For more background, see the discussions that took place on the mailing
list:

http://lists.llvm.org/pipermail/cfe-dev/2017-November/055955.html
http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20180101/thread.html#214043

rdar://problem/35204524

Differential Revision: https://reviews.llvm.org/D41039

llvm-svn: 324269

1 files changed, 12 insertions, 17 deletions

diff --git a/clang/lib/Sema/SemaChecking.cpp b/clang/lib/Sema/SemaChecking.cpp
index 3a6988c6026..31c1b8913b2 100644
--- a/clang/lib/Sema/SemaChecking.cpp
+++ b/clang/lib/Sema/SemaChecking.cpp
@@ -10814,23 +10814,18 @@ bool Sema::CheckParmsForFunctionDef(ArrayRef<ParmVarDecl *> Parameters,
     // information is added for it.
     diagnoseArrayStarInParamType(*this, PType, Param->getLocation());
 
-    // MSVC destroys objects passed by value in the callee.  Therefore a
-    // function definition which takes such a parameter must be able to call the
-    // object's destructor.  However, we don't perform any direct access check
-    // on the dtor.
-    if (getLangOpts().CPlusPlus && Context.getTargetInfo()
-                                       .getCXXABI()
-                                       .areArgsDestroyedLeftToRightInCallee()) {
-      if (!Param->isInvalidDecl()) {
-        if (const RecordType *RT = Param->getType()->getAs<RecordType>()) {
-          CXXRecordDecl *ClassDecl = cast<CXXRecordDecl>(RT->getDecl());
-          if (!ClassDecl->isInvalidDecl() &&
-              !ClassDecl->hasIrrelevantDestructor() &&
-              !ClassDecl->isDependentContext()) {
-            CXXDestructorDecl *Destructor = LookupDestructor(ClassDecl);
-            MarkFunctionReferenced(Param->getLocation(), Destructor);
-            DiagnoseUseOfDecl(Destructor, Param->getLocation());
-          }
+    // If the parameter is a c++ class type and it has to be destructed in the
+    // callee function, declare the destructor so that it can be called by the
+    // callee function. Do not perfom any direct access check on the dtor here.
+    if (!Param->isInvalidDecl()) {
+      if (CXXRecordDecl *ClassDecl = Param->getType()->getAsCXXRecordDecl()) {
+        if (!ClassDecl->isInvalidDecl() &&
+            !ClassDecl->hasIrrelevantDestructor() &&
+            !ClassDecl->isDependentContext() &&
+            Context.isParamDestroyedInCallee(Param->getType())) {
+          CXXDestructorDecl *Destructor = LookupDestructor(ClassDecl);
+          MarkFunctionReferenced(Param->getLocation(), Destructor);
+          DiagnoseUseOfDecl(Destructor, Param->getLocation());
         }
       }
     }