RX460 poor hash rate and multiple compute errors, any ideas?
Hi all,

Would like to know if anyone has some ideas and could point me in the right direction of my current issues.
Kernel: 4.20 on Ubuntu 18.04 LTS
amdgpu-pro-18.20-673703-ubuntu-18.04 w/ --opencl-legacy install for RX460 2GB
XMRIG-AMD 2.8.6-Xenial x64 binary

config.json:
```
{
    "algo": "cryptonight",
    "api": {
        "port": 0,
        "access-token": null,
        "id": null,
        "worker-id": null,
        "ipv6": false,
        "restricted": true
    },
    "autosave": true,
    "background": false,
    "cache": true,
    "colors": true,
    "donate-level": 1,
    "log-file": null,
    "opencl-platform": "AMD",
    "opencl-loader": "libOpenCL.so",
    "pools": [
        {
            "url": "gulf.moneroocean.stream:10004",
            "user": "redacted",
            "pass": "redacted",
            "rig-id": null,
            "nicehash": false,
            "keepalive": false,
            "variant": -1,
            "tls": false,
            "tls-fingerprint": null
        }
    ],
    "print-time": 60,
    "retries": 5,
    "retry-pause": 5,
    "threads": [
        {
            "index": 0,
            "intensity": 400,
            "worksize": 16,
            "strided_index": 2,
            "mem_chunk": 2,
            "unroll": 4,
            "comp_mode": false,
            "affine_to_cpu": false
        },
        {
            "index": 0,
            "intensity": 400,
            "worksize": 8,
            "strided_index": 2,
            "mem_chunk": 2,
            "unroll": 4,
            "comp_mode": false,
            "affine_to_cpu": false
        }
    ],
    "user-agent": null,
    "syslog": false,
    "watch": false
}
```

I was CPU mining but decided to stop to get better CPU performance for my actual workloads.

Screenshot:
![screenshot from 2018-12-26 11-26-19](https://user-images.githubusercontent.com/7962579/50452919-ab4c4e00-0902-11e9-9b42-542645311588.png)

Thank you to anyone taking the time to help me out with this, I'd really like to know what I'm doing wrong or if it's a driver bug.