if basic blocks are destroyed while there are *just* BlockAddress' hanging

around, then zap them.  This is analogous to dangling constantexprs hanging
off functions.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@85627 91177308-0d34-0410-b5e6-96231b3b80d8

test/Transforms/SimplifyCFG/basictest.ll

@@ -21,5 +21,10 @@ BB1:            ; preds = %0, %0
 }
 
 
-
-
+define void @test4() {
+entry:
+ br label %return
+return:
+ ret void
+}
+@test4g = global i8* blockaddress(@test4, %return)