New Vulkan validation error related to the depth fixes

[hrydgard]

With the latest SDK, we get the below message when running in debug. This could well be a bug in the old version of glslang we're using to compile our shaders... and might explain the driver issue. We should check the SPIR-V output...

ERROR: [Validation] Code 5 : Object: VK_NULL_HANDLE (Type = 0) | SPIR-V module not valid: Vulkan spec requires DepthReplacing execution mode to be declared when using BuiltIn FragDepth. ID <0> (OpStore) is referencing ID <8> (OpVariable) which is decorated with BuiltIn FragDepth in function <4>.

[hrydgard]

Seems it was added here:

KhronosGroup/glslang@c034c5a

Alright, time to bite the bullet and upgrade glslang. I'll do it soon.

[unknownbrackets]

Oh, bah. I guess I'll need to double check that the workaround still works afterward too.

Edit: just a note, this would probably not explain the driver issue, unless there's also an execution mode for whether it uses OpKill. The driver bug was that it ignored OpKill unless the shader wrote to depth.

-[Unknown]

[hrydgard]

Oh, right. Hm. Well, maybe if the DepthReplacing mode was specified correctly the driver would have taken a different path? Anyway, we can experiment after upgrading glslang.