1. A compressed memory controller, comprising: a memory interface configured to access a system memory via a system bus; and a compression indicator (CI) hint directory comprising a plurality of CI hint directory entries, each comprising a plurality of CI hints; the compressed memory controller configured to: receive a memory write request comprising write data and a physical address of a memory line in the system memory; determine a compression pattern for the write data; generate a CI for the write data based on the compression pattern; write the write data to the memory line in the system memory; write the generated CI into one or more error correcting code (ECC) bits of the memory line in the system memory; and in parallel with writing the write data to the memory line in the system memory: determine whether the physical address corresponds to a CI hint directory entry of the plurality of CI hint directory entries of the CI hint directory; and responsive to determining that the physical address corresponds to a CI hint directory entry of the plurality of CI hint directory entries of the CI hint directory, update a CI hint of the plurality of CI hints of the CI hint directory entry corresponding to the memory line based on the generated CI.