Decompile Java Streams to beautiful EO

[maxonfjvipon]

We have the next java code:

String[] strings = new String[10];
for (int i = 0; i < strings.length; i++) {
    strings[i] = String.valueOf(i);
}
int sum = Arrays.stream(strings)
    .filter(s -> !s.equals(""))
    .mapToInt(s -> Integer.parseInt(s))
    .sum();
System.out.println(sum);

After compilation, disassembling and decompiling it looks like this: decompiled.txt

In short - there are only opcodes, no decompilation is happening.

Ideally, the EO after decompilation should look something like this (I'm considering only working with Streams)

[] > factorial-application
  [] > new
    ... > @
  [] > main
    seq > @
      *
        ...
        java_util_Arrays.java_util_Arrays$stream
          java_lang_String[]-strings                         # I'm not sure if it's valid but we should mark that it's an array somehow
        .java_util_stream_Stream$filter
          [java_lang_String-s]
            seq > @
              *
                java_lang_String-s.java_lang_String$equals
                  ""
                .not
        .java_util_stream_Stream$mapToInt
          [java_lang_String-s]
            seq > @
              *
                java_lang_Integer.java_lang_Integer$parseInt
                  java_lang_String-s
        .java_util_stream_IntStream$sum > int_sum
        ...

Of course maybe it's not possible to get exactly such picture after decompilation because of bytecode restrictions. But the closer - the better

[volodya-lombrozo]

@maxonfjvipon Thank you for the explanation.

[volodya-lombrozo]

@maxonfjvipon Can we change the code you provided in the description to the following:

long start = System.currentTimeMillis();
String[] strings = IntStream.range(0, 10)
    .mapToObj(i -> String.valueOf(i))
    .toArray(String[]::new);
int sum = Arrays.stream(strings)
    .filter(s -> Boolean.valueOf(s.equals("")).equals(false))
    .mapToInt(s -> Integer.parseInt(s))
    .sum();

?
Otherwise I will need to implement decompilation of many opcodes including arrays related opcodes and, what is the most important, GOTO instruction, which is the most problematic instruction (we will need to preserve the control-flow.)

[maxonfjvipon]

@volodya-lombrozo sure, the creation of array of strings is not important step for us, we won't touch it in the optimizations

[0pdd]

@maxonfjvipon 2 puzzles #341, #342 are still not solved.

[0pdd]

@maxonfjvipon 7 puzzles #341, #342, #344, #345, #346, #347, #348 are still not solved.

[0pdd]

@maxonfjvipon 6 puzzles #341, #342, #344, #345, #346, #347 are still not solved; solved: #348.

[0pdd]

@maxonfjvipon 7 puzzles #341, #342, #344, #345, #346, #347, #361 are still not solved; solved: #348.

[0pdd]

@maxonfjvipon 8 puzzles #341, #342, #344, #345, #346, #347, #361, #363 are still not solved; solved: #348.

[0pdd]

@maxonfjvipon 8 puzzles #341, #342, #345, #346, #347, #361, #363, #366 are still not solved; solved: #344, #348.

[0pdd]

@maxonfjvipon 8 puzzles #341, #342, #345, #346, #361, #363, #366, #385 are still not solved; solved: #344, #347, #348.

[0pdd]

@maxonfjvipon 7 puzzles #341, #342, #345, #346, #361, #363, #366 are still not solved; solved: #344, #347, #348, #385.