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optimizer changes behavior of IDIV, LDIV, IREM, LREM bytecode instructions when the result is dropped #7607

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scabug opened this issue Jun 25, 2013 · 3 comments

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@scabug
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commented Jun 25, 2013

When compiled with -optimize the following program goes wrong:

object Test {

  def main(args: Array[String]) {
    (1 / 0)
  }

}

It swallows the ArithmeticException that the JVMS specifies should be thrown. The bytecode emitted is:

  // access flags 0x1
  public main([Ljava/lang/String;)V
   L0
    LINENUMBER 5 L0
    RETURN
   L1
    LOCALVARIABLE this LTest$; L0 L1 0
    LOCALVARIABLE args [Ljava/lang/String; L0 L1 1
    MAXSTACK = 0
    MAXLOCALS = 2

The problem goes away when the body of main is changed to use the result of (1 / 0) (as opposed to discarding the result as above). For example -optimize emits correct bytecode for:

object Test {

  def main(args: Array[String]) {
    println(1 / 0)
  }

}

Originally reported in https://groups.google.com/forum/#!searchin/akka-user/optimize/akka-user/r0Teq08f-YU/2Dfl1yQKbL0J

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commented Jun 25, 2013

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commented Jun 26, 2013

@magarciaEPFL said:
I've added tests for this bug in the branch for the new optimizer,
magarciaEPFL/scala@d525b6c

(the new optimizer isn't prone to this bug)

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commented Jun 6, 2014

@lrytz said:
fixed in scala/scala#3765, duplicate of #8601

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