[cfallin]

Hi Fil -- thanks for the comment!

I think we may be playing in slightly different spaces: unlike a JS JIT, Cranelift doesn't have "super fancy escape/type analysis". We're really targeting the core optimizations (GVN, LICM, cprop, RLE, STLF, various algebraic rules) in a fast compile pass. The RLE+GVN interaction was pretty real in our case, as are interactions between the algebraic rewrites and GVN.

You'll note that my main point is that the single fixpoint loop for all of the core rewrites is what we wanted, and what the sea-of-nodes-with-CFG gets us; the egraph (multiple versions of one value) is kind of an aside. One could say: well sure but I could just do a single pass with that fixpoint loop without all the egraph stuff; and, yes, that's what our single rewrite pass is.

[titzer]

Thanks for writing the article, btw. I didn't have a chance to go through the whole thing yet.

Did you have a chance to study Graal's IR? It is a hybrid between sea of nodes and CFG; it can contain some "fixed" nodes that can be wired into basic blocks. It can also be relaxed and have nearly everything floating.

TurboFan's IR was very close to C2, but it had even more things that could float. E.g. a pure operation could be lowered to a subgraph with internal control. TurboFan's schedule could move entire floating control islands and attach them to the main CFG skeleton, or remove them entirely.

I'm working on a new IR and I'll be able to share more soon.

[cfallin]

Thanks! I haven't studied Graal's IR in detail, no. I'll add it to my reading list...

[pizlonator]

> I think we may be playing in slightly different spaces: unlike a JS JIT

My B3 compiler is a direct equivalent of Cranelift.

Sure, I've also written JS JITs. B3 was initially the backend of a JS JIT, but now does other things too. And I've done a lot of LLVM work.

Generally, it's unwise to assume you know what another person has or hasn't done. I'm not making that assumption about you. (I don't even know you, and that doesn't matter for the purposes of this discussion.)

> single fixpoint loop for all of the core rewrites is what we wanted, and what the sea-of-nodes-with-CFG gets us

It just feels so constraining. Eventually you'll want optimizations that can't be expressed with egraphs, and I'm not convinced that your approach conserves code or complexity even if you are sticking to egraphable optimizations.

[cfallin]

OK, cool. I was assuming "escape analysis and type inference" implied a JS JIT -- straight from your comment, no other assumptions intended. But you've got a lot of interesting experience here and thanks for your thoughts.

All the best!