I'm a developer at Facebook on the Android team and I recently open sourced a bunch of our performance improvements to Proguard based on Proguard 4.11. These fixes are pretty straight forward, run 2.5x as fast, and in my tests they produced bit-for-bit identical output. I'd love to get these fixes upstreamed! You can find them here: https://github.com/facebook/proguard.
Thanks for the updates. The changes look simple enough; I can make similar changes in the code for ProGuard 5.0.
ProGuard is consistently reusing arrays, because it made a significant difference in performance in the past. Do you perhaps know as of which version of Java recreating the arrays has become faster?
Awesome! I'm not sure when this started being faster, but it's definitely faster in 7u45+.