Avoid generating unused variables in the Inliner.

These variables were later being eliminated by the dead-code-elimination
pass, so you can't see them directly in the final output, but removing
them affects the name mangling off all future symbols, so it causes an
enormous ripple effect in the diff. And of course, it's a waste of time
and memory to synthesize IRNodes just to destroy them later.

If we disable control-flow analysis, we lose the dead-code-elimination
pass entirely; this change is also beneficial for emitting better code
when optimizations are turned off.

Change-Id: I882b3be4f3fd99b77d99b6abe128f26bb9252c89
Bug: skia:11319
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/375776
Commit-Queue: John Stiles <johnstiles@google.com>
Reviewed-by: Brian Osman <brianosman@google.com>
Reviewed-by: Ethan Nicholas <ethannicholas@google.com>
91 files changed