Implement findMSB intrinsic in Metal.
findMSB has one special trick that Metal doesn't naturally have an
equivalent for, specifically in its treatment of negative numbers.
findMSB searches negative numbers for a zero bit, not a one bit!
We emulate this behavior in Metal using select(n, ~n, n<0).
Change-Id: I861c6b8fb3dc5427643cd8c68a39a53f1959bff3
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/343996
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
3 files changed