Improve dead-variable elimination.
We will now consider any variable with no reads as a candidate for
elimination. This requires us to look inside expressions, but in
practice we only care about binary expressions since `a = b` is the
only way to write to a variable without also reading from it. (Even
`a *= b` is considered a read-write; that is relaxed at followup CL
http://review.skia.org/582822, further improving these results.)
Changes in various existing tests were added to counteract this
optimization; otherwise the output would have large portions missing.
Commit-Queue: Michael Ludwig <firstname.lastname@example.org>
Reviewed-by: Michael Ludwig <email@example.com>
Auto-Submit: John Stiles <firstname.lastname@example.org>
22 files changed