Put something sane in the DWARF offset field for bitfield ObjC ivars.

This is useful because unnamed bitfields can have effects on the
offsets which are not otherwise reflected in the DWARF information.

<rdar://problem/12629719>

llvm-svn: 167503

1 files changed, 16 insertions, 6 deletions

diff --git a/clang/lib/CodeGen/CGDebugInfo.cpp b/clang/lib/CodeGen/CGDebugInfo.cpp
index 7dfaaa47080..80fa09be747 100644
--- a/clang/lib/CodeGen/CGDebugInfo.cpp
+++ b/clang/lib/CodeGen/CGDebugInfo.cpp
@@ -15,6 +15,7 @@
 #include "CodeGenFunction.h"
 #include "CodeGenModule.h"
 #include "CGBlocks.h"
+#include "CGObjCRuntime.h"
 #include "clang/AST/ASTContext.h"
 #include "clang/AST/DeclFriend.h"
 #include "clang/AST/DeclObjC.h"
@@ -1412,12 +1413,21 @@ llvm::DIType CGDebugInfo::CreateType(const ObjCInterfaceType *Ty,
       FieldAlign = CGM.getContext().getTypeAlign(FType);
     }
 
-    // We can't know the offset of our ivar in the structure if we're using
-    // the non-fragile abi and the debugger should ignore the value anyways.
-    // Call it the FieldNo+1 due to how debuggers use the information,
-    // e.g. negating the value when it needs a lookup in the dynamic table.
-    uint64_t FieldOffset = CGM.getLangOpts().ObjCRuntime.isNonFragile()
-                             ? FieldNo+1 : RL.getFieldOffset(FieldNo);
+    uint64_t FieldOffset;
+    if (CGM.getLangOpts().ObjCRuntime.isNonFragile()) {
+      // We don't know the runtime offset of an ivar if we're using the
+      // non-fragile ABI.  For bitfields, use the bit offset into the first
+      // byte of storage of the bitfield.  For other fields, use zero.
+      if (Field->isBitField()) {
+        FieldOffset = CGM.getObjCRuntime().ComputeBitfieldBitOffset(
+            CGM, ID, Field);
+        FieldOffset %= CGM.getContext().getCharWidth();
+      } else {
+        FieldOffset = 0;
+      }
+    } else {
+      FieldOffset = RL.getFieldOffset(FieldNo);
+    }
 
     unsigned Flags = 0;
     if (Field->getAccessControl() == ObjCIvarDecl::Protected)