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>



git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@167503 91177308-0d34-0410-b5e6-96231b3b80d8

Author: eefriedman

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)

lib/CodeGen/CGObjCRuntime.cpp

@@ -78,6 +78,13 @@ uint64_t CGObjCRuntime::ComputeIvarBaseOffset(CodeGen::CodeGenModule &CGM,
     CGM.getContext().getCharWidth();
 }
 
+unsigned CGObjCRuntime::ComputeBitfieldBitOffset(
+    CodeGen::CodeGenModule &CGM,
+    const ObjCInterfaceDecl *ID,
+    const ObjCIvarDecl *Ivar) {
+  return LookupFieldBitOffset(CGM, ID, ID->getImplementation(), Ivar);
+}
+
 LValue CGObjCRuntime::EmitValueForIvarAtOffset(CodeGen::CodeGenFunction &CGF,
                                                const ObjCInterfaceDecl *OID,
                                                llvm::Value *BaseValue,

lib/CodeGen/CGObjCRuntime.h

@@ -277,6 +277,12 @@ class CGObjCRuntime {
   MessageSendInfo getMessageSendInfo(const ObjCMethodDecl *method,
                                      QualType resultType,
                                      CallArgList &callArgs);
+
+  // FIXME: This probably shouldn't be here, but the code to compute
+  // it is here.
+  unsigned ComputeBitfieldBitOffset(CodeGen::CodeGenModule &CGM,
+                                    const ObjCInterfaceDecl *ID,
+                                    const ObjCIvarDecl *Ivar);
 };
 
 /// Creates an instance of an Objective-C runtime class.

test/CodeGenObjC/debug-info-ivars.m

@@ -0,0 +1,24 @@
+// RUN: %clang_cc1 -triple x86_64-apple-darwin10 -emit-llvm -g %s -o - | FileCheck %s
+
+__attribute((objc_root_class)) @interface NSObject {
+	id isa;
+}
+@end
+
+@interface BaseClass : NSObject
+{
+    int i;
+    unsigned flag_1 : 9;
+    unsigned flag_2 : 9;
+		unsigned : 1;
+		unsigned flag_3 : 9;
+}
+@end
+
+@implementation BaseClass
+@end
+
+// CHECK: metadata !{i32 786445, metadata !{{[0-9]*}}, metadata !"i", metadata !{{[0-9]*}}, i32 10, i64 32, i64 32, i64 0, i32 2, metadata !{{[0-9]*}}, null} ; [ DW_TAG_member ] [i] [line 10, size 32, align 32, offset 0] [protected] [from int]
+// CHECK: metadata !{i32 786445, metadata !{{[0-9]*}}, metadata !"flag_1", metadata !{{[0-9]*}}, i32 11, i64 9, i64 32, i64 0, i32 2, metadata !{{[0-9]*}}, null} ; [ DW_TAG_member ] [flag_1] [line 11, size 9, align 32, offset 0] [protected] [from unsigned int]
+// CHECK: metadata !{i32 786445, metadata !{{[0-9]*}}, metadata !"flag_2", metadata !{{[0-9]*}}, i32 12, i64 9, i64 32, i64 1, i32 2, metadata !{{[0-9]*}}, null} ; [ DW_TAG_member ] [flag_2] [line 12, size 9, align 32, offset 1] [protected] [from unsigned int]
+// CHECK: metadata !{i32 786445, metadata !{{[0-9]*}}, metadata !"flag_3", metadata !{{[0-9]*}}, i32 14, i64 9, i64 32, i64 3, i32 2, metadata !{{[0-9]*}}, null} ; [ DW_TAG_member ] [flag_3] [line 14, size 9, align 32, offset 3] [protected] [from unsigned int]