bsloane1650 commented on a change in pull request #316: Assortment of changes
to improve performance
URL: https://github.com/apache/incubator-daffodil/pull/316#discussion_r370361355
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File path:
daffodil-runtime1/src/main/scala/org/apache/daffodil/processors/Evaluatable.scala
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@@ -285,7 +285,17 @@ abstract class Evaluatable[+T <: AnyRef](protected val
ci: DPathCompileInfo, qNa
/**
* Preferred for use in the runtime.
*/
- @inline final def maybeConstant = constValue_.asInstanceOf[Maybe[T]]
+ @inline final def maybeConstant = {
Review comment:
In theory, this should just be maybeConstant = constValue_. All we are
trying to do here is a cast from T <: AnyRef : Maybe[AnyRef] -> Maybe[T], which
is a complete no-op at runtime.
This feels like we should be using DataValuePrimitiveNullable instead of
either Maybe type. However, I believe I decided that doing so would involve
refactoring all of out expression classes that used T <: AnyRef, which we
probably don't want to do.
We can however use the same trick in the Maybe class that I used in the
DataValue class to do this conversion with 0 runtime overhead.
Essentially, as part of the Maybe class, define an inline function along the
lines of: unsafeCast[T]:Maybe[T] = (Maybe(this.get))
This worked in the case of DataValues because T was purely a phantom type.
In the case of Maybe, I think it should be possible to do something similar
because of type erasure.
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