I think unifying the assembly language would be quite difficult given the large churn in the underlying hardware architectures as the GPUs evolve. DirectX is mostly fine, and it has served well to allow games to continue to operate even when they were developed against much older versions of the API.
Perhaps more work can be done driver side. For example, allow developers to hint at the formats of data used so the driver doesn't always have to check degenerate conditions, like textures of a certain size or mismatches in vertex shader outputs and pixel shader inputs. Maybe the old capabilities model of DX9 would allow the option of a faster path.
Perhaps more work can be done driver side. For example, allow developers to hint at the formats of data used so the driver doesn't always have to check degenerate conditions, like textures of a certain size or mismatches in vertex shader outputs and pixel shader inputs. Maybe the old capabilities model of DX9 would allow the option of a faster path.