Stream: git-wasmtime

Topic: wasmtime / PR #4710 Cranelift: Use bump allocation in `re...

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 18:52):

fitzgen requested cfallin for a review on PR #4710.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 18:52):

fitzgen opened PR #4710 from bump-alloc-in-remove-constant-phis to main:

This makes compilation 2-6% faster for Sightglass's bz2 benchmark:

compilation :: cycles :: benchmarks/bz2/benchmark.wasm

  Δ = 7290648.36 ± 4245152.07 (confidence = 99%)

  bump.so is 1.02x to 1.06x faster than main.so!

  [166388177 183238542.98 214732518] bump.so
  [172836648 190529191.34 217514271] main.so

compilation :: cycles :: benchmarks/pulldown-cmark/benchmark.wasm

  No difference in performance.

  [182220055 225793551.12 277857575] bump.so
  [193212613 227784078.61 277175335] main.so

compilation :: cycles :: benchmarks/spidermonkey/benchmark.wasm

  No difference in performance.

  [3848442474 4295214144.37 4665127241] bump.so
  [3969505457 4262415290.10 4563869974] main.so

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 19:02):

cfallin created PR review comment:

While we're here, is blocks_reverse_postorder.len() the only remaining reason we need to collect RPO into a Vec above? Or can we iterate on the iterator chain (postorder ... .rev()) below, and get the length from that somehow too?

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 19:02):

cfallin submitted PR review.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 19:02):

cfallin submitted PR review.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 19:02):

cfallin created PR review comment:

Does summaries still need to be a hashmap? It seems to me like it should be dense. If we can have a default state (either Option<BlockSummary<'a>> or a zero-alloc and cloneable empty BlockSummary) we could use a SecondaryMap here I think.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 19:31):

bjorn3 created PR review comment:

You can get the length of an iterator using .count(). This avoids the intermediate allocation of a Vec.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 19:31):

bjorn3 submitted PR review.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 19:33):

bjorn3 submitted PR review.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 19:33):

bjorn3 created PR review comment:

However we do iterate over it below: for &&b in &blocks_reverse_postorder {.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 19:42):

cfallin submitted PR review.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 19:42):

cfallin created PR review comment:

Right, the idea is that we could iterate over domtree.cfg_postorder().iter().rev() (with that expression directly in the for). And I see cfg_postorder returns a slice so we can do domtree.cfg_postorder().len() here I think.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 20:12):

fitzgen submitted PR review.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 20:12):

fitzgen created PR review comment:

About 30-35% of blocks don't get a block summary (no parameters themselves and no successors have params either) so it isn't a clear win since the hash map miiiiight end up using less space. I'll do a quick test and see if there is anything I can measure.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 20:12):

fitzgen created PR review comment:

Did this and wasn't able to measure any difference in perf, but its a nice change (good eye!) so I'll push it up soon.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 20:12):

fitzgen submitted PR review.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 20:16):

cfallin submitted PR review.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 20:16):

cfallin created PR review comment:

Ah OK, in that case it seems totally fine to stick with the hashmap, unless we're surprised by your results!

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 20:38):

fitzgen updated PR #4710 from bump-alloc-in-remove-constant-phis to main.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 20:40):

fitzgen submitted PR review.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 20:40):

fitzgen created PR review comment:

I didn't get any measurable perf benefits from switching to a SecondaryMap but it did actually clean up a bit of unwraps and such, so I do think I'll keep it.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 20:40):

fitzgen has enabled auto merge for PR #4710.

view this post on Zulip Wasmtime GitHub notifications bot (Aug 15 2022 at 21:36):

fitzgen merged PR #4710.

Last updated: Dec 13 2025 at 19:03 UTC