Stream: cranelift

Topic: ✔ Matching dynamically sized constants using ISLE

view this post on Zulip Chris Fallin (May 06 2025 at 00:19):

There isn't a single "correct" way, but this is an ideal case for an "external extractor", where you define your own logic as needed. Cranelift's use of ISLE has a bunch of examples of those -- grep for (extern extractor ...) -- including for some cases with constants predicated on types, etc. Or, if you need an input (say, width above), then a fallible constructor with an if-let is another option:

(decl is_all_ones_of_width (u64 u8) Unit)
(extern constructor is_all_ones_of_width is_all_ones_of_width)

(rule (lower (Ast.Or (Ast.Constant value width) a))
  (if-let _ (is_all_ones_of_width value width))
  ...)

then define is_all_ones_of_width in your environment trait to return Some(()) if true or None if not.

view this post on Zulip Colton (May 06 2025 at 00:25):

This is exactly what I was looking for. Thanks Chris!

view this post on Zulip Notification Bot (May 06 2025 at 00:28):

Colton has marked this topic as resolved.

Last updated: Dec 06 2025 at 07:03 UTC