[ObjC] Allow declaring __weak pointer fields in C structs in ARC.

This patch uses the infrastructure added in r326307 for enabling
non-trivial fields to be declared in C structs to allow __weak fields in
C structs in ARC.

This recommits r327206, which was reverted because it caused
module-enabled builders to fail. I discovered that the
CXXRecordDecl::CanPassInRegisters flag wasn't being set correctly in
some cases after I moved it to RecordDecl.

Thanks to Eric Liu for helping me investigate the bug.

rdar://problem/33599681

https://reviews.llvm.org/D44095

llvm-svn: 327870

1 files changed, 3 insertions, 5 deletions

diff --git a/clang/lib/Sema/SemaDecl.cpp b/clang/lib/Sema/SemaDecl.cpp
index ea971353039..6319e4b34ce 100644
--- a/clang/lib/Sema/SemaDecl.cpp
+++ b/clang/lib/Sema/SemaDecl.cpp
@@ -15266,7 +15266,6 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
 
     // Get the type for the field.
     const Type *FDTy = FD->getType().getTypePtr();
-    Qualifiers QS = FD->getType().getQualifiers();
 
     if (!FD->isAnonymousStructOrUnion()) {
       // Remember all fields written by the user.
@@ -15407,10 +15406,7 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
       QualType T = Context.getObjCObjectPointerType(FD->getType());
       FD->setType(T);
     } else if (getLangOpts().allowsNonTrivialObjCLifetimeQualifiers() &&
-               Record && !ObjCFieldLifetimeErrReported &&
-               ((!getLangOpts().CPlusPlus &&
-                 QS.getObjCLifetime() == Qualifiers::OCL_Weak) ||
-                Record->isUnion())) {
+               Record && !ObjCFieldLifetimeErrReported && Record->isUnion()) {
       // It's an error in ARC or Weak if a field has lifetime.
       // We don't want to report this in a system header, though,
       // so we just make the field unavailable.
@@ -15456,6 +15452,8 @@ void Sema::ActOnFields(Scope *S, SourceLocation RecLoc, Decl *EnclosingDecl,
         Record->setNonTrivialToPrimitiveCopy(true);
       if (FT.isDestructedType())
         Record->setNonTrivialToPrimitiveDestroy(true);
+      if (!FT.canPassInRegisters())
+        Record->setCanPassInRegisters(false);
     }
 
     if (Record && FD->getType().isVolatileQualified())