Investigate if/how Qiwu can be used in HEIR

Qiwu: Exploiting Ciphertext-Level SIMD Parallelism in Homomorphic Encryption Programs

> We introduce Qiwu, a ciphertext-level vectorization approach
that enhances performance by fusing multiple ciphertexts containing bubbles.
Qiwu uses a DSL to specify zero
bubbles in input ciphertexts and nonzero bubbles in output
ciphertexts, employs data-flow analysis to track them, and
formulates a fusion plan guided by a cost-benefit assessment

https://dl.acm.org/doi/10.1145/3696443.3708917