[HashRecognize] Rewrite arePHIsIntertwined (#144878)
The test crc8.le.tc16 is a valid CRC algorithm, but isn't recognized as
such due to a buggy arePHIsIntertwined, which is asymmetric in its
PHINode arguments. There is also a fundamental correctness issue: the
core functionality is to match a XOR that's a recurrence in both PHI
nodes, ignoring casts, but the user of the XOR is never checked. Rewrite
and rename the function.
crc8.le.tc16 is still not recognized as a valid CRC algorithm, due to an
incorrect check for loop iterations exceeding the bitwidth of the
result: in reality, it should not exceed the bitwidth of LHSAux, but we
leave this fix to a follow-up.
Co-authored-by: Piotr Fusik <p.fusik@samsung.com>
