Metal Performance

[stefankarschti]

Measure and improve metal render performance.
Initial performance is about 3.5 fps on iPad 5th gen.

[stefankarschti]

Initial instrumentation shows significant time being spent in mtl::ShaderProgram::getRenderPipelineState

[stefankarschti]

After caching the pipeline state:

Benchmark completed.
Result:
| boston     | 46.0 ms | 21.7 fps |
| paris      | 69.8 ms | 14.3 fps |
| paris2     | 52.0 ms | 19.2 fps |
| alps       | 39.0 ms | 25.7 fps |
| us east    | 37.9 ms | 26.4 fps |
| greater la | 49.2 ms | 20.3 fps |
| sf         | 83.8 ms | 11.9 fps |
| oakland    | 59.0 ms | 16.9 fps |
| germany    | 53.9 ms | 18.5 fps |
Average frame time: 54.5 ms
Average FPS: 18.3