llvm dev - Oct 2016 - How does one reduce a function CFG to its entry block?

Hello,
 I wish to reduce a function CFG to its entry block. I wrote the following code
using lib/IR/Function.cpp/Function::dropAllReferences() (from llvm-3.6) as
reference:

 Function *F; // Suitably initialized. BasicBlock *FEntryBlock =
&F->getEntryBlock(); FEntryBlock->getTerminator()->eraseFromParent(); FEntryBlock->removeFromParent(); for
(Function::iterator I = F->begin(), E = F->end(); I != E; ++I)   
I->dropAllReferences(); while (!F->getBasicBlockList().empty())  
F->getBasicBlockList().begin()->eraseFromParent(); FEntryBlock->insertInto(F); //
...subsequent provision of a terminator, etc.
  
 This does have the desired effect, but since I have no prior experience
modifying LLVM, I am not sure if this is safe/legitimate or if my approach is
flawed.
 [ I am also able to achieve this by  substituting the original terminator to
the entry block by a:   br i1 true, label %__RELEVANT,
%__DISCARD_REST_OF_OLD_BODY
   and have the code-gen prepare step eliminate the (made) unreachable rest of
the old body   so that only the original entry block with an unconditional
branch to other relevant code that   I add, remains; as intended. However, I
want to not rely on the change happening further   downstream; I'd prefer
that the intended transformation be self-contained. ]

  Kindly comment.

Thank you,Anmol P. Paralkar
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