Mesa's RADV ACO Adds Support For Rapid Packed Math

Hitting the Mesa tree when Mesa 21.0 was being branched (but looks like it will still make it now part of "staging/21.0") is support for AMD's "rapid packed math" with the RADV driver's ACO compiler back-end.

Rapid Packed Math is the AMD terminology for allowing two FP16 operations within a single FP32 operation. ACO, which is the default shader compiler back-end since last year in Mesa's RADV driver, now supports this functionality for Vec2 16-bit operations.

Rapid Packed Math (vectorize_vec2_16bit) is supported since Vega and can allow for significant throughput improvements for FP16 operations albeit not too common for most games.

In any case, this merge request that had been open for the past four months was finally merged this week to Mesa Git allowing Rapid Packed Math support within the ACO compiler back-end.