[llvm] Question: What is the correct interpretation of LaneBitmask? (PR #109797)

[Matt Arsenault via llvm-commits]

arsenm wrote:


> Does the approach of using register units (instead of registers) have any impact on the existence or future use of the LaneBitmask?
> 

No. In an ideal world you could directly map bits 


> 
> I have some local patches that define registers/subreg-indices for the top bits, but then ran into an issue that the `uint64_t` to represent the `LaneBitmask` is no longer sufficient. 


How big are these registers? AMDGPU is sitting right at the 64-bit limit now 

https://github.com/llvm/llvm-project/pull/109797