Deleting Instructions after Intrinsic Creation

Hi,
I tried creating intrinsics which
are to be placeholders for a set of instructions which
should not be executed by the backend.

I want to retain only intrinsic,phi and terminator instructions in a basic
block.
I have taken care of the external dependencies of basic block.
How do I delete the rest of the instructions?

Thank You
Aditya

P.S: