[InstCombine] Look through truncate to fold icmp with intrinsics

[InstCombine] Look through truncate to fold icmp with intrinsics

The output of intrinsic functions like ctpop, cttz, ctlz have limited range from 0 to bitwidth. So if the truncate destination type can hold the source bitwidth size, we can just ignore the truncate and use the truncate src to do combination.

Alive2 proofs:
https://alive2.llvm.org/ce/z/9D_-qP

Reviewed By: spatel

Differential Revision: https://reviews.llvm.org/D143368