proguard Lambda inlining optimization

Added lambda inlining for Kotlin lambdas passed directly as an argument or stored in a variable then passed as an argument. It currently cannot inline lambdas that are passed to a method and then used as an argument to a method called from the first method. We currently do not inline from final fields, nor from lambdas returned from methods. So we just handle the most basic cases for now.

[x] Retrace
[x] Only inline lambdas based on certain rules
[x] Start to end example with multiple steps in bytecode
[x] Replace aconst_null with getstatic call to the lambda class
[x] Add enable/disable option for the lambda inlining

Aug 03 '23 09:08 TimothyGeerkensGuardsquare

Can you provide some timings for a few applications: how big the applications are and how much time this inlining pass takes?

Aug 04 '23 09:08 rubenpieters

So currently the only real world application we tested it on is the klox compiler, it contains many lambda usages so it seemed like a good test. By just inlining the more basic lambdas we are currently focusing on we were able to get a ~10% performance increase. So this is without running proguard on it so only lambda inlining. Inlining the lambdas took around 30s.

Benchmark 1: java -jar result.jar wc.lox -o Test.jar
  Time (mean ± σ):      1.831 s ±  0.107 s    [User: 6.152 s, System: 0.238 s]
  Range (min … max):    1.717 s …  2.025 s    10 runs
 
Benchmark 1: java -jar test-files/klox.jar wc.lox -o Test2.jar
  Time (mean ± σ):      2.012 s ±  0.173 s    [User: 6.715 s, System: 0.238 s]
  Range (min … max):    1.822 s …  2.345 s    10 runs

We will try do run it on some more real world applications including android apps.

Aug 04 '23 09:08 MaartenS11

Can you provide some timings for a few applications: how big the applications are and how much time this inlining pass takes?

Current performance on a few android applications :

ANOTHERpass :

Inlining pass runtime = 4078ms
Number of lambdas found = 24
APK size before proguard = 5.3MB
APK size after proguard = 3.2MB

OneList :

Inlining pass runtime = 4651ms
Number of lambdas found = 31
APK size before proguard = 5.2MB
APK size after proguard = 3.0MB

Antimine :

Inlining pass runtime = 47651ms
Number of lambdas found = 158
APK size before proguard = 10.1MB
APK size after proguard = 5.0MB

Aug 10 '23 12:08 TimothyGeerkensGuardsquare

We noticed that proguard-core and proguard both have a version of the LambdaExpressionCollector, I guess it was moved over into proguard-core at some point but never removed here? They are also in the same package which can cause Intelij to understandably get a little confused sometimes.

Aug 11 '23 12:08 MaartenS11

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