The IR verifier will carsh if there is any instructions located before
phi-node. The `infer-address-spaces` pass would like to insert
`addrspacecast` before phi-node in some corner cases. Indeed, since the
operand pointer(phi-node's incoming value) has been determined to
`NewAS` by the pass, it is safe to `addrspacecast` it immediately after
the position where defined it.
Co-authored-by: Kerang Mao <krmao@birentech.com>
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