Assert if deleting BasicBlock before removing it from Function.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@12983 91177308-0d34-0410-b5e6-96231b3b80d8

lib/VMCore/BasicBlock.cpp

@@ -81,6 +81,7 @@ BasicBlock::BasicBlock(const std::string &Name, Function *Parent,
 
 
 BasicBlock::~BasicBlock() {
+  assert(Parent == 0 && "BasicBlock still linked into the program!");
   dropAllReferences();
   InstList.clear();
 }