OpenGL docs specifically insist that the sequence (comma) operator
should not be treated as a constant-expression so that attempts to
declare multidimensional arrays with a comma will fail:
http://screen/vJEpAe9yNmbzZTm
(See "12.43 Sequence operator and constant expressions" in the OpenGL
ES3 documentation or read skia:13311 for details.)
In practice, we don't get much benefit from optimizing away unused
comma-expressions; it improves some synthetic tests, but realistically
this will not help Skia in any real-world scenario. The constant folder
no longer attempts this optimization, and comma-expressions are now
rejected in a constant-expression context.
Change-Id: Ic5dea6ff90e36614b548c1ce89a444e81da944ae
Bug: skia:13311
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/539565
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Arman Uguray <armansito@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
This will hopefully improve performance on lower-end GPUs.
Change-Id: I9c2ee6dc31acd08bec0bfb5f59edc3cf90163f9e
Bug: skia:12339
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/465078
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Commit-Queue: John Stiles <johnstiles@google.com>
No-op arithmetic simplification will convert expressions like `x += 0`
to `x`. When making this simplification, we will also downgrade the ref-
kind of `x` from "write" to "read" since the new expression is no longer
an assignment.
The fuzzer discovered that the ref-kind downgrade was too aggressive,
and would also traverse into nested subexpressions and downgrade them
as well. That is, for `x[y=z] += 0` would convert both `x` and `y`
into "read" references, which is incorrect; `y` is still being written
to.
The fuzzer managed to turn this mistake into an assertion by leveraging
a separate optimization. It added a leading, side-effect-less comma
expression for us to detect as worthless and eliminate. In doing so, we
clone the expression with the busted ref-kind, triggering an assertion.
Change-Id: I42fc31f6932f679ae875e2b49db2ad2f4e89e2cb
Bug: oss-fuzz:37677
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/442536
Auto-Submit: John Stiles <johnstiles@google.com>
Commit-Queue: Brian Osman <brianosman@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
