Some refactoring of Ivar offset code gen.
in preparation for nonfragile ivar offset work.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@64225 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/CGObjCGNU.cpp b/lib/CodeGen/CGObjCGNU.cpp
index 8cee0f0..b41f76d 100644
--- a/lib/CodeGen/CGObjCGNU.cpp
+++ b/lib/CodeGen/CGObjCGNU.cpp
@@ -146,6 +146,9 @@
                                       const ObjCIvarDecl *Ivar,
                                       const FieldDecl *Field,
                                       unsigned CVRQualifiers);
+  virtual llvm::Value *EmitIvarOffset(CodeGen::CodeGenFunction &CGF,
+                                      ObjCInterfaceDecl *Interface,
+                                      const ObjCIvarDecl *Ivar);
 };
 } // end anonymous namespace
 
@@ -1035,6 +1038,23 @@
   return LV;
 }
 
+llvm::Value *CGObjCGNU::EmitIvarOffset(CodeGen::CodeGenFunction &CGF,
+                         ObjCInterfaceDecl *Interface,
+                         const ObjCIvarDecl *Ivar) {
+  const llvm::Type *InterfaceLTy =
+    CGM.getTypes().ConvertType(
+                            CGM.getContext().getObjCInterfaceType(Interface));
+  const llvm::StructLayout *Layout =
+    CGM.getTargetData().getStructLayout(cast<llvm::StructType>(InterfaceLTy));
+  FieldDecl *Field = Interface->lookupFieldDeclForIvar(CGM.getContext(), Ivar);
+  uint64_t Offset =
+    Layout->getElementOffset(CGM.getTypes().getLLVMFieldNo(Field));
+  
+  return llvm::ConstantInt::get(
+                            CGM.getTypes().ConvertType(CGM.getContext().LongTy),
+                            Offset);
+}
+
 CodeGen::CGObjCRuntime *CodeGen::CreateGNUObjCRuntime(CodeGen::CodeGenModule &CGM){
   return new CGObjCGNU(CGM);
 }