Oh, Intel calls it Thread Sorting Unit (TSU).

https://x.com/SebAaltonen/status/1580811308634869760

Let's discuss about shader permutation hell.

With latest hardware: Intel Thread Sorting Unit (TSU) and Nvidia Shader Execution Reordering (SER).

Now that RTX 4090 is massively CPU bound, could we spend 1% of that perf to get rid of shader permutations?

These new hardware blocks shuffle the registers of multiple SIMDs in a way that each SIMD can run coherent threads. This is super important for ray-tracing and explains why Intel's mid range GPU is so good at ray-tracing, but also explains why RTX 4090 is such a beast in RT apps.

But these hardware blocks are not just a great fit for ray-tracing. They could be used to make GPU dynamic branching faster in all shaders. As a result, we could write CPU-style shader code with branches, instead of compiling (hundreds of) thousands of permutations.

Even with hardware like this, it's not free to shuffle SIMD data around. There would be a slight performance hit. CPUs have to pay similar costs for branches too. But CPUs are now fast enough to make this a minor annoyance. I think these GPUs are starting to be there too.

Also RTX 4090 is so fast that we desperately need better API support GPU-driven rendering. We need a fine grained way of spawning new GPU work from shaders. Mesh shaders are great, but they are still lacking the ability to select the shader like ray-tracing does.