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exponential compiler performance with nested pattern matches under tailrec transform #8893

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scabug opened this issue Oct 7, 2014 · 3 comments
Closed

exponential compiler performance with nested pattern matches under tailrec transform #8893

scabug opened this issue Oct 7, 2014 · 3 comments
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@retronym
Milestone
2.11.5

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@scabug
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scabug commented Oct 7, 2014 

object Test {
    def a(): Option[String] = Some("a")
 
    def main(args: Array[String]) {
        a() match {
            case Some(b1) =>
        a() match {
            case Some(b2) =>
        a() match {
            case Some(b3) =>
        a() match {
            case Some(b4) =>
        a() match {
            case Some(b5) =>
        a() match {
            case Some(b6) =>
        a() match {
            case Some(b7) =>
        a() match {
            case Some(b8) =>
        a() match {
            case Some(b9) =>
        a() match {
            case Some(b10) =>
        a() match {
            case Some(b11) =>
        a() match {
            case Some(b12) =>
        a() match {
            case Some(b13) =>
        a() match {
            case Some(b14) =>
        a() match {
            case Some(b15) =>
        a() match {
            case Some(b16) =>
        a() match {
            case Some(b17) =>
        a() match {
            case Some(b18) =>
        a() match {
            case Some(b19) =>
        a() match {
            case Some(b20) =>
        a() match {
            case Some(b21) =>
        a() match {
            case Some(b22) =>
        a() match {
            case Some(b23) =>
        a() match {
            case Some(b24) =>
        a() match {
            case Some(b25) =>
        a() match {
            case Some(b26) =>
        a() match {
            case Some(b27) =>
        a() match {
            case Some(b28) =>
        a() match {
            case Some(b29) =>
        a() match {
            case Some(b30) =>
                println("yay")
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
            case None => None
        }
    }
}

See: https://twitter.com/dridus/status/519606670989590528
@scabug
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scabug commented Oct 7, 2014

Imported From: https://issues.scala-lang.org/browse/SI-8893?orig=1
Reporter: @retronym
Affected Versions: 2.10.4, 2.11.2

@scabug
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scabug commented Oct 7, 2014

@retronym said:
This fixes a constant factor along the way: https://github.com/retronym/scala/tree/topic/opt-tail-calls

But that's not the core problem.

@scabug
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scabug commented Oct 8, 2014

@retronym said:
I think I've spotted the problem. I've pushed a few more commits to that branch.

@scabug scabug closed this as completed Nov 4, 2014
@scabug scabug added this to the 2.11.5 milestone Apr 7, 2017
@SethTisue SethTisue mentioned this issue Sep 14, 2017
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@scala scala deleted a comment from scabug Nov 21, 2020
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