Teach backend to emit iinc instructions
#13214
Conversation
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I'm not sure what to do about tests. The initial PR had tests, but they used |
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Thanks @smarter! I completely forgot that there are tests in the |
The backend is now able to turn `x += 42` into an `iinc 42` instruction. The optimization only applies to `+=` and `-=`, provided the the net increment fits inside a signed 16-bit value (the ASM library handles choosing `iinc` or `wide iinc` as is appropriate). Ported from scala/scala#9713
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Is that something worth doing? I guess it won't make code any faster but it gives some small improvement in bytecode size. Is that worth the additional effort of maintaining the code? What does the Scala 2.13 backend do? |
This is a port of scala/scala#9713 which was just merged |
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It's mostly a cosmetic change. It could potentially benefit performance by pushing some methods below the JVM's inlining size limits. I also see it as going with the flow of the platform, javac emits |
The backend is now able to turn
x += 42into aniinc 42instruction. The optimization only applies to
+=and-=, providedthe the net increment fits inside a signed 16-bit value (the ASM library
handles choosing
iincorwide iincas is appropriate).Ported from scala/scala#9713