If llvm.dbg.region.end is disappearing then remove corresponding llvm.dbg.func.start also.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@64278 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Transforms/Utils/SimplifyCFG.cpp

@@ -1806,7 +1806,7 @@ bool llvm::SimplifyCFG(BasicBlock *BB) {
         // If we eliminated all predecessors of the block, delete the block now.
         if (pred_begin(BB) == pred_end(BB))
           // We know there are no successors, so just nuke the block.
-          M->getBasicBlockList().erase(BB);
+          DeleteDeadBlock(BB);
 
         return true;
       }