message: Add SPIR-V mapping for vertex/instance index builtins
diff: @@ -3665,10 +3665,9 @@ ShaderBuiltin BuiltInToSystemAttribute(ShaderStage stage, const spv::BuiltIn el)
  case spv::BuiltInSampleId: return ShaderBuiltin::MSAASampleIndex;
  case spv::BuiltInSamplePosition: return ShaderBuiltin::MSAASamplePosition;
  case spv::BuiltInSampleMask: return ShaderBuiltin::MSAACoverage;
  - case spv::BuiltInFragDepth:
  - return ShaderBuiltin::DepthOutput;
  - // case spv::BuiltInVertexIndex: return ShaderBuiltin::Vertex0Index;
  - // case spv::BuiltInInstanceIndex: return ShaderBuiltin::Instance0Index;
  + case spv::BuiltInFragDepth: return ShaderBuiltin::DepthOutput;
  + case spv::BuiltInVertexIndex: return ShaderBuiltin::VertexIndex;
  + case spv::BuiltInInstanceIndex: return ShaderBuiltin::InstanceIndex;
  default: break;
  }
  