$ javap -c -p demo.Target        (original, as javac produced it; fib and boom only)
  public static int fib(int);
    Code:
         0: iload_0
         1: iconst_2
         2: if_icmpge     9
         5: iload_0
         6: goto          22
         9: iload_0
        10: iconst_1
        11: isub
        12: invokestatic  #13                 // Method fib:(I)I
        15: iload_0
        16: iconst_2
        17: isub
        18: invokestatic  #13                 // Method fib:(I)I
        21: iadd
        22: ireturn

  public static void boom();
    Code:
         0: new           #31                 // class java/lang/IllegalStateException
         3: dup
         4: ldc           #33                 // String boom
         6: invokespecial #35                 // Method java/lang/IllegalStateException."<init>":(Ljava/lang/String;)V
         9: athrow

$ javap -c -p demo.Target        (naive transform: records on normal return only)
  public static int fib(int);
    Code:
         0: invokestatic  #74                 // Method java/lang/System.nanoTime:()J
         3: lstore_1
         4: iload_0
         5: iconst_2
         6: if_icmpge     13
         9: iload_0
        10: goto          26
        13: iload_0
        14: iconst_1
        15: isub
        16: invokestatic  #13                 // Method fib:(I)I
        19: iload_0
        20: iconst_2
        21: isub
        22: invokestatic  #13                 // Method fib:(I)I
        25: iadd
        26: ldc           #76                 // String Target.fib
        28: invokestatic  #74                 // Method java/lang/System.nanoTime:()J
        31: lload_1
        32: lsub
        33: invokestatic  #82                 // Method demo/Timings.record:(Ljava/lang/String;J)V
        36: ireturn

  public static void boom();
    Code:
         0: invokestatic  #74                 // Method java/lang/System.nanoTime:()J
         3: lstore_0
         4: new           #31                 // class java/lang/IllegalStateException
         7: dup
         8: ldc           #33                 // String boom
        10: invokespecial #35                 // Method java/lang/IllegalStateException."<init>":(Ljava/lang/String;)V
        13: athrow

$ javap -c -p demo.Target        (full transform: plus a catch-all handler)
  public static int fib(int);
    Code:
         0: invokestatic  #74                 // Method java/lang/System.nanoTime:()J
         3: lstore_1
         4: iload_0
         5: iconst_2
         6: if_icmpge     13
         9: iload_0
        10: goto          26
        13: iload_0
        14: iconst_1
        15: isub
        16: invokestatic  #13                 // Method fib:(I)I
        19: iload_0
        20: iconst_2
        21: isub
        22: invokestatic  #13                 // Method fib:(I)I
        25: iadd
        26: ldc           #76                 // String Target.fib
        28: invokestatic  #74                 // Method java/lang/System.nanoTime:()J
        31: lload_1
        32: lsub
        33: invokestatic  #82                 // Method demo/Timings.record:(Ljava/lang/String;J)V
        36: ireturn
        37: astore_3
        38: ldc           #76                 // String Target.fib
        40: invokestatic  #74                 // Method java/lang/System.nanoTime:()J
        43: lload_1
        44: lsub
        45: invokestatic  #82                 // Method demo/Timings.record:(Ljava/lang/String;J)V
        48: aload_3
        49: athrow
      Exception table:
         from    to  target type
             4    37    37   any

  public static void boom();
    Code:
         0: invokestatic  #74                 // Method java/lang/System.nanoTime:()J
         3: lstore_0
         4: new           #31                 // class java/lang/IllegalStateException
         7: dup
         8: ldc           #33                 // String boom
        10: invokespecial #35                 // Method java/lang/IllegalStateException."<init>":(Ljava/lang/String;)V
        13: athrow
        14: astore_2
        15: ldc           #90                 // String Target.boom
        17: invokestatic  #74                 // Method java/lang/System.nanoTime:()J
        20: lload_0
        21: lsub
        22: invokestatic  #82                 // Method demo/Timings.record:(Ljava/lang/String;J)V
        25: aload_2
        26: athrow
      Exception table:
         from    to  target type
             4    14    14   any