1820605 - Add --enable-ic-frame-pointers

Status: RESOLVED FIXED

(Core :: JavaScript Engine: JIT, enhancement, P1)

Description

[Jeff Muizelaar [:jrmuizel]]

This means we'll attribute time spent in them to the caller's caller instead of the caller when looking at a JS only profile.

There's an example here: https://share.firefox.dev/3KXgZkz.

• a bunch of IC's have IC: TrialInline as their caller when it should likely be Baseline: filter or Baseline: map

jandem suggests that we could have a mode to add frame pointer epilogue/prologue code to baseline ICs

and iain says:
If it's just a mode for profiling, maybe we could make it 64-bit only and dedicate a separate register for the baseline frame pointer
So rbp would point to the stub frame, and (say) r14 would point to the baseline frame
It's hard to make it work on 32 bit x86 because we're already so short on registers

Comment 1

[BugBot [:suhaib / :marco/ :calixte]]

The severity field is not set for this bug.
:willyelm, could you have a look please?

For more information, please visit auto_nag documentation.

Comment 3

[Iain Ireland [:iain]]

Attachment: Bug 1820605: Remove BaselineCacheIRCompiler::tailCallVM r=jandem!

This interferes with frame pointers and is only being used for a single op. Given the overhead of a VM call, doing a tail call here doesn't seem worthwhile.

Comment 4

[Iain Ireland [:iain]]

Attachment: Bug 1820605: Add --enable-ic-frame-pointers r=jandem!

Depends on D173386

Comment 5

[Iain Ireland [:iain]]

Attachment: Bug 1820605: Optionally emit frame pointers in baseline ICs r=jandem!

Depends on D173387

Comment 6

[Iain Ireland [:iain]]

Attachment: Bug 1820605: Adjust encoding to match LLVM r=jandem!

These two encodings are equivalent, but the perf team's patches to perf are built around the one that LLVM uses. We can simplify things by changing our encoding.

Unfortunately we have some tests that hardcode specific encodings that have to be updated. Tested on try for both Linux and Windows.

Depends on D173388

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/32227614c7f1
Remove BaselineCacheIRCompiler::tailCallVM r=jandem
https://hg.mozilla.org/integration/autoland/rev/d5c403a4e05f
Add --enable-ic-frame-pointers r=jandem
https://hg.mozilla.org/integration/autoland/rev/4ae02092a204
Optionally emit frame pointers in baseline ICs r=jandem
https://hg.mozilla.org/integration/autoland/rev/6d97efe0c291
Adjust encoding to match LLVM r=jandem

Comment 8

[Sandor Molnar[:smolnar]]

https://hg.mozilla.org/mozilla-central/rev/32227614c7f1
https://hg.mozilla.org/mozilla-central/rev/d5c403a4e05f
https://hg.mozilla.org/mozilla-central/rev/4ae02092a204
https://hg.mozilla.org/mozilla-central/rev/6d97efe0c291