[AggressiveInstCombine] Loosen some conditions in the popcount pattern (#197536) This PR refines and loosens some condition regarding the last AND mask in the popcount pattern introduced by #180917 . More specifically, this AND mask only needs to fulfill two conditions: 1. All ones for the lower NumLenBits-bits, where NumLenBits is the number of bits needed to represent the size of the integer 2. Zeros from bit 8 and onward Rest of the bits can have arbitrary values. The compute known bits infrastructure is supposed to reason about this but it was depth-limited in this particular case.
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