vcc glsl backend upgrades

[JuanDiegoMontoya]

• Fix spacing when emitting uniform constants.
• Remove initializers for more address spaces where they're illegal.
• Emit layout(binding = n) for storage and uniform blocks with descriptor binding annotation.
• Emit layout(location = n) for uniform constants, input variables, and output variables with location annotation.
• Detect feature usage and emit the appropriate #version directive (e.g. using an SSBO will require at least version 430).
• UBO support
  • Fixed-length array of native types
  • Fixed-length array of user-defined type (use extern to declare these)
• SSBO support
  • Fixed-length array of native type
  • Fixed-length array of user-defined type
  • SSBO with only a flexible array member
  • SSBO with one or more fixed-size members and one flexible array member
    • I don't know how this should look, syntactically. Maybe a struct with a flexible array member at the end? That syntax is legal in C and would closely match existing GLSL syntax. Otherwise, maybe a struct with a pointer member at the end. This could also just be dropped.

Expanded support for samplers and images are left for a future PR.

[JuanDiegoMontoya]

Can we get this downgraded to a draft PR? I don't have permission to change it.

[Hugobros3]

Could I interest you in picking this back up, perhaps adding some extra testing infrastructure so that we can guard against future regression ?

[JuanDiegoMontoya]

I'll see if I can take a look at re-syncing with main later this week.