What's so great about R8?
Summary
This episode features Tor Norby, Romain Guy, Sean from the R8 team, Chris from DevX Performance, and Shai from Platform Performance discussing R8, Android’s whole-program optimizing compiler. They explain how R8 improves app performance by removing dead code, inlining methods, and merging interfaces, often yielding significant startup speedups and reduced ANRs. The team highlights the importance of proper keep rules to handle reflection and JNI, warning against overly broad rules that hinder optimization. They also cover recent improvements in developer experience, including better document…
Topics discussed
Introduction to R8 and D8 compilers
Why two compilers: Debug vs Release optimization
Reflection, JNI, and the need for keep rules
Tree shaking, inlining, and interface merging
Baseline profiles and ART compiler hints
DEX file locality and startup code optimization
Performance gains and ANR reduction with R8
Kotlin null checks and compiler optimizations
Debugging obfuscated stack traces
Keep rules, ProGuard migration, and JSON libraries
Testing shrinking behavior and Compose optimizations
R8 limitations for non-Android Java bytecode
Reflection annotations and conditional keep rules
Resource shrinking and platform feature flags
R8 adoption impact on app performance
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