1657372 - Warp: don't create ScriptCounts in Baseline

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, task, P2)

Description

[Jan de Mooij [:jandem]]

Warp currently doesn't use ScriptCounts but instead relies on the Baseline IC counters. That means we can make Baseline a bit faster by not allocating and maintaining ScriptCounts there.

Comment 1

[Nicolas B. Pierron [:nbp]]

Note that ScriptCounts are used by Branch Pruning, which is later empower Scalar Replacement to optimize for-of loops.

Using IC should be fine, but then the equivalent count should be added back such that branch pruning can remove the branches which are adding Phi causing Scalar Replacement incapabilities of making optimizations.

Comment 2

[Jan de Mooij [:jandem]]

(In reply to Nicolas B. Pierron [:nbp] from comment #1)

Note that ScriptCounts are used by Branch Pruning, which is later empower Scalar Replacement to optimize for-of loops.

Using IC should be fine, but then the equivalent count should be added back such that branch pruning can remove the branches which are adding Phi causing Scalar Replacement incapabilities of making optimizations.

Yeah, we already add bailouts for Baseline ICs with hit count 0 so if we teach branch pruning about those always-bailing-out blocks that would still work I expect.

Comment 3

[Nicolas B. Pierron [:nbp]]

Branch pruning uses some heuristics based on the generated instructions to decide to remove or not a branch with a zero hit-count.
Making all branches with 0 hit-count always bailout was a performance hit when I was tuning it.

Comment 4

[Jan de Mooij [:jandem]]

Attachment: Bug 1657372 - Don't create/increment ScriptCounts in Baseline when Warp is enabled. r?iain!

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/b92cbbf74d59
Don't create/increment ScriptCounts in Baseline when Warp is enabled. r=iain

Comment 6

[Atila Butkovits]

https://hg.mozilla.org/mozilla-central/rev/b92cbbf74d59