RADV Lands VK_PIPELINE_CREATE_DISABLE_OPTIMIZATION_BIT

The RADV Vulkan driver within Mesa has landed its VK_PIPELINE_CREATE_DISABLE_OPTIMIZATION_BIT support so applications/games can opt to disable optimizations when compiling a Vulkan pipeline. This is notably what was just covered the other day for helping to reduce stuttering with DXVK.

When VK_PIPELINE_CREATE_DISABLE_OPTIMIZATION_BIT is set, NIR linking optimizations are not utilized. In doing so it sped up the compilation time of some Unity demos by about 10% as a reference test done by Timothy Arceri at Valve. This is what is being used by a DXVK branch to speed up the compilation time while asynchronously triggering off an optimized build in the background and then transparently switching over to the optimized build when ready, thereby hoping to eliminate stuttering for waiting on the initial compilation. So far I haven't seen any other Vulkan applications/games request support for this bit.

This bit landed in Mesa Git for next quarter's Mesa 18.2 release.