kmeakin (Apr 12 2023 at 17:34): kmeakin (Apr 12 2023 at 17:34):What are the semantics of bitselect on vectors?
kmeakin (Apr 12 2023 at 17:36):Will an instruction like bitselect 0b10 x y result in a vector where the first lane is the first lane of x and the second lane is the second lane of y?
kmeakin (Apr 12 2023 at 17:38):Or is the bitmask applied to each lane separately? ie the first lane would be bitselect(0b10 x[0] y[0]) and the second lane would be bitselect(0b10 x[1] y[1])?
kmeakin (Apr 12 2023 at 17:38):What about when the bitmask is itself a vector?
Jamey Sharp (Apr 12 2023 at 17:44):The documentation for bitselect says "For each bit in c, this instruction selects the corresponding bit from x if the bit in x is 1 and the corresponding bit from y if the bit in c is 0." I believe that applies the same to vectors as scalars, so this instruction doesn't care about lane boundaries: each bit in each lane is used to determine which input to use for the corresponding bit of the result.
Notification Bot (Apr 12 2023 at 19:07):kmeakin has marked this topic as resolved.
Last updated: Jan 09 2026 at 13:15 UTC