Intel recently introduced a large extention to the existing x64 ISA, adding registers R16-R31, as well as three operand style instrutions for many arithematic operations, e.g.,

Relevant links:

1. https://www.intel.com/content/www/us/en/developer/articles/technical/advanced-performance-extensions-apx.html
2. https://en.wikipedia.org/wiki/X86#APX_(Advanced_Performance_Extensions)

This extension is slated for future CPUs so we are not rushing to add support for it, but we still wish to add it in at a reasonable point.

Note, that I have been working on updating xed to v2024.04.01 (https://github.com/intelxed/xed/releases/tag/v2024.04.01), which already has the support for APX. However, there are various changes needed on my end to actually add support for it, e.g., extending the register list (https://github.com/Vector35/binaryninja-api/blob/dev/arch/x86/arch_x86.cpp#L2930), etc.