The discussion at scala/scala#2620
uncovered that the ICode-based optimizer's DCE doesn't eliminate a redundant conditional jump,
where both branches lead to one and the same instruction.

The example showing the above is test/files/jvm/bytecode-test-example/Foo_1.scala reproduced below:

class Foo_1 {
  def foo(x: AnyRef): Int = {
    val bool = x == null
    if (x != null)
      1
    else
      0
  }
}

With GenASM and -optimise we get the two conditional jumps that bytecode-test-example.check expects:

  public foo(Ljava/lang/Object;)I
   L0
    ALOAD 1
    IFNONNULL L1
   L1
    ALOAD 1
    IFNONNULL L2
   L3
    ICONST_0
    GOTO L4
   L2
    ICONST_1
   L4
    IRETURN
   L5
    LOCALVARIABLE this LFoo_1; L0 L5 0
    LOCALVARIABLE x Ljava/lang/Object; L0 L5 1
    MAXSTACK = 1
    MAXLOCALS = 2

including a useless

    ALOAD 1
    IFNONNULL L1
   L1

(useless because, whether the conditional jump is taken or not, L1 is the target anyway)