Suppose we want to generate code for a certain struct Box[T], with the constructor def mkBox[T: Manifest](t: Rep[T]); Rep[Box[T]]. Given the following code:
val someCond: Rep[Boolean] = //dynamic condition
if (someCond) mkBox(2)
else if (someCond) mkBox(7)
else mkBox(0)
If mixed in with the optimisation StructFatExpOptCommon, the generated code contains compile-time errors. Also, the generated code contains only one test for someCond: in the positive branch for that condition, both computations mkBox(2) and mkBox(7) are inlined. This is not desirable in general, and therefore should not be a default "optimisation". Consider a more real-life case:
val someCond: Rep[Boolean] = ...
val anOption: Rep[Option[Int]] = if (someCond) /* complex computation yielding Some */ else None
if (anOption.isDefined) anOption
else {
if (someCond) /* complex computation2 yielding Some */
else None
}
We only want the complex computation 2 to be inlined in the failure branch of the anOption. Using StructFatExpOptCommon we will arrive at a similar problem as above, effectively breaking the semantics of Option.
I am not fully confident in understanding StructExpFat and IfThenElseFat to propose a solution myself, unfortunately.
See https://gist.github.com/manojo/2e378e7128b13c84f29e for runnable test case.
Suppose we want to generate code for a certain struct
Box[T], with the constructordef mkBox[T: Manifest](t: Rep[T]); Rep[Box[T]]. Given the following code:If mixed in with the optimisation
StructFatExpOptCommon, the generated code contains compile-time errors. Also, the generated code contains only one test forsomeCond: in the positive branch for that condition, both computationsmkBox(2)andmkBox(7)are inlined. This is not desirable in general, and therefore should not be a default "optimisation". Consider a more real-life case:We only want the complex computation 2 to be inlined in the failure branch of the
anOption. UsingStructFatExpOptCommonwe will arrive at a similar problem as above, effectively breaking the semantics ofOption.I am not fully confident in understanding
StructExpFatandIfThenElseFatto propose a solution myself, unfortunately.