tree c354ee162c46fa0aef5fb7e08fc4ed7e27cf274a
parent 1f95e6c6b44f59aee99d430c2779047918ea2f94
author John Stiles <johnstiles@google.com> 1613826043 -0500
committer John Stiles <johnstiles@google.com> 1614006358 +0000

Demonstrate a bug with inlined static switches.

When we detect a static switch, the optimizer finds the matching switch-
case and eliminates all the other switch-cases. It handles case
fall-through by scanning forward and looking for an unconditional break.

However, the inliner has an interesting quirk--it can replace `return`
statements inside of a switch with `continue` statements, since the body
of the inlined function has been wrapped with a for-loop to allow for
early exits. The optimizer does not recognize these continue statements
as exits from the switch (although they certainly qualify), so it
treats continues as fallen-through and keeps emitting switch-cases.

The dead-code elimination pass was actually doing us a favor here and
eliminating the excess code later. A flag was added to disable DCE in
order to reveal the problem in a test.

Change-Id: I8ff19fde5e32d0ab73d7c5411da40cb953a446f5
Bug: skia:11352
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/372956
Auto-Submit: John Stiles <johnstiles@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>