wasmtime/meetings/cranelift/2021/cranelift-10-18.md

October 18 project call

See the instructions for details on how to attend

Agenda

1. Opening, welcome and roll call
   1. Note: meeting notes linked in the invite.
   2. Please help add your name to the meeting notes.
   3. Please help take notes.
   4. Thanks!
2. Announcements
   1. Sumbit a PR to add your announcement here
3. Other agenda items
   1. (fitzgen) update on ISLE integration
   2. Sumbit a PR to add your item here

Notes

Attendees

• cfallin
• fitzgen
• acrichto
• uweigand
• bjorn3
• sparker
• jlbirch
• bbouvier

Notes

ISLE

• fitzgen: first few rules working and integrated into Cranelift with tests passing, (few == 3, iconst, bconst, and catch-all for add). Glue isn't too bad and now plan to work on complicated lowerings next. If there are ideas of things to prove out the DSL let me know. Next is add with sinking loads, add with an immediate, popcnt lowering, compare-and-branch, etc. Hope to have final yay/nay in 2 weeks. Personally have enjoyed ISLE so far and it was super-easy to add case to 0-immediates are xor reg/reg. Didn't involve fitting into match tree and was nice to write as a standalone rule.
• cfallin: gist?
• fitzgen: not PR ready but sure!
• cfallin: this is definitely something I would have wanted last year, but take that with a grain of salt. Need to evaluate whether it's worth the complexity. Any questions/comments?
• cfallin: no vote today at all, just a progress update, but after two weeks hopefully will find consensus one way or another to move forward. Hope to make a decision soon though so this doesn't continue indefinitely.
• fitzgen: plan to have enough by next mtg for sure, yeah.
• jlbirch: which aspect is this supplementing or replacing? [the files posted]
• fitzgen: the handwritten match statements in lowering code going from clif to machinst.
• jlbirch: these looks like comments for types and not instructions?
• cfallin: oh there's inst.isle and lower.isle

... discussion of https://github.com/fitzgen/wasmtime/blob/isle/cranelift/codegen/src/isa/x64/lower.isle ...

... discussion of https://github.com/fitzgen/wasmtime/blob/isle/cranelift/codegen/src/isa/x64/inst.isle ...

• sparker: looks quite good for addressing modes on memory operations
• fitzgen: next goal for me!
• bjorn3: looks like a lot of new dependencies?
• fitzgen: uses miette - current branch unconditionally rebuilds isle crate, but shouldn't have to rebuild any of this unless you're changing various data types. Most don't touch this, so dependencies should only matter if you're actively hacking on these areas.
• cfallin: eventually we may not have the meta step or might check in more of the code. Would improve build times by a lot, but this is a separate discussion with different pros/cons. If build time is a concern there are avenues to take.

Status

• cfallin: not much, working on non-cranelift things. RA2 progressing a bit, jseward planning on finishing review for regalloc.rs adapter. Should be able to release to crates.io after that and license bits sorted.
• fitzgen: no other updates than from above.
• bbouvier: no update
• acrichto: no update
• jlbirch: starting to look at some fuzz bugs
• uweigand: working on atomics, everything is cas loops, tedious. Seems like clif supports a lot of atomic ops which are easy on x86 as a single instruction but not as easy on other platforms. Should we remove bits from clif ir?
• cfallin: github issues to remove things and can discuss there?
• uweigand: building wasi binaries from Rust needs a linker which isn't available on s390x.
• sparker: looking at flexible vectors, gonna try to put into cranelift somehow. Hoping to use ISLE to convert between flexible vectors and neon.
• cfallin: new clif instructions?
• sparker: using existing instructions but getting size of vector into system and have backends never see it later ideally.
• cfallin: feel free to post an issue and we can discuss there too
• jlbirch: based on flexible vector proposal?
• sparker: yes
• jlbirch: I would be interested! Would be great to have shared infrastructure.
• sparker: hoping to separate into 3 tiers, first being current simd. Want to have shared infrastructure to map to existing targets first.
• bjorn3: cleaning up after old x86 backend removal
• cfallin: great to see so much deleted!