Support FP16 in TVM

[gyagp]

Make sure FP16 is enabled in TVM and check its perf gain for Stable Diffusion (https://mlc.ai/web-stable-diffusion/).

[jiangzhaoming]

Chromium build for MacOS and Windows with patch that expose shader-f16 feature can be found in https://drive.google.com/drive/u/0/folders/1vAOh_JxkIitgyUPNPX8tyPgT2t4Csrj0. The build is based on Chromium code base at 14-15 March 2023.

[jiangzhaoming]

Currently "shader-f16" is exposed in Chrome Canary, behind a runtime flag.
To try using f16 on Windows (on supported devices, with DXC version >= 1.4 in path), use Chrome Canary with command

./chrome.exe --enable-dawn-features=use_dxc --disable-dawn-features=disallow_unsafe_apis

To try using f16 on Other platforms like Mac (on supported devices), start Chrome Canary with flag

--disable-dawn-features=disallow_unsafe_apis

[gyagp]

@tqchen Can you help to compare the perf of Stable Diffusion between f32 and f16 models? If you may guide us how to do this with TVM, we may also give a try.

[tqchen]

Thanks @gyagp, sorry for the delay, some of the team members are in asplos this week. Will get back as soon as we get something up and running.