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Enable egraph-based optimization by default.#5587

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cfallin merged 4 commits intobytecodealliance:mainfrom
cfallin:enable-egraphs
Jan 19, 2023
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Enable egraph-based optimization by default.#5587
cfallin merged 4 commits intobytecodealliance:mainfrom
cfallin:enable-egraphs

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@cfallin cfallin commented Jan 18, 2023 •
edited by fitzgen
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This PR follows up on #5382 and #5391, which rebuilt the egraph-based optimization framework to be more performant, by enabling it by default.

Based on performance results in #5382 (my measurements on SpiderMonkey and bjorn3's independent confirmation with cg_clif), it seems that this is reasonable to enable. Now that we have been fuzzing compiler configurations with egraph opts (#5388) for 6 weeks, having fixed a few fuzzbugs that came up (#5409, #5420, #5438) and subsequently received no further reports from OSS-Fuzz, I believe it is stable enough to rely on.

This PR enables use_egraphs, and also normalizes its meaning: previously it forced optimization (it basically meant "turn on the egraph optimization machinery"), now it runs egraph opts if the opt level indicates (it means "use egraphs to optimize if we are going to optimize"). The conditionals in the top-level pass driver are a little subtle, but will get simpler once we can remove the non-egraph path (which we plan to do eventually!).

Fixes #5181

@github-actions github-actions bot added cranelift Issues related to the Cranelift code generator cranelift:area:machinst Issues related to instruction selection and the new MachInst backend. cranelift:meta Everything related to the meta-language. labels Jan 18, 2023
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cfallin commented Jan 18, 2023

Hmm, some issues caused by my reimplementation of #5534 (GVN + idempotency) for egraphs; switching this to draft for now.

@cfallin cfallin marked this pull request as draft January 18, 2023 03:08
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cfallin commented Jan 18, 2023

Pushed updates, but I'll factor out the idempotent-GVN updates for egraphs into a separate PR tomorrow then rebase this.

@cfallin
Turn on egraph-based optimization by default.
6f1f1f8 
Also update the pass-driving logic to run egraph optimization only when
optimization is enabled. Previously `use_egraphs` acted as an overall
enable-switch that drove egraph-based optimization, regardless of
`opt_level`.
@cfallin
Update egraph filetests to set opt_level explicitly and consistently.
a41aa46
@cfallin
Make some tests explicitly use non-egraphs path (egraphs are tested s…
37f02db 
…eparately).
@cfallin cfallin marked this pull request as ready for review January 19, 2023 19:59
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cfallin commented Jan 19, 2023

Rebased on the idempotency fix; should be ready to review now!

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alexcrichton commented Jan 19, 2023

I think one final location to touch doc-wise would be here too perhaps?

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cfallin commented Jan 19, 2023

I think one final location to touch doc-wise would be here too perhaps?

Ah, yes, updated!

@github-actions github-actions bot added wasmtime:api Related to the API of the `wasmtime` crate itself wasmtime:config Issues related to the configuration of Wasmtime labels Jan 19, 2023
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github-actions bot commented Jan 19, 2023

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github-actions bot commented Jan 19, 2023 •
edited by cfallin
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fitzgen
fitzgen approved these changes Jan 19, 2023
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🎉

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cfallin commented Jan 19, 2023

In an extremely amusing twist, adding the deprecation warning for the cranelift_use_egraphs config option makes our fuzz target build throw a warning (because it can configure Cranelift not to use egraphs), and this makes our no-warnings build fail. I'm going to just remove the deprecation warning for now to get this in and am happy to talk about ways to warn while still using it internally in a followup PR.

@cfallin cfallin merged commit 1faff8c into bytecodealliance:main Jan 19, 2023
@cfallin cfallin deleted the enable-egraphs branch January 19, 2023 23:46
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fitzgen commented Jan 20, 2023

In an extremely amusing twist, adding the deprecation warning for the cranelift_use_egraphs config option makes our fuzz target build throw a warning (because it can configure Cranelift not to use egraphs), and this makes our no-warnings build fail. I'm going to just remove the deprecation warning for now to get this in and am happy to talk about ways to warn while still using it internally in a followup PR.

You can #[allow(deprecated)] on the specific function that does the deprecated call in the fuzzing infra.

cfallin added a commit to cfallin/wasmtime that referenced this pull request Jan 20, 2023
@cfallin
Add deprecation notice to cranelift_use_egraphs option.
be99823 
After bytecodealliance#5587, this is on by default. We are retaining the traditional
(no-egraphs) path for now, selected by setting this option to `false`,
but we eventually plan to delete it assuming that we don't find serious
regressions or issues. This PR adds a deprecation notice to the option.
@cfallin cfallin mentioned this pull request Jan 20, 2023
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cfallin added a commit that referenced this pull request Jan 20, 2023
@cfallin
Add deprecation notice to cranelift_use_egraphs option. (#5610)
69cd0a6 
After #5587, this is on by default. We are retaining the traditional
(no-egraphs) path for now, selected by setting this option to `false`,
but we eventually plan to delete it assuming that we don't find serious
regressions or issues. This PR adds a deprecation notice to the option.
@bjorn3 bjorn3 mentioned this pull request Feb 6, 2023
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cranelift:area:machinst Issues related to instruction selection and the new MachInst backend. cranelift:meta Everything related to the meta-language. cranelift Issues related to the Cranelift code generator wasmtime:api Related to the API of the `wasmtime` crate itself wasmtime:config Issues related to the configuration of Wasmtime

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Cranelift: use egraphs by default

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