Compiler: cache cleanup transformer

[asterite]

Otherwise on every finished hook we might potentially be cleaning up big chunks
of the program over and over agin.

Consider this program:

{% for i in 0..3000 %}
  puts "Hello"
{% end %}

On my machine it takes about a second to compile.

Now this program:

{% for i in 0..3000 %}
  macro finished
    puts "Hello"
  end
{% end %}

It takes 8.5 seconds to compile! 😱

The reason is that we call cleanup on every finished hook, and that ends up creating a new CleanupTransformer. Every transformer will cleanup calls and their respective target methods (target_defs), and keep a cache of which have been transformed (many calls might end up hitting the same method, of course.) However, because we create a new CleanupTransformer on every finished hook, these methods are "cleaned up" over and over again (this could spawn a big chunk of the program, because it goes into those methods, calls in those methods, and target methods of those calls, etc.)

I noticed this because the interpreter uses cleanup a lot more, and it was taking like 1 minute to create bytecode for the compiler's program, while it took about 20 seconds to generate LLVM code, which was very unreasonable.

I know Lucky and other programs use macro finished a lot so this might improve compilation times a bit, but I don't expect a huge difference (in this sample program I have 3000 macro finished hooks, maybe a regular program have a dozen of them, I don't know)

[asterite]

I forgot to mention: with this PR, that snippet with those macro finished takes the same time now: about a second to compile, instead of 8.5 seconds.

[beta-ziliani]

🚀

[sdogruyol]

More performance 😋 Thanks @asterite 🙏

[elorest]

I think this may help a lot for me. We have a project which takes about 2 minutes to compile on my mac but about 40 minutes to compile to arm. We do use finish on a class which is inherited from a few hundred times.

[elorest]

So without --release flag… removing macro finish cut my compile time from 1:48.22 to 1:16.82.