Add Analysis::ReturnsInputAlpha.
Now we have a basic mechanism to determine whether or not a color
filter returns its alpha unchanged, without relying on SkVM.
Its results are more conservative than SkVM's, since we can't rely
on SSA form tracking values through the flow of execution, but it
is good enough that we should be able to adapt existing shaders to
conform to its rules without hurting performance (if we notice any
reduction in performance).
Change-Id: Ibe45f1e31acebc2200020664e0c05f8a4685ad98
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/665522
Commit-Queue: John Stiles <johnstiles@google.com>
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
8 files changed
