add mad, to_f32, trunc

enough for SkVM_mad, SkVM_madder

Change-Id: Id5165e221ae9923f6ccffc6a987d973c7f11332c
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/274026
Auto-Submit: Mike Klein <mtklein@google.com>
Reviewed-by: Mike Klein <mtklein@google.com>
Commit-Queue: Mike Klein <mtklein@google.com>
1 file changed