589eac6524
A `tensor.cast` consumer can be folded with its producer. This is beneficial only if the result of the tensor cast is more static than the source. This patch adds a utility function to check that this is the case, and adds a couple of canonicalizations patterns that fold an operation with `tensor.cast` conusmers. Reviewed By: gysit Differential Revision: https://reviews.llvm.org/D120950