[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, 4 deletions

diff --git a/clang/lib/CodeGen/CGBlocks.cpp b/clang/lib/CodeGen/CGBlocks.cpp
index 663f1d03fdc..1a6904976fb 100644
--- a/clang/lib/CodeGen/CGBlocks.cpp
+++ b/clang/lib/CodeGen/CGBlocks.cpp
@@ -1525,6 +1525,9 @@ computeCopyInfoForBlockCapture(const BlockDecl::Capture &CI, QualType T,
   case QualType::PCK_Struct:
     return std::make_pair(BlockCaptureEntityKind::NonTrivialCStruct,
                           BlockFieldFlags());
+  case QualType::PCK_ARCWeak:
+    // We need to register __weak direct captures with the runtime.
+    return std::make_pair(BlockCaptureEntityKind::ARCWeak, Flags);
   case QualType::PCK_ARCStrong:
     // We need to retain the copied value for __strong direct captures.
     // If it's a block pointer, we have to copy the block and assign that to
@@ -1542,10 +1545,6 @@ computeCopyInfoForBlockCapture(const BlockDecl::Capture &CI, QualType T,
     // Special rules for ARC captures:
     Qualifiers QS = T.getQualifiers();
 
-    // We need to register __weak direct captures with the runtime.
-    if (QS.getObjCLifetime() == Qualifiers::OCL_Weak)
-      return std::make_pair(BlockCaptureEntityKind::ARCWeak, Flags);
-
     // Non-ARC captures of retainable pointers are strong and
     // therefore require a call to _Block_object_assign.
     if (!QS.getObjCLifetime() && !LangOpts.ObjCAutoRefCount)